Four field experiments were conducted in 1993 at Prosper and Dallas, TX, to; 1) determine the effects of timing and split applications of nitrogen (N) fertilizer on cotton lint yield and seasonal patterns of petiole tissue nitrate-N (N0(3) -N) concentrations; 2) to examine interactive effects of available soil moisture from subsurface drip irrigation and N fertilizer application on cotton lint yield; and 3) to determine the effects of foliar potassium (K) fertilizer sources and K applications made at 1, 2, 3, and 4 weeks after bloom on lint yield and fiber quality of 10 popular cotton varieties. Nitrogen application significantly increased cotton lint yield 25 to 35 percent compared to unfertilized plots. Sufficient single or split N applications from planting up to first square were equally as effective to correct N deficiencies of rainfed cotton. Applications of N following bloom had a tendency to either increase vegetative growth of cotton plants at the expense of lint yield, or did not become positionally available to plant roots early enough to benefit cotton production. Petiole tissue N0(3) -N tests at first square and first flower growth stages were practical to use, and proved quite accurate for predicting the N needs of cotton. Seasonal moisture levels exceeding 16.2 inch (60% evapotranspiration) and cotton lint yield potential in excess of 435 lb/acre were required for significant lint yield increase with N application. Foliar K application did not significantly increase fiber strength of 10 popular cotton varieties compared to unfertilized plots. However, cotton lint yield response to foliar K has been inconsistent in the Texas Blackland with a 14% yield decrease in 1992, and a 6% yield increase observed in 1993. Variety selection was more important than foliar K applications for high fiber strength of Blackland cotton.