Resposta da mamona, cultivar BRS-188 Paraguaçu, à aplicação de nitrogênio, fósforo e potássio.

Abstract

The Castor bean crop (Ricinus communis L.) is raising attention as an alternative crop for oil and biodiesel production. The mineral fertilization is an important factor that influences plant production because satisfies demand of nutrients. However, little information on suitable fertilizer recommendation exists for the castor bean and when existing usually these recommendations are unbalanced. These facts justify the present work, which had as objectives to evaluate the behavior of castor bean crop, cultivar BRS-188 Paraguaçu, to isolated applications of N, P and K, aiming to show, the ineffectiveness of such action and at the same time identify the nutrient levels that provide the best results, aiming to use these levels in future NPK mixed formulations. The experiment was carried out in a greenhouse located at the Campus I of the Federal University of Campina Grande, Paraiba State, Brazil, from June to November 2007. The experimental design was a completely randomized with thirteen treatments and three replicates, with the total of forty-five experimental units, consisting of isolated application of five nitrogen levels (40, 80, 120, 160 and 200 kg ha-1), five phosphorus levels (30, 60, 90, 120 and 150 kg ha-1) and five potassium levels (30, 60, 90, 120 and 150 kg ha-1). After thinning, a castor bean plant, cultivar BRS-188 Paraguaçu, was grown on a 78 kg capacity plastic container experimental unit until 140 days. The soil water content was daily monitored with TDR equipment. Data of plant height stem diameter, number of leaves, leag area, days for the emission of the first inflorescence, first inflorescence height, number of inflorescences, phytomass, root/aerial part ratio, water use and efficiency, were submitted to analyses of variance, test of Tukey and regression analysis to study the effect of the treatments. The results allowed to conclude that castor bean plants, although receiving increasing levels of nutrients, developed and produced well. The isolated application of increasing levels of nitrogen, phosphorus and potassium, was not efficient for the plant to reach its potential productivity. Among the three nutrients evaluated, the isolated application of nitrogen e promoted the best development of the plant; the castor bean fertilization must be conducted in a balanced manner in future studies, recommending to test applications of N, P and K together on formulation of 200 kg ha-1 de N, 120 kg ha-1 de P2O5 and 150 kg ha-1 de K2O.