Not All Tillage Is Created Equal

Balancing Soil Health and Weed Management in Organic Farming

By Thelma Velez and Heather Estrada

Organic farmers are often praised for their commitment to environmental stewardship. Indeed, these growers must adhere to rigid standards set forth through the National Organic Program, which delineates what is (and is not) allowed on organic operations. These standards are key to ensuring that the certified organic label is the same across the country. While many argue there is room for improvement in the label (and its enforcement), one thing is certain—farms under organic management are more ecologically sustainable than conventional operations. Organic farms are better for the environment, better for the people, and better for the planet. 

That said, organic farmers also face extensive criticism regarding their use of tillage. There is no denying that excessive or poorly timed tillage can lead to soil erosion or nutrient run-off, and there is mounting evidence that tillage can disturb fungal networks, harm larger soil organisms, and increase the decomposition of soil organic matter (SOM). However, it is worth “digging in,” “turning over,” and “exposing” why organic farmers till in the first place and how tillage practices and outcomes differ.

Why Do Organic Farmers Till?

So why do organic farmers till? In 2022, we published our National Organic Research Agenda (NORA) report. Organic farmers across the country indicated that their number one production challenge is managing weeds on their farms (Snyder et al., 2022). Tillage in organic systems is used for a variety of reasons, including weed management, but also for terminating cover crops or preparing seedbeds. While conventional growers use synthetic herbicides to terminate weeds, organic farmers are not allowed to apply these chemicals to the soil, nor would they want to, given the extensive evidence of the harm these chemicals cause to both humans and ecosystems. 

Building and maintaining healthy soil is the key for most successful organic farming operations (yes, this includes dairy and livestock operations where animals graze on pasture). Thus, co-managing soil health while also tackling weeds is something organic farmers deal with on a regular basis. Interestingly, there are researchers and farmers who have been studying soil for decades to better understand the impacts of tillage on different parameters of soil health, and what we are learning is that not all tillage is created equal. In fact, there are organic farms across the country that have been finding ways to keep weeds at bay while also improving soil health.   

The science of the last decade has begun to unravel some of the complexities related to how tillage depth and intensity affect soil organisms and soil organic carbon. 

Impact of Tillage on Soil Health

Studies have documented improvements in active soil organic carbon (SOC) and other soil health parameters when combining cover crops and compost applications, even with tillage (Cogger et al., 2013; Delate et al., 2015). Results from six long-term farming systems trials with organic crop rotations that included legume cover or sod crops, organic nutrient sources (compost or manure), and routine tillage actually accrued significantly more SOC than conventional corn-soybean rotations (Delate et al., 2015).  

Variability in Tillage Methods

Tillage is not a one-size-fits-all approach. There are major differences between deeper inversion tillage and shallow non-inversion tillage. In one meta-analysis, shallow inversion tillage resulted in higher soil carbon, more effective weed control, and only minimal yield reductions when compared with deeper tillage (Cooper et al., 2016). 

More invasive approaches, such as a moldboard plow, disk plow, or chisel plow at depths greater than six inches, will inherently create more disturbance, but taking a more shallow and judicious tillage approach is generally less harmful to soil health and can be compatible with soil building goals (Schonbeck et al., 2017; Dimitri et al., 2012). 

Additionally, there are meta-analyses with promising findings related to enhanced soil life in reduced tillage systems (Chen et al., 2016;  Li et al., 2020; Morugán-Coronado et al., 2022). Morugán-Coronado’s 2022 paper also included findings showing that reduced tillage systems outperformed full-tillage and no-till with respect to increases in microbial and fungal biomass (Morugán-Coronado et al., 2022).

Balancing Tillage and Soil Health in Organic Farming

While tillage is an essential tool in organic farming, its impact on soil health is complex and varies depending on the method and intensity used. The evolving science of soil management suggests that organic farmers can adopt practices that minimize soil disturbance while addressing production needs. This balanced approach helps to preserve and enhance soil health, supporting the overall sustainability of organic farming systems. 

For more information on balancing tillage and soil health, check out our guidebook “Practical Conservation Tillage,” which provides a practical means to reduce tillage and protect soil organic matter, soil life, and tilth through green manures, compost applications, and other organic practices.

How do you manage tillage in your farming practices? Email us at info@ofrf.org to share your experiences and insights, and stay informed about the latest research to continually improve your soil management strategies by signing up for our newsletter here.

References

Chen, G., C. R. Hooks, M. Lekveishvili, K. H. Wang, K. H., N. Pradhan, S. Tubene, S., R. R. Weil, and R. Ogutu. 2015. Cover Crop and Tillage Impact on Soil Quality, Greenhouse Gas Emission, Pests, and Economics of Fields Transitioning to Organic Farming. Final report for project ORG 2011-04944. CRIS Abstracts.

Cogger, C. G. M. Ostrom, K. Painter, A. Kennedy, A. Fortuna, R. Alldredge, A.; Bary, T. Miller, Collins, J. Goldberger, A. Antonelli, and B. Cha. 2013. Designing Production Strategies for Stewardship and Profits On Fresh Market Organic Farms. OREI award 2008-51300-04460. https://nifa.usda.gov/data/data-gateway.

Cooper, J., Baranski, M., Stewart, G., Nobel-de Lange, M., Bàrberi, P., Fließbach, A., Peigné, J., Berner, A., Brock, C., Casagrande, M., Crowley, O., David, C., De Vliegher, A., Döring, T. F., Dupont, A., Entz, M., Grosse, M., Haase, T., Halde, C., … Mäder, P. 2016. Shallow non-inversion tillage in organic farming maintains crop yields and increases soil C stocks: a meta-analysis. Agronomy for Sustainable Development, 36, 22. https://doi.org/10.1007/s13593-016-0354-1

Delate, K., C. Cambardella, and C. Chase. 2015. Effects of cover crops, soil amendments, and reduced tillage on Carbon Sequestration and Soil Health in a Long Term Vegetable System. Final report for ORG project 2010-03956. CRIS Abstracts

Dimitri, C., L. Kemp, J. Sooby, and E. Sullivan. 2012. Organic Farming for Health and Prosperity https://ofrf.org/wp-content/uploads/2019/09/HP-report-web.pdf

Li, Y., Q. Zhang, Y. Cai, Q. Yang, S.X. Chang. 2020. Minimum tillage and residue retention increase soil microbial population size and diversity: implications for conservation tillage. Sci. Total Environ., 716, 137164.

Morugán-Coronado et al., 2022. Agric., Ecosystems & Envir. 329, Article 107867.  Meta-analysis.

Schonbeck, M. D. Jerkins, and J. Ory. 2017. Soil Health and Organic Farming: Practical Conservation Tillage. https://ofrf.org/wp-content/uploads/2019/09/HP-report-web.pdf

Snyder, L., M. Schonbeck, T. Velez, and B. Tencer. 2022. 2022 National Organic Research Agenda: Outcomes and Recommendations from the 2020 National Organic & Transitioning Farmer Surveys and Focus Groups. Organic Farming Research Foundation.