Combinações de fontes fosfatadas e calagem na produção de sorgo e no acúmulo de macronutrientes

Abstract

The phosphorus fertilization has provided considerable increases in the production of sorghum, however there are few studies related to the use of different sources of phosphorus rates in the production of components and nutrient accumulation. In this sense, we aimed to evaluate different combinations of rock phosphate sources, reactive phosphate and lime on production and accumulation of nutrients in sweet sorghum. In the first crop, carried out in polyethylene pots, the design was in randomized blocks, with four replications, in a 2 x 6 factorial involving two limestone rates (with and without limestone) and six combinations of phosphate fertilizer at a dose of 90 kg ha-1 de P2O5: control (0 kg ha-1 de P2O5); 100% Itafós rock phosphate; 75% of Itafós rock phosphate + 25% single superphosphate; 50% Itafós rock phosphate + 50% single superphosphate; 25% of Itafós rock phosphate + 75% of superphosphate and 100% of superphosphate. The second crop, in the same pots and in the same design of the first one, the residual effect of phosphorus fertilization was used. In the first crop, the interaction between liming and P sources pointed higher dry matter production for treatments with higher single superphosphate rates, in the presence of lime, as the large amount of soluble P from that source associated with lower P adsorption, due to liming, increased the mass. The highest accumulation of macronutrients were the treatments with higher rates of single superphosphate, since this nutrient, being more available, help in the metabolic processes for the absorption of other nutrients. In the second crop, the interaction between liming and P sources pointed higher dry matter production in treatment with full use of rock phosphate in the presence of liming, in which the availability of P was in greater quantity since the solubilization conditions. This tendency also occurred in the nutrients accumulation, which showed higher content in the treatments with higher rates of rock phosphate, due to the gradual release of phosphorus, which favors the absorption of the others nutrients.