Varietal Trials and Physiological Basis for Yield Differences among Cowpea Varieties in Sudan Savanna of Nigeria

Field trials were conducted at Damboa (11o10.736’N; 12 o47.100’E; elevation 398 m asl) on the trial site of the International Institute of Tropical Agriculture (IITA) in Borno State in Sudan savanna zone of Nigeria during the 2010 and 2011 rainy seasons. The objectives of the study were to evaluate the agronomic performances of some improved cowpea varieties and to identify the physiological traits associated with high grain yield in the Sudan Savanna zone of Nigeria. The trial consisted of eight treatments, which included two local varieties viz: Kannanado White and Borno Brown obtained from farmers in Damboa, Borno State and six improved varieties viz: IT90K-277-2, IT97K-568-18, IT89KD-288, IT97K-499-35, IT98K-131-2 and IT89KD-391 obtained from IITA stations in Kano and Maiduguri, Nigeria. The treatments were laid out in a randomized complete block design (RCBD) replicated three times. The gross plot size was 5.0 m x 4.0 m (20 m2) while the net plot size was 3.6 m x 3.0 m (10.8 m2). The results showed that the improved varieties IT90K-277-2, IT97K-499-35 and IT98K-131-2 had significantly higher grain yield per hectare, harvest index and matured earlier to escape drought in this agro-ecological zone. The results also show that cowpea grain yield was positively correlated with harvest index, shell weight and grain yield per plant. Conversely, the results indicated that cowpea grain yield was significantly negatively correlated with number of days to first and 50% flowering, fodder yield, 100-grain weight, number of days to physiological maturity and pod development period.