EFFECTS OF IRRIGATION ON TRANSPIRATION AND WATER RELATIONS OF VINEYARDS, IN THE TEJO VALLEY (CENTRAL PORTUGAL)
An experiment was carried out in summer of 1996 in order to evaluate the influence of irrigation on transpiration (T) and the water relations of vineyards. For this purpose, in a large unirrigated area, a small plot was established, where two single irrigations (on days 220 and 242) were applied in middle summer. Transpiration was monitored by the “Granier” sap flow method, in both plots. Leaf water potential (psi.uc.giff) and stomatal conductance (gs) were also measured. Before the irrigation, gs and predawn leaf water potential (p) were identical for both treatments. After the irrigation, gs on the irrigated plot was significantly higher than the non-irrigated plot. Data obtained from sap flow sensors showed an increase in transpiration rates after irrigation. The daily pattern of T in the irrigated plot also changed, with higher transpiration rates at noon; the non-irrigated vines showed a continuous decrease after the late morning. This corresponded with the daily trend of gs in the plots. The daily relative transpiration (non irrigated in relation to the irrigated vines) was ca. 70% and 60% immediately after the two irrigations events. These results indicated a considerable degree of stress in the unirrigated vines, in spite of the deep soils and relatively high soil water availability.
Silvestre, J. and Ferreira, M.I. (2000). EFFECTS OF IRRIGATION ON TRANSPIRATION AND WATER RELATIONS OF VINEYARDS, IN THE TEJO VALLEY (CENTRAL PORTUGAL). Acta Hortic. 537, 305-312
Vineyards, irrigation, transpiration, Granier, sap flow, water stress.