Lowering Soil pH

Ieuan Dafyddin Training & Education
For many years the application of urea buffered sulphur, or similar, to fine turf in an effort to lower the pH of a soil was commonplace. The received wisdom seemed to be cast-iron in its assertions: finer grasses thrive in a slightly acidic soil, sulphur lowers pH, ipso facto sulphur is great for fine turf areas, golf greens particularly.

It took a while but some bright spark eventually put his hand up in class and said "Please Sir? Are you sure that putting sulphuric acid onto our greens is a good idea?"

Almost immediately the genie was out of the bottle and greenkeepers around the globe began to question the use of such a caustic acidification programme, regardless of the benefits (or otherwise) of acidic soil, the action of applying a dangerous chemical to fine turf was looked at with a frown.

Agronomist Robert Laycock was certainly doubtful when it came to acid programmes and penned the following in Greenkeeper international; "The effects of repeated acidification can be seen in many of our old golf courses.

Earlier this year I recently received soil samples from the greens of a well-known golf course (not a regular client). The pH values were between 4.4 and 4.8. The turf was annual meadow grass, the rootzone anaerobic and thatchy. Experience has taught me that a factor in the development of greens like this is the use of acidifying materials.

My recommendation was that the greens should be limed - I do not expect for one moment that they will be. But what would be the adverse effect of liming greens like this? What could be worse than their current condition?"

And therein lies one of the major problems of an acidification programme - it can be overdone very easily indeed.

Soil Scientist Stuart Ashworth clarified the point: "Finer grasses thrive at a pH of 5.5 to 6.5, that is a fact. However, the application of a corrosive, toxic chemical to turf in order to achieve this lower pH is inadvisable. Nitric Acid or Sulphuric Acid put into a golf green can easily cause problems - a pH below 5 might well result in unhealthy greens - this is a precise science, not a 'chuck it and chance it' affair."

Handling strong corrosive acids and sulphur treatments is, therefore, fraught with problems and can often lead to other problems such as plant scorch and increased severity of black layer. So is the movement towards acidification dead?

No, but it probably needs a facelift. The word 'acidification' is perhaps too emotive and creates an immediate stumbling block: once we have ascertained that applying acid to soil is probably not a good idea it would appear safe to assume that acidification of the soil is also a non-starter.

Enter confusion number two - it is actually possible to reduce pH of a soil to the 'optimum' pH of 6 without resorting to harsh acids.

A new, synthetic product that has recently been put on the market across Europe - Re-Phlex - replaces products like nitric acid and urea-buffered sulphuric acid without the use of toxic or corrosive harsh mineral acids. What is more, this non-corrosive, non-fuming, 100% biodegradable acid replacement system is a non-skin irritant and nonmutagenic to fish and wildlife.

So, several of the problems appear to have been removed from the acidification programmes of the past, safety and environmental issues have, apparently, been addressed. The question remains though, is the reduced level of pH on a golf green a desirable

Laycock maintained that it is not: "Many of the old greens I come across have a turf consisting predominantly of annual meadow grass on soils of pH 4 to over 7. In other words the annual meadow grass seems to do better than the bent and fescues at all
pH levels. So, does the Acid Theory not work?

And yet Ashworth is of the opposite standpoint; "Different plants need different soil properties. Try to grow heather or rhododendrons on alkali soil and you will struggle. Fine turf grass might be more of a complex issue but the basic fact remains, the pH of a soil can affect the growth of desirable species. Ideally we need the soil at a pH of 5.5 to 6.5 and, if we can achieve this without reverting to caustic chemicals, then it is certainly worth a second look."

Both Laycock and Ashworth agree on one point at least; regardless of pH values, undesirable species such as the shallow-rooted poa annua will dominate in areas of over watering. It is no surprise that the advent of widespread irrigation has coincided with the increase of many problems in fine turf, Ashworth goes further and makes an interesting observation on the source of irrigation water and the compounded problems that might follow.

"With the increasing use of alkaline bore-hole water and effluent water, more turf managers are facing the challenges that come from decreasing water quality and associated high soil pH. High bicarbonate levels in irrigation and soil water locks up essential plant nutrients making them unavailable for plant uptake.

High soil pH can encourage pests such as casting worms and create an environment for turf disease." The over-watering of golf courses in times of water shortages is anathema to all of us involved in the golf industry as is the use of harmful chemicals in the pursuit of excellence.

Therefore it would be useful if a more efficient irrigation system could be coupled with improved environmental practices and more beneficial conditions for fine turf grasses. This is where the manufacturers of the Re- Phlex soil and water conditioning system believe they score highly.

The product removes hardened deposits of lime scale that can reduce flow in irrigation pipes and heads without any corrosion worries; it will not harm other valuable irrigation equipment.With such diametrically opposed views on a very emotive topic, the lowering of pH values throughout the soil profile of a golf green (not just the surface) needs to be studied very closely and with expert advice at all stages of the process.

Whether such products as Re-Phlex are miracle cures or simply a useful additive remains to be seen. It would be advisable to keep an open mind at this point and investigate further. Certainly the question of lower pH and more than a 'black and white' answer or a cursory glance.

Water preservation,maintenance of valuable equipment, environmental protection and improved turf quality are the claims of the manufacturers. If only partly true it represents a step in the right direction, if entirely true then a big breakthrough has been achieved.

Consulting a qualified agronomist would be a good first step, as would researching the material on the internet; if nothing else it would make for an interesting and educational process.
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