PHYSICAL AND WATER CONTENT CHANGES IN A RED-YELLOW PODZOLIC SOIL INDUCED BY TILLAGE

Abstract

Soil management systems differ in relation to topsoil mobilization and surface cover, resulting in differencesin soil physical attributes that can affect yield and environmental quality. Aiming the evaluation of some of these parametersand soil water dynamics in a winter crop, in southem Brazil, an experiment was conducted at the Estação ExperimentalAgronômica of UniverSidade Federal do Rio Grande do Sul, RS-Brazil, on a Red-yellow Podzolic soil under conventional tillageand no-tillage, for three years, both in a maize-oat/vetch rotation. Undisturbed soil samples were used to obtain bulk density,pore size distribution, soil water retention curve and hydraulic conductivity from the surface up to 0.70 m depth, determiningthe internai drainage at 0.60 m. Soil water dynamics, during the oat/vetch, cycle was monitored using tensiometers. Higherdifferences were observed at the depth of 0.20 m, where conventional tillage resülted in lower macroporosity and highermacroporosity, higher soil water retention, and a lower saturated and unsaturated hydraulic conductivity. These differences ledto a higher soil moisture content at 0.10, 0.20 and 0.30 m in conventional tillage, and a faster drainage at 0.60 m for the no-tillagetreatment. Therefore, it is concluded that significant physical changes have occurred in the soil after three years of implantationof the tillage systems, with higher water retention, under conventional tillage at 0.20 m, and drainage, under no-tillage.