Cover Crop Selection and Use in Organic No-Till Farming

Project Overview

Project Type: Research and Education
Funds awarded in 2009: $155,730.00
Projected End Date: 12/31/2013
Region: North Central
State: North Dakota
Project Coordinator:
Dr. Patrick Carr
Montana State University

Annual Reports

Information Products


  • Agronomic: corn, flax, rye, soybeans, wheat


  • Crop Production: conservation tillage
  • Education and Training: demonstration, extension, on-farm/ranch research, participatory research
  • Energy: energy use
  • Farm Business Management: budgets/cost and returns
  • Natural Resources/Environment: carbon sequestration
  • Pest Management: allelopathy, cultural control, row covers (for pests), smother crops, mulching - vegetative, weed ecology
  • Production Systems: organic agriculture
  • Soil Management: green manures, organic matter, soil microbiology, soil quality/health


    Anticipated soil quality and other benefits have generated interest in adoption of no-till practices on organic farms. Vegetative mulch provided by killed cover crops is relied on heavily for weed suppression in no-till organic systems. This project included one study where 12 different cover crop treatments were screened for potential use in no-till organic systems at locations in IA, MN, ND, and WI, with up to 10 different treatments evaluated at any one location. Different methods of terminating cover crops were compared with a no-till method (rolling-crimping) common to all locations. A separate field study compared performance of up to five different market crops when seeded directly into rolled-crimped cover crop mulch at three locations. Fall-seeded small-grain crops produced over 14,000 kg/ha (12,500 lb/ac) in WI and hairy vetch over 8000 kg/ha (7140 lb/ac) in ND of rolled-crimped vegetative mulch and have the greatest near-term potential as cover crops in no-till organic farming systems. Grain production was successful when soybean was seeded directly into cover crop mulch, but problems were encountered when corn and other grain crops were grown. Refinement of the rolling-crimping method for killing cover crops, screening of additional cover crop species, and modification of current no-till organic farming strategies are needed so that crops in addition to soybean can be grown using no-till organic practices in the north central region.


    Most organic farmers rely on cultivation to control weeds, but tillage can destroy soil structure, reduce organic matter content, and diminish overall sustainability of cropping systems. Karlen et al. (1994) found that soil aggregate stability, total carbon, microbial activity, and earthworm populations were enhanced after eliminating tillage over a 12-year period in a continuous corn system. Those researchers concluded that soil quality could be improved by replacing tilled with no-till cropping systems. Similarly, Tanaka et al. (2002) and others (Carr et al., 2006, 2008) reported that crop performance was improved by eliminating tillage in semiarid portions of the north central region, probably because plant water-use efficiency was enhanced. Trewavas (2004) speculated that conventional no-till farming was superior to organic farming for enhancing soil health because of the deleterious effects of tillage on soils. Robertson et al. (2000) warned that organic farming and other food production systems relying on tillage contributed more in greenhouse gas emissions than conventional no-till systems. Organic farming has been suggested as promoting poor soil stewardship because of the perception that intensive tillage practices are needed for weed control and contribute to excessive erosion and overall soil degradation (Kuepper, 2001). However, recent studies indicate that soil quality can be improved by organic farming practices compared with conventional, no-till farming methods, even though tillage is used in the organic systems. Soil combustible C and N were higher after nine years in an organic system that included cover crops compared with three conventional, no-till systems, two of which included cover crops (Teasdale et al., 2007). However, weed populations reportedly were unacceptable in the organic system by the end of the study. Similarly, Miller et al. (2008) indicated that potentially mineralizable N was greater in an organic system than conventional, no-till cropping systems in a 4-year study. Winter wheat grain yields were equal or greater in the organic system compared with the conventional no-till systems. However, weeds were a serious problem in the organic system after only four years. Developing no-till, organic farming methods would eliminate the detrimental impacts of tillage on soil health. For that reason, many organic farmers want reduced- and no-till farming systems to be developed (Sooby et al., 2007). However, eliminating tillage removes a major weed control practice on many organic farms. The challenge of how to control weeds without tillage on U.S. organic farms was considered by Creamer et al. (1995) in a comparison between no-till (i.e. flail and sickle bar mowing) and reduced-till (i.e., undercutting followed by rolling) methods for terminating cover crops in Ohio. Creamer also evaluated different cover crop termination methods that relied on little if any tillage in the southeastern U.S., and published results demonstrating that cover crops could be killed mechanically without tillage (Creamer and Dabney, 2002). Creamer and Dabney (2002) concluded that rolling with a stalk chopper was not always effective in killing cover crops unless delayed until plants reached seed development growth stages. Conversely, mowing generally was effective at killing broadleaf cover crops (e.g., cowpea), even at vegetative growth stages in some instances. The scientists encouraged others to continue exploring methods to seed directly into rolled cover crops as a way to incorporate no-till methods into systems that cannot rely on synthetic herbicides (e.g., certified organic systems). Research cited by Morse (1999) demonstrated that cover crops could be killed by mowing and rolling prior to transplanting broccoli. Implements used to roll the cover crops ranged from empty grain drills to rollers with attached blades designed specifically for that purpose. Morse (1999) cautioned readers that mowing and rolling were effective termination methods only when delayed until cover crops were flowering and, in several instances, even at more advanced growth stages. Similar conclusions regarding the importance of delaying rolling until plants reached reproductive growth stages were made by Creamer and Dabney (2002). Cover crops have been killed using rollers with blunt steel blades welded onto cylindrical drums in conservation tillage systems for many years in South America (Ashford and Reeves, 2003). The blades crimp or crush but do not cut plant stems, thereby improving efficacy of the termination method while also maintaining intact plant residue on the soil surface. Winter oat, rye, and wheat cover crops were killed with a roller-crimper as effectively as with herbicides when rolling and crimping were delayed until small-grain plants reached the early milk growth stage of kernel development in a 2-year study in Alabama (Ashford and Reeves, 2003). Rolling and crimping were ineffective at killing small-grain plants during vegetative growth stages in that same study. Southern U.S. scientists have been exploring roller-crimper prototypes that improve upon older designs (Kornecki et al., 2006). Similarly, scientists at The Rodale Institute in Kutztown, Pennsylvania, developed an improved roller-crimper design in collaboration with a local farmer and manufacturer (J. Moyer, 2011). The innovative design maximizes tractor driver comfort without compromising cover crop killing efficacy when the roller-crimper is operated in the field. The roller-crimper developed by The Rodale Institute scientists has chevron-shaped blades welded onto a drum that can be filled with water for added weight. A particular innovation is the ability to mount the unit on the front of the tractor so that cover crop termination and no-till seeding of the subsequent crop can occur in a single pass. Previous SARE Projects and Other Funded Research SARE has funded numerous projects promoting reduced- and no-till farming methods. Several projects have focused specifically on conservation tillage practices in systems managed organically. Several projects included no-till treatments. These projects ranged from farmer/rancher grants (e.g., Project FS08-231), to graduate student grants (e.g., Project GS07-058) and research and education grants (e.g., Project LNE08-268). Professional development program grants promoting no-till organic farming also have been awarded (e.g., Project ES06-085). Funding no-till organic research has not been limited to SARE; the Organic Farming Research Foundation has funded several projects directed specifically at developing no-till organic systems, and virtually all of these include a cover crops component. Past research on no-till organic farming is noteworthy and has increased our knowledge base. However, the current project differed from previous efforts in several important ways. First, several past studies focused on horticultural crops (e.g., pumpkin; SARE Project LNC07-276) which are of local importance but not widely grown across the north central region. Second, some projects focused on widely grown field crops (e.g., soybean; SARE Project LNC04-240) but included only a few cover crop treatments and termination methods. Third, some projects were fairly broad in scope (SARE Project LNE06-244) but based recommendations on field activities in environments that differ markedly in climate, soils, cropping practices, and other factors from those existing in the north central region. References Ashford, D.L., and D.W. Reeves. 2003. Use of a mechanical roller-crimper as an alternative kill method for cover crops. American J. Alt. Agric. 18:37-45. Carr, P.M., R.D. Horsley, and G.B. Martin. 2008. Impact of tillage on field pea following spring wheat. Can. J. Plant Sci. (in press) Carr, P.M., Horsley, R.D. and Martin, G.B. 2006. Impact of tillage and crop rotation on grain yield of spring wheat I. Tillage effect. [Online] Available: http://www. pub/cm/research/2006/wheat1/ [verified 17 September 2008] Creamer, N.G., B. Plassman, M.A. Bennett, R.K. Wood, B.R. Stinner, and J. Cardina. 1995. A method for mechanically killing cover crops to optimize weed suppression. American J. Alt. Agric. 10:157-162. Creamer, N.G., and S.M. Dabney. 2002. Killing cover crops mechanically: Review of recent literature and assessment of new research results. American J. Alt. Agric. 17:32-40. Karlen, D.L., N.C. Wollenhaupt, D.C. Erbach, E.C. Berry, J.B. Swan, N.S. Eash, and J.L. Jordahl. 1994. Long-term tillage effects on soil quality. Soil and Tillage Res. 32:313-327. Kornecki, T.S., A.J. Price, and R.L. Raper. 2006. Performance of different roller designs in terminating rye cover crop and reducing vibration. Applied Eng. Agric. 22:633-641. Kuepper, G. 2001. Organic matters. Pursuing conservation tillage systems for organic crop production. National Center for Appropriate Technology, Butte MT. Available: [verified 09 October 2008] Miller, P.R., D.E. Buschena, C.A. Jones, and J.A. Holmes. 2008. Transition from intensive tillage to no-tillage and organic diversified annual cropping systems. Agron. J. 100:591-599. Morse, R.D. 1999. No-till vegetable production – its time is now. HortTech. 9:373-379. Moyer, J. 2011. Organic no-till farming. Advancing no-till–crops, Soils, Equipment; Acres USA: Austin, TX, USA, p. 204. Robertson, G.P., A. P. Eldor, and R.R. Harwood. 2000. Greenhouse gases in intensive agriculture: Contributions of individual gases to the radiative forcing of the atmosphere. Science 289:1922-1925. Sooby, J., J. Landeck, and M. Lipson. 2007. National Organic Research Agenda. Organic Farming Research Foundation, Santa Cruz, CA. 74 p. Tanaka, D. L., J. M. Krupinsky, M. A. Liebig, S. D. Merrill, R. E. Ries, J. R. Hendrickson, H. A. Johnson, and J. D. Hanson. 2002. Dynamic cropping systems: An adaptable approach to crop production in the Great Plains. Agron. J. 94:957-961. Teasdale, J.R., C.B. Coffman, and R.W. Mangum. 2007. Potential long-term benefits of no-tillage and organic cropping systems for grain production and soil improvement. Agron. J. 99:1297-1305. Trevewas, A. 2004. A critical assessment of organic farming-and-food assertions with particular respect to the UK and the potential environmental benefits of no-till agriculture. Crop Protection: 23-757-781.

    Project objectives:

    The primary objective of this project was to develop management recommendations for killing cover crops mechanically without tillage, and using the vegetative mulch that was produced for weed suppression in no-till organic grain production systems in the north central region. Specific objectives were to: (1) identify cover crop species and species mixtures that produced large amounts of above-ground dry matter (DM); (2) determine if cover crops could be killed effectively by rolling-crimping under environmental conditions in the north central region; (3) grow field crops successfully following rolling-crimping of cover crops; and (4) stimulate adoption of organic no-till methods on at least one organic farm in IA, MN, ND, and WI.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.