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As harvested tonnage continues to improve for processing tomatoes, the Ontario Tomato Research Institute requested a review of recommended nitrogen rates on three newer varieties. The three-year project was led by John Zandstra who’s in charge of fruit and vegetable cropping systems at the University of Guelph, Ridgetown Campus.
“The recommended nitrogen rates set by the Ontario Ministry of Agriculture, Food and Agribusiness have not been updated in awhile, and we wanted to see what the crop response would be to higher nitrogen rates on these newer varieties,” says Zandstra.
Six different fertilizer treatments were compared on three varieties (C337, H1014 and H3406), grown on loam or clay soil on Ridgetown Campus fields. The treatments ranged from no added nitrogen to currently recommended rates of 140 – 160 lb./ac., and up to more than 300 lb./ac.
The trial ran over three seasons (2023 –2025) and looked at yield response from nitrogen rates but did not include an economic component.
- Overall, tomato yields were higher when fields received more than the recommended rate of 160 lb. /ac. of nitrogen.
- There was no benefit to applying more than 300 lb./ac. of nitrogen, and in some cases yields dropped at these higher rates.
“We found consistently better yields at higher than currently recommended nitrogen rates,” says Zandstra. “This isn’t really a surprise but was good to confirm that we’re on the right track on how much we can push the yields of these newer varieties.”
Read the full research report Tomato nitrogen trial on clay and loam soil types.
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