Dr. Barry Shelp
University of Guelph
Regardless of the irrigation system used in greenhouse floricultural operations, nutrient delivery should be optimized so that a lower level of fertilizer is used over the crop cycle, thereby minimizing fertilizer costs and environmental impacts. This novel and innovative approach calls for a constant lower level of nutrients to be delivered during vegetative growth only, and this lower level was optimized so that reproductive growth was primarily sustained by the mobilization of previously-acquired nutrients, rather than current supply from the root system.
A combination of research and commercial greenhouse trials was conducted on the delivery of nitrogen and phosphorus, the most important environmental contaminants, as well as sulphur and potassium, measuring commercial yields, constructing nutrient budgets as a function of crop development, and assessing plant nutrient status using a mix of leaf analysis and visual diagnosis. With these nutrients, we found that the supply over the crop cycle can be reduced by as much as 75- 87.5% compared to the current industry standards.