OPTIMIZATION ALGORITHM TO

ii ACKNOWLEDGEMENTS I thank our Lord Jesus Christ for giving me the ability to complete this degree. Your love, faithfulness and guidance have been my instruments for this achievement. I would like to thank my husband, Edwin, and my children, Elaisa and Casiano III, for their love, support and understanding while pursuing this degree. I am also thankful to Raun family, and to my relatives, brothers and sisters in Christ and friends for being supportive and helpful in anyway they can. I am also grateful to the Department of Plant and Soil Sciences for granting me the opportunity t

Effects of Landscape, Soils, and Weather on Yields, Nitrogen Use, and Profitability with Sensor-Based Variable Rate Nitrogen Management in Cotton

Farmers may be reluctant to adopt variable rate nitrogen (VRN) management because of uncertain profits. This study assessed field landscape, soil, and weather effects on optical sensing (OS)-based VRN on cotton (Gossypium hirsutum L.) N rates, yields, and net returns (NRs). Field data were collected from 21 locations in Louisiana, Mississippi, Missouri, and Tennessee, USA, between 2011 and 2014. Data included yields, N rates, and NRs for the farmer practice (FP), OS-based VRN, and OS-based VRN supplemented with other information. Production data were augmented with landscape, soils, and weather data, and ANOVA and logistic regressions were used to identify field conditions where VRN was profitable, provided risk management benefits, and improved N efficiency. Key findings indicate that NRs were improved with VRN by applying additional N on more erodible soils. Higher organic matter soils also benefited from VRN through enhanced yields and NRs. VRN may also have provided risk management benefits by providing a lower probability of NRs below NRs for the FP on soils associated with greater water-holding capacity, higher organic matter levels, or deeper profiles. Results from this study may help identify farm fields with similar characteristics for adoption of VRN management