What does wet weather mean for golf clubs’ use of fertilisers?

Alistair Dunsmuir
By Alistair Dunsmuir June 25, 2013 16:26

What does wet weather mean for golf clubs’ use of fertilisers?

David Lawson, senior research officer at the STRI, argues that recent heavy rainfall means clubs need to look differently at the fertilisers they use

Everyone is struggling with the weather. Its unpredictability causes major planning difficulties and, with the prolonged wet and cold weather that we have been experiencing, we are simply wondering when there is going to be some grass growth.

Fertiliser-application-demo-mrBecause of the high precipitation over the winter there’s considerable concern that the plant nutrients have been washed out of the soil and rootzone profiles. So fertiliser programmes for the coming season will need to take this into account. In particular the heavy rainfall at the beginning of the year may have washed out a considerable amount of nutrient which will need to be replaced.

As well as heavy rainfall and snowfall, soils have been cold over a prolonged period. How will this affect growth in the coming season?

This article aims to look at how these factors will affect nutrient levels by the time spring actually arrives.

Potential for leaching

How does heavy rainfall during winter affect nutrients? We’ll concentrate primarily on the main nutrients of nitrogen, phosphorus and potassium, although we’ll also consider calcium magnesium and sulphate. Firstly, any soluble nutrient will be prone to leaching out of any turf rootzone. The main soluble nutrients are nitrogen, in the forms of ammonium and nitrate, as well as potassium, calcium, magnesium and sulphur, as sulphate. However, these nutrients are not equally prone to leaching and moreover soils and rootzones will vary in their ability to hold on to them.

You may notice that phosphate hasn’t been mentioned. It’s not very soluble, but more on that later.

• In essence rootzones and soils with a high sand content and low organic matter content have little ability to hold on to any nutrients. Soils with a high clay and / or organic matter content have a higher ability to retain nutrients. This is because the clay and soil organic matter have a negative surface charge which allows them to attract positively charged nutrients. Ammonium-N, potassium, calcium and magnesium are all positively charged. So these are less prone to leaching than the negatively charged nitrate and sulphate.

• Phosphate was mentioned previously; by the fact that it is not very soluble. Indeed most of the phosphate is held chemically on the oxides of iron and aluminium associated with clay. In alkaline soils calcium phosphate compounds are present, again in very fine particulate form.

So, all in all, the potential for nutrient leaching over a wet winter such as we’ve just had could be significant. There is no doubt that some compensatory fertiliser application will be required to make up for losses.

In summary the ‘likelihood of leaching’ is as follows:

However, this is not the whole story.


Up until now we have mainly been considering the soluble forms of elements such a potassium magnesium. However, in most soils a considerable amount of any nutrient is in a non-soluble form. This is particularly relevant for nitrogen. And nitrogen is, by far, the most important nutrient for turf.

We mentioned ammonium and nitrate as the soluble forms of nitrogen (N). But in fact these are present in relatively low concentration compared to the stable forms of N, within the soil organic matter. (Ammonium and nitrate concentrations will obviously increase immediately after application of a nitrogen fertiliser). The greater the content of soil organic matter the greater the nitrogen reserves. The organic nitrogen is only slowly released to soluble forms and the process requires the activity of soil bacteria. Such bacteria will only be active at temperatures greater than 5oC and are also dependent on the soil moisture, that is they are not active if the soil is very cold and / or very dry.

So for a moment let’s forget the winter that we have just come out of and return to the relatively mild winter conditions of a few years ago. In such a situation the bacteria are active enough to cause the release of soluble, plant-available nitrogen from the organic matter and there are adequate amounts of nitrogen made available for some grass growth during the winter months. However, this causes the nitrogen reserves to become somewhat depleted by the time spring comes around.

Move forward to the winter just passed and it is evident that soils have been so cold that bacterial activity has been virtually zero. So natural reserves of nitrogen will remain high and when soils do warm up and growth does take off there will be a considerable amount of nitrogen available for turf growth.

So in fact a prolonged cold winter does not mean that extra fertiliser nitrogen will be needed in the spring. Indeed the opposite may be the case, and by applying extra N it is possible that growth will be soft and the turf will be more disease-prone.

Obviously on USGA type and other sand-dominated rootzones the amount of organic matter, and therefore organic N, is lower than on a natural soil.

There is greater dependence on fertiliser N for turf growth. However, the same premise holds true. There will be no extra requirement above the normal spring dressing for nitrogen fertiliser after a prolonged cold and wet winter.


As mentioned previously, the forms of phosphate in soil are relatively insoluble and are associated with fine particulate materials such as clays, oxides and carbonates. However, the particulate material can be lost from the soil under heavy rainfall and surface drainage. The associated phosphate is lost with the material. The extent of this will depend on the physical nature of the soil and the stability of these fine fractions within the soil.

The extent to which phosphate has been lost through this mechanism can be checked by soil testing.

It is also worth mentioning that under cold soil conditions the solubility and mobility of phosphate is decreased even further. There is more likelihood of phosphate deficiency in early spring when soils are still cold, but air temperatures are high enough to encourage grass growth.

To sum up:

• Don’t worry about nitrogen, the reserves of nitrogen will still be there and so a normal spring fertiliser dressing can be applied.

• On sand-dominated rootzones do make sure that potassium is included in the first two dressings.

• Magnesium and calcium are unlikely to be deficient. Rainfall in the UK contains considerable amounts of calcium and magnesium.

• If the soil or rootzone is low in phosphate (check by getting soil sample analysis) then make sure that some phosphate is included in the first spring dressing.

• Most fertiliser products used for turf do contain sulphate and so deficiency is unlikely. However, check your fertiliser bag label.


Alistair Dunsmuir
By Alistair Dunsmuir June 25, 2013 16:26
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