Produção de matéria seca e absorção de macronutrientes pelo braquiarão, em função de níveis de saturação por bases do solo e fontes fosfatadas.

Abstract

Several forages experiments showed none or little response to liming, while other experiments demonstrated that tropical forages respond to rock phosphate, especially in acid soils. The objective of this work was to determine the effect of liming and rock phosphate on dry mater production and absorption of Nitrogen, Phosphorus, Potassium, Calcium and Magnesium by brachiarão (Brachiaria Brizantha, cv. Marandú) plants. The experiment was made in the greenhouse of ICA/UFRA using samples of an Yellow Latosol from Abaetetuba (State of Para, Brazil). A completely randomized experimental design with treatments arranged in a 4 x 4 fatorial, with four replications, was used. Treatments were four liming rates to increase base saturation of the soil to 20%, 60%, 80%, 100%; three sources of phosphorus (Arad Rock Phosphate - Arad, Triple Superphosphate - SFT, Arad Rock Phosphate plus Triple Superphosphate - Arad+SFT) and a control plot (without liming and rock phosphate). All phosphorus sources were applied at the rate of 100 mg P/kg of soil. Plant shoots of brachiarão were collected 46 days after emergency and the 35 days after first and second regrowth. Dry matter production was higher in SFT and Arad+SFT than in the other treatments. SFT and Arad+SFT showed the highest total dry mater production in 60% of base saturation. The increase in dry mater production slowed down with increases in base saturation above 60%. The highest total dry mater production (37,62 g/recipient) was observed in the Arad+SFT treatment at an estimated base saturation level of 61,31%. The absorption of all nutrients were not significantly affected by any of the phosphorus source, independent of the base saturation of the soil.