DOSES DE NITROGÊNIO E FÓSFORO PARA A PRODUÇÃO ECONÔMICA DA MAMONEIRA NO MUNICÍPIO DE MOSSORÓ-RN

Abstract

The fertilization of the castor bean plant (Ricinus communis L.) is few studies in the Northeast, where soils are generally poor in nitrogen (N) and phosphorus (P). This work aimed to define the doses of N and P2O5 associated with maximum economic production of castor beans cultivar BRS Energia and critical levels of N and P in castor bean leaf and the critical level of P available in an Oxisols. The experimental design was a randomized block in factorial 4 x 4 with four replicates, combining four N rates (0, 45, 70 and 120 kg ha-1) with four P2O5 rates (0, 30, 60 and 120 kg ha-1). The castor bean plant was planted at a spacing of 0,90 x 0,50 m under rainfed conditions with supplementary irrigation. At the end of the experiment, was evaluated the overall productivity and productivity racemes primary, secondary and other. The higher net income was estimated to productivity of 2.304 kg ha-1 grain, obtained by applying the doses of 120 kg ha-1 of N + 120 kg ha-1 of P2O5. The critical levels of N and P in the leaf were 37,5 g kg-1 and 2,4 g kg-1, respectively, and the critical level of available P in soil by Mehlich-1 extractor was 7,0 mg dm-3.