Management of desalinated water for irrigation of peppers Plant response to salinity and...

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)


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)


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)


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)


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.

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



0.0 .5 1.0 1.5 2.0

Rel

ativ

e d

rain

age

0.0

.3

.6

.9

1.2


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


0.0 .5 1.0 1.5 2.0

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0



0.0 .5 1.0 1.5 2.0

Rel

ativ

e d

rain

age

0.0

.3

.6

.9

1.2


0.0 .5 1.0 1.5 2.0

Lea

chin

g f

ract

ion

0.0

.2

.4

.6

.8


0 5 10 15 20 25

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0

A B

C D


0.0 .5 1.0 1.5 2.0

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0



0.0 .5 1.0 1.5 2.0

Rel

ativ

e d

rain

age

0.0

.3

.6

.9

1.2


0.0 .5 1.0 1.5 2.0

Lea

chin

g f

ract

ion

0.0

.2

.4

.6

.8


0 5 10 15 20 25R

elat

ive

yiel

d0.0

.2

.4

.6

.8

1.0

A B

C D



0.0 .5 1.0 1.5 2.0

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0



0.0 .5 1.0 1.5 2.0

Rel

ativ

e d

rain

age

0.0

.3

.6

.9

1.2


0.0 .5 1.0 1.5 2.0

Lea

chin

g f

ract

ion

0.0

.2

.4

.6

.8


0 5 10 15 20 25

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0

A B

C D


0.0 .5 1.0 1.5 2.0R

elat

ive

yiel

d0.0

.2

.4

.6

.8

1.0



0.0 .5 1.0 1.5 2.0

Rel

ativ

e d

rain

age

0.0

.3

.6

.9

1.2


0.0 .5 1.0 1.5 2.0

Lea

chin

g f

ract

ion

0.0

.2

.4

.6

.8


0 5 10 15 20 25

Rel

ativ

e yi

eld

0.0

.2

.4

.6

.8

1.0

A B

C D


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

Management of desalinated water for irrigation of peppers Plant response to salinity and...

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