Soil compaction and least limiting water range in dryland rice yield

Abstract

The objective of this work was to determine the least limiting water range and its relation with dryland rice yield in a medium texture Oxisol. The treatments were 0, 1, 2, 4 and 6 passed of a tractor, side by side, on soil surface. The experimental design was a completely randomized, with four repetitions. Indeformed soil samples were collected in the layers 0.02–0.05, 0.07–0.10 and 0.15–0.18 m for determination of soil resistance to penetration, bulk density, least limiting water range, critical bulk density and soil water retention curve. In 3.6 m² plots dryland rice (cv. Caiapó) was sown and its yield in useful parcels of 1.80 m² was evaluated. The least limiting water range was reduced from bulk density of 1.30 Mg m^-3 by soil resistance to penetration. From 1.82 MPa on decrease of rice yield occurred. Critical bulk density to root development in the least limiting water range was 1.63 Mg m^-3, equivalent to 1.62 Mg m^-3 of bulk density, that is critical to rice yield. The monitoring of soil compaction is necessary to prevent losses in dryland rice yield.