Garden soil pH

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Garden soil pH governs
successful growing of plants

Three reasons why garden soil pH is crucial in growing the best plants in your garden;

pH affects the availability of nutrients for plant uptake
low pH increases binding in clay soils making them harder to work, more cloddy and less hospitable for plant growth
acidic pH favour anerobic bacteria that sour the soil reducing growth

What is garden soil pH?

Soil pH is a measure of 'power of hydrogen' in the soil, a determinant of how acid or alkaline the soil is.

Although represented by a scale of pH 1 to 14 chemically, in soils the range is narrower being 4 to 9 with a pH of 7 being neutral, below which your soil is acidic and above which it is alkaline.

When should you test soil pH?

If you are taking over a new plot of land, if your plants show poor growth/ discolouring of leaves then it is well worth testing soil pH to identify a posssible cause. You may also have to test for specific nutrients in bad cases in order to correct major nutrient deficiencies even after correcting soil pH.

However, if plant growth is good and healthy then your garden soil pH is probably OK.

How do you measure soil pH?

Obtain a representative sample of soil from your garden, taken by sampling a small trowel full/ core of soil in 3-4 places, combining the top 5-10cm of soil, mixing thoroughly and testing a small amount with a soil pH kit available from most garden stores/ centres.

Optimum garden soil pH

For nutrient uptake, soil structuring and biological life the optimum pH is between 6-7, ideally 6.5-7, or neutral.

This brings best availability of a wide variety of nutrients, ensures clay soils are workable, and allows aerobic bacteria and fungi to thrive to the benefit of your soil and plants.

How do you change soil pH if needed?

To raise soil pH, on an acidic soil, add garden/ agricultural lime as recommended by the manufacturer.
Lime should always be applied separately from fertilizer or manure, ideally allowing 1-2 months between them as otherwise they react and you will see no benefit or worse. If applying manure do this in autumn and then lime in early spring 2-3 months ahead of planting
To lower pH of very alkaline soils the best long-term route is just to add good garden compost or well rotted manure each year according to need of your soil and plants, of course avoiding use in the same season as carrots/ parsnips. Note that mushroom compost makes the soil more alkaline not less!

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