Download - Can Peak-LAI be used as an appropriate index to estimate wheat performance under weed competition?
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
- Has an arid climate in which most of the relatively scant annual precipitation falls from October through April
Iran
- One of the only countries in the world which has the complete four seasons.
- Yearly precipitation averages 25 centimeters or less:
Less than 10 centimeters in the Central Plateau; More than 100 centimeters in the Caspian Coastal Plain
- The most important winter cereal grown in Iran
- Area under cultivation: 6.2 mha
- Annual production: 14.5 mt
- Ranks second after maize in the world cereal output
Wheat:
Introduction
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.
Weeds are one of the most important factors that reduce the wheat yield in Iran.
Reported wheat yield loss in Iran due to weeds: 30%
So, why control?
- Crop competition
- Prevent economic loss
- Hosts for insects and diseases
Weeds infesting wheat in Iran
Grass weeds
Avena fatua Phalaris minor
Secale cereale
Lolium rigidum
Hordeum spontaneum
Weeds infesting wheat in Iran
Broadleaved weeds
Eruca sativa Sisymbrium officinale
Sinapis arvensis
Cirsium arvense
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 developmentHeightLeaf areaPlant growth rate
Distinct competitive advantage
Rapid growthLonger period of initial growthTallDense canopyGreater 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
Latitude: 35°50’Longitude: 50°01’
Elevation: 1020 maslClimate: Semi-aridAnnual precipitation: 250 mmAnnual long-term temperature: 14°CSoil: Clay loam
Varamin
Latitude: 35°19’Longitude: 51°40’
Elevation: 1320 maslClimate: Semi-aridAnnual precipitation: 240 mmAnnual long-term temperature: 30°CSoil: Sandy loam
Experimental treatments
8 wheat cultivars x 2 weed management strategy (weedy & weed-free)
4 replications
Plot size: 2.4m x 6m
Row spacing: 0.30m
Experimental design: RCBD with factorial arrangement of treatments
Materials and methods
CultivarsYear of releasePlanting density (Grains/m2)
Optimum N (kg/ha)
Tabasi1955250110
Roshan1957250110
Karaj21975325110
Azadi1979325105
Niknejad1995425120
Mahdavi1995375130
Shiraz2000400120
Pishtaz2002400120
Materials and methods
Weed species
(Common name)
Weed species
(Latin name)
Planting density (Plants/m2)
Wild oatAvena fatua120
Common ryeSecale cereale120
FlixweedDescurainia sophia80
RocketEruca sativa80
Materials and methods
Cultural practices
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.
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)
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 oatCultivarsR (Karaj)R (Varamin)
Tabasi0.68c0.77bc
Roshan1.54a0.95b
Karaj20.92b1.17a
Azadi0.86bc0.77bc
Niknezhad0.96b1.29a
Mahdavi0.75c0.73bc
Shiraz0.85bc0.57c
Pishtaz0.74c1.01ab
Wheat - RyeCultivarsR (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
Results
Wheat - FlixweedCultivarsR (Karaj)R (Varamin)
Tabasi0.94b0.63c
Roshan1.30a1.05b
Karaj20.81c1.61a
Azadi0.65d0.98bc
Niknezhad0.73cd1.55a
Mahdavi0.97b1.00b
Shiraz0.74cd1.18b
Pishtaz0.93b1.10b
Results
Wheat - RocketCultivarsR (Karaj)R (Varamin)
Tabasi0.94b1.11bc
Roshan1.30a1.42b
Karaj20.81c1.48b
Azadi0.65d0.80cd
Niknezhad0.68d1.99a
Mahdavi0.97b0.85c
Shiraz0.74cd0.71d
Pishtaz0.93b1.07bc
Results
Common rye is a stronger competitor of wheat than other weed species.
The suppressive ability of the wheat crop not only depends on the cultivar but also to the weed species.
The wheat cultivars’ response to the weeds differedbetween locations:
Karaj: RoshanVaramin: Niknejad and Karaj2
Results
0
1
2
3
4
5
6
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
Tabasi
0
1
2
3
4
5
6
7
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
Roshan
Peak-LAI
0
1
2
3
4
5
6
7
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
Results
Azadi Niknejad
Peak-LAI
Results
Karaj2 Mahdavi
0
1
2
3
4
5
6
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
0
1
2
3
4
5
6
7
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixw eed(Free)
Flixw eed(Infested)
K V
Peak-LAI
Results
Shiraz Pishtaz
0
1
2
3
4
5
6
7
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Wild oat(Free)
Wild oat(Infested)
Rye (Free) Rye(Infested)
Rocket(Free)
Rocket(Infested)
Flixweed(Free)
Flixweed(Infested)
K V
Peak-LAI
Results
y = -301.08x + 5690.7
R2 = 0.1087
0
1000
2000
3000
4000
5000
6000
7000
0 1 2 3 4 5 6 7 8
y = 1517.2x + 10426
R2 = 0.2457
0
5000
10000
15000
20000
25000
30000
0 1 2 3 4 5 6 7 8
Grain yield vs. Peak-LAI)Weed-free(
Biomass vs. Peak-LAI)Weed-free(
Results
y = -101.49x + 3970.9
R2 = 0.016
0
1000
2000
3000
4000
5000
6000
7000
0 1 2 3 4 5 6 7
y = 1428.9x + 11597
R2 = 0.2241
0
5000
10000
15000
20000
25000
30000
35000
0 1 2 3 4 5 6 7
Grain yield vs. Peak-LAI)Weedy(
Biomass vs. Peak-LAI)Weedy(
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.