INFLUENCE OF SIMULTANEOUS CHANGES IN SODICITY AND pH ON THE HYDRAULIC CONDUCTIVITY OF AN ALKALI SOIL UNDER RICE CULTURE

Abstract

In a laboratory study we evaluated the chemical significance of PCO2 buildup, visà-vis reduction in soil pH and sodicity on the associated increase in hydraulic conductivity (HC) for rice culture conditions. Soil HC was determined at constant hydraulic head in soil columns packed to a bulk density of 1.47 g cm−3 and flushed with CO2 to obviate air entrapment in the presence and in the absence of farmyard manure (FYM) and rice. Hydraulic conductivity of alkali soils generally was least improved by continuous submergence, but was more improved in FYM-treated soils. Growing rice further increased the HC of soils. Exchangeable Na removal and reductions in pH appear to be directly related to the amount of CO2 production in calcareous strongly alkali soils. It seems that the physical presence of an active root system yields a certain HC, but chemical reclamation is primarily through more CO2 production. Organic manures improve rice growth because they raise PCO2 to reduce pH and sodicity through greater mobilization of soil lime.