Impact of Gypsum Application on Bermudagrass (Cynodon dactylon L.) Forage Production and Soil Properties.

Soil degradation and compaction are considered two of the most important problems of cultivated forage systems. Gypsum has been used as an agricultural soil amendment for over 250 years. It is a soluble source of calcium and sulfate-sulfur for crops and has been shown to improve soil physical and chemical properties. A study was conducted at Mississippi State University from 2012 to 2014 to determine the effect of gypsum on forage production and quality, nutrient availability, and soil physical (bulk density, aggregate stability and organic matter) and chemical properties (pH, soil mineral content, CEC and base saturation).  The study was conducted on a 10-yr old bermudagrass stand as a randomized complete block design replicated three times.  Treatments included a check, lime (2240 kg/ha), three gypsum rates (560, 1120 and 2240 kg/ha) and lime x gypsum combination.  Nitrogen was applied to all treatments using urea-ammonium sulfate (33-0-0S) at a rate of 112 kg N/ha/yr in four split applications of 28 kg N/ha.  Phosphorus and potassium were applied based on soil test recommendations.   One soil core sample was taken from each plot to a 50-cm depth at 3 depth increments (0-15, 15-30, and 30-50 cm) at the beginning (May) and end (November) of the growing season to monitor changes on aggregate stability, organic matter and soil mineral content.   There was no significant difference among treatments in seasonal biomass production within each year.  Forage quality was largely affected by harvest date and not by treatments. Changes in water soluble aggregates were observed between May and November, but not to treatment effect.   Mineral content, BD, OM, pH, CEC and base saturation were mainly impacted by soil depth.  Further studies with higher rates of application and more long-term data collection need to be explored to quantify the impact on soil quality and biomass production.