Dinâmica da água no solo em plantio direto com e sem terraço

Abstract

The decrease in runoff and the increase in infiltration are benefits of agricultural terraces. However, the contribution of terracing to the water storage in the soil and to the available water storage to plants is still not well understood. The aim of this study was to analyze a data series on soil water content, monitored in an area with and without terrace, to evaluate if there is association between terraces and available water storage in Nitisol under no till. For this purpose, two zero-order paired catchments under no till cultivation (soybean and wheat/turnip/corn succession), with and without broad-based terraces, were monitored in the period from 03/01/2016 to 02/28/2017 and 03/01/2017 to 02/28/2018. In each catchment, two points were demarcated, in the high and low terrain position, where data of soil water content, precipitation, runoff, field capacity and permanent wilting point were obtained. The relative water storage was higher the thicker the layer considered, and the variations were more accentuated in the shallow layers in the two catchments, with the top points having less variation. The presence of broad-based terraces positively affects the available water storage to plants in years with lower accumulated rainfall, when the functionality of the terraces is more evident, as in the first period of the study. In years with higher cumulated rainfall, the presence of terraces is not related with the available water storage to plants but acts to control runoff. In the relative available water, the differences in favor of the terrace were also more evident the thicker the layer considered. It was clearly notable that shortly after the rain, there was a dampening of the decrease in available water on the terrace, with a gradual decrease in the available water. In general, both in the high and low position, terracing positively affected the available water. However, the positive association between the terrace and the available water was more evident in the position where more upstream terraces were considered.