Improving reduced tillage vegetable systems for the Northern Great Plains: How does early season soil tarping (solarization and occultation) impact soil health?

Much of the research for tarping and soil health has taken place in the northeastern United States, and minimal research has applied early season tarping in a drier, sunnier climate such as the US Midwest. This study in Brookings, SD, evaluated soil health impact from early season (April through May) solarization and occultation at different durations (6, 4, and 2 weeks) used for weed control in onion (Allium cepa) production during 2023 and 2024. Solarization was conducted using greenhouse plastic, while occultation was evaluated using both white side up and black side up silage tarps. A randomized complete block design with four blocks and ten treatment plots per block, including an untarped, tilled control, was established. Immediately following tarp removal, clear and untarped control plots were tilled to remove high weed pressure, and all planting beds were harrowed within each plot where onions were planted. Soil response variables included inorganic nitrogen (N), soil respiration, active carbon (POXC), organic N, temperature, and moisture. Daily temperatures were up to 6°C higher in solarized plots compared to occultation plots during tarping. Occultation treatments showed trends of lower moisture during tarping and higher moisture during the growing season when compared to control plots. No differences were seen among tarp treatments for N, soil respiration, or POXC. While early season soil tarping used in the US Midwest can manipulate temperature, our research showed no significant impacts on other soil health indicators.