Effect of frequency of sodic and saline-sodic irrigations and gypsum on the buildup of sodium in soil and crop yields

The effect of three frequencies of irrigation with sodic (high residual alkalinity) and saline-sodic (high residual alkalinity and high NaCl concentration) waters in presence and absence of gypsum application on soil properties and crop yields were investigated under millet (fodder) — wheat — maize (fodder) rotation in a field experiment carried out for 6 years (1986–1992) on a well drained sandy loam Typic Ustochrept soil. Irrespective of the irrigation intervals, sustained use of sodic and salinesodic waters increased pH, electrical conductivity and ESP of the soil and hence significantly decreased crop yields. Application of gypsum decreased ESP and significantly improved crop yields. The beneficial effect of gypsum was lower under saline-sodic irrigation. There were no significant beneficial effects of increasing the frequency of sodic and saline-sodic irrigation, both in presence and absence of applied gypsum, on the yields of wheat and millet (f) crops grown during winter and monsoon seasons, respectively. But decrease in irrigation interval significantly improved yields of maize (f) grown during the hot dry summer period. Frequency of irrigation did not appreciably alter the effectiveness of applied gypsum in wheat and millet (f) but in maize (f), the gypsum treatment was more effective under more frequent irrigation.