Marcha de absorção e acúmulo de nutrientes na cultura do sorgo

Abstract

This study aimed to determine the uptake of nutrients and dry matter accumulation in different sorghum shoots, depending on growth stages in culture. It was carried out a field experiment, at the experimental farm of UNIMONTES, Janaúba - MG, under the conventional tillage, using two sorghum hybrids, a grain (DKB 599) and other forage (BRS 610). It was used a randomized blocks design with four replications and treatments arranged in a 9 x 2 factorial scheme, in which the first factor was collection times (TI =3 leaves, T2 = 5 leaves, T3 = 7 leaves T4 = floral differentiation, TS = 80*% leaf area, T6 = fully expanded leaves, T7 = pollen release, T8 = milky grains / pasty nand T9 = black layer) and the second factor was composed of the hybrids. The results were subjected to variance analysis, and significant differences were identified by F test (P <0.05), regression models were adjusted and applied the Scott-Knott test. The harvested plant material was separated into stems, leaves, grains and panicles. Later the plant parts were cleaned in distilled water, dried in a forced air circulation chamber (at 65 ºC until constant weight, it was determined and milled the dry matter. After that, the samples were sent to carry out chemical analysis (leaf analysis). lt was calculated the accumulation of each nutrient for each part of plant by the relation of the nutrient content in the dry matter of each part and then the values were transformed to kg ha. The accumulation of dry matter, macro and micronutrients in relation to the Phenological stages of sorghum followed sigmoidal model during the crop cycle, being that the maximum accumulated quantities were obtained at physiological maturity. The plants of forage sorghum and grain respectively accumulated nutrients in shoot in the following descending order: K> N> Ca> P> Mg> S and N> K> Ca> P> Mg> S. The highest concentrations of K and N respectively were observed in stems and grains. Manganese and iron were the micronutrients accumulated in larger amounts in the sorghum shoots, followed by boron, zinc and copper; however, Zn and (Cu were the most exported micronutrients.. For the conditions of the experiment, the best time to perform nitrogen and potassium fertilization in coverage is at 25 and 20 DAE. respectively. to the hybrid BRS610 DKB599.