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MINISTRY OF AGRICULTURE AND ANIMAL HUSBANDRY

RESEEDING DENUDED PASTORAL LAND IN KENYA

by

A. V. BOGDAN AND D. J. PRATT

Seven Shillings - 1967

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Reseeding Denuded Pastoral Land in Kenya

by

A. V. BOGDAN AND D. J. PRAIT Denuded Land The Njemps Flats: an alluvial plain on the floor of the Rift Valley near Lake Baringo which bas been denuded for decades, despite an average annual rainfall of 25 in. The result of reseeding this country is shown in Plate 9. (Photo: September 1965 by O. J . Pratt.) FOREWORD

The history of reseeding in Kenya lis largely one of individual endeavour on the part of a handful of officers, mosHy of the Depart­ ment of Agriculture, who have abtempted during their service in pastoral districts to rep~ir the denuded grazing area·s under their care. The number of published accounts of this work are few, but in 3lppreciation of i1tS importance as the foundation of present-day knowledge, this bulletin is inscribed to those officers concerned, with particular acknowledgement to J. S. Bagenal, L. H. Brown, G. Cowley, R. N. Edmondson, T. Hughes-Rice, S . .M. Jordan, the late W. Lang­ r·idge and H. J. York. Their experience is supplemented here by data from a series of experimenlis conducted ·by D. J. Pratt and J. Knight in 'Baringo District, and leavened by our independent persona! experi­ ence. The section "Grasses for Reseeding" bas been wriNen mainly by A. V. Bogdan and the remainder mainly 'bY D. J. Pratt, each section Teceiving mutual approval. Wbilst the rneed for more work is ev.iden·t, it is hoped that the result will prove of value to those who have the present responsibility for reb1l'bilitating Kenya's pastoral a reas. A. V. BOGDAN. D. J. PRATT. CONTENTS

INTRODUCTION 1 GRASSES FOR R ESEEDING 2 Grass Types 2 Recommended Species 3 Bothriochloa insculpta and B. perfusa; Cenchrus ciliaris 4· Cenchrus pennisetiformis; C. setigerus; Ch/oris gayana; C. mossambicensis . . 5 Ch/oris roxburghiana; C. virgata; Chrysopogon aucheri; Cynodon dactylon . . 6 Cynodon plectostachyus; Dactyloctenium sp.; Echinochloa haploclada; Enteropogon macrostachyus . . 7 Enteropogon somalensis; Eragrostis caespitosa; E. chloro- melas; E. cilianensis; E. sp. nr. curvula . . 8 Eragrostis superba; Eriochloa nubica; Eustachys pa spa/aides; Latipes senegalensis 9 Leptochloa obtusiflora; Panicum co!oratum; P. maximum; Paspalidium desertorum; Sporobolus he/valus 10 Sporobolus ?marginatus; Tetrapogon villosus; Themeda triandra; Tricholaena eichingeri 11 Choice of Species 11 Seed Collection 12 RESEEDI NG TECHN IQUE 15 Choice of Site . . 16 Preparation of Site 16 Seed-bed Cultivation 17 Time of Cultivation 18 Terracing 19 Seeding . . 19 Time of Seeding 19 Methods of Seeding 19 Seeding Rates 19 Supplementary Seed Protection 23 Insecticides . . 23 Cut Branches 24 Pelleting of Seed 24 Harrowing . . 24 Specialized Techniques for Problem Areas 25 Dense Bushland or Shallow and Rocky Soils 25 Dissected and Rilly Terrain 25 Arid Areas . . 26 Species/Treatment Interactions 27 GRAZI NG MANAG EMENT 29 REFERENCES 31 APPENDIX: Catalogue of Proprietary Machinery and Seed Suppliers . . 32 RESEEDING DENUDED PASTORAL LAND IN KENYA There are in Kenya extensive areas of overgrazed pastoral land which are in urgent need of rehabilitation. If the original grass cover bas not been completely destroyed, rehabilitation through grazing management may be possible; but if denudation is absolute, or the flora reduced to poor species only, then reseeding must be undertaken.

The primary reason for reseeding is to restore productivity; so that the full potential of the area may be realized, to the benefit of the individual, the district and the nation. The reason for taking action sooner rather than later is to con­ serve as much as possible rthe soil t'hat remains, before the potentia·l of the area is permanently impaired.

A soil surface that is without a protective mantle soon becomes hard and impervious, and repels ail but a fraction of the rain lthat falls on it. The rest (perhaps 80 per cent or more) is forced to run off, eroding the soil over which it flows and fill.ing the streams with a flood of water and soil. Not only does the denuded area deteriorate progressively but the muddy flood waters constitute a hazard in their own right. lndeed, the protection of dams from silting, or the provision of a controlled flow of clean water to irrigation or other projects, may be important factors in initiating a reseeding programme.

The areas of Kenya most in need of reseeding are usually of low rainfall and limited potential. They are also characterized by relatively dense hurnan popula­ tions, which may not yet have adopted a commercial system of land-use. The present bulletin is written against this background, and emphasis throughout is laid on grasses and methods for dry areas, with the assumption that low cost is of paramount importance.

No panacea is offered to guarantee success in reseeding. Any 1 eseeding opera­ tion, however carefull y planned, can fail if insuffioient ra·in talls at the righ.t time. Nevertheless, proper appraisal of the situation a nd the correct ohoice of grasses and methods go a long way towards ensuring success.

From the many attempts that have been made in Kenya to restore grass cover by means of seeding, on plot- and field-scale, it bas been learned that the funda­ mental requirements of success are:- (1) An appreciation of the ecological potential of the area concerned. (2) Grasses suitable for reseeding purposes and sufficient seed of adequate quality. (3) The integration of the reseeding operation into an overall land-manage­ ment policy, embracing grazing control and bush-control where necessary. (4) Sorne form of seed-bed preparation and a degree of seed protection in keeping wi•th si.te requirements. (5) A period of complete rest from grazing after seeding. (6) Reasonable rains during the establishment seasons.

It must be emphasized that failure in any one of these requirements can prove fatal, and every effort must be made to meet them all. Rainfall is beyond control, but species and techniques may nevertheless be so chosen that slightly below­ average rainfall will ensure success. Also, on sorne sites, it will be possible to safeguard against poor rains by using water-harvesting and water-spreading techniques to bring extra water to the site. Whereas these technical aspects are considered ·here in sorne detail, it· bas been decided not to attempt to cover the economie aspects of reseeding. The variables involved are too numerous and inconstant for averages to be meaningful. The cost of operations involving band-labour varies in time and space according to labour charges and output; machinery costs are standardized on an bourly basis but vary enormously on an acre basis; and the cost of the seed depends on whe~ber it is bougbt, grown or collected from wild stands. Also, although the financial return from reseeding can be calculated assuming optimum land-use, reseeding is oiiten undertaken with otber benefits in mind, on land where immedialte commercial exploiAfrica, bas been used locally with any success.

GRASS TYPES Grasses may lbe divided according to tbeir life-span (i.e. whetber they are annuals or perennials) and according to their habit of growth. Botb alttr·ibutes affect the suitability of grasses for reseed·ing. Whilst annual grasses last only one year or one wet-season and die when seed is formed, perennials bave the ability to survive dry seasons and regenemte with each rains rto produce f.resh growth from .the original mot stock. Aiùhough perennials may seed every season, they live for a ifew rto severa! years, mostly about six. In the field, they may •be recognized lby the presence of old, dry .remnants of the previous year's grow.th and by 11he .fact ltbat rthey are not easily uprooted. In unspoiled natural grassland that bas developed under an average annual rainrfall of more than 20 in., perennials form the bulk of the herbage and annuals occur only occasionally. Under drier climates, the proportion of annuals is greater; and the same can be observed in over-grazed and mismanaged pastures even where the rainfall is sufficient to support a perennial grassland. An average

2 annual rainfall of about 10 in. represents .jn Kenya the lower limit for the survival of perennial grasses: with less rainfall, perennials can on! y persist in favoured si•tes and llhen only if subject to very light grazing. In the intermediate 10-20 in . .rain.fall zone, it is common to find only a proportion of the rperennial grass population acting as true perennials; the remainder last only one season and die before they can fully establish themselves. Sorne species, such as Latipes senegalensis a nd Tetrapogon villosus, are more prone 1o this form of behaviour than others. In annual grasslands, plant population and heribage productivity fluctuate between wide extremes. In favouralble seasons a •bulk of herbage is produced which may exceed in palatabilirty and nutri•tive value .that of perennial species, but this productivioty is strictly seasonal and annual grasses have limited value for dry-season grazing or in preventing soi! erosion. Therefore, for reliable year­ round productivity and conservation of 1'he habitat, perennial grasses should be used wherever the potential permi.ts ; with the provision that, under marginal rainfalls, a proportion of annuals in the seeding mixture may aïd the initial stages of recovery and provide an additional safety margin. Within the natural annual grass zone, there is of course no point in sowing perennial grasses, unless the natural rainfall is to be supplemented lby a technique such as warter-spreading. Amongst the perennial grasses, diverse growth baJbits occur and rhizomatous creepers (with underground runners), stoloniferous creepers (witb surface runners) and tufted or "bunch" grasses can be distinguished. The stoloniferous grasses can in turn be classified into fast and slow creepers. The former have long stolons and cover the ground quickly, tbough -inirtially llhey form only loose stands and allow otber grasses to grow in tbeir midst; whilst the latter form a dense network of short stolons which colonize the ground slowly and steadily. Rhizomatous grasses are seldom found in dry areas, except at stream banks, and are not used for reseeding. ln most grassland types, tufted species form the dominant component of the climax community.

RECOMMENDED SPECŒS The requirements of a grass for reseeding are that it must be suffi.ciently drougbt tolerant to survive, perpetuate Ïltself, and provide a good quantity of herbage of fair .or good grazing value. It should also produce an adequate amount of viable seed wbicb can be easily barvested, and it should be easy to establisb. Tbose species which are believed to sa

3 effects of soil and season, there is a broad climaJtic influence which affects dry­ season values particularly. Whereas grass growing under most clima·t-ic régimes shows a progressive decline in nutritive value with approaching maturity, resulting in extremely low dry-season protein values, i-t is common for grasses growing under an arid climate to be killed 'by desiccation when still physiologically imma1ure and to cure with a relatively high protein content.

An example of the latter phenomenon is provided by two samples of Aristida mutabilis (a common annual of the dry areas) collected a:t a·bout the same time in 'the Rift Valley, one from semi-arid Baringo and one from ar·id Turkana. The former, at the flowering stage but still with sorne green leaf, bad a crude protein content of 3.73 per cent of the dry matter, whilst the latter, as dry straw, bad a orude protein content of 5.53 per cent. The digestible crude protein contents, by calculation, were 0.93 per cent for the Baringo sample and 2.05 per cent for the Turkana sample (all determinations by H. W. Dougail). Wi·th grasses of better grazing value than A. mutabilis, such as those described below, this phenomenon can make the difference between a sub-maintenance and a main­ tenance diet for cattle.

Bothriochloa insculpta and B. perfusa; SWEET PITTED GRASS (Fig. 1).-A moderately drought-tolerant grass of tufted .ar stoloniferous ha>bit, the latter being accentuated when the grass is closely grazed or when it is growing on bare ground. B. insculpta usually forms numerous thin s·tems and its feeding value is moderate only, having a crude protein content of around 8 per cent of the dry matter at the early-flowering stage and a crude fibre content of weil over 30 per cen·t. As with ail grasses, it is most nutritious when young. The flowering heads have a strong scent disliked by cattle, but the herbage itself is not scented and is reasonably weil grazed. This grass occurs on both red and black soils and often forms extensive pure stands from which seed can be collected, as, for example, East and North-East of Nairobi. The seed (Fig. 12p) is ready for harvesting when the top portions of the inflorescences begin to disintegrate. Harvesting can ;be by plucking the ripe seed, which results in good quality seed, but is rather slow; or the stems can be eut by sickles and stooked pr-ior to threshing a few days later, with sorne loss of seed quality. The seed is fluffy because the fertile spikelets are mixed with naturaily sterile spikelets and with hairy raceme-joints. Rand cleaning is too laborious to be practical and the fluffy seed should be sown as it is. There are about 550,000 fertile spikelets, with a seed in each, in a pound of seed. Bothriochloa insculpta has been used with fair success for reseeding the medium rainfall areas of Baringo (Pratt, 1963).

Cenchrus ciliaris; AFRICAN FoxTAIL (Fig. 2).-A tuf·ted perennial, occasionally with short, stout rhizomes. It is widespread in ·the dry areas of Kenya and is highly valued for reseeding, because of its outstanding drought tolerance, persist­ ence and good grazing value. The numerous varieties differ considerably in vigour and leafiness, and care in the selection .of good types is essential. Seed formation is often poor and varies with variety and season. Among the more relia ble seeders are "Biloela", "Mbalambala" and "Kongwa 531 ". The selection kn.own as "Edward's Tall" (Kitale introduction number K.5148) is less reliable, but is extremely useful on account of its robust habit, which gives it added resist­ ance to overgrazing. In all varieties, the seed is in the form of clusters of spikelets surrounded by hairy bristles (Fig. 12a and b). Each cluster contains up to three seeds, though the majority are usually empty except in the better seeding varieties. The size and the weight of the clusters vary with va riety. The spikelets are often attacked by smut and other diseases, espeoially in the wetter areas, and ûhis may destroy the seed. The spikelets are fluffy and springy, which m akes them difficult

4 to bandle and to plant mecbanically. As the caryopses (grains) are light in relation to the cluster, winnowing of the empty clusters seems hardly practicable. A hammermill can be used to remove the hairy 'bristles, or this can be done by rubbing the clusters between sbeets of rubber. C. ciliaris bas featured prominently in nearly ali reseeding work in the drier areas.

Cenchrus pennisetiformis (Fig. 3).- An annual species, forming dense tufts, normally not exceeding 18 in. in beight. It is locally common in northern Kenya and is adapted to arid conditions with an annual rainfall of 10 in. or less. The plant is not very leafy but the stems are soft and the whole heflbage is weil grazed. C. pennisetiformis is an efficient seeder and the majority of spikelets contain weil developed caryopses. As in C. ciliaris, the spikelets are awned and rather difficult to handle. lt bas not yet been used in reseeding, but should prove very valuable for the annual grass zone and as an additive to mixtures for areas with a rainfall below 20 in. per annum.

Cenchrus setigerus.- A tufted perennial, rather similar to C. ciliaris but easily distinguishable by the absence of hairy bristles around the spikelets. It is much Jess common than C. ciliaris and much more uniform. It is equally drougbt­ tolerant and is higbly palat,able and of good feeding value: at an early-flowering stage, the herbage may contain as much as 18 per cent of crude protein in the dry matter, without being unduly fibrous. The best known seeding stands of C. setigerus are in the area North of Lake Magadi : it is often a shy seeder, though the seed can be stripped easily from the flowering head. The seed is usually better formed than in C. ciliaris but germination is poor and 10 per cent germination of good seed is the maximum that can be expected. The seed is in the form of clusters of spikelets, witb each cluster containing one to three caryopses, or none. Being free of bristles, the seed is easy to handle. C. setige rus bas been tried experimentally in Baringo (Pratt, 1963), but more experience with this grass is needed.

Chloris gayana; RHODES GRAss.-A stoloniferous perennial, common in Kenya from 2,000 ft. to over 6,500 ft. altitude, mostly on alluvial or slightly waterlogged soils, but also on loose lava ash, as in the Nakuru-Rongai area. Under sub­ optimum conditions it does not persist for more than two years. This grass is widely cultivated in Kenya, seed of severa! varieties being in commercial supply. For reseeding denuded land, the "Rongai" variety is norrnally used, both because its seed is the cheapest on the market and because it is more drought-tolerant than most other cultivated varieties. The herbage quality of this variety is lower than is average for Rhodes grass. C. gayana is a prolific seeder and the seeds are easy to handle. Each spikelet contains one, or rarely two, caryopses. Because of availability of seed and ease of establishment, the tendency bas been to use Rhodes grass indiscriminately. lts use should properly be restricted to areas where it is known to persist, which will normally mean an average annual rainfall of not less tban 32 in. in western Kenya, m 27 in. in eastern Kenya.

Chloris mossambicensis.- A stoloniferous perennial resembling Rhodes grass, but witb lower herbage and shorter stolons. lt is fairly drought-tolerant. Its palatability and nutritive value are sati sfactory, analysis showing almost 14 per cent of crude protein and 32 per cent of crude fibre in the dry matter at an early-flowering stage. C. mossambicensis is a good seeder and the seed can be collected readily from natural stands, which occur mainly in the Coast hinterland. The structure and appearance of the seed are similar to tbose of Rhodes grass, and without experience these seeds are not easily distinguished. It bas not been tried for reseeding, but deserves attention.

5 Ch/oris roxburghiana, former! y known as C. myriostachya (Fig. 4) ; ~A tufted · perennial, 2-4 ft. in height, -with characteristicaily fiat shoot bases and dense, feathery panicles which are pale green or purple when young. It is drought­ tolerant and bas good nutritive value, IWii th up to 16 per cent crude protein· in: the dry matter at the early-fiowering stage. The crude fibre content at this stage is around 30 per cent of the dry matter. C. roxburghiana is widespread in Eastern and Coast Provinces, from sea level to a bout 4,000 ft. altitude, and often forms pure stands from which seed can be collected in large quantities. The spikelets are not easily detached from the panicles (due to the matting of the long fine awns) and it is therefore convenient to eut the panicles and thresh the seed later (see Fig. 12 n and o). This can be done by mbbing the panicles between two sheets of mbber. A piece of old tyre-tube, eut to the shape of a glove and fastened to the band, is an efficien:t deviee for freeing the seed from the panicles, the latter being spread out on a rubber fioor-mat. If the naked caryopses are not freed -in this way, the seed is extremely difficult to handle, for if bagged when still enclosed in the awned spikelets, the seed aggregates into clumps which it is virtuaily impossible to ·separa·te. C. roxburghiana bas been successfully used for reseeding in Kitui and Bar-ingo (Jordan, 1957; Pratt, 1963 and 1964). However, it should be noted that it is a grass of warm climates and may not be suitable for reseeding at altitudes exceeding 4,000 ft. Ch/oris virgata; BLACK SEED.-A leafy, erect annual, common in semi-arid areas. Lt is weil grazed by stock and

6 splits. Good seeding stands are found occasionally, ·but even from the best stands the seed yields are not high (30-40 lb. per ac~e). When good seed is obtaina'ble, it is easy •to handle •and consists of individual florets, each with one caryopsis. As sta•r grass spreads rapidly, a lighter seed rate than normal is permissible. Star grass is of value as a pioneer grass which quickly oolonizes bare ground : normally it will persist only about three years, .though on fertile alluvial soils it oan maintain itself indefinitely. It is a valu ~b le grass for areas with a rainfall of 30 in. or more (or Jess on fertile soils) and, ·if seed is not available, it is worth considering planting splits, ·especially in guily

Cynodon plectostachyus; NAIVASHA STAR GRAss.~A stoloniferous perennial, very similar to C. dactylon. It is, however, more restricted .in distribution and occurs only in dry areas at altirt: udes from 2,000 to 6,500 ft. Its herbage is usually Jess dense than that of C. dactylon but seed formation is better. The leafiest types occur in the Rift Valley near Lakes Naivasha, Elmenteita and Nakuru, although for reseeding dry areas, seed should perhaps be colleoted from drier sites, such as north of Lake Magadi, or around Kiboko. The seed, which does not shed easily, can be collected by cutting the seed heads and threshing them later. As Îln C. dactylon, the seed is a single-grain spikelet, of comparable size and weigbt. C. plectostachyus bas been insufficiently tested, but for moderately dry alluvial and semi-alkaline conditions, it should prove very useful.

Dactyloctenium sp. (Fig. 6).- A stoloniferous perennial species that bas yet to be named. It occurs in a variety of forms .in arid and semi-arid areas of south-easterm •and northern Kenya, mostly on sandy soils. The type which grows near Lake Magadi is very tolerant of alkal•ine condi

Echinochloa haploclada.- A tai! , tufted perennial, which is most often asso­ ciated with seasonal swamp conditions. Tbere is one form, however, collected from open busbland on Mt. Marsabit (K.53542) wbicb is •adapted to moderately dry conditions and wbich seems from preliminary 1r-ials to ·be weil worth fur-ther study. It is readily grazed and herbage analysed at an early-flowering stage had 14 1per cent of crude protein in the dry matter. It is a prolific seeder and the seeds (one plump caryopsis per spikelet) are easy to harvest and handle. The grass is easy to esta'blish and established plants self-seed readily.

Enteropogon macrostachyus; BusH RYE (Fig. 7).-A tufted perennial, which may be leafy or stemrny depending an the environment. lt is nearly always weil grazed by stock and is a valua'ble gvass of serni-arid areas, occurring aJt altitudes from 1,000 to 5,000 ft., mostly in bushland or glades and often on rocky ground. Good seeding stands occur in Acacia/Commiphora bushland between Sultan Hamud and Voi, aJnd locally throughout the dry areas. E. macrostachyus is a very good seeder and seed can be collected rapidly by cutting the seed heads or

7 stripping the heads by band. The seed (Fig. 12, c and d) is in the form of spikelets, -each with a single large caryapsis. For seed quality and ra

Eragrostis cilianensis; G REY LovEGRASS.-An annual with greyish-green herb­ age, widespread in arid and semi-arid areas of Kenya. It is bath a natural dominant in the annual grasslands of northenn Kenya, under a 10-in. rainfall, and a pioneer whicb colonizes bare ground in higher rainfall areas. It is often extensive 'in overgrazed pererunial grassland. Herbage production fluctuates bctween w.ide extremes, dependent ün seasonal rainfall, but even rather stemmy herbage at the flowering stage can contain up to 15 per cent of eructe protein in the dry matter. E. cilianensis is a n efficient seeder, tbough the seed may be rather ted.ious to collect in large quantities. The seed is in the form of small, naked caryopses {Fig. 12 k). This grass is recommended primarily for reseeding in the annua1l grass zo.ne, particularly on alluvial soils. Eragrostis sp. nr. curvula.- A vigorous, tufted perennial, rather similar to E. chloromelas, but generally more p roductive and palatable. The nutritive value is rather .Jow as it is fibrous and may contain only 8 per cent of crude protein in the dry matter at the early-flowering stage. This grass was found near Nairobi and was introduced for seed bulking under the number K.5268: no extensive seeding stands are known. When cultivated in Naim bi it seeds weil, but elsewhere (as at Kita,J e or Marigat) seed productioo may be very poor. Harvesting is easy a.nd threshing and cleaning present no difficulties. The seed is a naked caryopsis.

8 ln view of its origin, it :is remarkably drought-tolerant and has been shown to be an excellent choice for red loa-ms at medium altitudes in Bar.imgo (Pratt and Knight, 1964). It well deserves trial under comparable conditions elsewhere. Eragrostis superba; MASAI LovEGRASS (Fig. 8).- A tufted perennial with leafy he 11 bage, widespread in the semi-arid areas of Kenya. lt forms Jess robust tufts than E. sp. nr. curvula but bas a bigber nutritive value, with about 12 per cent of crude protein in the dry matter at an early-ftowering stage. At this stage, the crude fibre content is a!bout 30-35 per cent. E. superba is persistent, palatable and bighly valued for reseeding under a wide range of conditions in moderately dry a•reas. Seed can be collected easily from open grassland or at roadsides by stripping the ripe paiil'ioles. Mature spikelets are detacbed witbout difficulty. The seed is in the form of large, fl at ~ pik e l ets , each with numerous ft orets (Fig. 12e). In contrast to nearly all the otber species of Eragrostis, the mature spikelets do not break into single ftorets and the caryopses rema-in enclosed in the spikelets. Only one or two, or occasionally tbree, caryopses are found in eacb spikelet, and a number will be completely empty. Winnowing is impracticable and the wbole spikelets should be sown as they are, with due allowance made when determini.ng the seed rate. E. superba has, with Cenchrus ciliaris, been the basis of the seeds mixtures used for large-scale reseeding in Kitui and Machakos (Jordan, 1957), and it has also been used successfully in Baringo. Provided it is not used under very dry conditions, it is one of the safest grasses available. Eriochloa nubica.-A leafy, erect annual of good grazing value whicb, even at the full flower~ ng stage, may contaùn 10 per cent of crude protein in the dry matter. It occurs througbout the dry areas but is best adapted to the heavier soils, on which ·it can be very productive, given good s~asonal rainfall or flooding. The seed is well formed, as is usual with annuals, and each spikelet contains a single caryopsis (Fig. 12 f), but it sheds easi!y and is therefore rather difficult to harvest. Particular effort should be made to include this grass when reseedi:ng alluvial flats which are situated in the arid zone but subject to sorne seasonal flooding. Eustachys paspaloides.- A perennial with short stolons, forming slow spreading colonies. The herbage is Ieafy, weil grazed and of fair nutr·i·tive value, containing about 10 per cent of crude protein in 11he dry matter at an early-ftowering stage. E. paspaloides is common in semi-arid areas, on both red and black soils. The flowering heads resemble those of Rhodes grass, though the branches of the digitate panicles are darker a nd shorter. Seed formation is erratic and consider­ able effort may be required to collect large quantities of seed. However, the seed (Fig. 12 i and j) is small and only two ounces of good seed are required to plant an acre at a rate of 100 spikelets per square yard. E. paspaloides bas never been tried for reseeding, but is of potential value for the medium rainfall areas of eastern Kenya. Latipes senegalensis; HooK GRAss (Fig. 9).- A small, sbort-lived perennial of tufted habit wbicb is widespread in arid and semi-ar·id areas. Its value is Iimited by its small size and fibrous, stemmy herbage of rather low protein content. It is, however, a:n efficient colonizer and it seeds well. Seeding stands are to be found throughout Machakos and southwards towards Voi. The seed is in the fmm of a short raceme of the panicle which at maturity can be easily stripped from the head. The raceme terminates in a curved point and has two spikelets, each with a single caryopsis (Fig. 12 h). Because of their irregular shape and the presence of hook•s, lihe seeds cling together, making bandling rather difficult. L. senegalensis was used by Brown in reseeding the Mwea area of Embu and the grass also featured in the Baringo reseeding experiments (Pratt, 1963 and 1964). For most conditions, better grasses are available, but L. senegalensis is a

9 useful grass for adverse conditions, where a minimum of site preparation bas been provided. Leptochloa obtusiflora (Fig. 10).-A tall, tufted perennial, commcm in the semi­ arid bushlands of Coast and Eastern Provinces up to 4,500 ft. altitude. The heribage varies in quality, but ·in the leafier types, the content of crude protein at the early-flowering stage cao be as high as 18 per cent of the dry matter, while the percentage 'Of crude fibre is less than 30 per cent. L. obtusiflora is Ml exceptionally good seeder and seed can be collected easily in the areas cited by hand-stri·pping the panicles. Cubting with sickles may result in considerable !osses, as the seed sheds easily when mature. Thirty to fifty plants are often sufficient to provide one pound of seed. The spikelets have severa! florets each, which at maturity break off to make the seed (Fig. 12 q and r). L. obtusiflora bas n'Ot yet been tried for reseeding, though in Kitui sorne of its seed was found in mixtures collected locally for reseeding. Its seeding rand grazing properties make it weil worth a trial throughout the semi-arid areas. Panicum coloratum; CoLOURED ÜUINEA GRAss.- A very complex species which, pending taxonomie revision, includes annual and perennial forms, of both tufted and stoloniferous habit. Although most types, including those commercially available, are insufficiently drought-tolerant for reseeding except under the most favourable conditions, there are tufted perennial types of local occurrence in northern and south-eastern Kenya which are both leafy and very drought-tolerant. One such variety from south of Lake Rudolph is at present being bulked at Marigat. P. coloratum is generally not a bad seeder and although its seed sheds rather early it is easier to harvest than most Panicum species. The seed, in the form of spikelets with a single caryopsis, are very easy to handle and to plant mechanically. Panicum m.aximum; ÜUINEA GRAss.- A large tufted perennial of excellent grazing value wbich is common throughout the semi-ar-id area, particularly in bushland. Seed is normally not worth collecting from wild stands, as in most types of P. maximum seed is only scarcely formed and most of the spikelets, often over 95 per cent, are empty. One seeding variety, collected by D. B. Thomas from Makueni, ihas been introduced into cultivation under the Katumani Experi­ mental Farm number P.5650 (K.6221). It produces good seed, though it is excessively palatable to birds and sheds very easily. The seed is in the form of single-grain spikelets with hard inner scales. This variety 'Of P. maximum can be recomrnended for inclusion in mixtures for areas receiving a rainfall of 25 in. or more per annum. P. maximum var. trichoglume (Slender Guùnea) is an equally good seeder and ·is available commercially, but it cannot be relied upon to persist where the average annual rainfall is Jess than 30 in. Paspalidium desertorum (Fig. 11).- A tufted perennial which, with Chrysopogon aucheri and the stoloniferous Dactyloctenium sp., is one of the few perennials to penetrate into the annual grass zone of northern Kenya. It bas numerous ascending stems with many nodes and long, narrow, somewbat succulent leaves. Tt is well grazed by cattle and analysis at an early-flowering stage showed a crude protein content of nearly 14 percent of the dry matter. This grass bas only recently been introduced for seed bulking and test, but it seeds weil and appears to be a very promising species for very dry areas, weil deserving a thorough trial. It is adapted particularly to heavy alluvia and may not do well on sandy soils. Sporobolus helvolus.-A stoloniferous perennial, relatively common on alluvial silts and clay soils in northern Kenya, where it occurs in place of star grass. It does not normally produce good seed, but is mentioned here because if seeding types could •be found it would be a most useful grass for the dry areas.

10 Sporobolus ?marginatus.-A very drought-tolerant perennial which differs from the normal stçrloniferous S. marginatus in forming robust tufts, with large, erect, bluish leaves. lt bas been introduced from Arba Jahan (Wajir). Although not yet proven, it seeds freely and deserves thorough trial. The seed is in the form of naked caryopses and spikelets with the caryopses loosely held in soft glumes. This grass is most likely to be of use for sandy soils, under a rainfall of less than 20 in. :per annum. Tetrapogon villosus.- A rather smail, tufted grass which, although no!'maily a perennial, often 'behaves as an annual, dependent on site and seasonal conditions. It is not very productive, but is well grazed and is adapted rto arid climates. It occurs in northem and eastern Kenya, though seldom is it very common. The seed is weil formed and easy to strip from the seed heads. The seed is in the form of spikelets, each wÏlth tlluee ftorets of different size. The spikelets are hairy and are not easy to handle, though the caryopses can be freed readily by thresh­ ing. lt is not yet known, however, whether the naked caryopses give an equally good establishment. T. villosus bas not been used for reseeding, tbough it may weil have a place under dry, sandy conditions.

Themeda triandra; RED ÜAT GRASs.-A weil-known tufted perennial, which occurs extensively in the better ranching areas of Kenya, on botb red and black soils. Seed is usually weil formed but harvesting is difficult as each plant produces a relatively small number of seeds whicb shed easily when ripe. The spikelets are large and awned and each contains a single caryopsis. When tbresbed, the caryopses a.re mixed witb a large proportion of cbaff wbicb is not easy to separate. If sufficient quantÏities of seed can rbe collected, it is very desirable to include sorne in seeds mixtures for the bigber rainfall an-eas, particularly at altitudes above 5,000 ft. Tricholaena eichingeri.- A tufted perennial of sandy soils and rocky places, locally common tbrougbout the drier areas. lit pr;oduces numerous thin stems beset with short leaves, but is weil grazed despite its wiriness and can bave a crude protein content of over 14 per cent of the dry martter at an early-ftowering stage. Fairly extensive stands can be found .jn southern Machakos. Seed produc­ tion is enatic, partly due to susceptibilirty to smut rattack, and the seed is shed early. This grass is very hardy, and would be an extremely useful species for reseeding poor, sandy soils and rocky sites, were better seeding types available.

CHo reE OF SPECIES The first criteri-on in selecting grasses f.or reseeding is thalt the species sbould be well-adapted to the environmenJt concerned. Wben a number of grasses are equally suitable for a site, preference will of course be given to tbose of wbich seed is easily and cbeaply obtainable, but availabilirty of seed sbould not be allowed to dictate the choice of species. lt is most important that the grasses should be cbosen primarily on their suirtability for the site. Table 1 indicates the rainfall and soi! requirements of each of the species described and this sbould be used as a guide to selection. Another question tbat arises is whetber to sow a single species ror use a mixture of grasses. As a general rule, grass mixtures are recommended, largely because ~ mixrture provides a better insurance against the hazard of unprediotable seasonal conditions, wbich might not favour full establishment of one species. A seconda•ry consideration is that mixtures allow the inclusion of bath stoloniferous and tufted grasses, ·the former to provide rapid oover and the latter to form the basis of the persistent grassland. ln praotice, almost any mixture can be satis.factory if :t con·tains adapted speaies, though it wiU best fulfil its function if it includes sorne species adapted to a drier climate rthan tbat being reseeded.

11 The main circumstance under which a single species might be sown is where plenty of good seed is available of a grass which is known l!o be persistent and reliable under the particular site conditions concerned. Cenchrus ciliaris, under sorne conditions, falls into this category. This grass forms a particularly good example because it is both an excellent grass for the drier areas and one which has definite establishment requirements (see p. 27). Where reliance is placed on a species having such definite requirements, there i,s much to be said for using it exclusively, as it is then poss~ble to give absolute priority to its individual needs.

SEED COLLECTION

Although it is preferable to establish seed production plots •and obtain seed supplies for reseeding from this source, it must be :accepted that in the immediate future the majority of seed will have to be collected from wild stands.

As most grasses require a post-harve~t ripening period of 1-6 months for satisfactory germination, seed should be collected weil in advance of requirement. Usually, natural sources of seed must be sought outside the area for which the seed is required. Perhaps the best areas for collecting seed of the commoner species, if more local sources do not exist, are in Eastern Province and the Coast hinterland. Provided that the rains have been satis.factory, 'Seed can be expected to ripen in these areas in June-July and in December-January. Seed of the less common grasses, particularly those from northern Kenya, is more difficult to obtain. ln recognition of this, the Range Management Division of the Ministry of AgricuLture maintains small bulking plots of the majority of these grasses.

In the pas!, much of the seed for reseeding was collected under self-help schemes. ln sorne areas, this approach could still apply; or it may be possible to persuade local people 'l.o collee! seed of chosen ·species at a priee of between 20 and 50 cents per pound. The alternative is a seed-collecting safari, with a mobile force of paid labour. ln ali cases, a reconnaissance survey is needed to locale suitable seeding stands, prefera'bly weil before the seed is ripe. Tsetse areas are usually weil worth investigéllting.

Seed yield and quality will depend on seasonal conditions. In annual species, good seed is produced almost invariably, although harvesting may be made difficult by carly seed shed. Perennials are normally shyer seeders than annuals and in unfavourable seasons they may produce no seed at ·ail. Cenchrus ciliaris is one species that is particularly unreliable in this manner. To judge the optimum stage at which to collect seed may not always be easy, but it is obviously of fundamental importance that seed should not be collected when still flowering, or left until most has shed. The notes given for individual species will help in this, but Î't is a field in which there is no substitute for persona! exper·ience.

Grasses that are particularly easy to collect in quantity are Eragrostis superba, Leptochloa obtusiflora and Ch/oris roxburghiana: one man can collee! sufficient seed of these species in one day 1o plant an acre or more. Collection is facilitated by using a collecting-bag attached to the waist, with its neck held open by a wire ring. Both bands are then free for picking or cutting seed heads.

Af,ter collection, it may be necessary to air-dry the seed before bagging it for storage. At the same time, an insecticidal powder can be added, so that when placed in store the seed is both dry and in sect-free. The store should be airy and dry, with the sacks kept raised from the ground, where they will be free from

12 attack. The seed should be inspected regularly {at !east every six months) and if necessary it should be re-treated with insecticide. Four months before use, a sample should be taken and sent for official seed test (see p. 21). Ripe seed of most species can be expected to increase in germination capacity over the first year after collection and to maintain its viability fOT aibout three years. Seed aider than six years is unlikely to be of any use, though species do, of course, vary in this respect. The effect of storage time on the germination capacity of caryopses is illustrated weil by the following data from Kongwa Pasture Research Station, Tanzania :-

A ge of Seecl Percentage Germination Capacity (Months) Cenchrus ci/iaris Ch/oris gayana Panicum sp. 1- 6 89.8 48.6 36.3 6-12 89.3 93.2 47.9 12-18 92.5 99.0 70.7 18-24 92.3 98. 4 81.8 24-30 85.4 93 .1 81.5 30-36 83 .2 86.8 77.5 36-42 80.0 90.6 77.1 42-48 77.1 82.6 66.8 48-54 70.7 87.4 60.2 54-60 59.5 79.7 52.0 60-66 52.8 67.8 45.0 66-72 42.6 45.6 30.5 72 -78 30.6 10.7 13.0 78-84 22.2 8.0 6.5 84-90 12.7 Nil Nil 90-96 4.1 Nil Nil

From K ongwa Pasture R esearch Station, R ecord of R esea rch, 1960-62 (typescript).

13 TABLE !.- GUIDE TO THE RAINFALL(SOIL REQUIREMENTS OF THE RECOMMENDED GRASS SPECIES

Recommended species and minimum rainfall requirement for *Soil type (cf. Table 2) Average annual reseeding (where applicable) Other rainfall Comments Species t Rainfall Loo se, Alluvial (in.) Loams --- sandy soils ------silts Bothriochloa insculpta .. 27 ++ + + Also black cotton soi!. Cenchrus ciliaris . . .. ++ + + + Ch /oris gayana .. .. 28 + ++ ++ Also l ava Single ash. season > 32in. Cynodon dactylon .. 27 ++ + ++ Tolerant of seasonal flooding. Double Echinochloa hap/oclada . . + ++ + season > 27 in. Eragrostis sp. nr. curvula + + + Panicum maximum . . ++ ++ ++ Th emeda triandra .. 27 ++ ++ + Also black ------cotton soi!. Cenchrus ciliaris . . .. ++ ++ ++ Cenchrus setigems .. + + ++ Ch/oris mossambicensis . . 23 + Ch/oris roxburghiana . . + + Cynodon plectostachyus 23 ++ + ++ Sorne al ka- li ne toler- ance. Single Echinochloa hap/oclada . . 24 + season 32-26 in. Enteropogon macros/achy- 23 ++ ++ + Good for sus rocky sites. Double . Eragrostis chloromelas . . 25 + + season 27-22 m. Eragrostis sp. nr. curvula 24 + ++ ++ Eragrostis superba .. 22 ++ ++ + Eustachys paspaloides .. 22 + + Also black cotton soi!. L eptoch/oa obtusif/ora .. 23 + + + Panicum maximum .. 24 + ---++ ----+ Cenchrus ci/iaris . . . . 18 + ++ + Cenchrus setigerus .. 18 + + ++ Ch/oris roxburghiana .. 20 ++ ++ Ch/oris virgata .. 18 + + + Chrysopogon aucheri .. ++ + + A Iso l a va Single ash. season 25- 20 in . Dactyloctenium sp. .. 16 + + + A Iso ash and a lk a line soils. Enterop3gon somalensis + ++ A Iso black cotton so i!. Double . Eragrostis caespilosa . . 20 + + season 21 - 15 m. Latipes senega/ensis .. + + + ' tPanicwn co/orawm .. + ++ 1 + Paspa/idium desert omm . . 15 + + Sporobolus he/valus .. 15 ++ Tolerant of scasona l flooding. Sporobolus ?margina/us ++ ++ ++ Tetrapogon vil/osus .. + + Tricho/aena eichingeri .. 20 ++ + Good for rocky sites. ---- Cenchrus pennisetiformis 8 ++ ++ ++ Chrysopogon auclzeri .. 14 ++ ++ + A Is o lava ash. Enteropogon somalensis 14 + ++ A Iso black Single cotton soi!. season < 20in. Eragrostis cilianensis .. 8 + + + Erioch/oa nubica . . 10 + ++ A Iso black cotton soi!. Double Latipes senegalensis . . 14 + + season < 15 in. tPanicum coloratum .. 12 + + + Sporobolus ?margina/us 12 + ++ ++ Tetrapogon villosus .. 14 ++ + + *For each soil type, the best adapted species are shown by + + and supplementary species by +. tThe limits given refer to the two -season rainfall a rea of eastern Kenya : for western Kenya and the Rift Valley (single season) , 5 in. should be added. tThis refers to the drought-tolerant type specified in the text, not commercial P. coloratum, wh ich could if required be used instead of P. maximum, where the rainfall is more than 27 in. 14 RESEEDING TECHNIQUE

Before embarking upon a reseeding programme, it is as well to be sure that the proposed course of action is in fact necessary. Essen1ially, reseeding is a practice for areas denuded of productive grass species. Should a nucleus of productive species still exist, then the introduction of grazing control will be sufficient in itself to restore productivity. Reseeding will accelerate the process, but it is not strictly necessary.

In assessing the need for reseeding, the state of denudation must be related to the ecological potential of the area. For example, the annual species present in an arid aJrea may represent the best that the area can support, but the same species when found .jn an area of higher potential may be indicative of severe overgrazing and the need for reseeding (see Plate 1).

If reseeding is confirmed as being necessary, then the aim must be to provide by the choice of adapted species and methods as great an insurance against failure as the economies of the operation permit.

In order to assess what constitute adapted species and meth-ods, a study of the basic site characteristics is necessary. Rainfall, soi! type, depth of soil and bush density are ail relevant; the first essen1ial being an assessment of the average annual rainfall and it distribution pattern. Where records from local rain gauges are lacking, the average Tainfall can be deduced from the vegetation type (though, as this requires sorne experience, specialist advice is recommended).

On the question of economies, it must be accepted that prevailing conditions in Kenya will normally necessitate the use of minimal-oost methods. Particularly ' will this be so in those pastoral areas where economie ranching bas yet to impinge. Wbilst 'the aJPproach adopted here gives full recognition to this fact, experience from other parts of the world leaves no doubt that grass establishment under low-rainfall conditions is not an operation that lends itself readily to compromise. It is to be hoped therefore that in time it will be possible to intro­ duce more efficient methods to replace those recommended, wi1h a greater safety margin. For an indication of the approach to reseeding adopted in more developed countJries, reference to the United States Department of Agriculture handbooks on reseeding is recommended (e.g. Plummer et al., 1955; United States Forest Service, 1951).

Reseeding should never be divorced from grazing control. Under no circum­ stance is reseeding a substitute for grazing control and to undertake reseeding without at the same time correcting the causes of the original denudation i's sheer foUy. Conversely, it is equally unrealistic to expect grazing control alone to effect any worthwhile improvement in the absence of a nucleus of productive grass species (see Plates 2 and 3).

These general remarks may ·be summarized by three maxims:-

(1) Evaluate the site in advance and be sure that reseeding is necessary.

(2) Aim to provide as great an insurance against failure as the economies of the operation permit.

(3) Do !llOt attempt reseeding unless control over grazing can be implemented.

15 CHOICE OF SITE

Having decided that an area is in need of reseeding, it may :be that no further choice of site is involved. However, if denudation is widespread, such a choice often exists: of the whole area, which sites should have priority?

Justification for reseeding may ,be sought in the expected economie return, in the arrest of land destruction or in sorne social or political advantage which would accrue. If reseeding is to be considered purely as an economie venture, a site naving a higher ecological potential is a better choice than one where aridity imposes a low limit on the stock carrying capacity. Not only will the financial return be higher, but the chances of ·success will lbe greater. In this connexion, it should be noted that the extent to which a site is degraded by erosion will most likely be of secondary importance to its climatic potential. In other words, it is often a better proposition to reseed an eroded site having a higher rainfall than an uneroded one with a low rainfall. This was demonstrruted clearly by the early Baringo experiments (Pratt, 1963).

ln view of the fact that reseeding is useless without grazing control, priority should be given to those sites where control can be best maintained. Also, if oniy part of a denuded area can be reseeded, priority should be given to the upper part .of the catchment area, to facilitate 1ihe spread of grass into the unseeded areas.

PREPARATION OF SITE In presenting this section, it has been assumed that site preparation and seeding will constitute separate operations, the seed being broadcast by band on a site that bas received the minimum of preparation. Whilst this is in keeping with the prevailing demand for low-cost methods, it does lead to sorne over­ diversification of technique.

If the capital outlay can be borne, reseeding can be much simplified by the use of an implement of the chisel-seeder type, which cultivates and sows in one operation. Although there will always be types of country where the use of a chisel-seeder is impracticable, even with pre-treatment to clear bush, this approach could be used satisfactorily under a wide range of environmental conditions and deserves consideration before alternatives are sought. In addition to its simplicity and versatility, mechanical drilling also provides optimum establishment condi­ tions for species such as Cenchrus ciliaris (see p. 27).

When adopting the mechanical approach, it must be appreciated that no normal agricultural seed-drill can cope simultaneously with the diverse types of seed present in most reseeding mixtures, nor, for that matter, with seed of a single species if it is fluffy and awned. However, specially designed machinery is obtain­ able, or can, with ingenuity, be constructed. At Kongwa, in Tanzania, where Cenchrus bas been established mechanically on extensive areas, a converted groundnut planter bas been used with good results. ln this case, the tractor exhaust was coupled to the planter and the seed blown down the chutes (an invention of A. G. Bates, then with the Tanganyika Agricultural Corporation). One implement which can handle the shorter-awned varieties of Cenchrus without -modification is the *Connor-Shea chisel-seeder.

*The Connor-Shea implement is mentioned specifically because the firm has a local agent: alternative machines are cited in the Appendix.

16 For those cases where site preparation and· seeding are undertaken independ­ ently, details on the individual aspects of site preparation are given below. Table 2 summarizes the conditions under which the various methods cited are applica~ble, ·on the assumption that the aim is to establish for least cost the highest form of perennial grass caver which the site can support. The requirements for esta:blishing an annual grass caver are very imperfectly known, though it is probable that a tine-cultivated seedbed, or Holt corrugations (see below), represent the maximum preparation necessary. Recommendations for specifie problem areas are given separatcly (p. 25).

Seed-bed Cultivation

Only very rarely is it permissible to attempt reseeding without sorne seed-bed cultivation. As a general rule, the degree of cultivation required will increase as the expected rainfall decreases. Scratch-ploughing, with ox-plough or band jembe, bas been a fairly standard practice, but there are many areas and circumstances where this is insufficient. "Red pavement" conditions, typified by much of Baringo, demand .for best results the use of tractor-drawn cultivators, whilst on drier loams and silts deep ploughing may be necessary in arder to obtain a reasonable chance of success.

Of the implements commonly used, the ox-plough needs no description. In the case of cul1ivators, a diversity of types is available (Pllllte 4). To obtain penetraJtion to 6 in. (a useful standard at which to aim), a heavy cultivator will usually be necessary, although the lighter (Category 1) types may be sufficient on loose soils. Spring-loaded tines have a greater shattering effect on the soil than rigid tines, though the latter have been used successfully under a variety of conditions in Baringo D istrict {Pratt, 1964; Pratt and Knight, 1964). A 15-18 in. spacing between tines can be recommended for general purposes, with wider or closer spacing under extreme conditions. For deep ploughing, a heavy dise is preferable. It is unlikely, however, that it would be economie to use such an implement in the drier areas of Kenya under present conditions, however necessary it may be. This fact should not be construed as meaning that a lesser form of cultivation should automatically be used; rather, it means that sorne areas cannat be reseeded undet prevailing economie conditions (se e Plate 9b).

A unique form of seed-bed is that left by the Holt Weed and Bush Breakers. These machines are particularly valuable where dense bush or rock outcrops· prevent normal tractor cultivation. A series of models of this trailed crushe-r bas been produced, ali to the same basic design but of increasing weight, with the common attribute of leaving soil corrugations or basins in their wake (Plate Sa). These corrugations catch and hold rainfall and concentrate seed and water together in a manner favouring good germination. Their basic failing is that, because the corrugations are formed more by compaction than by a loosen­ ing of the soil, the water they collect does not infiltrate into the root zone as readily as it does with true cultivation. Thus, unless the soil is loose and sandy and the rainfall more than adequate, the situation can arise where excellent germination is obtained, followed by the premature death of much of the grass through water shortage (Pratt, 1964). However, to sorne extent this fault can be overcome by the use of one of the heavier machines from the range, which leave deeper corrugations*.

• The depth of the corrugations is also dependent on tractor speed and a low working speed is necessary for maximum penetration. This is illustrated diagrammatically in Pratt (1964).

17 The latest madel, the "Holt Xa Bush Breaker /Basin Lister", bas been produced with reseeding particularly in mind and bas the corners of the crusher blades removed in order that the corrugations should rbe true basins, separate from those adjoining. At a gross weight of 7,168 lb., it requires a crawler tractor of the D.6 class to pull it, which does not make for ease of transport and operation. The "Holt IXa Bush Breaker" (Plate 8a), weighing 4,838 lb. and, operated by a _1).4, would be adequate for most circumstances, though it would need modifica- 'tion if true basins were to be obtained. Certainly, experiments wi:th the "Holt lXa" show it rto ·be a practical and efficient machine for restoring a grass cover to densely bushed areas under medium rainfall conditions (Pratt, 1966 and Plate 8). In time, it is to be hoped that a modified version of the "Holt IXa'' will be produced, manufactured to the same weight, but incorporating the Mark X blade design, with the angle at which the blades strike increased to a:bout 30° to reduce draw-bar pull. When faced with a large area that requires reseeding, it is tempting to spread the available resources by confining seed-bed preparation to contour strips. On capped ·soils .and under low rainfall, this is false economy, as it can take many years for the grass to spread into the uncultivated areas (see Plates 6 and 7). Also, a discontinuous grass cover is very susceptible to the rigours of climatic stress. Strip cultivation is mostly applicable where the soi! is sandy and the rainfall favourable, when a satisfactory spread of grass from the strips into the un­ cultivated area can be expected. It is also applicable where an attempt is being made under marginal conditions to introduce perennial species into an area carrying a good annual grass cover, with the aim of est.ablishing nuclei of perennials without unnecessarily reducing the existing cover. Any implement can be used, but the ox-plough and jembe are those most commonly associated with strip cultivation. With the ox-plough, single contour !ines can be ploughed at appropriate intervals (see Table 2). The jembe can be used 'to simulate this or to make crescent basins in series on the contour; or, on flatter land, to cultivate irregular patches of a few square feet each. Time of Cultivation Particularly where a tractor-drawn cultivator is used, there is a choice between cultiv.ating prior to or after seeding. The former is the more normal and is generally preferable, but the latter does permit the incorporation of the seed into the soi!, with obvious advantages in the case of light, fluffy seed. Seed of this type is very susceptible to wind blow and wash if left uncovered and there is evidence (Pratt and Knight, 1964) to favour the suggested variation to normal procedure, where the site is exposed and species such as Cenchrus ciliaris are concerned. The disadvanrtage of deferring cultivation until after seeding is that there is no precise control over the depth to which the seed is buried. It is preferable therefore to restrict this technique to conditions where shallow cultiva­ tion with a light tine-cultivator is permissible. Ideally, ,of course, seed that is liable to wind ·blow should be drilled into the soi!, irrespective of the climatic zone. Under marginal rainfall conditions, where the soi! bas a high rainfall accept­ ance and the ability to hold water reserves within the root zone, there is a case for allowing one season's fallow to follow cultivation, before seeding is attempted. The object of this is to build up soil moisture reserves during the fallow season, to supplement natural rainfall during the season of grass establishment. If during the fallow season the cultivated surface is likely to be weathered to a state where it is no longer effective as a seed-bed, the cost of re-cultivation would have to be offset against the value of the additional soil moisture.

18 Terracing On relatively flat sites with a receptive soil, a cultivated seed-bed is usually sufficient preparation for reseeding, but elsewhere, wherever heavy storms are a feature of the rainfall pattern, efficient contour banks (Plate Sb) form an essential supplement to seed~bed cultivation. Under most conditions, surface run-off can build up with frightening ease to give sheet flood flow; and in the absence of terrace banks, one intense storm following soon after reseeding can carry off virtually ali the seed, the sheet of water riding over even a cultivated surface.

The optimum size and number of banks are interrelated, and both depend on the slope and nature of the soil. The banks can be constructed either mechanic­ ally or manually, but if they are made by band, close supervision is required to ensure proper consolidation.

Where an extensive uncultivated catchment exists above the reseeded area, a decision must be made as to whether it is safer to construct a barrier to break any sheet floods, or to accept the extra water on the reseeded area together with the danger inherent in excessive wash. Except where the rainfall is low or the soil receptive, the former is the safer and more advisable course.

SEEDING Time of Seeding Seeding must be timed so that as much as possible of the expected effective rain falls during the period of grass establishment. This applies to ali sites except waterlogged clays, where it may be necessary to sow towards the end of the main rains. ln eastern Kenya, with two distinct wet-seasons each year, reference to existing rainfall records will usually show exactly when to reseed, but in the Rift Valley the date of onset of the rains is much more variable. With two seasons of equal reliability, it is preferable to reseed at the commencement of the short rains (normally October) as the dry season which follows is less severe than that following the April rains.

M ethods of Seeding If a mechanical drill is not used, it will be necessary to broadcast the seed by band. When the seed-bed is prepared by a tractor-drawn implement, it may be practical to arrange accommodation behind the tractor for one or two sowers, and so speed the operation, but otherwise sowing will be performed by a gang quartering the area on foot. The division of the area into strips of known acreage and the distribution of the requisite amount of seed between the number of sowers present bas been the method most commonly adopted. It is quite adequate, provided that supervision is given.

Where seed-bed cultivation bas been confined to strips across the contour, there is a choice between seeding only the prepared strips or broadcasting the seed over the whole area. The former represents the more efficient use of seed, but if there is reason to expect sorne establishment on the uncultivated areas, there is much to be said for overall seeding. A high proportion of the seed sown on ·the uncultivated areas which does not establish will in any event be washed into the cultivated strips. Seeding Rates The seeding rate should allow for the fact that only a small percentage of the seed sown will give rise to established plants. lnvariably, sorne seed will be lost by wash, wind blow, insects and birds, wbilst many of the seeds tbat remain

19 TABLE 2. EFFECT OF SITE CHARACTERISTICS 0 R ESEED ING TECHNIQUE, D ETA ILING MINIMUM REQUIREMENTS FOR P ERENN!AL GRASS ESTABLISHMENT

Soi! Conditions Average Annual Rainfall Loose, sandy soils Hard-capped loams Alluvial silts/clays - - Scratch ploughing, with jembe or ox- Complete cultivation with cultivator (a Scratch ploughing wi th ox-plough at 3-6 ft . plough, in spaced contour !ines; terraces light implement if cap not too hard) intervals, or cultivation with light culti- Single season > 32 in. .. usually essential. On leve! sites, eut or close working with ox-plough; ter- va tor; terraces essential. Cut branches branches alone may suffice. Pelleted races essential. With dense bush, the useful. The Holt IX would give a su itable seed useful for eroded sites. The Holt Holt IX would be ideal. seed-bed. Double season > 27 in . .. VIII or IX would give a suitable seed- bed, should bush density warrant its use. - - Scratch ploughing with ox-plough at 6-12 Complete cultivation with heavy cultiva- Close working with ox-plough, or corn- Single season 32-26 in. .. ft. intervals, or strip cultivation with tor; terraces essential. Cut branches piete cultivation with heavy cultivator; light culti vator ; terraces usually neces- desirable. Fallowing useful on drier terraces usually necessary. Cut branches sary. Pelleted seed can be used. Fallow- sites. The Holt X could be used . very desi rable. Fallowing very useful on Double season 27- 22 in . . . ing useful on drier si tes . The Holt IX drier sites. The Holt IX or X could be N would give a sui table seed-bed. used on wetter bushed sites. 0 -- Scratch ploughing with ox-plough at 3 ft. Complete cultivation with heavy cultiva- Complete cultivation with heavy cultiva tor, intervals, or complete cultivati on with tor, usin g close tines ( l ft. spacing) ; preferably using close tines ( 1 ft. Single season 25- 20 in. .. (preferably) heavy cultivator. Terraces terraces usually necessary. Cut branches spacing); ploughing may be necessary might be dispensed with under favour- and fallowin g both very useful ; also on drier sites. Terraces may be neces- D ouble season 21- 15 in . .. able circumstances. Cut branches very water-spreading. A Holt seed-bed wo uld sary. Cut branches extremely valuable; useful ; also fa llowing, if soi! retentive not be reliable. also water-spreading, and fallowing if of mois ture. The Holt X is a possibility rainfall accepta nee satisfactory. Holt for bushed sites. seed-bed generally too unreliable. - - Complete cultivation wi th heavy culti- Complete plough ing (ch ise! plough or Complete dise ploughing, or equivalent. vat or. Terraces rare!y necessary; eut dise plough) ; or complete cultivation Terraces may be necessary. Cut branches Sin gle season < 20 in . .. branches ex tremely valuable. Fallow- with heavy cultivator (using close tines) extremely valuable. Fallowing could be ing can be useful, but with low rainfall may be sufficient. Terraces may be useful. Without water-spreading, peren- may be wasted unless soi! conditions necessary. Cut branches extremely niai grass establishment is generally very Double season < 15 in . .. ideal. Holt seed-bed very risky. Water- valu able. Fallowing might be useful and chancy however thorough the prepara- spreading should be used if feasible. water-spreading should be used wher- tions, especially on true alluvial silts. ever feasible. . . N.B.- The need for terraces 1S determmed by mtens1ty of ramfall, SOI! type and slope, tt must be assessed mdtvtdually for each stte and the comments mcluded above are for guidance only. High-intensity storms are more a feature of western Kenya (single season) than eastern Kenya (double season). will fail to germinate due to poor formation, burial or exposure. ln ad4ition, there will be !osses at the seedling stage amongst those plants that germimtte in unJavourable sites. Ail such !osses must be èatered for in the seed rate.

A useful standard at which to aim is a total of one established plant per square 'foot, .or ten plants per square yard. Assuming for the moment that ali the seed in the sample is viable, how many seeds is it necessary to •sow in order to obtain this population? The evidence available indicates that the percentage of pure germinating seed that is recovered as established plants varies with site, season and species, but that a recovery of more than 10 per cent is the exception rather than the rule (Pratt, 1964; Pratt and Knight, 1964). With species such as Eragrostis sp. nr. curvula, it can exceed 50 per cent; whilst with Cenchrus ciliaris, it bas varied between 2 and 12 per cent. With this variation, it is diffi.cult to give a meaningful average, but an average recovery of 10 per cent is suggested as a basis for calculation, which requires that 100 seeds be sown per square yard to obtain ten established plants.

Table 3 gives the seeding rates for each of the grasses described in the previous section, calculated to provide 100 seeds per square yard. 1t will be seen that the rates va,ry from t oz. 1o 10 lb. per acre, dependent on the size and weight of the seed. Naturally, when severa! ·species are included in a mixture, the quantities will need proportionate adjustment.

Whrilst ail the a!bove calculations refer specifically to pure seed, seed as sown always contains a proportion of non-viable caryopses and usually sorne inert matter. It is therefore essential, if the correct quantities of good seed are to be sown, that ail seed should be tested before use. A lalbora·tory test, as conducted by the Seed Testing Unit of the National Agricultural Laboratories, Nairobi, is preferable, as this provides information on both purity and germination ability, the produot of which gives the percentage pure germinating seed, on whrich Table 3 is 1based.

If a laboratory test is impossible, the purity can be assessed in most cases by weighing a sample, blowing off •the empty seeds and spikelets, together with any chaff, and reweighing the pure seed that is left. In 1he case of grasses which have large spikelets enclosing a small seed, such as Cenchrus spp. and Eragrostis superba, 1his simple method of winnowing cannat be applied and it is necessary to take 200-400 seeds at random and examine them for the presence or absence of caryopses.

The germinating ability of pure seed can only be assessed accurately by test, but as a general guide it can be assumed that the germination rate for most East Afr:ican species is around 40 per cent. This, however, is a very erode yardstick which is subject to many exceptions. In Enteropogon macrostachyus, for example, germination often exceeds 70 per cent, whilst in Cenchrus setigerus, germination is poor and often delayed and 10 per cent is the maximum that can be expected in the season of planting. The seed rates suggested above should not be regarded as inflexible. Whereas ten plants per square yard is a reasonable initial population for the larger tufted perennials, the smaller perennials such as Latipes, or annual species, could be grouped more densely; whilst a Iow seeding rate would be permissible in the case of stoloniferous species which cover the ground quickly. Also, the recom­ mended rates allow for a 90 per cent wastage of seed, such as may be expected when the seed is broadcast on to a cultivated seed-bed and subject to the normal hazards .of wash, wind-blow, removal by insects or birds, burial and casual

21 TABLE 3.-SEED CHARACTERJSTICS AND RATES OF SOWING

Seed ra te p er acre Species Structure of seed Number of pure to plant 100 pure (as recommended for ·sowing) seeds per lb. seeds per square yard - -·------+------1------l------Bothriochloa and B. perfusa 550,000 1 lb. Cenchrus ci/iaris and .. 160,000- 2t-3 lb. C. pennisetiformis .. 180,000 Cenchrus setigerus . . 160,000 3 lb. Ch/oris gayana . . . . 900,000 8 oz. Ch/oris mossambicensis .. 750,000 10 oz. Ch/oris roxburghiana . . 3,000,000- lt-3 oz. 6,000,000 Ch/oris virgata . . Spikelet with one caryopsis ...... 900,000 8 oz. Chrysopogon aucheri A raceme with three spikelets, only one of them with a caryopsis 200,000- 2 lb. 250,000 Cynodon dactylon .. Floret wilh one caryopsis 1,000,000- 5-8 oz. 1,600,000 Cynodon plectostachyus . . Floret with one caryopsis 1,200,000- 4-7 oz. 1,800,000 Dacty/octenium sp. (perennial) . . Spikelet ...... 450,000 H lb. Loose caryopsis ...... 1,100,000 7 oz. Echinochloa hap/oclada .. Spikelet with one caryopsis ...... 380,000 tt lb. Enteropogon macrostachyus Spikelet with one caryopsis ...... • • • . 80,000 6 lb. Enteropogon somaleiiSis .. Spikelet with one caryopsis ...... 280,000 li lb. Eragrostis caespitosa .. N aked caryopsis ...... 18,000,000 t oz. Eragrostis ch/orome/as .. N aked caryopsis ...... 3,000,000 3 oz. Eragrostis cilianensis . . Naked caryopsis ...... 5,000,000 2 oz. Eragrostis sp. nr. curvula N aked caryopsis ...... 2,600,000 3 oz. Eragrostis superba . . Large flat spikelet with numerous florets but with only 1-2 caryopses .. 45,000 10 lb. Erioch/oa nubica .. Spikelet with one caryopsis ...... 500,000 1 lb. Eustachys paspa/oides Spikelet with one caryopsis ...... 3,500,000- 2t oz. 4,000,000 Latip es senega/ensis .. Short raceme of panicle with two spikelets, each with one caryopsis 160,000 3 lb. Leptoch/oa obtusiflora .. F loret with one caryopsis ...... 1,500,000 5 oz. Panicum co/oratum complex Spikelet with one caryopsis ...... 400,000- 1 lb. 500,000 Panicum maximum Spikelet with one caryopsis 330,000- l-It lb. 430,000 Paspa/idium desertorum .. Spikelet with one caryopsis ...... 550,000 1 lb. Sporobolus ?marginatus Naked caryopsis ...... 3,500,000 2-3 oz. Tetrapogon villosus Spikelet with 2- 3 caryopses ...... 175,000 3 lb. Themeda triandra .. Spindle shaped dark spikelet in hard scales .. 130,000 4 lb. Tricholaena eichingeri Hairy spikelet with one caryopsis . . . . 1,500,000 5 oz. Plate !.- Denudation and Ecological Potential

P late 1 (a).- Semi-desert country near Loperot, Turkana, with scattered Acacia reficiens and a poor ephemeral grass cover on stone-mantle. The conditions may look similar to those of the Frontipiece, but this a rea is not in fact seriously degraded and the establishment of perennial grassland on natural rainfall would be impossible. (Photo: Marc/1 1965 by D . J. Pral/.)

Plate 1 (b).- Acacia-Termina/ia woodland at Sabur, Baringo ; the site of the reseeding shown in Plates 2 and 3. T he unsccdcd forcground shows a com pletely denuded and highly eroded surface, but one on which pcrennial grasses can be estabUshed with relative case duc to a moderately high rainfall. (Photo: October 1958 by D. J . Pral/.) Plates 2 and 3.- Reseedin.• (Altitude 4,200 ft., averag

Plate 2 (a).- A general view of the Sabur site in April 1957, immediately before work commenced. With the exception of one shrub (Ipomoea) , denudation is absolute. The Terminalia tree in the centre has been lopped to provide browse. (Photo by D. J . Pratt.)

Plate 2 (b).- As above, but in December 1959, showing a satisfactory nucleus of sown perennial grass. The site had been grazed in April 1959 after two years' complete rest following seeding. (Photo by D. J. Pratt.) at abur, Baringo District annual rainfall c. 38 in .)

P late 3 (a).- An unsecded plot in December 1959 (witb seeded arcas in the ba ckground), showing the poor covcr of annual voluntcer grasses (mainly Aristida mutabi/is) that resultcd from protection a lone. (Pitoto by D. J. Pratt.)

P late 3 (b).- A eeded plot (adjoining that shown a bove and photographed at the same time), witb a good cover of C!tloris gayana, Eragrostis sp. nr. curvu/a, E. superba and Bothrioc!tloa inscu/pta. The seed had been broadca t on to an uncultivated urface that had the protection of eut branches. (Photo by D. J. Pratt.) Plate 4.- Reseeding Equipment

Plate 4 (a).- The Rockland Tiller: an example of a heavy tine-cultivator, designed and built by the U.S. Forest Service specifically fo r range seeding. (Ph oto by courtesy of Forest Service, U.S. Department of Agriculture, Wa shington, D.C., U.S.A.)

Plate 4 (b).- A rigid-tine cultivator (Ransomes C68 Toolbar with wide-spaced curved tines and P SF 1049 steel points) operating in Disperma, on the El Bata Plains, Samburu. This equipment, with close-spaced tines, was used extensively in the Baringo experiments. (Photo: June 1960 by D. J. Pratt.) Plate 5.-Seed-bed Techniques

Plate 5 (a).- Seed-bed prepared by a Holt Vlllb Weed Breaker on an alluvial site at Salabani, Baringo. The corrugations are about 5 in. deep. The seed-bed shown gave good germination but a poor final establishment. (Photo: May 1958 by D . J. Pratt.)

Plate 5 (b).- Establishment of sown grass (mainly Ch/oris gayana) in a contour terrace bank at Gobat, Baringo. A heavy rain-storm following seeding of tbe area above the terrace (to the left) washed off most of the seed, which would have been lost completely but for the terrace. (Photo: February 1961 by J . Knight.) Plates 6 and 7.-The Effect (Gobat, Baringo: altitude 5,200 ft.,

Pla~e 6 (a):- Fair _grass ~tablishment following com~lete cultivation with a rigid-tine culhvator (tme spacmg 18 m.). The sown grasses are mamly Ch/oris gayana and Eragrostis sp. nr. curvu!a; whilst Aristida mutabilis has volunteered strongly in response to cultivation. (Photo by J. Knight.)

•lf' '.; ..

Plate 6 (b).- Poor grass establishment following ox-ploughing, with plough-lines at 6 ft. intervals. There is sorne Ch/oris gayana and other sown grass, with a fair growth of Aristida mutabilis. of Degree of Cultivation average annual rainfall c. 35 in.)

Plate 7 (a).-Extremely poor grass establishment following ox-ploughing, with plough­ Iines at 12 ft. intervals. Nearly ali the grass visible is Aristida mutabilis. (Photo by J. Knight.)

Plate 7 (b). - An unseeded, unprotected area outside the experimental site, showing a lm ost complete denudation. This photograph was taken in November 1960; the remainder of the series in October 1961, eighteen months after seeding. (Photo by J. Knight.) Plate 8.- The Holt IXa Bush Breaker (Cheblesil, Baringo : altitude 5,200 ft. , annual rainfall 37 in.)

Plate 8 (a).- The Holt IXa in use in A cacia-Tarchonanthus thicket, pulled by an Allis Chalmers HD 5 fi ttcd with a front pusher-bar. (Photo: May 1958 by D . J . Pratt.)

P late 8 (b).- The Cheblesil site four years later. After Holt-trcatment and seeding (mainly with Ch/oris gayana) the site was burned in March 1960 and grazed periodically thereafter until J une 1962 when it was treated with a rotary slasher. T he transformation is obvious and the productive sown pasture is in active competition with the regcnerating Tarchonan­ rh us. (Photo: November 1962 by D . J. Pratt.) desiccation. Where precautions are taken which effectively reduce seed wastage, the rates suggested should also be reduced. If, for instance, the seed is drilled into the soil-which provides best protection-the seed rate cao safely be halved. Similarly, seed rates can be increased 1f wastage of seed is likely to be excessive, though on/y if the causes of the expected wastage are those noted above. An increased seed rate is not effective in countering wastage in the form of a high seedling mortality under low ·rainfall conditions. Losses of this nature are due to lack .of soil moisture, a condition which is determined by site characteristics and season and which can only be improved by thorough cultivation. An increased seed rate will only accentuate competition for moisture and cause an increase in the percentage mortality.

Table 4 illustrates the importance of correct seed rate and the manner in which rainfall determines the maximum population of plants that establish. Clearly it is a case of too much seed 1being as bad as too little.

TABLE 4.-EFFECT OF SEED RATE AND SEASONAL CONDITIONS ON SOWN ÜRASS ESTABLISHMENT (Numbers of established plants per square yard)

Pounds pure Seasonal Rainfall germinating 23- 24" 33-34" seed sown 7-8" 11-12" ] 5-1 6" per acre (a) (b) 5 0·10 0·45 0·58 1·03 ] ·25 3·08 10 0·80 x 2·41 3.83 x x 15 0·95 0·98 1·90 3·05 3·23 3-16 20 0·24 x ] ·30 2·04 x x (a) refers to average establishment and (b) to good establishment under 15-16 in. rainfall; x indicates no data available.

These data are derived from four of the Baringo experiments. As a constant seeds mixture was not used, the number of seeds contained in any one seed rate varies between seasons. Dependent on the seeds mixture used, 10-15 lb. of seed per acre was equivalent to between 41 and 107 seeds per square yard. The fact that the populations of established grasses did not exceed four plants per square yard does not mean that the suggested objective of ten plants per square yard is impracticable. The seeds mixtures used contained up to eight species, not ali of which were adapted to the sites concerned: consequently sorne completely failed to establish. Had adapted species been used exclusively, the final populations per square yard would have been greater.

SUPPLEMENTARY SEED PROTECTION It is not always sufficient to bring together the right seed and the right seed-bed at the right time; often, sorne form of supplementary protection must be provided to fully combat the hazards of harvester ants, of wind, wash and desiccation.

1nsecticides It is wise to treat all seed prior to sowing with an insecticide such as Aldrin. In view of the fact that new chemicals and formulations are constantly being released- and old ones withdrawn- speoific recommendations are omitted here, but up-to-date advice cao always be obtained from commercial representatives or from the Senior Entomologist of the Department of Agriculture.

23 If the site carries a high population of harvester ants, the ·danger should be attacked at its -source by treating the nests before reseeding. An insecticidal solution poured down the nests is the most efficient method, but it is sometimes easier to use a poison hait (e.g. posho soaked in Aldrin) scattered around- the nests.

Protection by insecticide is particularly necessary when low seed ra:tes are used; while species undoubtedly differ in their attraotiveness to insects (see p. 29 and Table 5).

Cut Branches Ii:J. most cases, eut branches laid on the soi! surface can be expected to assist grass establishment, particularly under low rainfall conditions. H is impossible to separate their various effects, for they at one and the 'Same time break the force of impact of raindrops on the bare soi!, reduce seed !osses by wind and wash, provide shade, and (later) protect the grass from grazing animais. Species vary in their response to eut branches, but unless there is direct local evidence to the contrary, their use should be an integral part of the reseeding operation (see also Tables 2 and 5). Where the site bas been "Holted", broken trees can if necessary be rearranged over the seed-bed after seeding; elsewhere, branches can be eut specifically for this puPpose, concentrating on the more noxious woody species

Pelleting of Seed An unusual form of seed protection, which is effective against both insects and wind, is the pelleting of seed, as tried experimentally in Baringo (Pratt, 1963). The pellets in the case oited were prepared by adding the grass seed to a thick paste consisting of two parts wet soi! (an alluvial silt) and one part borna manure, spreading this on 'a hard surface to sun dry and then breaking the resulting crust into the pellets. The pellets were about 0.4 in. thick and varied between 0.8 and 2.5 in. in diameter. A minimum of water and rapid drying are essential, and the pellets should be relatively large or they disintegrate or erode too quickly and their advantage is !ost. In other parts of the world, small pellets compounded of lime and fert-ilizer have been used, but these fulfil a rather different func-tion and are associated particularly with ae11ial seeding.

The earth~pellet technique is most useful where the soi! is loose and erodible, and a minimum of seed-bed preparation is included. It is virtually the only method whereby grass can be established on guily sides. However, under no circumstance should pellets be used on compacted soils with a hard cap, or wherever they cannot become rapidly integrated into the soi!.

Harrowing It might be thought that harrowing after seeding would be an efficient method of protecting the seed. In fact, under a semi-arid climate and with broadcast seed, it bas been shown that the harrowing of the seed-bed after sowing can reduce grass establishment very considerably or even cause complete failure (Pratt, 1964, and Plate 9b). In itself, the covering of the seed is not detrimental, but the over-riding necessity in a harsh climate is for a rough, broken surface, to aid rainfall infiltration and to sbield the seedlings from wind and sun. The use of a harrow after seeding should tberefore be restricted to relatively high rainfall areas (say over 30 in. per annum), where it can materially aid establishment of species such as Cenchrus ciliaris when the seed is sown broadcast.

24 SPECIALIZED TECHNIQUES FOR PROBLEM AREAS Dense bushland, shallow and rocky soils, dissected and billy terrain and an arid climate ail make reseeding especially difficult. Priority will be given initially to sites which can be reseeded most easily and profitably, but in time attention will need to be given also to the problem areas. Sorne techniques suitable for such areas are sugges:ted here. Only brief details are given of methods of bush­ control, as this is a subject in its own right which will, it is hoped, be covered by a separate bulletin.

Dense Bush/and or Shallow and Rocky Soifs

The use of a "Holt" machine is the first choice for these areas. The "Holt IXa Bush Breaker" is the mode! which bas widest application, and this bas already been described (p. 18 and Plate 8). lt is important to appreciate that Holting will not kiil the bush, but will merely reduce the canopy to ground leve! and provide a seed-bed. In ail likelihood, tbere will in fact be an increase in seedling trees (Pratt, 1966). lt is therefore essential that the need for regeneration- and seedling-control sbould be accepted before operations commence, and financial provision made for this. Sucb control migbt take the form of burning, chemical applications or band stumping, dependent on circumstances.

The alternative approach wbere dense busbland and a deep soi! occur together is eradication of the bush by bulldozer, root plough or chain, followed by cultiva­ tion with heavy equipment. Such an approach would also be necessary in low rainfall areas where the "Holt" seed-bed is unsatisfactory. The cost, in relation to the financial return, would be prohibitive, and rit will certainly be severa! years before extensive rehabilitation by such methods can be contemplated. In sorne circumstances, however, it may be feasible to reduce the operation to chaining or bulldozing, followed by .burning and aerial seeding into the ash mulch, as is practised in Australia. Glover, Trump and Williams (1959) give information and costs rela4ing to various mecbanical metbods of bush-clearing (see also Plummer, et al., 1955).

Where the ·site is excessively rocky, no machine can be expected to operate. Fortunately, such areas normaily carry a nucleus of perennial grass, even when the adjoining plains have been completely denuded; but if reseeding is necessary, ali tbat can be recommended is the band broadcasting of seed over 1be area. A proportion of sucb seed can be expected to estaoblish between rocks and in orevices which collect run-off and constitute relatively favourable sites for grass establishment. Where rocky sites are also densely bushed, little can be profitably accomplished without recourse to aerial metbods of bush-control by arboricides. These bave still to be developed.

Dissected and Hilly T errain Sites tbat are severely gullied are difficult to work mecbanically, even if adequate soi! remains between the gullies. Short of bulldozing the area into shape, seed-bed preparations will have to be done by band jembe. On sloping land, the preparations will need to include contour terraces and basins to control run-off. Pelleted seed is indicated for loose, erodible soils and roots of star grass (Cynodon spp.) sbould be planted in guily bottoms. Such techniques will normally be permissible as severe gullying is typically associated witb moderate or high rainfall. lt is better to defer the planting of star grass in gully bottoms until after the reseeding of the main area bas been accomplished and a grass cover exists (Jordan, 1957).

25 Hilly terrain i:s usually also rocky, and often densely bushed. It is recom­ mended that areas in this condition be left undisturbed until such time as it becomes feasible to use aerial methods of bush-control and reseeding. Lightly bushed, rocky billsides can be reseeded by band if required, in the manner outlined for shallow and rocky soils.

Arid Areas Because of their limited potential, arid areas have a low priority for rehabilita­ tion. Nevertheless, approximately half of Kenya receives a rainfall of Jess than 15 in. per annum and this vast area cannot be ignored indefinitely.

The establishment of perennial grasses under minfalls of Jess than 20 in. per annum requires careful planning and thorough seed-bed preparation. As the expected rainfall decreases, the point will 'be ·reached where the expense of pro­ viding the necessary conditions is •proh ~ büive. Under these circumstances, it is possible that the expense of the operation can be reduced by sowing predomi­ nantly annual species requiring less rigorous cultivation and protection. Information on the requirements of annual species is, however, very limited and more work is urgently needed, both to test the practicability of this approach and to formulate recommendations for the true annual grass zone. For very arid conditions, grasses are needed with seed which germinates sporadically and which can if necessary lie dormant in the soil for at !east 18 months.

Techniques of water-harvesting and water-spreading have a particular part to play in the rehabilitation of arid areas (see Table 2). Both of these techniques aim •to bring extra water on to a site rto supplemenrt: 1he natural rainfall; the distinction is that "harvesting" refers to any system where water is gathered-in and concentrated on to a site, whereas "spreading" applies specifically where an existing concentration of water (the flood flow of a water-course, or water in storage) is taken and spread over the adjacent land.

Water-harvesting can be applied independently or as a preliminary to water­ spreading. In the former case, it can be used to assist grass esta~blishment either on hill slopes, by constructing a barrage of contour basins to collect, retain and control the flow of run-off, or, under conditions of extreme aridity, by con­ centrating water into natural depressions and making these the foci for increased grass production. The fallowing of a cultivated area prior to seeding (see p. 18) may also be regarded as a form of water-harvesting, though this is a technique which can be unreliable under arid conditions unless the site also collects run-off from an adjoining catchment.

Where harvesting and sp reading are combined, the object of the harvesting is to lead run-off water into storage reservoirs for ·release for spreading later. In the context of reseeding, this combination is of greatest value in arid areas of unreliable rainfall, where sown grass may germinate in response to the first rain but fail to establiiSb for want of sufficient rain at the rigbt time thereafter. If suitable storage for water bas been provided, the rain that germinates the g·rass will also fill the storage; and should there then be insufficient rain in the weeks following, the stored water can be relea·sed for spreading and ISO ensure establish­ ment on the area commanded. If the storage area is lGI!rge, it may even be practicable to grow a forage or otber crop on it .once the water bas been released*.

* These techniques are being developed in Queensla nd, Australia, by the D epartment of Primary Industries.

26 Although water-spreading can be based on stored water, the more normal system, and that of greatest application, is the utilization of the flood-flow of seasonal water-courses. Many of the arid areas of Kenya are dissected by water­ courses that flood at ]east two or three times a season; and carry to waste an intoleraJble quantity of water. The practicability and cost of diverting this water, and the extent to which terrace ·banks are necessary for optimum spread, can be determined only by s urvey~but the benefits can be so great {Plate 10) that the water-spreading rpotential of ali arid sites should be investigated before any rehabilitation programme is formulated.

Further information on water-spreading in Kenya ~s given by Fallon (1963) and details of techniques in use in the U.S.A. by Stokes, et al. (1954).

SPECIES / TREATMENT INTERACTIONS

The Ba ringo experiments (op. cit.) show that grasses differ markedly in their reaction to treatments such as cultiva11ion, rpelleting, the provision of eut branches and seed dressing with an insecticide. Pa ssing reference only bas been made to this aspect because the requiremen:ts of species can be expected

Although confirmation under different environmental conditions is necessary, certain general assumptions can

Of equal importance to the effect of environment are the reasons why species should react in the manner reported. With this knowledge, it would be possible to predict the likely reacrtion of other species. At present, the following tentative conclusions must suffice :-

(1) In species with large but fluffy seeds, such as Cenchrus ciliaris, the incorporation -of the seed with the soil prevents !osses through wind and wash; and also facilitates the absorption of the moisture necessary for germination, wbich the nature of the seed coat otherwise tends to hinder. The latter factor would seem to be the more important in the ca:se of C. ciliaris, for eut branches, which should reduce !osses through wind and wash, have little effect. It is probably also important in the ca•se of ha;rd-coated seeds which lack bairs or bristl es.

(2) Species that require a culitivated seed ~bed , but which do not respond to seed c-overing, can be classified as "normal", having smaller, denser seeds which can effectively absorb moisture.

27 TABLE 5.-EFFECT OF SEED- BED TECHNIQUE ON THE ESTABLISHMENT OF CERTAIN GRASS SPECIES (from Pratt, 1963 (1), 1964 (2) and Pratt and Knight, 1964 (3))

Species Cultivated seed-bed Cut branches on soi! surface PeUeting of seed Insecticidal seed dressing (Aldrin) - - - Bothriochloa insculpta Sorne response un der low No response (1 , 2). Marked negative response (1 ). (lnsufficient data) rainfall, otherwise none (1, 2, 3). Cenchrus ciliaris Very marked response. Res- Little or no response (1, 2, 3). Little or no response (1, 2). Sorne response at low seed rates ponds also to covering of (2, 3). seed (2, 3). Ch/oris gayana No response (1, 2, 3). Marked response under low Little or no response (1, 2). Normal! y sorne response (2, 3). rainfall (1 , 2, 3). Ch/oris roxburghiana Sorne response un der low Sorne response under low (Insufficient data) (lnsufficient data) rainfall (2). rainfall (2). - Enteropogon macrostachyus Fairly rnarked response (2, 3). (lnsufficient data) (lnsufficient data) Someresponse at low seed rates (2). Eragrostis sp. nr. curvula Marked response (1, 2, 3). Variable, but normally sorne Marked response, at !east under Fairly rnarked response (2, 3). response (1, 2, 3). moderate rainfall (1). Eragrostis superba Very rnarked response (1 , 2, 3) No response (1, 2, 3). Varied response, sornetimes Little or no response (2, 3). Better than average estab- ma.rked (1) and sometimes lishrnent on Holt seed-bed (2). none (2). Latipes senega/ensis No response (1, 2). Little or no response (1, 2). Negative or no response (1, 2). No response (2). (3) Species with seed whicb, by virtue of its angular or awned nature, bas the albility to ancbor or bury itself, may show no response to cultivation, provided :tbat the species are also to sorne extent xerophytic. On this tbesis, the reaction of Latipes senegalensis is explicable. But no explanation can be given .for the consistent Jack of response in Ch/oris gayana, unless it is con­ cluded that on a cultivated surface the seed is very easily buried beyond optimum germination depth.

(4) No generalizations can be made on the relation between seed type and the response to eut branches and pelleting. Light seed, which is the most susceptible to wind and wash, sbould respond to the protection of both, though in practice this is not an invariable rule. Species which at the seedling stage have soft leaves sensitive to sun scorch and low bumidity (? Ch/oris gayana) can be expected to respond to eut branches.

(5) Species witb seed in the form of a small, plump grain, such as Eragrostis sp nr. curvula, are particularly susceptible to insect damage. Other species wi,th seed of this type are the orher Eragrostis species (excluding E. superba), Dactyloctenium sp., Eustachys paspaloides and Sporobolus spp.

It sbould not be thought that the type of interaction reported is of academie interest only. The magnitude of the responses can be very great, as is illustrated by the example given below, 'whicb refers to a reseeding experiment in North Baringo. The figures represent populations of establisbed plants per 50 sq. yd.

Seed-bed prepared No seed-bed by tine-cultivator cultivation

Cut No eut Cut No eut branches branches branches branches

Chloris gayana ...... 160 58 205 74 E ragrostis superba ...... 298 281 77 30

Clearly, individual species requirements is an aspect of reseeding weil worth furtber study.

GRAZING MANAGEMENT

1t is boped tbat sufficient emphasis bas been given to indicate the foUy of attempting to reseed over-grazed land without first reducing the livestock popula­ tion and introducing grazing management. This section is concerned primarily with methods of achieving control, both during establishment and subsequently. It is appreciated tbat stock reduction and control is a perennial problem of many pastOTal areas of Kenya, and one of the most difficult to solve, but unless grazing control is enforced there can be no place for reseeding and little future for the rehabilitation of these areas.

29 During the season of estaJblisbment, at least, protection from grazing must be complete. The actual period which should elapse before stock are introduced will, of course, depend on rainfall and the success of establishment, but often 1t will be necessary to allow a second season to pass before grazing is allowed. Should there be any possibility of stock obtaining access to the reseeded area during the period of closure, a perimeter fence should be constructed. For most purposes, a well ~built thorn fence will suffice.

The greatest difficu!Jty in ensuring complete protection will occur on communal grazing areas, where there is no division into fenced paddocks. Under these circumstances, control can best be enforced within the framework of a controlled grazing rotation, the establishment of which bas already become a feature of land rehabilitation in many pastoral areas of Kenya. If the area to be reseeded is subject to a grazing system of this type, it may well be possible lto fit the operation within the rest periods which the rotation provides, without addi.tional protection or fencing. W·ith the systems currently most popular, •the rest periods so provided are of one year's duration and intersperse grazing periods of from three to six months. In eastern Kenya, with two growing seasons per year, one year's rest should ·be sufficient for satisfactory establishment, provided that rainfaU is average and adapted grasses have been used. In western Kenya, with one extended season, it would be more chancy, and for ensured success a relatively high rainfall would be necessary. Certainly, strict adherence to the grazing system would be an essential of success, as experience in the Goba,t Grazing Scheme of Baringo illustrates (Pratt and Knight, 1964).

Where a four- or five-block rotational system is operating in an extensively denuded area, an alternative approach could be to excise one block from the grazing rotation for two years, during which time intensive rehabilitation could be accomplished, whilst the cattle rotated between the •remaining blocks of the scheme.

One of the major advantages of coupling reseeding with the use of a rotational grazing system is that proper grazing-use after establishment is thereby assured, provided only that the stocking rate is kept within the actual grazing capacity of the land. It should be understood, however, that formai rotational systems are not suited to the very dry areas, where the rainfall is less than 15 in. per annum.

In sorne areas, wildlife constitutes an additional hazard. Depending on the size of the reseeded area and the concentration of grazing species, fencing or permanent guards may be necessary. Usually, however, the liberal use of eut branches, spread over the seeded area, will be sufficient. Frequenltly, invasions by game animais are a seasonal phenomenon and it may be possible to discourage dry-season concentrations in the vicinity of the reseeded area by rendering inaccessible all local watering points. With species such as oryx, which very seldom drink, this approach would of course be impracticable.

If a quantity of eut or broken bush bas been left on the site, it is desira~ble to burn the reseeded area once a grass cover bas lbecome well established. In this event, protection from grazing should be provided up to the time of burning, and for as long afterwards as it takes the grass to recover. Great care should be taken when using fire in areas with a rainfall of Jess than 20 in. per annum.

30 REFERENCES

BOGDAN, A. V. (1958). "A revised list of Kenya gr:asses" Nairobi, Governmem Prin ter. DouGALL, H. W. and BoooAN, A. V. (1958). "The chemical composition of the grasses of Kenya-l". E. Afr. agric. J. 24, 17-23. ----(1960). "The chemical composition of the grasses of Kenya-ill". E. Afr. agric. . J. 25, 241-244. ---- (1965). "The chemical composition of the grasses of Kenya-JII" E. Afr. agric. For. J. 30, 314-319. FALLON, L. iE. (1963). "Water spreading in Turkana". Nairobi, United States A. I. D. Mission to Kenya. GLOVER, P. E., TRUMP, E. C. and WILLIAMS, R. '(1959). "Note on mechanical bush clearing". E. A/r. agric. J. 25, 18-22. JoRDAN, S. M. {1957). "Reclamation and pasture management in the semi-arid areas of Kitui District, Kenya". E. A/r. agric. J. 23, 84-88. PLUMMER, A. P., HULL, A. C., STEWART, G. and ROBERTSON, J.H. (1955). '·'Seeding rangelands in Utah, Nevada, Southern Idaho, and Western Wyoming''. U.S. Dept. Agric., Agric. Handbook No. 71. PRATT, D . J. (1963). "Reseeding denuded land m Baringo District, Kenya". E. Afr. agric. For. J. 29, 78-91. --- - (1964). "Reseeding denuded land in Baringo District, Kenya-II. Techniques for dry alluvial sites". E. Ajr. agric. For. J. 29, 243-259.

- - --(1966). "Bush-control studies ~n the drier areas of Kenya-II. An evaluation of the Holt IXa Bush Breaker in Tarchonanthus / Acacia thicket". J. appl. Ecot., 3, 97-11 5. PRATT, D. J. and K NIGHT, J. (1964). "Reseeding denuded land in Baringo District, Kenya- III. Techniques for capped red loam sites". E. Afr. agric. For. J. 30, 117-125. STOKES, C. M., LARSON , F. D., PEARSE, C. K. et al. (1954). "Range improvement through waterspreading". Washington, U.S. Govt. Printing Office. VAN RENSBURG, H. J. (1958). "Guily utilization and erosion control". E. A/r. agric. J. 23, 190-192. UNITED STATES FoREST SERVICE (1951). "Handbook of range reseeding equip­ ment". Washington, U.S. Dept. Agric.

31 APPENDIX

Catalogue or Proprietary Machinery and Seed Suppli~rs This list is for guidance only: inclusion implies no guarantee and exclusion no disrespect.

MACHINERY l. Tine Cultivators (including "tillers" and "chisel ploughs"): - (a) Rock/and Tiller (Plate 4a).-A heavy trailed cultivator designed by the U.S. Forest Service for range seeding, with compression spring tines mounted on three cross beams: overall width 9 ft., wi1h one tine every 6 in. Plans for manufacture obtainable from United States Department of Agriculture, Forest Service, Washington D.C., U.S.A. (b) Napier Heavy Duty Toolbar, with three-point linkage, available in 8 ft. (AF-A, B) and 9 ft. 6 in. (AF-C) models, with adjustable rigid or stump­ jump tines. Manufactured by Napier Bros. Ltd., Dalby, Queensland, Australia; Agents Hughes Ltd., P.O. Box 30060, Nairobi. (c) Connor-Shea "Chisel-Plow".-Availab!e in 5 and 7 ft. (mounted) and 9 and 13 ft. (trailed) models, with adjustable rigid or stump-jump tines. Manu­ factured by Connor, Shea and Co. Pty. Ltd., Sunshine, Victoria, Australia; Agents G. North and Son (Pty.) Ltd., P .O. Box 30085, N airobi. (d) Massey-Ferguson "544 Heavy Duty Field Tiller".-A 2,079-lb. implement for rear mounting, with five rigid or coil-spring tines: overall width 9 ft. Manufactured ·by Massey-Ferguson Ltd.; Agents Farm Machinery (Distributors) Ud., P.O. Box 18073, Nairobi. (e) Ransomes "C79" Zed-bar, with three-point linkage, available in 8 ft. 10 in. or 10 ft. 6 in. models, with adjustable rigid or stump-jump tines; or Ransomes "C68" Heavy Duty Toolbar, with adjustable rigid tines (see Plate 4b); or, rfor surface scarifyi ng on loose soils; Ransomes "C74" Toolbar, with 7-11 spring-loaded tines ~work ing width 9 ft. 8 in.). Manufactured by Ransomes, Sims and Jefferies Ltd., Ipswich, England; A gents Gailey and Roberts Ltd., Machinery Services, P.O. Box 30342, Nairobi. Mention may also be made of the Sapper "Superflow" Mounted Cultivator and Brown's "Panbuster" Chisel Plough, details of which can be found in N.I.A.E. Reports 306 and 357. 2. Heavy-Duty Dise Ploughs and Offse t Dise Harrows.-Many of the above manufacturers (e.g. Ransomes, Connor-Shea) offer heavy-duty dises. There is also the "Brushland Plow", designed by the U.S. Forest Service. As the immediate demand for such machines is likely to be limited, details are omitted and refer­ ence should be made to the manufacturers or agents for information. 3. "Ho/t" Bush and Weed Breakers (a) Hait VI/lb Weed Breaker.- A si ngle crusher unit, rear mounted, with a working width of 5 ft.; weight 1,400 lb. (see N.I.A.E. Report 174 (East Africa)). (b) Hait !Xa Bush Breaker.-A trailed three-gang unit, with a working width of 11 ft. ; weight 4,838 lb. (see N.I.A.E. Report 190 (East Africa) and Plate Sa).

32 (c) Holt X a Bush Breaker f Basin Lister.- A trailed three-gang unit, with truncated blades leaving individual corrugations or basins; working width 11 ft. and weight 7,168 lb. (If required Holt rollers can be combined in five-gang as weil as three-gang units). Ali models manufactured by The Holt Weed Breaker Company, Kirbymoorside, York>S hire, England; Agents Wigglesworth and Co. (Africa) Ltd., P.O. Box 30092, Nairobi.

4. M echanical Seeders.-Normal agricultural drills can handle seed of species such as Rhodes grass; those Jisted below are designed specifically to cope with awned seed of the Cenchrus type: - (a) Connor-Shea Seeder, for fitting to the Connor-Shea "chisel plow"; or the two may be bought as one unit, viz. the 5 ft. (mounted) or 9 ft. (trailed) "chisel seeder". An agitator chain is driven off the plough wheel. Manufacturers and Agents as for 1 (c). (b) Shearer "All-Seed" Planter, with agitators driven off a trailed wheel, or Napier "All-Seeder" , with a V-belt drive, ·both for fitting to most cultivating 1mplements. Manufactured, respectively, by John Shearer and Sons, Ltd., P.O. Box 81, Toowoomba, Queensland, Australia, and Napier Machinery Sales Pty. Ltd., Dalby, Queensland, Australia; Agents not known. (c) Power Broadcasters.- The U.S. Forest Service (see 1 (a)) have specifications for severa! types of power broadcaster which, fitted behind the tractor, will scatter seed from a hopper in a swath of up to 14 ft.

SEED SuPPLIERS Most of the grasses described in this bulletin are not available commercially, but seed of Rhodes grass (Ch/oris gayana), sorne Guinea grasses (e.g. Panicum coloratum and P. maximum var. trichoglume) and occasionally other grasses such as Cenc/u·us ciliaris, are obtainable from one or other of the following suppliers: - Dalgety (East Africa) Ltd., P.O. Box 13, NAKURU (or order through any branch office). Kenya Seed Co. Ltd., P.O. Box 553, KITALE. K.F.A. (Co-op.) Ltd., P.O. Box 35, NAKURU (or order through any branch office). Kirchhoffs East Africa Ltd., P.O. Box 30472, NAIROBI. Simpson and Whitelaw Ltd., P.O. Box 42, NAIROBI.

33 ILLUSTRATIONS OF GRASSES

(by A. V. Bogdan)

Figure Bothriochloa insculpta 2 Cenchrus ciliaris 3 Cenchrus pennisetiformis 4 Ch/oris roxburghiana 5 Chrysopogon aucheri 6 Dactyloctenium sp. (perennial) 7 Enteropogon macrostachyus 8 Eragrostis superba 9 Latipes senegalensis lO Leptochloa obtusiflora Il Paspalidium desertorum 12 Seeds of range grasses: Bothriochloa insculpta- p, spikelet as sown; Cenchrus ciliaris-a, cluster of spikelets as sown & b, caryopsis (grain); Ch/oris roxburghiana--n, spikelet & o, caryopsis as sown; Dactyloctenium sp.- l, caryopsis & rn, spikelet (either may be sown); Enteropogon macrostachyus-c & d, spikelet as sown (side and back view); Eragrostis cilianensis-k, caryopsis as sown; Eragrostis superba-e, spikelet as sown; Eriochloa nubica-f, spikelet as sown; Eustachys paspaloides- i, caryopsis & j, spikelet as sown; Latipes senegalensis-h, raceme with two spikelets (seed as sown); L eptochloa obtusifl ora-q & r, floret as sown (back and side view); Paspalidium desertorum-g, spikelet as sown. (Each measure = 1 mm.)

34 Fig. 1.- Bothrioch/oa insculpta Ct na lural size) 35 \

Fig. 2.-Cenchrus ciliaris (t natural size)

36 Fig. 3.-Cenchrus pennisetiformis Ct natural size)

37 Fig. 4.-Ch/oris roxburghiana (t natural size)

38 Fig. 5.-Chrysopogon aucheri (t natural size)

39 Fig. 6.-Dacryloclenium sp. (perennial) (t natural size)

40 Fig. 1.- En!eropogon macroslachys (i natural size)

41 Fig. 8.-Erogrostis superba (t natural size)

42 Fig. 9.-Latipes senegalensis (f natural size)

43 •W"""""- o-,.. '• ·~ '"" "-,., ~ ., ., .•-1- ~ . .ri"'?"L-..~ '\·-..\ -,

J --··'

Fig. 10.-Leptoch/oa obtusif/ora (-! natural size)

44 \ \ l '~

~ F ig. 11.- Paspa/idium desertorum Ct n ~t ura l size) 45 \

I e

I

I

1

Fig. 12.-seeds of range grasses-see p. 34 for key 46 Plate 9.- The Njemps Flats, Baringo District (Altitude 3,300 ft., average annual rainfall 25 in.)

Plate 9 (a).- The result of reseeding the country illustrated in the Frontispiece. The photograph is taken seven months after broadcast seeding on to a seed-bed closely cultivated with a rigid-tine cultivator. (Ph oto: November 1958 by J . Knight.)

Plate 9 (b).- ln dry years on the Njemps Flats, tine-culitvation may be insufficient seed-bed preparation. The plots shown above were seeded in April 1961, those in the left-hand photograph having been prepared by disc-plough and those in the right-hand photograph by cultivator. The patchy establishment in the foreground of both photographs is the result of harrowing after seeding: the only treatment to give a good stand of grass was disc­ ploughing without harrowing (Ieft background). (Photo: November 1961 by J. Knight.) Plate 10.-Water-spreading

Plate 10. A vigorous stand of Cenchrus ciliaris, C!Jloris roxburghiana and Eragrostis superba established at Lorengipe, Turkana with the aid of water-spreading. Eighteen months earlier, this area supported only very scattered annual species and the increase in grass productivity can be estimated at about 3,000 percent. (Photo: Seprember 1964 by D . J. Pratt.)

GPK 6079-lm- 8/66