Soil physical quality on tillage and cropping systems after two decades in the subtropical region of Brazil

Abstract

Sustainability of crop production systems depends on the preservation of soil physical quality over time. This study aimed to determine long-term effects of soil tillage and cropping systems on physical attributes and hydraulic properties of an Oxisol in Southern Brazil, emphasising management practices to preserve or improve the soil structure quality under no-tillage system. The experiment was conducted in randomized block design, using a 5×2 factorial arrangement (tillage×cropping systems), with four replications. The five tillage systems consisted of conventional tillage (CT); minimum tillage, chiselled soil every year (MTC1); minimum tillage, chiselled soil every three years (MTC3); continuous no-tillage for 11 years (NT11); and continuous no-tillage for 24 years (NT24). The two cropping systems consisted of annual crop sequence with wheat in the winter and soybean in the summer, designated as crop succession (CS); and a 4-year crop rotation (CR) with white lupine-maize—black oat-soybean—wheat-soybean—wheat-soybean in winter–summer, respectively. Undisturbed soil cores were collected from 0–0.10; 0.10–0.20 and 0.20–0.30 m of soil depth, to determine the soil bulk density (BD), total porosity, macroporosity, microporosity, pore size distribution and classes, soil water retention curve, infiltration rate and field-saturated hydraulic conductivity. There was no interaction between tillage and cropping systems, and no effects of cropping systems on soil physical and hydraulic properties. Regardless the cropping system, chiselling effects on soil physical properties persisted for less than 22 months, and were restricted to below 0.20m soil depth. The CT resulted in soil pulverization at 0–0.10 m depth, leading to lower BD and higher macroporosity compared to the other soil tillage systems. At layers below 0.10m, CT increased the BD and reduced the macroporosity to critical levels for crop growth. Continuous use of no-tillage improved soil physical quality mainly at deeper layers, and provided higher plant available water retention in the soil at matric potentials ranging from −10 to −200kPa in relation to CT and MTC1. The adoption of NT improves soil physical quality and plant available water over time, and periodic soil chiselling aiming to disrupt compacted layers should be avoided because of its effects on reducing soil compaction level are short-lived.