Transcript Agricultural Weather Station - CIHEAM,Istituto Agronomico

IMPROVING WATER USE EFFICIENCY OF FIELD CROPS
THROUGH REGULATED DEFICIT IRRIGATION
Fadi Karam
Lebanese Agricultural Research Institute
Department of Irrigation and Agro-Meteorology - Tal Amara (http://www.lari.gov.lb)
Kamal Karaa
Litani River Authority
Department of Rural Development – Beirut – Lebanon
Nazir Tarabey
Association of Irrigation Water Users in South Bekaa Scheme – Lala - Lebanon
WASAMED – International Conference on “Water Saving in Mediterranean Agriculture &
Future Research Needs”, IAMB, Bari, 14-17 February 2007
Efficiency
Is the ratio OUTPUT
INPUT



Irrigation efficiency (Ei)
Agronomic water use efficiency (WUEa)
Physiological water use efficiency (WUEp)
Agronomic water use efficiency (WUE)
WUEg,b (kg m-3)
=
YIELD OR BIOMASS
(kg m-2)
EVAPOTRANSPIRATION
(1 kg m-3 = 1 g m-2 mm-1)
Subscripts g and b indicate grain yield and biomass
(m3 m-2)
Water saving approach
Develop new irrigation scheduling, not
necessarily based on full crop water
requirement, but one designed to ensure
the optimal use of allocated water: Partial
irrigation
Deficit Irrigation


DI or RDI is one way of maximizing water use
efficiency (WUE) for higher yields per unit of
irrigation water applied.
The crop is exposed to a certain level of water
stress either during a particular growth period or
throughout the whole growing season, without
significant reduction in yields.
Objectives


Increase WUE of a crop by eliminating
irrigations that have little impact on yield.
Yield reduction may be small compared with
the benefits gained through diverting the saved
water to irrigate other crops.
YIELD RESPONSE TO WATER


Yields increase with water
availability in the root zone,
until a saturation level, above
which there is little effect.
Yield response curve of specific
crops depends on weather
conditions and soil type as well
as agricultural inputs.
EXPERIMENTAL PLAN




Maize, a determinate species with a limited
capacity to adjust grain yield in response to water
availability (Karam et al, 2000; 2003);
Soybean, an indeterminate species with a high
capacity to compensate the effects of early water
stresses (Karam et al., 2005);
Cotton, an indeterminate species with a larger
capacity to adjust the number of dehiscent bolls
under stressful conditions (Karam et al., 2006);
Sunflower, a determinate species with a single
inflorescence and an aptitude to tolerate
moderate water stresses (Karam et al., 2007).
Irrigation treatments
Crop
Corn
Period Treatment Period of irrigation cutout
1998- I-100
No irrigation restriction
1999 I-80
80% of soil replenishment
I-60
80% of soil replenishment
Soybean
2000- C
No irrigation restriction
2001 S-1
Irrigation cutout at full bloom (R2)
S-2
Irrigation cutout at seed enlargement (R5)
S-3
Irrigation cutout at mature seeds (R7)
Cotton
2001- C
No irrigation restriction
2002 S-1
Irrigation cutout at first open boll
S-2
Irrigation cutout at early boll loading
S-3
Irrigation cutout at mid boll loading
Sunflower 2003- C
No irrigation restriction
2004 S-1
Irrigation cutout prior to flowering stage
S-2
Irrigation cutout at mid flowering stage
S-3
Irrigation cutout at the beginning of seed
formation
S-4
Irrigation cutout at mid seed ripening
SOIL-WATER BALANCE
Dynamic-oriented Process
 
t2
t1
t
 R0     Drdt  
t2
t1

z 0 t
z
Where t2–t1 is the time interval over which measurements are made,
zo is the soil surface and z is the depth to the lowest point of
measurement and  is the volumetric soil water content.
ACTUAL SOIL MOISTURE CONTENT
t 
INup  ( INlow  Ta )
RD
t
t is actual moisture content of the root zone at time step t (cm3 cm-3)
INup is rate of net influx through the upper root zone boundary (cm d-1)
INup = P + Ie – Es + SSt/ t - SR
INlow is rate of net influx through the lower root zone boundary (cm d-1)
INlow = CR - Perc
Ta is actual transpiration rate of crop (cm d-1)
RD is actual rooting depth (cm); P is precipitation intensity (cm d-1)
Ie is effective daily irrigation (cm d-1); Es is soil evaporation rate (cm d-1)
SSt is surface storage (cm); SR is rate of surface runoff (cm d-1)
CR is rate of capillary rise (cm d-1); Perc is percolation rate (cm d-1)
t is time step (cm d-1); Zt is depth of groundwater table (cm).
SOIL WATER CONTENT
z2
T   A  z
z1
A = Root Absorption
Z = soil depth
o
9- v-0
D 3
19 ec-0
-D 3
29 ec-0
-D 3
ec
8- -03
Ja
18 n-0
-J 4
a
28 n-0
-J 4
an
7- -04
Fe
17 b-0
-F 4
e
2 7 b -0
-F 4
e
8 - b -0
M 4
18 ar-0
-M 4
28 ar-0
-M 4
a
7- r-04
A
17 pr-0
-A 4
27 pr-0
-A 4
p
7- r-0
M 4
17 ay-M 0 4
2 7 ay -M 04
ay
6- -04
Ju
16 n-0
-J 4
un
-0
4
29
-N
Rain, ETp (mm)
Rain (mm)
ETP (mm)
SW (I-0)
60
50
Days after sowing
SW (I-50)
70
I-0 (7.5 mm)
I-50 (7.5 mm)
I-100 (7.5 mm)
I-100 (50 mm)
300
40
(PWP)
200
30
100
20
0
10
-100
0
-200
Soil water content (mm)
Soil Water Balance
SW (I-100)
500
(FC)
I-50 (50 mm)
I-100 (50 mm)
400
SOIL WATER MONITORING AND MEASUREMENTS
CAPACITANCE PROBE
DISADVANTAGES






The system requires highly qualified technicians for installation
and maintenance and highly qualified personnel for running the
system i.e. farmer by himself cannot use the system.
Very expensive system
System fragile and subject to vandalism.
Can be affected by climate adversity (flooding, heavy rain, etc)
Radio transmission can be affected by nature barrier or
geographical relief
Problems of data discontinuity or delaying due to radio or other
tele-communication interference
Soil moisture measurement


Method of measurement:
TDR (Time Domain
Reflectometry)
Frequency: before and
after irrigation supplies, at
30 cm increment in the 0120 cm of soil depths.
Weighing Lysimeter (ETcrop)
ET measurements (Hourly
and Daily)
Location (middle of the Exp.
field)
Area (4  4 m²)
Depth (1 m)
Weight (22000 kg)
Watered at 30% of SWD
Linked to a weight indicator
Weight loss recorded (4
times/hr; 94
readings/day)
Rye-grass drainage Lysimeters (ETrye-grass)
ET measurements (3-to-4 day
interval)
Location (middle of the Exp.
field)
Area (2  2 m²)
Depth (1 m)
Watered at 30% of SWD
ET = I – D ± Q
(Q = 0 when irrigation is
frequent)
METHODOLOGY




First year
ETref (Rye-grass
drainage lysimeters)
ETcrop (weighing or
drainage lysimeters)
Kc = ETcrop/ETref



Second year
ETref (Rye-grass
drainage lysimeters)
ETcrop = ETref x Kc
Climatic-Water Balance: FAO Penman-Montheith
   900 ea  ed  
0.408Rn  G   

T

273


ETo 
   1  0.34  U 2 
ETcrop = ETo × Kc
1.2
Reproductive phase
1
Kc
0.8
0.6
0.4
0.2
Grain fi lling phase
Vegetative phase
S owing
Harvest
0
Days after sowi ng
ETo FAO-PM vs. ETrye-grass
2001 grwing period
1:1
14.0
ETp FAO-PM (mm/day)
12.0
10.0
8.0
6.0
4.0
y = 0.8321x + 1.5567
R2 = 0.785
2.0
0.0
0.0
2.0
4.0
6.0
8.0
10.0
ETrye-grass (mm/day)
12.0
14.0
Daily and Seasonal Evapotranspiration
ETcum
mm
mm per day
ETm
d.a.s
Daily ETm, ETo and Kc
ETo-grass
.
.
.
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.
.
.
.
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mm per day
ETm
.
.
.
.
.
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d.a.s
Kc
Kc-grass
Kc-FAO vs. kc-grass
Y= .
X+ . (r = .
;n=
)
Line
.
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Kc FAO
.
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Kc grass
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:
Soybean (2000-2001)
10000
4000
9000
3500
8000
3000
2500
Biomass (t/ha)
Seed Yield (t/ha)
7000
2000
1500
y = 1.5797x + 2005.3
6000
5000
4000
y = 6.1554x + 3087.7
R2 = 0.3924
3000
R2 = 0.0494
1000
2000
500
1000
0
0
0
100
200
300
400
500
ET (mm)
600
700
800
900
0
100
200
300
400
500
600
700
800
900
ET (mm)
(Karam et al., 2005; data points are means of five quadrates of 1m2 each per treatment)
Results are a kind of database for the
country




Corn seasonal ET reached on the lysimeter 952 mm in 1998 and 920
mm in 1999. Grain-related water use efficiency (WUEg) varied in corn
treatments from 1.34 to 1.88 kg m-3, while at biomass-basis (WUEb)
the values varied from 2.34 to 3.23 kg m-3.
Soybean seasonal ET totaled 800 mm in 2000 and 725 mm in 2001.
Seed-related water use efficiency of soybean (WUEs) varied from 0.47
to 0.54 kg m-3, while WUEb varied from 1.06 to 1.16 kg m-3.
Cotton, seasonal ET was 641.5 mm in 2001 and 669.0 mm in 2002.
Average WUEl values varied among treatments from 0.43 to 0.64 kg
m-3, while WUEb varied from 1.82 to 2.16 kg m-3.
Sunflower, average across years of evapotranspiration attained 672
mm. WUEs of sunflower varied among treatments from 0.76 to 0.87 kg
m-3, while at biomass-basis WUEb varied from 3.46 to 4.1 kg m-3.
Concluding remarks
Improvement of water use efficiency requires information
on water consumption by the crop
Use of modern irrigation methods can result in less water
losses
More experiments are needed with respect to different
agro-climatic zones.