Crop Coefficients & Evapotranspiration: Implications for the

farmers of BekkaValley, Lebanon

The BekkaValley

•75 miles X 10 miles

•80% of Lebanese Agriculture

Outline

• Water Problems

• Tal Amara Research Station

• Experimental Methods

• Sunflowers

• Results from other studies

• Conclusion

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

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)

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)

Penman Montieth is used to calculate potential evapotranspiration

Data from weather station (ambient weather data @ 10-min intervals) exported to excel file (ie. Dry air density, vapor pressure)

Graph of Bekaa Valley ETp-PM (mm/day) for sunflowers

Experimental Plot

Reference crop– Rye grass (Lolium perenne)

Experimental crop•2,200 sq. m.•Soybean, corn, sunflowers, wheat

Drainage Lysimeter to Measure ET

www.rtdf.org

General Schematic (may vary in different locations)

Entrance to lysimeter in Bekka Valley

Boundary Layer Effect

2 x 2 x 1.2 cu

Sunflowers

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)

•Control

•Well irrigated crop (C)

Drip irrigation can provide precise

volumes under controlled pressure

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)

Results of study

•0.3 @ crop establishment

•0.9 @ late crop development

•>1 @ flowering stage

•<1 @ seed maturity

Average Kc values

Show crops consumptive water use over growing season, needed for sustainable irrigation planning in Bekaa Valley.

Results of study

These seeds can be used in consumer products such as cooking oil

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

Water use efficiency

increased

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

Often, water issues are viewed as…

A rural African problem…

thewaterproject.org

Or macroscopically…

thewaterproject.org

Each country has a unique government, climate and culture which governs water management there…

Views that are in disaccord with reality

http://www.idrc.ca/

ReferencesKaram, 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

Questions