Does gypsum increase crop grain yield on no-tilled acid soils? A meta-analysis

Improving the chemical conditions for plant growth in the subsoil is especially difficult in no-till (NT) soil because of the low solubility of limestone. In this situation, gypsum may be recommended due to its ability to mobilize exchangeable Ca2+ and other basic cations associated with SO42- anions mainly in the soil profile, thereby alleviating Al toxicity. However, the response of crops to gypsum is contradictory and ranges from a substantial increase to a slight decrease in grain yield. In this work, a meta-analysis comprising 129 harvests of six different grain crops (930 observation pairs in all) was conducted to identify the conditions under which grain yield responds to gypsum and to establish criteria for optimal management of gypsum as an amendment for NT soils. Based on the results, cereals (maize [Zea mays L.], wheat [Triticum aestivum L.], white oat [Avena sativa L.], barley [Hordeum vulgare L.], and rice [Oryza sativa L.]) have a high probability (77-97%) of their grain yield being increased by gypsum application to soils, with Al saturation exceeding 5% in the 0.20- to 0.40-m layer. The average increase in grain yield was 14 and 7% in crops growing in the presence and absence of water deficiency, respectively. A positive response of soybean [Glycine max (L.) Merr.] to gypsum was observed in water-deficient soils with Al saturation exceeding 10%. Under these conditions, the probability of a positive response of soybean was 88%, and the average yield increase was 12%. Therefore, gypsum application decreases Al toxicity to plants and increases crop grain yields as a result in NT soils with high Al saturation.