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Abstract
Cotton (Gossypium hirsutum) and corn (Zea mays) are two of the most widely grown row crops in the state of Georgia, so profitable and sustainable production of these two commodities is essential for producers. The objective of the first project of this dissertation research was to assess stand establishment, crop growth and development, and lint yield in response to varying cultivars and seed sources. Findings from this study illustrate the need to utilize well-adapted cultivars but to also be mindful of seed quality to minimize early season risk of stand loss without sacrificing yield potential. Project two evaluated thrips prevalence, plant injury, crop development, and lint yield in response to cultivar (with or without ThryvOn™, a new gene technology for thrips control) and insecticide treatment under high thrips pressure. ThryvOn™ cotton exhibited lower thrips densities and plant injury due to thrips than non-ThryvOn™ cotton, regardless of insecticide treatment. When interactions between cultivar and insecticide were observed, insecticide treatment reduced pest pressure and positively impacted plant growth to a larger extent in non-ThryvOn™ cotton compared to ThryvOn™ cotton. Lint yields were not affected by cultivar or insecticide treatment in either year, despite significant plant injury in the early season. Project three assessed biomass, nutrient uptake, lint yield, and resource use efficiency in cotton grown under two different irrigation treatments, three N application rates, and three MC treatments. Overall, we can conclude that management practices with the potential to alter canopy growth, nutrient uptake, and lint yield also have the potential to influence resource use efficiency. Project four evaluated the effect of irrigation scheduling approach on grain yield and water, nitrogen, and radiation use efficiencies for field corn in southern Georgia. Across both years of the study, soil moisture-based approaches and the UGA checkbook method maximized grain yields, yet among these treatments, only the 60kPa SWT maximized intrinsic nitrogen use efficiency (iNUE), radiation use efficiency (RUE), and irrigation water use efficiency (IWUE). Using this threshold for irrigation scheduling has the greatest potential to maximize yield and profitability for the producer, while also optimizing the intrinsic resource use efficiencies of the crop.