I associate soil pH values with miniature test tube kits, filled with garden soil, a mud monochrome of the model glass lighthouses you fill with multicoloured sand from Alum Bay on the Isle of Wight. But whilst lighthouses keep you off the rocks, soil testing kits will tell you what their ground down ancestors are made of. And once you know the pH of your soil you will know whether Rhododendrons planted in your garden will be a dead cert or dead shrub and if Hydrangeas will favour blue or pink.
As I don’t have enough soil to put in a test tube, let alone grow things in, my understanding beyond this, is vague. So Saturday Swot Shop today is Tomato Lover’s PDQ guide to soil pH .
What does pH actually mean ?
- Potential Hydrogen Ions.
None the wiser… How does it relate to soil ?
- Soil is either acid, alkaline or neutral. pH is measured on a scale of 1 to 14. The middle of the scale at 7, is neutral. Below 7 and it’s acid , above 7 and it’s alkaline. What’s being measured is the amount of lime (calcium ) in the soil.
Does it matter ?
- At certain levels of acidity or alkalinity some minerals cannot dissolve in water and so get ‘locked up’; held in the soil, meaning they are not available for absorption by the plant and so the plant is deprived of essential nutrients. Certain plants will thrive in one type of soil but die in another. The expression ‘lime hating’ plants covers those which grow well in acidic soil.
Can the pH value of soil be changed ?
- To make acid soil more alkaline lime is added to the soil. Increasing the acid in alkaline soil is more difficult but sulphur is used for this purpose.
What’s the normal pH range for soil and what’s the right soil for tomatoes ?
- Most soil is 4-8.5. Tomatoes grow best at 6.0 to 6.8, so slightly acid.
And why in pH is the p lower case and the H upper case ?
- pASS !
