Growth, yield and plant-water relations of four cowpea (Vigna unguiculata) cultivars in the Sahel

Abstract

The response of four cowpea (Vigna unguiculata (L.) Walp.) cultivars to the warm, semi-arid tropical environment at the ICRISAT Sahelian Center at Sadore, Niger was studied during 1985 and 1986 in terms of leaf area index (LAI), dry matter (DM) accumulation, net photosynthesis, stomatal conductance, total water use and yield. Among the three improved cultivars, IT82D-716 is early and erect, cv. IT83S-947 is early and spreading and cv. TVX4659-03E is a medium-duration, highyielding, dual-purpose type. The local cv. Sadore Local is a long-duration, photosensitive, spreading type used mainly for fodder. In both years, Sadore Local recorded the highest LAI. IT82D-716 and IT83S-947 produced < 1-3 t/ha of DM in both years, whereas TVX 4659-03E produced > 2 t/ha of DM and proved superior to Sadore Local in partitioning DM into pods. The four cultivars did not differ significantly either in stomatal conductance or in net phytosynthetic rates. Observed maximum photosynthetic rates of c. 20 umol/m 2 /s lie at the bottom of the range 21-38 umol/m 2 /s reported for 31 cowpea genotypes in an earlier study. Photosynthetic rates increased with increasing photon flux density. TVX4659-03E had an advantage in total seed plus fodder yields while the local cultivar gave significantly greater fodder yields in both years. Seed and fodder yields, as well as water-use efficiency, confirmed the advantages offered by the dual-purpose cultivar TVX4659-03E. Future breeding efforts in the Sahel should focus on dual-purpose (grain/fodder) cowpea types.

Simulation of growth and development of irrigated cowpea in Piauí State by CROPGRO model

“…Thus, in 1998 the flowering time (about 43 days) of cowpea occurred during a period of high air temperatures (around 35 o C) (Figure 1), that contributed to reduce both observed and simulated grain yields by 12 and 19%, respectively. This was also noted by other authors (Roberts et al, 1978;Summerfield et al, 1978;Doto & Whittington, 1981;Shouse et al, 1981;Sivakumar et al, 1996;Craufurd et al, 1998).…”

“…This is a common characteristic in cowpea, as observed by Littleton et al (1979), Castro et al (1984), Phogat et al (1984) and Sivakumar et al (1996). Soon after, an accelerated vegetative growth was observed, with maximum values of LAI, observed and simulated, varying from 3 to 4.3, in 1997 and 1998, respectively.…”

Grain yield and contribution of symbiotically fixed nitrogen to seed in cowpea varieties using the15N natural abundance technique

“…Cowpea (Vigna unguiculata) is a grain legume, widely grown by many resource poor farmers in Africa and other developing countries of the world (Sivakumar et at., 1996;Vandermeer, 1992). In the Northern Province of South Africa, matured dry cowpea seeds constitute a major source of dietary protein among rural dwellers.…”

“…, Farmers in the province are accustomed to planting seetls saved from their previous harvest. Identification of well adapted varieties with high nitrogen fixing abilities has the potential to improve cowpea productivity in the province and their contribution to soil fertility in the overall cropping system (Sivakumar et al, 1996;Singh & Ntare, 1985). The main objectives of this research were to identifY cowpea varieties with superior grain and protein yield abilities and also to assess the proportion of seed N that was derived from symbiotic fixation.…”