Tarping Cover Crops Facilitates Organic No-till Cabbage Production and Suppresses Weeds

Abstract

Small-scale vegetable farmers are interested in cover crops and reduced tillage, but scale-appropriate technology and equipment are necessary to expand these practices to the growing segment of small farms. We sought to determine the efficacy of tarps, an increasingly popular tool on small farms, to end overwintering cover crops and provide weed suppression for subsequent no-till cabbage production. In three fields over two seasons in Maine, we grew a winter rye (Secale cereale L.) and hairy vetch (Vicia villosa L.) cover crop, which we managed by a factorial combination of tillage (no-till, till) and tarping (tarp, no-tarp) in June, followed by a transplanted cabbage crop (Brassica oleracea L. var. Capitata) in July. Within each treatment, subplots were either weeded by hand or left unweeded. Cover crop biomass ranged from 2.8 to 4.5 Mg⋅ha−1. Mean cabbage weights in the novel no-till system (no-till/tarp) were greater than (year 1) or equal to (year 2) those in tillage-based systems (till/no-tarp and till/tarp). In year 1, the mean cabbage weight in weeded subplots was 48% greater in no-till/tarp than in till/no-tarp systems. In unweeded subplots, this difference was 270%, highlighting the efficacy of the no-till/tarp system to reduce the impact of weeds. In year 2, weed biomass was higher with all treatments than it was in year 1, and unweeded subplots failed to produce marketable heads (i.e., >300 g). The mean cabbage weight in weeded subplots was equal among no-till/tarp, till/tarp, and till/no-tarp systems. Tarping had a strong effect on weed biomass and weed community composition measured at the time of cabbage harvest in unweeded subplots. In year 1, weed biomass at the time of cabbage harvest with tarp treatments was less than half that with no-tarp treatments. Tarps effectively facilitated the cover crop mulch-based no-till system. We propose that this system is an adaptive strategy for farmers affected by climate change. However, both cover crop production and tarping shorten the growing season. We discuss tradeoffs and opportunity costs using the metric of growing degree days.

Tarping and mulching effects on crop yields, profitability, and soil nutrients in a continuous no-till organic vegetable production system

“…In contrast, yields in NTT were either greater than or equal to CT across all years. Lower yields in NT organic vegetable systems are often attributed to greater weed densities (Delate, Cwach and Chase, 2012; Lilley and Sánchez, 2016; Rylander et al, 2020a, 2020b; Lounsbury et al, 2022). However, multiple crop cultivations and hand weeding events were performed to minimize crop-weed competition (Table 1), including a zero-seed rain approach (Brown and Gallandt, 2019) within NT and NTT systems.…”

“…Tarps can also be used in NT applications to overcome some of the common barriers to NT adoption. Tarping has shown to effectively terminate living weeds and cover crops prior to planting (Lounsbury et al, 2020; Rylander et al, 2020a), increase soil nitrogen availability (Rylander et al, 2020a), reduce weed competition for the following crop, and increase crop yields (Rylander et al, 2020b; Lounsbury et al, 2022). Farmers often cite tarps’ weed suppression benefits while acknowledging their labor and logistical challenges (Kinnebrew et al, 2022), but the effects of tarping on labor requirements and profitability in NT systems are not well-documented.…”