Appendices - Soils for Fine Wines - page 258

Irrigation Requirement under Drip Irrigation Table A10.3

Diameter (m) of
Wetted Soil

Volume of Water Volume of Water

Volume for a
Wetting Depth of

per Vine (L) for a
Wetting Depth of

(ML) per ha for a
Wetting Depth of

Vine by
row spacing

No. of
vines

(m m) per ha 0.4 m 0.6 m 0.4 m 0.6 m 0.4 m 0.6 m

K s 0.02 m/hr
1

2

5,000 0.57 0.66 5.2 10.1 0.026 0.051

3

1.5 2,222 0.57 0.66 5.2 10.1 0.011 0.022

K s 0.04 m/hr
1

2

5,000 0.46 0.52 3.3 6.4 0.017 0.032

3

1.5 2,222 0.46 0.52 3.3 6.4 0.007 0.014

The effects of these soil properties are quantified by a formula (Dasberg and
Or, 1999) for calculating the diameter d of wet soil, for a given depth of wetting,
as follows:

zq

0.33

d 1.32 (A 10.1)

K s
where z is the depth of wetting required, q is the irrigation rate, and K s is the sat-
urated hydraulic conductivity. Note that the diameter of wet soil increases as K s
decreases. The d value is obtained by substituting appropriate values for z , q , and
K s in equation A10.1. The depth of wetting is determined by the depth of the
main fibrous root system of the vine. In the following examples, the shape of wet-
ted soil volume V s is assumed to be cylindrical and is calculated as follows:

2
V s z

d

(A10.2)

2
The volume of water required for RDI is then the product of V s and DAW . For
this soil example ( DAW 0.05 m 3 /m 3 ), with two possible K s values, the volume
of water required has been calculated assuming one dripper per vine (4 L/hr) for
two depths of wetting and two vine spacings. The results are given in table A10.3.
An increase in K s causes the diameter of wetted soil to decrease for a given
depth of wetting, which means that the volume required per vine for a particular
RDI is decreased; also the quantities of water required would be doubled if there
were two drippers per vine. Note that the water required per ha to achieve a de-
sired RDI is less under drip irrigation than by microjets, and much less than un-
der overhead sprinklers or flood irrigation.

Irrigation Schedule Using Weather Data
and Crop Coefficients for a Vineyard
in Southeastern Australia

Appendix 11

The aim is not to stress the vines from bud burst to fruit set ( SWD kept within
the RAW range), but to apply some stress from fruit set to veraison ( SWD kept