A Novel Phosphogypsum Application Recommendation Method under Continuous No‐Till Management in Brazil

Abstract

Core Ideas Phosphogypsum application increases grain yield, particularly in acidic subsoils. Phosphogypsum rates can be based on Ca2+ saturation in the ECEC of the subsoil. We show a new method for phosphogypsum recommendation based on M5‐Rules. Phosphogypsum (PG) is used in tropical and subtropical agriculture when subsoil acidity is an important yield‐limiting factor. However, the conditions that increase crop yield under PG application in continuous no‐till systems remain unclear. In addition, the methods used in Brazil to estimate the PG requirements are sometimes imprecise. Thus, to develop an accurate method for establishing PG recommendation, a dataset from experiments performed in southern Brazil and selected published papers involving PG application on various Oxisols under continuous no‐till was analyzed by computational techniques of data mining using the M5‐Rules algorithm to create regression models. Experimental areas consisted of annual crops managed under a long‐term (≥10 yr) no‐till system. These included maize (Zea mays L.), soybean [Glycine max (L.) Merr.], wheat (Triticum aestivum L.), and barley (Hordeum distichum L.). Results allowed the proposal of a new method for establishing the PG requirement to increase Ca2+ saturation to 60% in the effective cation exchange capacity (ECEC) at the 20‐ to 40‐cm soil layer when this is lower than 54% using the following equation: PG (Mg ha−1) = (0.6 × ECEC – exchangeable Ca2+ content in cmolc dm−3) × 6.4. The PG rates indicated by this method agreed with those leading to the maximum economic yields obtained in most studies conducted on continuous no‐till soils in Brazil. The proposed method might be efficiently used when subsoil acidity is an important growth‐limiting factor.