Resumo A longa duração do sistema plantio direto tem causado limitações para o solo, como a compactação e a acidez subsuperficiais. O objetivo deste trabalho foi avaliar os efeitos de estratégias de manejo sobre os atributos do solo e a produtividade da soja. O experimento foi realizado em um Latossolo nas safras agrícolas de 2016/17 e 2017/18 e seu delineamento experimental foi de blocos ao acaso com três repetições. Os tratamentos foram constituídos pela aplicação de estratégias de descompactação (escarificação e subsolagem) e de melhoria química (óxido de cálcio e magnésio, calcário e gesso), utilizadas de forma isolada e combinada. As amostragens de solo para análise química e a determinação da resistência à penetração do solo foram realizadas 6 e 18 meses após a aplicação dos tratamentos. A escarificação e a subsolagem foram eficientes na redução da resistência à penetração, mas apresentaram efeito temporário no solo. A subsolagem intensa associada à aplicação profunda de óxido de cálcio e magnésio, após 18 meses da aplicação, incrementou os valores de pH e os teores de cálcio e magnésio, além de neutralizar a saturação por alumínio até 60 cm. Em ambas as safras avaliadas, não houve efeito significativo dos tratamentos sobre a produtividade da soja.

Abstract The long term use of the no-tillage system has caused limitations to the soil, such as the subsurface compaction and acidity. The aim of this study was to evaluate the effect of management strategies on soil attributes and soybean yield. The experiment was carried out in the 2016/17 and 2017/18 crop seasons and its experimental design was a randomized blocks with three replications. The treatments were constituted by strategies of physical improvement (chiseling and subsoiling) and chemical improvement (calcium and magnesium oxide, limestone and gypsum), isolated or combinated. Soil samplings for chemical analysis and determination of resistance to soil penetration were performed 6 and 18 months after application of treatments. The chiseling and subsoiling were efficient in reduction compaction, but presented temporary effects in the soil. The intense subsoiling associated with the deep application of calcium and magnesium oxide, 18 months after the application, increased the pH values and the calcium and magnesium contents in addition to neutralizing the aluminum saturation to the depth of 60 cm. In both evaluated seasons, there was no significant effect of treatments on soybean productivity.

The processes of water transfer in the soil-plant-atmosphere system are strongly affected by soil use and management. Differences in the dynamics of soil water transfer between no-tillage (NT) and conventional tillage (CT) practices during a soybean (Glycine max) growing season in southern Brazil were assessed in this study. All the water balance components were analyzed during the soybean growing season (2009/2010). Rainfall, runoff, soil water storage and hydro-physical soil properties were analyzed under two tillage systems. The land-atmosphere water vapor exchanges, obtained from eddy covariance stations, were analyzed with regard to the soybean agroecosystem. Characterizations of soil water storage were also formulated in the 2006/2007 and 2008/2009 soybean growing seasons under the NT system. During the periods without rain, the soil water content under NT was greater than under CT. The soil superficial layer, more porous under NT, contributed to less runoff during rainy events. Moreover, under NT conditions the water supply was always high, between 0.2 - 0.5 m. The total evapotranspiration in the soybean agroecosystem growing season was 410.8 mm.