Agriculture Reference
In-Depth Information
Table 6.3.
Crop parameters affecting the evapotranspiration of edible alliums (from Allen
et al.
, 1998).
Maximum
Depletion
rooting
fraction for
K
a
Cmid
depth
b
(z
r
, m)
RAW
c
(p)
d
Crop species
Height (m)
K
Cend
K
CBinit
K
CBmid
K
CBend
Garlic 0.3
1
1.00 0.70 0.15 0.90 0.60 0.3-0.5 0.3
1
Bulb onion 0.4
1
1.05 0.75 0.15 0.95 0.65 0.3-0.6 0.3
1
Green onion 0.3
1
1.00 1.00 0.15 0.90 0.90 0.3-0.6 0.3
1
Seed onion 1.05 1.05 0.80 0.15 1.05 0.70 0.3-0.6 0.35
a
All the K values apply to a temperate sub-humid climate with a minimum RH of 45%, a mean RH of 70% and moderate windspeeds
averaging 2 m/s at 2 m height.
b
The larger values of z
r
are for soils with no restriction to rooting and apply to water-stressed or rainfed crops; the smaller values are
appropriate for irrigation scheduling.
c
RAW is the 'readily available water' fraction of water in the soil at field capacity. When water is depleted below RAW, K
CB
is reduced
by a stress factor K
S
(see Eqns 6.11 to 6.14).
d
The p values apply to a medium-textured soil at ET
0
, approximately 5 mm/day.
Formulae to adjust K and p values for different climatic conditions are given in the text.
