Bowls clubs are often divided on whether to water the green or not. When I visit clubs to advise on this, they are generally under-watering their greens.
This results in poor surfaces, especially when a green is still within the renovation phase as described in my book Performance Bowling Greens.
You can think of Soil Moisture Deficit in much the same way as a negative balance in your bank account.
Soil Water Balance Management…
…is almost unheard of within bowling circles or certainly the bowling circles I have been involved with but is a critical part of the management program to get right for high performance and deals with the management or the “balance” of water in the soil profile (rootzone).
The approach we take to this can be thought of as being similar to a bank account; water goes in to our account (soil) and comes back out again by various means, more quickly than we sometimes think (again just like a bank account!).
One question I am asked a lot about this subject is why bother? Why bother to spend all of the time and effort to measure and manage this when the British weather is so unpredictable. Most people asking this question understand that we can add water when required but get really confused about managing water balance to make sure there isn’t too much water in the soil.
This confusion arises because the management of water is a lot more to do with soil texture management than irrigation management. If we work towards the ideal rootzone texture as discussed in Performance Bowling Greens, we won’t have to worry about excess water, the rootzone will always drain out to a point we call “field capacity”. Field capacity is when all of the micro-pore space in the soil is filled with water and the soil cannot hold on to anymore water. On a performance green the macro pores only contain water temporarily even after very heavy rain as these are the key to drainage of excess water. So you see, regardless of how excessive the rainfall we experience, the well set up, performance green will drain back down to field capacity quickly.
The main aspect of water balance we have to think about then is making sure that the green doesn’t lose too much water or have too big a Soil Moisture Deficit (SMD).
Water is lost from the soil in two main ways. Although there will be some leakage downward in most soils even from the micropores, the majority of soil moisture is lost to Evapo-transpiration. This is a measurement that combines the losses to evaporation from the soil surface and transpiration through the plants themselves.
Evaporation and transpiration rates vary considerably throughout the British Isles which is why the quantity of irrigation water applied to the sward will be different from year to year and place to place.
Where we talk about ‘evaporation’ we refer to water lost from any surface or object, whereas transpiration is that water lost from plants, and precipitation encompasses rain, snow, sleet, hail, etc.
The ability to reasonably accurately calculate irrigation need is necessary to both conserve water, and most importantly to maintain a quality sward.
Only the required amount of water should be applied. If we don’t apply enough the turf will suffer, and if we apply too much we could cause damage to the soil structure whilst wasting money and precious water.
This is not a signal to under water your green, rather a signal that you need to take a more measured approach to irrigation management, especially if your green is in renovation phase which well over 50% of UK greens are whether the club knows it or not!
In Performance Bowling Greens, a practical guide I detail a simple, but foolproof system for making sure you never under or over water your green.