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*.

*a*is the quantity of an element used by the grass*b*is the quantity of an element that must be kept in the soil to ensure the grass will have access to enough of that element*c*is the quantity of an element that is actually present in the soil

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.

- The MLSN guidelines.
- Climate appraisal forms from PACE Turf with the growth potential equation and lots of other necessary information already embedded in the downloadable spreadsheets.
- A detailed explanation of MLSN.
- The Global Soil Survey.
- MLSN on Facebook.
- Posts tagged Fertilizer on the Asian Turfgrass Center blog.
- I didn’t put a link to this explanation of growth potential in the slides, but it is a fuller explanation of this approach.
- My twitter account is @asianturfgrass.