Soil Testing

Soil Testing

When selecting a commercial laboratory for soil testing, it is generally advisable to choose a local one. This article will elaborate on this topic in detail.
Gardenerdy Staff
Plants need the right nutrients for their growth, and these nutrients are absorbed from the soil in which they grow. Many times, the soil may lack the exact nutrients needed by the plant, and so, it is necessary to provide these by way of fertilizers. What you need to know is the soil composition, so you know exactly how much or how little fertilizer to add. Too much can harm the environment, and too little won't have much effect on plant growth. To effectively know how much fertilizer is required, samples are taken and soil testing is done in a laboratory.

Soil testing is necessary for the following reasons :
  • To know the characteristics of the soil
  • To know what fertilizer is required for overcoming deficiencies
  • To know what quantity of fertilizer is needed so that fertilizers are used only as needed, not too less or too much (This saves money, as you don't have to buy more than necessary and also help protect the environment)
  • To be able to follow better agricultural practices and achieve higher agricultural production
Collecting Samples
  • Collect separate samples from each field.
  • Collect samples from different areas of the same field, and mix them up thoroughly.
  • If the same field has distinct areas with different appearances, take different samples and keep them separate.
  • Make a map of your field or fields, and mark the areas from which the samples were taken.
  • Dig to about plow depth to take samples.
  • Take samples with clean tools. If the soil is soft, you can easily take samples using a trowel, spade, or tube. If the ground is hard, you may have to use an adze, screw auger, or post hole auger.
  • Clean tools before taking sample from another area.
  • Collect the samples in a clean bucket.
  • Clean the bucket if it has been used before to take samples from another field or if it is going to be used again. This is to avoid any contamination.
  • Pack the samples carefully.
  • Mark the samples so you don't mix them up.
  • Get sample information forms.
  • Fill them out for each sample.
  • Provide correct information about land topography, irrigation, drainage, and crop varieties grown currently and in the past.
  • Send filled forms together with the samples to the laboratory for soil testing.
Testing Method

When selecting a commercial laboratory, it is generally advisable to choose one that is local for the following reasons:
  • The people at the local laboratory are likely to know more about local garden and farming conditions.
  • They will have more experience in analyzing the local soil.
Soil testing needs to be done as soon as possible, preferably within 24 hours. Or there is a chance of chemical changes taking place. If testing can't be done at once, then the sample must be frozen or air dried to make it stable for a longer period.

There are various kinds of tests that can be carried out. You need to have specified in your forms which tests are required for your purpose. Here are some tests that are carried out:
  • Testing for the major nutrients - nitrogen, phosphorus, and potassium
  • Testing for the secondary nutrients - sulfur, calcium, and magnesium
  • Testing for the minor nutrients - iron, manganese, copper, zinc, boron, molybdenum, and aluminum
  • Testing for Acidity
  • Testing for the Electrical Conductivity
  • Testing for the organic matter
  • Testing for the moisture
  • Testing for contamination (if any)
If you don't require quite such comprehensive tests and don't want to go through all the formalities of sending samples to the laboratory, you can carry out some tests yourself with a do-it-yourself testing kit. You can buy these from the lab or from an agricultural products store. The number of tests possible with these kits is quite limited, but you should be able to do the following -
  • Testing for the major nutrients - nitrogen, phosphorus, and potassium
  • Testing for Acidity
But, keep in mind that the lab report will be more detailed, and probably more accurate.
Ecological test