ABSTRACT

Four field experiments were conducted at Prosper, Powell, and Dallas, Texas to; 1) determine the effects of timing and split applications of nitrogen (N) on cotton lint yield and seasonal patterns of petiole tissue nitrate-N (NO,-N); 2) determine the effects of N, phosphorus (P), potassium (K), zinc (Zn), sulfur (S), calcium (Ca), magnesium (Mg), and boron (B) on cotton lint yield and fiber quality; and 3) determine seasonal daily water requirements for maximum cotton lint yield in the Texas Blackland using supplemental drip irrigation. Of all the fertilizer nutrients applied, only N significantly increased cotton lint yield (34%) and fiber strength (4% compared to unfertilized plots). Conventional interpretation of preplant soil test values would predict no response to P, K, Zn, S, Ca, Mg, and B as was observed. Variety selection was far more important than K applications for increasing cotton fiber strength. Though additional work is needed, the cotton petiole NO₃-N tissue tests at first square and first flower growth stages were practical to use and proved quite accurate in predicting the N needs of cotton. Maximum lint yields resulted when total seasonal water ranged from about 20 to 25 inches. Maximum daily water requirements occurred from late June through early August at peak bloom stage of growth. Drip irrigation of 1 inch water/week during this period of peak water use resulted in maximum cotton lint yield.