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

Abstract

Leaching in a salt-affected, permeable, sandy loam soil was evaluated under continuous and intermittent ponding conditions in 2 x 2 m (Sj), 4 x 4 m (S 2 ) and 6 x 6 m (S 3 ) 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 S lf S a and S 3 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 S 3 plots. The displacement of the resident soil solution in S! plots under intermittent ponding was nearly piston-like. With increased plot size, it tended to deviate from this behaviour. The leaching curves from S 3 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.

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

“…The corresponding figures for CPS 2 and IPS 2l and CPS 3 and 1PS 3 were 69 and 80, and 69 and 262 cm. These results are also in accordance with those obtained by Dahiya et al (1985) for desalinization of the experimental soil in these plots.…”

“…Thus, any attempt to develop a reclamation technique for these soils based on the results of laboratory and micro-plot experiments would probably be fruitless unless the validity of such results was examined on practically manageable large fields. In a very recent study (Dahiya et al 1985) conducted on a highly saline-sodic, permeable, sandy loam soil in plots of different size, desalinization efficiency in 2 x 2 m plots was found to be significantly higher with intermittent than with continuous ponding, but the reverse was true in 6 x 6 m plots. In 4 x 4 m plots, it was independent of the mode of water application.…”

“…The area has been irrigated since 1925. The essential characteristics of the selected soil and details of the leaching experiment are presented elsewhere (Dahiya et al 1985). The salient features are given here.…”

“…The total area covered found adequate to predict leaching of soluble salts by salt-affected soils in the world is about 95-5 in these soils (Dahiya, Malik & Singh, 1981; million ha (Kovda & Szabolcs, 1979). About 0004 Pal & Poonia, 1982;Bresler et al 1982; Dahiya, million ha of land annually become unfit for Malik & Richter, 1983;Dahiya et al 1985). agricultural production because of this problem…”

“…The present information is part of this study. The previous paper (Dahiya et al 1985) deals with desalinization. The present paper deals with desodification in plots of these three sizes under intermittent and continuous ponding.…”