Effects of seedbed preparation methods on cowpea yield in Alfisols and Oxisols in semiarid West Africa

Tied-ridge techniques have not been used to improve seed yield in cowpeas, so experiments were conducted in Burkina Faso in the Sudan savannah zone on an Alfisol at five slope-positions on the toposequence, using two dates of planting for three consecutive years; and in the northern Guinea savannah zone, at a mid-slope position on an Oxisol with one date of planting for two consecutive years. In these trials, the effect of planting cowpeas on tied-ridge seedbeds was compared with planting on the flat. The plots were tractor-ploughed to 25 cm depth prior to the establishment of seedbed preparation methods. Tied-ridge seedbeds eliminated or reduced runoff, increased soil water storage and reduced severe seed yield losses during protracted dry spells in the Sudan savannah zone on an Alfisol, but they had no effect at all on cowpea yield in the northern Guinea savannah zone on an Oxisol. In the Alfisol, tractor ploughing and early planting were not adequate to reduce runoff and the cowpeas were subjected to severe yield loss during dry periods

Use of successional sowing in evaluating cowpea (Vigna unguiculata) adaptation to drought in the Sudan savannah zone. 2. Responseof reproductive traits

Two sets of experiments on cowpea sowing date were conducted in 1983–85 at Ouagadougou, Burkina Faso. One set tested six daylength-insensitive (DI) cultivars and the other compared four or five daylength-sensitive (DS) cultivars with one or two DI cultivars as controls. Sowing after inadequate rainfall, particularly when followed by drought stress, impeded seedling establishment and growth. Severe drought stress during the reproductive growth stages and prolonged drought stress throughout the crop season adversely affected flowering, flowering and subsequent yield. Cultivar differences in ability to withstand drought damage were observed. The ability of cultivars to (i) branch profusely, to compensate for stands lost by drought during seedling growth and (ii) flower at such a time that pod set and fill coincide with favourable climatic conditions appears to be a prerequisite for satisfactory adaptation to the Sudan savannah zone of semi-arid West Africa. Daylength-sensitivity and early maturity per se were inadequate to prevent yield losses under drought conditions