The pH is a measure of the acidity or alkalinity of the soil. The pH scale has a range of 0 – 14 with 7 as neutral. Numbers below 7 indicate acidity while numbers above 7 indicate alkalinity.
The pH value of the soil affects the availability of nutrients and affects the quality of plant growth. Several plants are lovers of acidic soil and will thrive well in soil with low pH. Examples include azaleas, rhododendrons, blueberries, and conifers.
These plants thrive best in soil having a pH of 5.0 – 5.5. Also, vegetables, grasses, and several ornamentals thrive well in slightly acidic soil with a pH of 5.8 – 6.5. Most effects extremes in pH have on plants’ growth are related to the availability of plant nutrients as well as a concentration of plant-toxic minerals.
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Soils having a high level of acidity of course will contain aluminum and manganese as expected but these minerals can be more available and more toxic to the plant.
Also, calcium, phosphorus, and magnesium are less available to the plants at low pH values. Several ornamental plants and some fruit plants blueberries being an example, need slightly strong to strongly acidic soil.
If they are grown in soils in the alkaline range, they are bound to develop iron chlorosis but this can be corrected by lowering the pH of the soil.
How to lower the pH of a soil
Below are various ways to lower the pH of a soil:
1) Use of Aluminum sulfate or sulfur
To lower the pH of the soil, you will need aluminum sulfate or sulfur. Aluminum sulfate helps to change the soil pH instantly. This is due to the fact that aluminum produces acidity as soon as it dissolves in the soil.
Sulfur in its own case requires more time for it to convert into sulfuric acid with the aid of soil bacteria. The conversion rate of the sulfur is dependent on some factors such as the fineness of the sulfur, soil temperature, amount of soil moisture as well as the presence of the bacteria.
There may be a slow rate of conversion which can take up to several months depending on these factors and ideal conditions which is why most people prefer to use aluminum sulfate.
To use these chemicals in lowering the pH of the soil, ensure both materials are worked into the soil after application for them to be effective. If these materials come in contact with plant leaves in the process, they should be washed off the leaves immediately otherwise may result in leaf burn. Also do not over-apply them.
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2) Use of sphagnum peat
Another way by which you can lower the pH of the soil is by adding sphagnum peat. Sphagnum peat is an excellent source of organic matter which helps to lower the soil’s pH. To lower the soil’s pH using sphagnum peat, add a 1 – 2 inch layer of the sphagnum peat and work it into the soil before going on with the planting. However, the addition of sphagnum peat to large areas can cost more money.
3) Use of fertilizers
Fertilizers can also help in soil acidification and most of these fertilizers are safe to apply. Some of these fertilizers include mono ammonium phosphate, diammonium phosphate, ammonium sulfate, ammonium nitrate, and urea.
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I hope this article helps you understand how to lower the pH of soil. I would like to hear from you. So let me know if you have any questions about lowering the pH of soil.