Note on phosphorus and cultivar enhancement of biological nitrogen fixation and productivity of maize/bean intercrops in Malawi uri icon

abstract

  • Little attention has been given to soil fertility technologies for maize (Zea mays L.)/bean (Phaseolus vulgaris L.) intercrops common in Africa, and yields and bean biological nitrogen fixation (BNF) remain perpetually low. This study investigated the effect of 30 kg ha(-1) P fertilizer and improved bean cultivars on intercrop yields and bean BNF (measured by the N-difference method) at two sites with nutrient deficient soils typical of high altitude cropping systems in Malawi. Following farmer practice, maize was the dominant crop of the intercrop and bean a low density 'bonus' crop. Phosphorus application to the maize/bean intercrop consistently enhanced maize and bean yields and BNF. Yields of the improved cultivars were about 150% higher than farmer cultivars at both 0 and 30 kg P ha(-1). BNF was increased by about 90% in improved cultivars compared to farmer cultivars, with the exception of one site in 1996/97, A trial conducted at nine sites on-farm was used to evaluate a fertilizer strategy of P (30 kg ha(-1)) and N (30 kg ha(-1)) applied to a maize/bean intercrop versus sole maize. Yields and economic evaluation indicated high mean net benefits for an average cost/price scenario for fertilizer application to maize/bean intercrop: net benefit was US$192 ha(-1), compared to unfertilized sole maize, net benefit US$62 ha(-1). Net benefit for fertilizing sole maize was US$86 ha(-1). Fertilizing maize/bean intercrops is a promising technology for smallholder farmers in upland, P-deficient soils, in areas where beans as a sole crop are not valued sufficiently to be fertilized by subsistence farmers. (C) 1998 Elsevier Science B.V. All rights reserved.

publication date

  • 1998
  • 1998