The two years on-farm tillage research during the 1999 and 2000 cropping seasons in an Ethiopian highland Vertisol area demonstrated the importance of adapting cultural practices into participatory trials. The minimum tillage package could be an effective intervention for soil conservation due to the early-vegetative cover of the soil. Based on farmers' application of ash on Vertisols at Chefe Donsa, the incorporation of 50 kg ha −1 of potassium sulphate (K 2 SO 4 ) in the on-farm trial significantly increased grain and straw yields of wheat. The nitrogen levels in the grain and straw of wheat on plots given K 2 SO 4 were higher than those without. The nitrogen level for both wheat grain and straw was even higher when grown on plots previously growing legumes that received K 2 SO 4 . This showed that the availability of extra potassium in these soils improved the extraction of nitrogen by the wheat crop, thus improving the grain yield. The findings indicate the need to reassess the traditionally-practised system of not applying potassium fertilizer to Ethiopian soils. I N T RO D U C T I O NVertisols cover 10.3 % of the total landmass of Ethiopia, two-thirds of which are in the highlands at altitudes higher than 1500 m asl (Wakeel and Astatke, 1996). Despite the fact that they have high agricultural potential, these soils are generally regarded as marginal due to their hydro-physical properties leading to waterlogging in the main rainy season ( June to September) and cracking during the dry months. On Vertisols, crops are planted at the tail end of the rainy season, exposing the tilled soil to the heavy rains during most of the rainy period; this often results in high soil erosion.In order to solve the waterlogging problem on Vertisols, a research consortium has developed an animal-drawn cultivator called a broadbed maker (BBM) by modifying the local implement known as 'maresha'. The BBM creates 0.8 m wide beds separated by 0.4 m wide furrows that allow excess water during heavy rains to be discharged to a main drain or other outlet at the bottom end of a plot. This technology allows early planting to take advantage of a longer growing period, resulting in higher yields and less erosion as there is adequate vegetative cover during the rainy season (Astatke and Mohamed Saleem, 1998;Mohamed Saleem, 1995). † Corresponding author: a.astatke@cgiar.org

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10Farmer participatory tillage trials were conducted in a highland Vertisol area of Ethiopia during the 1999 and 2000 cropping seasons. This participatory initiative clearly demonstrated that incorporating farmers' knowledge, ideas and preferences could improve the wheat production package. A traditional practice of Chefe Donsa farmers-applying ash from their homesteads to their fields to enable early-sown crops to withstand frost-led to the verification of the yield-enhancing effect of inorganic potassium fertilizer on wheat. Farmer adoption of a minimum tillage production system increased the gross margin of wheat production by US$ 132 per hectare-based on 1999 prices-relative to the traditional flat seedbed system. The minimum tillage system was characterized by a much lower level of soil manipulation relative to the traditional flat seedbed system, and, as a consequence, markedly reduced the total human labor and draft oxen requirements for wheat production. Thus, the minimum tillage system could be an effective intervention for soil conservation due to early-season vegetative cover of the soil surface. Also, the early crop harvest associated with the minimum tillage system was highly beneficial for small-holder farmers-since the early harvest coincided with the cyclical period of severe household food deficits and high grain prices in local markets. 11 12 13 14 15 16 17 18 19 20 21 22 (A. Astatke).while the last pass can reach approximately 20 cm in 35 depth (Astatke and Kelemu, 1993). Cropland is usually 36 tilled in preparation for the main rainy season, extend-37 ing from June to September. For tef (Eragrostis tef), 38 the principal cereal crop of Ethiopia, seeds are sown 39 during the middle of the main rains. For other crops, 40 e.g. local wheat (Triticum spp.) and pulses, seeds are 41 sown at the beginning of the main rains on light soils 42 and close to the end of the rainy season on heavy clay 43 soils such as Vertisols. 44 About 12.6 million ha of Vertisols, comprising 45 roughly 30% of the Vertisol area in Africa, are lo-46 cated in Ethiopia. Vertisols cover 10.3% of the total 47 surface area of Ethiopia, and two-thirds of the Ver-48 1 tisol area is located in highlands >1500 m a.s.l. (El 49 Wakeel and Astatke, 1996). Despite their high agri-50 cultural potential, Vertisols are generally regarded as 51 problematic soils in Ethiopia due to their character-52 istic hydro-physical properties, which lead to a high 53 incidence of prolonged water-logging during the main 54 rainy season. For this reason, most crops are sown 55 on Vertisols towards the end of the main rainy sea-56 son. Thus, the tilled soil is exposed to intense rainfall 57 during the major portion of the rainy season; due to 58 the lack of adequate vegetative cover, this results in 59 a high rate of soil erosion. Furthermore, crops sown 60 late on Vertisols in order to escape water-logging uti-61 lize residual soil moisture to mature, and inevitably 62 experience water stress during the seed filling stage, 63 lowering grain yield levels....

Land degradation is one of the major problems related to low productivity in Ethiopia. Vertisols are potential agricultural lands but are underutilized due to waterlogging during the rainy season and are prone to soil erosion due to the traditional practices of planting crops at the end of the rainy season exposing bare land to heavy rains. An animal-drawn implement, the broadbed maker (BBM), was tested to facilitate drainage of the Vertisols. Improved drainage enables earlier planting of crops to use the resultant prolonged growing period for attaining higher yields. In order to further improve the BBM package, the frame of the BBM was used for attachment of other implements to minimize tillage practices and reduce seed and fertilizer rates, labour and animal power requirements and soil erosion. The attachments were tested both on-station and on-farm with positive results.

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