Bluelab Soil pH Pen - Manual (Page 7)

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7
6.0 Information about measuring the pH of soils/media
pH is the measurement of the hydrogen ion concentration (H+) - acidity and its
opposite, alkalinity. Neutral pH is 7.0 pH. Acidity measures below seven pH (7.0 pH)
with alkalinity measuring above it (7.0 pH). See chart below.
In soils or growing media, pH strongly infl uences the availability of nutrients and the
presence of microorganisms in the soil.
Certain plants require a particular pH range to enable the required nutrients to be consistently available
to the plant. If the solution is too acidic or too alkaline it can cause “lock up” – a situation which restricts
certain elements essential for growth from being absorbed by the root structure. This in turn reduces plant
health and performance. Defi ciencies in the required elements become apparent in plant growth and can
lead to crop failure.
Low soil pH causes aluminium and manganese toxicity in plants and reduces the availability of soil
phosphorus. High soil pH also reduces soil phosphorus availability and reduces micro nutrients
such as zinc and boron to plants.
The chart below shows how nutrient pH levels infl uence the uptake of certain elements.
Recommended pH range
for plants grown in:
can be plant specifi c
Solution Soil
5.5 - 6.3 6.2 - 7.2