Considerations for fine-tuning your fertilizer program

How do you typically fertilize floriculture crops in your greenhouse?  Based on how the plant performs? Maybe based on recommendations from your consultant or supplier?  Do you do it the way it’s always been done?  Do you know why it was always done that way?

We know from a few studies that floriculture crops are often over-fertilized.  While this may not result in any harm to the plant, fertilizer is often a significant cost of production for you!  A few studies have also indicated that high nitrogen levels might contribute to higher pest populations in the greenhouse.  The extra nitrogen is transported through the plant and is available for feeding; whether or not it makes the plant tastier is up for debate.

So, higher nitrogen levels may not be affecting your crop but higher pest populations require more pest management inputs (like biological control agents and/or pesticides) and increase the likelihood for crop losses.

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Plant quality at reduced fertilizer levels in spring bedding plants.

Last year, we ran a small study on reducing fertilizer levels in five common spring bedding plants produced in Ontario.  The goal was to see if we could produce the same quality plant using less fertilizer than was typically applied.  Our results showed that a reduction to 150ppm of Nitrogen lead to an increase in plant biomass (dry weight) without any difference from the high Nitrogen treatments in time to flower, or overall size of the plant (height and canopy spread) (we used a 20-8-20 mix).  This small reduction is an easy one to try out in your own operation if you are thinking ahead to spring 2018.

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A look at our current trial looking at the link between fertilizer and pest pressure levels in potted chrysanthemums and gerbera.

This year, Sarah and I have been working together to see if lowering fertilizer levels in potted chrysanthemum and gerbera crops will lead to a reduction in pest pressure without a reduction in quality. Throughout the fall we have been collecting data on plant growth and development (height, canopy size, weight and time to flower) as well as pest pressure levels.  The experiment is still underway, so we don’t have final results to share just yet, but overall there are no differences in time to flower or flower height in gerberas, little difference in the mum canopy height and size (after pinching) and no signs of deficiencies in either crop at rates of 100, 200 and 300ppm of Nitrogen (we used a 17-5-17 mix with micronutrients).  Look for more comprehensive results later this fall when we wrap this study up.

Being more efficient with plant inputs is an area where growers can always improve.  Think about your own operation and where you can make small adjustments in your fertilizer program.  A trial of different rates, similar to the ones highlighted here are easy to setup.  Take advantage of resources available to you to make it happen!  Attend our “Doing Research in your own Greenhouse” workshop this Thursday at the Canadian Greenhouse Conference, or stop by the booth to see some plants from our trial this fall.

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