Fate of gypsum surface - applied to an Appalachian hill pasture watershed

Low pH soils leached with gypsum solutions have been shown to sorb gypsum t hereby increasing calcium and improving root growth of some crops. However, in some situations, exchangeable aluminum is leached which could enter wat erways and potentially cause adverse off-site impacts. Due to relatively hi gh solubility, gypsum itself has potential to impact stream water chemistry . In this study, 8250 kg ha(-1) gypsum was applied to plots in a steep 4.3 ha-pasture watershed in central Appalachia. Changes in the 0-40 cm soil pro file and changes in water chemistry at a flume below a seep which drains th e watershed were measured in response to this application. After the end of the second growing season, and a total rainfall of 1.7 m, 46% of the appli ed gypsum calcium was still in the top 40 cm of soil. The rainfall had a 11 .4% efficiency rate of transporting gypsum out of the top 40 cm compared to movement of a saturated solution through an inert medium. Of the applied g ypsum sulfate, 3.4% exited the watershed through stream flow. Maximum gypsu m concentrations in stream flow, which occurred during a storm event, were 34 ppm or <1.5% of saturation levels. No detectable aluminum was measured i n stream flow at the flume. These findings indicate that as long as a minor part of watersheds such as this one has gypsum applied at rates less than 10,000 kg ha(-1), off-site environment impacts should be minimal. Published by Elsevier Science B.V.