PRODUTIVIDADE DE FEIJOEIRO-CAUPI CULTIVADO COM ESTIRPES RIZOBIANAS E DOSES DE FÓSFORO.

Biological nitrogen fixation has been shown to be indispensable for the sustainability of Brazilian agriculture, due to the supply of nitrogen with low economic cost to crops and reduction in environmental impact. Given the above, the objective of this study was to evaluate the efficiency of rhizobian strains and phosphorus doses, to maximize the growth of two cowpea cultivars and nitrogen fixation and to obtain better agronomic performance. The experimental design was a randomized complete block in a 3 x 6 factorial scheme (2 rhizobium strains + 1 treatment without inoculation x 6 phosphorus doses), containing 4 replications. The doses consisted of 0, 30, 60, 90, 120 and 150 kg ha-1 of P2O5. Potassium fertilization was performed at sowing using 60 kg ha-1 of K2O. Water supply for the crop was performed with irrigation and two-day watering shift, with approximate flow rate of 5 mm. The characteristics evaluated were: chlorophyll performed 45 days after sowing, shoot dry biomass (g), one hundred seed weight (g), total shoot nitrogen (dag kg ha-1) and yield (kg ha-1). In general the two strains tested showed capacity for nodulation and biological nitrogen fixation. The strain INPA 03-11B was the most suitable for cv. BRS Sempre Verde and BR 3299 the most suitable for cv. BRS Vinagre cowpea. The phosphorus dose that conditioned the maximum agronomic efficiency in cowpea ranged from 70 to 110 kg ha-1. Higher nitrogen content for both bean cultivars was verified with the strain BR 3299. [ABSTRACT FROM AUTHOR]