Use of black polyethylene tarps to advance reduced tillage system for organic beets

Abstract

Organic vegetable farmers rely on intensive tillage to control weeds, incorporate amendments and residues, and prepare seedbeds. Intensive tillage, however, can lead to a decrease in long-term soil health. The use of black, impermeable, polyethylene tarps on the soil surface prior to planting reduces weed pressure, increases crop yield, and preserves prepared soil for several weeks. Cultivar Boro beets were planted at three sites (Freeville, NY, Riverhead, NY, Monmouth, ME), two years (2017 and 2018), on two dates (May and June). Tarps were applied and left in place for three time periods prior to projected planting dates: 1) either overwinter (early planting) or 10+ weeks (late planting), 2) 6-8 weeks, 3) 3-5 weeks, and 4) no tarp. After tarp removal, plots were tilled to 4-8 in. (conventional till), 1-3 in. (reduced till), or left undisturbed (no-till), then direct-seeded with beets. Soil environment, weed pressure, and crop yield were measured at pre- and post-tarp removal, midseason, and at harvest. Tarp use increased soil moisture and nitrate concentrations, and increased soil temperature by 1-3°C compared with bare ground at the time of removal. Tarps did not decrease crop residue. Tarp use of three or more weeks reduced weed percent cover by 95-100% at the time of tarp removal, and retained lower weed pressure for 10 days in most site years. Tarp use increased crop yield, and decreased the difference between tillage treatments for weed biomass and crop yield, making reduced tillage a more viable option in organic vegetable systems.