NITROGEN AND POTASSIUM APPLICATION SCHEDULING EFFECTS ON DRIP-IRRIGATED TOMATO YIELD AND LEAF TISSUE-ANALYSIS

Tomato (Lycopersicon esculentum Mill.) was grown with drip irrigation on an Arredondo fine sand and on an Orangeburg fine sandy loam to eval uate the effect of N and Ii time of application on petiole sap, leaf-I V and -K concentrations, fruit yield, and to determine N and K suffici ency ranges in leaf tissue. On the sandy soil, N-K at 196-112 kg.ha(-1 ) were applied 0%, 40%, or 100% preplant with the remainder applied in 6 or 12 equal or in variable applications in 12 weeks. With the varia ble application rate, most nutrients were applied between weeks 5 and 10 after transplanting. On the sandy loam soil that tested high in K, only N (196 kg.ha(-1)) was applied as above. Petiole sap K concentrati on declined during the season, but was not greatly affected by treatme nt. Petiole NO3-N concentrations decreased during the season from 1100 to 200 mg.L-1, and the decrease was greater with preplant N treatment s. On the sandy soil marketable fruit yields were lowest with 100% pre plant, intermediate with 100% drip applied (no preplant N), and highes t with 40% preplant and 60% drip applied. With 100% drip applied, yiel ds were higher with 12 even applications than with either six even wee kly applications or with 12 variable N and K applications. With 40% pr eplant, timing of application had little effect on yield. On the sandy loam soil in 1993, yields were highest with 100% preplant, intermedia te with 40% preplant and 60% drip applied, and lowest with all N drip applied. In 1994 when excessive rains occurred, yields were similar wi th all preplant and with split N applications. Petiole N concentration was correlated with tomato yield, especially at 10 weeks after transp lanting. The best correlation between sap-N and total yields occurred between 4 and 6 weeks at Gainesville and between 4 and 10 weeks at Qui ncy.