In a laboratory study we evaluated the chemical significance of PCO2buildup, 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−3and flushed with CO2to 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 CO2production 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 CO2production. Organic manures improve rice growth because they raise PCO2to reduce pH and sodicity through greater mobilization of soil lime.