Yield and Economic Assessments of Fertilizer Nitrogen and Phosphorus for Processing Tomato with Drip Fertigation

Agronomic and economic assessments of response of processing tomato (Lycopersicon Esculentum Mill.) to nutrient application with drip fertigation are essential to optimize soil fertility management that maximizes farmers' profitability in a sustainable manner. A field study was conducted to evaluate the yield and economic responses of drip fertigated processing tomatoes to additions of fertilizer nitrogen (N) and phosphorus (P) from 2003 to 2005. The experiment was arranged in a factorial design with four levels of fertilizer N (0, 120, 240, and 360 kg N ha(-1)) and three levels of fertilizer P (0, 100, and 200 kg P2O5 ha(-1)). Fertilizer N application affected biomass yield of stems and leaves, total and marketable fruit yields, N use efficiency, and N agronomic efficiency. However, neither P application nor the interaction between fertilizer N and P influenced these variables. Nitrogen use efficiency and N agronomic efficiency decreased with increases in fertilizer N rate, with N use efficiency averaging 443 kg kg(-1) and N agronomic efficiency averaging 237 kg kg(-1). Both fruit yields and net economic returns responded quadratically to the fertilizer N rate, with a maximum marketable yield of 127 Mg ha(-1) averaged across the 3 yr. The fertilizer N rates were 271 kg N ha(-1) for the maximum marketable yield and 265 kg N ha(-1) for the optimum economic yield. These values are considerably greater than the current recommendation, due to the largely increased yield with drip fertigation. Fertilizer N should be applied at an increased rate for processing tomatoes with drip fertigation to maximize the economic return.