Crop coefficient studies were conducted at the Tal Amara Research Station in Lebanon's Bekka Valley to determine optimal irrigation volumes for sunflowers, soybeans, wheat, and corn. Deficit irrigation experiments on sunflowers found that yield was reduced by 25% during early flowering but only 14% during mid-flowering. Seed yield actually increased with deficit irrigation during seed formation. The studies provide crop water use data and coefficients to inform sustainable irrigation planning for farmers in the water-stressed Bekka Valley region.

1. Crop Coefficients &
Evapotranspiration:
Implications for the
farmers of Bekka
Valley, Lebanon

3. The
Bekka
Valley
•75 miles X 10 miles
•80% of Lebanese Agriculture

4. Outline
• Water Problems
• Tal Amara Research Station
• Experimental Methods
• Sunflowers
• Results from other studies
• Conclusion

5. Water Problems
• Very long and dry summers
– Annual Precipitation: 592 mm
– 95% occurs from March to November
• Water Mismanagement
– Water delivery system is unreliable
– Farmers prefer drilling illegal wells rather than relying
on public delivery system
• Farmer’s education
– Do not adopt drip irrigation
– Are not provided analytical solutions for optimal
irrigation volumes for specific crops

6. Tal Amara Research Station
•Part of a broader movement to
provide water and economic
security to Lebanon
•Experiment in local conditions so
results are more applicable
•To inform farmers about optimal
irrigation volumes during certain
growing seasons
•Experiment on crop for two
growing seasons to determine
optimal irrigation
Experimental plot (and my tour guide)

7. Important Terms
• Crop yield
– Sunflowers produce seeds to be used in consumer
products such as cooking oil
• Growth stage
– For example, sunflowers have an early flowering
stage, mid-flowering stage, and seed formation
• Deficit Irrigation
– Withholding irrigation completely
– Irrigating at a percent of soil moisture deficit (I60)

8. Penman Montieth is used to calculate
potential evapotranspiration
Data from weather station (ambient
weather data @ 10-min intervals) Graph of Bekaa Valley ETp-PM
exported to excel file (ie. Dry air (mm/day) for sunflowers
density, vapor pressure)

9. Experimental Plot
Reference crop Experimental crop
– Rye grass (Lolium perenne) •2,200 sq. m.
•Soybean, corn, sunflowers, wheat

10. Drainage Lysimeter to Measure ET
General Schematic (may vary in different locations)
2 x 2 x 1.2 cu
Entrance to lysimeter in Bekka Valley
Boundary Layer Effect
www.rtdf.org

11. Sunflowers

12. Experimental Parameters (Sunflowers)
•2 growing seasons
•2003: 139 days
•2004: 131 days
•3 growing stages (deficit irrigation)
•F1- early flowering (WS1)
•F2- mid-flowering (WS2)
•M0- seed formation (WS3) Drip irrigation can provide precise
volumes under controlled pressure
•Control
•Well irrigated crop (C)

13. More parameters…
• ETrye-grass = I – Dr +- S
• V = ETcrop x A
– Irrigation volume (V)
– Plot area (A)
• P + I - Dr –R0 –ET +- (Se – Sb) = 0
– Precipitation (P)
– Irrigation (I)
– Drainage (Dr)
– Runoff (R0)
– Soil water content (Se)
– Water content at beginning of same time interval (Sb)

14. Results of study
Average Kc values
•0.3 @ crop establishment
•0.9 @ late crop
development
•>1 @ flowering stage
•<1 @ seed maturity
Show crops consumptive water use over growing season,
needed for sustainable irrigation planning in Bekaa Valley.

15. Results of study
Seed Yields:
Control
5.36 t/ha
WS1
Reduced yield by 25%
WS2
Reduced yield by 14%
WS3
Increased yield to 5.5 t/ha These seeds can be used in
Water use efficiency consumer products such as
increased cooking oil

16. Other studies
Durum wheat
•Supplemental irrigation increased grain number per sq. m. and grain weight
Soybean
•Deficit irrigation (I-60) was profitable in growth stage R7 (late in the
growing season)
Corn
•Not grown before in Bekaa Valley, but studies conclude the Bekka Valley
is a suitable place for corn production

17. Often, water issues are viewed as…
A rural African problem…

18. Or macroscopically…
thewaterproject.org

19. Views that are in disaccord with reality
Each country
has a unique
government,
climate and
culture
which
governs
water
management
there…
thewaterproject.org
http://www.idrc.ca/

20. References
Karam, Fadi. Masaas, Randa. Sfeir, Therese. Mounzer, Oussama. Rouphael, Youssef. 2005.
Evapotranspiration and seed yield of field grown soybean under deficit irrigation conditions. Agricultural
Water Management. Volume 75. pp. 226-244.
Karam, Fadi. Breidy, Joelle. Stephan, Chafic. Rouphael, Joe. 2003. Evapotranspiration, yield and water
use efficiency of drip irrigated corn in the Bekaa Valley of Lebanon. Agricultural Water Management.
Volume 63. pp. 125-137
Karam, Fadi. Lahoud, Randa. Masaad, Randa. Kabalan, Rabih. Breidi, Joelle. Chalita, Claude. Rouphael,
Youssef. 2007. Evapotranspiration, seed yield and water use efficiency of drip irrigated sunflower under
full and deficit irrigation conditions. Agricultural Water Management. Volume 90. pp. 213-223
Karam, Fadi. Kabalan, Rabih. Breidi, Joelle. Rouphael, Youssef. Oweis, Theib. 2009. Yield and water-
production functions of two durum wheat cultivars grown under different irrigation and nitrogen regimes.
Agricultural Water Management. Volume 96. pp. 603-615
AgriMet. 2009. About AgriMet Crop Coefficients. The Pacific Northwest Cooperative Agricultural
Weather Network. Webpage. Accessed: October 27, 2009.
http://www.usbr.gov/pn/agrimet/cropcurves/about_crop_curves.html
Photos: Carter’s Facebook (Water Resources of the Middle East) & Google Images

21. Questions