For my subscribers worldwide, here is a “not google translated” text describing the method and work procedure I use for measuring organic material in sand based golf greens.
I start measuring moisture level after irrigation at 30 points with short probes (shorter than 75 mm) on a green to see how much moisture vary in mat layer. Volumetric moisture content is strongly correlated to variation of organic material which vary about 10% on a good green in mat layer.
If moisture vary less than 20% I take seven samples, no less no matter how small portion of the surface I will evaluate. If moisture vary more than 20% I take ten samples or simply chose to recommend a visual study of profile to find the reason for variation. Micah Woods at Asian Turfgrass Center use five samples #OM246 and he might be correct but so far I experience five samples a bit too varying. Micah also analyse nutrients for MLSN, so OM246 is more complete, kind of one-stop-shopping for green analysis.
If possible I prepare every tube from the nursery green to exchange the sample with a plugg so I leave no marks on the green. Or I move turf from the edge of the green to the samples positions.
Samples are taken with a 32 mm tube to the depth of interest, often 50 mm is enough, not much happen under 50 mm just slowly decrease to 1% organic material which is not very interesting level. It is the mat layer we need to follow and the top 25 mm is the operating zone possible to influence in short time. The seven samples are individually analysed at 0-25 mm and the samples are pooled for lower levels to get a mean based on seven positions.
I recommend at least three greens are samples three time per year. Right after opening in spring, just before the period in summer with most golfers playing and in autumn before cultivation or heavy topdress dressing is performed. This will give information about what comes out of the winter (it could vary a lot) what levels of OM are when greens are the best, and finally a reflection of what maintenance is required to get back to preferred level.
When I studied two green every month in 2021 in south Sweden it looks like this:
The cost for 72 samples is about 1500 EUR per year. Buying the equipment for loss on ignition of 24 samples each time is about 4000 EUR and operating cost is only electricity. Brake even within three years. Add dry sieving equipment to have control of sand used is 3000 EUR. Chemical and pathology analysis is not for DIY if accuracy is required, but for indication there is reasonable priced equipement.
I have indicated the 95% confidence interval, calculated by 1,96 x standard deviation /sqrt(#samples). Another common way is to calculate cv: the standard deviation/mean. There is also something called a paried t-test which calculate the probability that two means are from same distribution.
Samples are to be undisturbed and verdure should not be removed. No grounding or sieving as lab do measuring Soli Organic Matter in agricultural or horticulture soils.
The samples are cut in 25 mm sections and put in a crucible to dry in 105 C for five hours. Weight crucibles with content with a 10-mg scale. 24 hours is not needed. Burning in muffle owen for one hour in 550 C. Measure again before cooling totally (or will attract moisture) and you will not need a desiccator. All this is depending on very low levels of clay in the sample. But the mat layer in golf greens got bigger problem than organic material if they got clay in the sand to the extent it will effect crystal water and carbonate leves etc, which will be create invalid numbers of Loss on Ignition.
That’s it! No rocket science, just do it.