Measuring Soil Sustainability: Index for Bioenergy Cropping Systems.

To ensure the sustainability of the soil resource under a bioenergy cropping system, a field experiment was conducted in northeast Kansas. We tested the effectiveness of eight bioenergy plant species grouped between annual and perennial crops. Our main objective was to determine the sustainability of bioenergy cropping systems. There was significantly greater soil structural stability plus greater root biomass under the perennial crops but greater aboveground biomass in the annual crop. Differences in soil carbon measured to 1.2 m were not significant between energy crops after five years. Assessment of soil microbial diversity can be a sensitive indicator to management and can be used to illustrate the effect of management decisions on productivity and soil quality. Soil microbial community composition was assessed using phospholipids fatty acid (PLFA) analysis. To assess the bioenergy feedstocks, there is an urgent need to develop a transparent unbiased method to identify possible change in soil characteristics under bioenergy cropping practice. Although the methods and sustainability criteria used in this investigation provided key insights about different feedstocks, it is difficult to assess how well they will predict the long term sustainability of the soil given the short-term of the project.