Biomass Energy Cropping Systems: Biomass Yield and Soil Quality Implications.

Biomass is a potentially renewable source of energy. A field experiment was established in 2009 at Jonesboro, Arkansas to evaluate eastern gamagrass, switchgrass and biomass sorghum response to different nitrogen fertilizer sources on biomass yield and soil quality. Nitrogen fertilizers included municipal biosolids, poultry litter, urea and a control.  Throughout 2010 and 2011, switchgrass yielded greater biomass compared to gamagrass. Nitrogen fertilization increased yield compared to the control in all cases. Nitrogen use efficiency was greater for switchgrass compared to gamagrass. Switchgrass yielded greater biomass than gamagrass and, in extremely dry years, was greater than biomass sorghum. Treatments receiving no nitrogen indicate that sustainable production of bioenergy crops is not feasible without nitrogen fertilization in the Midsouth region on this type of soil. Soil aggregate stability tests showed a greater impact of the type of grass grown than the type of N used as fertilizer. However, the source of N had a greater impact on soil enzyme activity than did the grass type. Further investigation on nitrogen dynamics and nutrient partitioning is needed to develop productive and efficient bioenergy systems for this region.