Soybean Agronomic Performance Does Not Change with Gypsum Application in a Cambisol Submitted to Water Restriction in Southern Brazil

Abstract

Water stress is one of the main limiting factors for soybean crop development, and it may increase due to subsurface soil acidity. The use of agricultural gypsum is a way to improve the soil’s chemical conditions at depth and mitigate the undesirable effects caused by water restriction during drought periods. This study aimed to evaluate whether gypsum application increases soybean yield in water restriction conditions. The experiment was implemented in 2018 in a Humic Cambisol, Southern Brazil. The treatments consisted of two gypsum management procedures (with 1.4 Mg ha-1 and without application) associated with two water conditions (with and without water restriction). The water conditions were promoted by partially covering the soil with plastic tarpaulin sheets, and the of agricultural gypsum used was 1,400 kg ha-1. Soybean was grown in the crop years 2018/19 and 2019/20 to assess root attributes and yield and were analyzed soil’s chemical characteristics. Water restriction reduced soybean yield by 11.4 and 36.8% in the 2018/19 and 2019/20 harvests, respectively, whereas there was no response to gypsum application. The plants’ root system was not affected by the water conditions or gypsum management. It was concluded that water restriction reduces soybean yield, and agricultural gypsum does not mitigate such loss under de evaluated conditions, even though it positively changes some soil chemical parameters.