There is a lack of yield data at landscape scale for biomass crops such as Miscanthus giganteus. Most yield data are from plot scale plantings on research farms rather than marginal lands where commercial scale entities are planting the crop, which are on soils which may not represent the types targeted by the expanding biomass industry. Crop yields vary across the landscape with biophysical factors, such as climate, topography and soils. These factors are very heterogeneous across the landscape, leading to large variations in crop yields, both within and between fields across the landscape. As part of a life cycle assessment (LCA) for miscanthus production, we have been tracking both within- and between-field yields at Bioenergy Crop Assistance Program (BCAP) project area 5 in Ashtabula County, OH. Our objective was to describe yield variation across the landscape for miscanthus and scale up this understanding of yield predictions using satellite data to other BCAP sites across a diverse climatic gradient. Topographic attributes (slope, aspect, profile, plan and mean curvature, and wetness index) within each BCAP region were used to characterize fields, identifying characteristics which favor yield.
Results/Conclusions
For the LCA, we found that although fuel use was higher for land preparation in fields with perennial vegetation, fuel to harvest miscanthus dominated greenhouse gas (GHG) emissions from agriculture machinery for crop management. The nitrous oxide emissions and changes in soil carbon were the largest source and sink of GHG emissions associated with miscanthus production, respectively. In using satellite imagery to estimate crop biomass yields, we found that although the Enhanced Vegetation Index (EVI) saturated as yields increased during the season, the Normalized Difference Water Index (NDWI) was less prone to saturation, demonstrating a linear relationship with wet biomass yields.