10. I have learned that the C/N ratio is important. Why ?

The C / N ratio is a clue revealing a good or bad evolution of organic matter. The analysis of earth samples gives telling indications of the environment conditions that determine the evolution of organic matters. The assessment of pH values, organic matter content, iron and manganese contents gives a fair idea of the conditions of evolution of organic matters. Therefore, the determination of the C / N ratio is not essential. The interpretation may read as follows:

High values must be linked to adverse conditions of evolution. Of course, these indications are valid for soils managed as yearly crops. Permanent grassland soils have a high organic matter content on the surface and the C/N ratio is often high too.