Within‐Season Growth and Spectral Reflectance of Cotton and their Relation to Lint Yield

Within‐season measurements of cotton (Gossypium hirsutum L.) growth and development in response to moisture deficit stress can provide insight into how management practices impact plant health and yield. The objectives were to investigate responses of leaf area index (LAI), normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and crop water stress index (CWSI) and their relation to the lint yield of four cotton cultivars (PHY499, DP1044, PHY375, and FM9170) grown under various irrigation levels for two consecutive growing seasons at Chillicothe, TX. Plants exposed to water stress showed significant LAI, NDVI, and NDWI decrease and CWSI increase compared with well‐watered plants. The NDVI reached a plateau value of 0.89 at 82 d after planting (DAP), while NDWI increased steadily to the end of the growing seasons for the high irrigation level. The high irrigation level had the greatest lint yield of 1670 and 1846 kg ha−1 in 2013 and 2014, respectively. Fiber length, strength, and micronaire showed significant differences among irrigation levels. Compared with dryland, an average 8% increase in fiber length and strength and 10% decrease in micronaire were observed by the high irrigation level. High positive correlations of LAI, NDVI, and NDWI with lint yield were observed in both years. The CWSI differentiated low vs. high irrigated plants and was negatively correlated with lint yield. The results indicated that these measurements at different growth stages are useful to detect growth and water status for cotton in the semiarid Texas Rolling Plains.