A Systems Comparison of Contrasting Organic Weed Management Strategies

Abstract

Weed management strategies differ in their ability to control weeds, and often have unique agroecological implications. To provide growers with an improved sense of trade-offs between weed control and ecological effects, we implemented several prominent organic weed management strategies in yellow onion in 2014 and 2015. Strategies included cultivation of weed seedlings during the early, weed-sensitive “critical period” of the crop; frequent cultivation events to ensure “zero seed rain”; and weed suppression with polyethylene or natural mulches. As expected, end-of-season weed biomass and weed seed production were greatest in the critical period system and nearly zero for the zero seed rain system. Weeds were also well controlled in natural mulch systems. Average onion yield per treatment was 50.7 Mg ha−1. In 2014, the critical period system and the polyethylene mulch systems demonstrated yield loss, likely due to weed competition and excessive soil temperature, respectively. Onion soluble solids content was also diminished in these systems in 2014, but bulb firmness was greatest in unmulched systems. Carabid beetles, earthworms, soil compaction, soil nitrate, and microbial biomass were affected by weed management strategy, with natural-mulched systems generally performing most favorably. However, these effects were not substantial enough to affect yield of a subsequent sweet corn crop grown in weed-free conditions. In contrast, sweet corn managed with only early-season cultivations demonstrated yield loss (P=0.004) in plots where the critical period treatment was implemented the prior year, indicating that weed competition resulting from abundant weed seed production in that system was the most influential legacy effect of the weed management strategies.

To each their own: case studies of four successful, small-scale organic vegetable farmers with distinct weed management strategies

“…For example, crop growth is most impacted by weeds in the early-season ‘critical period’ (Nieto et al, 1968; reviewed by Knezevic et al, 2002); thus, for farmers that consider labor as the main risk of weeds, they may limit weed control efforts to the critical period of each crop (Jabbour et al, 2014 a , b ). However, this strategy often allows late-season weeds to produce seeds, resulting in abundant ‘seed rain’ and a large weed seedbank (Norris, 1999; Jabbour et al, 2014 a ; Brown and Gallandt, 2017).…”

“…Farmers may also use mulch to suppress weeds (Baker and Mohler, 2014; Brown and Gallandt, 2017), a strategy most frequently employed in high-value vegetable crops. In northern temperate regions, black plastic mulch is often used for its soil warming properties.…”

“…Clearly, each of these weed management strategies have different ecological (Brown and Gallandt, 2017) and economic consequences; however, an applied understanding with respect to the impacts of each strategy on the management of working organic farms remains lacking. We hypothesized that the farmer motivations and practical implications related to each strategy would differ, thereby highlighting tradeoffs between each strategy.…”

Soil conservation practices for insect pest management in highly disturbed agroecosystems – a review

“…A recent systems comparison evaluated the ecological (Brown & Gallandt, 2018) and economic effects of black plastic mulch, hay mulch, and two cultivation-based weed management strategies (critical period weed control and a zero seed rain approach) in onion (Figure 1). Aboveground weed biomass did not differ between the hay-mulched treatment and the zero seed rain treatment, which was cleanly cultivated about every 10 days throughout the season.…”

Efficiency of the Adapted Automatic Row Hoe for Weed Control in Organic Soybean

“…The control of weeds in agricultural organic systems has been mentioned by the farmers as one of the main barriers for the organic production and, the adoption of integrated weed management practices (IWMP) is still minimal [1][2][3].…”