ESTRUTURAIS E MECÂNICAS DE SOLO DE VÁRZEA CULTIVADO COM ARROZ IRRIGADO POR INUNDAÇÃO (1)

SUMMARY: STRUCTURAL AND MECHANICAL CHANGES IN A LOWLANDSOIL UNDER FLOODED RICE The conversion of natural areas for agricultural use can degrade the soil structure andincrease the occurrence of compression. This study aimed to evaluate changes in the physico-mechanical and hydro-physical properties of an Endoaqualf, caused by the conversion of anatural area into a rice field. Hydro-physical (density, porosity, macroporosity, microporosity,void ratio, and water retention) and mechanical properties (preconsolidation pressure,compression index, coefficient of decompression, and recovery rate) were evaluated in the horizonsA 1 (0.0-0.25 m), A 2 (0.25-0.51 m), Cg 1 (0.51-0.92 m) and Cg 2 (0.92-1.20+ m) in soil of anatural area and in Ap (0.0-0.17 m), A (0.17-0.40 m), Cg 1 (0.40-0.70 m) and Cg 2 (0.70-1.00+ m)of soil under rice. Cluster analysis showed that eight years of conventionally tilled rice underflood irrigation did not significantly alter the physico-mechanical and hydro-physical properties.However, rice cultivation increased bulk density and reduced the void ratio, total porosity andmacroporosity. The ratio of elasticity with bulk density, porosity and void ratio was affected bythe type of soil structure, since compression and decompression were higher in horizons withprismatic than with massive structure.Index terms: preconsolidation pressure, compression index, soil elasticity.