Chapter 2
Ecology (continued)

References

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wilson, a.d., 1966c: “Absorption of high quantities of salt by sheep. A problem of semiarid grazing areas,” Rural Res. In: csiro, December 1970: 7–10.

wilson, a.d.; leigh, j.h.; hindley, n.l. and mulham, w.e., 1975: “Comparison of the diets of goats and sheep on a Casuarina cristata-Heterodendrum oleifolium woodland community in western New South Wales,” Aust. J. Animal. Husb. 15: 45–53.

wilson, j.g. and bredon, r.m., 1963: “Nutritional value of some common cattle browse and fodder plants of Karamoja, Northern Province, Uganda,” E. Afr. Agric. For. J. 28: 204–208.

wood, g.w. and lindsey, j.s., 1967: “The effects of forest fertilization on crude protein, calcium, and phosphorus contents of deer browse in a mixed oak forest,” Naturaliste Canadian, Quebec, 3: 335–346.

wood, j.g.; woodroffe, k. and trumble, h.c., 1947: “South Australian,” In: The use and misuse of shrubs and trees as fodder, Imperial Agric. Bur. Joint. Publ. No. 10, Aberystwyth. pp. 25–29.

wright, h.a., 1970: “The response of big sagebush and three-tip sagebush to season of clipping,” J. Range Mgt. 23: 20–22.

wright, h.a., 1972: “Shrub response to fire,” In: Wildland shrubs - their biology and utilization, u.s. Dept. Agric. For. Serv. Tech. Rep. int-1. pp. 204–217.

wright, h.a., and stinson, k.j., 1970: “Response of mesquite to season of top removal,” J. Range Mgt. 23: 127–128.

young, j.a.; hedrick, d.w. and keniston, r.f., 1967: “Forest cover and logging-herbage and browse production in the mixed coniferus forest of northeastern Oregon,” J. For. 65: 807–813.

The Use of Fodder Trees and Shrubs for Animal Production

Fernando Riveros
Senior Officer, Grassland and Pastures Crops Group
Plant Production and Protection Division
FAO, Rome, Italy

Introduction

Man's demand on natural resources that sustain his existence, and population pressure on land resources, are increasing at an alarming rate. At the beginning of the present century the world population was only a little over 1.5 billion. It rose to 4 billion in 1975 and reached 4.7 billion in 1983 with an increase of 18 percent (fao, 1984). It is projected to be about 6.3 billion by the end of this century (United Nations, 1977), with 80% living in developing countries.

Livestock population is also rapidly increasing. In the period between 1974–1983, cattle numbers have risen 3% in the world as a whole, with the highest rate of 21% in the Near East, 11% in Africa, 4% in the Far East, and 4% in Latin America. Sheep and goat numbers have risen 13% in the world as a whole, with the highest increase of 39% in Africa, 25% in the Far East, 21% in the Near East, and 10% in Latin America. A similar or even higher trend is expected during the next 15 years with rapidly increasing demand for livestock products, which will rise at about the same rate as the general demand for food in the developing countries. To meet the demand for food in the developing countries, agriculture and livestock production should be more than doubled (Bommer, 1978).

Many of the world's poorest people live a precarious existence in the semiarid and arid tropics and subtropics. Nearly 60% of the 47 countries located in continental Africa have more or less significant arid and semiarid areas (Riveros, 1985). Livestock production is often the most economically efficient way to utilize the abundant land and scarce water resources of these arid lands; consequently, plants that can provide a greater quantity and better quality of livestock feed are highly desirable. Adapted fodder trees and shrubs have some of the highest potential to improve natural arid rangelands in terms of total productivity and nutritive value, as well as a resource of feed reserve during the dry seasons and prolonged drought periods (Ibrahim, 1981).

Fortunately for livestock production, there is great potential from shrubs, still untapped, in the vast rangelands of the world. In recent years, scientific investigations have gradually accumulated much information about shrubs in terms of their nutritive value, dry matter yield, palatability to livestock and wildlife, use for wildlife habitat, physical characteristics, and other biological functions.

This paper summarizes some of the recommendations by the major seminars and conferences regarding the needs and opportunities for research and development programs, particularly for developing countries, and reviews some of the important publications on fodder trees and shrubs.

During the last two decades, over 325 papers on Prosopis spp. were published, covering very wide fields such as taxonomy, genetics, physiology (including germination, metabolism and nitrogen fixation), chemical composition, nutritive value, livestock production, biomass (including forage and pod production), control, wood technology and land reclamation.

Recommendations

It is impossible in this brief paper to summarize all the recommendations made on the utilization and research programs on fodder trees and shrubs.

During the International Symposium on “Wildland Shrubs” held in Logan, Utah, July 1971, an ad hoc committee recommended the establishment of an International Advisory Committee to identify needs for action and research on shrubs. Box (1972) reported the summary of the recommendations by that committee as follows:

1. Improve communication between scientists by publishing proceedings and establishing a newsletter.

2. Develop an inventory of shrub research and knowledge. Encourage an international agency to publish the material and keep it current.

3. Organize a committee to coordinate research efforts on a worldwide basis.

4. Identify research areas necessary for increasing production in shrubs. Establish priorities for action programs.

5. establish a program for exchange of knowledge, scientists, seeds, and equipment.

6. Plan a future meeting in 3 to 5 years to examine progress since this congress.

An extensive review by Ibrahim (1981) presents a comprehensive listing of references (175) on factors affecting dry matter yield, palatability, nutritive value, and utilization of fodder shrubs. Factors affecting production and intake include environmental conditions, stages of growth, associated species, genetic makeup, and chemical content. Among the factors affecting utilization are the season, frequency and intensity of grazing by different classes of livestock and wildlife, as well as other environmental factors. Some recommendations as to the needs and opportunities for research and development programs, particularly for developing countries, are briefly presented as follows:

1. The establishment of gene banks equipped with cold storage facilities and nurseries for living shrub collections would provide seeds and vegetative material for research work. Gene banks are very expensive to establish and to maintain in developing countries. Therefore, in these countries, regional rather than national germ plasm banks should be encouraged with the support of international organizations. Where the facilities and staff are available, national forage gene banks, such as the one established at the National Agricultural Research Station, Kitale, Kenya, should be encouraged and supported.

2. A major part of shrublands occur in developing countries. Many of these countries cannot afford to support studies on their native fodder trees and shrubs, and those Third World countries which can afford the expenditure, most usually do not have the manpower and facilities to carry out such studies. Therefore, it might be useful to organize regional projects supported by international agencies to undertake studies on the ecology of important fodder shrubs or trees, particularly their range of adaptation, productivity, nutritive value, and utilization.

3. The simplest source of information about fodder shrubs and trees in many developing countries of Africa, Asia, and South America is not available or not well documented. For several generations native grazers have gathered valuable information about shrub adaptation and utilization which is not documented or known to scientists. Efforts should be made to collect the available information on fodder trees and shrubs from nomadic and semi-nomadic tribes.

4. There is a need to assess the total potential production on the important range types including all their grasses, herbs, shrubs, and trees. For instance, in subtropical rangeland, grasses furnish the bulk of forage production during the growing season, while shrubs provide animals with highly nutritive fodder during the dry period. It is a known fact that fodder shrubs serve as dietary supplements and provide important nutritional components such as protein, phosphorus, and carotenoides when these components are less adequate in other available forage. In many range surveys the shrub component is not reported, basically because it is difficult to assess it. It is important, particularly in developing countries, to develop a guideline for simple techniques such as fecal analysis, twig length, or crown diameter to assess the browse component.

5. Studies in developing countries should be of an applied nature, such as the identification of important species, test adaptation trial of introduced and native species, and utilization rather than advanced detailed studies on their physiology, quantitative ecology, breeding, and cytogenetics Undoubtedly, all aspects of research would eventually contribute to understanding of fodder shrub utilization.

6. In developing countries, herds are composed of different classes of livestock. Some are mainly browsers, such as goats and camels, and some are grazers, such as cattle and, to a certain extent, sheep. They all share the same range at one time or another. This livestock also often shares the same ground with wildlife and sometimes with game, as in subtropical East Africa. The multiple use of an area by wildlife and different classes of livestock is a better measurement to express shrubland productivity.

7. Perhaps with the exception of some of the educational institutions in the United States and Australia, the subject of fodder trees and shrubs is hardly mentioned in the regular academic courses of forage and range management. It is hoped that the importance of fodder trees and shrubs and their contributions to the world range resources will be given more attention.

In 1984, an International Round Table on Prosopis tamarugo Phil. was held in Arica, Chile, attended by over 90 participants from 21 countries (fao, 1985). The main purpose of this Round Table was to congregate scientists and technicians from different parts of the world interested in the development of arid and semi-arid zones, to analize and discuss the Chilean experience in desert development based on the utilization of man-made Prosopis tamarugo plantations by livestock, and to share the experience of other countries in the use of other species of the genus Prosopis.

Three committees —America; Africa, Near and Far East; and Chile— were formed to discuss and recommend the reasearch, demonstration and development activities pertaining to Prosopis spp. Among the important recommendations are the following:

The committee for America recommended that:

1. in the Second International Meeting on Prosopis, businessmen and producers involved with the genus would be invited to exhibit their products,

2. the participating countries would contribute with the technical, traditional, current and potential knowledge on the use of Prosopis, for which the Committee, headed by Peru, had formulated a guideline for data collection,

3. each of the countries should promote the formation of a national Prosopis association with a view to its internationalization,

4. for an active and efficient communication, it was necessary to count on an executive board formed by a representative and a deputy,

5. there was a need for an informative newsletter on general aspects on Prosopis, with the possibility that Brazil, with its infrastructure, would be encharged with it. fao offered to release such a newsletter together with their annual publication on Forest Genetic Resources,

6. general coordination by fao was essential, to which the Committee will report,

7. the Committee for America will seek to invite the various American countries which have the Prosopis species but are not represented.

8. germplasm and Rhizobium banks would be established in each country, taking into account provenance, progeny, standards, and in situ and standard trials and tests,

9. a collaboration between the different countries was proposed regarding:

   • studies on, or taxonic classification of, the genus Prosopis,
   • exchange of human resources,
   • interdisciplinary nomenclature of institutions, persons, and researchers,
   • a bank of projects and research lines,
   • standardzation and establishmentof a working methodology,
   • resource inventories and prospects,
   • multiple use and management practices for the resource,
   • designing a logotype with the outline of the American continent, as background to an arboreal Prosopis spanning the continent.

For Africa, the Near and Far East, the meeting recommended research, demonstration and development activities pertaining to the following:

1. The cooperative research development network through an international cooperative network involving national and regional institutions and on-going projects.

2. Identification of Prosopis species with potential for multiple use in the arid and semiarid parts of Africa, Near and Far East.

3. The study of adaptation and behaviour of recommended leguminous trees and shrubs under agrosilvopastoral systems in order to increase productivity in terms of crop yield, livestock production and soil protection.

4. The development of standardized techniques for the evaluation of fodder species proposed with respect to their adaptability, behaviour, productivity, nutritional values and other such items are limited.

5. Development of a package of agro-silvopastoral systems with lopping intensity and lopping cycle, spacing of three species for inter-cropping with other species suitable for the region to be worked out. Grazing systems to be standardized as per carrying capacity of the rangeland with adoption of rotational or deferred grazing systems.

6. Regular training courses for technicians and extensionists from the participating countries should be conducted.

For Chile, the Committee recommends the following lines of action:

1. To continue and enlarge, if necessary, observations tending to characterize the physical environment at the Tamarugal Pampa.

2. To diagnose the present condition of the plantations and natural forests.

3. To conserve, select, reproduce, and distribute genetic resources.

4. To encourage the utilization of the available information about the management of the resource.

5. To continue with the assessment of the productivity of the Tamarugal Pampa System.

6. To establish the research studies necessary to develop the application of technology to the resource.

7. To continue the study of the silvicultural and protection treatments for the management of the forest, within the concept of multiple use.

8. To explore the ancestral utilization patterns of the resource, particularly the transhumant activities and the interactions with their respective ecosystems.

9. The multi-disciplinary teams participate in the design and supervision of the planning process for the area.

Conclusion

There is a wealth of information on fodder trees and shrubs on a worldwide basis.

Several international meetings were held during the last two decades to discuss the utilization of these fodder crops. Excellent recommendations were presented. A good number of highly qualified scientists are currently carrying out research and extension programs in almost every continent of the world. It is suggested that the recommendations made on the use of these fodder crops by the different conferences or individual scientists should be discussed and evaluated so as to prepare an outline for a 5-year program to assist the various countries having an interest in this work.

References

anderson, r.h. 1947: “New South Wales, Australia,” in: The use and misuse of shrubs and trees as fodder, Imperial Agric. Bur. Joint Publ. No. 10, Aberystwyth. pp.13–19.

bommer, f.r. 1978: “Rangeland resources and world food needs,” in: Proceedings of the first international rangeland congress, Denver, Colorado, pp. 5–6.

box, t.w. 1972: “Some approaches to achieving the potential of shrubs for man's use,” in: Wildland shrubs — their biology and utilization, U.S. Dept. Agric. For. Ser. Report int-1. pp. 440–444.

chippendale, g.m. and b.r. jephcott, 1960: “Topfeed,” N.T. Admin. Ext. Art. 5.

corbet, h.a. 1957: “Fodder trees,” 2nd Ed. Perth: h. a. Corbet Publ.

dayton, w.a. 1931: “Important Western browse plants,” U.S. Dept. Agric. Misc. Publ. 101. 213 p.

department of national development, forestry, and timber bureau, 1972: “The use of trees and shrubs in the dry country of Australia,” Aust. Gov. Publ. Serv., Canberra. 558 p.

everist, s. 1969: “Use of fodder trees and shrubs,” Queensland Dept. Primary Ind. Plant Ind. Leafl. 1024. 44 p.

food and agriculture organization of the united nations, 1983: “Production yearbook,” vol. 320 p.

food and agriculture organization of the united nations, 1985: “The current state of knowledge on Prosopis tamarugo,” International Round Table on Prosopis tamarugo Phil., Arica, Chile, June 11–15, 1984. fao, Rome. 464 p.

french, m.h. 1949: “The use and misuse of shrubs and trees as fodder,” East Afric. Agric. Jour. 14: 157–166.

ibrahim, k.m. 1981: “Shrubs for fodder production,” in: Advances in food producing systems for arid and semi-arid lands, Academic Press. pp. 601–642.

imperial agricultural bureaux, 1947: “The use and misuse of shrubs and trees as fodder,” Joint Publ. No. 10. Imp. Bur. Pasture and Field Crops, Aberystwyth. 258 p.

khan, a. h. 1965: “Fodder shrubs and trees in Pakistan,” West Agric. Univ., Lyallpur. 132 p.

mcginnies, w. g. 1972: “Continental aspects of shrub distribution, utilization, and potentials — North America,” in: Wildland shrubs — their biology and utilization, U.S. Dept. Agric. For.Ser. Tech. Report int-1. pp. 55–66.

mckell, c.m.; j.p. blaisdell and j.r. goodin, 1972: “Wildland shrubs — their biology and utilization,” U.S. Dept. Agric. For. Ser. Gen. Technical Report int-1. 494 p.

riveros, f. 1985: “Fodder shrubs in Africa,” in: The current state of knowledge on Prosopis tamarugo, International Round Table on Prosopis tamarugo Phil., Arica, Chile, June 11–15, 1984. fao, Rome. pp. 205–209.

torres, f. 1983: “Role of woody perennials in animal agroforestry,” Agroforestry Systems, 1: 131–163.

united nations, 1977: “World population prospects as assessed in 1975,” Population Studies No. 60, New York. p. 14.

williams, r. e.; b. w. allred; r. m. denio and h. a. paulsen, 1968: “Conservation, development and use of the world's rangelands,” 21: 355–360.

Prosopis juliflora (Schwartz) DC, a fast growing tree to blossom the desert

K.D. Muthana
Scientist
P.O. Box 12, Kushalnagar, India

Introduction

Prosopis juliflora is a thorny, large-crowned, evergreen to semi-evergreen tree with deep as well as lateral root system. It grows up to 10-meter heights, depending on type of soil and climate.

It was introduced to India in 1877 (Sind) and, later on, in many parts of the country, including Hagari, Bellary (Karnataka), Punjab, Agra, Delhi and other areas. It was also introduced in dry regions of South Africa, Sudan and some parts of Australia, and has proved useful as a pioneer tree to improve degraded lands. The then ruler of Jodhpur State introduced it in 1913 in many arid and semi-arid parts of Rajasthan, with great success. The State Government declared this species a “Royal Plant” in 1940, and exhorted the public to protect it. It also encouraged large scale planting with this species.

It proved to be the most versatile plant for afforestation on shifting sand dunes, coastal sands, eroded hills and river beds, saline terrains, dry degraded grasslands and wastelands with scanty and erratic rainfall. It grows well in regions with 150- to 600-mm rainfall. It is fast growing and reproduces by coppicing and through root suckers. It is seen profusely growing on vast wastelands and grazing lands, mainly through seeds encapsulated in the droppings of goats and sheep. The quality of feed it supplies through pods and its good quality fuelwood, produced in short rotations, is a boon to the desert dwellers, therefore remaining always in great demand in most parts of the arid and semi-arid regions. Although it is an introduced tree species, it is now well adapted to the Indian dry zones.

The usefulness of P. juliflora in afforesting arid and semi-arid areas has long been recognised by foresters and tree lovers. It can be grown as a tree, a shrub and as a hedge. It is a useful sand binder and has established a reputation as a good and fast growing species for reclamation of degraded grasslands and wastelands, where no other valuable tree species would easily grow. It is drought resistant and tolerates mild frost and has the ability to withstand adverse conditions. Argentinian and Mexican types are reported to be frost hardy but the Australian type is susceptible to frost at seeding stage. The Peruvian type has been found to be more sensitive to frost than the Australian one. Therefore, choice of provenance is of great importance before large-scale afforestation programmes are initiated.

General description

Prosopis juliflora belongs to Fabaceae sub family Mimosae. It is a medium to tall evergreen tree (3 to 15 m tall), sometimes shrubby. It has thorny, spreading branches. Leaves are glabrous or pubescent, petiole plus rachis 0.5 to 5 cm long, pinnae 3 to 10 cm long, leaflets 6 to 12 pairs per pinnae and elliptic oblong, 0.6 to 2 cm long and 0.2 to 0.5 cm wide. Florets are greenish white turning light yellow to brown, compressed, about 8 to 20 cm long by 0.75 to 1.0 cm broad and 0.4 to 0.75 cm thick. Seeds are brown, compressed and glabrous. Flowering and fruiting is generally from August to October three to four years after establishment. Seeds are firmly embedded in the pods. There are about 400 to 500 pods/kg and about 10 to 25 seeds per pod.

Seed extraction

Extraction of seeds from the pods is rather difficult and a few methods evolved in India are detailed below:

The gummy seeds with their inner seed cover intact are soaked in a 0.1 N HCI solution for 24 hours. Remove them from the solution and again soak in clean water for an hour and then dry them in the sun. While drying the segments start opening and they are slightly pounded to remove the outer coat to obtain clean seeds (Vasavada et al., 1973). Weevils often damage the seeds, hence pod/seeds collected may be fumigated before storage. About 10,000 to 20,000 seeds weigh one kilogram.

Pretreatment

1. In India, the pods are generally broken into smaller segments leaving one seed in each segment. These segments are soaked in water for a period of 24 hours and then rubbed with the hands to remove the coat. This method will give out seeds with a fibrous seedcoat which is not easily separated. These segmented seeds are sown at site or in the nursery beds.

2. The simplest and most commonly used method is to feed the entire pods with seeds to goats or sheep, collecting and sowing thereafter the seeds ejected by these animals during rumination or which have passed through their digestive system. Such seeds embedded in the droppings germinate quicker and give higher germination rates.

3. If clean seeds are required for experimental sowing, the best method is to separate them from their inner fibrous seedcoat and after soaking them in water (tap or well water) overnight, these are sown and give good germination.

4. To remove the dormancy due to the hard seedcoat, the broken pods are soaked in concentrated sulphuric acid for 15 to 20 minutes and then washed thoroughly in cold (tap or well) water. Seeds thus treated germinate in about 4 to 6 days with 80 to 90 per cent germination.

Nursery techniques

Seeds are sown in lines in nursery beds or in galvanized tubes 10.2 cm in diameter and 30 cm in length, or 7.5 cm diameter and 30 cm long, or in 11-cm × 22.5-cm perforated polythene bags, or in sun dried 30-cm-long earthen bricks having 15 cm² at the bottom and 10 cm² at the top, with a hole at the top 10 cm deep × 2.5 cm in diameter, for transplanting in the field during the onset of monsoon. Under favorable conditions, the seedlings develop very fast and attain a height of about 30 to 45 cm within a period of 9 months. Early growth of stipular spines is conspicuous. Tap root development exceeds about four times that of shoot. Young plants have a tendency to develop long tap roots but as the plants grow in age, they send out lateral roots depending on soil type. Seed sowing is generally carried out in September or in February and seedlings attain, on an average, a height of 45 to 30 cm, respectively, by following July. Both these seedling sizes (45 and 30 cm) are recommended for planting. Since young seedlings are frost-prone, it is desirable to raise seedlings after the winter period.

Planting techniques

Nine to ten month old seedlings or pre-sprouted stumps are planted in 60-cm³ pits at the required spacement. A planting programme should commence with the onset of the monsoon. After transplanting, saucer shaped depressions one meter in diameter, having a depth of 15 cm near the stem of the plant, may be provided in plain areas; on slopy areas, crescent shaped ridges of 15 cm high across the local slope may be provided to harvest the runoff water for boosting plant growth. Weeding and soil working is necessary and should be performed twice a year and continued until the plantation is about three years old.

In case of no rains after transplanting, supplemental watering should be provided at nine liters per plant at fortnightly intervals for proper establishment. If well-distributed rains occur after planting, watering need not be done until March or until the plants show signs of wilting.

If Prosopis juliflora seedlings are to be raised on field boundary as live hedge or as windbreak, pretreated seeds may be dibbled 15 to 30 cm apart in lines during rainy season to get a thick row of vegetative cover.

If the objective is to protect the avenue plants from biotic interferences, seeds of Prosopis juliflora may be sown in trenches around the avenue plants 1.5 meters away from the main planting pit. P. juliflora seedlings grow so fast and vigorously that they provide adequate protection to the avenue plants in the initial stages and when avenue plants become established and reach about 2 to 3 meters in height, P. juliflora may be felled for fuel.

Growth attributes

Prosopis juliflora is a fast growing, drought-hardy tree next to or equal to Acacia tortilis in its importance for arid and semi-arid regions. The only plus point Acacia tortilis has over Prosopis juliflora is that leaves of A. tortilis have fodder value, whereas leaves of P. juliflora are not edible (Table 1).

TABLE 1
Comparative Merits and Demerits of P. Juliflora Over A. tortilis

Furthermore, it may be emphasized here that Prosopis juliflora (Israel) has performed better with respect to all growth parameters when compared with Acacia tortilis (Israel) and other indigenous conditions (Table 2).

TABLE 2
Comparative Growth of Prosopis juliflora(Israel)

Studies on pre-sprouted stumps of Prosopis juliflora revealed that seedlings raised from stump cuttings grow rapidly. Various sizes of stumps from 1 year old seedlings of Prosopis juliflora were grown in nursery beds. Stumps of 1.5 cm collar diameter, 2.5 cm shoot length, having 17.5 cm length of root portion, have been found to be of optimum size for raising stocks. These stumps were transplanted in galvanized iron tubes and were kept under identical environmental and watering conditions in the nursery. It was also observed that under nursery conditions smaller stumps (both in terms of collar diameter and root length) reduced the sprouting period compared to the stumps of larger collar diameter and longer root length.

When compared with the effect of size of presprouted stumps on their subsequent growth in height seven years after transplanting, it was observed that the initial gains in growth in the nursery did not maintain their superiority over other treatment combinations on planting in the field.

Different sizes of stumps varying in collar diameter and root length influenced the sprouting period, whereas there survival in the nursery was affected by root length alone. Prosopis juliflora stumps of 1.5 cm collar diameter and 17.5 cm root length appeared to be the most suitable size for presprouting in the nursery. Their field establishment and subsequent growth in height remained unaffected by their size (Bhimaya et al., 1965) (Table 3).

TABLE 3
Mean Growth in Height (cm) of Presprouted Stumps After Seven Years of Out Planting

Comparative performance of Prosopis juliflora and Acacia tortilis with regard to various growth attributes

Seed germination studies showed that seeds of both the species sown on August 22 continued to germinate until September 8 in the case of P. juliflora, whereas germination stopped from September 3 in A. tortilis, giving 67 and 43 percent germination, respectively. It was also noticed that germination commenced in A. tortilis as from the third day after sowing, whereas it started from the fourth day in P. juliflora. Maximum germination per cent was recorded on the third and fourth days after sowing in A. tortilis, whereas it was from the sixth to ninth days in P. juliflora.

Regarding growth rate of shoot and root, maximum growth was recorded during the second week in P. juliflora (3 cm), while A. tortilis showed some growth in the fourth week (2.5 cm). In the seedling stage, growth of shoot and root and the development of secondary roots, there is hardly any significant difference in both species when recorded from the seventh day to the seventy-fifth day of the growing period. Nodulation was initiated in A. tortilis from the fourth week, while it commenced from the sixth week in P. juliflora. A greater number of leaves was recorded in the tenth week (75 days) in A. tortilis (Av: 85.60), whereas it was much less in P. juliflora (Av: 25.0). Secondary rootlets where much more numerous in A. tortilis than P. juliflora, which may also be attributed to the capacity of A. tortilis to establish well even under dry conditions as compared to P.juliflora (Gupta Balara, 1972).

Studies to determine the optimum age of exploitation and fuel yield of P.juliflora were carried out on five different habitats of different rainfall zones, namely Sardarshahar (268 mm), Jhunjhunu (395 mm), Gadra Road (285 mm) and Bikaner (285 mm). There were wide variations in fuel yield both with respect to tree age and habitat. There were significant age differences in all the habitats. The habitat differences were significant in 4.5 and 10 year old trees, and it was also inferred that with the increase in tree age, tree to tree variability decreased. A study of mean annual rainfall of these habitats indicated that the difference in fuel yield between the habitats followed the pattern of increase in the rainfall from west to east. It was further seen that fuel yield increased with the age of the trees and has correlation with climatic factors (Table 4).

TABLE 4
Average Fuel Yield per Tree in kg (m) and Percentage Standard Error (cv) as Affected by Different Ages and Habitats

* Figures in parenthesis denote the number of trees harvested.

Data on different relationships between growth attributes and fuel yield are given in Table 5.

Data on growth attributes, namely diameter at breast height (cm) (dbh) and tree height (m) as affected by age of tree and habitat, are presented in Table 6.

TABLE 5
Results of the Correlation and Regression Analysis

* Significant at 0.1% level of probability. Diameter at BH and tree height were positively correlated with fuel yield (Bhimaya et al., 1967).

TABLE 6
Average (m) and Percentage Standar Error (CV) Values of DBH (cm) and Height (m) per Tree

There were wide variations in dbh and height of trees of different habitats. A comparison of data in Tables 5 and 6 revealed that trees of higher dbh produced higher fuel yield, whereas tree height did not influence its fuel yield to the same extent. The habitat X age interaction was significant for both parameters. It was also determined that dbh alone is sufficient for predicting fuel yield (Kaul and Jain, 1967; Kaul et al., 1964). The equation Y = 2.10 + 5.08X, where “Y” is the yield in kg and “X” is dbh in cm, can be used for prediction purposes. It was also found that with a unit increase in dbh, the yield increases by about 5 kg for the age range of the trees.

A replicated study to find out the most economic and easiest method of establishing P. juliflora in plantations on the wastelands of Western Rajasthan, was carried as detailed below:

3 treatments: a) 1 cm deep, b) 2 cm deep, and c) 4 cm deep sowing with 3 replications. 2 sites: i) fenced and ii) unfenced.

Prior to sowing at these two sites, seeds were soaked for 40 hours in tap water. Inside the fence area, commencement of seed germination was observed from the fifth day in all the treatments. The germination of seeds continued for 67 days. Maximum seed germination ocurred (Table 7) within the first 30 days, with more than 50 per cent in “a” and “b” treatments, about 40 per cent in treatment “c” and negligible thereafter under fenced area. The data also revealed that there was no significant difference between treatments “a” and “b”, but between treatment “a” and “c” and “b” and “c” significant differences were observed, indicating that placing P. juliflora seeds beyond 2 cm depth is not desirable.