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Knowing your soil type and whether it is acidic, neutral or alkaline will help you choose the right plants for your garden and how to treat your soil.
Soils usually range from pH4-pH8 and most plants prefer a range of pH5.5-pH7.5.
Some plants only survive in acid conditions while others prefer alkaline soil.
The term pH refers to the acidity or alkalinity of your soil which can affect soil texture, distribution of nutrients, and tiny organisms that dwell in the soil.
Soil acidity is measured in pH units on a scale of 1 to 14, and it refers to the amount of hydrogen (h) in the soil.
A pH of 7.0 is taken as the central, neutral point (true neutral) i.e. it is neither acid nor alkaline, although, horticulturally, 'neutral' soil is pH6.5.
Put another way; a drop of one point on the scale denotes the soil has increased in acidity by ten times, conversely, a one point drop means it is ten times more alkaline.
pH measurements from 7.0 to 0 are increasingly acid, and from 7.0 to 14 more alkaline.
Extremes below pH 5.5 (acid) and above pH7.5 (alkaline) can be problematic, with certain pests, diseases and nutritional disorders becoming more prevalent.
Magnesium deficiency and clubroot are more prevalent on acid soils, while trace element deficiencies are common on alkaline soils.
A very alkaline soil can cause nutrients to be 'locked' into the soil.
Soil types;
Clay or sandy soils tend to be acidic, and chalky soils are generally alkaline, except in areas of high rainfall.
Peaty soils tend to be acidic.
Organic / cultivated soil with a high humus content is often more acid, as decomposition produces acidic by-products.
Soils can become more acid over time, particularly in wet climates.
One should aim for a pH5.5-pH7.5.
Soil testing;
Tests should be made annually, and basically there are two ways to do this;
1) By sending soil samples to a Soil laboratory.
Quite often when taking this route, the laboratory will give information other than the pH, i.e. such things as the NPK content and amount of trace elements held in the soil.
Some laboratories will even advise you the best course of action to take to improve the quality of your soil
2) Buy a D.I.Y. test kit.
Follow the instructions on the packaging, and identify the pH by using the enclosed / attached colour chart.
After the tests;
To make your soil more alkaline by 1 pH add lime
Note; It is very important not to apply lime at the same time as you are adding manure, compost or fertilizer.
To do so may create a harmful reaction.
If you normally apply manure in the autumn then leave liming until early spring, say about six weeks before planting.
Over-liming is difficult to correct, add less than the recommended amounts at first, and adjust later after it has had time to weather in, or wait till the following season.
As an application guide use the following quantities;
apply 270grammes of Ground limestone per square metre (8oz per sq yd) to sandy soils
apply 550grammes of Ground limestone per square metre (16oz per sq yd) to loamy soils
apply 800grammes of Ground limestone per square metre (24oz per sq yd) to clay soils
To make your soil more acid by 1 pH apply 70grammes of Ammonium Sulphate per square metre (2 1/2oz per sq yd)
Adding garden compost and manure can help to make the soil more acid.
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