Effects of desulfurized gypsum application on soluble salt in sodic soil and drainage water under rice cultivation

【Objective】 To explore the effects of desulfurized gypsum application on soluble salt in sodic soil and drainage water in paddy field.【Method】 A field experiment with three different application rates of desulfurized gypsum ［29.17（S1），16.68（S2） and 4.17（S3）t·hm^-2］was carried out to assess the improvement effect of sodic soil and soluble salt ions concentration.【Result and conclusion】 The results showed that the soluble salt ions concentration except for carbonate in drainage water remained constant after rice tillering rear, and pH, electrical conductivity (EC) and residual sodium carbonate (RSC) in drainage water basically stayed unchanged. Differences in soil EC between S1 and S2 treatments were statistically significant at 10-20 cm soil depth (P<0.05); soil EC increased with the increase of desulfurized gypsum application rates at 0-20 cm soil depth, however, the opposite trends were found for soil pH and sodium adsorption ratio (SAR). Improvement effects of S1 treatment on sodic soil were better than those of S2 and S3 treatments for 0 to 40 cm soil depth.