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Crop agronomy research on Vertisols in the central highlands of Ethiopia: Jar's experience

Hailu Gebre

Holetta Research Centre Institute of Agricultural Research (JAR)
PO Box 2003, Addis Ababa, ETHIOPIA


Abstract
Introduction
Crops and production patterns
Review of research results
Future research
References


Abstract

Some results obtained from a series of experiments carried out on Ethiopian Vertisols at Sheno and Ginchi, two research stations of the Institute of Agricultural Research (IAR), are reported.

Barley is the major food crop around Sheno. Its production is associated with soil burning, or "guie", and long periods of fallowing. Fairly high yields are obtained in the first crop season after "guie", but yields decline quickly after the second crop season. The major crops around Ginchi are Teff (Eragrostis tef) and wheat. They are planted late in the main rainy season and yields are low.

Crop agronomy research has been conducted by IAR at Sheno and Ginchi since 1968 and 1974, respectively. The major objective was to replace the traditional practices of crop production with improved drainage, fertilizer and crop management techniques.

At Sheno, barley and wheat yields increased substantially when grown on 4-6 m wide cambered beds with the application of 60/26 (N/P) kg ha-1. Fertilizer was more efficient with wheat than with barley. Grain yields from continuous barley production under improved management fluctuated over the years.

At Ginchi wheat yields more than doubled with improved drainage and application of 60/20 (N/P) kg ha-1. Improved cultivars responded well to fertilizer application.

Introduction

Currently about 2 million ha of Vertisols are cropped annually in Ethiopia and some 6 million ha are left under native pasture because of severe drainage problems in the main rainy season (Jutzi et al, 1987). With the present trend of population growth in Ethiopia, estimated at 2.9%, there is a strong need for increased agricultural production which may be achieved by increasing productivity per unit area and/or opening new lands. Both options may be applied on Vertisols in the highlands.

Some of the major limitations for crop production on Vertisols are poor drainage, difficulty of seedbed preparation, and low soil fertility. In the high altitude areas the impact of low temperature complicates the soil problems. Traditionally farmers cope with these problems by late sowing of crops to mature on residual moisture, fallowing the land in the main rainy season, and soil burning, or "guie" (Berhanu Debele, 1985). Land that is ploughed early for late planting of crops is exposed to soil erosion due to high and intense rainfall, hence diminishing soil fertility.

The Institute of Agricultural Research (JAR) has been conducting agronomy research at Sheno, about 70 km north-east of Addis Ababa, since 1968 and at Ginchi, 85 km west of Addis Ababa, since 1974. Crop production patterns and the research experiences at these locations are reviewed in this report. It is possible to increase crop productivity on Vertisols through improved drainage, fertilizer and crop management (Hiruy Belayneh, 1986; Jamal Mohammed, 1985; Jutzi et al, 1987; Mesfin Abebe, 1979 and 1982; Taye Bekele, 1986).

Crops and production patterns

Sheno

Sheno is situated at an altitude of 2800 m, surrounded by a large highland plain. The soil has about 60% clay, a slightly acid pH, 0.2-0.3% total N and 7 ppm of available P (Mesfin Abebe, 1982). Annual rainfall is about 900 mm, with excess rain in July and August. "Guie" is extensively practised in the region. "Guie" plots are cropped to barley for 2-3 seasons and then left fallow for 10-20 years.

The predominant crop is barley with some faba beans, wheat, fieldpeas and oats, and lentils and linseed on a few hectares. Average yields of crops around Debts Birhan are 846 kg ha-1 for barley, 1295 kg ha-1 for faba bean, 964 kg ha for wheat, and 846 kg ha for fieldpeas (Gryseels and Anderson, 1983). Crop intensity is high on the hillsides and low on the bottomlands which are flooded during the main rainy season. Faba beans and wheat are mainly produced on the hillsides which have better drainage and less frost hazard; barley is produced on the flatter lands (Gryseels and Anderson, 1983). "Belg", or off-season barley, is mainly produced on bottomlands.

Tillage operations may start in September or October for "belg" season production and "guie" fields with repeated ploughings in the short rainy season. "Guie" fields are planted in June. Early sowing is practised for all crops except wheat, although barley may be sown in late June to escape aphid infestation.

Ginchi

The research site at Ginchi is at an altitude of 2200 m. Average annual rainfall is about 1080 mm of which about 65% falls between June and September. The soil is a heavy clay with 0.91-32% organic matter, 0.09-0.14% N and 4.2-9.9 ppm available P (Morton, 1977); the pH is about 6.4 (Hailu Kenno and Lulseged Gebre Hiwet, 1983).

The major food crops are teff (Eragrostis tef), wheat, niger seed and chickpeas. Sorghum, roughpea and barley also are grown to some extent. Estimates of yields of major crops are 500 kg ha-1 for teff and chickpeas, 600 kg ha-1 for wheat, and 300 kg ha-1 for niger seed (Agricultural Economics and Farming Systems Research Division, Survey date 1986).

The frequency of ploughing varies for crops: 3-4 times before planting for teff, 3 times for wheat and 1-2 times for pulses, niger seed and sorghum. Ploughing starts in March for cereals and niger seed; the first ploughing for pulses may be done in May. The small grains and pulses are sown late in the main rainy season and mature on residual moisture. Sorghum is sown in March or April and niger seed towards the end of May.

Pulse/cereal rotation is a common practice. Teff follows chickpeas in most cases, or roughpea and niger seed. Niger seed may follow sorghum for weed suppression.

Review of research results

Sheno site

The major objective for agronomy research was to replace the inefficient traditional practice of "guie" crop culture with improved drainage, fertilizer and crop management techniques for continuous crop production.

Barley grain yields of about 1.5 t ha-1 are obtained on "guie" fields in the first crop season (Taye Bekele, 1986). The high yield is due to improved soil structure and increased availability of ammonium-N and P; on the other hand, there is a high loss of organic matter and total N. with a detrimental consequence on the cation exchange capacity and microbial activity (Berhanu Debele, 1985; Mesfin Abebe, 1979 and 1982; Taye Bekele, 1986). "Guie" plots respond to fertilizer application and the efficiency is better than on regularly ploughed plots (Taye Bekele, 1986). Yields on "guie" plots decline dramatically after the second season of barley production (Taye Bekele, 1986; Mesfin Abebe, 1979).

In the early years, research on soil and fertilizer management was directed towards comparing the crop yields obtained from plots prepared by tractor-drawn ploughs (such as disc, mouldboard, and chisel) with those from narrow and wide cambered beds (prepared with mechanised operation), using different rates of application of N and P fertilizers. Narrow cambered beds gave higher yields at all N and P fertilizer application rates than the plots prepared by other methods. In 1970 about 2.5 t ha-1 of barley grain yield was obtained on a 6 m-wide cambered bed with application of 60/13 (N/P) kg ha-1 (Mesfin Abebe, 1979). Grain yields of barley, wheat and oats were also better on narrow cambered beds than on "guie" plots (Mesfin Abebe, 1979). Fertilizer efficiency was high on narrow cambered beds for barley and wheat.

The higher yield advantages of narrow cambered beds over local ploughed and mouldboard ploughed plots were further confirmed in later years on barley and wheat. The best yields of barely were obtained on cambered beds due to improved drainage (Table 1). However, efficiency of fertilizer with local barley was nearly similar on local ploughed and cambered beds (Mesfin Abebe, 1982; Taye Bekele, 1986). Fertilizer efficiency with wheat was much higher with improved drainage; wheat also responded better to additional P application than barley at a standard level of 60 kg N ha-1 (Table 2). Grain yields from continuous barley production fluctuated over the years; it was difficult to maintain stable yields even with improved drainage and optimum fertilizer application (Table 3). Rotation with pulses may be essential to sustain grain yields.

Ginchi site

In 1971 a testing site was established at Wollencomi, 74 km west of Addis Ababa, for research on drainage and fertilizer management and on the selection of high yielding crops and cultivars for early sowing on Vertisols. The Ginchi site, 11 km further west, was selected in 1974 as being a better representation of the surrounding area.

Table 1. Effects of seedbed preparation methods and N/P fertilizer application rates on mean grain yields of barley, Sheno, 1979-84.

Fertilizer rate (kg ha-1)
N/P

Grain yield (kg ha-1)a

LP

MP

CB

0/0

200

400

780

30/13

630

690

1200

60/26

870

1230

1670

90/40

1090

1410

1990

a LP: Local plough; MP: Mouldboard plough; CB: 6-m wide cambered beds.

Source: Taye Bekele (1986).

Table 2. Effects of seedbed preparation methods and N/P fertilizer application rates on grain yields of wheat and local barley, Sheno, 1976.

Fertilizer rate (kg ha-1)

Grain yield (kg ha-1)a

Wheat cv Enkoy

Barley cv Local Sheno

N/P

LP

MP

CB

LP

MP

CB

0/0

119

387

559

82

316

565

60/13

395

1267

1561

909

1277

1385

60/26

385

1318

1877

1055

1246

1598

60/40

657

1452

1995

1079

1194

1692

a. LP: Local plough; MP: Mouldboard plough; CB: 4-m wide cambered beds.

Source: Mesfin Aebe (1982).

From 1975-1977 different drainage system methods-cambered beds, open trenches, and subsurface trenches filled with wooden poles and branches at 4, 6 and 8 m intervals-were compared using improved and local varieties of wheat, teff and chickpeas at zero and optimum fertilizer levels.

Improved drainage had a significant effect on grain yields of crops, especially of wheat, whose yields increased by more than 100% compared to the yields from undrained plots; however, no significant differences in grain yields were observed between the various drainage methods (Table 4).

Table 3. Effects of seedbed preparation methods on grain yields of barley at optimum level of fertilizer application (60/26 (N/P) kg ha-1), Sheno, 1979-84.

Year

Grain yield (kg ha-1)a

LP

MP

CB

979

1510

1990

2490

1980

870

1940

2270

1981

470

410

700

1982

690

1470

2050

1983

300

520

850

1984

1350

1020

1650

mean

865

1225

1668

a. LP: Local plough; MP: Mouldboard plough;
CB: 6-m wide cambered beds.

Source: Taye Bekele (1986).

Fertilizer efficiency was highest with wheat with improved drainage; chickpeas responded poorly (Table 5). Among the wheat varieties, Enkoy gave the best response to fertilizers and improved drainage, yielding 1.8 t ha-1, while Bahir Seded yielded 0.65 t ha-1; there was no difference among the verities of teff or chickpeas (Hiruy Belayneh, 1986).

Results of sowing date studies on three cultivars of wheat (Enkoy, Cocorit 71 and Bahir Seded), covering the period from the end of June to the third week of August (Jamal Mohammed, 1985), showed no significant differences on 8-m wide cambered beds. Average grain yields were 2.1 t ha-1 on cambered beds and 1.3 t ha-1 on flat beds; improved drainage gave about a 70% yield increase over undrained plots. The yield of Enkoy, at 2.4 t ha-1 was significantly better than that of Cocorit 71 or Bahir Seded (2.1 and 1.9 t ha-1, respectively) on cambered beds.

Undersowing wheat with barrel medic, snail medic and lolium was found promising with wheat grain yields of 2-3 t ha-1 (which are comparable to sole cropping yield!), and dry matter forage yields of over 2 t ha-1 from the forage crops (Lulseged Gebre Hiwet et al, 1987).

The major direction in cereal breeding is to select high yielding, late maturing cultivars for sole cropping to utilise the whole growing season. Long season wheat cultivars giving about 3.2 t ha-1 are identified for Ginchi (Hailu Gebre Mariam and Bekele Geleta, 1985).

Table 4. Influence of drainage methods on grain yields of wheat, teff and chickpeas, Ginchi, 1975-77.

Drainage methods

Grain yield (kg ha-1)

Wheat

Teff

Chickpeas

Cambered bed

1150

1280

1250

Open trench

1150

1180

1200

Subsurface drain

1100

1000

1480

Control

520

940

870

Source: Hiruy Belayneh (1986).

Table 5. Influence of drainage and fertilizers on grain yields of wheat, teff and chickpeas, Ginchi, 1975-77.

Crops

Grain yields (kg ha-1)

Undraineda

Draineda

F0

F1

F0

F1

Wheat

360

670

720

1530

Teff

740

1140

840

1470

Chickpeas

850

900

1220

1400

a. FO: no fertilizer;
F1: 60/20 (N/P) kg ha-1 for wheat and teff,
27/30 (N/P) kg ha-1 for chickpeas.

Source: Hiruy Belayneh (1986).

Future research

Current research on Vertisols is being strengthened by collaborative work involving ILCA, ICRISAT (International Crops Research Institute for the Semi-Arid Tropics), JAR, the Agricultural University of Alemaya and the Ministry of Agriculture. The sharing of experience among the institutions helps to streamline research efforts. Applied agronomic research based on animal-drawn implements would have more relevance to the highly subsistence-oriented nature of crop production on highland Vertisols. For high altitude areas it may be worthwhile considering appropriate tillage methods, proper seeding and fertilizer application, and alternative cropping systems for small grain-based production.

Tillage

Timeliness of tillage with respect to soil moisture content is important to work the soil properly for effective control of weeds. The local plough is not effective for weed control, and better implements are needed. Reduced tillage with shallow cultivation and the use of glyphosphate for weed control may be important (Willcocks and Browning, 1986).

Proper seeding and fertilizer application

The wastage rate of fertilizers is high on Vertisols due to the broadcast method of sowing and denitrification due to waterlogging. Proper methods of seeding and method and time of application of fertilizers are important for efficient fertilizer use.

Cropping Systems

Crop productivity on Vertisols can be increased through early planting and improved surface drainage. Appropriate cropping systems are required for efficient use of the whole growing season. Some forage legumes are known to benefit food crop production by enhancing soil fertility when planted in association, or in rotation, with a major food crop. Most of the available information is relevant to maize and sorghum production in mid-altitude areas, such as Debre Zeit. In the higher areas, small grains are major food crops, so cropping systems based on such crops would be more appropriate. Some Vicia, Trifolium and Medicago species have high potential for sequential cropping with cereals. Some useful cropping systems may include forage legume-cereal sequences in the off-season and main rainy season, and cereal-pulse Sequences in the main season.

References

Berhanu Debele 1985. The Vertisols of Ethiopia: their properties, classification and management. In: Fifth Meeting of the Eastern African Sub-Committee for Soil Correlation and Land Evaluation. Wad Medani, Sudan. 5-10 December 1983. World Soil Resources Reports No. 56. FAO (Food and Agriculture Organization), Rome. pp. 31-54.

Gryseels G and Anderson F M. 1983. Research on farm and livestock productivity in the central Ethiopian highlands: Initial results, 1977-80. Research Report No. 4. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia.

Hailu Gebre Mariam and Bekele Geleta. 1985. An overview of the Ethiopian breadwheat breeding programme. Paper presented at the Workshop on Review of Field Crops Research in Ethiopia, Addis Ababa, 25 February 1 March, 1985.

Hailu Kenno and Lulseged Gebre Hiwet. 1983. Prospects of vetches (Vicia spp) as forage legumes for the highlands of Ethiopia. Ethiopian Journal of Agricultural Sciences 5:131-138.

Hiruy Belayneh. 1986. Drainage benefit for wheat, teff and chickpeas on heavy clay soil in central Ethiopia. Paper presented at the Workshop on the Review of Soil Science Research in Ethiopia, Addis Ababa, 11-14 February, 1986.

Jamal Mohammed. 1985. Effects of sowing dates and seedbed preparation methods on the yield of wheat. Ethiopian Journal of Agricultural Sciences 7(2):81-88.

Jutzi S C, Getachew Asamenew, Haque I, Abate Tedla and Abiye Astatke. 1987. Intermediate technology for increased food and feed production from deep black clay soils in the Ethiopian highlands. Paper presented at the FAO/SIDA Seminar on Increased Food Production through Low-Cost Food Crops Technology, Harare, Zimbabwe, 1-17 March 1987.

Lulseged Gebre Hiwet, Gebremedhin Hagos and Tadesse Tecle Tsadik. 1987. Undersowing of forage crops in cereals: some achievements. Paper presented at the First National Livestock Improvement Conference, Addis Ababa, Ethiopia, 4-6 February 1987.

Mesfin Abebe. 1979. Studies on soil fertility and drainage. In: Summary of Research Activities at Sheno Substation 1968-1978. Institute of Agricultural Research, Addis Ababa. pp 2-22.

Mesfin Abebe. 1982. Uses of improved seedbed and fertilizers as an alternative to soil burning or 'guie '. Ethiopian Journal of Agricultural Sciences 4(1):1-9.

Morton W H. 1977. Geological notes for the field excursion. In: Reports of the Second Meeting of the Eastern African Sub-Committee for Soil Correlation and Land Evaluation, Addis Ababa, Ethiopia, 25-30 October 1976. World Soil Resources Reports No. 47. FAO (Food and Agriculture Organization), Rome. pp. 96-100.

Taye Bekele. 1986. Effects of soil heating on the properties of soils and plant growth at Sheno. Paper presented at the Workshop on the Review of Soil Science Research in Ethiopia, Addis Ababa, Ethiopia, 11-14 February 1986.

Willcocks T J and Browning J. 1986. Vertisols (black cracking clays): A bibliography with some abstracts, extracts, context analyses and comments. Overseas Division, AFRC, Institute of Engineering Research (formerly NIAE), Silsoe, Beds, UK. 134 pp.


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