NUTRIENT REMOVAL BY OFF-SEASON GRAIN SORGHUM AS AFFECTED BY INTERCROPPING WITH RUZIGRASS AND FERTILIZATION LEVELS IN THE BRAZILIAN CERRADO

Sorghum is an off-season crop option in succession to soybean in the Cerrado region, but many producers underestimate the fertilization requirement, which can harm the productive performance of the system as a whole. Aiming to quantify the uptake and export of nutrients by grain sorghum, experiments were carried out in monocropping and intercropping with ruzigrass (Uroclhoa ruziziensis), with three levels of NPK fertilization (control without fertilization; maintenance fertilization; and maintenance + 30%). The experimental design was randomized blocks, with four replications. Sorghum plants were sampled at 33, 67 and 130 days after sowing, corresponding to the eight-leaf, flowering and physiological maturation development stages. The nutrient accumulation throughout the sorghum cycle and the respective extraction and export rates were calculated. Intercropping with ruzigrass reduces grain yield, but does not influence sorghum nutrient accumulation. Fertilization in soil with current high fertility increases biomass and nutrient accumulation, however, without any impact on grain yield. In off-season sorghum crop, nutrient uptake occurs mostly during the vegetative phase. Each ton of grain produced removes the equivalent of 14.5; 5.0; 3.5; 1.1 and 0.5 kg of N, P2O5, K2O, Mg and S, in addition to 2, 2, 25, 9 and 11 g of B, Cu, Fe, Mn and Zn, respectively. The potential for nutrient removal by grain sorghum cultivation is comparable to the patterns of the off-season maize crop, evidencing the importance of fertilization to replenish the amounts of nutrient exported.