management of desalinated water for irrigation of peppers plant response to salinity and...
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Management of desalinated waterfor irrigation of peppers
Plant response to salinity and implicationsregarding blending strategies
מים מותפלים לחקלאות בערבה – היבטים אגרונומיים ויישומייםמים מותפלים לחקלאות בערבה – היבטים אגרונומיים ויישומיים07/10/200807/10/2008
Alon Ben-GalAgricultural Research Organization
Gilat Research Center
Why use desalinated water for irrigation?
• Better plant growth• Reduce leaching requirements
– Higher yields with less water– Less negative environmental impact
(sustainability)
Lysimeters Yotvata
2 seasons
9 salinity levels
3 water (leaching fraction) levels
Determination of Eta, drainage water quantity and salinity, biomass production and yields
Ben-Gal A., Ityel E., Dudley L., Cohen S, Yermiyahu U, Presnov E, Zigmond L, Shani U. (2008) Effect of irrigation water salinity on transpiration and on leaching requirements: A case study for bell peppers. Agric. Water Manag. 95, 587-597.
Greenhouse experiments Zohar and Yair stations
Desalinated water (EC = 0.4-0.5 dS/m)
Saline water (EC=2.5-3.2 dS/m)
Blended water (30% saline; EC=1.35 dS/m)
Under experimental conditions: sandy loam soil and high evaporation demand– irrigation water salinity causes reductions in transpiration and subsequent reductions in vegetative growth starting within 1 month of planting
Ben-Gal et al., 2008. Agric. Water Manag.
Relative water application (leaching fraction) influences response – increased leaching maintains lower soil solution salinity)
Ben-Gal et al., 2008. Agric. Water Manag.
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6
Rel
ativ
e yi
eld
(Y
/Ym
ax)
Irrigation water EC (dS/m)
peppers - arava
1.1
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6
Rel
ativ
e yi
eld
(Y
/Ym
ax)
Irrigation water EC (dS/m)
peppers - arava
0.8
1.1
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6
Rel
ativ
e yi
eld
(Y
/Ym
ax)
Irrigation water EC (dS/m)
peppers - arava
0.8
1.1
1.3
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6
Rel
ativ
e yi
eld
(Y
/Ym
ax)
Irrigation water EC (dS/m)
peppers - arava
0.8
1.1
1.3
2
I/ETp
Shani, U., Ben-Gal, A. Tripler E. and Dudley, L.M. (2007) Plant Response to the Soil Environment: An Analytical Model Integrating Yield, Water, Soil Type and Salinity. Water Resources Res. Vol. 43, No. 8, W08418 10.1029/2006WR005313.
Ben-Gal et al., 2008. Agric. Water Manag.
Blending as a strategy to save water and nutrients?
3 years of data from experiments in Zohar station
Relative irrigation water applied (I ETp-1)
.5 1.0 1.5 2.0
Sat
ura
ted
pas
te
elec
tric
al c
on
du
ctiv
ity
(dS
m-1
)
0
1
2
3
4
0
DW 2004-5DW 2005-6BW 2006-7GW 2004-5GW 2005-6GW 2006-7
GWBWDW
Month
09 10 11 12 01 02 03 04 05 06
Ref
eren
ce e
vap
ora
tio
n (
mm
d-1
)
0
2
4
6
8
10
12
2004-05 2005-06 2006-07
Ben-Gal A Yermiyahu U and Cohen S. (2008) Fertilization and blending alternatives for irrigation with desalinated water. J Environ. Quality. In press.
Rel
ativ
e fr
uit
yie
ld
0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative irrigation water applied (I ETp-1)
0.0 .5 1.0 1.5 2.0
Rel
ativ
e sh
oo
t b
iom
ass
0.0
.2
.4
.6
.8
1.0
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0R
elat
ive
yiel
d0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e d
rain
age
0.0
.3
.6
.9
1.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Lea
chin
g f
ract
ion
0.0
.2
.4
.6
.8
Salt load (ton NaCl ha-1 season-1)
0 5 10 15 20 25
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
A B
C D
Ben-Gal et al. (2008) J Environ. Quality. In press.
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2
Rela
ive
yiel
d (Y
/Ym
ax)
Relative irrigation water (I/ETp)
0.4
3.2
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2
Rela
ive
yiel
d (Y
/Ym
ax)
Relative irrigation water (I/ETp)
0.41.353.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e d
rain
age
0.0
.3
.6
.9
1.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Lea
chin
g f
ract
ion
0.0
.2
.4
.6
.8
Salt load (ton NaCl ha-1 season-1)
0 5 10 15 20 25
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
A B
C D
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e d
rain
age
0.0
.3
.6
.9
1.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Lea
chin
g f
ract
ion
0.0
.2
.4
.6
.8
Salt load (ton NaCl ha-1 season-1)
0 5 10 15 20 25R
elat
ive
yiel
d0.0
.2
.4
.6
.8
1.0
A B
C D
Ben-Gal et al. (2008) J Environ. Quality. In press.
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e d
rain
age
0.0
.3
.6
.9
1.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Lea
chin
g f
ract
ion
0.0
.2
.4
.6
.8
Salt load (ton NaCl ha-1 season-1)
0 5 10 15 20 25
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
A B
C D
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0R
elat
ive
yiel
d0.0
.2
.4
.6
.8
1.0
מותפליםמהוליםמליחים
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Rel
ativ
e d
rain
age
0.0
.3
.6
.9
1.2
Relative applied irrigation water
0.0 .5 1.0 1.5 2.0
Lea
chin
g f
ract
ion
0.0
.2
.4
.6
.8
Salt load (ton NaCl ha-1 season-1)
0 5 10 15 20 25
Rel
ativ
e yi
eld
0.0
.2
.4
.6
.8
1.0
A B
C D
Ben-Gal et al. (2008) J Environ. Quality. In press.
Conclusions (I)
• Irrigation water salinity needs to be evaluated in terms of:
• reduced crop yields• direct cost of additional water needed to
leach salts• indirect environmental costs of leaching
Conclusions (II)• For the relatively salt-sensitive pepper crop grown in an arid region, reducing salinity from EC 3.20 dS m -1 to
EC 0.40 dS m-1 by reverse-osmosis desalination was found to increase maximum yields by almost 50% while allowing a reduction of the applied irrigation water to half of that with the saline water.
• However, the cost of fertilizing in order to re-supply Ca, Mg, and S minerals removed during the desalination process (in our case some $3,500 ha-1) must also be considered.
• Pepper yields from irrigation with blended water containing 70% desalinated and 30% saline water could be maintained at greater than 90% of those with fully desalinated water, but only if irrigation rates were increased by at least 50%.
• The blending strategy for providing mineral nutrients can therefore consume up to 40% more desalinated water than the fertilization strategy.
• The environmental cost of the increase in irrigation-water salinity from an EC of 0.40 dS m-1 (desalinated water) to an EC of 1.35 dS m-1 (blended water) is substantial, as it involves the loading (into the soil) and leaching (beyond the root zone) of five times more salt, and potentially escalates the transport of other contaminants out of the root zone as well