Improving Reduced Tillage Vegetable Systems for the Northern Great Plains: How Does Early Season Soil Tarping (Solarization And Occultation) Reduce Weeds, Affect Soil Health, and Protect Yield?

Soil tarping (solarization and occultation) is a no-till weed management practice gaining popularity in the United States for small scale vegetable growers. While many studies have been conducted using variations of this tool in the Northeast United States, minimal research has been done in the windier, sunnier, Midwest climate. Our research explored the effectiveness of early spring solarization and occultation to manage weeds and produce viable onion yield in Eastern South Dakota. Occultation tarps placed in early spring included double sided black and white silage tarps with tarps placed black side up or white side up, each placed 6-, 4-, or 2 weeks before tarp removal in late spring. Occultation treatments were compared to a no-tarp control and solarization treatments using clear greenhouse plastic with the same field placement timing intervals. Results suggest that occultation has the potential to be used for reducing annual weed pressure at removal, but not during the growing season, while solarization has the potential to exhaust the weed seed bank at tarp removal and reduce weed pressure during the growing season. No difference was seen for onion yield due to treatments, and other weed management strategies, such as hand weeding, were still required to maintain viable yield. Clear and black tarps increased soil temperature during tarp application but had no effect on soil moisture, microbial activity, or nitrate levels. Soil tarping has the potential to reduce weed pressure in reduced or no-till vegetable production in the Midwest, however, further research should be conducted on the time of year this tool can be used as well as which crops, such as larger canopy or shorter season, crops, are best suited to be used with soil tarping.