Thirty varieties of cowpeas (
Vigna unguiculata
L. Walp) were evaluated for their yield stability using two methods of field trials. One set of environments was created by using different crop protection management practices within one location. The second set was created by using different seasons and locations. The results of both methods revealed significant differences among environments, genotypes and genotype x environment interactions. Both methods showed that most of the varieties were stable with regression coefficients (b) not significantly different from unity, mean square deviations from regression (s
2d) close to zero, high coefficients of determination (r
2) and high grain yields. It was concluded that where funds, time, co-operating scientists and competent field assistants are limiting the simulation of environments could be resorted to. Five varieties IT85F-1987, TVx3236, IT82D-716, IT82D-522-1 and TVx274-02 were selected, using the stability parameters of both methods and other desirable traits for further testing before eventual release to farmers.
