Looking at the clipping volume GvX
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. That is, for almost everywhere in the world, the expected amount of clippings is going to change through the year.
Jason Haines came up with a logical and effective way to standardize this—the Turf GvX which looks at actual growth compared with expected growth.
Jason has suggested that adjusting N and PGR applications through the season to keep the GvX close to 100 has been a great way to keep healthy grass and good playability. He can also favor bentgrass over Poa annua by keeping the GvX below 100, and favor Poa annua over bentgrass by keeping the ratio above 100.
I took a look at this for the warm-season korai greens at Keya GC in 2021.
In the spring as the grass is coming out of dormancy, the GvX is way above one.1
Then from June through to the end of October, the GvX (as a seven day moving average) is always less than 300.
It seems that a value of 100 works pretty well for korai greens too, and for tournament play, a GvX of about 50 would work well.
This is because there is some clipping volume from mowing but the temperatures are so cold that the GP is close to zero. Seeing this type of discrepancy between growth and GP as grass goes in and out of dormancy provides some insight on how the GP model might be adjusted. ↩︎