Making the Most of Mulch: Strategic Systems for Small Organic Tomato Growers

View the project final report

Commodities

• Agronomic: clovers, rye, vetches
• Vegetables: tomatoes

Practices

• Crop Production: cover crops
• Education and Training: participatory research
• Natural Resources/Environment: carbon sequestration
• Soil Management: green manures, organic matter

Organic mulches can suppress weeds while promoting soil health and carbon storage among other benefits. Mulches created from nitrogen-fixing cover crops, such as white clover and hairy vetch, are particularly attractive for nitrogen-demanding crops such as tomato. Yet reliability and convenience often turn farmers to plastic mulch, a fossil-fuel intensive product that generates substantial landfill waste and helps retain but does not build soil nutrients or organic matter. Straw is another common mulch choice, but can contain weed seed, promote mold, and lead to crop nitrogen deficits.

To increase their viability for small, organic farmers, cover crop mulches must be optimized for organic contexts, where herbicide is not an option for controlling either incomplete weed suppression or competition from living cover crops. We worked with farmers to test combinations of cover crops (living white clover or residue of winter rye-hairy vetch) and leaf mulch against plastic and straw mulches for organic fresh-market tomato production on three Indiana small farms. Farmers were interviewed before and after the research to explore their attitudes about and understanding of cover crops.

We found that although leaf mulch strips did improve cover crop performance, plastic or straw mulches still outperformed cover crops in terms of weed suppression and tomato yield. Results suggest that over time, cover crop mulches may promote greater soil health and carbon storage compared with plastic and straw mulches. Our results warrant follow-up research to test these cover crop strategies against different weed backgrounds. Cover crop mulches with leaf mulch strips may suppress weeds more effectively once farmers have worked to reduce the overall weed seed bank in the soil. Farmers appreciated that engaging in formal research experiments with professional researchers presented opportunities to learn about new, innovative production systems. We observed that our research led to increased interest in and use of cover crops on two of the farms. And while farmers acknowledged that it can be challenging to juggle research with production goals, there is interest in engaging in follow up research.

1. Establish replicated mulch treatments and controls at three partner farms
2. Collect and analyze soil, cover crop, weed, labor and crop data to assess optimal mulching strategies
3. Share project rationale, methods and results with farmers and agricultural professionals via a video, extension-style technical report, IU Campus Farm webpage, Indiana Small Farms Conference poster presentation, and agronomic journal article