Nitrogen, potassium, and irrigation management for cotton production on the Texas High Plains

Nitrogen (N) is the most commonly limiting nutrient in cotton ( Gossypium hirsutum L.) production and is important for lint yield and physiological development, but yield response is difficult to predict due to the influence of water and residual soil nitrate‐N (NO 3 − ‐N). The objective of this research was to evaluate how N and potassium (K) fertilization interact with irrigation cultivar to influence N uptake, nitrogen use efficiency, lint yield, and the ability of canopy reflectance indices normalized difference vegetation index (NDVI), and normalized difference red edge to estimate crop performance. The study was conducted in Lubbock, TX, from 2018 to 2021 on a subsurface drip irrigation field. The experimental design was a split‐split‐plot, with irrigation, cultivar, and fertility as main plots and sub plot factors, respectively. Irrigation rates were 30% and 70% of evapotranspiration (ET), fertility included urea‐ammonium nitrate (32‐0‐0) at rates of 17, 85, and 167 kg ha −1 and potassium thiosulfate (0‐0‐25‐17S) applied at 0, 22, and 45 kg ha −1 , and the cotton cultivars were DP 1820 B3XF and DP 1823NR B2XF. Plant N uptake was greater within the 70% ET. Throughout the study, a significant fertilizer × irrigation × cultivar interaction influenced both plant N uptake and lint yield. These results indicate that the impact of fertilizer on yield is directly contingent upon irrigation levels and varies by cultivar. Additionally, NDVI proved to be an unreliable predictor of lint yield due to a weak relationship.