A soil test is essential to planning for that new garden or changing one to accommodate new conditions. At the least, a test of the soil's pH is necessary to determine the health and vitality of the ground into which you plan to invest your landscape dollars.
Simply put, pH is a chemical term used to express hydrogen ionization in water. The term refers to potential hydrogen and indicates the breakdown of water (H2O), normally a stable molecule, into a positively-charged hydrogen ion and a negatively-charged hydrogen-oxygen molecule (HO).
The soil's acidity or alkalinity is determined by this ionization. It occurs when the various minerals and organic materials combine with water molecules forcing the soil to change its properties.
Luster Leaf 1817 Rapitest Mini Soil pH/Moisture Tester
We measure this ionization on a scale from 0 to 14. Neutral soils are said to have a pH of 7, or midway up the scale. Acid soils are those with a pH of less than 7, and alkaline soils are those with a pH above 7.
Soils with an extremely low pH – very acid soils – are said to be sour. Conversely, soils with a high pH are said to be sweet.
So much for the scientific jargon. What is important to you is the knowledge that pH directly affects your soils health. And your soils health, in turn, directly affects your plants health. And finally, your plants health directly affects its susceptibility to disease and insects, which may require you to apply pesticides which, in turn, may directly affect your health and the environment!
Most plants will not tolerate a soil with extremes in pH. The reason for this intolerance is because pH affects the release of essential elements necessary for the plant’s growth and vitality.
Nitrogen (chemical symbol N) the element we hear about most often. It is the primary element that affects productivity of plant life. That is, it is directly responsible for vegetative growth in plants. Without nitrogen, the plants leaves lack their lush green color and growth is stunted. In soils with very low or very high pH, nitrogen is trapped – a condition most plants cannot tolerate.
Phosphorous (P) is essential for strong roots, flower and fruit development, and resistance to disease. It too can be trapped in soils that are excessively out of neutral in pH. Recent tests have shown many soils have excessive amounts of phosphorous that has accumulated by excessive application of synthetic fertilizers onto tight clay soils. One of the reasons for this accumulation is that these normally high pH soils prevent the plant from using all the phosphorous that is available.
Potassium (K) is the third important element in soil health. Most often, plants us the form of potassium known as potash or potassium oxide (K2O). Potassium is essential to the plant's ability to create sugars. It is also essential to the plants capacity to resist disease, survive cold temperatures, and provide drought protection. It is less susceptible to variations in soil pH, but can be significantly trapped when soils are at their extremes in alkalinity or acidity.
Lesser know elements essential to plant vitality are calcium, magnesium, manganese, iron and boron.
Calcium (Ca) we think of as bone material – found in milk and limestone. Actually, calcium is a metal and extremely important to plants for its ability to neutralize toxic acids formed in their metabolic processes. It also serves as the building block in plant proteins and cells, and assists in the balance of magnesium within the plant's growth cycle. In very low pH soils, calcium is neutralized and plants can suffer toxic shock.
Magnesium (Mg) is essential to photosynthesis in plants. It is the main molecule in chlorophyll, the green coloring in green plants! Photosynthesis is the process by which plants use the sun's energy to create carbohydrates. Without magnesium, plant leaves turn yellow (usually at the bottom of the shrub) and soon die. Magnesium usability is limited to a narrow range in soil pH. Even slightly acid soils will inhibit its usefulness.
Manganese (Mn) is a micronutrient element. That means not very much is needed for plant health. But it is needed! Without manganese, growth of the plant is stunted. That's because this element is the catalyst to make the other elements work. The problem with manganese is its lack of availability in highly alkaline soils.
Iron (Fe) gets a lot of press. Ever wonder why? Like magnesium, iron is essential to the photosynthetic and hydrocarbon production process. Without iron, the plant is said to have iron chlorosis which manifests itself as yellowish leaves and dark green veins. Most soils have plenty of iron, but it's in an insoluble form. Soils in the alkaline range can not release the iron. And that is where many of our soils tend to be... too alkaline. The unknowing gardener (unlike you) spends a great deal of money adding soluble iron to the lawn and garden; thus curing the symptom but not treating the cause... high soil pH.
Boron (B) is another one of those must have micronutrients... not much must but definitely a must have! Boron is essential to virtually every function within the plant's metabolism, its cell growth and division, and reproduction. Ever wonder why your apples have corky centers or why your celery has cracked stems? It's a lack of boron! And like iron, high pH soils trap boron.
Okay. So what is the best way to insure your plants get these elements? The answer is simple: For most of your landscape needs, a neutral to slightly acid pH will ensure these eight essential elements are available. And what is the best way to maintain this pH? With appropriate amounts of organic materials and frequent soil tests.
Luster Leaf 1601 Rapitest Soil Test Kit
You can perform your own soil test, of course. Kits are available wherever garden products are sold or you can find them on the web. The chart above will assist you in determining the nutrients available at a given pH. And remember: The best defense against pests and diseases is a well balanced, organically improved soil.
Note: pH is measured in gram atoms per liter. As stated by Walter Reeves, Georgia Agricultural Extension Service, the p in pH is an arithmetic operator just like + or -. p stands for the negative logarithm of the concentration of the following element i.e. hydrogen. For example, an acid condition of 5.0 indicates 0.00001 or 1 x 10-5 gram atoms of hydrogen ions in a liter of solution.
