By Ken Naylor
I was interested to read in Pitchcare's June Article on Irrigation Management in the section titled Compaction Relief and Aeration "Thus, a major influence of compaction on turfgrass is a decrease in water usage". And it got me thinking!
There is a major misunderstanding amongst many bowling Greenkeepers and some agronomists that compaction is caused by rolling on wet soil conditions. This may be true given a high clay content, where the water is literally squeezed out by too heavy rolling or rutting caused by vehicles but, as the majority of bowling greens are built on a sandy base, the opposite is more likely to be true.
Compaction is caused by rolling in too dry conditions when the soil particles can be physically squeezed together in the absence of water. To put it another way "wet soils cannot be compacted until the moisture content has been reduced" - a well known Civil Engineering fact. This helps to explain why the heads on many bowling greens are in a deteriorated condition; the compaction being caused, not necessarily by rolling, but by a concentration of bowlers' feet. This misunderstanding may also explain why there seems to be a trend these days amongst many Greenkeepers not to roll. Of course, rink settings should be changed daily to help avoid the corridor affect and popular rinks used for practise because they are nearest the clubhouse door should be rested and saved for recognised games.
Most bowlers want fast greens with even draws (flat green bowlers anyway) and, to achieve this, mistakes in greens maintenance are made. Greens and particularly heads are often maintained in too dry a condition with grass mown to 3mm or scalped to less which, in hot sunny weather, not only puts the grass under undue stress but causes future soil compaction problems leading to all manner of ills. This will also include surface scarring due to the impact of poorly delivered bowls onto a soaked wet turf with underlying dryish soil compaction e.g. following rain.
Following on from the above, one can understand that turf with a thatch problem and poor surface draining characteristics cannot be made sufficiently firm to provide fast running surfaces to achieve a pace of say 12 to 14 seconds, especially when wet, due to "sponginess".
Deep scarification, carried out to say a depth of 25mm to provide aeration and to tackle the thatch problem, can also cause temporary "sponginess" especially at the beginning of the playing season, although immediate dressing with a sandy topdressing material and thoroughly working-in will help to prevent this.
Hollow core tining and spreading of topdressing material by barrow, shovel and rake over many years without proper spirit-level levelling can also lead to surface level problems affecting the run of the bowls. Solid core tining and sarel rolling can provide good results and is a safer option in many cases.
Greenkeepers can be put under pressure from bowlers and committee members with little knowledge of agronomy to do all kinds of undesirable things in order to achieve pace for example, and then subsequently, when greens deteriorate, the Greenkeeper is considered at fault.