| Abstract: | Cover crops can suppress weeds and provide ecosystem services during fallow periods. The effects of contrasting cover crop and herbicide systems in corn (Zea mays L.) and grain sorghum (Sorghum bicolor (L). Moench) were evaluated in a three-year study in Burleson County, TX. Cover crops were winter wheat (Triticum aestivum), spring wheat, a rye (Secale cereale) and hairy vetch (Vicia villosa) mix and a mix of triticale (× Triticosecale), oat (Avena sativa), Austrian winter pea (Pisum sativum var. arvense), hairy vetch, and crimson clover (Trifolium incarnatum). Four herbicide systems were evaluated that included increased time between applications compared to pre-emergence only. Spring wheat generally produced more dry matter with more persistent residues than other cover crops. Cover crops increased (p < 0.10) control of grass weeds up to 44 days after planting in sorghum without herbicide applications. Cover crop effects on weed control in corn and sorghum were diminished with herbicide use. While spring wheat reduced plant stands in some years, grain yield was not reduced. Cover crops contributed to small soil carbon increases in a sorghum-corn rotation. Additionally, severe weather impacts sorghum production in Texas, and hail adjustment procedures are decades old. A three-year study measuring the effects of stand reduction by growth stage in sorghum was initiated in Burleson County, TX to evaluate modern sorghum response to stand reduction. Late season yield estimations have not changed from older guidelines. Yield estimations from early growth stage stand reductions could be improved. Regression models were evaluated to optimize yield loss predictions in sorghum with stand loss occurring at various growth stages. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198603 |
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