Resposta do feijoeiro a aplicação foliar de potássio

Abstract

Common bean is a crop of great importance for the state of Paraná. Aiming the success in the cultivation of this species, several techniques are adopted, seeking better conditions for the development of the plant. The foliar nutrients supply to the leaves is an alternative that aims to improve the physiological processes of the plant and increase productivity. In this study were evaluated the agronomic and physiological characters of two common bean cultivars exposed to K foliar spray in differents phonological stages. The experiment was performed in two years; at the first year in Bom Sucesso do Sul, Paraná, 2014/2015 crop season, with the carioca IPR Tangará common bean cultivar. The treatments were: water foliar spray application (200 L ha-1), Bulk® – composed by 20% of a complexing agent for amino acids + 12% of K2O (2 L ha-1 in 200L ha-1 of water) and Fainal K® - composed by 3% of N and 31% of K2O (2 L ha-1 in 200L ha-1 of water) applied in different stages and the combination of these ones: R5, R7, R8, R5+R7, R7+R8, R5+R7+R8. At the second year, 2015/2016 crop season, the experiment was conduced in Pato Branco, Paraná, using the carioca common bean cultivars IPR Tangará and IAC Imperador. For the both cultivars, the applications followed the same formulations and volumes of applications performed in 2014/2015 crop season, modifying just the phenological stages of application and his combinations, being, in this case: R7, R8, e R7+R8. In both years, the experimental design were in random blocks with three replications, in a bifactorial experiment, with different nutrient sources and stages of application. The agronomical characters evaluated were: number of pods for plant (NVP), number of grains for pods (NGV), thousand grain weight (MMG, g) and yield (RG) in kg ha-1, besides the nitrogen percentage (N), phosphorus (P) and potassium (K) in the leaves and grains, and the physiological characters: CO2 assimilation rate (μmol CO2 m-2 s-1), stomatal conductance (mol H2O m-2 s-1), intracellular concentration of CO2 (μmol CO2 mol-1), transpiration rate (mmol H2O m-2 s-1) and water use efficiency (%). The data were submitted to an analysis of variance and comparation of means by Tukey's range test (P<0,05). For all the variables analyzed, there was no significant interaction between K sources and phenological stages of application for the components of yield and physiological parameters of the common bean crop. For 2014/2015 crop season, considering all stages of application, it is noted that both KG and NG the highest average were to Fainal K®, with no difference for Bulk®, but showing higher to water application, due the product having in it’s formulation 31% of K2O, and 3% of N, but without brings increases in productivity. The foliar applications of potassium did not changed the yield components and physiological common bean parameters, independent of the nutrient source and application stage, not bringing productivity gains for both environments and cultivars evaluated.