Acid Or Alkaline

All successful gardeners know that some plants prefer an acid soil; others grow better in alkaline conditions. It is important therefore to establish the nature of your soil.


The rate of pH is the standard form of measuring the rate of acidity or alkalinity of a soil. The pH scale starts at 1 for extremely acid and goes to 14 for the very alkaline side Neutral soil would have a reading of 7.


This acid/alkaline factor is important because only in the vicinity of the neutral mark are most elements appreciably soluble in the soil and unless they are easily dissolved in the soil water they cannot be taken up by the plant roots. Therefore in a very acid or alkaline soil it is possible to have deficiencies of elements that are actually present but are unavailable to the plant.

 

For example, essential elements such as

  • potassium,
     

  • phosphorous,
     

  • boron
     

  • molybdenum

begin to lose solubility as acidity increases (less than about 1.001).
 

Similarly, as soils become alkaline or limey (about 7.0pH), manganese and particularly iron become insoluble and unavailable to the plants. Iron deficiency is quite common when soils have been heavily limed as lime reduces the acidity or inversely increases the alkalinity. The symptom is a yellowing of the foliage, particularly of the new growth, and it is referred to as 'lime-induced chlorosis' or iron deficiency.
 

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