Cereal rye mulch biomass and crop density affect weed suppression and community assembly in no‐till planted soybean

Abstract

The use of multiple ecological weed management tactics may be an effective solution to weed management challenges associated with reducing tillage. An experiment was conducted to assess how soybean Glycine max (L.) Merr. density and cereal rye Secale cereale L. mulch biomass affected weed suppression and community assembly in no‐till production. Soybean was planted at five rates from 0 to 74 seeds m−2, and five cereal rye mulch levels were established from 0 to 2 times the ambient cereal rye biomass within each site–year. We assessed the effects of soybean density and cereal rye mulch biomass on weed suppression, weed community composition, and the functional structure of weed life cycle, emergence timing, seed weight, height, and specific leaf area traits. Weed suppression was influenced by a synergistic interaction between soybean density and cereal rye biomass. The functional dispersion (FDis) of all weed traits, when combined, was reduced by increased soybean density and mulch biomass, suggesting that high treatment intensities induced trait convergence. However, soybean density and cereal rye biomass had differing effects on the FDis and composition of individual traits, suggesting that these management practices represent unique filters during weed community assembly. Mulch biomass had a larger effect on annual weed suppression and weed community composition than soybean density. Farmers who utilize high biomass cover crop mulch for weed management may experience shifts in weed community composition toward an increased proportion of perennials and weeds with later emergence, heavier seeds, and shorter stature. Increasing soybean density may reduce perennial weed biomass, making it a valuable complement to high cereal rye mulch biomass. As such, weed management in no‐till soybean is enhanced by combining multiple practices, which can enable synergistic weed suppression and the management of diverse weed functional groups.

Cover crop management strategies affect weeds and profitability of organic no-till soybean

“…3a). Mennalled et al (2022) suggested that spring mulching affects early emergence of weeds, mostly annuals and grasses, primarily by physical interference (Teasdale and Mohler, 2000). The lack of planting date effect on broadleaf weeds may stem from the fact that perennial weeds sampled in this study, such as Trifolium spp.…”

“…The lack of planting date effect on broadleaf weeds may stem from the fact that perennial weeds sampled in this study, such as Trifolium spp. and Calystegia sepium, could emerge from vegetative structures with high amounts of stored resources (Mennalled et al, 2022). Broadleaf perennials such as Taraxacum officinale and Asclepias syrica were the species susceptible to mulch suppression, but the effect was not significant to have altered the community structure.…”

“…Termination methods altered weed species composition within and between the crop rows (Fig. 5b), possibly due to interaction with differing weed emergence phenology and trait dispersion (Mennalled et al, 2022; Ryan et al, 2010). Differences in grass and broadleaf assembly may be explained by weed seed placement in the soil layers as well as the availability of niche opportunities such as soil moisture and nutrients as driven by the degree of soil disturbances (Hernandez Plaza, Navarrete, and Gonzalez-Andújar, 2015).…”

Mechanisms of weed suppression by cereal rye cover crop: A review

“…A literature analysis (43 site‐years) of the effect of cereal rye biomass on percent weed suppression, calculated in comparison to a fallow treatment in similar year, location, and management conditions. Data were compiled from several studies conducted across the Southern, Midwestern, and Eastern regions of North America (Baraibar et al., 2018; Cornelius & Bradley, 2017; Hand et al., 2019; Korres et al., 2020; Menalled et al., 2022; Mischler et al., 2010; Nord et al., 2011; Norsworthy et al., 2011; Palhano et al., 2018; Pittman et al., 2020; Price et al., 2018; Reeves et al., 2005; Ryan, Mirsky et al., 2011; Samuelson, 2020; Teasdale et al., 1991; Vollmer et al., 2020; Webster et al., 2016; Wells et al., 2013, 2014; Williams et al., 2018). …”

Effect of multi‐tactic weed management on weed suppression and yield in the establishment year of intermediate wheatgrass

“…When farmers use multiple weed management tactics, they create dependable systems because if one tactic fails, others can continue to suppress weeds and maintain crop productivity (Lemerle et al., 2004). Likewise, using multiple weed management tactics allows farmers to diversify the selection pressures on weed communities, suppressing a greater range of weed functional groups (Menalled et al., 2022) and reducing the chances of developing weed resistance to a single management tactic (MacLaren et al., 2020). Multi‐tactic weed management can also result in synergistic interactions, where weed suppression from the combination of practices is better than expected based on the performance of each practice in isolation (Alba et al., 2020; Brown & Gallandt, 2018; Ryan et al., 2011).…”