Desalinization of a salt-affected soil in plots of various sizes under two modes of water application

Abstract

SummaryLeaching in a salt-affected, permeable, sandy loam soil was evaluated under continuous and intermittent ponding conditions in 2 × 2 m (S1), 4 × 4 m (S2) and 6 × 6 m (S3) plots. The soil contained large amounts of soluble salts throughout the profile to the water table, chiefly chlorides and sulphates of sodium, calcium and magnesium. The leaching curves did not differ significantly between Slf Sa and S3 plots under continuous ponding but did under intermittent ponding. The leaching efficiency decreased sharply with increased plot size. The leaching efficiency in Sj plots was significantly greater with intermittent than with continuous ponding, but the reverse was true in S3 plots. The displacement of the resident soil solution in S1 plots under intermittent ponding was nearly piston-like. With increased plot size, it tended to deviate from this behaviour. The leaching curves from S3 plots (this size being reasonable in farmers' fields) were compared with those obtained from numerical solution of a simplified steady-state salt transport model. The model also included a source term, solubility rate constant, for the slightly soluble salts present in the experimental soil. The pore water velocity was estimated from field capacity and time-averaged infiltration rate. The effective dispersion coefficient and solubility rate constant were estimated by a least-squares minimization technique. A reasonably good agreement was obtained between simulated and experimental leaching curves. For practical purposes, this simple model may be adequate to predict leaching in salt-affected soils similar to the one under consideration.