NITROGEN AND PHOSPHORUS APPLICATION TO PROCESSING
TOMATOES GROWN UNDER DRIP FERTIGATION
T.Q. Zhang, C.S. Tan, K, Liu, and J. Warner
Agriculture and Agri-Food Canada, Harrow, Ontario, N0R 1G0
E-mail: zhangt@agr.gc.ca
Sufficient nutrient and water supplies are vital for processing tomato (Lycopersicon
esculentum Mill.) production. Excessive N and P supplies, however, can cause water
contamination. A 3-yr study was conducted to evaluate agronomic and environmental
consequences of applied fertilizer N and P to processing tomatoes under drip fertigation
in south-western Ontario. The experiment was arranged in a factorial design, with four
rates of fertilizer N ranging from 0 to 360 kg N ha-1 and three rates of fertilizer P ranging
from 0 to 200 kg P2O5 ha-1. The full amount of P and 40% of N were broadcasted and
incorporated into soil prior to transplanting, with the remaining N fertigated. Total and
marketable fruit yields and stover biomass responded quadratically to N rate, but not the
P rate. The optimum N rate for the production of processing tomatoes grown with
fertigation was estimated as 270 kg N ha-1. Fertilizer N applied at rates above the
optimum rate can cause significant increases of post-harvest soil residual NO3-N, which
may increase leaching losses during the non-growing season. Total N uptake was
averaged at 265 kg N ha-1 and total P uptake averaged at 44 kg P ha-1. Nitrogen and P
removals were averaged at 187 kg N ha-1 and 36 kg P ha-1, respectively. The results
demonstrated that with the increases of fruit yield under drip fertigation N application
rate needs to be increased to satisfy the optimum growth under prevailing conditions.