Fontes de potássio na adubação de cobertura do algodoeiro produtividade, diagnose foliar, qualidade de fibras e análise econômica

Abstract

An experiment was carried out on a commercial cotton crop, in Sapezal MT, in farm year 2007/2008, with the objective of evaluating the effect of different sources of potassium in cover fertilization, on biometric attributes, production components, quality of fibers, economic viability and the nutritional status of cotton plants. The outline used was complete blocks at random, with five repetitions, whose treatments were comprised of cover application of 100 kg ha-1 of K2O from sources KCl, K2SO4, KNO3 and K2SO4.2MgSO4. The nutrient content found in the cotton leaves at blooming was evaluated, being interpreted by the critical level method and by the DRIS method. Both critical level method and DRIS were efficient in detecting differences in leaf nutrient contents and, the content of S in cotton leaves was highest for applications of fertilizer with K2SO4.2MgSO4. IBN was coherent between its values and the productivity of the treatments, with the highest productivities being obtained with the lowest IBN in potassium cover fertilization with the source K2SO4.2MgSO4. Potassium based fertilization of the cover with source K2SO4.2MgSO4 afforded highest plant height and higher agricultural productivity, however, these results were not confirmed by increased fiber quality and economic profitability of the cotton crop. Given its lower cost, KCl is the most economically viable source of fertilizer K for cover of cotton crops.