Comparing soil tarping and solarization for early season weed control in vegetable crop systems - a research and demonstration study

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Commodities

• Vegetables: onions

Practices

• Crop Production: Tarping for weed management
• Education and Training: demonstration, on-farm/ranch research
• Pest Management: mulching - plastic
• Soil Management: soil analysis, soil microbiology

Vegetable production in Iowa and South Dakota has trended in the past twenty years towards very small farms growing a diversified range of vegetables. Weed control can be particularly challenging when growing numerous types of vegetables simultaneously; herbicide options are limited, and most of our growers prefer to minimize chemical use. Tillage is complicated by small plot sizes and the wide diversity of crop growth habits and cropping cycles. Using silage tarps as a method of controlling weeds and conditioning soil in these small diversified vegetable farms has enthusiastic adherents; the use is spreading in many areas of the U.S. and Canada. However, most of the research and demonstration of tarping has been in higher rainfall regions of the eastern U.S., with one SARE study as far west as Wisconsin.

We propose a two-pronged approach of testing tarping at research farms in Iowa and South Dakota, while simultaneously demonstrating their efficacy on cooperating farms across a range of soils and climate spanning from eastern Iowa to western South Dakota. The effects of short-term tarping treatments on soil health are largely unknown, so we also propose to assess effects of tarping durations of 14, 24, or 42 days on soil temperature, moisture, and microbial activity. Because our cooperating farmers had particular interest in controlling early season weeds, the tarps will be applied in the spring prior to later-season crops. We will also compare tarping to early-season solarization, using clear plastic, which warms the soil much more efficiently, likely leading to germination of warm season weeds so that they can be controlled prior to planting the desired crop.

The demonstration farms will use management practices appropriate to their farm; some may tarp over cover crops, while others may use tillage prior to tarping. Thus we will gain information on an array of on-farm practices that may impact tarping efficacy. Because the demonstration farms will cover a wide variety of soils and span a range of 18 to 36 inches precipitation per year, we expect that there will also be variation in weed species and their response to tarping. Growers and researchers will have the opportunity to observe various practices (including no tarping) and impacts. Results will be available to a wide audience through field days, webinars, videos, reports, and presentations at grower meetings.

Objectives:
1. Compare efficacy of tarps (occlusion) vs. clear plastic (solarization) vs. no plastic for minimizing early season weed pressure under a range of soils and climates
2. Demonstrate on-farm feasibility of using tarps across a range of soils, climates, and management practices
3. Investigate the effect of occlusion or solarization on soil microbes and soil health

Learning outcomes:
+ Participants will learn how to manage tarps or plastic for maximum efficacy and profitability on their farms
Action outcomes:
+ Tillage and/or herbicide use will be reduced on farms using tarps
+ Using recycled tarps reduces landfill waste