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Soil pH is a measurement of acidity or alkalinity of the soil on a scale that ranges from 1 to 14. An acid soil will have a pH value below 7 and an alkaline soil will have the pH value higher than 7. A soil that has the value of pH 7 is a neutral soil.

Usually, the pH value of the soil is controlled by its calcium levels. Calcium is an alkaline element that is contained in any soil. Soils with high levels of calcium, like chalk or limestone soils, are alkaline. Calcium is washed from soil in time by water and the soils that have low levels of calcium, like sandy soils, become acidic. You can control soil alkalinity by liming or adding lime-rich elements into the soil, like mushroom compost.

Acidity and Alkalinity

You can verify your soil pH using soil test kits or electronic pH meters, taking several tests in different parts of your garden as the pH may vary from one side to another. Soil test kids are using a chemical solution that changes color when is mixed with soil sample in a small test tube. Then the color is matched against a chart that indicates the pH level of the soil sample.

Why you need to know the pH of your garden soil? Because the pH affects the solubility of soil minerals, thing that is important for a good development of your plants. For example, acid soils tend to be deficient in phosphorus, while alkaline soils tend to lack manganese, boron and phosphorus. The pH also affects the type and number of beneficial soil organisms, as well as pest and diseases. For example, worms don’t like acid soils, while clubroot, leatherjackets and wireworms enjoy the conditions that an acid soil offers.

As we all want to offer the best growing conditions for our plants is good to know that the optimum pH value is between 5.5 and 7.5, and a 6.5 value is usually the best we can offer for our plants. Also is good to know that plants also have different needs, some of them like a more acidic soil while others prefer an alkaline one, many of them will usually tolerate a wider range of pH values. There are also some plants, fortunately not too many, that will suffer hard or even die if they are planted in a soil with a wrong pH level.

It is good to verify the pH levels periodically as soil pH can change during the year. It depends on temperature and moisture conditions, and can also vary to a whole pH unit during the growing season. Temperature changes the chemical activity into the soil, so the measurements of pH are best to be done at a standard temperature of 25 Celsius degrees (77 F).

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