Cotton Yield, Fiber Quality, Water Use Efficiency, and Spectral Reflectance Responses to Irrigation and Tillage Management in the Texas Rolling Plains.

In the semi-arid Texas Rolling Plains, the growth and yield of cotton (Gossypium hirsutum L.) is driven by the amount of water available to the crop through irrigation and precipitation.  A field study was conducted in 2012 and 2013 at Chillicothe, TX, to investigate the growth, yield, water use efficiency (WUE), and spectral reflectance responses of cotton under different irrigation and tillage treatments. A split-split plot design with three replications was used with irrigation as the main plot (dryland, 45% evapotranspiration replacement, 90% evapotranspiration replacement, and irrigation based on a remote sensing method developed by researchers in the current study), tillage (conventional and minimum) as sub plot, and varieties (PHY499, DP1044, PHY375, and FM9170) as sub-sub plot. Plant height, lint yield, WUE, and fiber quality were significantly affected by irrigation and irrigation by variety interaction. Increasing irrigation level resulted in a linear increase in lint yield and WUE. The irrigation by variety interaction showed that the 90% evapotranspiration (ET) replacement treatment involving PHY375 produced the greatest lint yield and WUE. Tillage did not significant affect lint yield, WUE, and fiber quality. Increasing irrigation water amounts resulted in a linear increase in fiber length and strength, and a linear decrease in fiber micronaire. Vegetation indices calculated using spectral reflectance measurements included the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI). In the current study, NDWI performed better than NDVI. We suggested further investigation on using NDWI for irrigation management for cotton in the Texas Rolling Plains.