in lower yields than hand weeding or the cultivator system.
importance. Time determines not only what is possible when, but also the energy requirements, operational efficiency and yields.
Mid-season ridging at the time of weeding, which could be used in combination with widely used plough and planting systems, was a versatile method of preparing a water conserving landform. It could also provide timely weed control following tine tillage, that is planting along a rip line (Shumba et al., 1992). Farmers would then have a low draft system of plant establishment without the requirement for additional weeding labour caused by early weed growth in the untilled interrows. This approach to reduced seed-bed preparation may allow conservation tillage to be introduced where other systems such as mulch ripping (for example, Anazodo et al., 1991) are impractical because the crop residues are used for livestock feed. Other potential benefits, as yet unquantified, were the effects of the previous season's tied ridges on the conservation of early spring rainfall, prior to spring tillage.
2.6 Technology advancement
Dry-planting and pre-season hard pan breaking are some of the practices which are of great significance especially in areas of limited rainfall amounts.
Generally, physical technologies involve implements and tools which, in many applications add work and energy efficiency towards applying the biological technologies.
2.6.1 Research Findings versus traditional practice
Most field operations particularly by small- holder farmers are performed manually thereby limiting the area cultivated per person. The fact that most operations are performed by hand limits the extent to which farmers can adopt certain conservation tillage practices as draught power or mechanisation is almost always a requirement.
Conservation tillage and technology needs to be defined in the broad sense. Contil technology is much more than animals and their care, implements and equipment, crop varieties and their management and even soil and water management techniques. In recent days the broader approach to technology and its transfer calling for multi-disciplinary and multi-sector approach has become necessary.
The need for systems approach to conservation tillage and management needs emphasis. Technology includes sustainable soil and crop management options available to farmers in the region. Among the various equipment that have been introduced in ESA, the range of practices include technology for seedbed preparation, planting and erosion control. Biological conservation technologies are such as agroforestry, mulch farming, contour and strip cropping, legume-based crop rotations, cover crops and green manures, mixed farming practices based on controlled grazing, use of farm-yard manure and others.
Conservation tillage technology needs to be seen and defined to include these and what may be called physical technologies such as no-till, minimum-till, vegetative hedges, sod-seeding, contour ridges, tie ridges, mulch farming, terracing, rough-ploughing, deep sowing and pot-holes, among others (see Chart 3). Time when these various technologies, or accompanying operations are applied is of prime
Thus the development of mechanical power has been related to scales of production associated with the colonial history of the respective countries. The adoption of conservation tillage systems is related to the resource ownership of the farmers particularly draught power. In Zimbabwe for instance it is estimated that 5-10% of the commercial farms are under true conservation tillage whilst the use of conservation tillage in the small-holder farming sector is estimated to be below 1% (Nyagumbo, 1998).
Assessing the potential for adoption of advancing technology and specifically on weed control in the region Nygumbo (1998) reported that weeding effort which accounted for more than 60% of the labour used for maize production, was greatly eased by animal drawn cultivators and ploughs used to control weeds. The efficiency of weed control was also found to greatly improve where farmers used re-ridging with the plough as a weed control measure under no-till tied ridging in the sub-humid north of Zimbabwe (Nyagumbo, 1993). The technology utilization remained low. Comparatively in the larger scale commercial farming sectors of Zimbabwe, Zambia and South Africa the spread of Contil technologies could be attributed to the availability of suitable machinery and the herbicides which have tended to be unaffordable to small-holder farmers in Zimbabwe.
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