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Benefits and barriers to perennial forage crops in Iowa corn and soybean rotations

Published online by Cambridge University Press:  27 May 2008

Julia Olmstead  and
E. Charles Brummer
Julia Olmstead*
Affiliation:
Graduate Program in Sustainable Agriculture, Department of Agronomy, Iowa State University, Ames, IA 50011, USA.
E. Charles Brummer
Affiliation:
Center for Applied Genetic Technologies, Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA.
*
*Corresponding author: [email protected]
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Abstract

The transition away from forage-based cropping systems in Iowa to corn and soybean rotations since World War II has corresponded with degraded economic and environmental conditions in the state. Falling net incomes for farmers and concern over global warming and the effects of agriculture-related pollution on water, wildlife and human health have increased interest in diversified cropping systems. This paper reviews the benefits of diversifying Iowa corn and soybean rotations with perennial forage species such as alfalfa and red clover. Perennial forage crops improve soil quality, decrease NO3-N leaching and soil erosion, increase carbon sequestration and decrease pesticide and herbicide needs by controlling weed and insect pests. Forage legumes reduce N fertilizer needs for succeeding corn crops at a higher rate than soybeans, and corn crops following forages have higher yields than after corn or soybeans. Farmers who add alfalfa to corn and soybean rotations could realize significant economic gains. A simulated 5-year rotation in Iowa including corn–soybeans–oats/alfalfa–alfalfa–alfalfa would result in a 24% net income increase over 5 years of corn–soybean–corn–soybean–corn, even with government farm support payments for the row crops. Farm policies that encourage commodity production create little incentive for Iowa farmers to diversify their cropping systems beyond corn and soybeans, despite the clear economic and ecological benefits. We recommend increasing federal support for conservation programs that reward environmentally beneficial farm practices such as the Conservation Securities Program and we encourage land grant universities to hire researchers interested in alternative agricultural systems.

Keywords

foragesalfalfacorncropping systemsalternative agriculturefarm policy
Type
Review Article
Information
Renewable Agriculture and Food Systems , Volume 23 , Issue 2 , June 2008 , pp. 97 - 107
Copyright
Copyright © 2008 Cambridge University Press

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References

1 Dimitri, C., Effland, A., and Conklin, N. 2005. The 20th century transformation of U.S. agriculture and farm policy. Economic Research Bulletin. Economic Research Service, United States Department of Agriculture.Google Scholar
2 Cardwell, V.B. 1982. Fifty years of Minnesota corn production: sources of yield increase. Agronomy Journal 74:984–990.CrossRefGoogle Scholar
3 United States Department of Agriculture, National Agricultural Statistics Service (USDA-NASS). 2007. Crops and Plants Quick Stats. Available at Web site: http://www.nass.usda.gov/QuickStats/indexbysubject.jsp?Text1=&site=NASS_MAIN&select=Select+a+State&Pass_name=&Pass_group-Crops+%26+Plants&Pass_subgroup=Field+Crops (verified 9 April 2007).Google Scholar
4 United States Department of Agriculture, National Agricultural Statistics Services (USDA-NASS). 2006. Economics Quick Stats. Available at Web site: http://www.nass.usda.gov/QuickStats/indexbysubject.jsp?Pass_group=Economics (verified 16 February 2006).Google Scholar
5 Gast, R.G., Nelson, W.W., and MacGregor, J.M. 1978. Nitrate accumulation in soils and loss in tile drainage following nitrogen application to continuous corn. Journal of Environmental Quality 7:258–262.CrossRefGoogle Scholar
6 Logan, T.J., Randall, G.W., and Timmons, D.R. 1980. Nutrient content of tile drainage from cropland in the North Central Region. North Central Regional Research Publication 268. OARDC Research Bulletin 1119. The Ohio State University, Columbus, OH.Google Scholar
7 Logan, T.J., Eckert, D.J., and Beak, D.G. 1993. Tillage, crop and climate effects on runoff and tile drainage losses of nitrate and four herbicides. Soil Tillage Research 30:75–103.CrossRefGoogle Scholar
8 Kladivko, E.J., Van Scoyoc, G.E., Monke, E.J., Oates, K.M., and Pask, W. 1991. Pesticide and nutrient movement into subsurface tile drains on a silt loam in Indiana. Journal of Environmental Quality 20:264–270.CrossRefGoogle Scholar
9 Buhler, D.D., Randall, G.W., Koskinen, W.C., and Wyse, W.L. 1993. Atrazine and alachlor losses from subsurface tile drainage of a clay loam soil. Journal of Environmental Quality 22:583–588.CrossRefGoogle Scholar
10 Cambardella, C.A., Moorman, T.B., Jaynes, D.B., Hatfield, J.L., Parkin, T.B., Simpkins, W.W., and Karlen, D.L. 1999. Water quality in Walnut Creek watershed: nitrate-nitrogen in soils, subsurface drainage water, and shallow groundwater. Journal of Environmental Quality 28:25–34.CrossRefGoogle Scholar
11 Hatfield, J.L., Jaynes, D.B., Burkart, M.R., Cambardella, C.A., Moorman, T.B., Prueger, J.H., and Smith, M.A. 1999. Farming systems impacts on water quality in Walnut Creek Watershed. Journal of Environmental Quality 28:11–24.CrossRefGoogle Scholar
12 Jaynes, D.B., Hatfield, J.L., and Meek, D.W. 1999. Water quality in Walnut Creek watershed: herbicides and nitrate in surface waters. Journal of Environmental Quality 28:45–59.CrossRefGoogle Scholar
13 Kanwar, R.S., Bjorneberg, D.L., and Baker, D. 1999. An automated system for monitoring the quality and quantity of subsurface drain flow. Journal of Agricultural Engineering Research 73:123–129.CrossRefGoogle Scholar
14 Rabalais, N.N., Turner, R.E., Justic, D., Dortch, Q., and Wiseman, W.J. 1999. Characterization of hypoxia: Topic 1. Report for the integrated assessment on hypoxia in the Gulf of Mexico. NOAA Coastal Ocean Program Decision Analysis Series No. 15. NOAA Coastal Ocean Program, Silver Spring, MD.Google Scholar
15 Relyea, R. 2005. The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities. Ecological Applications 15:618–627.CrossRefGoogle Scholar
16 Richard, S., Moslemi, S., Sipahutar, H., Benachour, N., and Seralini, G. 2005. Differential effects of glyphosate and Roundup on human placental cells and aromatase. Environmental Health Perspectives 113:716–720.CrossRefGoogle ScholarPubMed
17 Rohr, J.R. and Crumrine, P.W. 2005. Effect of an herbicide and an insecticide on pond community structure and processes. Ecological Applications 15:1135–1147.CrossRefGoogle Scholar
18 Forage Grazing Terminology Committee. 1992. Terminology for grazing lands and grazing animals. Journal of Production Agriculture 5:191–201.Google Scholar
19 Barnhart, S. 2006. Iowa State University Forage Extension Specialist. (Personal communication.)Google Scholar
20 Iowa Department of Agriculture. 2005. Iowa Agricultural Statistics Bulletin. Available at Web site: http://www.agriculture.state.ia.us/2005AgStatsGeneralInfo.htm (verified 12 November 2006).Google Scholar
21 Pimentel, D. and Pimentel, M. 1996. Food, Energy and Society. University Press of Colorado, Niwot, CO.Google Scholar
22 Crookston, R.K., Kurle, J.E., Copeland, P.J., Ford, J.H., and Lueschen, W.E. 1991. Rotational cropping sequence affects yield of corn and soybean. Agronomy Journal 83:108–113.CrossRefGoogle Scholar
23 Porter, P.M., Crookston, R.K., Ford, J.H., Huggins, D.R., and Lueschen, W.E. 1997. Interrupting yield depression in monoculture corn: comparative effectiveness of grasses and dicots. Agronomy Journal 89:247–250.CrossRefGoogle Scholar
24 Pikul, J.L.J., Hammack, L., and Riedell, W.E. 2005. Corn yield, nitrogen use, and corn rootworm infestation of rotations in the northern corn belt. Agronomy Journal 97:854–863.CrossRefGoogle Scholar
25 Bolton, E.F., Dirks, V.A., and Aylesworth, J.W. 1976. Some effects of alfalfa, fertilizer and lime on corn yield in rotation on clay soil during a range of seasonal moisture conditions. Canadian Journal of Soil Science 56:21–25.CrossRefGoogle Scholar
26 Gregory, M.M., Shea, K.L., and Bakko, E.B. 2005. Comparing agroecosystems: effects of cropping and tillage patterns on soil, water, energy use and productivity. Renewable Agriculture and Food Systems 20:81–90.CrossRefGoogle Scholar
27 Hesterman, O.B., Schaeffer, C.C., Barnes, D.K., Lueschen, W.E., and Ford, J.H. 1986. Alfalfa dry matter and nitrogen production, and fertilizer nitrogen response in legume–corn rotations. Agronomy Journal 78:19–23.CrossRefGoogle Scholar
28 Clay, S.A. and Aguilar, I. 1998. Weed seedbanks and corn growth following continuous corn or alfalfa. Agronomy Journal 90:813–818.CrossRefGoogle Scholar
29 Fox, R.H. and Piekielek, W.P. 1988. Fertilizer N equivalance of alfalfa, birdsfoot trefoil, and red clover for succeeding corn crops. Journal of Production Agriculture 1:313–317.CrossRefGoogle Scholar
30 Ma, B.L., Ying, J., Dwyer, L.M., Gregorich, E.G., and Morrison, M.J. 2003. Crop rotation and soil N amendment effects on maize production in eastern Canada. Canadian Journal of Soil Science 83:483–495.CrossRefGoogle Scholar
31 Uhland, R.E. 1948. Grass and the yields of cash crops. In Grass. Yearbook of Agriculture 1948. United States Department of Agriculture, Washington, DC. p. 191–194.Google Scholar
32 Adams, W.E., Morris, H.D., and Dawson, R.N. 1970. Effects of cropping systems and nitrogen levels on corn (Zea mays) yields in the southern Piedmont region. Agronomy Journal 62:655–659.CrossRefGoogle Scholar
33 Huggins, D.R., Randall, G.W., and Russelle, M.P. 2001. Subsurface drain losses of water and nitrate following conversion of perennials to row crops. Agronomy Journal 93:477–486.CrossRefGoogle Scholar
34 Anderson, I.C., Buxton, D.R., Karlen, D.L., and Cambardella, C.A. 1997. Cropping system effects on nitrogen removal, soil nitrogen, aggregate stability and subsequent corn grain yield. Agronomy Journal 89:881–886.CrossRefGoogle Scholar
35 Hesterman, O.B., Griffin, T., Williams, P., Harris, G., and Christenson, D. 1992. Forage-legume small-grain intercrops: nitrogen production and response of subsequent corn. Journal of Production Agriculture 5:340–348.CrossRefGoogle Scholar
36 United States Department of Agriculture. 2005. Agricultural Chemical Usage: 2005 Field Crop Summary. Available at Web site: http://usda.mannlib.cornell.edu/reports/nassr/other/pcu-bb/agcs0506.pdf (verified 31 May 2006).Google Scholar
37 Battaglin, W.A., Kolpin, D.W., Scribner, E.A., Kuivila, K.M., and Sandstrom, M.W. 2005. Glyphosate, other herbicides, and transformation products in Midwestern streams. Journal of American Water Resources Association 41:323–332.CrossRefGoogle Scholar
38 Cerdeira, A.L. and Duke, S.O. 2006. The current status and environmental impacts of glyphosate-resistant crops. Journal of Environmental Quality 35:1633–1658.CrossRefGoogle ScholarPubMed
39 Michael, P.W. 1960. The control of thistles (Silybum and Onopordum) by perennial pasture species. Proceedings of the Australian Weed Conference, 2nd Council of the Australian Weed Science Society, Meredith, VIC, Australia.Google Scholar
40 Derscheid, L.A. 1978. Controlling field bindweed while growing adapted crops. Proceedings of the North Central Weed Control Conference 33:144–150. North Central Weed Science Society.Google Scholar
41 Pearson, J.O. 1969. A life history study of white cockle (Lynchis alba Mill.) and some competitive effects in alfalfa (Medicago sativa L.). PhD thesis, Michigan State University, East Lansing, MI.Google Scholar
42 Ahmed, M. 1988. Viability of buried seeds of bathua (Chenopodium album L.). Bangladesh Journal of Agriculture 13:23–30.Google Scholar
43 Brink, G.E. and Marten, G.C. 1986. Barley vs. oat companion crops: II. Influence on alfalfa persistence and yield. Crop Science 26:1067–1071.CrossRefGoogle Scholar
44 Sheaffer, C.C. 1983. Seeding year harvest management of alfalfa. Agronomy Journal 75:115–119.CrossRefGoogle Scholar
45 Curran, B.S., Kephardt, K.D., and Twidwell, E.K. 1993. Oat companion crop management in alfalfa establishment. Agronomy Journal 85:998–1003.CrossRefGoogle Scholar
46 Caporali, F. and Onnis, A. 1992. Validity of rotation as an effective agroecological principle for a sustainable agriculture. Agriculture, Ecosystems and Environment 41:101–113.CrossRefGoogle Scholar
47 Westerman, P.R., Liebman, M., Menalled, F.D., Heggenstaller, A.H., Hartzler, R.G., and Dixon, P.M. 2005. Are many little hammers effective? Velvetleaf (Abutilon theophrasti) population dynamics in two- and four-year crop rotation systems. Weed Science 53:382–392.CrossRefGoogle Scholar
48 Heggenstaller, A.H. and Liebman, M. 2006. Demography of Abutilon theophrasti and Setaria faberi in three crop rotation systems. Weed Research 46:138–151.CrossRefGoogle Scholar
49 Francis, C.A., Flora, C.B., and King, L.D. 1990. Sustainable Agriculture in Temperate Zones. Wiley, Hoboken, NJ.Google Scholar
50 Stickler, F.C. and Johnson, I.J. 1959. Dry matter and nitrogen production of legumes and legume associations in the fall of the seeding year. Agronomy Journal 51:135–137.CrossRefGoogle Scholar
51 Putnam, D., Russelle, M.P., Orloff, S., Kuhn, J., Fitzhugh, L., Godfrey, L., Kiess, A., and Long, R. 2001. Alfalfa, Wildlife and the Environment. California Alfalfa and Forage Association, Novato, CA. Available at Web site: http://www.calhay.org/environmental.html (verified 3 January 2007).Google Scholar
52 Carpenter-Boggs, L., Pikul, J.L.J., Vigil, M.F., and Riedell, W.E. 2000. Soil nitrogen mineralization influenced by crop rotation and nitrogen fertilization. Soil Science Society of America Journal 64:2038–2045.CrossRefGoogle Scholar
53 Sawyer, J.E. 2001. Making Every Fertilizer Dollar Pay. Integrated Crop Management IC-486, 29 January 2001. Available at Web site: http://www.ipm.iastate.edu/ipm/icm/2001/1-29-2001/makenpay.html (verified 22 March 2006).Google Scholar
54 Lamond, R.E., Whitney, D.A., Bonczkowski, L.C., and Hickman, J.S. 1988. Using legumes in crop rotations. Cooperative Extension Service Bulletin L778. Kansas State University, Manhattan, KS.Google Scholar
55 Kanwar, R.S., Cruse, R.M., Ghaffarzadeh, M., Bakhsh, A., Karlen, D.L., and Bailey, T.B. 2005. Corn–soybean and alternative cropping systems effects on NO3-N leaching losses in subsurface drainage water. Applied Engineering in Agriculture 21:181–188.CrossRefGoogle Scholar
56 Randall, G.W., Huggins, D.R., Russelle, M.P., Fuchs, D.J., Nelson, W.W., and Anderson, J.L. 1997. Nitrate losses through subsurface tile drainage in Conservation Reserve Program, alfalfa and row crop systems. Journal of Environmental Quality 26:1240–1247.CrossRefGoogle Scholar
57 Perfect, E., Kay, B.D., van Loon, W.K.P., Sheard, R.W., and Pojasok, T. 1990. Rates of change in soil structural ability under forages and corn. Soil Science Society of America Journal 54:179–186.CrossRefGoogle Scholar
58 Reid, J.B. and Goss, M.J. 1981. Effects of living roots of different plant species on aggregate stability of two arable soils. Journal of Soil Science 32:521–541.CrossRefGoogle Scholar
59 Su, Y.Z. 2007. Soil carbon and nitrogen sequestration following the conversion of cropland to alfalfa forage land in northwest China. Soil and Tillage Research 92:181–189.CrossRefGoogle Scholar
60 Drury, C.F., Yang, X.M., Reynolds, W.D., and Tan, C.S. 2004. Influence of crop rotation and aggregate size on carbon dioxide production and denitrification. Soil and Tillage Research 79:87–100.CrossRefGoogle Scholar
61 Senwo, Z.N. and Tabatabai, M.A. 2005. Aspartase activity of soils under different management systems. Communications in Soil Science and Plant Analysis 36:2575–2585.CrossRefGoogle Scholar
62 Dodor, D.E. and Tabatabai, M.A. 2005. Glycosidases in soils as affected by cropping systems. Journal of Plant Nutrition and Soil Science 168:749–758.CrossRefGoogle Scholar
63 Ekenler, M. and Tabatabai, M.A. 2002. β-Glucosaminidase activity of soils: effect of cropping systems and its relationship to nitrogen mineralization. Biology and Fertility of Soils 36:367–376.CrossRefGoogle Scholar
64 Moore, J.M., Klose, S., and Tabatabai, M.A. 2000. Soil microbial biomass carbon and nitrogen as affected by cropping systems. Biology and Fertility of Soils 31:200–210.CrossRefGoogle Scholar
65 Karlen, D.L., Hurley, E.G., Andrews, S.S., Cambardella, C.A., Meeka, D.W., Duffy, M.D., and Mallarino, A.P. 2006. Crop rotation effects on soil quality at three northern corn/soybean belt locations. Agronomy Journal 98:484–495.CrossRefGoogle Scholar
66 Russell, A.E., Laird, D.A., and Mallarino, A.P. 2006. Nitrogen fertilization and cropping system impacts on soil quality in midwestern mollisols. Soil Science Society of America Journal 70:249–255.CrossRefGoogle Scholar
67 Putnam, D. 1998. Contributions of alfalfa to wildlife and the environment. Proceedings of the 28th National Alfalfa Symposium, Bowling Green, KY.Google Scholar
68 Angers, D.A. 1992. Changes in soil aggregation and organic carbon under corn and alfalfa. Soil Science Society of America Journal 56:1244–1249.CrossRefGoogle Scholar
69 Clark, E.H.I., Haverkamp, J.A., and Chapman, W. 1985. Eroding Soils: The Off-farm Impacts. The Conservation Foundation, Washington, DC.Google Scholar
70 United States Environmental Protection Agency. 2006. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2004. United States Environmental Protection Agency, Washington, DC.Google Scholar
71 Deng, S.P. and Tabatabai, M.A. 2000. Effects of cropping systems on nitrogen mineralization in soils. Biology and Fertility of Soils 31:211–218.CrossRefGoogle Scholar
72 Gebhardt, D.L., Johnson, H.B., Mayeux, H.S., and Polley, H.W. 1994. The CRP increases soil organic carbon. Journal of Soil and Water Conservation 49:488–492.Google Scholar
73 Russell, A.E., Laird, D.A., Parkin, T.B., and Mallarino, A.P. 2005. Impact of nitrogen fertilization and cropping system on carbon sequestration in midwestern mollisols. Soil Science Society of America Journal 69:413–422.CrossRefGoogle Scholar
74 Gregorich, E.G., Drury, C.F., and Baldock, J.A. 2001. Changes in soil carbon under long-term maize in monoculture and legume-based rotation. Canadian Journal of Soil Science 81:21–31.CrossRefGoogle Scholar
75 Dodor, D.E. and Tabatabai, M.A. 2003. Effect of cropping systems on phosphatases in soils. Journal of Plant Nutrition and Soil Science 166:7–13.CrossRefGoogle Scholar
76 Robinson, C.A., Cruse, R.M., and Ghaffarzadeh, M. 1996. Cropping system and nitrogen effects on mollisol organic carbon. Soil Science Society of America Journal 60:264–269.CrossRefGoogle Scholar
77 Meyer-Aurich, A., Weersink, A., Janovicek, K., and Deen, B. 2006. Cost efficient rotation and tillage options to sequester carbon and mitigate GHG emissions from agriculture in Eastern Canada. Agriculture, Ecosystems and Environment 117:119–127.CrossRefGoogle Scholar
78 Thompson, R.L. and Thompson, S.M. 2004. Alternatives in Agriculture. Thompson On-farm Research, Boone, IA.Google Scholar
79 Diebel, P.L., Williams, J.R., and Llewelyn, R.V. 1995. An economic comparison of conventional and alternative cropping systems for a representative northeast Kansas farm. Review of Agricultural Economics 17:323–335.CrossRefGoogle Scholar
80 Sheaffer, C.C., Barnes, D.K., and Heichel, G.H. 1989. ‘Annual’ alfalfa in crop rotations. Minnesota Agricultural Experiment Station Bulletin 588. University of Minnesota, St. Paul, MN.Google Scholar
81 Delate, K., Duffy, M., Chase, C., Holste, A., Friedrich, H., and Wantate, N. 2003. An economic comparison of organic and conventional grain crops in a long-term agroecological research (LTAR) site in Iowa. American Journal of Alternative Agriculture 18:59–69.CrossRefGoogle Scholar
82 Mitchell, R., Vogel, K., Varvel, G., Klopfenstein, T., Clark, D., and Anderson, B. 2005. Big bluestem pasture in the Great Plains: an alternative for dryland corn. Rangelands 27:31–35.CrossRefGoogle Scholar
83 Nimrick, K., Oswald, D., and Staff, R. 2005. Economics of grazing stocker cattle as a sustainable alternative to row crops. Proceedings of the American Forage and Grasslands Council, Bloomington, IL.Google Scholar
84 Rotz, A.C., Roth, G.W., Soder, K.J., and Schnabel, R.R. 2001. Economic and environmental implications of soybean production and use on Pennsylvania dairy farms. Agronomy Journal 93:418–428.CrossRefGoogle Scholar
85 Duffy, M. and Smith, D. 2004. Farmland ownership and tenure in Iowa 1982–2002: a twenty-year perspective. Iowa State University Extension Publication PM 1983. Iowa State University, Ames, IA.Google Scholar
86 Duffy, M. and Smith, D. 2005. Estimated crop production costs in Iowa. Extension Bulletin FM1712. Iowa State University, Ames, IA.Google Scholar
87 Hay, and Forage, Grower. 2003. Prices are Largely Unchanged. Available at Web site: http://hayandforage.com/mag/farming_prices_largely_unchanged/index.html (verified 15 April 2006).Google Scholar
88 Wisner, B. 2003. Counter-cyclical payments for corn and soybeans. Ag Decision Maker Newletter 9(1). Iowa State University Extension, Iowa State University, Ames, IA. Available at Web site: http://www.extension.iastate.edu/AgDM/articles/wisner/WisFeb03.html (verified 3 January 2006).Google Scholar
89 Lozier, J., Rayburn, E., and Shaw, J. 2005. Growing and selling pasture-finished beef: results of a nationwide survey. Journal of Sustainable Agriculture 25:93–112.CrossRefGoogle Scholar
90 Naylor, R., Steinfeld, H., Falcon, E., Galloway, J., Smil, V., Bradford, E., Alder, J., and Mooney, H. 2005. Losing the links between livestock and land. Science 310:1621–1622.CrossRefGoogle ScholarPubMed
91 Dougherty, E. and Geuder, J. 2007. Corn Acres Expected to Soar in 2007, USDA Says. USDA National Agricultural Statistics Service Newsroom. Available at Web site: http://www.nass.usda.gov/Newsroom/2007/03_30_2007.asp (verified 9 April 2007).Google Scholar
92 Environmental Working Group. 2006. Farm Subsidy Database. Available at Web site: http://www.ewg.org/farm/ (verified 18 May 2006).Google Scholar
93 Hanson, M., Miller, R., and Padgitt, S. 2002. Incorporating Grassland Agriculture into Row Crop Systems. Iowa State University Extension, Iowa State University, Ames, IA.Google Scholar
94 Shoemaker, R., McGranahan, D., and McBride, W. 2006. Agriculture and rural communities are resilient to high energy costs. Amber Waves 4(2):16–21.Google Scholar
95 Marshall, L. and Greenhalgh, S. 2006. Beyond the RFS: The Environmental and Economic Impacts of Increased Grain Ethanol Production in the U.S. World Resources Institute, Washington, DC.Google Scholar
96 Boody, G., Vondracek, B., Andow, D.A., Krinke, M., Westra, J., Zimmerman, J., and Welle, P. 2005. Multifunctional agriculture in the United States. Bioscience 55:27–38.CrossRefGoogle Scholar
97 Trout, S.K., Francis, C.A., and Barbuto, J.E. 2005. Evaluation and perceived impacts of the North-Central Region SARE grants, 1998–2002. Journal of Sustainable Agriculture 27(2):117–137.CrossRefGoogle Scholar
98 Keeney, D. and Kemp, L. 2004. How to Make it Work: Required Policy Transformations for Agroecosystem Restoration. Institute for Agriculture and Trade Policy, Minneapolis, MN. Available at Web site: http://www.mcknight.org/hotissues/news/makeitwork_kemp-keeney.pdf (verified 8 January 2007).Google Scholar
99 Traxler, G., Acquaye, A.K.A., Frey, K., and Thro, A.M. 2005. Public Sector Plant Breeding Resources in the US: Study Results for the Year 2001. Cooperative State Research, Education, and Extension Service, United States Department of Agriculture. Available at Web site: http://www.csrees.usda.gov/nea/plants/part/pbgg_part_study.html (verified 18 April 2007).Google Scholar