Research

A late July solid-tine spiking treatment of a creeping bentgrass green in Hokkaido, Japan. How’s this for a lede? “Hollow-tine coring and solid-tine spiking practices may not alleviate creeping bentgrass summer decline.

After I wrote the seven part series about soil sampling for turfgrass, I formatted the posts into an easy-to-read 11 page PDF brochure. The take-home message is yes, we’ve been doing it wrong.

Bill Kreuser shared a fascinating update from one of the experiments he is conducting this summer. I wouldn’t have expected to see such a big difference in growth rate with a mowing height difference of 0.

The N-only pot looked pretty good when I showed roots after 184 days. But that same grass grew a lot more, and produced a lot more underground roots and rhizomes, when P and K were added.

Regular readers of this site will remember the grow-in experiment I started on 1 October 2019. I wrote about it in these posts. Fertilizer response at planting Experiment update: fertilizer response at planting

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.