Descompactação mecânica e biológica em terras baixas e seus impactos nos atributos físicos do solo

Abstract

In lowland soils, normally cultivated with irrigated rice, there is the presence of compacted subsurface layers, which restrict the development of roots of other rainfed crops, limiting the exploitation of nutrients and water from the soil. In this sense, the general objective was to determine the effect of mechanical soil decompaction, through scarification, associated with biological decompaction, with the implementation of a soil cover in the off-season, on penetration resistance, porosity (micro and macroporosity) and soil density, antecedent to the sowing of rainfed crops. The experiment was conducted in the 2021/22 off-season, at the IRGA Regional Research Station, in Cachoeira do Sul - RS. It was composed by the interaction of three factors, namely: soil preparation (Factor 1, chiseling and non chiseling), soil cover (Factor 2, oats, ryegrass, ryegrass and oats, ryegrass and Persian clover, fallow and Persian clover) and by different soil layers (Factor 3, 0.00 to 0.05, 0.05 to 0.10, 0.10 to 0.15 and 0.15 to 0.25 m). The experimental design was randomized blocks, with four replications. Scarification was carried out with a five parabolic shank scarifier, set to a working depth of 0.25 m, on 04/9/2021. The sowing of cover crops was in line, on 04/23/2021. The desiccation of the area was carried out on 09/24/2021 and after 41 days, the resistance to soil penetration was determined, together with gravimetric moisture and the collection of soil samples with preserved structure was carried out, to determine the density, total porosity, macroporosity and microporosity. The soil mechanical and biological decompaction reduced the penetration resistance values by 42.95%. In all studied layers, except for layer 0 to 5, there was a reduction in PR with the management of chiseling. As single ryegrass and intercropped with Persian clover, with better performance in reducing this variable. Oat, regardless of soil mobilization or not, reduced the density value and increased the total soil porosity. Regarding microporosity, significant reductions were found in the first layer, in the scarified area together with the intercropped ryegrass and oat. The Persian clover was the treatment that provided greater macroporosity in the soil. Soil scarification was responsible for increasing soil macroporosity up to 0.10 m.