Excessive Biomass Removal From Energy Crops Increases Loss of Sediment and Nutrients in Runoff.

Excessive removal of biomass from energy crops as feedstocks for cellulosic ethanol production may increase loss of non-point source (NPS) water pollutants such as sediment and nutrients in runoff. The extent of the effects of biomass removal from energy crops such as row crops and warm season grasses on NPS pollution has not been widely documented. This study quantifies the impacts of variable rates of biomass removal from switchgrass plantations and wheat and sorghum fields. In the first study, four treatments consisting of cutting switchgrass at 0, 5, 10, and 20 cm heights were established in small plots (1 m by 2 m) in an existing switchgrass field. In the second study, six treatments consisting of cutting wheat and sorghum stubble at 0, 20, 40, 60, 80, and 100% of the original height after harvest were established in small plots in no-till fields. The second study received beef cattle manure at 0, 5, 10, and 15 Mg ha^-1. The experiments were established in a randomized complete block design. Simulated rain was applied at 75 mm h^-1 to both experiments. Sediment, soil organic carbon, and nutrients lost in runoff are being measured from each experiment. Relationships between pollutant loss in runoff and residue removal and manure application rates are being developed to determine the optimum rates of manure application and permissible levels of residue removal. Results will be discussed at the meetings.