Crop and Soil Productivity Response to Corn Residue Removal: A Literature Review

of greenhouse gases in the atmosphere (IPCC, 2001), and ability of our agricultural systems to sustain producSociety is facing three related issues: overreliance on imported fuel, tion at rates needed to feed a growing world population increasing levels of greenhouse gases in the atmosphere, and producing sufficient food for a growing world population. The U.S. De(Cassman, 1999). Many papers have been written on partment of Energy and private enterprise are developing technology these topics both individually and in the various combinecessary to use high-cellulose feedstock, such as crop residues, for nations (Doran, 2002; Follett, 2001; Janzen et al., 1998a, ethanol production. Corn (Zea mays L.) residue can provide about 1998b; Lal et al., 1999). However, few authors have ad1.7 times more C than barley (Hordeum vulgare L.), oat (Avena sativa dressed all three topics together. L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max Recent developments in the energy industry and ac(L.) Merr.], sunflower (Helianthus annuus L.), and wheat (Triticum tivity by entrepreneurs have prompted new strategies aestivum L.) residues based on production levels. Removal of crop for addressing the first issue, overreliance on imported residue from the field must be balanced against impacting the environfuels (Hettenhaus et al., 2000). This strategy expands use ment (soil erosion), maintaining soil organic matter levels, and preof biomass for fuel production and is contingent on deserving or enhancing productivity. Our objective is to summarize published works for potential impacts of wide-scale, corn stover collection velopment of new organisms or enzymes to convert on corn production capacity in Corn Belt soils. We address the issue of cellulosic (a high concentration of cellulose) biomass crop yield (sustainability) and related soil processes directly. However, [opposed to grain (starchy) biomass] to ethanol for use scarcity of data requires us to deal with the issue of greenhouse gases as a motor vehicle fuel. The U.S. DOE, in concert with indirectly and by inference. All ramifications of new management pracprivate enterprise, is making great strides toward develtices and crop uses must be explored and evaluated fully before an oping enzymes and improving efficiency in fuel producindustry is established. Our conclusion is that within limits, corn stover tion from biomass (DiPardo, 2000; Hettenhaus et al., can be harvested for ethanol production to provide a renewable, do2000). mestic source of energy that reduces greenhouse gases. RecommendaSources of cellulosic biomass are numerous (woody biotion for removal rates will vary based on regional yield, climatic mass crops and lumber industry wastes, forage crops, inconditions, and cultural practices. Agronomists are challenged to develop a procedure (tool) for recommending maximum permissible dustrial and municipal wastes, animal manure, and crop removal rates that ensure sustained soil productivity. residues); however, currently few sources are perceived to be available in sufficient quantity and quality to support development of an economically sized processing facility of about 1800 Mg dry matter d 1 (Hettenhaus T of the most pressing issues facing our society, et al., 2000), except crop residues (DiPardo, 2000). Bain the midterm, are overreliance on imported fuels gasse [remaining after sap extraction from sugarcane [U.S. Department of Energy (DOE) Office of Energy Ef(Saccharum officinarum L.)] in Louisiana and rice (Orficiency and Renewable Energy, 2002], increasing levels yza sativa L.) straw in California are regional examples of crop residues collected in current culture and availW.W. Wilhelm, USDA-ARS, 120 Keim Hall, Univ. of Nebraska, Linable for production of ethanol (DiPardo, 2000). Creatcoln, NE 68583-0934;  J.L. Hatfield, 108 Natl. Soil Tilth Lab., 2150 residues represents a huge problem in the regions where Pammel Drive, Ames, IA 50011-3120; W.B. Voorhees, USDA-ARS (retired), 803 Iowa Ave., Morris, MN 56267-1065; and D.R. Linden, they are produced although the total quantity is not USDA-ARS (retired), 1991 Upper Buford Circle, St. Paul, MN 55108sufficient to have a great impact on fuel needs for the 0000. This paper is a joint contribution of the USDA-ARS and the nation (DiPardo, 2000). On the other hand, the quantity Agricultural Research Division of the University of Nebraska. Pubof corn stover is large, but corn stover is generally not lished as Journal Ser.  Corresponding author (wwilhelm1@unl.edu).  13C, change in 13C atom percent; DOE, Department Published in Agron.  (2004).  American Society of Agronomy of Energy; HI, harvest index; SOC, soil organic carbon; SOM, soil organic matter. 677 S. Segoe Rd., Madison, WI 53711 USA