Erosion Modeling of Biofuel Cropping Systems in California Using RUSLE2 and Opportunities for Sustainable Crop Adoption.

Environmental impacts stemming from biofuel feedstock production must be considered before broad-scale adoption in California can occur. Erosion is one of the most serious environmental concerns in agriculture; in addition to removing fertile topsoil and ultimately reducing or eliminating yield, erosion transports harmful substances (pesticides, fertilizer, sediment itself) from fields to aquatic systems, sometimes with ecologically devastating effects. This study assesses the severity of erosion from biofuel crop production systems through modeling with the Revised Universal Soil Loss Equation (RUSLE2). Two biofuel crops (canola, Camelina) were modeled for fields in the dry-farmed, rain-erosive Central Coast region (CC, slope 1-15%) and irrigation-erosive Central Valley fields (CV, slope < 1%); three additional biofuel crops (sweet sorghum, bermudagrass, sugarcane) were modeled only for CV, since they are unsuitable for CC locations. Modeling annual erosion values were generally lowest for sugarcane (0.007 t/ac/yr for CV) and highest for Camelina (2.1 t/ac/yr for CC, 0.027 t/ac/yr for CV). However, values for biofuel crops were comparable or somewhat lower than alternatives of barley (3.3 t/ac/yr for CC, 0.031 t/ac/yr for CV) and wheat (2.8 t/ac/yr for CC, 0.024 t/ac/yr for CV), and substantially lower than bare soil (2.1 t/ac/yr for CC, 0.03 t/ac/yr for CV). Findings indicate that biofuel cropping systems do not experience greater erosion than standard cropping systems. Including biofuel crops in rotation with existing crops during the winter rainfall season, when most erosion occurs, has potential to reduce erosion in the rugged hills of CC. Furthermore, biofuel crops may be used in orchard row middles as cover crops, resulting in erosion reductions while eliminating demand for new biofuel cropland.