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A couple weeks ago I was preparing for a seminar in which I discussed Charles Vancouver Piper and the early days of turfgrass science in the United States. I recalled—or quite possibly I misremembered, as I haven’t been able to find it yet—having read some years ago something by Piper about nostrums.

The normal range of calcium (Ca) in irrigation water is 20 to 60 ppm. That comes right from Penn State’s Irrigation water quality guidelines for turfgrass sites. Were you surprised by the previous post that worked out daily Ca use by the grass, and Ca added in irrigation water, to find that irrigation water was supplying 26 times more Ca than the grass was using?

These are some key things I’ve learned after studying soil organic matter (SOM) for a few years. This is about organic matter in the context of playing conditions—how a ball reacts when it hits the surface.

Did you see where soil potassium (K) only went down by 1 ppm after 374 mm (14.7 inches) of rain? In that same comparison of pre- and post-rain samples, the soil calcium (Ca) went down by 26 ppm.

I was in Fukuoka last weekend and enjoyed the mid-winter weather and the seasonal colors of the turf. This is what golf courses in Japan look like in the winter.

The summary so far is this: standard recommendations for turfgrass sampling are to take 12 or more cores from each area and composite them into one sample I’ve been taking 5 cores and compositing them Donohue’s research in Virginia led him to recommend taking 20 subsamples and compositing them The article by Lawrence et al.

Now this series gets interesting. I’ve reviewed what I do, what a Twitter survey says people are doing, what Rutgers and Penn State recommend, and what an intensively sampled lawn in Virginia suggests would be an appropriate number of subsamples to combine in composite samples for turfgrass.

I’d read the soil sampling instructions from Penn State and Rutgers, suggesting a minimum of 12 subsamples be combined as a composite sample for each area. When I give instructions for sampling, I suggest a minimum of 5 subsamples be collected per green (or per area).

I’ve recommended taking at least 5 subsamples per green, for as long as I can remember. That’s less than the 12 to 15 recommended by Rutgers, less than the 12 or more in the Penn State instructions, and way less than the 20 subsamples per composite recommended by Donohue.

There’s an article by Donohue, Evaluation of soil nutrient variability for development of turfgrass soil test sampling methods, that describes results from sampling a 2,000 m2 (21,520 ft2) lawn at the Virginia Tech Turfgrass Center Laboratory.