2.6.2.c Soil analysis

What information is obtained from a soil test?

This analysis provides all the necessary information regarding the nature of the soil and therefore helps decide whether or not to add a soil improver, and its properties according to the major analytical points. Among the data of interest, there are:

• Soil texture, which determines the value scale for the other tests.
• Water pH, which has a major impact on biological activity
• The proportion of OM % (organic matter in the soil)
• The C:N ratio (carbon to nitrogen)
• Annual OM loss estimation using different indexes (k1 and K2 respectively humification and mineralisation)
• Phosphorus, potassium and magnesium availability
• The CEC (cation exchange capacity) defines a soil’s nutrient retention capacity. The richer the soil is in organic matter and clay, the higher the CEC.
• The saturation rate of the CEC. The cations present are mainly Ca2+, Mg2°, K+ and Na+. In acidic and unsaturated soils, H+ ions are present. The ratio of each ion in the CEC indicates the health of the CEC and thus the availability of minerals to the vine.
• Trace elements (boron, manganese etc.)
• The presence of active limestone which is very valuable for planting (calculation of the chlorosis power index)

How often should this analysis be carried out?

An analysis every four years ensures that the plot is properly monitored. This type of analysis cannot be done every year because of the cost and time required for sampling. Moreover, a single year is not enough to correct any soil problems. Frequent monitoring is therefore unnecessary.