Gypsum applied to the surface or mixed into the 2.5-cm depth decreased P and increased NH4–N leaching and mobility in the soil profile but did not affect NO3–N. In general, exchangeable Ca–Mg treatments did not affect leaching or nutrient mobility in the soil, except for particulate P and total P in the leachates. For these, there was significantly less leaching in the Ca-treated soil than the Mg-treated soil. The overall practical conclusion for farmers and agronomists is that to control P leaching, it is necessary to add gypsum as a Ca2+ electrolyte source, even when the soil exchangeable Ca/Mg ratio is high. Application of gypsum to the soil could be recommended as a best management practice to avoid water pollution by reducing P transport from the soil to water, but it could cause environmental problems by increasing the NH4 soil mobility.

Please click here for full article.