Organic matter v material

Added on December 22nd, 2015 by Lorne Smith
Posted in General, Greenkeeping

Organic matter v organic material


Travelling around GB&I and visiting golf courses as an amateur player while also talking to greenkeepers about what they are trying to do, I pick up the sentiment that ‘all-year-round firmness’ in greens is becoming a major objective – Hoorah!

FineGolf is not suggesting it has all the answers to the complex question of achieving all-year-round firmness, which continues to baffle most of the experts but we believe it is worth trying to identify from an independent viewpoint what are the issues with the different approaches.

Digging a little deeper with regular reading of greenkeeping monthly magazines where grass consultants write articles there does seem to be an increasing emphasis of trying to achieve this ‘firmness’ with a the policy of

top-dressing greens with tons of expensive pure sand.


Perhaps this is one of the reasons that one of The R&A’s “Golf Course 2030” funded projects, recognising that the best washed sand is running out from over-use, new methods of resourcing this product is felt to be needed.

Pure sand topdressing apparently not only smooths the greens for better putting but it also, in chemical greenkeeping parlance, “dilutes the thatch layer” and so firms even annual meadow grass (Poa annua) greens.

thatch, jim arthur, fescues,

High thatch rootzone

‘Thatch’ is a combination of soft cellulose and woody lignin that results from dead grass and roots and other ‘organic material’, such as leaf stalks, which reside in the rootzone, just below the living grass.

In conservation greenkeeping, the equal balance of good microbes, bacteria and fungi in the ‘organic matter’, or humus, within the soil around grass roots, ensures the successful breakdown and degradation of the dead thatch (organic material), turning it back into nutrients for the drought-resistant, deep rooted fine perennial grasses (fescues and browntop bents). This process requires good aeration and the grass being cut at above 4mm so the natural plant food-chain grass system remains friable and drains well, which the perennial fine grasses love and stay disease free.

In chemical controlled greenkeeping however, the natural nutrient uptake is swamped and overridden by inorganic fertilisers and the weed grasses, primarily annual meadow grass (Poa annua), cut below 4mm (some greens being cropped as low as 1.75mm) become stressed, needing extra water and fertiliser to survive. In addition, the annual weed grass grows quicker dosed with fertiliser and becomes prone to excessive fungal disease and more thatch build-up.

If this thatch layer (organic material) becomes too thick it is either too soft and mushy, holding excess moisture or becomes the very opposite, creating a barrier to moisture reaching the shallow weed grass roots. (Water management products like wetting agents ameliorate these problems in the short term but fail to solve the underlying thick thatch problem).

Therefore thatch build-up needs to be controlled if the objective of ‘all-year-round firmness’ is to be achieved.

Everybody desires this outcome apart from the diehard 2mm Poa brigade greenkeepers with high input budgets who want to produce soft ‘target-golf’ greens.


For the majority of greenkeepers this vital goal of controlling the thatch is delivered in one, or more, of three ways:

1)     Mechanically – using machinery like a ‘Graden’ or ‘hollow coring’ with all the concomitant disturbance to golfers playability if undertaken during the summer season when the growing grass recovers quicker.




2)     Top-dressing – diluting the thatch layer with many tons of pure sand, which runs the risk of burying a problem as an impermeable layer, restricting aeration, draining and deep root growth.




3)     Increasing the microbial and fungal activity to naturally convert the thatch layer (organic material) to humus (organic matter) and acids that slowly feed the continually evolving natural fine grass food chain. A healthy balanced soil is created with the humus giving a medium for a good balance of bacteria and fungi to thrive and do their work. This is an aspect of the Jim Arthur method of conservation greenkeeping, while the use of ‘Compost Teas’ is one way of boosting this activity.








A side effect of using pure sand top-dressing and hollow-coring infill is that this action creates the perfect inert environment into which weed grass (Poa anuua) can invade. It enjoys an artificially high fertilised environment containing a high bacteria and low fungi balance. Pure sand dressings also increase the risk of poor moisture retention within the rootzone and can place unwelcome high demands on irrigation in dry parts of the country.

Mycorrhizae, Mycorrhizal

Mycorrhizae around grass roots

The soil biology one seeks is one where mycorrhizal fungi (that only attaches to perennial fine grass roots rather than annual grass roots) helps extend the deep rooting system of fine grasses and thereby their natural take-up of nutrients, while good microbial activity boosts the natural defences of fine grasses to disease.

So it is the creation of ‘organic material’ not ‘organic matter’ that is part of the larger problem of lack of firmness and if the two similar phrases continue to be mixed up by advisors to greenkeepers, the solution to how to move from soft weed grass greens to firm fine grass greens will be further confused.

The science of soil biology in golf has become better understood through research conducted at many universities and the technology developed by Symbio in recent years, since Jim Arthur died in 2005. To promote further interest in this area FineGolf has hosted some articles by Martin Ward the founder of Symbio who developed the compost teas product that adds microbes and fungi to the soil.

At the same time we note that the STRI, the largest agronomic service company, who earn considerable income from hosting grass trials for all sorts of companies and providing laboratory soil analysis to golf clubs with weed or fine grass greens, don’t yet seem convinced of the proof of the efficacy of compost teas.  The STRI have also been strongly in favour in recent years of the use of pure inert sand as topdressing.

jim arthur,

Jim Arthur at Hollinwell (Notts GC))

Perhaps it is useful to return to Jim Arthur and his instinctive understanding of conservation greenkeeping which he saw as much an art as a science and who continues to give the simple non-chemical way forward through his protege Gordon Irvine. He was happy with links courses using top spit sand and seaweed mixed, as top-dressing, while advising use of 70/30 sand/fensoil as a replacement top dressing for courses using high silt clay content mixed with sand.

The provision of some ‘organic matter’ within the rootzone where healthy microbes and fungi can live in competition against the pathogens that thrive in high fertilised environments that produce disease, has been proven many times to be a good policy for the encouragement of fine grasses over annual meadow grasses (Poa annua).

However, as in all healthy activity there is seldom one solution that fits all and the correct answer depends on the particulars of the specific site.




Practical Greenkeeping, Jim Arthur

Practical Greenkeeping by Jim Arthur

FineGolf continues to recommend that golf clubs do not trust the snake-oil salesmen of the high input fertiliser and pesticide brigade but rather to check out your problems and solutions by reference to Jim Arthur’s bible of conservation greenkeeping ‘Practical greenkeeping’.

If a golf club is contemplating going through a change from managing Poa to introducing fine grasses, take advice from the experts who have a track record of this change like Gordon Irvine. Only engage them if they recognise that it is not just the technical advice that is necessary but also positive communication and involvement with the club’s membership to build an understanding of the vision of where and how to get there. This will ensure long term success.

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