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    the equipment, its design quality, sustained production and marketing,

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    farm level crop yields as affected by the introduction and use of Contil equipment or practice,

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    participatory approaches where not just technological but also socio-cultural and economic constraints to adoption have been addressed.

It may be argued that the most successful programmes have been those of Zambia and Zimbabwe. From these, complete animal drawn equipment packages covering the range of primary as well as secondary tillage operations have come to existence. In no-till and minimum tillage systems energy saving direct seeding equipment have been manufactured. Due to high weed infestation in these systems animal drawn cultivators have also been developed.

Examples of equipment developed are such as the Mogoye ripper and its wing attachments which easily make it a Contil ridger and weeder; or its planter attachment which makes it a direct seeder. The animal drawn subsoiler, one version from Zambia and another from Zimbabwe are but a few examples of the range of equipment developed in the region. Others are such as the tie-ridger, a most useful light equipment which helps conserve moisture in the driest areas. Some efforts have attempted to modify the traditional Ethiopian Maresha among other efforts.

2.5.1

Farmer management, soil and micro- topography

Micro-topography (small differences in surface elevation, 0.2 –0.8m, over distances of 20-50m, not associated with the overall slope) was identified as a major scale of within field variability. The high areas were commonly associated with termite activity and the soils were generally more fertile with higher pH and clay content than low areas. However the high areas (despite greater available water holding capacities) were always drier than low areas where runoff landed.

Several tillage options were tried including tie ridging and strip tillage. Cultivation was shown to improve the infiltration into the soil. Despite the complications introduced by micro- topography, double cultivation appeared to improve crop establishment. This was attributed to better soil moisture conditions early in the season through improved infiltration and weed control.

For tie-ridging, the system did have effect of preventing redistribution of water within fields, while concentrating water in the furrow bottom. The seed was sown in the base of the ridge and was close to the subsoil as most of the top soil had been used to form the ridge. This positioning of the seed avoided the potential water logging effects of the furrow bottom and the dry conditions in the ridge top. The early development of the plants was always slower than in the flat row planted control, due to soil compaction in the root zone. Planting in the ridge top was not a feasible option as this was the driest soil. Although such a system could not be recommended a modified wide-bed, tied ridge and furrow system appeared more promising.

Working in Botswana Harris et al (1992) analyzed farmers practices with regard to management and soils, micro-topography and tillage options. Farmers commonly grew a variety of crops with mixed stands of sorghum, maize, water melon, cowpeas and sweet sorghum. Most farmers broadcast their crops and this resulted in areas of high and low crop density. Row planting provided better control of plant population densities reducing the inter- plant competition and facilitating weeding.

Extensive research was conducted into strip tillage systems, where alternate bands of soil were cropped and kept bare, both under well controlled experimental conditions and in farmers fields. Water flowing through a series of such crop strips was likely to result in a cascade effect with consequent soil erosion problems.

2.5.2 Water harvesting and agronomic practice

The work in farmer’s fields highlighted the importance of accessibility to draught animal power for timely cultivation and planting. Good crop establishment was clearly a key factor for good productivity. The spatial and temporal variability of the rainfall and the spatial variability of soil properties were confounding factors in comparing the influence of sites and soils on crop production.

Water harvesting from off-field sources was also explored. There was potential for such schemes to benefit other farmers. No specialist equipment was needed for construction of bunds. Each site would however have required specific investigation and design to fit socio-economic aspects.

Various agronomic and management factors were considered. The need for timely sowing

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This paper is published in: Kaumbutho P G and Simalenga T E (eds), 1999. Conservation tillage with animal traction. A resource book of the

Animal Traction Network for Eastern and Southern Africa (ATNESA). Harare. Zimbabwe. 173p. A publication supported by French Cooperation, Namibia. For details of ATNESA and its resource publications, see http://www.atnesa.org

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