IV. COUNTRY REPORTS

1. Afghanistan
2. Cyprus
3. Iran
4. Iraq
5. Jordan
6. Lebanon
7. Libyan Arab Republic
8. Pakistan
9. Qatar
10. Saudi Arabia
11. Somali Democratic Republic
12. Sudan

1. Afghanistan

1.1. Introduction

Afghanistan is an interesting country, popularly called the land of mountains or the Switzerland of Asia. It lies between 29 and 38° north and the elevation varies from high mountains (up to 7 620 m) to arid desert plains, with the most general height being 1 200 m above sea level. The climate is cold in winter, hot and dry in the summer. Rainfall is scanty, nowhere more than 381 mm annually with much of the precipitation as winter snow and spring rains.

The total area is 653 000 km² with an estimated population of 17 million, 85 percent of which is classified as rural and 15 percent as urban. It is estimated that about 14 million hectares of land is cultivable, with 2.3 million hectares under wheat irrigation.

Afghanistan's economy is dependent on production and export of crops and livestock products. Principal exports are dried and fresh fruits, nuts Karakul pelts, raw cotton, wool, carpets and rugs.

1.2. Soils of Afghanistan

A detailed soil survey of the country is yet to be completed, however a generalized map of the soils of Afghanistan is presented in Fig. 1.

A study of the Genesis of Afghanistan soils indicate that these are developed predominantly from the influence of climate. Since moisture is low, physical weathering is more pronounced than chemical and soil formation has proceeded rather slowly. Most of the products of weathering are retained within the soil itself.

Calcification is the most dominant soil forming process in dry conditions. In areas of low rainfall there is a tendency to evaporation from the surface and replacement from the water table below. The groundwater which is drawn up often contains large amounts of dissolved calcium bicarbonate and on evaporation the calcium carbonate is deposited within the soil-body resulting in an accumulation of this substance. Leaching of the soluble materials from the surface downwards is minimal because of the absence of percolating water.

Horizons and features of three representative soil profiles are presented in Fig. 2. An examination of these shows that:

a) The profile of Kabul silt loam has a marked textural and structural B horizon. In the sub-soil there is an abundance of irregular calcareous nodules, less than 8 cm in diameter. A few calcite tubes, calcareous tubules and columnar Krotovinas, all about 2.5 cm in diameter were observed. A horizontal calcite plate 1 mm thick lay at a depth of 150 cm and was continuous except for the points at which it was pierced by calcite tubes.

b) The second profile at Nadi Ali, had a gravelly tertural II B horizon under a massive vesicular Ap, Pinkish white calcium carbonate nodules (7,5 yr 6/4 D) less than 1 cm in diameter are abundant in the II B 21. At a depth of 175 cm there is a petrocalcic horizon of unknown thickness.

c) The third profile is undisturbed Boast sandy loam, has a discontinuous desert pavement (Ar), and has the most cemented horizon. The II CICS between 58 and 82 cm contains more than 50% by volume of calcium carbonate and associated gypsum and salts. The weakly cemented III C6CS horizon does not effervesce with acid.

Figure -2- Horizonation and Features of Representative Soil Profile of Afghanistan

The soils of Afghanistan are alkaline in reaction. Most of the samples studied have a pH much higher than 7.0. It is estimated that nearly 50% of the soils of Afghanistan have a pH between 8 and 8.5, about 35% between 8.5 and 9.0 and about 10% between 9 and 9.5. It is also known that soils with a pH of 8.0 to 8.5 are generally rich in alkaline earth carbonates, except for the soils of Panjshir Ghorband Valley. All the soils studied so far have a calcium carbonate content of 10% or more; soils of the Ghazani area have in general 10 to 12% calcium carbonate, Kunduz soils show 10 to 15% Kabul and Katawaz 10 to 20%, Hari-Rud 15 to 20%, and Farah, Logar and Adras Kand areas show 20 to 25% calcium cargonate in the surface samples. Occasionally in some areas CaCO₃, content is more than 40%.

1.3. Response of Wheat, Corn and Sugarbeet grown on the Calcareous Soils of Afghanistan to Fertilization

The excess of calcium carbonate poses serious problems in plant nutrition, mainly because it influences the pH of soil and thus renders micro-nutrients unavailable to plants as well as the unavailability of phosphorus in calcareous soils.

During the FAO Project on soil fertility and fertilizer use, some simple fertilizer experiments were conducted in different provinces of Afghanistan (for details please refer to UNDP/FAO/Report No. TA 30/6).

The average mean yield of wheat as affected by fertilizer treatment is presented in Table 1. Corresponding yields for corn are given in Table 2 and for sugarbeet in Table 3. The average CaCO₃, is given for each province.

From these data it seems that, inspite of high CaCO₃ content, the response to application of N + P is uniformly high and statistically significant. However, more detailed experimentation is needed to draw valid conclusions about management of calcareous soils in Afghanistan.

REFERENCES

Salem, M.Z. and Hole, E.D. 1969, Soil Geography and Factors of Soil Formation in Afghanistan. Soil Science, Vol. 107, No.4.

UNDP/FAO T.A. Report No. 3016 - 1971, Soil fertility and fertilizer use in Afghanistan (based on work of Dr. Tamboli, FAO expert). FAO, Rome.

Table 1. Mean average yield of wheat as affected by fertilizer treatments (kg/ha)

Province	Lagman		Nangarhar		Kabul		Logar		Maidan
Treatment No.	1969 - 70		1969 - 70		1969 - 70		1969 - 70		1969 - 70
1.	1 167	1 719	1 087	1 835	1 655	2 012	1 378	1 691	1 089	1 628
2.	1 542	2 167	1 406	2 251	1 814	2 647	1 555	2 363	1 290	2 346
3.	1 800	2 339	1 710	3 205	2 031	2 768	1 727	2 482	1 441	2 408
4.	1 427	1 953	1 310	2 288	1 985	2 383	1 637	2 087	1 367	1 658
5.	1 540	1 806	1 398	3 094	2 148	2 379	1 721	1 982	1 469	1 991
6.	2 281	3 710	2 265	3 864	3 133	3 925	2 539	3 157	2 776	3 327
7.	2 052	3 273	1 954	2 704	2 590	3 327	2 024	2 787	2 418	2 671
8.	2 292	3 039	2 340	2 871	2 596	3 478	2 168	2 790	2 428	2 913
9.	3 197	4 522	3 304	4 382	5 420	4 781	4 769	3 909	4 900	3 980
10.	1 704	1 826	1 321	2 038	2 134	2 211	1 684	1 860	1 407	1 946
11.	2 354	3 814	2 319	4 026	3 158	4 018	2 591	3 322	2 487	3 379
12.	3 310	4 650	3 376	4 533	5 573	4 764	4 618	3 885	4 690	4 056
CaCO3 %	3.0		10.0		. 14		18		11

Province	Parwan		Kapisa		Ghazni	Baghlan	Kunar
Treatment No.	1969 - 70		1969 - 70		1970	1970	1970
1.	1 296	1 681	1 296	1 748	1 461	1 946	1 641
2.	1 574	2 202	1 574	2 400	1 997	2 350	2 485
3.	1 738	2 603	1 738	2 733	2 311	2 579	2 700
4.	1 570	1 963	1 570	2 156	1 894	2 225	1 833
5.	1 589	2 411	1 589	2 620	1 889	2 203	2 770
6.	2 499	3 643	2 499	3 615	2 781	3 791	3 876
7.	2 335	3 013	2 335	2 845	2 605	3 159	2 915
8.	2 332	3 127	2 332	3 136	2 233	3 000	3 491
9.	4 180	4 418	4 180	4 015	3 444	4 302	4 208
10.	2 029	1 943	2 029	2 551	2 066	2 280	2 100
11.	2 711	3 777	2 711	4 281	2 761	3 289	3 610
12.	3 968	4 486	3 968	4 603	3 411	4 333	4 441
CaCO3 %	3				15	17	3

Treatment
	N	-	P2O5	-	K2O
1.	0	-	0	-	0
2.	75	-	0	-	0
3.	150	-	0	-	0
4.	0	-	75	-	0
5.	0	-	150	-	0
6.	75	-	75	-	0
7.	75	-	150	-	0
8.	150	-	75	-	0
9.	150	-	150	-	0
10.	0	-	75	-	100
11.	75	-	75	-	100
12.	150	-	150	-	100

Table 2. Mean average yield of corn as affected by fertilizer treatment

Treatment	Fertilizers - kg/ha			Yield in kg/ha
No.	N	P2O5	K2O	Paktya1/	Logar2/
1.	0	0	0	1 967	1 905
2.	75	0	0	2 351	2 457
3.	150	0	0	3 859	3 900
4.	0	75	0	2 372	2 495
5.	0	150	0	2 499	2 676
6.	75	75	0	5 906	6 011
7.	75	150	0	3 973	4 035
8.	150	75	0	3 929	4 152
9.	150	150	0	6 844	6 995
10.	0	75	50	2 523	6 680
11.	75	75	50	5 988	6 087
12.	150	150	50	6 950	7 081

^1/ Soils with 15% CaCO₃
^2/ Soils with 18% CaCO₃

^1/ Soils with 17% CaCO₃

2. Cyprus

2.1. Physical. Morphological and Geological features of Cyprus

Cyprus is an island in the eastern Mediterranean sea lying between 34°33' to 35°41' North and between 32°20' to 34°35' East, 70 km from southern Turkey, 100 km west of Syria and 370 km north of Egypt.

Its maximum length is 225 km east to west and its greatest width is 96 km north to south. It covers an area of 9 250 km² of which some 47 percent is arable and about 25 percent under forests. Out of a total population of 640 000, 35 percent of the economically active population is presently engaged in agriculture.

The island is transversed by two mountain ranges, the high Troodos massif in the southwest with the highest peak, Olympus, at 2 000 m and the long narrow Kyrenia range rising to 900 m and bordering the northern coast. Between the two mountain systems lies the central plain, and along their seaward margins a more or less narrow coastal strip.

The Troodos massif consists of igneous rocks, while the Kyrenia range is hard crystalline limestone. Over almost half the central plain there are middle miocene and post middle miocene calcareous marine sediments, such as marls and limestone outcrops. The rest of the plain is covered by pleistocene calcareous of non-calcareous deposits, and by recent calcareous alluvium in some low lying areas. The coastal strips consist of upper miocene to upper pliocene limestones and marls in places, while the rest is covered by pleistocene calcareous or non-calcareous deposits and by recent calcareous alluvium.

Middle miocene soft bedded limestones and chalks stretch from east to west of the southern part of the island over a distance of approximately 145 km. This stretch of land, frequently dissected by deep, narrow valleys, cut down by young rivers flowing to the sea, constitutes the southern flanks of the Troodos massif, and due to favourable climatic conditions, extensive vine plantations have been established on these extremely calcareous soils.

2.2. Climate

The climate of Cyprus has the characteristic features of the arid Mediterranean basin, with a cool wet winter followed by a hot and practically rainless summer. Cyprus, at the northeast corner of the Mediterranean sea and 3 200 km from the Atlantic ocean, is surrounded by much larger land masses and furthermore, these lands around Cyprus are of a dominant arid and semi-arid character. On account of its position Cyprus is influenced by modified continental air masses. Many travelling lows, however, are diverted at the southern corner of Turkey and leave Cyprus unaffected. In addition the major winter front, originating from the Icelandic low and covering most of Europe, seems to end in southern Turkey.

2.2.1 Precipitation and its distribution

Most of the rain falls between November and April, 50 percent of it in December and January. The average annual precipitation ranges according to elevation from 320 mm in the central plain and 500 mm in coastal areas to 800 mm at highest elevations. However, in dry years the central plains receive less than 200 mm of annual rainfall.

Winter rain is the most important element to the vegetative environment of the island as, in addition to the replenishment of the groundwater resources, it provides for the evapotranspiration requirements of dryland farming (cereals, carobs, olives and vines). Its distribution even in the rainy months is uneven and low precipitation in March-April affects adversely the performance of rainfed cereals during their critical physiological stage.

2.2.2 Temperature

The monthly mean maximum temperature in the central plain ranges from 15°C in January to about 35°C in July and August. The coolest areas are the most elevated, Olympus (2 000 m) having a mean maximum of 26°C in August.

The mean minimum temperature ranges from about 5°C to 20°C and frost, although infrequent, may happen unexpectedly.

2.2.3 Relative humidity

The average monthly relative humidity ranges from 40 to 80 percent in the inland plain with lowest in the summer, 50 to 85 percent in the coastal areas and 40 percent in the summer and 80 percent in January-February on the Troodos massif.

2.2.4 Evaporation and evapotranspiration

Evaporation (E pan) in the central plain and measured by USWB class 'A' pan reaches an annual total of 1 750 mm. In coastal areas annual cumulative pan evaporation is somewhat lower at around 1 500 mm. Evapotranspiration (ETp) calculated by Penman formula is about 70 percent of pan evaporation. Typical data obtained for Nicosia were as follows:

J	F	M	A	M	J	J	A	S	0	N	D	Year
37	45	85	143	206	269	285	260	196	119	61	39	1 745 mm E pan
31	41	68	108	142	181	192	184	130	87	46	28	1 238 mm ETp

2.3. Soils

From the pedogenic point of view the soils of Cyprus bear the strong impact of the aridity of the climate and the diversity of the topography, both of which seem to have acted dominantly on the parent material and to have subjugated to secondary importance the contribution of vegetation in the processes of soil formation.

The shallowness of the soil profile and the almost complete lack of well-defined diagnostic horizons indicate that the large soil moisture deficit created from low precipitation and high evapotranspiration has arrested the speed of the soil forming processes known to be active under more humid climates.

Essentially then the soils of Cyprus are typified by this Mediterranean character resulting in low organic matter, high calcium carbonate content in surface horizons, high pH, low mineral nitrogen, low phosphorus and high total and exchangeable potassium.

2.3.1 Soil surveys

Soil survey forms an important part of the activities of the Department of Agriculture under the Ministry of Agriculture and Natural Resources. A systematic soil survey designed to cover the whole island has been in progress since 1956. Until the present, over 300 000 hectares or 70 percent of the cultivated area of the island have been surveyed and covered by detailed soil maps.

In some watersheds land suitability surveys were carried out concurrently with detailed soil surveys in conjunction with proposed development projects, to propose the best land use based on soil properties, climate and availability of irrigation water.

2.3.2 Soil classification

Until 1970 the agricultural soils of Cyprus were classified as:

Rendzinas -	light-coloured calcareous soils formed on soft highly calcareous rock or calcareous colluvium and alluvium;
Terra Rossa -	red-coloured fine-textured soils on hard calcareous
	crust overlying soft mass of limestone;
Alluvial soils-	formed on recent water-borne deposits extensive in the central plain
Carbonate raw - soils	formed on calcareous parent material;
Silicate raw -soils	formed on igneous materials;
Brown earths -	formed on basic volcanic and plutonic rocks;
Bed soils (rotlehm)	formed on igneous conglomerates.

In 1970 the new system of soil classification introduced by the European Commission on Agriculture of the U.N. was adopted and a general soil map of the island at a scale 1:200 000 has been prepared. Under this system the soils of Cyprus fall into nine orders, namely, Lithosols, Solonchaks, Vertisols, Xerosols, Solonetz, Cambisols, Rendzinas, Luvisols and Rhegosol.

The distribution of most of the Cyprus soils classified according to the above-mentioned orders and sub-orders is approximately as follows:

 

Order	Sub-order		Area, km2
Lithosol	calcaric		2 280
	eutric (igneous, lavas)		137
Solonetz	orthic
		saline and alkaline	283
Solonchaks	gleic
Xerosols	haplic	Kythrea formations
			770
Lithosols	calcaric	marls and sandstones
Vertisols	chromic (mamonia)		103

 

Order	Sub-order				Area km2
Vertisol	calcaro pellic
				central plain alluvials of low EC	269
Lithosols	calcaric
Cambisols	vertic				291
Cambisols	calcaro chromic (reddish brown)				1 142
Cambisols	eutric (igneous)				1 434
Rendzinas	orthic
		limestones			832
Lithosol	calcaric
Rhegosols	calcaric				269
Rhegosols	calcaric
		alluvial			229
Vertisols	verlic
Luvisols	rhodo chromic				317
	rhodo calcic

2.3.3 Calcareous soils and their distribution

Soils in Cyprus are calcareous with the exception of those developed on hard igneous rocks of the Troodos massif, on non-calcareous swelling clays outcropping to the southwest and on some pleistocene non-calcareous deposits of the central plain and the coastal strip which could be termed as non-calcareous. It is worth noting here that the vast majority of soils in Cyprus contain free calcium carbonate, they have a predominantly Ca-saturated clay and their pH determined in a 1:5 soil to water suspension is above 7.5.

Soils referred to as "calcareous" vary in lime content from those having a small concentration somewhere in the profile to those containing an appreciable amount of lime throughout the profile. The term "calcareous soils" is used here to designate soils in which the lime content is sufficiently high to affect adversely the nutrition of crops, reduce productivity of the soil and narrow the choice of crops that could be grown on such soils.

The following calcium carbonate classes if adopted could be used for separating calcareous soils associated with properties that may adversely affect plant nutrition, from the rest of calcareous soils:

	CaCO3 Content
Calcium Carbonate Classes	%
(1) Non or almost non-calcareous soils	<5
(2) Slightly calcareous soils	5-15
(3) Moderately calcareous soils	15-35
(4) Calcareous soils	35-55
(5) Very calcareous soils	55-75
(6) Extremely calcareous soils	>75

The distribution of Cyprus soils according to the above system of classification and the proposed calcium carbonate classes may be summarized as follows:

soils developed on the Troodos massif are practically non-calcareous Eutric Cambisols and Eutric Rhegosols;

soils developed on the Kyrenia range are on the majority calcareous and have been classified as Calcaric Lithosols and Mollic Rendzinas;

over the central plain the soils occurring extensively are classified as Calcaric Lithosols and Orthic Rendzinas which are very calcareous; Xeric Vertisols, Calcaric Cambisols and Calcaric Rhegosols which are calcareous; and Rhodic Vertisols, Pellic Vertisols and Vertic Cambisols which are moderately calcareous;

in the northern coastal strip the soils are Pellic Vertisols which are moderately calcareous and Calcaric Cambisols which are calcareous;

soils on the southern coastal strip are Calcaric Cambisols and Calcaric Rhegosols which are calcareous; Chromic Vertisols and Pellic Vertisols which are moderately calcareous; and Gleyic Solonchaks which are very calcareous;

soils developed on the marls, limestones and chalks on the southern flanks of the Troodos massif are Calcaric Lithosols and Ochric Rendzinas which are very or extremely calcareous.

Preliminary results obtained recently from X-ray defraction analysis of clay minerals from a limited number of soils indicate that throughout a 120 cm profile of an alluvial Calcaric Rhegosol, 2:1 lattice minerals predominate with abundant montmorillonite and beidellite and some illite. The predominant minerals in two Rhodo Chromic Luvisols were illite and Kaolinite with some montmorrillonite.

2.3.5 Soil fertility and nutrient availability

As mentioned earlier the agricultural soils of Cyprus in their natural state are poor in nitrogen (0.1 %), poor in organic matter (around 1 59, poor in available phosphorus and rich in total and exchangeable potassium.

Although magnesium is generally in good supply, especially in soils developed on igneous rocks, it may be short in some others.

Lime - induced chlorosis is observed under conditions of high calcium carbonate content coupled with high moisture regimes and on calcareous soils where the surface horizon has been removed in the process of land levelling.

Zinc deficiency is by far the most prevalent micro-nutrient disorder especially in tree crops such as citrus and deciduous.

From leaf analyses manganese seems to be in short supply for some crops but this may not at present be of economic importance.

In spite of the adequate supply of soil potassium, application of potassic fertilizers does not improve the uptake of this element by irrigated tree crops, presumably because of excessive Ca⁺⁺ in the soil solution and possibly due to fixation by clay minerals.

2.3.6 Fertilizer consumption

Whereas in 1960 agriculture in Cyprus used 6 500 t of N, 7 500 t P₂O₅ and 500 t of K₂O, in recent years fertilizer consumption rose to 13 500 t N, 10 000 t P₂O₅ and 1 900 t of K₂O. Thus the value of all fertilizer imports is over £2 million a year. It is estimated that more than 50% of the fertilizer import is consumed by irrigated crops, such as citrus, potatoes and other vegetables representing only 12% of the total cultivated area.

2.3.7 Crop responses

Crops in general respond to fertilizer nitrogen applications and to a lesser extent to phosphorus. Responses of crops to soil application of potassium are an exception rather than the general rule.

Soil fertility studies were the first agricultural research activity embarked upon, long before the establishment of the Agricultural Research Institute in 1962. Since then experimental work in soil fertility has been expanded considerably to include fertilizer field experiments and plant nutrition studies of the most important irrigated and rainfed crops such as citrus, potatoes, carrots, vines, wheat and barley.

From the results of long term experiments the responses of individual crops is summarized in the following paragraphs.

a) Fertilizer Use by Major Crops

Potatoes: previous and recent experiments on fertilizer requirements by potatoes of the commonly cultivated varieties, Arran Banner and Up-to-Date, have established that high yields are attainable with only 110 kg of N applied as sulphate of ammonia and 90 kg P₂O₅ as single superphosphate per hectare per year all applied at planting. This has been re-established from recent work on the fertilization of potatoes in the main growing areas of Terra Rossa. In these experiments close planting at 18-20 cm in rows corresponding to 70 000 plants per hectare irrigated by sprinkling could produce up, to 50 tons of Arran Banner and 45 tons of Up - to-Date. Doses of nitrogen above 150 kg of N per hectare always tended to decrease production. Phosphorus on the other hand, even used at higher rates, had no ill-effect on production. Most of the fields sampled in a survey showed that they had acquired high levels of available phosphorus by the continuous use of high rates of phosphatic fertilizers. Potassium, on the other hand, has never increased yields or improved the quality of potatoes. These findings come in sharp contrast to the practice of potato growers who firmly insist on fertilizing with high doses and up to 2.8 tons/ha of the mixed types of fertilizer 14-22-0 or 14-22-9. On the basis of the present area cultivated with potatoes, it is estimated that the potato growers could save up to £250 000 per year if they were to adopt the recommended fertilizer rates.

Carrots: experiments on the fertilization of carrots grown on Rhodo Chromic Luvisols developed on igneous pebbles have shown that very high exportable yields of 75 - 80 tons/ha of the variety Chantenay could be achieved when fertilized with only 110 kg N/ha as sulphate of ammonia and 90 kg P₂O₅/ha as single superphosphate, all applied at planting. Mechanical triple-row planting and sprinkler irrigation have been used and the high yields are not only attributed to the right combination and amount of fertilizers used but also to the mechanical triple-row planting and the Sprinkler irrigation for maintaining high moisture regimes.

Citrus: within the objectives of the Agricultural Research Institute's crop programme, the study of all aspects of citrus production is of paramount importance. Nutrition and fertilizer requirements of citrus are major aspects of citrus management. Two experiments on the fertilization of Valencia oranges at Morphou (Calcaric Rhegosols) were established in 1962. The results of these experiments so far indicate that 14-year old Valencia orange trees require up to 0.75 kg N/tree as sulphate of ammonia applied in February and 0.25 kg N/tree as nitrate applied in early July to supplement the nitrogen requirements of Valencia growing in light textured soils. The phosphorus requirement under the same conditions was found to be 0.2 kg P₂O₅/tree triple superphosphate per year. Potassium, on the other hand, has not been found to affect either yields or quality of the fruit inspite of the fact that the potassium leaf levels have dropped from 1.15 - 0.65 % since 1962, However, the present levels of potassium in the leaves are considered "low" and current studies are directed towards finding ways and means to increase potassium content in the leaves. In connection with the serious problem of the creasing of Valencia oranges in the Morphou area, which causes serious losses in certain years, a number of experiments have been set up with a view to finding the cause and a remedy for this symptom.

Apples: production is important in certain regions of the island where the climate is sufficiently cold to allow the cultivation of this crop. In addition, the expansion of apple culture makes it necessary to carry out experimental work to determine the fertilizer requirements. An experiment was initiated in 1962 on a Rendzina where the nitrogen, phosphorus and potassium requirements of apples are being studied. So far, although no conclusive results can be cited, it is indicative that apples require 1 kg Nitrogen, 0.3 kg P₂O₅ phosphorus and, interestingly enough, no potassium. In another small experiment initiated at Saittas on the Lord Lambourne variety of apples, it has been shown from leaf analysis at intervals that N, P and K are continuously on the decline from the beginning of July until harvest of the apples.

Lucerne: This has been used as a test crop in a long-term field experiment at Morphou whereby the interest was to find out the direct and residual effects of phosphate fertilization and at the same time exhaust the phosphorus and the potassium of the soil. So far, it has been found that lucerne will require up to 200 kg P₂O₅/ha/year in order to maintain high production of up to 120 tons of green matter/ha/year. This is equivalent to about 24 tons of dry matter containing roughly about 5 tons of crude protein. In rotation with lucerne, potatoes have been grown and it was found that they too responded to direct application and to residual phosphorus in the soil.

Application of increasing rates of potassium to lucerne resulted in the reduction of the magnesium content. Similarly zinc was reduced from 30 ppm to 20 ppm with the application of 200 kg P₂O₅/ha.

Olives: a long-term experiment on olives in a Calcaro Chromic Cambisol was carried out in Kyrenia in which the nitrogen, phosphorus and manure requirements of olives was studied. The results over the years have shown that the best combination under trial conditions for maximum olive production was 0.75 kg N as sulphate of ammonia and 0.2 kg P₂O₅ of single superphosphate per tree per year applied in early February.

Carobs: the results obtained from a long-term experiment carried out at Paphos, have shown that fertilization with 0.75 kg N as sulphate of ammonia and 0.2 kg P₂O₅ as single superphosphate per tree per year increased yields on the average by about 30%, in addition to the increase of N and P in the leaves.

Wheat: in a recent four-year cycle of experiments on wheat fertilization in the main wheat belt of Mesaoria (Calcaro Pellic Vertisols) the nitrogen and phosphorus requirement of both Kyperounda (durum) and Pitic 62 (soft) were studied. It was found that under most conditions Pitic outyielded Kyperounda by 40 percent and that it also responded to higher rates of nitrogen fertilization. On the other hand, Kyperounda responded very markedly to the application of nitrogen as indicated by higher levels of nitrogen in the grain.

In a parallel experiment in 1968/69 on the effect of nitrogen fertilization and of supplementary irrigation at critical stages of the growth of three wheat varieties: Kyperounda, Pitic 62 and 8156, it was again verified that Pitic was superior in grain yield compared to the other two varieties. Generally, nitrogen fertilization increased yields but at the same time high rates of nitrogen were found to induce lodging of Kyperounda. On closer examination of the statistical interaction of varieties and nitrogen levels, it became clear that Pitic continued to respond at the higher levels of nitrogen applied. The corresponding yield of grain in tons/ha for 1969 at Athalassa were as follows:

With respect to supplementary irrigation no striking differences were obtained because of the high rainfall in the winter of 1968/69.

Vines: from long-term NPK experiments with rainfed vines growing on Orthic Rendzinas it has been established so far that vines respond to nitrogen application up to 150 kg N/ha as sulphate of ammonia producing on the average 7 tons of fresh grapes per hectare. However, there has been some indication that significant losses of nitrogen as ammonia may occur from application of ammonium sulphate.

Response to phosphorus application has been observed in one location (available soil P 12 ppm, Olsen 25°C).

No responses have so far been observed from potassium applications.

In a sultana table grape experiment on a Chromic Vertisols irrigated once in early May there were marked linear responses to nitrogen up to 200 kg N/ha applied as sulphate of ammonia (N_o 10 tons fresh grapes/ha, N₃ 15 tons fresh grapes/ha). °

No phosphorus or potassium responses were obtained so far.

In order to complement and to evaluate meaningfully the results obtained in field fertilizer experiments extensive and detailed analytical work is carried out on soil and plant material.

Concurrently nutrient status surveys, especially of high cash tree crops such as citrus and deciduous, are undertaken from time to time in order to establish the effect of current fertilizer practices on yield and quality and to compare the results of these surveys with the norms of macro- and micronutrients obtained from long-term experiments.

In the case of Valencia oranges we have established that the norms for N, P and K, Zn, B, Mn and Cu in six-to-seven month old leaves from non-bearing growth suggested by Californian workers are, in the main, applicable to Cyprus conditions as well.

From nutrient status surveys we have also found that in citrus high leaf nitrogen levels were prevalent as a consequence of excessive amounts of nitrogenous fertilizers used by the growers which had resulted in the deterioration of fruit quality.

2.4. Water Resources

The Government of Cyprus, recognizing the urgent need to implement an overall water policy and a masterplan for the utilization and development of the island's scarce water resources, received UNDP assistance in instituting the Cyprus Hater Planning Project with the main object to take an inventory of the island's water resources and to identify viable development projects. The conclusions of this survey were:

(a) the total available water was estimated around 960 × 10 m per year of which some 400 × 106m³ are being used at present for various purposes.

(b) even when full development of the water resources has taken place by the end of this century, it is estimated that water utilization will be around 600 × 106m³ per annum or about 60 percent of the potential water, and

(c) the additional water available to agriculture will be insignificant.

Thus future projections for increasing the irrigable land do not seem promising. However, in view of the importance of irrigated agriculture, which contributes over 55 percent of the value of agricultural production, the urgency for the most economic and efficient use of the presently available water resources is pressing.

2.4.1 Water use research

Given this state of realities, apart from the various measures taken by Government for promoting the most efficient use and conservation of the available water resources, water use field studies have commended a high priority in the overall programme of the Agricultural Research Institute since its establishment. A major part of the activities in the soils and water use field is devoted to the determination of the water requirements of irrigated crops such as citrus, potatoes, vegetables and table grapes, including comparison and evaluation of methods of irrigation. In parallel, microclimatological data are collected for calculating evapotranspiration for comparison with values determined in the field.

Salinity studies are undertaken in conjunction with each irrigation field study with the object of supplementing crop water requirements with those of leaching. The results obtained so far from this work are summarized below.

2.4.2 Water requirements of crops

Citrus

Even with good quality irrigation water (EC-1 mmho/cm) and inherently good drainage, salinity tended to build up within the root zone when low amounts of water were applied which did not permit leaching.

The experiment has now been modified to allow a wider range of amounts of water to be applied in order to determine the additional field leaching requirements.

Potatoes

Table Grapes

Method of Irrigation	Water applied m3/ha.				Mean method
	0	1500	2400	3800	± 0.86
	± 1.22
Sprinkler	9.50	9.77	12.92	13.13	11.33
Border	7.72	10.54	12.91	12.79	10.99
Mean amount ± 0.86	8.61	10.16	12.92	12.96

From soil moisture measurements with a neutron probe it was observed that moisture moved down to 60 cm when irrigated with 1 500 m³/ha and to 90 cm and 120 cm for 2 400 m³/ha and 3 800 m³/ha respectively.

2.4.3 Methods of irrigation

A preliminary study initiated in late 1971 and continued in 1972 aimed at comparing the conventional method of furrow irrigation with the sprinkler and trickle methods.

The test crop used was sweet peppers. The evaluation of these methods, the moisture movement and the salinity profiles as well as the practical and economic problems involved are to be assessed.

2.4.4 Field water balance studies

Two studies initiated in 1972 are continuing with the main objective of evaluating the drainage component in the field water balance equation for a more precise determination of crop water requirements.

Soil moisture changes are followed by neutron probe and tensiometry in order to establish the hydraulic gradient and calculate the hydraulic conductivity of the profile at different depths.

Data obtained so far indicate that the unsaturated hydraulic conductivity varies widely from layer to layer due to textural difference and the sequence of the soil horizons making the evaluation of the drainage component rather difficult. This complicating situation is likely to occur in most irrigated soils of the island.

2.5. Concluding Remarks

The present character of the soils of Cyprus is the result of the strong effect of aridity on the parent material in a slow process of soil formation and horizon development resulting in the omnipresence of calcium carbonate throughout the profile. Aridity is the dominant feature also of lands in the Mediterranean basin.

In general the agricultural soils of Cyprus are poor in nitrogen and phosphorus and rich in potassium.

The high calcium carbonate contents with attendant high pH impose restricting conditions on the uptake of micronutrients especially zinc, iron and manganese.

The fertility of the soil can be easily restored by the application of the main nutrient elements in the form of fertilizers and of foliar sprays of micronutrients.

A basic requirement for the most efficient use of fertilizers and soil nutrients in general is the continuous supply of moisture to the soil. Prolonged moisture deficits created by the semi-arid climatic conditions have to be supplemented by irrigation whenever possible. However, the scarcity of water resources imposes a further restriction in bringing more land under irrigation and at the same time it underlines the necessity for the meticulous use of water and fertilizer in order to increase crop yields, maintain a high quality of agricultural produce and lower production costs.

Thus the necessity for applied research on the fertility of calcareous soils and on the most efficient use of the scarce water resources available is of paramount importance, not only for Cyprus, but for the Region as a whole.

The Government of Cyprus in perpetuating an effective programme in the development and utilization of the island's land and water resources will lend its active support to regional projects under the Near East Regional Applied Research Programme.

3. Iran

3.1. Introduction

Iran, or historic Persia, is situated between 25 and 39.45° N and 44 to 63° E, covering 165 million hectares of lands with wide ranges of:

Climate:	- Humid to Subhumid in the north
	- Semi-arid in the north-west and west
	- Arid to hot desertic in the east, south-east and central Iran
Geology:	- Basic Sedimentary rocks, ultras-basic igneous and acid extrusive rocks of the Precambrian era, up to present time sediments
Vegetation:	- Deciduous forests in the north and west
	- Shrubs and Scrubs in the north-west and south-west
	- Steppe and salt tolerant bushes in arid and desertic areas
Physiography or Geomorphologic Land Types:
	- High altitude mountains (up to 6 000 m)
	- Hills, piedmont plains, river alluvial plains
	- Saline flood plains and low lands.

Iran is one of the countries with most parts affected by dry or arid conditions which account for the formulation and accumulation of calcareous materials in some soils as well as salt in some others.

3.2. Calcareous Soils in Iran

According to the studies on soils carried out since 1953, it is clear that with the exceptions of the Caspian Zone, where CaCO₃ has been leached from the soil by high rainfall, the central and south-eastern deserts which are affected by salt and a few small areas of non calcareous origins, the soils of the rest of the country are affected by or combined with lime comprising from 10 to 60% of the soil constituents and/or up to 100% of the calcareous stones.

According to "The Soils of Iran" the areas and the association of calcareous soils are as follow:

Soil Association		Area in 1 000 ha
	I - Soils of the plains and valleys
1	Fine textured alluvial soils (mainly calcareous)	4 750
2a	Coarse textured alluvial and colluvial soils and Regosols	4 500
	II - Soils of the plateaux
7	Brown soils	6 000
8	Chestnut soils (calcareous horizon below 50 cm)	1 000
5-2a	Desert soils - Regosols	8 000
6.2	Sierozem soils - Regosols	9 000
7-15	Brown soils - Lithosols	2 000
	III - Soils of the Caspian Piedmont
11	Brown forest (mainly calcareous in sub-soil)	300
	IV - Soils of the dissected slopes and mountains
12	Brown soils - Rendzinas	400
13	Calcareous Lithosols, desert and Sierozem	35 000
14	Calcareous Lithosols from saliferous, gypsiferous materials	12 000
15	Calcareous Lithosols, Brown and Chestnuts	24 000
	Total	106 950

The figures show that around 65% of the soils of the country are calcareous.

3.3. The Management and Land Use

Calcareous soils are productive under semi-arid to subhumid conditions or with irrigation in the following circumstances:

(i) when water is available and slope and topography of the land are suitable; these soils are used mainly for irrigated, annual crops or fruit trees;

(ii) when precipitation is sufficient for dry farming (300-600 mm/h) nearly all the slopes and even the tops of the hills in some places are under dry farming (wheat or barley);

(iii) when the rainfall is 150-300 mm/a, or yearly distribution is not suitable for cropping, or when rainfall is well above 300 am but there is no suitable topography for cropping, the main land-use is pasture or forest;

(iv) in the Caspian zone, on cretaceous and jurassic limestones with very shallow to very deep soil cover of rendzina to brown forest soils there are highly productive forests;

(v) when rainfall is lower than 150 mm/a, and the evaporation is also high, the lime or gypsum is concentrated immediately below the surface and occurs mostly together with salt; these areas are naturally seasonal or occasional grazing lands or waste lands and deserts, with no vegetation;

	million ha
Occasional grazing	58
Deserts, waste, urban	43
Marginal grazing	25
Productive range	19
Fallow	12
Dry farming	4
Irrigated cropping	3
Forest	1

3.4. Research and Studies

Different organizations in the Ministry of Agriculture and Natural Resources have various activities on the reclamation or management of lands and soils. Within these organizations the Soil Institute plays the major role in research and studies on soils and has many experimental fields throughout the country.

During the past few years the Soil Institute, which consists of various divisions, has carried out the following activities among many others:

(i) Land Resources Inventories: various land resources of the country and their potentiality or capability for different land uses have been defined. In this respect more than 40 million ha were surveyed and mapped in the last four years by the Land and Soil Evaluation Division.

(ii) Soil and Land Classification: this activity was started in 1952 and a great deal of work has been done on the classification of lands for irrigation and on the soil classification of Iran.

(iii) Soil Fertility Research and Soil and Water Management: many studies, combined with experimental field work all over the country, have been carried out on soil fertility, soil and water management and salt leaching in the last 10 years by the Soil and Water Management Division. This same Division has also done plant nutrition studies in relation to CaCO₃ content and iron and zinc deficiencies in calcareous soils.

(iv) Soil and Water Conservation: soil conservation on a country-wide scale has been done by the Natural Resources Organization and includes such activities as: afforestation of many degraded forests, dune stabilization, plantation of drought resistant plants in desertic areas etc. Conservation of agricultural soils, however, comes under the Division of Soil and Water Conservation and includes such work as the installation of large scale experimental stations in areas of calcareous soils, e.g. Quin (160 km west of Teheran) and on the basic igneous soils of Tickmeh-Dash (500 km north-west of Teheran) and many other stations in the Provinces.

4. Iraq

4.1 Introduction

At present the main problem for agricultural development in Iraq is salinity. Other problems, including the presence of between 15 and 35 percent CaCO₃, are of lesser importance. Recently, studies were started on the effect of CaCO₃ on the physical, chemical and nutritional characteristics of calcareous soils in Iraq. The effect of CaCO₃ on phosphorus fixation and that of teaching and cropping on CaCO₃ content have been studied but more work is needed in order to obtain definite and clear information on the behaviour of these soils.

4.2. Physiographic Regions of Iraq

The physiographic formation of Iraq is composed of five zones, namely: mountain ranges, undulating low hills, desert land, the Jezira and the Mesopotamian Plain.

4.3. Parent Material of Soils

Most of the parent material in the mountain ranges is limestone; in the undulating low hills it is gravels, conglomerate, sandstone or mudstone; in the Jezira gypsum is dominant, while in the desert land it is limestone. The parent material of the alluvial Mesopotamian Plain is formed by sediments of the Tigris and Euphrates rivers and is generally calcareous containing 15 to 35 percent CaCO₃ in the top metre.

4.4. Distribution of Lime in Iraqi Soils

Most Iraqi soils contain from 15 to 35% lime with few having less than 15% or more than 35%. In the plains of the mountain ranges some soils have only 2-7% in the surface but more than 50% in the sub soil. In the low hills, the soils have more than 25% lime content throughout the profile. The Jezira soils generally contain more than 6% CaCO₃ while those of the desert lands have more than 25% in the surface and up to 50% in the subsurface layers. The calcareous soils of the Mesopotamian Plain contain from 15 to 35% lime mainly as CaCO₃ (90%) and MgCO₃ (10%).

Generally, the soils of the coarse textured levee contain less carbonate than those of the fine textured basins which could be caused by:

i) better drainability of the levees; consequently leaching of carbonates would be more than in other soils;

ii) the decrease in size of the lime particles as they move in the water stream before being deposited on the fine textured soils of the basins.

4.5. Distribution of Lime in the Soil Profile

The lime distribution is usually homogenous within the soil profile, but in recent sediments the top metre has a higher lime content which increases with depth and with the age of these sediments. In the old soils of northern regions, the lime content also increases with depth.

In the calcareous soils of Iraq, lime can be found in the following forms: fine calcite, calcite intercalary crystals, calcite crystal chambers, calcite crystal tubes, calcite crystal sheets, calcitan lining some pores, neocalcitans deposited around some pores, amorphous deposits as a result of high groundwater levels in southern Iraq, soft lime nodules, Petrocalcic layer and Lithorelics.

The lime in the soil of the Mesopotamian Plain originates from the limestone rocks of the mountain ranges. Due to soil erosion, lime is transported in the rivers' streams as small particles and deposited under the same conditions as the sand, silt and clay soil particles. A few of the results taken from thousands of samples are presented in Table 1 and the following remarks can be made.

i) There is a difference in the lime content of the sediments transported by the Tigris and Euphrates rivers; the lime content in the former being higher by 2-5%. This characteristic can be used to differentiate between the sediments of the two rivers.

ii) Coarse textured soil samples contain less lime than those with a fine texture as shown in Table 2. This is due to the effects of turbulence, caused by the velocity of the flowing water on the size of the suspended lime particles and their sedimentation; a decrease in velocity of flow permits the sedimentation of finer particles.

Table 1. Average lime content to a depth of one metre in the soils of the various Governates of Iraq

Governate (Arabic)	No. of samples	Lime content %
		Range	Average
Basra	24	27 - 38	33
Muthanna	8	23-28	26
Thi-qar	4	27 - 30	28
Waset	20	24 - 35	29
Babylon	41	18-32	27
Baghdad	45	21 - 38	28
Anbar	11	18 - 39	28
Diala	10	26 - 35	31
Kirkouk	11	23 - 36	32
Arbiel	1	···	20
Sulaimaniya	5	12 - 18	14
Nineveh	1	···	6

Table 2. Relation between soil texture and lime content in representative samples from two projects

Project	Light textured profile			Heavy textured profile
	depth cm	texture	lime %	depth cm	texture	lime %
Almouthana	0 - 10	clay	29	0 - 14	sandy loam	14
	10 - 40	clay	28	14 - 36	silt clay loam	20
	40 - 70	clay	27	36 - 66	sandy loam	18
	70 - 95	clay	28	66 - 96	sandy loam	20
				96 - 120	loamy sand	17
Greater Mussayeb	0 - 12	clay loam	29	0 - 16	sandy loam	20
	12 - 34	clay	30	16 - 37	loamy sand	19
	34 - 65	clay	32	37 - 47	silt loam	26
	65 - 94	silt clay	30	47 - 74	sand	19
	94 - 129	silt clay	27	74 - 104	loam	24
				104 - 150	loamy sand	19

4.6. Effect of Lime on Reclamation of Iraqi Soils

Although 15 to 35% lime is found in most Iraqi soils, as shown in the Map, its presence does not pose a serious problem to land reclamation and development as is the case with a high salt content. Studies have been carried out in various parts of the country on soil reclamation and the following are cited as examples.

i) Experimental work was started in Dujailah area (Mesopotamian Plain) in 1956. Soils were highly saline with about 6% salts in the top 30 cm, of medium texture, below average permeability (80 cm/day) and with a 20 - 30% lime content. It proved possible to reclaim these soils by leaching and most field crops could be grown thereafter.

ii) Studies, investigations and reclamation work started in Abu Ghraib (Mesopotamian Plain) in 1969. The soils were highly saline, of heavy texture and contained 25 - 30% lime. Due to the presence of lime and the possibility of leaching excess salts, cropping was successfully achieved afterwards.

iii) Reclamation experiments in Twairey took place from 1961 to 1969. This area represents the saline soils in the upper basin of the Euphrates river. Salinity was 74 mmhos/cm, the texture varied from sand to light clay and the lime content was about 25%. Results of experiments indicated that the water table could be lowered, salinity decreased and that economic yields from all crops included in the rotation (as shown in Table 3) could be produced. No side effects were observed from the presence of lime in the soils.

Distribution of lime in soils In different physiographic region of Iraq (to a depth of one metre)

Table 3. Relation between reclamation procedures, wheat year net returns per donum^1/ during three years

Reclamation Procedure	Brains		Average yield of wheat in the last year per donum 1/	Salinity		Net return
	distance	depth		Initial	find	Dinar	Fils
	metres
1. Leaching with 80 en;
barley, green gram,
barley, green gram,
wheat	100	1.8	265	11	0	16	600
2. Leaching with 30 cm;
wheat, fallow, wheat,
fallow, wheat	100	1.8	318	26	0	20	200
3. Leaching with 30 cm;
wheat	100	1.8	385	17	0	21	100
4. No leaching;
barley, rice berseem,
berseem, wheat	100	1.8	421	7	0	13	800
5. No leaching;
barley, fallow,
barley, fallow, wheat	50	1.8	393	28	0	17	300

^1/ 1 donum = 2 500 m²

iv) Studies, investigations and reclamation work in the Tanouma Basrah, in the lower basin of the Euphrates, were carried out from 1967 to 1970. The soils were heavy textured, very highly saline and the lime content varied from 30 -35% Reclamation and leaching of these soils was not a problem and no amendments were needed except for the application of organic matter after leaching to increase soil fertility and improve structure.

v) Studies and investigations in Hawejah project, representing the northern foothills, took place from 1968 to 1970. The soils were of medium texture, highly saline with 20 - 25% lime content and had a high water table. Good results were achieved from leaching and reclamation. Organic fertilizers had to be added to improve the soil properties and increase crop yields.

vi) Studies were carried out (1971 to 1972) on the effectiveness of drains in the Khalis project (Mesopotamian Plain). Three sites were selected for the study. The depth of the drains was constant (1.8 m) but the distance between them was varied.

a) In Sodirah the soils had a fine texture and were badly structured. Salinity was low and the lime content between 23 and 31%.

b) In Masary the soils bad a fine texture, bad structure, very low salinity and 27 - 31% lime.

c) In Abbassy the soils had a fine texture, bad structure, medium salinity and 23 - 30% lime.

4.7. Results and Discussions

1) Results obtained from the experimental projects cited and from other regions in Iraq show that the presence of lime does not create noticeable problems in land reclamation and utilization. Lime is not found as hard formations either on the surface or in the soil profile and this may be due to the presence of a high salt content and the consequent effect on solubility of lime and its leaching to lower horizons.

2) The studies carried out in Abu Ghraib (1964-1966) showed that line is an important factor in phosphorus fixation. Plants were unable to utilize all the applied phosphorus in the first year. The residual effect remained for two years or more.

3) No studies have been made on the effect of lime on the availability to plants of nitrogen and potassium; there is a need for such studies.

4) No studies have been made on the effect of lime on the physical properties of Iraqi soils. It is to be expected that in the presence of CaCO₃, the soil moisture retention would be less, the hardness would increase and the porosity, permeability and availability of water would be less. These characteristics need investigating under Iraqi soil conditions.

Ideal utilization of the land resources calls for thorough investigations and studies based on survey, classification and evaluation of the soils to select those most suitable for vertical expansion and those requiring improvement for horizontal expansion. Such improvement and expansion would require the followings:

i) Priority being given to soils highly responsive to reclamation and to those costing less and giving higher returns at a faster rate. Such soils could provide savings which would then be used for further development of new lands and improvement of degraded soils.

ii) The establishment of specialized agencies and organizations to carry on the responsibilities of land reclamation. In such organizations, an integrated approach to planning, execution, management and research should be assured.

iii) The certain availability of irrigation water (surface or groundwater), which is the limiting factor in soil reclamation, development and crop production. The use of the appropriate irrigation method, allocation of the right amount of water needed for the developed areas and knowledge of crop water requirements are also required.

iv) The identification and supplying of agricultural machinery adapted to local conditions, together with technically trained staff for its operation and maintenance.

v) Planning for the economic utilization of land resources through intensive farming and proper management of soils and crops.

Since most of the countries participating in this Seminar are in the arid and semi-arid regions where salt affected, waterlogged, sandy and calcareous soils are of wide occurrence, and each group has its own problems, it is necessary to:

1) cooperate and coordinate with each other and with the assistance of FAO to make full use of their available resources and experience;

2) support and strengthen the Regional Centre for Research and Studies on Arid and Semi-arid Zones, sponsored by the Arab League, and establish specific branches in different countries, as the need indicates;

3) support and develop training centres in land reclamation in some countries and specially the training centre for land reclamation in Iraq as a nucleus for providing trained staff for the region. The Government of Iraq is giving full support to this centre and funds have already been allocated for it in the development plan 1970-1974;

4) adopt a regional applied research programme on calcareous and sandy soils in cooperation with FAO and accelerate the implementation phase of the applied research programmes on salt affected and waterlogged soils. The requested experts and equipment should be made available to those countries which have already supported the programme including Iraq. The approved programmes are being executed in Iraq in cooperation with FAO;

5) follow up research activities and field studies on reclamation and utilization of reclaimed lands. There should be discussion of research results and these should be disseminated through regional symposia and scientific conferences.

5. Jordan

The soil of Jordan has developed mainly from secondary rocks that differ in their geological composition and age.

Two main kinds of limestones: hard and soft, exist in Jordan. In addition, sandstone and calcareous sandstone form the crust of a small area in Jordan. The soils of the Jordan Valley have developed mainly from alluvial materials.

These factors in addition to low weathering of the rocks are the reason for the content of CaCO₃ in most of the Jordan soils. The percentage and distribution of CaCO₃ particle size vary in these soils according to their origin and their degree of weathering.

Pour main groups of calcareous nature soils exist in the country.

5.1. Red Mediterranean Soil (Terra Rossa)

This group of soils has developed mainly from hard limestone which has been classified by geologists in the Ajlum series. These soils are red to brown with a clayey texture and a clay content of 35 - 60% and occasionally up to 70%. Most of the CaCO₃ is in the course fraction of the soil particles.

Chemical analysis of several hundred samples of these soils has shown that they are salt free with a base saturation of about 100% and pH of 7.8 - 8.2.

This group of soils-form most of the uplands parallel to the River Jordan and cover an area of about 13 000 km². They usually receive 250 mm/year rainfall in the south to 600 mm in the south west.

They are planted with crops, mainly under rainfed conditions. Barley and wheat are the major crops grown in the south; wheat and legumes in the winter and vegetables in the summer are grown in the central area. In the southern hills, wheat, legumes and summer vegetables are grown on the plains while most of the rough hills are covered with forest and fruit trees, mainly olives.

The main problems facing these soils are:

a) The acceleration of soil erosion which is evident and is due to poor tillage practices, as a result of the misuse of modern farm machines.

b) The necessity for water conservation, since almost all of them depend mainly on winter rain and there is a long drought period of about seven months.

c) Their usually high potassium content and poor phosphorus with a narrow C/N ratio.

They comprise the bulk of soils in Jordan and cover about 80% of the country. They developed mainly from soft limestones (chalks and marl) which have been classified by geologists in the Balqa series.

These soils are brown to yellowish brown with a clayey texture containing from 35 - 60% clay. The CaCO₃ content ranges from 20 - 70% and is usually in both the clay and silt fractions.

Most of these soils are salt affected with an EC range from 1 mmhos/cm to 50 mmhos/cm and frequently to 200 mmhos/cm and an ESP range from 20 - 50. They receive an average annual rainfall of 150 mm to less than 50 mm and are mainly poor range lands, dotted with intensive agricultural areas where underground water is available.

The importance of these soils to Jordan's agricultural economy depends upon the discovery of more groundwater sources which could lead to an increase in irrigation water for the development of these soils; but salinity and sodicity problems would then have to be tackled.

5.3. Alluvial Soils

This group of soils are either alluvial or developed from alluvial material. The alluvial soils are formed in a very narrow strip on the banks of the River Jordan; other soils are developed either from lisan marl (kattars) or from materials developed from the surrounding hills and mountains. The latter soils form the main agricultural land in the Jordan Valley which will be discussed in this category.

These soils have a colour range from very dark grey to yellowish brown with a silty clay loam to clay texture. The CaCO₃ content ranges from 15 - 60% and the size distribution varies according to the origin of the soils.

Their chemical analysis reveals the wide variation in their salinity, the trend of which increases from 1 mmho/cm in some northern areas to as high as 50 in the south. In many cases, salinity is mainly due to waterlogging sodicity which is of minor importance with ESP usually below 20.

These soils covers about 50 000 hectares, 15 000 of which are under intensive irrigation and this area is planted mainly with off-season vegetables, citrus and banana.

The main problems of these soils are:

a) The rise of the water table in certain areas which was caused by both over-irrigation and the lack of proper drainage systems.

b) The fertility status of these soils must be studied more comprehensively. In general, most of them are rich in potassium and poor in phosphorus.

c) Chlorosis in many of the crops, and particularly in citrus, is evident and might be due to a high CaCO₃ content in addition to over-irrigation and some other factors.

6. Lebanon

6.1. Introduction

The problem of calcareous soils in Lebanon has been taken into consideration since the phylloxera invasion which started in our vineyards in the 1930s. The first function of the soil laboratory at the Agricultural Research Institute at Tel Amara was to estimate the calcium carbonate content in the soil in order to select the best rootstock of vines. The soils were classified then by Billault according to their calcium carbonate content and their colour.

It is well known that the Lebanese mountains are formed by Jurassic and Cretaceous limestone of various hardness; Cenourian and Eocene are mostly formed by marl and soft lime deposition. This lime is an important factor in the soil formation which is considered of autochthonous and/or allochthonous origin. As a result of the variations in climate, the Bekaa valley shows nearly all kinds of calcium carbonate formations mentioned by Ruellan, 1970. In the mountainous region where slopes are steep, the erosion is very active and the soils are shallow. Recently, in the last five years, soil scientists in Lebanon have become more aware of the problems of the management of these soils. Team-work by soil scientists from the Lebanese Research Institute with the cooperation of the Litani Office, the American University of Beirut (AUB) and FAO started a research programme as follows.

6.2. Soil Survey

The first step of the research programme was the classification of the soils. In collaboration with FAO soil surveyors, the soils were classified according to their physiographic characters, especially for irrigation purposes. The most important factors considered were the depth of soil, the lime content, the texture, the colour, the slope and the presence of stones and gravel.

In the south of Lebanon four soil series were distinguished according to their calcium carbonate content:

1. Series with less than 10% active CaCO₃
2. Series with 10 - 20% active CaCO₃
3. Series with 20 - 30% active CaCO₃
4. Series with more than 30% active CaCO₃

6.3. Soil Physics

With the collaboration of ORSTOM experts, the actual research programme deals with the hydrodynamic properties of the soils, the conception of R.U. (reserve en eau utile), the evolution of structure of soils under irrigation and the relationship between the water holding capacity and the lime content in the silt and clay fractions, considering at the same time the type of clays present.

6.4. Soil Chemistry and Fertility Programme

A joint programme with the collaboration of AUB on the application of soil mineralogy to the management of soil fertility has been initiated. The soil mapping units have been studied according to their physical, chemical, and mineralogical properties. The amount of active and total calcium carbonate in each soil mapping unit was related to phosphorus fixation. The recommendations for fertilizers, irrigation and other soil management practices are based on the fact that soils of common mineral composition have the same physical and chemical properties.

Studies on phosphorus forms, phosphorus retention and the fate of added phosphate fertilizer were done on selected calcareous soils. The effect of amorphous materials present in calcareous soils was also studied in relation to phosphorus fixation. Methodology is being stressed to devise or modify existing methods to fit calcareous soils. In other words, we are studying the applicability of laboratory methods in relation to field conditions. Already modified methods have been published for ammonium, potassium and phosphorus fertilization for calcareous soils. Research is now in progress to study the use of chelates, reducing agents such as hydroquinone, organic matter and minor elements in relation to yield on calcareous soils.

Another part of this programme is the availability of nutrients and the antagonism of calcium - potassium.

In addition to the above collaborators, an ORSTOM expert is studying the effect of organic matter in relation to soil structure and yield on irrigated calcareous soils. In the field a set of lysimeters was also established to study the evolution of soil structure and mobility of calcium carbonate in drainage water.

Laboratory research has also been initiated using soil columns leached with distilled water. The nobility of CaCO₃ is compared with that obtained in the field by lysimeters.

6.5. Clay Mineralogy

The mineralogy of 48 profiles covering the most important agricultural soils were identified. The lowland north of Tripoli was mostly montmorillonitic. Nine of the soils have a high kaolin content from the central Bekaa valley, south east of Tripoli, and the southern part of Lebanon. Central Bekaa, south Bekaa and north of Tripoli also showed weak kaolin contents.

Illite, vermiculite and chlorite were also identified in the above profiles with various concentrations in addition to kaolinite and montmorillonite.

6.6. Soil Irrigation and Agronomy

Tel Amara irrigation department, in collaboration with Litani and FAO scientists are studying water management practices, irrigation methods (sprinkler, furrow and drip irrigation), water need and water distribution.

Modern meteorological equipment is already installed to collect data for evapotranspiration studies.

Agronomists are trying to select the best varieties of forage, vegetables and fruit tree crops giving the highest yield on calcareous soils.

7. Libyan Arab Republic

PART I: Genesis and Classification of Calcareous Soils in Jebel El Akhdar

7.1. Introduction

The Jebel El Akhdar occupies the greater part of Northern Cyrenaica and is roughly 250 km long, east to west, To the south and the east the ground falls away very gradually but the northern part is delineated by two steep escarpments.

All the exposed rocks of the area are sedimentary and are mainly marine limestones. The oldest are Cretaceous and the youngest Marine Pleistocene, but most of the area in question must be regarded as composed of Eocene with subsidiary Miocene.

7.2. General Conditions

The Jebel El Akhdar is a mountainous region which consists of two plateaux running parallel to the seashore. Its annual rainfall varies between 300 - 600 mm.

The lower lying plateau has an elevation between 200 - 400 m. The upper plateau, whose elevation varies from 500 - 700 m is extended southward by a higher zone with a gradual transition and reaches 876 m at its highest point; this latter zone is sometimes called the third plateau.

The upper plateau is composed of Oligocene and more rarely Miocene limestone formations. The substratum is either hard limestone on which are found ferro-siallitic soils, or chalky limestone associated with rendzinic or with brown limestone soils, or marls covered with very clayey vertic soils.

The landscape consists of hills covered with vegetation like Pistacia lentiscus, oleasters, Cypressus phlomis, Cistus. These vegetal species are replaced by a herbaceous cover of Artemisia herba alba south of the 300 mm isohyet.

The lower plateau is made up mainly of older (Eocene) covered hard limestone, which is affected by an intense karst erosion related to the dissolution of the limestone.

The limestone massifs are deeply eroded. The intense fissuration of the hard limestone facilitates the penetration of water and the surface of the karst is broken up and contains many pockets and shafts in which the shrubs, Juniperus phoenicea, Pistacia lentiscus and oleasters develop their root system.

The alteration of limestone is most often a red decarbonation clay terra rossa on which ferro-siallitic soils are formed and sometimes a yellow decarbonation clay or terra fusca on which brown ferro-siallitic soils are formed.

7.3. Climatology

The Mediterranean climate characterized by rain in winter and a dry season in summer may be subdivided in two Mediterranean bio-climates:

1) Sub-Humid Mediterranean Bio-climate

It is characterized by an average rainfall greater than 500 mm and an average temperature of 18°C. This bio-climate corresponds to the upper plateau.

2) Semi-Arid Mediterranean Bio-climate

Average annual rainfall is between 300 and 500 mm and average annual temperature is about 19°C. This bio-climate corresponds to the lower plateau.

Soils are classified according to the French classification: reference "Travaux de la Commission de Pédologie et Cartographie des Sols" 1947 Edition: Institut National de la Recherche Agronomique.

The major units are the following! Class, Sub-class group, Sub-group.

The calcareous soils in Jebel El Akhdar are classified under the class of calcimagnesian soils.

7.5. Class of Calcimagnesian Soils - Sub-class of Carbonated Soils

These soils are characterized by the presence of alkaline earth ions and, in particular, of calcium carbonate. The profile is of the type AC or A (B) C, without there even being a horizon B. In the horizon A, the organic matter is closely related to the mineral elements and forms a very stable complex with them. The complex is saturated with calcium and secondarily, with magnesium. The pH is basic and always greater than 7.0. The structure is granular and finely polyhedral.

The sub-class of the carbonated soils includes the following groups.

7.5.1 Group of rendzinas

These are carbonated calcic, thin 20 to 40 cm soils having a clearly granular or finely sub-angular structure often including limestone pebbles. The parent material consists of a carbonated rock.

Example :	Profile (Sidi Gharib)
Landscape and Vegetation:	Plateau with small slope, cereals.
Description
0-30 cm:	Brown, 10 YR 8/4, sandy clay loam, vigorous effervescence, granular, loose, low consistency, fresh, many roots.
30 - 50 cm:	Yellowish white with rusty and ochre passages. Beds of limestone in plates mixed with friable, powdery limestone.

The rendzinas are particularly suitable for cereal farming. The chalky substratum is a favourable element for water retention in depth and crops can benefit from an additional water reserve stored by this subsoil. Also, it is to be recommended that the sterile chalky substratum should not be raised and that crops sensitive to chlorosis should not be grown.

7.5.2 Group of calcareous brown soils

These are calcic carbonated soils having a structural horizon (B). Two sub-groups are distinguished 2

(a) Calcareous brown soils
(b) Vertic calcareous brown soils

Example:	Profile (Al Haj Younis)
Landscape and Vegetation:	Plateau, cereals.
Description
0 - 30 cm:	Dark brown, 10 YR 3/4, clay loam, vigorous effervescence, grumous low cohesion, low consistency, fresh, quite numerous roots.
30 - 50 cm:	Greyish brown, 10 YR 4/3, clay, vigorous effervescence, sub-angular, low cohesion, average consistency, fresh, quite numerous roots.
50 - 80 cm:	Light grey with white stains 10 YR 4/2, clay loam, vigorous effervescence, transition horizon, low cohesion, average consistency, fresh, some roots.
80 -100 cm:	Chalky limestone, powdery and friable.

The calcareous brown soils are rich in organic matter (3 to 4%), well structured on the surface and generally thicker than the rendzinas.

(b) Vertic calcareous brown soils

This sub-group corresponds to agrillaceous calcareous brown soils in which the subsoil exhibits vertic characteristics, polyhedral to prismatic structure, presumably with swelling clays having a high exchange capacity.

Example:	Profile (Al Haj Younis)
Parent Material :	Marl
Landscape and Vegetation :	Hilly plateau, cereals
Description
0 - 20 cm:	Yellowish brown, 10 YR 4/3, clay, vigorous effervescence, grumous structure on surface, then sub-angular, coherent, pasty consistency, fresh, not many roots.
20 - 100 cm:	Yellowish grey, 10 YR 5/4, clay, vigorous effervescence, polyhedral, shiny slip faces, coherent, pasty consistency, fresh, few roots.
100 cm:	Yellowish marl with small friable calcareous nodules.

These carbonated soils are characterized by their high clay content, their poor structure and their compactness. These characteristics are reflected in poor internal drainage, the permeability rate is low, K - 0.9 cm/h.

The vertic calcareous brown soils are difficult to work owing to their compactness in the dry state and their plasticity in the wet state. Consequently, this land is difficult to improve and must be tilled taking into account its wet condition.

REFERENCES

Coop, S.C.T, Mise en valeur agricole du Djebel Akhdar. Programme d'Etudes Pédologiques.

Groupement d'études français en Libye. 1972, Soil and Hater Resources Survey for Hydro- Agricultural Development. First Draft November.

Habert, P. 1964, The Soils of Northern Cyrenaica. FAO Libya Mission. Ben Ghazi.

Lamoureux, X. 1968, Les sols bruns méditerranéens et les sols rouges partiellement brunifiés du Liban. Cah. Orstom Série Pédologie Vol. 1.

Price, R.W. 1968, Soil survey of selected areas in the eastern, western and southern Governorates of Libya. Development of tribal lands and settlement projects. Trust Fund 94. Rome.

PART II: Reclamation and Management of Calcareous Soils in Cyrenaica

7.6. Introduction

The soils of Cyrenaica are mainly calcimagnesic,

These soils have the common characteristics of a fine clay loam or very fine clay texture and a basic reaction (pH higher than 7.5) when they are decarbonated. They are therefore susceptible to chlorosis especially as the limestone content is high. This should be taken into account when choosing crops.

The soils of Cyrenaica have a low phosphoric acid content and the ferro-siallitic soils are deficient in this element.

As the majority of the soils are of a carbonated or calcic nature with a calcium saturated complex, the conditions for their use and fertilization are given below.

7.7. Chemical Fertility

7.7.1 Nitrogen fertilization

Calcareous and calcic soils nitrify easily but the nitrates are mobile and carried down into the soil. It is therefore necessary to add nitrate fertilizers in accordance with requirements and with the vegetative cycle of the crop. Suitably placed ammonium sulphate appears to be more valuable than nitric fertilizers.

7.7.2 Potassium fertilization

The sharing of the K ions between the soil and the plant is related to the nature of the clay. Ferro-siallitic soils consist mainly of montmorillonite and of some illite.

A small part of the potassium in the montmorillonite remains available for the plant (potash retro-gradation phenomenon).

Thus even in a soil sufficient in exchangeable potassium, the nutrition of the plants depends upon the liberation of the non-exchangeable potassium.

In the case of the soils of Cyrenaica, the potassium migrates slowly and the open-structured clays retain the K ions. Potash requirements are relatively high and it is necessary to apply fertilizers as required by the crops.

7.7.3 Phosphate fertilization

In a calcareous soil, phosphorus can be insolubilized in the form of calcium phosphate. Ferro-siallitic soils are deficient in this element. The insoluble phosphorus in the calcium phosphate can be liberated by adding organic matter and this explains the higher P₂O₅ content in calcareous or mollic brown soils. However, the P₂O₅ content always remains rather low.

Phosphate requirements are high and it is recommended that the fertilizer be applied in doses, the least soluble fertilizer in the autumn and the most soluble (e.g. super phosphates) at the end of the winter.

7.7.4 Organic fertilization

Ferro-siallitic soils have an organic matter content of less than 2%, The addition of organic matter in the form of green fertilizers or manure is beneficial, not only on the structure of the soil, but also on the solubilization of the phosphates and of the obligo elements, such as boron.

7.8. Deficiencies and Chlorotic Power

Since many of the soils of Cyrenaica have a pH of 8 magnesium, phosphorus and boron are made less soluble or insoluble.

The consequences can be deficiency diseases and the frequent appearance of chlorosis. The reaction of the plants appears to reflect the chlorotic power of the soil better than its active limestone content.

In fact, the pH is not the cause, but the indication of a set of conditions.

Chlorosis is manifested by the yellowing of the leaves of plants which begin to wilt. Iron can no longer be absorbed by the plant for reasons related to the nature of the soil.

Crops which are not highly sensitive to chlorosis should be chosen or if plants show signs of chlorosis they should be treated by spraying with ferro or ferro-silixic complexes of the EDTA type.

7.9. Erosion

The soils of Cyrenaica and, in particular, those which are located in Jebel el Akhdar, are subject to erosion owing to the uneven relief and the nature of the rainfall.

Sheet erosion is evident on the gentler slopes (beginning at 1%) when the soil is bare and gully erosion on slopes (beginning at 3%) void of vegetation or cleared. Therefore, in order to prevent erosion, it is essential that clearing should be carried out with caution.

It is also recommended that the natural vegetation between the cleared parcels should be maintained in order to create a wooded landscape with woody slopes intended to slow down erosion and to serve as windbreaks.

8. Pakistan

8.1 Introduction

West Pakistan lies between latitudes 23° and 37° north and longitudes 61° and 76° east. Its total area is about 810 000 km and population about 60 million. There are three main physiographic units: (i) the mountainous area, (ii) the Indus plains and (iii) the Thar desert. The mountainous area covers more than two-thirds of the country on the northern and western sides. The Indus plains extend over an area of about 207 000 km² whereas the Thar desert, which is a vast region of sand ridges, covers about 65 000 km².

8.2. Climate

The major part of West Pakistan has an arid or semi-arid subtropical continental climate. Only a small region in the north-east has a sub humid climate where the rainfall is 500 to 1 000 mm The rainfall decreases rapidly toward the south-west with the result that two thirds of the country gets less than 200 mm. About 70 percent of the total rain falls as heavy downpours in summer, mainly in July, August and September. The remaining 30 percent occurs in winter as gentle showers of long duration. The proportion of winter rain increases in the north-western parts of the country. Hilly areas higher than 2 000 m in the north and west have snow in winter.

Except in high areas (more than 2 000 m altitude) the summer is very hot, with a maximum temperature of more than 40° C. May and June are the hottest months when the maximum temperature may rise to 45 C; the central part of the Indus plains is the hottest region in the whole of the Indo-Pakistan subcontinent. The winter is mild with maximum temperatures around 20° C and minimum a few degrees above freezing. In the hilly areas summers are mild and winters are severe.

8.3. Landforms and Parent Materials

The main landforms and soil parent materials of West Pakistan are listed in the following table and are shown in Map I.

Landforms	Soil parent materials
1. Mountains	Rock, residual material and local colluvium
2. Piedmont plains and terrace remnants	Subrecent and some old gravelly and loamy to clayey piedmont alluvium
3. Dissected old loess and alluvial terraces	Loess, residual material, old river alluvium and Subrecent out wash
4. Rolling sand plains	Pleistocene and Subrecent wind-reworked sands
5. Old river terraces	Pleistocene, mainly silty river alluvium
6. Subrecent river plains	Subrecent silty and clayey river alluvium
7. Indus delta	Subrecent and some Recent silty and .clayey estuary alluvium with some clayey coastal alluvium
8. Active and Recent river plains	Recent and some Subrecent silty and sandy river alluvium

MAP I

Each landform is briefly described below:

8.3.1 Mountains

This mapping unit occurs over a large area in the western and northern parts of West Pakistan. The whole area has been subjected to folding, faulting and uplifting as a result of compression between two stable land masses - one in the north in China and the other in the south in India. During the Mesozoic and Tertiary periods, almost the whole of Nest Pakistan was part of a great depression forming an extensive sea which received sediments from the rising hill ranges in northern Afghanistan and along the northern borders of Pakistan and India. The western and northern strips of this sea area in Vest Pakistan received mainly sandy, calcareous, near-shore sediments. The central strip received mainly silty and clayey sediments with lime, and deposits of dark-coloured (near-surface) and reef limestones. The south eastern strip is mainly massive or bedded white limestones, indicating deposition far from the source of continental sediments. At different times during the folding, igneous material was injected into the centre of the folded areas, giving rise to the mainly granitic core of the Himalayas and spots of volcanic rocks of different ages.

During the Tertiary, the compression of this area continued, causing folding and uplifting of progressively more southerly and younger sedimentary rocks. Some folding and faulting continued during the early Pleistocene. As a result, all the area formed mountain ranges and only the present Indus plains remained under sea.

The mountains have steep slopes covered with scree or colluvial material on their lower parts. The main rocks are limestones and calcareous shales and sandstones. In humid areas in the north the valleys are 'V shaped as the rivers and streams are still engaged in active down-cutting. In the arid parts in the west the valleys are filled with alluvium. Hard limestones weather slowly and yield little material. Therefore, much of their surface is bare rock, except for some material in depressions and crevices. Sandstone and shale mountains have much less exposed rock and a much higher proportion of scree and colluvium.

It is worth noting that although the rocks and the structure of the mountains are mainly Tertiary or older, the land surface and the soils are generally Holocene, part Pleistocene, due to continued erosion.

8.3.2 Piedmont plains and terrace remnants

This mapping unit occurs in the western mountainous area of West Pakistan and consists of three main elements: loamy and silty, very gently sloping plains; clayey, part strongly saline basins; and stony, sloping fans and valley margins. In many places there are remnants of the same main elements from an earlier cycle of deposition, occurring as generally stony terraces. All the materials are strongly calcareous.

8.3.3 Dissected old loess, residuum and alluvial terraces

This mapping unit comprises the Potwar uplands: a vast area of deeply dissected loess and alluvial terraces with Subrecent outwash and residual material outcropping in ridges or valley bottoms or occurring as broad interfluves. A small area in the northern part of Peshawar Tale has a similar, but less complete landscape of loess and alluvial terraces. Ob the map, this could not be shown due to its small extent. The same is the case with small patches of loess in some other places. Loess is among the oldest of the main soil-forming sediments recognized in West Pakistan. In the Potwar uplands it forms a vast, deeply dissected sheet which may overlie older alluvium, locally older loess or piedmont or, unconformably, mainly steeply dipping Tertiary rocks. The loess is estimated to have been deposited in the main, coldest, period of the last glaciation - say, some 50 000 to some 20 000 years ago. As in other loess areas of the world, except for the most arid parts, the material appears to have been blown out of broad, sandy river beds and river plains downstream (the area of the present Indus plains).

8.3.4 Rolling sand plains

Wind-reworked sands occupy a considerable part of West Pakistan. The main area is the desert of Cholistan and Thar, a band about 80 km wide, over a distance of some 805 km in the southeast, along the Indian border. This forms the western margins of the Rajputana desert of India. The origin of the sands is not certain. They are most probably older than the last Glacial period, in view of their elevation far above the probably levels of the Indus and Sutlej courses in the late Pleistocene. The landscape consists of mainly stabilized hilly sand plain, with longitudinal ridges in the south but alveolar (honeycombed) and transverse ridges in the northern part. The sands are calcareous, rich in weatherable minerals and typically yellowish or pale brown. They contain less mica but more quartz than the sands of the Indus river and its tributaries.

In the north, the sandy area of Thal, between the Indus and Jhelum rivers, is an old Indus terrace deposited in the later part of the last Glacial period. The sand ridges are longitudinal, transverse and alveolar, which are stabilized with vegetation.

The western areas of wind-resorted sands are also of alluvial origin: sandy piedmont slopes, probably of Holocene and partly of late Pleistocene age. In the arid climate of this part of West Pakistan, soil development is virtually nil, the vegetation covers less than some two percent of the total area and reworking by wind is continuing.

8.3.5 Pleistocene river terraces

During the main part of the last glaciation, shallow seasonal surface thawing in the permanently frozen uplands liberated large amounts of sand from Tertiary and Pleistocene sandstones, and the sandy material was deposited probably all over the present Indus plains, but at present, the sandy terrace base is at the surface only north-east of a line running northwest of Lahore. Further southwest it is buried under deposits of the later part of the last glaciation when the permafrost in the uplands and Himalayan foothills disappeared and enormous quantities of unconsolidated sediment, mainly loess and some old silty and sandy alluvium, were removed from there by deep and widespread dissection. This mainly silty material was deposited on the sandy terrace base. Its thickness increases from very thin near Lahore to more than 7.6 m near Multan. The surface of this deposit is now some 6 m above the present river plains in the north-eastern part and merges with the river plain near Multan. Further downstream it is presumably buried under increasing depths of later sediment.

During the early Holocene, wide plains were cut by the rivers in the old sediments along their courses, so that steep-edged Pleistocene river terraces now remain in the centre between each pair of rivers.

8.3.6 Subrecent river plains

Covering the Indus and tributary river plains, this mapping unit mainly consists of silty levees, clayey basins and sandy meander bars with a silty cover of varying thickness.

During the early Holocene, a somewhat warmer and more humid climate than the pre-sent caused a denser vegetation in the Himalayan foothills and uplands, with consequently less erosion and larger, more constant, river flows with less sediment load. The Pleistocene river deposits in the upper Indus plains were dissected, producing the broad Holocene river plains between the remaining strips of old terraces. The depth of dissection in the north-eastern part of the Vest Pakistan plains was of the order of 6-9 m, diminishing downstream due to the difference in gradient. Near Multan, the Old and Sub-recent river plains are at about the same level, and further south-west the Subrecent river plain was built up over the late Pleistocene level, due to the rise in sea level and the sediment added to the rivers by the dissection upstream.

During the middle and late Holocene, the sea level remained constant and the climate was much like the present, with less rainfall than during the early Holocene. Some decrease in vegetative cover in the uplands due to the decreased rainfall brought about a slight increase in erosion and increased seasonal changes in river flow. This is probably the cause of the presence, even in the northern Indus plain, of large areas of double storey soil profiles, in which soil formation was interrupted by accretion of some 0.6 -0.9 m of new sediment and followed by soil formation mainly in the younger sediment. In the lower Indus plain, vertical accretion continued, but at a slower rate than during the early Holocene, and with periods of soil formation in areas where the river was not currently depositing sediments.

8.3.7 Indus delta

The estuary plain differs from the river plain in four main characteristics. Its gradient is considerably smaller; it contains a large proportion of extensive, level, silty spill flats; it has a different degree and kind of salinity; and the river channels in the natural landscape are distributaries influenced by sea tides.

The main part of the estuary plain consists of very extensive, level, saline, silty spill flats and level, part saline and part nonsaline, clayey basins and channel infills. Narrow, nonsaline silty levees, which overlie the estuary material, extend along some Indus distributary channels far into the delta from the boundary of the river plain.

The coastal fringe mainly consists of extensive, strongly saline, silty clay tidal flats with some narrow, slightly higher, strongly saline, silty tidal ridges.

8.3.8 Active and Recent river plains

The Active and Recent Indus floodplain in the northern half mainly consists of sandy bars and levees with gentle slopes away from the multiple and relatively shallow river courses. Locally, small areas have a shallow clayey or silty cover which is nearly level. The Active and Recent floodplains of the eastern tributaries generally have a large proportion of nearly level, shallow to moderately deep, silty covers and a smaller area of uncovered sandy meander bars and levees. The Indus course in the southern half Is intermediate between these two conditions.

8.4. Calcareous Soils

Calcareous soils of Nest Pakistan have been broadly grouped into four classes as shown in Map 2 and are described below.

8.4.1 Moderately calcareous soils of the Indus Plains

These soils cover almost the whole of the Indus Plains (about 200 000 km²) which form about one fourth of the total area of West Pakistan. They have formed in calcareous alluvial material which is derived from the calcareous rocks of the Himalayas and deposited by the Indus river and its tributaries. The alluvium is moderately calcareous when it is deposited, and contains about 8 to 12 percent lime. The climate is arid or semi-arid and, therefore, little leaching takes place. Moreover, the soil formation has taken place concurrently with deposition of new alluvial material. This has also maintained the original calcium carbonate content of the soils. The lime is present mostly as silt size particles, very little lime being present in clay size or sand size.

The soils show structural development, with angular or subangular blocky structure, accompanied by accumulation of well humified organic matter, down to about 100 cm depth. The original fine stratifications which are characteristics of fresh alluvial deposits, have disappeared during structural development and homogenization.

A part of these soils In the northern Indus Plains are developed on Late Pleistocene river terraces and show a lime profile with a zone of lime accumulation. The climate of this part is semi-arid and some leaching of lime has taken place, so that the soil up to about 120 cm contains only 5 to 8 percent lime and is underlain by a zone of lime accumulation which contains about 15 to 20 percent lime both as fine particles and lime nodules. Only in very snail patches the zone of lime accumulation starts within 50 cm of the surface.

MAP 2 WEST PAKISTAN CALCAREOUS SOILS

The greater part of the area of these soils in the central and southern part of the Indus plains are formed in Subrecent deposits. These soils contain lime evenly distributed throughout the soil profile. There are some fine lime concretions in some soils but they occur throughout the subsoil and do not form any zone of lime accumulation.

The texture of these soils is mostly loamy (silt loams, loams and silty clay loams) and clayey; the proportion of the latter increase in the southern part of the Indus plains. The content of organic matter, present in well humified form, varies between 0.4 and 0.7 percent, and the pH of the soil is about 8.2. The exchangeable sodium is high only in a comparatively small part of the total area but locally quite important.

These soils form the most important agricultural land of Vest Pakistan and are very productive for a wide variety of crops. The presence of calcium carbonate in these soils poses only minor problems of plant nutrition, as for instance the availability of phosphate, iron, manganese etc. Probably the presence of well humified organic matter (0.4 to 0.7 percent in the soil profile down to about 100 cm depth) helps to overcome the harmful effects of calcium and magnesium carbonates and the problem does not become accute. Farmyard manure added to the soil by farmers once in three or four years also helps to overcome the harmful effects of calcium carbonate to a considerable extent. Vegetables and fruit orchards are given farmyard manure in quite heavy doses. This practice helps to control deficiencies of minor elements and phosphate. Vegetables and fruit trees planted in new areas sometimes show symptoms of deficiencies of minor elements but these generally disappear after a few years of farmyard manure applications.

With the increasing use of nitrogen fertilizers, deficiencies of phosphate have become pronounced during the last few years, effecting especially pulses and other legumes as well as tuber crops like potatoes and sweet potatoes. The farmers have reduced the area under these crops.

It seems that in the fertilizer programmes of such soils addition of organic matter is essential, especially for vegetables and fruit trees. For field crops the use of artificial fertilizers is generally helpful in producing enough root material to raise organic matter content of soil, and if a part of the plant residue (like wheat straw) is also buried in the soil and some nitrogen is added to encourage its decomposition, it is very useful. Some progressive farmers have already adopted this very practice.

Only in small areas, where the zone of lime accumulation is within 100 cm, fruit trees do not grow well, as the lime zone is massive and probably contains a high proportion of active lime. The lime concretions also act as a mechanical hinderance to root development.

8.4.2 Strongly calcareous soils of the intermountain valleys

Covering about 62 000 km² in the western hilly area of West Pakistan, these soils occupy valleys and basins. They are formed in alluvial deposits derived from limestone and calcareous shales and sandstones as well as loess. The deposits have a piedmont character. Typically, gravelly materials occur near the mountains and form borders of the valleys and basins. Next to the gravelly deposits there are loamy or silty deposits and in the lowest parts there are clayey deposits. Generally, the loamy deposits are most extensive and form important agricultural soils. The soils are strongly calcareous and contain about 20 percent carbonates of calcium and magnesium, mostly as silt-size particles. As the climate is arid or semi-arid, no leaching of lime has taken place.

The soil formation processes are limited to homogenization and weak structural development.

Organic matter present in well humified forms is very low, generally 0.4 to 0.5 percent.

The greater part of these soils is used for grazing sheep, goats and camels. Only a small part is cultivated with irrigation from groundwater which is usually present in the gravelly deposits on valley margins. The water is taken through underground tunnels which are made by connecting series of wells. Plowing by gravity the water appears at the surface on the loamy part of the valleys. The water tunnels are called 'karezes' which are analogous to 'ghanats' in Iran and 'phagaras' in Iraq and Jordan. A variety of crops and fruits is grown under irrigation. Addition of farmyard manure consisting of dung of sheep, goats and cattle is a standard practice for fruit orchards and vegetables. Newly planted fruit trees often show chlorosis, the sign of iron, manganese and zinc deficiencies, but it is seldom seen in older orchards which receive regular applications of organic manures. Field crops like wheat, alfalfa, melons etc., which receive occasional applications of farmyard manure, grow quite well.

Parts of these soils are used for growing wheat, sorghum and melons with torrent flood waters. The fields are made with high embankments and are soaked with a deep irrigation whenever torrent water is available. Since the success of the crop depends upon the moisture in the soil, fertility is not a problem and no manuring is done.

8.4.3 Moderately and strongly calcareous soils of loess deposits

Loess deposits occur in the northern part of the Indus Plain and cover about 13 000 km². The deposit pertains to the last glaciation period and is strongly calcareous, containing about 20 percent carbonates of calcium and magnesium. Soil formation took place during the Early Holocene but at the same time large-scale erosion occurred, so that only a very small part of the area has fully developed soils which have escaped erosion. The fully developed soils are non-calcareous with clayey or clay loam B horizons and loamy surface soil. Most of the area is, however, occupied by a soil which has developed on an erosional surface and has a thin B horizon with weak or moderate structure. The erosional surface comprises the zone of lime accumulation of the original soil. The soil is moderately calcareous to about 30 to 50 cm, but strongly calcareous below and also contains concretions of lime.

The other important soil consists of massive loess material in its original form and is strongly calcareous, with about 20 percent lime.

The two soils occur in an association which comprises gently to moderately sloping areas of the moderately calcareous soil in high parts and massive loess soil in dissected, low areas. The association also includes areas of gullied land and bad land.

Both of the important soils occur in a subhumid and semi-arid climate with mean annual rainfall ranging between 400 mm and 1 000 am. They are used mainly for growing rainfed wheat and sorghum. The crops show quite good response to a combination of nitrogen and phosphate fertilizers. Comparative study of the fertility problems of the two soils has not been made.

8.4.4 Strongly calcareous lithosols of mountainous areas

These soils cover about 310 000 km² in mountainous areas of West Pakistan. The main rooks are limestones of various kinds and some calcareous sandstones and shales. The greater part of the area consists of steep slopes of bare rocks, whereas the remaining area has very shallow soils which are strongly calcareous. These soils occur in an arid and semi-arid climate. The sparse vegetation on them is used for grazing. As the main problems of these soils are very shallow depth and steep slopes, the high lime content is not so important a limitation.

8.5. Other Soils

The uncoloured areas in the map have either non-calcareous soils or sandy soils The non-calcareous soils occur in the northern parts of the country while the sandy soils occupy areas of rolling sand plains in the south and west.

9. Qatar

9.1. Introduction

Soils in Qatar have not been studied. The area of Qatar State is about 1 million hectares.

The agricultural area is about 6 000 ha (0.52% of the country), and vegetables are the main product. Agriculture depends entirely on water from shallow wells. The possibility of expanding the agricultural area is limited by the available water resources and the lack of potentially productive land. Land productivity classifications show that Qatar soil can be considered of low productivity, due to the poor quality of the soils and water.

Qatar soils are classified generally as calcareous and these are problem soils as far as agriculture is concerned, which in turn may affect the agricultural economy of the country.

Qatar has been classified as arid region, where all agriculture depends on irrigation from groundwater. Some 1 300 shallow wells already exist. An area of groundwater (total dissolved salts 1 000 - 2 000 ppm, mostly of NaCl) exists in the central part of the Qatar peninsula and seems to be continuous in all parts of north Qatar. In the centre and south of Qatar, a good fresh water (T.D.S. up to 3 000 ppm) exists, but with equal amounts of chloride and sulphates and seems in most cases to be not interconnected. Usually the groundwater is from 3 to 20 metres below ground surface in North and Central Qatar. In the South, water may be as much as fifty metres below ground surface. Most of this water is used for agriculture and some of it is used for municipal purposes after it has been mixed with distilled water from the sea.

9.2. Distribution and Nature of Calcareous Soils in Qatar

The majority of calcareous soils in Qatar State are located in depressions formed from colluvium materials sedimented by the seasonal rainfall runoff on rocky limestone strata (bedrock), which is dominant in Qatar. These depressions are scattered along the Qatar peninsula forming oases in the desert.

In northern and central Qatar, calcareous soils are dominant in these depressions. In the south, calcareous sandy clay to calcareous sandy loam are the dominant soils, as they are also in the south-west of Qatar where a few sandy wadies have been formed by the transportation of desert sands. In the south-east of Qatar, sand dunes and sandy hills are formed on a rocky surface.

Salt affected calcareous and sandy soils are located adjacent to the Gulf shore and represent 6.04% of the Qatar peninsula area.

Calcareous soils mainly have high calcium carbonate, silt and clay contents with a moderately slow infiltration rate such as in colluvium depressions which are characterised by a limited soil depth overlying the bedrock, with low salinity. The thickness of the colluvium sediments in depressions provide a potential for the use of these soils. The dominant salts in these depressions are generally soluble calcium, magnesium and sulphates, with a low content of total soluble salts.

Saline soils are characterised by a high sodium chloride content, a saline water table and are adjacent to the sea.

The salt affected calcareous soils, of secondary origin in Qatar, are mostly in the present cultivated area. The deterioration of these soils is mainly attributed to the saline well waters used in irrigation and the misuse of irrigation water over the years, together with the lack of drainage system and soil management practices.

Qatar soils are characterised by low fertility, due to the arid climatic conditions.

9.3. UNDP/FAO Project - Hydro-Agricultural Resources Survey

Co-operation between the Government of Qatar and FAO on the project to study water and land resources, which was begun in 1970, will have valuable results on water availability and soil resources. That project includes the following:

(i) A reconnaissance soil survey and land classification with the production of three maps: soil classification, land classification and potentialities, and soil index map, all at scale 1:100 000.

It has been interpreted that Qatar State can add about 26.4 thousand ha (2.4% of its area) for agricultural utilization, provided that water is available.

(ii) The study of water quality and resources, in order to assess agricultural extension in the future programme.

No study on soil capabilities had been conducted in Qatar prior to the present hydro-agricultural surveys project. The problems could be stated as follows:

(a) The domination of calcareous soils in Qatar, plus limited soil profile depth over the bedrock.

(b) The high content of CaCO₃ and magnesium carbonate in the soil.

(c) Soil compaction and low water penetration

(d) Inefficient soil management and low soil productivity

(e) The dominant arid climatic condition

(f) Limited irrigation water depending on season rainfall run-off where it is recharged by shallow wells and with moderate to high salinity contents

(g) Inefficient irrigation practices

(h) Low fertility

(i) Desalinisation of the present cultivated area.

(i) Interpretation of the area of arable soil available in the whole of the Qatar peninsula; chemical and physical characteristics of calcareous soils, their diagnosis, reclamation and management were delineated.

(ii) Infiltration rate measurements were carried out on Qatar soils in the field by using an infiltrometer with one cylinder.

(iii) A detailed soil survey and land classification of Qatar Government Farm was carried out in order to specify the major problems and delineate a specific programme on soil management and soil amelioration on the cultivated calcareous affected soils.

(iv) A water survey was conducted by the hydrological section of the Project on water resources and availability,

There has been no land reclamation and improvement except to a limited extent in some agricultural areas, where 30 cm of top soil have been transferred to cover the rock fragments for vegetable cultivation.

9.6. Recommendations

1. The study of Qatar soils should be encouraged, physically and chemically, and the establishment of the new soils laboratory which was essential and .has now been completed must be supported.

2. The very detailed soil study on the present cultivated land, as well as a detailed survey on the potential arable land prior to its cultivation should be completed.

3. Work on soil conservation and erosion should be supported and a study carried out on forestry cultivation on saline sandy soils with particular attention being paid to the water table.

4. Benefits would be gained if a feasibility would be carried out on reclaiming saline soils where irrigation water is available.

5. The establishment of a regional research programme on reclaiming calcareous soils is necessary and would be of great benefit to the country.

6. Improvement of irrigation practices in Qatar State is necessary and measures to ensure this should be encouraged.

10. Saudi Arabia

10.1. Introduction

The Kingdom of Saudi Arabia has a total area of about 225 million hectares and of this area just over 0.1 percent is under cultivation. The Government intends to double the present area under cultivation in the next 15 years, through survey and evaluation of land and water resources.

The variation in the soil forming factors prevailing in the country results in the existence of different soil types. Aridity and a hot climate, lack of water and wind erosion affect the degree of soil formation. Concerning chemical weathering of the soils, it proceeds at a slow rate owing to the absence of much rainfall and the soils therefore tend to be salty for the soluble products are not washed away. Less soluble salts such as gypsum and CaCO₃ exist in some soils in a considerable percentage. Generally, the organic matter content is essentially low, below 1%, as is also that of nitrogen. The available phosphate is generally low and because of insufficient leaching potassium content is high.

Two agricultural areas of Saudi Arabia are used as examples since there is some available information, although the country has many agricultural areas with different soil types already surveyed or under survey. These two areas are Qatif, which is situated on the coast of the Arabian Gulf, and Al-Hasa which is about 160 km from Qatif in a south-west direction.

10.2. Climate

Data recorded during the years 1964-69 in Qatif Experimental Farm showed that:

- temperature ranged from 10° C in winter to 43° C in summer as mean monthly data
- monthly recorded rainfall data ranged from 1.9 mm in 1966 to 122 mm in 1968.

In a soil profile at Qatif the parent materials of the soils show a great variation resulting in rather large differences in the soil profile. Influencing phenomena are (Soil Survey 1963):

- limestone and marl formation and their erosion products
- aeolian desert sand
- tidal sediments of the sea

The consequences of the occurrence of this hardpan were thought to be that the root development of crops might seriously be hampered and that the drainage profile might be restricted owing to its limited permeability.

When these soils were reclaimed, the hardpan gradually dissolved and its detrimental effect was strongly reduced within a two year period. The material overlying the calcareous hardpan is generally sand, but in places layers of even, silty clay and all possible transitions are found. The material below the hardpan .varies to a great extent. Coarse-textured materials, however, exists in all profiles.

The variations occur at very short mutual distances and at different depths, consequently the area can be considered heterogeneous with very light-textured soils.

For illustrative purposes, a review is given hereunder of a typical soil profile as far as texture is concerned:

0 - 15 cm	loamy sand
15 - 40 cm	medium coarse sand
40 - 60 cm	loam
60 - 85 cm	loamy sand
85 - 120 cm	coarse sand

Below the calcareous hardpan, an impervious layer is found at a depth of 2 metres in places.

10.4. Soil Salinity

From observations made during the soil survey (ILACO 1963) it was established that the soils were strongly saline. The content of easy soluble salts ranged from 0.5-4% Determination of the electrical conductivity of the saturated extract before leaching resulted in average values of 23.5 mmhos/cm at 25°C at a depth of 0.15 cm and 17.0 mmhos/cm at a depth of 0.50 m. Next to the easily soluble salts there existed a considerable amount of less soluble salts, mainly consisting of gypsum to a minor degree of CaCO₃. The content of gypsum and CaCO₃ together, as found in the sample analysed, ranged from 30-40% of the total soil mass.

The Soil Survey also showed that pH values were found to range from 7.2 to 8.2.

10.5. Irrigation and Drainage

The area is supplied with water from artesian wells. There is a drainage system constructed by the Government throughout the Qatif area.

10.6. Quality of Irrigation Water

The analytical data available on the water to be used for irrigation revealed that most artesian wells supplied water with EC values of 2.8-4 mmhos/cm.. This quality class of water is not suitable under ordinary conditions, but may be under special circumstances, such as permeable soils or adequate drainage. Water must be applied in excess to provide considerable leaching and very salt tolerant crops should be selected.

Data of the chemical properties of the irrigation water are given in the following table (Analysis by ARAMCO)

ION	PPM
Na	344
K	20
Ca	195
Mg	76
SO4	451
Cl	625
HCO3	195
Total	1 886 = approx EC = 2.9 mmhos/cm
SAR approx = 6

10.7. Land Reclamation

Soil reclamation is toy leaching in order to minimize to a level suitable for plant growth the soil total content of soluble salts. The following technique is used.

The first water application is used to soften the soil, then the salt encrusted surface is broken up and pulverized; this improves the topsoil permeability and leaching. The operation was carried out with a heavy tractor-mounted cultivator with rigid, deep-digging shanks, equipped with sharp, narrow shovel points acting like a ripping plough.

The breaking up of salt crusts and hardpan, where feasible, should be repeated as many times as possible at gradually increasing depths. The use of a plough, whether disc or mouldboard for this work should be avoided since this implement turns the soil over, thus bringing to the surface again all the salts that have been washed down.

During and after these mechanical soil improvement activities, pre-sowing water applications should be given to leach out salts.

The usual procedures for full reclamation of the soil are leaching followed by growing barley, ploughing this crop under and then keeping the area under alfalfa for one season or else a heavy application of farmyard manure is given immediately after the initial leaching period.

The results obtained during the last few years have proved that the organic matter is essential in the production of vegetables in this particular soil. Moreover, the results indicate that chemical fertilizers are more efficient if they are combined with an adequate addition of farmyard manure applied prior to sowing or planting of the crop.

There exists an insignificant difference between the effect of combined and single fertilizers on the yield. Phosphate is essential for attaining high yields, whereas potassium was not, probably because an adequate quantity of this element is supplied by the irrigation water in addition to its soil content.

There are two experimental stations in the eastern province of the country, one at Qatif and the other at Al-Hasa. Qatif station concentrates its research mainly on horticulture, whereas the Al-Hasa station does research on both animal production and forage crops. Al-Hasa soils are similar to Qatif's in texture hut have less salinity and CaCO₃. The Al-Hasa area is irrigated mostly from springs that are combined in one vast irrigation system, the largest irrigation project in the country that is designed to cover 20 thousand hectares. Research on saline and calcareous soils of Al-Hasa is still in progress with the assistance of both Leicht Weiss Institute of West Germany and the University of North Wales of Great Britain.

In the Qatif station, a research programme is run mainly on vegetables, industrial crops, some fruit trees, forage crops, weed control and date palm trees. Experiments on these crops include fertilizer trials, variety selection and date of planting.

11. Somali Democratic Republic

11.1. Introduction

The climate of Somalia is arid and semi-arid with two rainy seasons. The annual rainfall and distribution fluctuate from year to year, for example in the Afgoi district the annual rainfall in 1970 was about 400 mm but in 1972 it was over 800 mm.

Somalia has 10 million ha of arable land, 2 million ha of which lie in the inter riverine area. Of the cultivable land 500 000 ha are under cultivation of which 400 000 ha are dry farmed, 80 000 ha are flood irrigated and 20 000 ha are regularly irrigated.

11.2. Soils

A major portion of the Somali soils are calcareous, but the agricultural areas are not highly so. Out of 800 samples collected from widely scattered areas along the Wadi Shebelli and the Giuba Valleys, 30% contained less than 10% calcium carbonate, 31% contained from 10-20% and 39% contained from 20-30%, The pH of these samples was from 7.2 to 8.2 with 8.0 being the predominant value.

11.3. Nutrient Status

The data in the following table shows the results of maize nutrient requirement studies on calcareous soils being done at the Central Agricultural Research Station at Afgoi.

The objectives of the experiment are to determines

(i) which elements are deficient in the soil
(ii) the fertilizer requirement of maize
(iii) the response of maize to fertilizer under irrigated conditions
(iv) the correlations between soil test and yield at the end of the experiment (which is still continuing). The average calcium carbonate of this soil is 21%.

Nutrient requirements of maize grown on calcareous soils

GU Season: April-June 1971		Deir Season: October-December 1971
Treatment N - P - K	Average yield 100 kg/ha	Treatment N - P - K	Average yield 100 kg/ha
0 - 0 - 0	18.9	0 - 0 - 0	13.8
0 - 50 - 0	22.7	0 - 50 - 0	13.2
0 - 100 - 0	21.4	0 - 100 - 0	13.3
50 - 0 - 0	30.6	50 - 0 - 0	23.6
50 - 50 - 0	39.6	50 - 50 - 0	22.8
50 - 100 - 0	36.3	50 - 100 - 0	21.2
100 - 0 - 0	38.9	100 - 0 - 0	20.4
100 - 50 - 0	38.5	100 - 50 - 0	30.4
100 - 100 - 0	40.2	150 - 0 - 0	27.9
150 - 0 - 0	40.8	150 - 50 - 0	30.6
150 - 50 - 0	34.2	150 - 100 - 0	32.7
150 - 100 - 0	35.9	100 - 100 - 0	30.0

Number of replications: 4
Rotation: maize after maize
Fertilizer used: Urea and triple superphosphate in kg/ha

Electrical conductivity of these soils ranges from 10 - 220 mmhos/cm. Reasons for this high salinity are:

(i) high salt content in irrigation water
(ii) excess use of irrigation water
(iii) lack of proper drainage.

The Johar Estate poses the main soil problem in Somalia at present and shows what will happen to other calcareous but not highly saline soils if they are farmed under similar conditions as at Johar.

Recently, the following experiment has been proposed:

Treatment	Gypsum	Water
	kg/m2	litre/m2
1	0	120
2	0	180
3	0	240
4	1	120
5	1	180
6	1	240
7	2	120
8	2	180
9	2	240

Concerning drainage, deep canals are made along the plots to take away extra water.

12. Sudan

12.1. Introduction

The Sudan is a country with vast land resources. Due to shortage of capital, the national priority in agricultural development has been directed primarily towards areas where the possibility of bringing land under cultivation was low.

The problem of land reclamation for agricultural development was never tackled seriously until recently. Reclamation projects are now being considered for two areas: the Northern Province, and areas around Khartoum, which together amount to about 200 thousand ha (500 000 feddans). The need to reclaim soils in the Northern Province was dictated mainly by the favourable conditions for the production of horticultural crops. Initiation of reclamation projects in lands around Khartoum was justified by the high demand for horticultural, dairy and poultry products.

12.2. Calcareous Soils in the Sudan

Calcareous sediments in the form of limestone as soil parent material do not exist in the Sudan. The calcareous nature of the soils is a result of the precipitation of CaCO₃ under arid and semi-arid climatic conditions. Calcareous soils with diagnostic calcic horizons as defined in the 7th approximation (USDA System) have not so far been identified. The soils are classified as calcareous or non-calcareous on the basis of the presence or absence of CaCO₃, (field acid test) regardless of quantity or form.

12.3. Geographical Pattern of CaCO₃. Distribution

Under the arid conditions of Northern Sudan (rainfall less than 400 mm), CaCO₃, exists in a finely divided form incorporated with the mineral soil particles giving a calcareous matrix, together with soft powdery aggregates and hard concretions. Soils with a non-calcareous matrix to a depth of 150 cm, but with various forms of CaCO₃, concretions, occur in areas of 650 mm of rain and above.

In the dry region, the calcareous characteristic of the soil as described above is always associated with high soluble salts and gypsum deposits.

12.4. Levels of CaCO₃ Content

Calcium carbonate forms larger than 2 mm diameter in size are sieved off. CaCO₃, determination is made on the fine earth of less than 2 mm diameter. The content of such incorporated CaCO₃ in general, ranges between 3 and 13%. In most of the agriculturally productive land, the CaCO₃, content within 600 cm is above 5%.

The table below gives some data of two profiles from Khartoum area.

Profile	Depth	pH	%	EC	Non calcareous soil fractions-%				ESP
No.	cm	paste	CaCO3	se	C.S.	F.S.	Silt	Clay
1.	0 - 10	8.4	10.6	1.1	31	21	10	27	27.0
	10 - 35	8.5	11.1	2.4	26	18	12	32	50.0
	35 -55	8.3	10.9	6.7	22	17	14	36	50.0
	55 - 85	8.6	9.6	3.4	22	19	14	35	60.0
	85 -135	8.7	10.1	2.9	23	26	14	26	61.1
2.	0 - 35	8.6	7.0	13.4	19	17	18	39	45
	35 - 60	8.4	3.9	17.0	20	17	18	41	46
	60 - 90	8.8	4.4	12.6	19	17	18	42	44
	90 - 130	9.2	6.2	4.3	10	21	26	36	63

The data show that though the CaCO₃ content is around 10% in profile No. 1, yet the soil is adversely affected by the high content of sodium expressed in ESP.

Profile No. 2 shows a moderate CaCO₃, content of about 5%, and high Ec and ESP.

Both soils are more adversely affected by the presence of soluble salts and exchangeable sodium rather than by the presence of CaCO₃ which is mostly in an inactive form.

At present soil calcareousness does not seem to be a problem in the Sudan. Reactivation of the CaCO₃ under environmental conditions is needed to reduce the effect of soluble and exchangeable sodium cations. The main limitations of soils affected by calcareous characteristics are fine textures, slow permeability, associated with high salinity and salinity and sodicity.