Monitoring Soil Water Chemistry During Establishment of Bioenergy Cropping Systems with Mixed Ion Resins: Limitations and Potential Improvements.

One of the potential benefits of producing cellulosic feedstocks for bionenergy production in the Lower Mississippi Alluvial Valley (LMAV) is that woody crops or perennial grasses such as switchgrass frequently requires lower inputs of fertilizer than other agronomic crops.  This may result in reductions in the amount of nutrient fluxes to subsurface and ultimately surface waters.  As part of a project evaluating the impacts of cellulosic crop establishment in the LMAV, soil water is being monitored using tension lysimeters and mixed bed ion resin lysimeters in areas with newly established switchgrass and cottonwood plantations, mature forests, and agronomic crop rotations (soybean-grain sorghum) typical of the region.  Data collected by the two types of lysimeters will be compared to evaluate the ability of these different lysimeters to monitor soil water chemistry within the different cropping systems.  In addition, lab tests are being used to evaluate the efficiency of the mixed bed to capture and then, following extraction, release different nitrogen and phosphorus ions given the diverse chemistry of the soil solutions collected from these crops.  Extraction of some types of mixed bed resins can release amine groups which are present in the resins prior to field deployment.  Lab tests are also being performed to determine if pre-treating mixed bed ions to neutralize the pH of the extracted solutions will reduce contamination of the extracted solutions with these amine groups.  Results from these comparisons and tests will be presented and used to asses the ability of mixed bed resins lysimeters to monitor water chemistry in these cropping systems.