Modify Soil pH of Acid and Alkaline Soil

Last Updated on August 23, 2021 by Grow with Bovees

Knowing the difference between acid and alkaline soil will help you to much better understand which plants you can grow the best.

Most plants do well in soil which is neutral or slightly acid but there are some which require distinctly acid soil.

They will not grow in soil which is even mildly alkaline and they should, therefore, not be planted in regions where the soil and water is alkaline.

The acidity or alkalinity of the soil is measured in what are known as pH values.

What Does pH Mean?

Numbers from 1 to 14 are used to express the degree of acidity or alkalinity. A pH of 7 shows that the soil is neutral – that is neither acid nor alkaline.

The change up or down of more than 1 is important as a change of a single digit indicates a tenfold increase in acidity or alkalinity.

Soil with a pH of 5 is ten times more acid than one with a reaction of 6.

Most plants grow well in soil with a reaction between pH 6 and 6.5, but plants which like acid soil may require a pH of 5 or even lower, while the lime-loving ones may need a pH of 8.

Acid soils tend to occur in regions of high rainfall and alkaline soil in areas where the rainfall is low, but this is of course, not universally true.

Does Lime Lower pH in Soil?

Lime is sometimes used in the garden as a soil amendment to raise soil pH.

This is because lime “sweetens” the soil and helps to counteract the acidic conditions found in many gardening areas.

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Lime can be used in an area that is naturally acidic, or where a more acidic soil has been created by over-fertilization.

The word lime is somewhat misleading, since it is not a type of plant.

It is a naturally occurring substance known as calcium carbonate that is extracted from limestone.

How Can I Test the pH of My Soil at Home?

There are many risks involved with growing your own food, including exposure to pesticides and chemicals, diseases, and environmental threats like flooding, which can destroy your crops overnight.

There are soil test kits available for doing soil tests oneself or one can send soil samples to a professional who does tests of this kind.

One of the best ways to mitigate these risks is by testing your soil on a regular basis.

And there’s no better way to do this than with a simple pH meter.

Can I Change The pH Of My Soil?

Where soil is too acid for good growth a sprinkling of lime should be applied to the soil at the time of planting. But lime should not be used unless the pH is lower than 6, and the plant requires a more alkaline soil.

Lime tends to make food elements in acid soil more readily available, but, in soil which is highly alkaline with a pH of 8 or higher the opposite happens and plants will die because the necessary food elements become unavailable.

In regions where the soil is alkaline it is advisable to choose plants which are tolerant of such soil.

The alkalinity of the soil can be reduced by the regular application of certain chemicals but it is nevertheless wiser to select plants that tolerate alkaline conditions rather than to have to treat the soil constantly.

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Iron sulphate, aluminium sulphate and iron chelates, obtainable from garden stores, are quick-acting in changing the character of the soil.

How often it is necessary to apply this kind of correction depends on the nature of the water used in the garden. If it is highly alkaline the salts will build up in the soil fairly quickly.

Plants which like acid soil (e.g. azaleas) should never be given ordinary garden fertilizers as these have an alkaline reaction and can cause their demise.

Even compost to which lime has been added may have an adverse effect on them.

Such plants show chlorosis, i.e. yellowing of the leaves when the pH value of the soil is too high, and the ground should be treated around the base of the plant with one of the chemicals mentioned above. A mulch of pine needles or oak-leaf compost will also help to acidity the soil.

Do Coffee Grounds Raise or Lower Soil PH?

Coffee grounds are acidic (they have an alkaline reserve of 5.3), so it is tempting to think that using them in your garden will lower soil pH. However, there are a couple of things to consider before using them for gardening. For one, the acidity of the grounds is tied up in the coffee bean itself, which means you are not really adding any acid to the soil with these grounds.

The best way in gardening to use coffee grounds is to add them to your compost pile or compost tumbler.