Kathleen Delate, Iowa State University: Organic no-till
Watch Professor Delate's video about organic no-till farming
When did you start researching organic no-till processes?
In 2005, the Rodale Institute invited Iowa State University (ISU) to join a consortium with it and UC-Davis, Michigan State, University of Georgia and Virginia Tech to participate in the first multi-state research on no-till systems for organic farming. As a member of the USDA-NRCS Conservation Innovation Grant that supported this consortium for No-Till for Organic Systems (“No-Till Plus”), I conducted research on managing cover crops in organic grain and vegetable systems at two ISU research farms and an on-farm site. From 2008–2012, I served as a the Principal Investigator of an organic no-till consortium of six institutions (ISU, University of Wisconsin, University of Minnesota, North Dakota State University, Michigan State University, and the Rodale Institute) on the USDA-NRI Integrated Organic Program (IOP) grant project I wrote, entitled Developing Carbon-Positive Organic Systems through Reduced Tillage and Cover Crop-Intensive Crop Rotation Schemes. Crop performance, soil quality, and weed management parameters in this project were evaluated. We also completed a USDA-SARE project on “Organic Corn in No-Till Systems,” established in partnership with North Dakota State University and University of Wisconsin in 2009-2011 at the ISU Neely-Kinyon Farm, to examine the effect of five cover crops on organic corn production. In 2009, I initiated an expansion of this research from grain crops to vegetables with the University of Florida, and in 2010, we received funding for Enhancing Soil Health and Food Quality in Organic Vegetable Systems from the NIFA-Organic Transitions Program, which continues today. I also received funding from Ceres Trust to examine the performance of organic no-till soybeans following rolled/crimped and mowed rye. [A publication summarizing the organic no-till system is: Delate, K., D. Cwach, and C. Chase. 2012. Organic no–till system effects on soybean, corn and irrigated tomato production and economic performance in Iowa, USA. Renewable Agriculture and Food Systems 27(1):49–59. doi: 10.1017/S1742170511000524.]
What is organic no-till, and why is it different from tilling processes?
Some of the most critical needs of transitioning and certified organic growers are methods for enhancing soil fertility and managing weeds. Although weeds in organic systems are typically managed through a multi-pronged approach that includes cultural, biological and mechanical methods, currently organic producers primarily rely on tillage systems for weed management and field preparation. Increased use of strategies that enhance or sequester soil carbon on organic farms, such as reduced or no-tillage systems, will lead to decreased erosion and facilitate participation in government programs supporting reductions in carbon emissions. The main difference between conventional no-till farming and organic no-till is that conventional no-till relies on an herbicide to terminate cover crops, which has numerous draw-backs (including the use of a non-renewable resource), and recent health concerns on glyphosate expressed by the World Health Organization. Although plastic mulch is allowed in certified organic vegetable systems for weed management, many organic and conventional vegetable farmers are seeking alternatives to plastic mulch, which is expensive, difficult to dispose, and may have negative impacts on soil microbial activity. Natural mulches, including crushed and desiccated cover crops, have been proposed as an option in organic weed management. The most common cover crops planted in organic systems have included single species or combinations of rye, barley, wheat, hairy vetch, and crimson clover, due to their quick establishment, ability to over-winter, competitiveness with weeds, and ease of termination using mechanical methods. The cover crop combination of winter rye and hairy vetch offers great potential for enhancing crop yields and soil quality.
Cover crop termination methods using reduced tillage approaches offer the greatest potential for the dual purpose of weed management and enhancement of soil quality. Cover crops are planted in the fall and then rolled/crimped with a roller-crimper the following spring when the rye reaches anthesis (pollen shed). Our roller-crimper is 3.2 m wide x 41 cm diameter, and is mounted on a tractor. The ideal method is to mount the roller-crimper in front of the tractor, but it can be pulled if a front-mount is not available. The crushed cover crop should dry down within 1-2 weeks, and become a thick mulch, which ideally lasts throughout the season.
What are the benefits of using no-till systems? What about the benefits of using organic systems?
Organic no-till will decrease erosion, lower weed management costs, and ideally sequester carbon. Benefits ascribed to winter rye include carbon acquisition through biomass accumulation, residual soil nitrogen (N) scavenging, and reduced nitrate leaching. In addition, increased weed management from rye cover crops can be obtained through physical interference, antagonism and allelopathy. Hairy vetch is considered an excellent cover crop in terms of biomass production, providing some degree of weed suppression and nitrogen supplementation up to 138 kg N ha-1. Lysimeter data have shown that the concentration of leached N has been consistently lower under vegetables grown with a cover crop and in no-till. Soil quality comparisons show greater soil carbon sequestration with cover crops and compost.
The potentially negative effects of mechanical tillage on soil carbon can be mitigated by carbon additions from crop residues, cover crops and compost, but organic farmers continue to express interest in reducing tillage operations. John Teasdale published research showing that organic rotations had higher soil quality than conventional no-till (Teasdale et al., 2007). Our own research with Dr. Cynthia Cambardella of USDA-ARS has shown that soil organic carbon, total nitrogen, and extractable K and Ca were 5.7%, 9.5%, 14.2%, and 10.8% higher in organic soils, respectively, compared to conventional fields. Soil properties related to biologically active organic matter were up to 40% higher in organic soils. [Teasdale, J. R., Coffman, C. B., and Mangum, R. W. 2007. Potential long-term benefits of no-tillage and organic cropping systems for grain production and soil improvement. Agron. J. 99:1297-1305.]
What difficulties do you encounter when using an organic no-till system?
The most challenging no-till organic crop has been field corn for us in the Midwest. There seems to be additional competition for moisture and nutrients between the dying cover crop and the growing corn crop compared to soybeans that fix their own nitrogen, and vegetables, which are transplanted for a quick start. The other challenges include the cover crop maturing at the right time. If this occurs too late (i.e., past June 1), there could be a reduction in corn and soybean yield. Sometimes you may need to roll the cover crop more than once if it doesn’t stay down after rolling/crimping.
What crops work well for organic no-till? What crops need more research?
To date, our research has determined that organic soybean, tomato, pepper and squash crops can be successfully produced in the organic no-till system, with yields equal to tilled organic systems, but with reduced weed management costs. Organic no-till corn has not been successful in the Midwest, but Pennsylvania trials have shown successful organic no-till corn crops. Challenges currently under investigation include moisture competition between crop and terminated cover crop mulch, and incomplete termination of cover crops in wet years in the no-till system, which curtails its use for organic corn crops.
What types of machines are used for organic no-till?
Our roller-crimper was supplied by the Rodale Institute and manufactured by I & J Manufacturing (Gap, PA). Plans to build your own roller-crimper are available on the Rodale Institute website: rodaleinstitute.org/our-work/organic-no-till/.
Once you roll/crimp your cover crop, you will either direct-seed with a mechanical, tractor-pulled seeder or a drill if planting in narrow rows; or plant vegetable transplants by hand or with a mechanical transplanter. One of the topics of my sabbatical leave in Italy was a new innovation: an “in-line” cultivator that opens a slit through the flattened mulch to perform mechanical- or hand-transplanting of vegetable transplants. This is shown in the video. We are investigating if we can get a patent for this innovation in the U.S.
What is most important to keep in mind when you are using organic no-till?
Plant a heavy rate of cover crop (e.g., 2 bushels/acre of rye) so you have lots of biomass for weed management in the spring/summer. Roll/crimp when the rye is in anthesis or past that; rolling sooner will create uneven mulch that may not stay down. If you need to weed (i.e., weeds are excessive through the mulch), plan on doing hand-weeding or tilling (a high-residue cultivator is best), because you do not want to lose your crop. Organic no-till is still in its infancy, so experimentation is warranted.
What do you see as the future for organic no-till in the United States?
I think the future is bright: there are numerous organic researchers working on organic no-till systems—in Iowa, Wisconsin, Michigan, Minnesota, North Carolina–and of course, Rodale continues this important work. Continued research funding is needed to perfect the system for each climatic zone.