Abstract

The cowpea represents one of the most important agricultural species of the brazilian Northeast, and proper management of mineral fertilizer that culture becomes essential to their production. The present work aimed to study the effect of the interaction between potassium and phosphorus in the presence of the inoculant INPA 03-11B in the culture of cowpea for Production Pole of Bom Jesus, Piaui, Brazil. The experiment was conducted in the experimental area of the Federal University of Piaui, Campus of Bom Jesus, PI, about a Quartzarenic Neosol. The experimental design was a randomized block with four replications. The treatments consisted of four levels of potassium (0, 35, 70 and 105 kg K₂O ha^-1) and four levels of phosphorus (0, 40, 80 and 120 kg P₂O₅ ha^-1). Nodule number, nodule dry and fresh biomass, shoot dry biomass and grain yields were evaluated. The potassium and phosphorus levels and their interaction affected nodulation and parameters indicators of production of cowpea. The interaction between the phosphorus and potassium levels favored the nodulation, shoot dry biomass and grain yield. The highest grain yield of cowpea was obtained with the fertilization of 67.73 kg of P₂O₅ ha^-1 and 35 kg of K₂O ha^-1.

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