Optimizing Application of Phosphorus and Potassium to Processing Tomatoes under Drip Irrigation
IPNI-2007-CAN-ON28
30 Jan 2009
2008 Annual Interpretive Summary
Optimizing Application of Phosphorus and Potassium to Processing Tomatoes under Drip Irrigation in Ontario, 2008
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, starting in the spring of 2006. Soil test levels in 2008 were higher than in 2007 ... 65 ppm Olsen-P, and 216 ppm ammonium-acetate K.
In 2008, in contrast to previous years, the marketable yield of tomatoes responded to P, but not to K. An optimal rate of 110 lb P2O5/A produced 121 t/A of marketable yield, but nutrient use efficiency was low. Measured as agronomic efficiency, each lb of P2O5 produced 130 lb of additional tomatoes. Recovery efficiency of P by the plant was less than 4%. Phosphorus fertilizer increased vitamin C levels by 12% in 2008, though there was no effect in 2007. Rates of 200 to 350 lb K2O/A caused a slight increase in soluble solids content, though not large enough to compensate for the lower soluble solids under drip irrigation. Lycopene analysis remains to be completed. This project is planned to continue in 2009. This project is demonstrating that high yields of high quality tomatoes can be produced with improved nutrient use efficiency for N, P, and K by using drip irrigation. ON-28