What is soil pH?
The pH scale measures whether soil is acid or alkaline. The numbers on the scale run from 1 to 14, with neutral at 7. Levels below 7 are rated acidic; levels above 7 are alkaline. To find out your soil’s level, test it with a pH soil test kit, or have it tested professionally. Soil pH affects the nutrients available for plant growth. Most plants prefer a slightly acidic pH level of 6.0 to 6.5. Fortunately many soils oblige by falling within this range, but the soil in some regions is more acid or quite alkaline, and that limits which plants will thrive there. In very alkaline soils – and above – acid-loving plants such as rhododendrons and azaleas are not able to get the necessary nitrogen, phosphorus, iron and other nutrients that are dissolved in soil moisture. Their roots actually need acidic conditions to be able to absorb soil nutrients.
All soils can be classified as acid, neutral, or alkaline. The degree of acidity or alkalinity of a soil can be described by a pH value. pH values range from 0 to 14. Any value below 7.0 is considered acid, a value of 7.0 is neutral, and a pH above 7 is alkaline. Thus, a soil with a pH of 5.8 is acidic, whereas a soil with a pH of 7.9 is alkaline. Soils become more acid as pH values below 7.0 decrease numerically (see Fig. 1). In fact, there is a ten-fold increase in acidity for every decrease by one whole pH unit. For example, a soil with a pH of 5.5 is ten times more acid than a soil with a pH 6.5, and a soil with pH of 4.5 is 100 times more acid than the soil with a pH of 6.5. Similarly, for every whole unit increase in pH above 7, there is a ten-fold increase in alkalinity. pH values are usually reported to the nearest 1/10th of a whole unit on a soil test report (ie. 6.2, 7.0, 8.5). Many plant species show a preference in regard to soil pH. Whereas rhododendrons and azaleas prefer
Soil-testing kits available and by and large they do a very good job of accurately testing your soil. However, if you are only interested in knowing if your soil is acid or otherwise, without worrying about degrees of acidity or alkalinity, here is a simple test you could make. First, buy a packet of blue litmus papers from your chemist. Next, using a trowel, take samples of soil from different sections of the area you wish to test. Mix well together. Then add sufficient of this soil to fill a breakfast cup and pour boiling water over it to form a sticky mass. Then, using a knife, make a slit in the soil an inch or so deep and insert a litmus paper for about three parts of its length. Make sure that both sides of the litmus paper are making contact with the soil and allow it to remain there for 15 minutes. After that time remove the paper. If it has turned red your soil is acid. If the paper is only faintly red the soil is only slightly acid, but if it turns very red your soil is very
