How Soil pH Affects Plant Growth
Your garden or the landscape frequently needs to be checked if the soil pH is appropriate with your gardening requirements or not. If you are not getting required response even after using fertilizers you must get the soil tested and ph Level determined.
pH Values and pH Scale
pH is the measure of acidity or alkalinity of a soil. The pH scale runs through 0.0 to 14.0 values on the scale. The most acid soil would have 0.0 value stands for the most acidic soil while 14.0 is the top value for the most alkaline soil on the pH scale.
Middle of the scale i.e. at 7.0 values is attributed to the neutral soil. Meaning thereby, the soil with 7.0 pH value would neither be acidic nor alkaline in nature on the scale.
A soil starts getting more acidic in nature as the pH values decrease from 7.0 to 0.0 and likewise the soil would become more alkaline as pH values increase from 7.0 to 14.0.
For instance, lemon juice having a 2.4 pH value will be acidic in nature while water has 7.0 pH values and therefore is neutral. On the other side soap solution with 9.3 pH value would be alkaline.
How Soil pH Affects Plants Growth
Soil pH affects plant growth in many ways.
Bacteria that are responsible for any change and release of nitrogen from organic matters and some fertilizers have a more suitable operating environment within a pH range of 5.5 to 7.0 making this the optimum pH range. Plant nutrients are abundantly available for the plants and soil when the soil pH remains within this optimum pH range.
If the pH value of the soil is below 5.5 then several plant nutrients start leaching from the soil at greater speed compared to the soils within the 5.5 to 7.0 range.
In some mineral soils aluminum can be dissolved at pH levels below 5.0 becoming toxic to plant growth. Soil pH may also affect the availability of plant nutrients.
Soil structure also gets immensely affected by the pH, in clay soils. Clay soils generally remain granular within the optimum pH range and that is why it is always easier to work with such soils. Cultivating is easier with the clayey soils. However, if the soil is either extremely acid or alkaline clay, soils tend to become sticky and hard to cultivate.
Exact nature of the soil with its specific pH value and position of the pH scale can be determined by pH soil test. The soil test will reveal whether your soil is within the optimum range or whether it will need to be treated to adjust the pH level.
You must remember that despite the fact that optimum range is 5.5 to 7.0 some plants will grow in a more acid soil and some at a more alkaline level.
Experienced gardeners know it very well that the pH is not an indication of soil’s fertility, but it does affect the availability of fertilizer nutrients. Even if the soil contains adequate nutrients yet plant health may be limited by an unfavorable pH level.
In order to correct the pH of an acid soil (5.5 to 0.0) use lime or dolomite would be more advantageous. Lime contains mainly calcium carbonate (caco3) and dolomite contains both calcium carbonate and magnesium carbonate. (mg2co3). In home gardens and landscapes ground limestone and dolomite are highly recommended as these cause less likely burning of plant roots compared to the hydrated lime.
A simple equation is easy to remember while changing pH level of soil. The greater the amount of organic matter or clay in a soil, application of more lime or dolomite uniformly at least six inches into the soil required to change a pH level for obtaining best results.
In case of soil being extremely alkaline you will need to determine if the alkalinity is because of the soil’s own character or external application of additional lime.
Although it appears feasible chemically but as a matter of fact is extremely difficult to change the nature of soil, i.e. changing the pH of soil that is naturally alkaline even with adding sulfur, ammonium sulfate, or similar acid forming materials.
A soil with high pH values could also be due to externally applied lime or dolomite, acid forming materials like sulfur or ammonium sulfate can be applied.
Reducing the soil pH would then need application of superfine dusting or water soluble sulfur. Repetition of the application of sulfur should not be made more often than once every two months because soil sulfur oxidizes and mixes with water to form a strong acid that can burn the plant roots.
You will require approximately 1/3 the amount of sulfur to decrease the pH one unit as it does limestone to raise soil pH one unit.
Applying sulfur coated fertilizers to the soil that is mostly alkaline due to the high sand and shell content would be better. Coated fertilizers are usually slow release kind and fertilizing this way is more environmentally friendly. It also adds much needed sulfur to you landscape slowly.
Soil texture can also be easily determined with the soil test and there may be soil textures like sand, loamy sand, sandy loam and sandy clay loam.
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