MACROPOROSITY CONTRIBUTION TO WATER FLUX OF A SOIL UNDER DIFFERENT TILLAGE SYSTEMS

SORACCO C.G.; LOZANO, LUIS ALBERTO; BALBUENA, ROBERTO ; RESSIA, J.M.; FILGUEIRA, ROBERTO RAUL

REVISTA BRASILEIRA DE CIêNCIA DO SOLO

SOC BRASILEIRA DE CIENCIA DO SOLO

Lugar: Vicosa; Año: 2012

0100-0683

The importance of soil macroporosity for the water transport properties of the soil makes its quantitative assessment still a challenging task. Measurement of hydraulic conductivity (K) at different soil water tensions, and quantification of water-conducting macroporosity (thetaM) in a soil under different tillage managements could help us to better understand the effects of these practices on the soil porous system and related hydraulic properties. The aim of this study was to assess the effects of Conventional Tillage (CT), Chisel Plough (CP) and No Tillage (NT) on thetaM, and on K; and to quantify the contribution of macroporosity to total water flux in a loam soil. A tension disc infiltrometer was used at two ascending soil water pressure heads (-5 cm, and 0) to infer thetaM, and K, during fallow. Macroporosity was determined based on the contribution of flow between 0 and -5 cm water potentials (K0, K5, respectively) in agreement with the Hagen-Poiseuille equation. The K0 values obtained were statistically higher for CT as compared to NT and CP. The K5 values did not differ statistically among treatments. Mean values of K varied between 0.20 and 3.70 cm/h. θM was significantly greater for CT as compared to CP and NT, following the same trend as K0. No differences in thetaM were detected between CP and NT. CT created water-conducting macropores that persisted until postharvest, whereas CP did not create persistent water-conducting macropores. These results support the idea that tillage affects soil water movement mainly through the creation of water-conducting macroporosity. Future studies on effect of tillage on water movement should focus on macroporosity.