Qualidade do solo e produtividade da soja após gessagem e cultivos de plantas de cobertura

Abstract

The aim of this study is verify the changes in physical, chemical and biological soil attributes and in soybean crop yield, under cover crops in the off-season and presence and absence of gypsum, in the western region of Paraná. Soil samples were collected in layers of 0-0,10 m, 0,10-0,20 m and 0,20-0,40 m, in three years of evaluation (2017, 2018 and 2019) in an experimental area located in Corbelia, Paraná State, Brazil. The experimental design was randomized blocks in split plots with four replications. In the subplots, agricultural plaster is applied. In the summer crop all plots were cultivated with soybeans. In winter cultivation, different crops were installed in the plots: T1 – (CU) Crotalaria juncea (L.) + Urochloa ruziziensis, T2 – (CP) Crotalaria juncea (L.) + Pennisetum glaucum (L.), T3 – (P.) Pennisetum glaucum (L.), T4 – (J) Crotalaria juncea (L.), T5 – (S) Crotalaria spectabillis (R.), T6 – (O) Crotalaria ochroleuca, T7 – Zea mays (L.) (Z) ), T8 – Urochloa ruziziensis (U), T9 – (A) ausence of cover crops in winter. It was evident that cover crops need an adequate rainfall index to demonstrate their main effects on the soil. The grain cultivation system with ausence of cover crops in the winter had deleterious effects such as lower yield and lower accumulated grain yield for the soybean crop. There was an increase in soil density, lower total porosity, a reduction in macroporosity, a decrease in organic carbon and soil enzyme content, all of which are indicative of physical and biological chemical degradation of the soil. However, there was a lower soil resistance to penetration, higher yields in the second and third year of cultivation, in addition to higher soil organic carbon content, lower basal soil respiration and higher levels of soil enzymes. Using the cover crops Crotalaria juncea (L.) + Urochloa ruziziensis provided excellent soil cover and higher nitrogen content in the grains. When using the cover crops Crotalaria juncea (L.) + Pennisetum glaucum (L.) there was a considerable increase in hydraulic conductivity in saturated soil in the layers of 0 – 0,20 and 0,20 – 0,40 m and greater stabilization of the soil aggregates. Crotalaria ochroleuca cultivation promoted the highest hydraulic conductivity of saturated soil in the 0 – 0.20 m layer. Cover crops such as Crotaralaria juncea (L.) showed excellent effect on hydraulic conductivity in saturated soil.