Abstract
Weed communities can be influenced by nutrient availability, nutrient form (e. g., ammonium vs. nitrate), amendment timing, amendment type (e.g., organic vs. inorganic), and by immigration of seeds during amendment applications. The objective of this research was to compare the long-term effect of different fertility treatments in a corn (Zea mays L.)-alfalfa (Medicago sativa L.) rotation on taxonomic and functional structure and composition of weed communities by analyzing the soil weed seedbank. After 14 years of a long-term experiment in Aurora, NY, United States, soils were sampled in five fertility treatments for corn years in the rotation: liquid dairy manure, semi-composted separated dairy solids; or inorganic nitrogen (N) as starter fertilizer with either no sidedress N, a low rate or a high rate of inorganic N as sidedress fertilizer. Soil was collected in early spring 2015 and a greenhouse weed seed germination bioassay was used to quantify the germinable soil weed seedbank. Total weed seedbank density, species richness, and evenness did not vary by treatment. However, fertility treatments modified the ecological niche represented by 20 environmental descriptors, which filtered the weed community creating distinct functional group assemblages. A trait-based analysis revealed that nitrophilic dicotyledons preferring alkaline soil were associated with high concentrations of inorganic N fertilizer, whereas highly specialist monocotyledons preferring high amounts of light were associated with low concentrations of inorganic N fertilizer. Because fertility treatments affected weed community composition but not seed bank density and richness, results encourage the development of holistic management strategies that adopt coherent weed management and crop fertilization.
Highlights
Weeds are a major constraint to crop production (Adeux et al, 2019b)
Understanding the effects of different nutrient management strategies on weed community assembly can contribute to ecological weed management and reduce reliance on soil tillage and herbicides
A total of 22 weed species recorded across the whole experiment: Chenopodium album (Common lambsquarters, 100% of frequency of occurrence), Taraxacum officinale (Dandelion, 90.9%), Digitaria sanguinalis (Large crabgrass, 59.1%), Oxalis sp. (Woodsorrels, 59.1%), Solanum sp. (Nightshades, 50%), Panicum dichotomiflorum (Fall panicum, 36.4%), Amaranthus sp. (Pigweeds, 27.3%), Plantago major (Broadleaf plantain, 27.3%), Setaria pumila (Yellow foxtail, 27.3%), Abutilon grandifolium (Hairy Indian mallow, 27.3%), Hibiscus trionum (Venice mallow, 27.3%), Veronica persica (Persian speedwell, 13.6%), Ambrosia artemisiifolia (Common ragweed, 9.1%), Juncus tenuis (Path rush, 9.1%), Panicum capillare (Witchgrass, 9.1%), Trifolium hybridium (Alsike clover, 9.1%), Atriplex patula (Spear saltbush, 4.5%), Chenopodium glaucum (Oakleaf goosefoot, 4.5%), Eragrostis sp. (Lovegrasses, 4.5%), Lamium amplexicaule (Henbit, 4.5%), Senecio vulgaris (Common groundsel, 4.5%), Stellaria media (Common chickweed, 4.5%)
Summary
Weeds are a major constraint to crop production (Adeux et al, 2019b). Concerns about herbicide resistance, environmental impacts, and human health effects associated with standard weed management strategies (e.g., herbicide use and soil tillage) have prompted renewed interest in ecological weed management (Liebman et al, 1997; Mortensen et al, 2000; Petit et al, 2018; Maclaren et al, 2020). Community assembly theory has been proposed as a strategy for understanding and predicting weed species response to management practices (Booth and Swanton, 2002; Gaba et al, 2017; Smith and Mortensen, 2017). Environmental filters such as crop type, crop sequence (Fried et al, 2008; Mahaut et al, 2019), soil disturbance, and disturbance timing (Cordeau et al, 2017c) have been explored previously; limited information is available about the role of long-term nutrient management on weed community assembly in agroecosystems. Understanding the effects of different nutrient management strategies on weed community assembly can contribute to ecological weed management and reduce reliance on soil tillage and herbicides
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