Glossary of water testing
Comparative Soil test ranges
Water quality and Soil testing
So much has been written (or not as the case may be) on water quality and its relation to turf and soil that there is now a huge amount of confusion occurring within the turf industry. The majority of work that has been done is in horticulture or broad acre agriculture and this has then been simply transplanted and applied to the turf industry. As a result sadly the principles used have often been misrepresented in the marketplace.
Obviously, the quality of water is important but measures can be taken to improve this to make it more acceptable to use. What these are will depend entirely on its initial quality and what turf managers are trying to achieve.
Applying principles based on horticultural research to for example the irrigation of golf greens with water of varying quality is fraught with issues. Golf greens possess unique biological and vegetative characteristics that make such principles questionable if applied exactly. Sand based golf greens as their name suggests contain a high percentage of sand which means that they are going to behave differently when irrigated compared to for example a heavier fairway containing a high percentage of clay. In the case of the latter this can be further extrapolated to take into account the exact type of clay present as this has an impact on how the fairways behave.
The principle of sodium adsorption ratio (SAR) or SARadj with an upper acceptable limit being regarded as gospel is also questionable. Golf greens as mentioned earlier are often composed of a high percentage of sand and in that case a limit of 10 can be regarded as being acceptable. How often has this figure been used rather than the usual figure of 6 (which is accepted as being the limit in agricultural situations on heavier soils)?
The reason for writing this is to offer a guide for what limits are acceptable and to also explain how calculations are made. Taking SARadj as a case in point there are a actually a number of means of calculating this and the most common one used is based on the work by Ayers and Westcott in 1976 which tends to give a slightly inflated value. A much better methodology is one based on work by Suarez in 1981. I’ll discuss this in more detail later. Bearing this in mind when you get a water test do you actually know the methodology is being used? This can have a major impact on the interpretation of these results.
We have written this as an overview of the testing methodologies used. Accompanying this is an easy to use water quality calculator. All you have to do is enter your test results and it does the rest for you
References are available if required for those of you who feel a need for further reading.
There now appears to be little by way of consistency of testing or interpretation of soil tests. Different methodologies will lead to different results and fertilizer recommendations. Unfortunately many of these ''sets'' appear to arbitrary with no factual basis behind them. Opposite is a summary of US work showing how variable interpretation can be depending on the extractant used.