Effects of applying calcium salts to coastal saline soils on growth and mineral nutrition of rice varieties

A greenhouse experiment was conducted with 3 coastal saline soils, viz. Ramgati (Aeric Fluvaquent), Nalchiti (Aeric Haplaquept), and Jhalakati (Typic Haplaquept), representing 3 salinity levels. Calcium (Ca) salts in the form of nitrate, chloride, sulfate, and phosphate (dibasic) were added to maintain the ratio of 1 :5 for Na: Ca on the basis of the content of sodium (Na) and Ca in all soils. Two varieties of rice (Oryza sativa L.) (BR-11 and Pokkali) with varying salt tolerance were grown on the soils under submergence for 30 days. Salt injury symptoms such as chlorosis and necrosis on leaves of plants receiving no additional Ca (control) were observed and the severity of symptoms varied among the soils. Pokkali was less affected by salinity than BR-11 and produced greater dry matter yield on all soils. In comparison to control plants, application of calcium phosphate (CP) and calcium sulfate (CS) to soils tended to ameliorate the detrimental effects of salinity stress on dry matter yield. On the other hand, a decrease in dry matter yield was obtained with calcium chloride (CC) and calcium nitrate (CN). This suggests that maintaining a constant Na:Ca in the growth medium with Ca salts (CP and CS) having lower solubility seems to be effective in the amelioration of salinity stress regardless of its level. Concentrations of nitrogen (N), phosphorus (P), potassium (K), and Ca in shoots and roots of two varieties of rice plants decreased with increasing salinity levels, while results obtained with Na and magnesium (,Mg) were opposite. Application of CP and CS increased N, R K, and Ca and decreased Na and Mg concentrations when compared to control plants grown on all soils. The decrease in Na and Mg concentrations was less pronounced in BR-11 as compared to Pokkali. In general, CP was more effective than CS in the acquisition of essential macronutrient elements (except Mg), which was higher in Pokkali than BR-11.