Soil Testing

Most people have strong trust in any scientific work. Therefore, when it comes to soil fertility,

farmers might also think of getting their soil analysed in a laboratory. Though chemical soil

testing may yield valuable information to specific questions, farmers should not expect too

much of it.

For example there are some inherent problems related to analysing nutrient contents: For

the plant, the total content of a certain nutrient in a sample is not always relevant, as the

nutrient may be absorbed to minerals so strong that it is not available to the plant roots (e.g.

Phosphorus, see chapter 4.1.3). Therefore, some tests treat the sample with solvents in

order to simulate the fraction of the nutrient available to plants. This might be a realistic

simulation for conventional farming. In organically managed soils, however, the higher activity

of soil organisms can result in a better availability of the nutrient, thus the result of the test

is not fully appropriate. The content of other nutrients such as nitrogen is extremely fluctuating

within few days, so that it highly depends on the point of time when the sample is taken.

Still, chemical soil analysis can be useful in some cases, e.g. to analyse the level of acidity

of the soil (pH) or to detect deficiency of nutrients such as Potassium (K) or Zinc (Zn).

Organic farmers might be especially interested in knowing and monitoring the content of soil

organic matter.

Chemical soil analysis on pesticide residues is highly complicated as one must know which

pesticide to look for, and they are very costly. Physical testing, e.g. related to water retention

capacity or soil structure can yield interesting information, but samples must be taken very

carefully. Biological analysis, e.g. of the activity of soil organisms, must be done in specially

equipped laboratories and is rather costly. Altogether, the use of soil analysis on the farm

level is limited due to the scientific methods, the availability of suitable laboratories and the

costs involved. If soil tests are used, make sure that the relevant aspects are investigated