Phosphorus and potassium application to processing tomatoes grown with drip irrigation.

Balanced nutrient supply can increase processing tomato productivity, which may be further enhanced with drip irrigation. An experiment was conducted to determine the responses of yield and quality of processing tomato (Solanum lycopersicum) to fertilizer P and K and drip irrigation in accordance with the newly developed N rate in Ontario, Canada. Drip irrigation substantially increased marketable fruit yield and fruit size, and decreased green fruit yield at harvest, compared with the non-irrigation treatment. Optimum combination of fertilizer P and K increased total fruit yield. Fruit soluble solids content was reduced with drip irrigation, but the reduction was compensated to some extent by yield improvement and K addition. Drip irrigation increased N and P removals by 29 and 38%, respectively, compared with non-drip irrigation. Increased fertilizer K application decreased soil residual nitrate-N when drip irrigation was not applied, while drip irrigation reduced residual NO₃-N in 0-100 cm soil profile. The results indicated that drip irrigation in combination with fertilizer K application can make the reduction of N pollution potential possible, while producing high yield of processing tomatoes with improved quality.