Lime, Lawns & the Danger of Assumptions!

 

Assumptions regarding the application of “lime”, a product used to lower soil acidity, often serve as the precursor to disease and other forms of lawn decline.  For it is a common practice of many lawn managers to apply lime annually, just assuming that it is helpful.  Unfortunately, this practice often yields a soil that is too alkaline to maintain healthy turf, and predisposes it to disease.

What’s best from an agronomical standpoint is to analyze the soil pH (measure of acidity), allowing for an informed decision to be made.

What does lime do?

As mentioned above, lime is a material that is applied to lawns for the purpose of reducing soil acidity.  Doing so is sometimes necessary for if soil acidity is too strong, nutrition and health problems follow.  However, a slightly acid condition is favorable to lawn types in Georgia, and if an application of lime causes acidity to become too weak, problems will follow.

An old paradigm

Like many raised in Georgia, I grew up to believe that one can’t apply too much lime to a lawn, for I’d often heard that.  An exception to the “rule” was if you had a centipede lawn, on which one was to never apply lime.  I was convinced of the above to the point that when I later attended college, I silently questioned my college instructors who taught of the need to analyze soil pH prior to making liming decisions.  Surely, I thought, such analyses would only reveal what we all “already know”.

Apparently, many others grew up in an environment that held some similarities as mine, as the belief that respective lime application is always good, is a common one.  The concept is so entrenched, that suggesting that it isn’t true will lead to a loss of credibility, when discussing it with some folks.   This is most common with men about my age or older.  I’ve found women to be less stubborn on the matter.

Enlightened

Years ago while conversing with a competitor that I have much respect for, I learned that his company had adopted a policy of not applying lime unless a soil acidity test was first approved, and the test revealed that the soil was too acidic.  Reason being, most of their tests revealed that lime wouldn’t be beneficial.

Liking the sound of my competitor’s method, I began to do the same.  Sure enough, a low percentage of the tests revealed a need for lime.  In fact, some tests revealed that a lime application would have a negative effect on the lawn.

Brian’s theory and some well established facts

In most portions of Georgia, the native soil is acidic.  This is factual and is common knowledge amongst those of us that have interest in such things.  I believe it to also be the reason for those long standing beliefs that are held mainly by my brethren.

The native “topsoil” is enriched by the nutrient cycling process that occurs as fallen leaves and other plant matter decompose, and in the process, acidification takes place.  However, if that rich topsoil is removed, as it likely has been if the corresponding home or building was constructed sometime during the past 30 years, the environment changes significantly.  Instead of the rich topsoil that tends to maintain acidic conditions, lawns and other landscaping are planted to what was previously “subsoil”, usually solid clay.  Absent of organic matter, the subsoil doesn’t experience the same acidification process.

Secondly, when rain is deficient, the leaching of base nutrients calcium, magnesium and potassium is reduced.  Reduced leaching of these nutrients lowers a soils tendency to acidify.  So during drought years, soil is less likely to increase in acidity.

There are other contributing factors as well.

What are the odds that lime application could cause harm to your lawn?

Over application of lime and the creation of alkaline conditions results in a lawn being unable to obtain adequate nitrogen, phosphorus, iron and other nutrients that are needed by the plants.  This condition leads to a lower lawn quality.

Where Bermuda lawns are concerned, over application of lime contributes to the probability of “Spring Dead Spot” disease, which has become very common.  Spring Dead Spot is very costly and difficult to rid of.

Spring Dead Spot discovered during a 2012 lawn inspection Spring Dead Spot discovered on Bermuda lawn in 2012

So as was mentioned in the beginning, assumptions regarding lime can be dangerous!

How do I have soil acidity tested?

If you have a lawn care company, hopefully they are suggesting this to you.  If not, they still should be able to perform the test at your request.

You can also collect a sample and submit it to the UGA Cooperative Extension Service for testing.  A small fee is charged for this service.  They can advise regarding procedure.

Soil acidity may be tested any time during the year, and in my opinion, once every three years will suffice in most situations.