Consommation d'eau de la vigne en conditions hydriques non limitantes. Formulation simplifiée de la transpiration
DOI:
https://doi.org/10.5073/vitis.1994.33.109-115Keywords:
water use, water balance, evapotranspiration, transpiration, solar radiation, net radiation, trellis system, row spacing, roe geometryAbstract
La modélisation géometrique de la vigne, utilisée pour l'interception du rayonnement solaire (RIOU et al. 1989) est d'abord reprise pour évaluer les bilans radiatifs de la vigne et du sol intercalaire. La vérification expérimentale est satisfaisante. Après une période pluvieuse, les différents flux du bilan d'energie du vignoble sont ensuite mesurés, notamment grâce à la méthode des corrélations tourbillonnaires tandis que la transpiration de la vigne seule est obtenue par une mesure de flux de sève (VALANCOGNE et NASR 1993).
Trois grandeurs concernant la vigne elle-même restent proches: le taux de transpiration par rapport à l'évaporation totale , le taux d' absorption du rayonnement net par rapport au bilan radiatif total et le taux d'absorption du rayonnement solaire par rapport au rayonnement global absorbé par le vignoble; une simulation montre que ces deux derniers taux restent voisins quand la distance entre rangs varie. L'évapotranspiration maximum étant finalement exprimée correctement par la formule de PENMAN (1948), ces résultats conduisent à proposer une formulation simple de la transpiration de la vigne en conditions hydriques non limitantes.
Water use of grapevines well supplied with water. Simplified expression of transpiration
A model of solar radiation interception by a vineyard canopy from simple geometrical assumptions (Riou et al. 1989) is first extended into a model of the whole radiative balance of the vine rows and of the intervening soil surface; experimental validation is excellent. After a rainy period, the various fluxes taking part in the energy balance of a vineyard canopy were measured, among which total evaportranspiration by an eddy correlation technique, and vine transpiration from a sap-flow estimation (Valancogne et Nasr 1993).
Three partition rates quantifying the exchanges of the vines alone remain noticeably close to each other: those of transpiration over total evaportranspiration, of absorbed net radiation over overall radiative balance, and of intercepted global radiation over global radiation intercepted by the whole canopy. From a simulation, evidence is provided these two latter rates are still hardly distinguishable when the row spacing is changed. As maximum evapotranspiration is quite correctly expressed by the Penman formula, these results lead to the proposal of a simple method for estimating transpiration of grapevines well supplied with water.
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