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United States Department of Agriculture

Agricultural Research Service

Research Project: Mitigating Agricultural Sources of Particulate Matter and Greenhouse Gas Emissions in the Pacific Northwest

Location: Northwest Sustainable Agroecosystems Research

Title: Site-specific trade-offs of harvesting cereal residues as biofuel feedstocks

Authors
item Huggins, David
item Kruger, Chad -
item Painter, Kathleen -
item Uberuaga, David -

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2012
Publication Date: March 20, 2014
Citation: Huggins, D.R., Kruger, C.E., Painter, K.M., Uberuaga, D.P. 2014. Site-specific trade-offs of harvesting cereal residues as biofuel feedstocks. BioEnergy Research. DOI: 10.1007/s12155-014-9438-4.

Interpretive Summary: Straw produced by wheat and barley crops is considered an important feedstock for future biofuel production. Harvesting straw, however, could lead to soil erosion, loss of organic matter and impaired sustainability. Our objective was to evaluate trade-offs associated with harvesting straw including impacts on soil quality, soil organic matter (SOM) and nutrients removed in harvested straw. We discovered that substantial variation in straw production occurred within a given field indicating that straw harvest should be targeted towards field areas with greater straw. Harvesting straw reduced organic inputs to soil by 46% and to field levels that would not sustain SOM under conventional tillage (CT). Harvesting straw under CT was also predicted to reduce soil quality as Soil Conditioning Indices (SCI) were negative throughout the field. In contrast, SCI’s under no-tillage (NT) were positive throughout the field despite straw harvest. We found that significant amounts of crop nutrients are removed in harvested straw with a fertilizer replacement value of $14.59/Mg dry straw and that field variation in nutrients removed was tremendous ranging from $12.27 to $69.74/ha. We concluded that substantial trade-offs exist in harvesting straw for biofuel, that trade-offs should be evaluated on a site-specific field basis, and that support practices such as crop rotation, NT and site-specific nutrient management need to be considered if straw harvest is to be a sustainable option. These results will be useful for wheat growers, NRCS, Conservation Districts, scientists and the fertilizer industry as field assessment of straw harvest is critical for managing soil sustainability and in the formulation of site-specific recommendations for straw harvest and fertilizer applications.

Technical Abstract: Cereal residues are considered an important feedstock for future biofuel production. Harvesting cereal residues, however, could lead to substantial soil degradation. Our objective was to evaluate trade-offs associated with harvesting straw including impacts on soil erosion and quality, soil organic C (SOC) and nutrient removal. We used cropping systems data from 369 geo-referenced points on the 37-ha Washington State University Cook Agronomy Farm to develop straw harvest scenarios that included conventional tillage (CT) and no-tillage (NT) and both two- and three-year crop rotations. Site-specific field estimates of annual lingo-cellulosic ethanol production scenarios ranged from 681 to 1541 L/ha and indicated that both crop rotation and site-specific targeting of residue harvest are important factors. Harvesting straw reduced average residue C inputs by 46% and to field levels below that required to maintain SOC under CT. This occurred as a function of both straw harvest and the inclusion of low residue producing crops in rotation with cereals. Harvesting straw under CT was predicted to reduce soil quality as Soil Conditioning Indices (SCI) were negative throughout the field. In contrast, SCI’s under NT were positive throughout the field despite straw harvest. Estimated replacement value of nutrients (N, P, K, S) removed in harvested straw was $14.59/Mg dry straw with field variation that ranged from $12.27 to $69.74/ha for the continuous cereal rotation. We concluded that substantial trade-offs exist in harvesting straw for biofuel, that trade-offs should be evaluated on a site-specific basis, and that support practices such as crop rotation, reduced tillage and site-specific nutrient management need to be considered if straw harvest is to be a sustainable option.

Last Modified: 10/22/2014
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