Atributos químicos e microbiológicos do solo e produtividade da soja em função de manejos de solo e de culturas

Abstract

No-tillage is widely adopted in Brazil; however, studies evaluating how different soil management methods used during system establishment influence the long-term dynamics of soil chemical and microbiological attributes are still limited. Therefore, this study aimed to evaluate the residual effect of different soil management systems used during the establishment of no-tillage, associated with autumn–winter crops, on soil chemical and microbiological attributes, as well as soybean yield. The experiment was carried out at Embrapa Agropecuária Oeste, in Dourados, MS, Brazil, on a very clayey dystroferric Red Latosol. The experiment followed a 4 × 4 factorial arrangement in a randomized block design and three replications. The first factor consisted of soil management practices: disc plow, moldboard plow, chisel plow, and no-tillage. The second factor comprised autumn–winter crops: maize, maize + Brachiaria ruziziensis, B. ruziziensis + Crotalaria ochroleuca, and a crop mixture (maize + B. ruziziensis + C. ochroleuca + C. spectabilis + Vigna radiata L.). Prior to soybean sowing, soil samples were collected to evaluate chemical attributes, and at the R1 stage to assess microbiological attributes. Soybean yield components were evaluated at the R6 stage, and grain yield was determined at harvest. Data were subjected to analysis of variance and Pearson correlation analysis, and means were compared using the Tukey test (P < 0.05). Soil management systems used during the establishment of no-tillage mainly affected soil chemical attributes, promoting nutrient redistribution within the soil profile, with phosphorus levels in the 10–20 cm layer ranging from 15.29 mg dm⁻³ under no-tillage to 24.96 mg dm⁻³ under disk plowing. Autumn-winter crops had a localized effect on surface phosphorus, with the highest value observed in the B. ruziziensis + C. ochroleuca intercrop (46.54 mg dm⁻³). Soil management systems resulted in residual effects on soybean yield components, such as 100-grain weight, but did not lead to significant differences in grain yield. It is concluded that soil disturbance associated with lime incorporation during the establishment of no-tillage promotes nutrient redistribution without negative residual effects on soil microbiota and soybean yield after four years.