Can Peak-LAI be used as an appropriate index to estimate wheat performance under weed competition?

1. 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.

2. Middle East

3. 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

4. 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

5. Weeds in wheat crop compete with the crop for nutrients, water, and light as with other crops.

6. Weeds are more competitive when moisture is limiting and especially under drought situation; when young wheat does not compete well with weeds.

7. 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.

8. So, why control? - Crop competition - Prevent economic loss - Hosts for insects and diseases

9. Weeds infesting wheat in Iran Grass weeds Phalaris minor Avena fatua Lolium rigidum Secale cereale Hordeum spontaneum

10. Weeds infesting wheat in Iran Broadleaved weeds Sisymbrium officinale Eruca sativa Cirsium arvense Sinapis arvensis Galium aparine

11. Weed management strategies Identify weed, life cycle, habitat Integrated weed management Preventive Physical Cultural Biological Chemical

12. Enhancing crop competitiveness is one of the promising approaches toward IWM and toward decreasing herbicide consumption.

13. Factors affecting weed competition: - Timing of emergence √ - Growth form - Weed density - Duration of competition √ - Physiological basis of competition

14. 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

15. 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?

16. Materials and methods Site description: 8 field experiments at two locations in 2003-2004. Locations: Karaj 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 Varamin 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

17. 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

18. Materials and methods

19. Materials and methods

20. 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.

21. MeasurementsDAP (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 > 1 : Able to suppress weeds Grain yield (weedy) R = Grain yield (weed-free) 0.90 < R < 1 : Able to tolerate weeds

22. Results Significant differences were observed in the yielding ability of the wheat cultivars in competition with different weed species.

23. Results Wheat - Wild oat

24. Results Wheat - Rye

25. Results Wheat - Flixweed

26. Results Wheat - Rocket

27. 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

28. Results Peak-LAI Tabasi Roshan

29. Results Peak-LAI Azadi Niknejad

30. Results Peak-LAI Karaj2 Mahdavi

31. Results Peak-LAI Shiraz Pishtaz

32. Results Grain yield vs. Peak-LAI (Weed-free) Biomass vs. Peak-LAI (Weed-free)

33. Results Grain yield vs. Peak-LAI (Weedy) Biomass vs. Peak-LAI (Weedy)

34. 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.

35. Thank you all for your attention.