Leaching of salts as affected by the method of water application and atmospheric evaporativity under shallow and saline water-table conditions

Abstract

SummaryField studies on leaching a highly saline sandy loam soil having a shallow groundwater table showed that application of 150 mm water in two equal parts at 10 days interval had no distinct advantage over a single application of the whole amount. On the contrary, the surface-accumulated salts were displaced to a lesser extent and the salt peak remained at a shallower depth under split application, particularly during periods of high atmospheric evaporativity when the leached salts tended to move upward between successive water applications. A soil mulch created by shallow tillage reduced evaporation losses and curtailed upward movement of salts, resulting in nearly 10% increase in leaching efficiency. Significantly a small quantity of water (0·41 cm leaching water per unit soil depth) sufficed for 70% chloride removal, indicating that under the prevailing conditions a larger fraction of the pores contributed to the leaching process. A compact layer, having a bulk density of 1·69 g/cm3, at the soil surface, also appeared to be related to the higher leaching efficiency by maintaining a preponderance of unsaturated flow.