Effect of seedbed methods and time of harvest on the yield and nutritive value of some forage crops grown on Vertisol at Debre Zeit, Ethiopia Abate Tedla, Helena Airaksinen and M.A. Mohamed-Saleem Tedla, A., Airaksinen, H. & Mohamed-Saleem, M.A. 1992. Effect of seedbed methods and time of harvest on the yield and nutritive value of some forage crops grown on Vertisol atDebre Zeit, Ethiopia. Agric. Sci. Finl. 1:491-497. (International Livestock Centre for Africa (ILCA), P.O. Box 5689, Addis Abeba, Ethiopia.) The influence of the improved drainage broadbed and furrow (BBF), as opposed to the traditional flat seedbed over the growing season on the dry matter yield and nutritive value of A vena sotiva, Vigna unguiculata, Lablab purpureas , Vida dasycarpa, Trifo- lium steudneri and Seshania sesban were studied on Vertisol. Up to 7 t/ha dry matter yield was recorded for Avena sotiva and Lablab purpureus when planted on Vertisols with improved drainage. Dry matter yield of forage crops also increased with advance in stage of maturity or subsequent harvests. On both improved and traditional flat seedbed methods, the chemical analysis of forage crops showed similar declines in crude protein content and in vitro dry matter digestibility (IVDMD) levels as the maturity of forage crops progressed. Key words: Ethiopian highlands, Vertisols, forage legumes,Avena sotiva Introduction Integrated crop-livestock production is a long tradi- tion in the Ethiopian highlands (above 1500 m alti- tude). Livestock provides draught power for tillage and transport and manure for crops while crop residues serve as important feed resources (Gry- SEELS 1988). Vertisols (deep clay soils) in Ethiopia cover about 12million ha; 7.6 million ha are found in the highlands. Only about 2 million ha of Vertisols are under cultivation in the highlands. The remainder is not cropped because of waterlogging caused by high rainfall amounts (JUTZI 1986). The traditional flat seedbed method is generally used on Vertisols by farmers. However, it cannot effectively overcome the problem of waterlogging (Berhanu 1985). Research at the International Livestock Centre for Africa (ILCA) on animal trac- tion showed that the development ofan appropriate animal drawn implement (broadbed maker) for seedbed-shaping helped to overcome the problems of waterlogging. The broadbed maker forms the seedbed into broadbeds and furrows (BBF) which provides better drainage for cropping. On Vertisols and other soils in the highlands, native pasture and crop residue are the major feed resources. However, quality and quantity of these 491 Agric. Sei. Fint. 1 (1992) https://www.c-info.fi/en/info/?token=BtV-6kx4YcH851TL.4680KJWWyOsaMY-JWvBt5g.99CCdJDCBbp-yOHucXYM85lqqKMEVPr628gunN9RLSSh_ck073Bjub023UBapcTF1_t0YF7a1JBsiIpCimurdiP2RmljJFQGCaaAJYGk1XrHS_djp2y7cUYxKwuhIK8Ap_beZXqidyZ0dV0awh7GBW5jfS3xblYPyvjtE_-er8ZBod_okNQARVrQ0It5Sb2acV9J6VYD2L7gGCL_xG8cdrflxE5dWhbhquxM0ngGh45UzLK6QWJNem3SH0hHzRiiY-QSfXvhsJGUg_T6jdZk4LyN8hOJieYKiH6MOHsOEpGMCmfTZnmlNuKQ2qOg feedstuffs are insufficient to meet livestock require- ments (Lulseged and Alemu 1984). Delayed har- vest ofnative pasture for hay is also responsible for its low nutritive quality (Jutzi et al. 1987). In order to alleviate these problems, ILCA’s Highland Programme has focused its research on the evaluation of forage crops, especially legumes, for the highlands. In earlier studies, Avena saliva, Vigna unguiculata, Lahlah purpureas, Vida dasy- carpa, Trifolium steudneri and Sesbania sesban have shown potential for the medium altitude (1500-2400 m asl) highlands of Ethiopia (Lulseged and Alemu 1984; Jutzi et al. 1987). These forage crops can provide high quality feed either as cut and carry during the rainy season or as hay for dry season feed when seasonal feed short- ages become a serious impediment to meeting live- stock requirements. These forage crops are high yielding (Abate 1984) compared with native pas- tures that have annual yields ofonly 3-4 t/ha (Jutzi et al. 1987) of dry matter, are poor in quality and result in low livestock performance in the dry sea- son. The role of forage legumes in increasing animal performance is well documented (Shaw 1961, 1978; Tothill 1974). However, the yield and quality of these forage crops are influenced by har- vest time and drainage. In this study, field experi- ments were designed to examine the yield and quality trends of potential forage crops under the traditional and improved seedbed methods on Ver- tisol at different harvest times during the growing season. Material and methods Field experiments were conducted in the Ethiopian highlands, at ILCA’s Debre Zeit Research Station (1800 m asl) from 1989 through 1990. The soil of the experimental site is Vertisol, which would nor- mally present drainage problems in the high rainfall season. Rainfall occurs from mid June to mid Sep- tember (main rainy season) and from Feb-ruary to April (small rainy season). Average annual rainfall is about 800 mm, with 70% usually falling in the main rainy season. In the first year of the study, a randomised com- plete block design experiment with four replicates in a factorial arrangement oftwo seedbed methods using three forage legumes giving a total of 6 treat- ments each in a 3.6 x 20 m plot was established. The flat seedbed represented the traditional sys- tem. The broadbed and furrow (BBF) was the im- proved drainage system intended to allow early planting on Vertisols and the removal of excess water from the seedbed. In the second year, the experiment was sown as a split plot design. The two seedbed methods were used as main plots (each 18 m x 20 m) and he forage crops (one fodder oat and four legumes) were used as sub plots (each 3.6 m x 20 m plot) with six replicates ofeach. The forage crops studied and their seed rates are shown in Table 1. At sow- ing, 100 kg/ha di-ammonium phosphate fertiliser was applied uniformly to all treatments in both years. Sampling was done using a quadrant frame of 1 m 2 in each sub plot which was repeated five times to provide yield estimation per net plot of 5 m 2 for each forage crop. Harvests were done randomly at 6, 12 and 18 weeks after plant emergence in the first year. Harvesting was carried out at 6,9, 12, 15 and 18 weeks after plant emergence in the second year in order to determine dry matter yield and Table 1. Forage crops and their seed rate used for the study on Vertisols in the 1989 and 1990 cropping season. Study Forage Species Seed rate year kg/ha 1989 Sesbania sesban 20 Lablab purpureus 50 Vigna unguiculata 75 1990 Avena saliva 100 Lablab purpureus 50 Vigna unguiculata 75 Vida dasycarpa 25 Trifolium steudneri 13 492 Agric. Sei. Finl. 1 (1992) nutritive value over the growing season. The dry matter data were subjected to analysis of variance (SAS); LSD and SED were used for mean compari- sons. Results Dry matter yield Dry matter yields of the three forage crops in the 1989 crop season at differentharvest times over the growing season are shown in Table 2. There was no significant difference in dry matter yield between the flat and BBF seedbed methods at 6 weeks after emergence. However, at 12 and 18 weeks after emergence, there were significant dif- ferences in dry matter yield (P<0.05) between the forages grown on the two seedbed methods. Among the forage crops, dry matter yield dif- ferences were statistically significant at 6 weeks (P<0.001), 12 weeks (P<0.05) and 18 weeks (P<0.01) after plant emergence. When harvested at 18 weeks, Lablab purpureas had the highest dry matter yield, followed by Vigna unguiculata. However, the performance of Vigna mguiculata at earlier harvests was the highest of the two forage crops. The seedbed method by forage crop interaction on dry matter yield was significant at harvests of 6 weeks (P<0.05) and 12 weeks (P<0.05) after emer- gence. The interaction effect at 18 weeks after emergence was not significant. Dry matter yields of the five forage crops in the 1990 cropping season at different harvest times over the growing season are given in Table 3. With the exception of the 18 week harvest time, there were no significant dry matter yield differences between the flat and BBF seedbed methods. There were highly significant differences (P<0.001) in dry matter yield among the forage crops at all harvest times. The interaction ofseedbed methodby forage crop was only significant (P<0.05) at 6 weeks after emergence. From the forage crops evaluated, Avena saliva had the highest dry matter yield (7983 kg/ha) fol- lowedby Lablab purpureas (6292 kg/ha). The low- est yield was recorded for Vicia dasycarpa at 18 weeks after emergence. Table 2. The mean dry matteryields (kg/ha) of three forage cropsunder the traditional seedbed method (FLAT) and on drained (BBF) Vertisol and harvested at different times during the growing season at Debre Zeit, 1989. Seedbeds Forage crop Time ofharves (week after plant emergence) FLAT Sesbania sesban 250 1980 2500 Lahlah purpureus 650 4450 6410 Vigna unguiculata 830 4780 6010 BBF Sesbania sesban 540 2490 3650 Lablab purpureus 470 3360 7140 Vigna unguiculata 1040 4000 5930 LSD (5%) 150 1230 1320 F-test probability Seedbed method (SM) NS P<0.05 P<0.05 Forage crops (FC) PO.OOI P<0.05 P24oo m asl) where clay content greater than 60% is recorded for Vertisols, rainfall exceeds 1000mm per annum and temperatures are lower. These effects result in poor drainage on plant growth throughout the growing season (Juxzi 1983). Of the forage crops tested, Avena saliva, Lablab purpureas and Vigna unguiculata produced high dry matteryields (>6 t/ha) in both seasons. The legumes are ofparticular importance for then- high forage quality (Table 4 and 5). Protein content was high at the earliest harvests but declined grad- ually as the legume matured. This result was ex- pected because older plants are more heavily ligni- fied and normally produce poor quality forage. Conclusion The performance of these forage legumes in terms of yield and quality suggests they are crops of choice for integration into mixed crop - livestock systems in the highlands. However, further studies are needed on how these forages are combined with food crops in land short systems in order to be used for livestock feed. It is expected that if these forage legumes are successfully introduced into the highland cereal cropping system, they could have a significant im- pact on livestock production. Acknowledgements. The authors wish to express their ap- preciation to the Government of Switzerland (SDC) and Finnish International Development Agency (FINNIDA) for the support ofVertisol work reported here at ILCA. The extensive assistance also provided by the Vertisol staff involved in this work especially W/o Nigist Wagaye and W/t Etalem Engeda are acknowledged. References Abate, T. 1984. Results of 1983/84 Forage Network Trials. ILCAHighlands Programme, Addis Abeba, Ethiopia. 15 P- Berhanu. D. 1985. The Vertisols ofEthiopia; their propeties, classification and management. Fifth meeting of the Eastern African Sub-Committee for Soil Correlation and Land Evaluation. Wad Medani, Sudan. World Soil Re- sources Reports No. 56. FAO, Rome. p. 31-54. Gryseels, G. 1988. Role of livestock on mixed smallholder farms in Ethiopian highlands. A case study from the Baso and Worena woreda near Debre Berhan. Dissertation, Agric. Univ., Wageningen, The Netherlands. 249 p. Jutzi, C.S., Haque, I. & Abate, T. 1987. The production of Animal feed in the Ethiopian highlands. Potentials and Limitations. In: lAR Proc. national livestock conference, Inst. Agric. Res., Addis Abeba (Ethiopia). 1. National Livestock Improvement Conference, Addis Abeba Ethiopia p. 141-142 1983. Forage legumes. Networkshop on draft power and animal feeding, CIMMIT, Mexico city Mexico. Eastern and Southern Africa Economics Programme. CIMMIT Networkshop on Draft Power and Livestock Feeding in Eastern and Southern Africa, Mbabane Swaziland 8 p. Jutzi, S.C. 1986. Deep black soils (Vertisols) management options for Ethiopian highlands. African Mountains Workshop, Geo-ecology International Geographical Union, Addis Abeba, Ethiopia. Kamara, C.S. & Haque, I. 1987. Characteristics ofVertisols at ILCA research and outreach sites in Ethiopia, ILCA PSD Workingpaper No. 85. Lulseged, G. & Alemu, T. 1984. Pasture Research Develop- ment in Ethiopia. Pasture Improvement Research in East- ern and Southern Africa. In: Proc. Workshop held in Harare, Zimbabwe. Shaw, N.H. 1961. Increased beef production from Towns- ville lucerne (Stylosanthes sundaicad Tauh) in the spare grass pasture ofCentral Queensland. Australia J. Agric. Animal Husb. 1: 73-80. 1978. Superphosphate and stocking rate effect on native pasture oversown with Stylosanthes humilis in 496 Agric. Sei. Finl. 1 (1992) Central Coastal Queensland. 2. Animal Production. Manuscript received March 1992 Australian J. Exp. Agric. Animal Husb. 18: 800-807. Tothill, J.C. 1974. Experiences in Sod-seedling Siratro into Tedla Abate native spear grass pasture on granite soils near Mundub- bera. Tropical Grassland. 8; 128-132. Helena Airaksinen M. A. Mohamed-Saleem International Livestock Centre for Africa (ILCA) P.O. Box 5689 Addis Abeba, Ethiopia SELOSTUS Kylvöalustan muokkaustapojen ja sadonkorjuuaikojen vaikutusten vertailu kasvien satotasoon ja ravintoarvoon Vertisol-savimailla Debre Zeitissa, Etiopiassa Abate Tedla, Helena Airaksinen ja M. A. Mohamed-Saleem International Livestock Centre for Africa (ILCA) Tutkimuksessa verrattiin parannetun pellon muokkauksen (kuivatuksen, leveää kohotettua kyntöviilua käyttämällä (BBF)) ja perinteisen tasaisen muokkauksen vaikutuksia Avena sotivan, Vigna unguinatan, Lablab purpureumin, Vicia dasyearpan, Trifolium steudnerin ja Sesbania ses- banin kuiva-aine satotasoihin jaravintoarvoihin vertisol-sa- vimailla Debre Zeitissa, Etiopiassa, Tutkimus suoritettiin vuosina 1989 ja 1990. Ensimmäisenä vuonna käytettiin sat- unnaistettujen lohkojen muotoista faktorikoketta (2x3 tasoa). Toisena vuonna käytettiin osaruutukoetta, jossa pääruututa- solla olivat muokkausmenetelmät ja osaruututasolla olivat kasvit. Tarkoituksena oli testata parannetun muokkauksen (BBF) vaikutusta perinteiseen muokkaukseen verrattuna. BBF- muokkausmenetelmä mahdollistaa aikaisemman kylvön, koska liika vesi valuu pois kylvöalustalta, mikämahdollisesti lisää satotasoa. Koelohkoilla, joilla oli käytetty BBF muok- kausta, Avena sotiva ja Lablab purpureum tuottivat 7 m kuiva-aine hehtaarisatoja. Myöhäisempi kasvuaste ja kor- juuaika lisäsivät myös kuiva-ainesatoja. Kasvien raakaval- kuaispitoisuus ja kuiva-aineen in vitro sulavuus aleinivat kasvuasteen edetessä eikä muokkaustavoilla ollut vaikutusta saatuihin arvoihin. Selostettu tutkimus tehtiin Afrikankansainvälisessä kotie- läintutkimuskeskuksessa ILCA:ssa, Etiopiassa. Tutkimusta rahoittivat Sveitsin hallitus jaSuomen Ulkoasiainministeriön Kehitysyhteistyöosasto. 497 Agric. Sei. Finl. 1 (1992)