30
Introduction
Measuring soil and plant water status to provide decision
support in irrigated agriculture is on the brink of a breakthrough,
Zith the deYeOoSPent oI robXst Dnd reOiDbOe fieOd sensors
being made available to growers.
Previous research on water stress measurement through
XtiOizing therPDO diIIXsiYity Dnd YDSor SressXre deficit sensors
has led to the suggestion that water dynamics within a plant
will be better understood through the combination of data
gDthered IroP both sDS ÁoZ Dnd steP diDPeter YDriDtion
in particular to enable accurate measurement of plant water
status in a grapevine cane under conditions of increasing
water stress.
The perception gained was that change in stemwater content
was the driving force behind the changing thermal diffusivity,
as transpiration drained stored water from the plant stem.
In order to understand more on measuring water stress in
grapevines through the use of thermal diffusivity and vapor
SressXre deficit sensors D series oI fieOd triDOs Zere cDrried oXt
using an improved thermal diffusivity(TD) sensor implanted
in the xylem tissue of Cabernet-Sauvignon grapevines in a
commercial vineyard.
The purpose of the research was to test to what levels the
incorSorDtion oI D YDSor SressXre deficit (VPD) sensor into
the TD sensor would allow the response of the plant to
be compared to the daily atmospheric demand that drove
chDnges in sDS ÁoZ Dnd steP ZDter storDge
To provide a clear picture, a mathematical algorithm designed
to provide accurate reporting a single ‘crop water stress’
figXre ZDs deYeOoSed DiPed to SroYide YineyDrd PDnDgers
with a simple and robust daily value, which would integrate
the crop’s response over the previous diurnal cycle.
Despite considerable efforts to the contrary, to date, there
is no simple strategy in place where irrigators can arrive
at a daily crop water stress quotients that will allow them
to confront the challenge of applying exactly the correct
quantity of water to their vines.
7o SroYide D cOeDrer SictXre D series oI fieOd triDOs into
crop water stress was carried out over two consecutive
growing seasons in the Riverland region of South Australia,
a region which is currently producing more than half the vast
continent’s wine production.
Field Trial Methodology
Field trials were conducted at a 250 Hectare vineyard,
situated close to the town of Waikerie in the SouthAustralian
Riverland.
7he triDOs Zere bDsed DroXnd fiYe treDtPents 7 thoXgh to
T5 were instrumented, having irrigation rates as follows:
• T1 - 6.6 ML per Hectare
• T2: 3.3 ML. per Hectare
• T3: 2.3 ML. per Hectare
• T4: 1.7 ML. per Hectare
• T5: 0.6 ML. per Hectare
(Dch oI the treDtPents consisted oI fiYe Yines roZs Zith
the measurement instrumentation placed in the center of
Measuring water stress in
grapevines through the use of
thermal diffusivity and vapor
pressure deficit sensors
Measuring soil and plant water
status to provide decision support in
irrigated agriculture is on the brink of
a considerable breakthrough, with the
development of robust and reliable field
sensors being made available to growers