Respostas da cultura da mamona às adubações mineral e orgânica combinadas, em solo do Semiárido do Nordeste do Brasil

Abstract

The fertilization of the soil, traditionally made with the use of mineral fertilizers, is one of the biggest costs of agricultural production. In this way, small and medium producers have difficulties in ensuring good soil fertility conditions. The objective of this study was to determine the combination of mineral fertilizer and organic fertilizer that gives the best answer for the growth and production of castor bean. The experiment was carried out between April and September 2014. The statistical design was randomized blocks, which were tested 25 treatments distributed in a factorial 5 x 5, with combined five doses of mineral fertilizer (0, 75, 150, 225 and 300 kg ha-1 of N + P2O5 + K2O in a ratio of 1: 1: 1) and five levels of fertilizer (0,1.25, 2.50, 3.75 and 5.0 t ha-1 composite castor bean cake). The experiment was conducted in the municipality of Crateús, state of Ceará. The soil of the region is a ultisol Yellow eutrophic, with sandy loam texture. The area was irrigated daily with a sprinkler system located dripline with 4.14 L of 1-time average flow, and the volume of water used was about 300 mm per month. It was evaluated the production weight components, number of fruit and seed weight of the primary raceme, number of racemes per plant, weight of 100 seeds, and yield, as well as the concentrations of macro and micronutrients in leaf of castor bean. The highest yield was achieved in the use of fertilizer combined with 3.75 tons ha-1 of organic fertilizer with 150.0 kg ha-1 of mineral fertilizer. The trend of castor productivity increase was observed for the organic fertilizer with 3.75 tons ha-1 of organic manure combined with mineral fertilizer to the maximum amount of 176.80 kg ha-1 of mineral fertilizer, with maximum production reached approximately 2372.0 kg ha-1. The production component that contributes most to the increase of castor bean productivity is the number of racemes per plant, which can substantially increase the amount of seed for cultivation area.