African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 4, Num. 2, 1996, pp. 257-262

ABATE TEDLA, N.Z. LUPWAYI and HAILU REGASSA^1

International Livestock Research Institute (ILRI), P.O. Box 5689, Addis Ababa, Ethiopia
^1 Institute of Agricultural Research (IAR), P.O. Box 2003, Addis Ababa, Ethiopia

(Received 23 March, 1995; accepted 30 September, 1995)

Code Number: CS96064
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An on-farm trial was conducted over two seasons on Vertisols in the Ethiopian highlands to evaluate a sequential forage/food crop system as an alternative to the traditional fallow/food crop system. The efficiency of residual nitrogen from sequential cropping and fallow systems as a supplement to applied nitrogen in a wheat crop was also tested. Chickpea grown on residual moisture preceded by either oats/vetch mixture or a fallow had similar yields. In the second year, both wheat grain and straw yields were significantly increased at the 60 kg nitrogen level treatment while the straw yield was also significantly increased at the 30 kg nitrogen level compared to 0 nitrogen level.

Key Words: Chickpea, Ethiopian highlands, oats, on-farm, sequential cropping, vertisols, vetch

RESUME

Un essai en milieu paysan a ete realise durant deux saisons sur des vertisols de hautes terres d'Ethiopie pour evaluer un systeme sequentiel de fourrage/cultures vivrieres comme alternative au systeme traditionel de jachere\cultures vivrieres. L' efficacite de l'azote residuel resultant de la culture sequentielle et de systeme de jachere comme supplement d'azote dans une culture de ble etait aussi analysee. Le pois chiche cultive en humidite residuelle apres une culture mixte d'avoine/vesce ou jachere donnait le meme rendement. Dans la deuxieme annee, les rendements de grains de ble et de paille augmentaient significativement apres un traitement de 60 kg d' azote tandis que le rendement de paille augmentait apres un traitement de 30 kg d'azote en comparaison de 0 kg.

Mots Cles: Pois chiche, les hautes terres d'Ethiopie, avoine, sur ferme, cultures sequentielles, vertisols, vesce

INTRODUCTION

Integrated crop-livestock production systems are common land-use types in the Ethiopian highlands (Gryseels and Asamenew, 1985; Asamenew et al., 1993). The integration of crop and livestock production systems is particularly advanced in areas where growing demand for available land has led to a decrease in grazing lands and shorter fallow periods. As land use intensification becomes necessary, food as well as fodder must be produced from the same land unit. Crop residues become important as the main fodder from cultivated areas.

Vertisols are among the most important soils in Ethiopia, accounting for 12.7 million hectares (Debele, 1985). Of the total Vertisol land area, 7.6 million hectares are located in the highlands (1500 m asl). At present, only 25% of the highland Vertisols are estimated to be cultivated. Approximately 70% of the country's population live in the highlands and face the threat of an inadequate supply of food commodities.

Most of the potentially highly productive bottom land Vertisols are only partially utilised during the potential growing period because of waterlogging (Jutzi et al., 1987). Sowing of the major crops, teff (Eragrostis tef), chickpea (Cicer arietinum), grasspea (Lathyrus sativa) and lentil (Lens culinaris) is delayed until the water naturally recedes to escape the negative effect of waterlogging (Tedla and Mohamed-Saleem, 1992). The average yield of these crops is below 1 t ha^-1 (Debele , 1985). In addition to poor yields, growing late-season crops on Vertisols leads to inefficient use of the available moisture. It also makes the land prone to erosion early in the growing season when it is bare.

Over the past eight years, research has focused on solving the problem of excess water by improving moisture evacuation from the fields. A solution was found in shaping the land into broadbeds and furrows using a broad-bed maker (BBM).

The BBM is based on the traditional Ethiopian farm implement "maresha". Pulled through the soil by a pair of animals, the BBM makes two parallel cuts while its wings scoop the soil towards the middle and mound it. The result is a series of broad, raised beds 15 cm high, 80 cm wide, separated by 40 cm wide furrows into which the excess water drains (Jutzi et al., 1986; Astatke, A. and Kelemu, F., Unpubl. data).

With the broadbed and furrow land management system, crops can be sown at the beginning of the main rains without the adverse effects of waterlogging, thus making early planting feasible. Improved drainage on Vertisols has two major beneficial effects. First, it enables farmers to grow longer-duration crop varieties. Second, it allows them to use various cropping options and crop varieties giving higher yields of grain and straw (Willey , 1981; Tedla et al., 1992; 1994).

This paper reports on testing, on-farm, a sequential f orage-food crop system on a drained Vertisol as an alternative to the traditional single cropping system, and its effects on a subsequent wheat crop in the second year.

MATERIALS AND METHODS

Experimental site. The trial on sequential cropping and its residual effects in the succeeding year were conducted at Ginchi (9degrees 0'N, 38degrees 15'E), 2200 metres above sea level in 1992 and 1993. The soil in all the fields is classified as a pellic Vertisol and the physical and chemical characteristics of the soil profile from the same topographic area are given in Table 1.

Selection of farmers. With the help of the Ministry of Agriculture agent at Ginchi, eight representative farmers were identified on one part of the extended Vertisol in the central Ethiopian highlands, and the distance between their farms was 0.5 - 2 km. All the farmers selected for the on-farm sequential cropping trials accepted to participate and implement the work in their own fields. All field operations were carried out by farmers, according to their practice and preference, but were supervised closely by the researchers involved in the trial.

Treatments. The sequential forage-food crop trials were carried out in June 1992 and January 1993 using the broadbed and furrow system. The first treatment comprised oats (Avena sativa) intercropped with vetch (Vicia dasycarpa). Planting was in mid-June to coincide with the beginning of the main rainy season. The oats/vetch forage (first crop) was harvested at the end of August by the cut and carry method to determine dry matter yield. The harvested plots were then sown to chickpea (food crop) which grew between September and January to make use of the residual moisture. The traditional rainy-season fallow (June-August) and the September to January chickpea crop served as a second treatment. The chickpea (second crop) plots in both treatments were harvested in January to measure grain and straw yields.

Table 1

In the 1993 crop season, the residual effects of sequential cropping and fertilizer N were assessed on the same eight farmers' fields. The two 1992 treatments (rainy season oats/vetch followed by chickpea, and rainy-season fallow followed by chickpea) were each split for three rates of N: 0, 30 and 60 kg N ha^-1. The N source was urea and no other fertilizer was applied. All the plots were planted in mid-June to bread wheat (Triticum aestivium) cv ET 13 at a seed rate of 150 kg ha^-1, on the broadbed and furrow system. The seed and fertilizer for the trial were received from the Institute of Agricultural Research in Addis Ababa. At crop maturity, six random samples of wheat per plot were harvested at ground level, and grain and straw yields were determined.

For comparison of results from all treatments, analysis of variance was carried out using a SAS statistical package (SAS, 1989).

RESULTS AND DISCUSSION

First crop : oats/vetch mixture. The dry matter (DM) yields of the oats/vetch mixture of the eight farms ranged from 3 to 11 t ha^-1, with a mean of 6 t ha^-1. The difference in the performance of oats/vetch among the farms could be attributed to the variation in the natural fertility of the soil, since the soil characteristics represent a mean of a wide area. There were no fertility studies in the individual participating farmers' fields.

Second crop: chickpea. The grain and straw yields of chickpea grown after the first crop of oats/vetch and the early-season fallow are presented in Table 2. There were no significant differences in grain and straw yields between chickpea grown after oats/vetch and that grown after early season fallow. Similar results have been obtained from previous on-station work (Tedla et al., 1994) which demonstrated that a sequential system of oats/vetch in the early season followed by chickpea could be achieved with no reduction in the second crops. The sequential system simply adds a feed crop to the traditional cropping system on Vertisols.

Table 2

We conclude that cropping oats/vetch mixture (feed) in the early season that is supplied with N and P fertilizers is a likely means of increasing land productivity since this is not at the expense of the food crop (chickpea). Such a system could be attractive to farmers in the Ethiopian highlands where land is a constraint and natural forage is in short supply with the growing livestock population.

Residual effects. Residual effects of sequential cropping on succeeding wheat grain and straw yields are shown in Table 3. There were no significant (P<.05) differences in grain and straw yields of wheat succeeding oats/vetch-chickpea and fallow-chickpea cropping systems. Also, there were no significant interaction effects between the two cropping systems and nitrogen application levels. Wheat grain yield significantly increased at the 60 kg ha^-1 nitrogen fertilizer treatment while that of straw was significantly higher at the 30 and 60 kg nitrogen ha^-1 levels. These results mean that there were negligible residual effects of either of the two cropping systems in the previous year.

ACKNOWLEDGEMENTS

The authors would like to acknowledge the financial support for the work provided by the Government of Switzerland (SDC). Thanks are also extended to Ato Degefa Beru, W/o Nigist Wagaye, W/t Sara Petros and Ato Kinde Engida for their assistance in the execution of the on-farm trial and preparation of the manuscript. The authors are also greatful to Dr. A. M . Mih and Mrs. Inca Alipui for their time and interest taken in reviewing the paper.

REFERENCES

Asamenew, A., Zerbini, E. and Tedla, A. 1993. Crop-livestock interactions and implications for animal traction research in the Ethiopian highlands. In: Proceedings of the Fourth National Livestock Improvement Conference held 13-15 November 1991, Addis Ababa, Ethiopia. IAR, NLIC Proceedings No. 4, pp.29-36.

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

Gryseels, G. and Asamenew, G. 1985. Link between livestock and crop production in the Ethiopian highlands. ILCA Newsletter 4 (2): 5-6.

Jutzi, S.C., Asamenew, A., Haque, I., Tedla, A. and Astatke, A. 1987. Intermediate technology for increased food and feed production from deep black clay soils in the Ethiopian highlands. In: Improving Food Crop Production on Small Farms in Africa. FAO, Rome. pp.373-383.

Jutzi, S. C., Anderson, F.M. and Astatke, A. 1986. Low-cost modification of the traditional Ethiopian tine plough for land shaping and surface drainage of heavy clay soils: Preliminary results from on-farm verification trials. ILCA Bulletin 27:28-31.

Kamara, C.S., Haque, I. and Desta Beyene. 1989. Characterstics of soils at IAR research sub centres at Sheno and Ginchi. Plant Science Division Working Document B9. ILCA and IAR, Addis Ababa, Ethiopia. 55pp.

SAS Institute, 1989. SAS STAT User's Guide, Version 6, 4th Ed., vol. 2. SAS Institute, Cary, NC. 846pp.

Tedla, A. and Mohammed-Saleem, M. A. 1992. Cropping systems for Vertisols of the Ethiopian highlands. In: Reports and Papers on the Management of Vertisols (IBSRAM/AFRICALAND). Network Document No.1. IBSRAM (International Board for Soil Research and Management), Nairobi, Kenya. pp. 55-56.

Tedla, A., Mamo, T. and Gebeyehu, G. 1992. Integration of forage legumes into cereal cropping systems in Vertisols of the Ethiopian highlands. Tropical Agriculture 69:68-72.

Tedla, A., Sherington, J. and Mohammed-Saleem, M. A. 1994. Integration of forage and food crops sequentially on Vertisols under rainfed conditions in the mid-altitude Ethiopian highlands. Experimental Agriculture 30: 291-298.

Willey, R. W. 1981. A scientific approach to intercropping research. In: Proceedings of the International Workshop on Intercropping, Jan 10-13, 1979. ICRISAT, Hyderabad, India.

Copyright 1996 The African Crop Science Society

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