2.6.4.e Decision-making review: order of priority of the parameters to be corrected

Having defined all the relevant parameters and the selection criteria for the products used, a summary of the order of priority of the parameters is helpful.

1. Correction of soil acidity and S/CEC by liming.
   Why: the soil's biological activity, the availability of mineral elements and the risks of metal toxicity greatly depend on this parameter. Managing the pH is the way to control this environment.

2. OM then C/N.
   The two values should be considered together to know whether or not to apply a fertiliser and what type. Example: high OM and high C/N, low C/N fertilizer. If low OM and normal C/N: soil improver.
   Moreover, good management of organic matter also enables the management of nitrogen and most of the mineral elements in typical cases through the simple biological activity of the soil (no problems of assimilation by the vine, no particular imbalances etc.).

3. K, Mg and K/Mg.
   Similarly, these two values should be considered together because either one can reduce the assimilation of the other. The soil improver should be chosen according to whether or not the K/Mg ratio or the K2O/MgO ratio needs to be rebalanced. Most of the time the ratio is in favour of potassium but rather than trying to rebalance this parameter at all costs it is better to focus on not making the situation worse. If the vine does not show any symptoms of deficiency, this means that despite the results of the soil analysis there is no assimilation problem.

4. Nitrogen.
   Nitrogen is released via the soil's biological activity, so a healthy OM and a healthy C/N should result in normal nitrogen values. Hence its low ranking in the order of priorities despite the fact that it is essential for the vine's development. If a real deficiency is observed in the vineyard, then fertiliser should be applied to the soil.

5. Manganese and boron.
   Depending on the observation of the leaves and the results of branch analysis, foliar applications to make up for any deficiencies are a good option.

6. Phosphorus.
   Only prior to planting because there is never a deficiency even if the soil only contains very small quantities. Most soil improvers include small amounts of phosphorus, which are more than sufficient.

To encourage autonomy in a plot, the best method is to manage the soil's biological activity. This enables good mineralisation and a natural, moderate release of all the necessary elements for the healthy development of the vine (nitrogen, magnesium, potassium etc.). The second factor is the management of the pH and CEC saturation rate (S/CEC). These two parameters impact element availability for the plant as well as the soil's biological activity.
The management of soil pH, S/CEC and soil biological activity via organic matter and the C/N ratio enables the majority of situations to be covered. The K/Mg ratio allows a more detailed selection of the soil improver's properties.

The remaining elements measured in soil analyses make it possible to manage more complex cases of deficiency or toxicity. In most cases, these values are simply checked to see if they are normal or not. If not, corrective action must be taken. This is mainly the case for trace elements. Branch analysis enables observation of assimilation problems in the vine, even when the elements are available in the soil, and therefore to look for the origin of such assimilation problems, and to correct them if possible or to compensate them with a foliar application. It is at this point that a deep understanding of the vineyard is important, especially the plot's hydric behaviour, its vigour, the nature of the root system and its soil and subsoil.