# Chapter 4 Units of measurement

## 4.1 Note about units

You’ll find various units of volume in this book. My first serious interest in this topic began at Keya GC in Fukuoka in 2013. At that time, I was thinking, and writing about clipping volume, in terms of liters per green.

That’s fine for a single location; if one knows the green sizes and what a normal or target clippin volume is for a particular green, then that is the easiest way to think about it. In fact, I still think about it this way today, but I don’t communicate it that way anymore. That’s because there are different green sizes, or fairway sizes, or portions of a sports field, or lawn sizes, or whatever one is measuring. For communication about clipping volume to people at another property, or to estimate a dry harvest yield, it is necessary to express the volume in terms of area.

In Japan it is common to express this in terms of liters collected per 100 m^{2} (L/100 m^{2}).^{5} This measure works great for monthly totals. It would be common to have a monthly clipping volume from putting greens of 30 to 120 L/100 m^{2}.

For daily clipping volume, however, one ends up using a lot of decimal points when expressing in these units. When I wrote a report about this in 2017, this chart reproduced in Appendix A shows a median clipping volume of 1.2 L/100 m^{2} and 50% of the measurements in a range from 0.67 to 2.2 L/100 m^{2}. It’s not ideal to try to express the clipping volume and be using so many decimal points. It may be 1.2 today, 0.9 tomorrow, 0.8 the next day, skip a day of mowing because of rain, and then get 1.7.

This past winter I started expressing daily totals in units of mL/m^{2} which I much prefer, as explained in the next section.

And as for this book? Well, it is a work in progress. I’m going to convert all the units and charts to the units I’m using now. But for now, I’m publishing what I have.

## 4.2 Something new^{6}

First, the new. I am going to start using a standard unit of mL/m^{2} to express the clipping volume. This is milliliters per square meter. I have previously used units of L/100 m^{2}. This is an easy change to make. 1 L/100 m^{2} is 10 mL/m^{2}.

Why the change? Because this gives a number for almost all measurements that will be between 0 and 100. Vigorously growing turf may be from 20 to 50 mL/m^{2}. Haven’t mown for a few days? You may get more than 50 mL/m^{2}. Under tournament conditions, one might have less than 10 mL/m^{2} from a double cut of the surfaces. Using a unit on a scale from 0 to 100 is easier because it avoids decimal points. And it expresses the volume per square meter, which is the base area unit I prefer.

When I was in graduate school, I read a paper (Monteith 1984) by John Monteith (https://en.wikipedia.org/wiki/John_Monteith)—you’ll recognize that name from the “Penman-Monteith” equation for evapotranspiration—entitled
*Consistency and convenience in the choice of units for agricultural science*. Here’s his advice:

“How should an appropriate multiple or sub-multiple of a unit be chosen? When repeated measurements of a quantity are to be reported, it is worth looking carefully for a unit which will avoid the frequent quotation of unnecessary zeros or decimal points. For example, the mean weight of a cereal grain should obviously be reported as 38.2 mg rather than 0.0382 g or 38200 μg. In general, when a quantity is quoted to two or more significant figures, the choice of unit should preferably allow its numerical component to fall between 1 and 100; but when only one significant figure is available, it should normally lie between 1 and 10.”

I try to work with units that fall in that range, and I intend to start doing so in my discussion of clipping volume.

### References

Monteith, J.L. 1984. “Consistency and Convenience in the Choice of Units for Agricultural Science.” *Experimental Agriculture* 20: 105–17. https://doi.org/https://doi.org/10.1017/S0014479700000946.

The unit of L/100 m

^{2}is roughly equivalent to quarts/1000 ft^{2}.↩This is from a blog post in March 2018 (https://www.asianturfgrass.com/2018-03-25-clipping-volume-green-speed-and-units/), in which I explained that I would start expressing clipping volume in units of mL/m

^{2}rather than the unit of L/100 m^{2}that I had used previously.↩