Gypsum form and rate can affect soil physicochemical properties and crop productivity in soils of low electrical conductivity that have been enriched by sodium due to supplementary irrigation

Context The optimum gypsum form and rate required to ameliorate soil sodicity constraints caused by supplementary irrigation with water containing sodium bicarbonate in humid regions are unknown. Aim Evaluate the short-term effect of different gypsum forms and rates on (i) soil physicochemical properties and (ii) grain yield in a barley (Hordeum vulgare L.)/maize (Zea mays L.) sequence. Methods We conducted two field experiments in the southeastern Argentinean Pampas on soils with low electrical conductivity (0.2 dS m−1), assessing three forms of gypsum (granulated, pelletised, and powdered) applied a month before barley sowing at 2000 kg ha−1. In one experiment, 3000 kg ha−1 was also tested. Soil properties and grain yield were determined at barley and maize harvests (i.e. 7 and 13 months after the gypsum application, respectively). Key results (i) Gypsum did not significantly affect soil physical properties; (ii) powdered gypsum at 3000 kg ha−1 enhanced soil chemical properties at barley harvest, decreasing pH by 7% and exchangeable sodium percentage by 35%, while increasing the exchangeable Ca2+/Na+ ratio by 70% (0.0–0.1 m depth); (iii) powdered gypsum improved soil chemical conditions at deeper soil depths (0.1–0.2 m) at maize harvest; (iv) barley grain yield increased with gypsum application; and (v) maize yield was negatively correlated with soil pH and positively correlated with the Ca2+/Na+ ratio. Conclusions Powdered gypsum can rapidly improve soil chemical properties and increase crop yields. Implications Powdered gypsum, especially at 3000 kg ha−1, could be used to alleviate soil sodicity issues in the short-term.