Processing tomato nitrogen utilization and soil residual nitrogen as influenced by nitrogen and phosphorus additions with drip-fertigation

Timely sufficient water supply through drip irrigation or fertigation may increase nutrient demand of processing tomato (Lycopersicon esculentum Mill.) due to increases in yield production. However, excessive nutrient application could result in crop luxury uptake and enrichment in soil profile, especially mineral N, with the latter potentially causing environmental concerns. A study was conducted to determine the responses of crop N utilization and post-harvest soil profile mineral N to fertilizer N and P additions under drip fertigated processing tomato in sandy loam soils from 2003 to 2005. Across the 3 yr, both fruit N removal and plant total N uptake were either linearly or quadratically related to fertilizer N rate, with 187 kg N ha -1 of fruit removal and 268 kg N ha -1 of plant total N uptake obtained at the maximum yield. Nitrogen uptake efficiency and apparent N recovery decreased linearly with increases in N rate. At the maximum fruit yield, N uptake efficiency was 0.71, and apparent N recovery was 51.7%. Post-harvest soil profile (0-100 cm) mineral N increased with increases in fertilizer N rate, and at greater rates with fertilizer N applied at rates above those required for maximum fruit yield production. Of the soil residual N, 62% remained in the top 40-cm soil layer. Addition of fertilizer P had no effects on plant N uptake, N uptake efficiency and post-harvest mineral N in soil profile, presumably due to the high levels of soil test P. Beneficial management practices need to be developed to prevent soil N losses during the non-growing season following production of processing tomato with drip fertigation. © Soil Science Society of America.