Optimizing Application of Phosphorus and Potassium to Processing Tomatoes under Drip Irrigation
IPNI-2007-CAN-ON28
18 Feb 2010
2009 Annual Interpretive Summary
Optimizing Application of Phosphorus and Potassium to Processing Tomatoes under Drip Irrigation in Ontario, 2009
Recent research has indicated that processing tomatoes require higher rates of N when grown with fertigation. The objective of this research is to determine optimum rates of P and K for the higher yields obtained in this production system. Four rates of P, from 0 to 180 lb P2O5/A, were applied in a factorial combination with four rates of K from 0 to 640 lb K2O/A, in a drip-irrigated system fertilized with N at 240 lb/A. Soil test levels for P and K varied from year to year, but were generally high, representative of those of typical producer fields.
From 2006 to 2009, marketable yield responded to P and K, each in 2 of the 4 years. Yields were boosted 5% and 11% by P at soil test P levels of 37 to 65 ppm. Potassium increased soluble solids content and also raised marketable yields by 10% and 12% at soil test K levels of 160 to 233 ppm. Vitamin C was increased 1 year in 3 by P, but not by K. Neither P nor K influenced lycopene concentrations in any of the 4 years. The positive yield and quality impacts measured at these relatively high soil test levels support current nutrient use practices of progressive growers, but opportunity to improve fertilizer uptake efficiency remains, particularly for P. The field research was completed in the 2009 growing season, and the project completion is planned for early 2010. ON-28