Can Peak-LAI be used as an
appropriate index to estimate
wheat performance under
weed competition?
Saeid Soufizadeh, Eskandar Zand, Mohammad Ali Baghestani,
Mohammad Bannayan, Reza Deihimfard
Dept. of Agronomy, Faculty of Agriculture, Tarbiat Modares University, Iran.
Middle East
Iran
- One of the only countries in the world which has
the complete four seasons.
- Has an arid climate in which most of the
relatively scant annual precipitation falls from
October through April
- Yearly precipitation averages 25
centimeters or less:
Less than 10 centimeters in
the Central Plateau;
More than 100 centimeters in
the Caspian Coastal Plain
Introduction
Wheat:
- Ranks second after maize in
the world cereal output
- The most important winter
cereal grown in Iran
- Area under cultivation: 6.2 mha
- Annual production: 14.5 mt
Weeds in wheat crop compete with the crop for
nutrients, water, and light as with other crops.
Weeds are more competitive when moisture is
limiting and especially under drought situation;
when young wheat does not compete well with
weeds.
Reported wheat yield loss in Iran due to weeds:
30%
Weeds are one of the most important factors
that reduce the wheat yield in Iran.
So, why control?
- Crop competition
- Prevent economic loss
- Hosts for insects and diseases
Weeds infesting wheat in Iran
Grass weeds
Avena fatua
Phalaris minor
Lolium rigidum
Secale cereale
Hordeum spontaneum
Weeds infesting wheat in Iran
Broadleaved weeds
Eruca sativa
Sisymbrium officinale
Cirsium arvense
Sinapis arvensis
Galium aparine
Weed management strategies
Identify weed, life cycle, habitat
Integrated weed management
Preventive
Physical
Cultural
Biological
Chemical
Enhancing crop competitiveness is
one of the promising approaches
toward IWM and toward decreasing
herbicide consumption.
Factors affecting weed competition:
- Timing of emergence
√ - Growth form
- Weed density
- Duration of competition
√
- Physiological basis of competition
Weed competition affecting by growth form:
Root development
Height
Leaf area
Plant growth rate
Distinct competitive advantage
Rapid growth
Longer period of initial growth
Tall
Dense canopy
Greater leaf area
Our aim:
To asses the competitive ability of the Iranian
wheat cultivars released within different eras
in response to weeds.
Our research question:
Can Peak-LAI be used as an appropriate and
easy-to-measure index to estimate wheat
performance under weed competition?
Materials and methods
Site description:
8 field experiments at two locations in 2003-2004.
Locations:
Karaj
Varamin
Latitude: 35°50’
Longitude: 50°01’
Elevation: 1020 masl
Climate: Semi-arid
Annual precipitation: 250 mm
Annual long-term temperature: 14°C
Soil: Clay loam
Latitude: 35°19’
Longitude: 51°40’
Elevation: 1320 masl
Climate: Semi-arid
Annual precipitation: 240 mm
Annual long-term temperature: 30°C
Soil: Sandy loam
Materials and methods
Experimental treatments
Experimental design: RCBD with factorial arrangement of treatments
8 wheat cultivars x 2 weed management strategy
(weedy & weed-free)
4 replications
Plot size: 2.4m x 6m
Row spacing: 0.30m
Materials and methods
Cultivars
Year of release
Planting density
(Grains/m2)
Optimum N
(kg/ha)
Tabasi
1955
250
110
Roshan
1957
250
110
Karaj2
1975
325
110
Azadi
1979
325
105
Niknejad
1995
425
120
Mahdavi
1995
375
130
Shiraz
2000
400
120
Pishtaz
2002
400
120
Materials and methods
Weed species
(Common name)
Weed species
(Latin name)
Planting density
(Plants/m2)
Wild oat
Avena fatua
120
Common rye
Secale cereale
120
Flixweed
Descurainia sophia
80
Rocket
Eruca sativa
80
Cultural practices
Planting dates: November 2nd at Karaj.
November 6th at Varamin.
Fertilization: Ammonium phosphate 150 kg/ha
Urea 100 kg/ha (at planting)
Urea 50 kg/ha (at tillering)
Urea 50 kg/ha (at heading)
Irrigation: immediately after planting and
throughout the growing season (no water deficit
symptom occurred).
No need to apply insecticides and fungicides.
All weeds except the target weed species were
effectively controlled throughout the growing season.
Measurements
DAP (Days after planting)
Crop biomass and LAI:
(from stem elongation at two-weeks intervals)
Crop yield & biomass: (at physiological maturity)
Weed biomass: (at crop physiological maturity)
R=
Grain yield (weedy)
Grain yield (weed-free)
R > 1 : Able to suppress weeds
0.90 < R < 1 : Able to tolerate weeds
Results
Significant differences were observed in the
yielding ability of the wheat cultivars in competition
with different weed species.
Results
Wheat - Wild oat
Cultivars
R (Karaj)
R (Varamin)
Tabasi
0.68c
0.77bc
Roshan
1.54a
0.95b
Karaj2
0.92b
1.17a
Azadi
0.86bc
0.77bc
Niknezhad
0.96b
1.29a
Mahdavi
0.75c
0.73bc
Shiraz
0.85bc
0.57c
Pishtaz
0.74c
1.01ab
Results
Wheat - Rye
Cultivars
R (Karaj)
R (Varamin)
Tabasi
-
0.66bc
Roshan
-
0.69b
Karaj2
-
0.63bc
Azadi
-
0.54c
Niknezhad
-
0.74b
Mahdavi
-
0.68b
Shiraz
-
0.44c
Pishtaz
-
0.92a
Results
Wheat - Flixweed
Cultivars
R (Karaj)
R (Varamin)
Tabasi
0.94b
0.63c
Roshan
1.30a
1.05b
Karaj2
0.81c
1.61a
Azadi
0.65d
0.98bc
Niknezhad
0.73cd
1.55a
Mahdavi
0.97b
1.00b
Shiraz
0.74cd
1.18b
Pishtaz
0.93b
1.10b
Results
Wheat - Rocket
Cultivars
R (Karaj)
R (Varamin)
Tabasi
0.94b
1.11bc
Roshan
1.30a
1.42b
Karaj2
0.81c
1.48b
Azadi
0.65d
0.80cd
Niknezhad
0.68d
1.99a
Mahdavi
0.97b
0.85c
Shiraz
0.74cd
0.71d
Pishtaz
0.93b
1.07bc
Results
The suppressive ability of the wheat crop not only
depends on the cultivar but also to the weed species.
Common rye is a stronger competitor of wheat
than other weed species.
The wheat cultivars’ response to the weeds differed
between locations:
Karaj: Roshan
Varamin: Niknejad and Karaj2
Results
Peak-LAI
Tabasi
Roshan
6
7
K
V
K
V
6
5
5
4
4
3
3
2
2
1
1
0
0
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Results
Peak-LAI
Azadi
Niknejad
7
K
V
5
K
V
4.5
6
4
5
3.5
3
4
2.5
3
2
1.5
2
1
1
0.5
0
0
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Results
Peak-LAI
Karaj2
Mahdavi
7
6
K
K
V
6
5
5
4
4
3
3
2
2
1
1
0
0
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Wild oat
(Free)
Wild oat
(Infested)
Rye (Free)
Rye
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixw eed
(Free)
Flixw eed
(Infested)
V
Results
Peak-LAI
Shiraz
Pishtaz
7
K
V
4.5
K
4
6
3.5
5
3
4
2.5
3
2
1.5
2
1
1
0.5
0
0
Wild oat
(Free)
Wild oat Rye (Free)
Rye
(Infested)
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
Wild oat
(Free)
Wild oat
(Infested)
Rye (Free)
Rye
(Infested)
Rocket
(Free)
Rocket
(Infested)
Flixweed
(Free)
Flixweed
(Infested)
V
Results
Grain yield vs. Peak-LAI
Biomass vs. Peak-LAI
(Weed-free)
7000
(Weed-free)
30000
y = -301.08x + 5690.7
R2 = 0.1087
6000
25000
y = 1517.2x + 10426
R2 = 0.2457
5000
20000
4000
15000
3000
10000
2000
5000
1000
0
0
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
8
Results
Grain yield vs. Peak-LAI
Biomass vs. Peak-LAI
(Weedy)
(Weedy)
7000
35000
6000
30000
y = 1428.9x + 11597
5000
R2 = 0.2241
25000
y = -101.49x + 3970.9
R2 = 0.016
4000
20000
3000
15000
2000
10000
1000
5000
0
0
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Conclusion
Investing more biomass in leaf under
Weed-free condition does not seem a good
strategy to increase the wheat yield.
Peak-LAI could be used successfully as an
estimator of the wheat crop under weed
competition along with some other
measures ONLY but not alone.
Thank you all for your
attention.