These two analyses provide a better understanding of what is going on in terms of mineral assimilation. It is possible for all the necessary nutrients to be available in the soil but for a vine to present deficiency symptoms. For plots without problems, an analysis every four years may be sufficient. In the event of a particular problem, more regular analyses or even at different stages of the same year may be appropriate.
Petiole analysis gives an image of the mineral assimilation by the vine at a given time. It can be done at different stages: flowering, fruit set, véraison.
An analysis at véraison is more common but it does not permit intervention in the current year, except in the case of stalk desiccation. Analysis at flowering can enable intervention on plots where, for example, coulure regularly occurs.
Petiole analysis provides a precise characterisation of cations (K+, Mg2+, etc.) and their transport in the plant. For all the other mineral elements, leaf blade analysis is more precise. The choice of analysis should therefore be based on the requirements.
If a potassium or magnesium deficiency or excess is observed, a petiole analysis is recommended, as well as for routine monitoring. Otherwise, leaf blade analysis is recommended (trace element deficiency, new plot, nitrogen problems, etc.).
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