Nitrogen, Phosphorus and Potassium Removal By Perennial Energy Grasses Grown on Wet Marginal Land.

Prevention of nutrient runoff from agriculture production systems is a key concern facing the industry. On-farm efforts will lead to a proactive approach that has the potential to confer key ecosystem services. The overall goal of this study was to determine the best management practices for sustainable biomass production of perennial energy crops on marginal land while improving ecosystem services. Emphasis was placed on significant removal of nitrogen, phosphorus and potassium, with the intent of preventing nutrient leaching into waterways. A field study was conducted from 2012 to 2015 to understand the effects of species (switchgrass, Miscanthus x giganteus, prairie cordgrass, and a native grass mixture), N-rate (0, 56, and 112 kg N ha-1), and harvest timing [peak standing crop (PSC) and after a killing frost (AKF)] on nutrient removal. Biomass yields increased with increased application of nitrogen and yields were higher for PSC compared to AKF, with an exception for Miscanthus during the first two years after establishment. Species, N- rate, and harvest timing significantly affected nutrient concentrations in biomass and removals. Mean N, P and K concentration was 5.55, 1.22 and 5.27 g kg-1 for switchgrass, 5.97, 1.64 and 7.79 g kg-1 for Mxg, 6.36, 1.32 and 6.40 g kg-1 for pCG, and 5.53, 1.18 and 6.68 g kg-1 for the mixture, respectively. Nutrient removal for all species is higher overall with PSC than with AKF and with increasing application of nitrogen. For PSC, switchgrass had the highest nitrogen and phosphorus removal, while potassium removal was highest in the mixture. For AKF, nutrient removal levels did not show significant differences across species. From this study, we inferred there is considerable potential for perennial energy crops to remove excess nutrients when grown on a riparian buffer; however, a specific recommendation for species selection and best management practices will be dependent on the desired outcome.