Soil PH levels

Understanding Soil PH Levels…

  The degree of acidity or alkalinity of the soil is called the soils PH level.

  It is determined by the soils composition or the materials that make up the soil and is measured on a scale of 0-14.With Acid being numbers ranging from 0-7 and Alkaline being numbers ranging from 7-14.

  Most soils fall near the middle of the scale between 4.5-8.5 and are considered to have a neutral PH Value, being neither overly acidic or overly alkaline.

Why Would We Care About Soil PH Levels?

  Soil PH influences both the chemical form of elements in the soil as well as soils microbial processes.


  I know I just went all technical on you, sorry, let me explain.

  Plants are affected by soil PH because some of those elements in the soil are essential nutrients that the plant needs and uses to grow and function properly. Others of those elements in the soils can be toxic to plants when present in excessive amounts.

  Soil PH determines the amount of the existing element that is in solution at any one time. Ooops did it again, beeeep… beeeep… beeeep…(that was me backing up)

  Ok, soil PH determines the amount of the element in the soil that is available to be taken up by the plants root system at any one time. Not better?

  Hmmm…. let me give you an example….

  Palm trees in South Florida often suffer from a micronutrient deficiency of manganese that causes a condition called “Frizzle Top” The palms health suffers and the new leaves or fronds that form are weakened and smaller than normal etc. As the problem gets worse new leaves will come out withered and looking scorched or “frizzled”.

  This whole problem is due to the simple fact that Manganese has a low soluability in South Florida’s high PH – Alkaline soils. It is not that Manganese is not present in the soils in South Florida but that the PH being highly Alkaline will not allow much of the existing manganese in the soil to be in an available form that the palm is able to take in through its root system and use.

Better? Ok, whew, moving on….


Raising Soil PH


Acidic Soils: 

–   Characteristic of heavy rainfall areas high in sandy as well as humus soils.

–   Help raise the PH of very Acidic soils by adding lime in the form of agricultural limestone.

Lowering Soil PH


Alkaline or High PH Soils: 

–   Characteristic of light rainfall areas with soils high in lime like limestone marl or seashells and sodium content. High Alkalinity can also result from concrete left over from construction of a new home or mortar from a wall that was just built etc.

 – Help this condition by adding organic matter compost or cow manure, composted leaves, peat moss, ground pine bark or other wood chips, mushroom compost,earth worm castings and elemental sulfur can be incorporated into the soil to help lower the PH.

  I should note here that not all sulfur compounds that increase sulfur levels will acidify the soil, so don’t use calcium sulfate(gypsum) or potassium sulfate or magnesium sulfate(Epsom salt) to acidify the soil, you will be wasting time and money. You can use some sulfate compounds such as ammonium sulfate aluminum sulfate or iron sulfate that do have some soil acidifying results. All attempts to change soil PH will be temporary.

The clayey soils in North Florida tend towards acidity.


 Tips for wading the preverbial waters of the PH scale.

–    Concern about PH in a normal landscape situation is almost always exaggerated…it must be just fun to write about. I’ve been blabbering on unnecessarily for days!

–            Landscape plants are more tolerant to PH than most of those little tags that come on plants would imply.

–            Lowering soil PH with elemental sulfur will result in a lower PH for all of a three week period before it is used up and the soil begins to return to its original value! Now that’s an uphill battle.

 –      Popular Florida lawn grasses including St. Augustine, Bahia, Centipede and Bermuda are tolerant of Acidic soils commonly found in North Florida.