Cotton Growth Variability in Relation to Topography and Soil Physical Properties in the High Plains.

Understanding crop growth variability within field helps to optimize crop input, especially irrigation water allocation. The objective of this study is to identify cotton growth and yield variability under different irrigation rates at different landscape positions with varying topography and soil physiochemical properties. A 290 ha commercially managed field in the Texas High Plains was selected in 2017. Elevation data were collected using a real-time kinematic (RTK) GPS receiver. A digital elevation model (DEM) was obtained from the elevation data. Slope and other terrain attributes were derived from the DEM. Two hundred thirty soil samples with three layers on eight circular transects were collected and analyzed for soil texture, pH, electrical conductivity (EC), total C and N, and surface reflectance. Plant height, number of nodes, leaf area index (LAI) and biomass at different growth stages were collected to characterize cotton growth. Plants grown in areas with steeper slope and sandy textured soil had nonuniform stands and lesser height, while plants growing in less-steep slope and clayey loam soil had more uniform stand and greater height. Number of nodes however was not so significantly different across landscape positions. Preliminary results show that topography and soil physical properties have significant influence on plant growth, with greater plant height, LAI, and biomass in areas with low slope and loamy or clayey soil texture. Results can be used to allocate irrigation water at different landscape positions, for example, concentrating water on more productive areas within the field to improve overall productivity and profitability.