Atributos químicos, físicos e biológicos do solo e produtividade da soja após sistemas de renovação de pastagem

Abstract

A large portion of the Brazilian Cerrado pastures is affected by some degree of degradation, where one of the main challenges is incorporating these areas into a crop production system with the aim of increasing agricultural productivity without having to clear new areas. In this vein, this study aimed to identify a pasture renewal system that provides improvements in soybean yield and chemical, physical and biological properties, considering two texture classifications. The experiments were carried out in the municipalities of Batayporã (medium-texture soil) and Vicentina (sandy soil), both in the State of Mato Grosso do Sul, from September 2018 to March 2020. In both study sites, the experiment adopted a randomized block design, with four replications and eight pasture renewal systems, namely: 1) soybean – off-season rainfed maize – soybean; 2) soybean – off season rainfed maize intercropped Brachiaria ruziziensis – soybean; 3) a soybean crop; 4) Panicum maximum for 8 months then a soybean crop; 5) P. maximum intercropped with Crotalaria ochroleuca for 8 months then a soybean crop; 6) P. maximum for 12 months then a soybean crop; 7) P. maximum intercropped with C. ochroleuca for 12 months then a soybean crop; and 8) the original pasture (control). Soil chemical, physical and biological traits and soybean yield components were evaluated. Data were submitted to analysis of variance and means were compared by Tukey (P≤0.05). System 8 showed higher toxic aluminum contente and potential acidity compared to Other systems. Systems 3 and 7 showed higher total porosity and soil macroporosity compared to system 2, and the other systems did not differ from systems 2, 3, and 7. Soil microbial biomass carbono was lower in system 1 compared to systems 6, 7 and 8. The activity of β-glucosidase was higher in system 6 compared to systems 1 and 3, and the other systems did not differ from systems 1, 3 and 6. Arylsulfatase showed higher activity in system 6 compared to system 3, and the other systems did not differ from systems 3 and 6. Acid phosphatase was lower in system 3 compared to system 6, and the other systems did not differ from systems 3 and 6. Soybean grain yield was higher in systems 6 and 7, compared to systems 1 and 3, and systems 2, 4 and 5 did not differ from systems 1, 6 and 7. The use of Panicum maximum alone or intercropped with Crotalaria ochroleuca provides improvements in soil quality and contributes to higher soybean yield. Pasture renewal with the off season rainfed maize - soybean succession reduces soil quality and impairs soybean yield.