How to measure and reduce organic matter on greens

Alistair Dunsmuir
By Alistair Dunsmuir March 18, 2012 14:05

How to measure and reduce organic matter on greens

Overseeding on golf greens – is it a waste of time? Yes … unless you create the right environment for long-term establishment!

Well, let’s start with the wrong environment!

Costing anything from around £90 per bag for a standard fescue / bent to £400 and above for top of the range, all bent overseeding is an expensive business. How can you be sure you’re not chucking this money straight down the drain?

If overseeding with bent is attempted into greens which have a high organic matter content, there is a fair chance that the seed will germinate given ideal soil temperatures and moisture levels. You can get seed to germinate pretty much anywhere, (we’ve had bent seed springing up on concrete, tarmac, on our trailers and in the back of our vans!) so germination isn’t the issue – it’s all about establishment. On greens with high organic matter the seed will soon be swamped by less desirable grasses and organic matter, and the time, effort and money spent will all have been for nothing.

Over the last 50 years of greenkeeping, organic matter has remained the number one problem / issue on golf greens all over the world, not only for overseeding, but for spongy, slow greens which are far more prone to disease.

Organic matter poses the single greatest threat to successful overseeding. Too much organic matter prevents the seed from making good contact with the soil. If seeds do manage to germinate, the poor air flow will exacerbate seedling diseases. Seeds growing in thatch will not be able to put down sufficient roots and will quickly burn off under any drought stress. In actual fact, it’s a double whammy, as if you then have to water the greens to keep the seeds alive, the water gets clogged up in the thatch layer, depriving the seeds of any oxygen and they just rot off. It’s like trying to build a house with no foundation; it will work initially but just won’t last. Therefore, reducing organic matter is an essential part of the overseeding process.

So how do you create the right environment?

The Sports Turf Research Institute (STRI) carried out organic matter research with trials involving over 600 golf greens throughout the UK and highlighted the following facts:

• Greens with an organic matter content of seven per cent or below had a very large percentage of finer grasses, that is bent or fescue.

• Greens with an organic matter content at ten per cent or above (which is surprisingly the norm on most courses) were found to be predominantly annual meadow grass.

So, although it’s not rocket science, (thank goodness) it is proven scientific research. I know that the people greenkeepers really have to get the message across to are golf club members. This research is widely available; and I’m sure if you contact your local agronomist or the STRI themselves, or show them this article, that could help.

The most important thing to take from this article is that you need to measure the amount of organic matter in the soil profile – you need a base line to work from!

To measure the organic matter, you need to take a core sample and send it off to an accredited lab, such as the STRI or European Turfgrass Laboratories. The test used is ‘Loss of Ignition’, which involves drying out the core sample, weighing it and then burning off the organic matter. The sample is then weighed again and the difference in weight adds up to the amount of organic matter in the sample. It’s imperative that the lab tests the sample in sections, that is in the top 0-20mm, 20-40mm and 40–60mm. This is so that you can ascertain where the problems are. Most labs will do this automatically, but it’s always worth checking. The majority of organic matter is typically found in the top 25mm. However, any issues below this depth must not be ignored either.

The advantage then of measuring the organic matter is that it is a scientific formula or mathematic equation which can be understood by everyone involved, from greenkeepers to greens’ committees! It’s so much easier to work with something concrete which has been thoroughly researched and is not a matter of myth, speculation or opinion.

Now you can plan your attack!

With this factual evidence showing the percentage of organic matter already in the greens, you can take it to the powers that be and show them what percentage you need to aim for. As you can see from the bullet points earlier, the optimum target level of organic matter in the top 0-20mm is between five and seven per cent or less. If your samples show that organic matter is present at the 20 to 40mm and 40 to 60mm depths, then the target for these areas is four per cent.

By using this testing procedure regularly once a year, greenkeepers can show exactly how effectively their organic matter reduction programme is working. At a time when clubs are struggling to save money and attract members, what better way to do it than by offering superb fast, firm, smooth and disease free greens? There are other advantages to the reduction of organic matter too, including using less water, less fertiliser and less fungicide, because lower organic matter means less disease. What a result!

Can it be done? Absolutely! But can it be done quickly? Yes!

If you have good organic matter levels below seven per cent, virtually all machines used for overseeding are good, such as drill / dimple / disc seeders, micro tiners and sarrel rollers; there’s a lot of choice.

However, if the organic matter is high, you will need to remove and replace as much of the surface as possible. The STRI carried out research comparing hollow tining and micro tining followed by top dressing and deep scarifying without back-filling. The machine which came out tops was the Graden Contour Sand Injection … oops, sorry, I know that’s my machine, but it’s the truth! In the trials, this machine removed and replaced up to 10 per cent of the surface in one pass and reduced the organic matter by 15 per cent at the same time.

Over a timescale of two years the organic matter was reduced by 60 per cent, which is incredible when you think only a few years ago, if organic matter was reduced by three or four per cent per year, that was deemed to be successful.

The beauty of the Graden process is that whilst removing vast quantities of organic matter, it simultaneously creates the perfect growth medium by backfilling the grooves with kiln-dried sand and places the seed directly into the sand-filled grooves, virtually guaranteeing a total success rate for both germination and far more importantly, establishment, which is what it’s all about. The process is incredibly quick, given that this machine achieves every goal in just one operation. We allow two days for 18 greens and a putting green, and the greens are back in play immediately after clear up.

My interest was first sparked in all this by an article on USGA greens’ research by Chris Hartwiger and Patrick O’Brien. This showed that to maintain greens at tournament level you need to remove and replace between 15 and 30 per cent of the surface every year. I soon realised that most clubs in the UK, Europe and beyond (but not quite infinity!) only remove and replace between eight and ten per cent at the very most, which is why overseeeding is often not as successful as it should be.

In the contracting side of my business, up until I read their article, I too used to go along quite happily overseeding twice a year, the same as everyone else, and just accepted the results. However, since I read the article, it has become a subject I am absolutely passionate about and which I really believe I can help people with, especially now it is backed up with the results of the research.

As with most things, there will be people who agree and people who disagree with what I’ve said. All I can say is that what I’ve learned is not only based on 40 years’ experience of greenkeeping and contracting on golf courses throughout the world, but also from talking to agronomists and greenkeepers. On my travels to different countries to look at, or work on, golf courses, there’s one common denominator.  When you go to a course that’s got low organic matter, the greens are always firm, fast and, more importantly, smooth.

This is just a short article (believe it or not) and I haven’t even mentioned drainage, fertilising, regular top-dressing and so on. I welcome all feedback, especially from those of you who are not yet convinced and I’m more than happy to talk (for hours!) to discuss the various processes of successful overseeding.  But please, if there’s one thing to take from this article – get your organic matter measured properly!

Keith Kensett is a director at R&K Kensett

Alistair Dunsmuir
By Alistair Dunsmuir March 18, 2012 14:05
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1 Comment

  1. (@GCM_mag) (@GCM_mag) March 18, 14:06

    Tips on how to reduce organic matter in golf greens:

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