Hydrologic and water quality impacts from perennial crop production on marginal lands

Marginal lands are proposed as a viable option for producing biofeedstocks as these lands are not heavily engaged in agricultural production or may not be suitable for intensive row-crop food/feed production. However, meeting biofeedstock production goals will require large amount of marginal lands and the unintended consequences of producing biofeedstocks on marginal lands are not fully clear. The overall goal of this study was to evaluate the productivity of biofeedstocks on marginal lands and the potential impacts on hydrologic and water quality processes from the land use conversion. This study was conducted in the Upper Mississippi River Basin (UMRB). First, the suitability of marginal lands in this region was evaluated for the growth of three candidate biofeedstock crops, switchgrass, Miscanthus and hybrid poplar. The evaluation was conducted using a fuzzy logic based land suitability evaluation method. Then, the simulation of switchgrass and Miscanthus growth during their establishment periods in the Soil and Water Assessment Tool (SWAT) model was improved. Finally, the model was used to evaluate the impacts on hydrologic and water quality processes due to production of switchgrass and Miscanthus on marginal lands in the UMRB region. The results indicated that 23% of the UMRB area included marginal lands. Among these lands, 40% of them were poorly suitable for the production of biofeedstock crops. Biofeedstocks produced from these marginal lands could be converted to biofuels that contributed 14 to 25% of the 132 billion liter biofuel goals set by the Energy Independence and Security Act (EISA) 2007. The model simulation results indicated that producing perennial biofeedstock crops on marginal land would reduce annual stream flow by 20% and 29% and sediment load by 26% to 35% at the watershed outlet. The reduction was less during the establishment periods of perennial grasses (first 2 to 3 years of switchgrass and 2 to 4 years of Miscanthus) than during the post establishment periods. The results of this study indicated that marginal land in the UMRB region could be a viable choice of land resources for biofuel development and could be used to produce almost one quarter of biofuel production goals. At the same time, water quality in the watershed could be improved. The information could be used by stakeholders to create regional biofuel development and watershed management plans