While the use of black plastic is allowed within organic agriculture, it is inherently unsustainable, as it is a petroleum-based product and is difficult to recycle. Every acre of land farmed using a black plastic system produces 100-120 lb of waste that typically go to landfills. What’s more, 50-70% of a field is transformed into an impervious surface when black plastic is used, increasing the volume of runoff by 40% and erosion by 80%. And when herbicides and pesticides are used on fields covered in black plastic, the concentration of these chemicals in the fields’ runoff increases, making environmental and human health impacts even more of a concern. Finally, the increase in soil temperatures during hot summer days under black plastic mulch has been found to shift the soil organisms community towards bacterial rather than fungal and increase microbial stress. Black plastic is also a substantial annual cost to the farmer at $250-$300 per acre for the material and about $20 per acre for disposal.
With increases in cost of production and climate change, vegetable growers are looking into profitable and sustainable systems that increase soil health, reduce carbon foot print, and increase their profits. The Northeast Sustainable Agriculture Research and Education (NE SARE) Program provided Rodale Institute with funding in 2010 to launch a three-year vegetable trial focusing on cover crop alternatives to petroleum-derived disposable black plastic mulch.
While researchers have made great headway in developing and demonstrating the efficacy of cover crop mulch systems, most of the systems that have been developed rely to some degree on synthetic herbicides to supplement the weed control provided by the cover crops. For this reason, researchers at Rodale Institute have been working to develop a cover crop mulch system in which herbicides are not necessary for weed suppression, furthering the work of making cover crop mulch a viable option for organic as well as conventional vegetable producers.
The goal of the study was to measure the impacts of these different mulch systems on soil quality and fertility, weed control, yields and waste production, and profitability for small to mid-size vegetable operations. The vegetable trials at Rodale Institute compared cover crop nitrogen, potential carbon contribution, weed suppression, yields and soil health between rolled and mowed vetch, and rye cover crops, as well as commonly used black plastic. At the four collaborating farms in Pennsylvania and New Jersey, each farmer tested one cover crop system with the standard system.
The cover crop systems provided serviceable weed control, added more biomass to the soil, contributed nutrients, and increased soil moisture and percent total soil carbon. Although marketable yields were lower on average, some of the cover crop systems achieved higher profits across the three years. The cover crop mulch systems eliminated 91.5 lb of plastic waste per acre. Challenges related to extreme weather conditions and late blight meant results were more variable than anticipated, but all of the partner farmers continue to use what they’ve learned from the project to reduce their reliance on black plastic. Partner farmers experienced benefits including the discovery of a method for more effective cover crop kill, substantial cost savings, and new ways to use cover crops between rows for ecosystem benefits. One partner has already cut his black plastic use in half and hopes to expand even further.
Click here to download this 24-page guide that looks beyond plasticulture and evaluates the effects of different mulch systems on soil quality and fertility, weed control, yields and waste production, and profitability for small to mid-size vegetable farms.
This material is based upon work supported by Northeast SARE, under Subaward LNE 10-295.