J. Eastham et Sa. Gray, A PRELIMINARY EVALUATION OF THE SUITABILITY OF SAP FLOW SENSORS FOR USE IN SCHEDULING VINEYARD IRRIGATION, American journal of enology and viticulture, 49(2), 1998, pp. 171-176
An experiment was carried out to evaluate the potential for the use of
sap flow measurement for scheduling irrigation in vineyards. Sap flow
was measured over a 35-day period on 5 different varieties of grape v
ines (Vitis vinifera), with canopy leaf areas ranging from 3.4 to 16.4
m(2). Irrigation was withheld from some vines to investigate whether
sap flow sensors could be used to detect effects of water deficits on
transpiration rates. Data obtained from sap flow sensors under well-wa
tered conditions showed differences in transpiration rates caused by d
iffering canopy sizes and changing evaporative demand due to diurnal a
nd daily changes in meteorological conditions. When transpiration rate
s were expressed on a leaf area basis, mean transpiration from irrigat
ed and non-irrigated vines were initially similar. With time, transpir
ation from non-irrigated vines became less than that from the irrigate
d vines. Also differences in diurnal patterns of sap flow became evide
nt, with significantly more sap flow found at night for non-irrigated
vines than for irrigated vines. Thus sap flow sensors were able to det
ect differences in both the timing and amount of water used by irrigat
ed and nonirrigated vines and hence have potential application in irri
gation scheduling.