Environmental Correlates with Germinable Weed Seedbanks on Organic Farms across Northern New England

Abstract

The northern New England region includes the states of Vermont, New Hampshire, and Maine and encompasses a large degree of climate and edaphic variation across a relatively small spatial area, making it ideal for studying climate change impacts on agricultural weed communities. We sampled weed seedbanks and measured soil physical and chemical characteristics on 77 organic farms across the region and analyzed the relationships between weed community parameters and select geographic, climatic, and edaphic variables using multivariate procedures. Temperature-related variables (latitude, longitude, mean maximum and minimum temperature) were the strongest and most consistent correlates with weed seedbank composition. Edaphic variables were, for the most part, relatively weaker and inconsistent correlates with weed seedbanks. Our analyses also indicate that a number of agriculturally important weed species are associated with specific U.S. Department of Agriculture plant hardiness zones, implying that future changes in climate factors that result in geographic shifts in these zones will likely be accompanied by changes in the composition of weed communities and therefore new management challenges for farmers.

Weed germinable seedbanks of rice–wheat systems in the Eastern Indo‐Gangetic Plains: Do tillage and edaphic factors explain community variation?

“…The response variables were the individual NMDS ordination axis scores. Predictor variables with variable importance values greater than 0.8 were retained in the final models (Smith et al, 2018 ), and model predictive ability was determined with K ‐fold cross‐validation ( K = 10).…”

“…Factors other than tillage may influence weed community composition in the Eastern IGP, such as edaphic properties and topography. In other regions, edaphic properties, such as soil texture, pH and nutrient status, have been shown to be strong predictors of the variation in weed communities (Fried et al, 2008 ; Korres et al, 2017 ; Smith et al, 2018 ). Rice–wheat production in the Eastern IGP occurs in both upland (less flooding and drier) and lowland (more flooding and wetter) topographies, which likely cause variation in weed community composition due to variation in flooding and soil drainage.…”

“…The composition of the germinable seedbank determines which weed species, especially annuals, could potentially infest the succeeding crop (Mahé et al, 2020 ; Smith et al, 2018 ). Additionally, the composition of the germinable seedbank reflects the success of weed management in proceeding years, because relative competitive success and fecundity will influence relative abundance in the seedbank of subsequent years.…”

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

“…Our data suggest that although most weed species present were suppressed by tarping cover crops (i.e., combining the two filters of cover crop mulch and tarps), some were more capable than others of "passing through" these filters, including A. retroflexus. A. retroflexus is one of the most common weeds found on organic farms in Maine and other New England states (Smith et al, 2018). Rylander et al (2020) found that seeds of a closely related species, A. powelli, had greater survival (i.e., retained viability) under tarps compared with bare soil.…”

Exploring the effect of region on diversity and composition of weed seedbanks in herbicide‐resistant crop systems in the United States

“…23,24 Furthermore, previous studies endeavored to connect geographic regions with the structure or composition of weed seedbanks. Smith et al 25 demonstrated that geo-climatic factors were closely associated with soil weed seedbank richness, seedbank species composition, and total seedbank population density. Studies also noticed that regional distinction of weed species pool contributed to species composition of weed seedbank.…”