Application of Gypsum to Acid Oklahoma Soils Under No-till.

Soils can be naturally acidic due to lack of basics cations, weathering, and other factors. However, agricultural activity can decrease soil pH, resulting in an increase in plant toxic aluminum (Al3+). The objective of this work was to assess soil chemical quality after gypsum application in acid Oklahoma soils under no-till. Field trials were established at two commercial farms, Marshall and Geary, Oklahoma. The experiment consisted of six treatments: control (no amendment), 5 and 10 Mg ha-1 of gypsum (applied only in the first year), 2.5 Mg ha-1 of gypsum (annual application), lime (recomended rate according to the soil test buffer index to increase pH to 6.4), and lime + gypsum (recomended lime rate +  5 Mg ha-1 of gypsum). Soil samples were collected at three depths (0-7.5, 7.5-15, 15-30 cm). Saturated Paste, Mehlich 3, exchangeable cations, exchangeable acidity, pH, and electrical conductivity analysis were conducted on soils at 1 and 2 years after treatment application. One of the current conclusions is that even with low rainfall, soil properties were positively impacted after only 1 year, and was maintained after 2 years. Gypsum treatments increased calcium and sulfur in subsurface, and decreased Al3+. Gypsum was more soluble and mobile than lime after 1 year, and was more mobile in Geary than Marshall (different soils and weather conditions). Overall results suggested that gypsum has potential to alleviate problems in acid subsoils when lime cannot be incorporated.