growth potential

For any day in the year, one can calculate the cool-season grass growth potential (GPC3) and the warm-season grass growth potential (GPC4). These growth potential functions take the average air temperature as the input and return a GP value on a scale of 0 to 1, or 0 to 100% if you prefer.

This note below, about the temperature-based turfgrass growth potential (GP), has been sitting in my blog_posts.org1 file for a while now, as one of those topics to write about sometime. When I read the note I jotted down when I created this entry, I realized I wouldn’t have to do much to turn this into a blog post.

I’ve been recommending the growth ratio as a way to check the observed (measured) growth of the grass at any particular time of year. The clipping volume on its own tells you how much the grass is actually growing.

This is a common question. I heard another one recently, too. “How big of a bucket should I get to measure clipping volume?” I like to answer these questions by looking at the site-specific conditions.

The temperature-based turfgrass growth potential (GP) is a utility function that rescales the temperatures that the grass is growing in. Rather than the temperature scale, the GP is a unitless scale from 0 to 1 (or from 0 to 100%) that expresses how close the average air temperature is to the optimum temperature for shoot growth.

I use the turfgrass growth potential (GP) all the time. I make use of the GP for all kinds of things, like predicting sand topdressing amounts, comparing locations, predicting nutrient use, checking overseeding dates, estimating mowing requirements, and many more.

I’ve been asked about the variance in PACE Turf’s growth potential (GP) equation. The variance adjusts the shape of the curve, as the chart above shows. With a lower variance, the GP drops quickly as t moves away from to.

I often express the temperature-based growth potential (GP) as a number between 0 and 1. That is, I don’t multiply GP by 100 to express it as a percentage. One advantage of keeping the GP on the scale of 0 to 1 is easy multiplication.

This can seem a bit abstract, the whole growth ratio thing. In this post, I go step-by-step through the reasoning behind this, and explain exactly which problem this solves. There’s a common question that people have when they start measuring the exact amount of clipping volume.

A question came up about optimum clipping volume and whether that quantity of clippings changes by season. That amount must change for any location at which there are seasonal changes in the weather.