Evaluation of symbiotic N nutrition, C accumulation, P uptake and grain yield of fifteen mungbean genotypes planted at two sites in South African region.

M. Tech. AgricultureMungbean (Vigna radiata L. Wilczek) is becoming a food security crop in Africa, especially in South Africa where there is a growing Asian population. To promote its production by farmers, 15 elite mungbean varieties were evaluated for plant growth, symbiotic N (nitrogen) nutrition and grain yield at Nelspruit and Kliplaatdrift in Mpumalanga Province, South Africa. Genotypes VC6486-10-S1 and VC6493-44-1 at Nelspruit, and VC6510-151-1, VC1973A and VC3960-88 at Kliplaatdrift showed better growth and fixed significantly more symbiotic N than the other genotypes. They also seemed to obtain more N from soil. At both Nelspruit and Kliplaatdrift, two genotypes (namely, VC6510-151-1 and VC6493-44-1) exhibited much greater δ¹³C (carbon) values, and hence higher water-use efficiency. A comparison of P (phosphorus) nutrition between Nelspruit (received no P) and Kliplaatdrift (received 20 kg P.ha-1) revealed mineral P suppression of acid phosphatase activity in the rhizosphere of all fifteen mungbean genotypes at the latter site. The findings further showed that there is a direct functional relationship between water-use efficiency and N2 fixation, and between water-use efficiency and P nutrition