Weed Management and Soil Quality Outcomes of Non-Chemical Weed Control Tactics.

From 2015 to 2017, field experiments were conducted to investigate tillage system (no-till/hay mulch vs. tilled) and arbuscular mycorrhizal fungi (AMF) inoculant impacts on onion, beet, winter squash, and snap pea performance, soil quality, and weed suppression in certified organic vegetable production systems in Absaraka and Dickinson ND. Weeds were removed from all plots on a timely basis, so yield differences among treatments were due to factors other than crop-weed competition. Hay mulch almost completely suppressed weeds whereas weed pressure in the tilled plots was considerable. Tilled plots required substantially more weeding time than the no-till plots. In general, the mulched no-till system was associated with greater crop yield than the tilled system, except for squash. The AMF inoculant did not impact crop yield. Beets grown in tilled plots had greater leaf chlorophyll than those grown in mulched plots (307 vs. 278 mg/m²), whereas onions grown in mulched plots had greater leaf chlorophyll than those grown in tilled plots (328 vs. 309 mg/m²). Pea and squash leaf chlorophyll were not influenced by tillage system. Beet plants grown in tilled plots had greater stomatal conductance than beets grown in mulched plots (492 vs. 450 mmol per m²s). Mulched plots had greater soil N than tilled plots when the previous crops were beet (45 vs. 32 lbs N/acre) and squash (59 vs. 30 lbs N/acre). When plots were tilled, soil N did not differ among previous crops. But when plots were mulched and not tilled, plots previously cropped to squash had greater soil N than plots previously cropped to beet (59 vs. 45 lbs N/acre), onion (59 vs. 45 lbs N/acre), and pea (59 vs. 41 lbs N/acre). Soil phosphorus, potassium and organic matter were not influenced by tillage system or AMF. These results indicate that no-till mulched systems can benefit organic vegetable production.