This is the handout for a presentation on this topic at the Ontario Golf Superintendents Association conference. It includes the presentation slides and links to additional information.
These are the presentation slides on slideshare. For a PDF version of the slides, download from Dropbox.
This is another attempt to explain nutrient use and requirements for turfgrass. To browse other presentations that looked at a similar topic, see 4 versions of the same topic.
In the presentation, I explain how I go about answering the two important questions every turfgrass manager should have about fertilizer. First, is this element required as fertilizer, and second, how much of it should be applied? I show how these questions can be answered by estimating three quantities, which today I called a, b, and c.
It becomes apparent that a + b is the quantity that we need to have, and c is the amount that we actually do have. It follows that the amount of an element to apply as fertilizer is the result of a + b - c, if we can only get good estimates of a, b, and c.
The answers for b and c are easy; these correspond to the soil test interpretation guidelines that we work with – I recommend the MLSN guidelines – and the amount of an element measured by the soil test, respectively. It turns out to be straightforward to get a reasonable estimate of a also, by considering that the maximum quantity of nutrients harvested will be less than the quantity of N supplied. This approach is based on the growth potential model of PACE Turf.
Examples are shown for Toronto, Ottawa, and Vancouver.