2018 ASHS Annual Conference

The use of plastic mulch (PM) is common for warm-season organic vegetable production in Michigan. While PM offers excellent weed control in-row, weed management between-row remains a challenge. Organic growers employ a variety of strategies to manage this area including cultivation, mowing, straw mulching, and less commonly, planting cover crops as living mulches. While these practices impact crop production and soil quality differently, information regarding the potential benefits and tradeoffs of each management strategy is lacking. The objective of this study is to clarify how between-row management affects both crop production and soil health indicators, allowing growers to make informed management decisions considering their unique farm context and goals. Strategies (treatments) evaluated in this study included weed-free wheel-hoe cultivation, rye cut and carry (dead) mulch, mowing weeds, rye living mulch, rye/white clover living mulch, and Italian ryegrass living mulch. These strategies were implemented between bell pepper (Capsicum annuum cv. Paladin) and summer squash (Cucurbita pepo cv. Lioness) grown on PM to allow for comparisons between a relatively short- and long-duration crop.

First year (2017) results demonstrate that competitive inhibition by living mulch and weeds is cash crop dependent. Summer squash yields were consistent across management strategies, but total pepper yields were reduced by an average of 453g per plant (~30%) in all treatments compared to weed-free cultivation. Cumulative biomass production in the between-row area was not significantly different between mowed weeds and living mulch treatments, averaging 490g m^-2 biomass accumulated over the course of the growing season. Dead mulch reduced in-season weed biomass by 75% relative to the mowed weeds control, more than any living mulch species. Italian ryegrass was the only living mulch species to significantly decrease in-season weed biomass with a 52% reduction. Both mowed weeds and living mulch plots were able to scavenge between-row nitrogen, resulting in significantly less potentially leachable nitrogen in the fall (0-60 cm soil depth) compared to dead mulch and weed-free cultivated treatments. Significant differences in soil microbial biomass and shifts in soil microbial communities were not observed at any of four sampling dates during the first year of this study. However, this trial will be repeated in the same location in 2018 to evaluate cumulative impacts of between-row management on soil organic matter, microbial activity, and weed seedbanks.