What about PGRs?

And the Growth Ratio equation

One of the follow-ups I wanted to write to yesterday’s post was in regard to using plant growth regulators (PGRs) and how it factors into using growth ratio to inform nitrogen. Then, I got this question from a reader: “do growth regulators factor in separately or is all the same equation?”

There are many people who know much more about PGRs than I do. My experience is very much anecdotal. I did spend one full season not using PGRs on putting surfaces, I was curious and wanted to see what it was like. I’m glad I did it, because now I know what it’s like not to use them. Based on my anecdotal PGR experience, here are some things I’m fairly certain of:

• They improve the health of the plants.

• Plants require less nitrogen when using PGRs.

• The plants grow tighter and form a better surface. I refer to this as canopy architecture.

• The grass grows less.

• The best results come from using PGRs consistently. 

Some of these things, maybe all of them are obvious, but still worth noting. I like what I believe I get from PGRs, thus I have no plans to change my approach to using them.

We reapply PGRs according to GDDs; many of you probably do the same, and you’ll know this results in varied application intervals throughout the season. We use the Greenkeeper app to track our PGR applications and it models the percentage of growth regulation. This number is recorded in my spreadsheet, and can be seen in the chart below. I aim to keep the regulation (according to the Greenkeeper model) as consistent as possible. 

When it comes to the equation I wrote about in my last post, PGRs are going to be a factor in clipping volume, which is going to be a factor in the growth ratio and thus help to inform the amount of nitrogen being applied. So to answer the question above, PGR use is sort of baked into the formula and I don’t factor them separately.