Effect of Ca:Mg ratio on soil sodicity at different levels of sodium adsorption ratio and electrolyte concentration

Abstract

A laboratory study on loamy soil (19.6% clay) with different quality waters varying in Ca : Mg ratio (1 : 1, 1 : 2, 1 : 4, 1 : 6, 1 : 8) at two levels each of salinity (6 and 12 dSm-1) and SAR (10 and 50) was carried out. Exchangeable sodium (ES), exchangeable sodium percentage (ESP), Na: (Ca+Mg) ratio and degree of dispersed clay in soil increased with increasing Mg concentration at both the levels of EC(iw) and SAR(iw). The percentage of dispersed clay was more with increasing Mg concentration at higher SAR(iw) with a lower level of EC(iw), while the reverse trend was observed with hydraulic conductivity of soil. The Ca : Mg ratio in the exchange complex decreased with increasing Mg concentration, EC(iw) and SAR(iw). Further Mg concentration in the exchange complex increased with Mg in water and EC(iw) and decreased with the rise in SAR(iw). The multiple correlations between different water parameters and soil characteristics, namely ESP, degree of dispersion and hydraulic conductivity, were calculated and regression equations were developed. The relative contributions of water parameters to ESP, degree of dispersion and hydraulic conductivity of soil were in the order SAR(iw) > EC(iw) > Ca : Mg; EC(iw) > Ca : Mg > SAR(iw), EC(iw) > SAR(iw) > Ca : Mg, respectively.