Plant Tissue Analysis Complements Soil Testing Services
Various tools are available for enhancing growth and reducing plant problems. Each tool has it strength and limitations. Soil testing is not always 100% adequate in resolving plant nutritional needs. It is estimated by some to be only 75% accurate. Soil testing is valuable in resolving major problems but does not do well with minor adjustments nor does it perform as well in soils which have poor physical properties. Soil tests can be valuable when calibrated for a specific plant in a specific soil. Since there are thousands of soil types and numerous plant species which differ in their responses to soils and nutrition, this is difficult.
The most efficient procedure to assess plant nutritional requirements is with the use of various combined analyses. Visual symptoms, the result of plant growth to different treatments as well as soil and tissue testing need to be used. It is best to have a second opinion before applying nutrients which can not be readily removed from the soil.
The micronutrients are needed in very low amounts. Boron for instance has a very fine line between optimum levels for good growth and the toxic level. Poorly buffered soils such as sandy soils can be adversely effected with the application of an essential trace metal. A little too much zinc or copper can induce an iron or manganese deficiency.
Since the root systems of plants assimilate the nutrients, the availability of nutrients present in the soil depends upon the size and status of the root system. A very invasive root system in an infertile, loose, friable soil can give good growth as well as a more restrictive root system in a fertile soil. Most nutrients move with the flow of water to the roots. Low levels of nutrients over a large root system are just as effective as higher levels of nutrients in a smaller system. The proper evaluation of soil when using soil testing should include fertility as well as physical evaluations. Otherwise, plants can be used as a bioassay to determine what is really available. The measurement of nutrient uptake by plants eliminates all the complex interactions of soil and gives a picture of what is available.