Tarping has become a popular practice for small-scale organic farms to manage weeds. Typically, beds are tilled and prepared for planting and then covered using a durable, black plastic tarp. Tillage combined with warming soils under tarps can promote the germination of weed seeds which then die when starved for light. Tarps are then removed weeks later, prior to planting, with the goal of reducing weed pressure for the following crop. Our research has focused on how to manage tarps with reduced tillage practices. We continue to learn from these trials and from grower experience on their own farm. We have found tarps can help suppress weeds while also changing the soil environment, labor needs, and the profitability of no-till production.
What are we learning? Check out these resources:
- We shared some research results from trials looking at how tarps impact weeds and soils in the Small Farms Quarterly. (Winter 2019)
- Read about local farms have trialed tarping on our blog. (Fall 2018)
- Read some of our early lessons learned using tarps to reduce tillage in the Small Farms Quarterly. (Spring 2018)
- Hear details on our research in permanent beds in our RT Webinar Series. (Spring 2017)
- Read about no-till tarping practices at Seeds of Solidarity Farm in the Small Farm Quarterly. (Fall 2016)
No-till tarping practices are compared side-by-side to no-till and conventional tillage in permanent beds on the Cornell Thompson Research Farm in Freeville, NY. Parallel research is happening at the Highmoor Farm in Monmouth, ME in collaboration with the University of Maine.
Tarps are impermeable, durable (>5mil) black plastic. They pond rainwater and snowmelt and restrict the flow of water into beds. We have found elevated soil nitrate after tarp removal, a combination of warm temperatures under tarps and less leaching over winter and early spring.
After applied for 3 weeks in spring, we have found tarps to kill winter annual weeds, like chickweed. When fields are too wet for any tillage, tarps can be applied and then hold beds idle until they are needed for planting.
Tarps have created weed-free planting beds without tillage and have also shown to reduce the time needed for hand weeding during the season. We are looking at how tarps effect weeds, soils and crop production in both mulched and bare soil.
Pathway weeds can be difficult to manage in permanent beds when primary tillage is restricted the bed. Tarps have shown to suppress weeds in pathways (right) in comparison to conventionally managed beds (left).
We still find perennial weeds, like nutsedge, after tarp removal in spring.
Tarps and sandbags require labor to apply and remove but we have found the labor saved in preparing beds compared to no-till without tarps can be dramatic. Total annual labor in tarped beds has been similar to those that are conventionally tilled.