The tillage systems affect the soil structure, and influence the storage of water available to plants. The objective of the present study was to evaluate the effects of long-term (17 years) of conventional tillage (PC), reduced tillage (PR) and no tillage (SD) on soil physical properties related to water storage in a Loamy Acrisol, in Eldorado do Sul, Rio Grande do Sul State. Soil samples (0-2.5, 2.5-7.5, 7.5-12.5, 12.5-17.5 cm) were collected in a sequence of vetch/corn and in an adjacent native grass field. The soil in SD presented high organic carbon (CO) for the superficial layer and large soil resistance values for depth compared to the conventional tillage. There were no differences among tillage systems of macro and microporosity of the soil, but for PC the saturated hydraulic conductivity increased in depth. No physical restriction to the plant root penetration in the soil under the different tillage systems was verified, which agrees with observation of non-critical observed values of bulk density (1.35 - 1.65 Mg m-3), macroporosity (0.09 - 0.20 m³ m-3) and soil resistance (0.25 - 0.75 MPa). The water retention curves and the available water (AD = 10 kPa (field capacity) - 1.500 kPa (point of permanent wither)) were not influenced by tillage systems, being the low volume of available water (0.05 - 0.09 m³ m-3) related to the texture of this soil. In this case, the increase of the infiltration rate and decrease of water evaporation due to the maintenance of the plant residues on soil surface for reduced tillage and no tillage may contribute to increase availability of water in the initial phase of crop establishment in these systems.
soil water retention curve; saturated hydraulic conductivity; bulk density; porosity; penetrometer resistance
