Why Soil Test?

The performance of a plant can be directly associated with the type of soil it is growing in. Different types of plants have specific nutrient requirements and will only successfully thrive if those elements can be found within the soil and are accessible. Accessibility will vary widely depending on the soil texture: a combination of sand, silt, clay, and organic matter, along with the pH level. The soil’s texture and pH level determine how these nutrients can be absorbed. Because soil nutrients often vary from place to place, we recommend having a complete soil test done before beginning any landscape project or adding soil amendments.

A standard soil test will measure the levels of several essential plant nutrients: phosphorus, potassium, calcium, and magnesium. Nitrogen, another essential nutrient, may not be in the standard test as nitrogen content within soils can significantly fluctuate. A nitrogen test can be done with the same soil test if requested.  Another option when soil testing is determining the amount of micronutrients within the soil. Essential to a plants health, although used in small amounts, these nutrients include zinc, iron, copper, molybdenum, manganese, boron, cobalt and chlorine.

In order to take up these nutrients, many of these elements need to be dissolved in water and then absorbed through the root system of a plant. Soil texture affects how well water and these nutrients are retained within the soil. For example, water will drain quickly from sandy soils taking with it the nutrients many plants need. This is called leaching. Ideally soil should contain equal amounts of sand, silt, clay and organic matter.

Soil pH is one of the most important soil properties that affect the availability of nutrients. pH level testing comes in most standard soil testing and often provides a guide to amend your soils if the level is not optimum. If the pH level is  high or low the chemical make up of these nutrients can be altered, lowering their ability to be taken up by the plant. An example of this is seen in areas that have a high pH level which limits the availability of iron to pin oaks, causing chlorosis of the leaves.  Because these elements are only absorbed at their simplest form chemically, not only having these nutrients in the soil but having the right chemical balance within your soils is critical for the plant to successfully perform.

 

Learn more about Plant Nutrition:

http://www.ncagr.gov/cyber/kidswrld/plant/nutrient.htm

http://retirees.uwaterloo.ca/~jerry/orchids/nutri.html

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