Three Years of Corn and Soybean after Gypsum and Poultry Litter Amendment of an Acid Fragipan Soil.

Fragipan soil productivity under rainfed conditions is limited by physical and chemical constraints to root development and water acquisition. We examined the impacts of gypsum and poultry litter on subsoil chemistry and corn and soybean yield over a three-year (2012-2014) period, applying 0 and 6.7 Mg/ha of each amendment, in complete factorial combination, to a Sadler (fine-silty, mixed, semiactive, mesic, oxyaquic, Fraglossudalf) silt loam located at the West Kentucky Research and Education Center near Princeton. Because small differences were expected, there were sixteen replications of the four treatments. Soil samples were taken in 15 cm increments, to a depth of 60 cm (the depth of the fragipan), in the spring of each year. Corn and soybean were grown each year and rotated across side-by-side plot areas.  Canopy temperature was monitored. Leaf tissue was taken at growth stage R1 in both species. The gypsum raised subsoil calcium and sulfate to a depth of 45 cm during the first year, reaching 60 cm during the second year. Poultry litter had little impact on subsoil chemical properties. Both amendments raised crop yield, especially during the second and third years of study. Canopy temperature data was mixed, and both amendments lowered canopy temperature, but not at the same time. Yield was positively affected more by poultry litter than by gypsum, probably by nutritional enhancement as indicated by leaf tissue analysis.