Solaria Help Predict In-Crop Weed Densities1

At locations in Argentina and the United States, solaria (miniature, portable, plastic greenhouses or a plastic sheet approximately 1 m2) were placed on field soils in autumn or late winter in an attempt to predict summer annual weed densities. Initial emergence of summer annual weeds covered by solaria commenced weeks before that of weeds in exposed seedbeds. Cumulative emergence of many species in solaria reached asymptotes before crops were sown. At asymptotic cumulative emergence, densities of dominant weeds in solaria (common lambsquarters, green foxtail, and large crabgrass) were correlated with weed densities occurring 4 wk after sowing, the typical time for making postemergence weed control decisions. These results indicate that solaria may supplement seedbank-sampling techniques for predicting weed densities in crops.Nomenclature: Common lambsquarters, Chenopodium album L. #3 CHEAL; green foxtail, Setaria viridis (L.) Beauv. # SETVI; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA.Additional index words: Decision making, emergence, postemergence control, seedlings, solarization.Abbreviations: CWD, in-crop weed density; OM, organic matter; PPI, preplant incorporated; PRE, preemergence; SWD, weeds inside solaria; TWD; threshold weed density.