ATRIBUTOS DE PLANTAS E DE FERTILIDADE DO SOLO SOB ADUBAÇÃO POTÁSSICA EM SISTEMA INTEGRADO DE PRODUÇÃO AGROPECUÁRIA

Abstract

The Integrated Crop-Livestock System (ICLS) is in a form of integrated production, which achieve a higher environmental, economic and social sustainability. Because of the efficient nutrient cycling and biodiversity of crops, the system combines food production with environmental conservation. The lack of research in the context of the potassium (K) dynamic in subtropical soils under ICLS and how the shading provided by the arboreal component alters the production, determined the focus of this research. The main objective of this project consists in evaluating the effects of shade (provided by eucalyptus) on the attributes of plants and soil fertility under conditions of K rates (0, 100, 200 and 300 kg ha-1 yr-1 K2O) applied on the soil surface in the entire area. Two experiments are being conducted simultaneously in an Typic Hapludox on a model farm of the Agronomic Institute of Paraná (IAPAR), Ponta Grossa (PR). The experiment employs an experimental design in randomized complete block with split plots and three replications. The plots (4 x 24 m) consists of annual plants (corn, oat and soybean) and the distances considered in relation to eucalyptus (shading effect) were: 0-4, 4-8, 8-12 and 12-16 m. The subplots (4 x 6 m) receive doses (0, 100, 200 and 300 kg ha-1 yr-1 of K2O) K (as potassium chloride), at the soil surface at the time of seeding culture of autumn-winter (oat) and at seeding of the summer crop (corn and soybeans). The second experiment was also a randomized complete block design with split plot and three replications. The plots were characterized by rows of eucalyptus and subplots doses of K (similar to the first experiment). In the maize crop (2012/13 and 2014/15) and soybean (2013/14) were evaluated nutritional status (for macronutrients) and grain maize yield (GYM and GYS). During oat growing (2013 and 2014) were evaluated the dry matter yield (DMY), height and macronutrient accumulation. The evaluation of nutritional status of eucalyptus was conducted in the summer (2013/14), and the nutrients in the leaf litter under the canopy. Soil samples of layers 0-5, 5-10, 10-15, 15-20, 20-40 and 40-60 cm were performed in both experiments at 6, 12 and 30 months after the start of the experiment (Sep / 2012). After that, was determined pH concentration, H + Al, C, Ca, Mg, K, Al, CEC and effective CEC (ECEC), base saturation (%) and aluminum (m%) and the percentage of K, Ca and Mg in the effective CEC. In general, higher concentrations of cations was observed in less shaded transects, which favored the largest DMY for oats/2014 (2218.83 kg ha-1) and GYM (10,470.1 kg ha-1 in 2012/13 and 8742, 5 kg ha-1 in 2014/15) and GYS (1989.0 kg ha-1). Moreover, high concentrations of Ca and Mg were detected in the whole profile favoring saturation in these ECEC in second experiment. Leaching was not observed in profile in the second experiment. The concentration of N, P and K in shoots of eucalypt was within the proper range, but the opposite was observed for Ca, Mg and S. The reduction of the concentration of N, P, K, Mg and S in the litter, may indicate a biochemical decomposition. However, the concentration of Ca in the litter, suggests the influence of biogeochemical cycling. K doses did not affect the production of eucalyptus at 8 years.