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Effect of Simulated Grazing Intensity on Dual-Purpose Winter Wheat Growth and Grain Yield
Dillon Butchee and Jeff EdwardsDepartment of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK
Introduction• Approximately 50% of the 2.4 million hectare Oklahoma wheat crop
will be grazed by stocker cattle.• Many farmers will choose to remove cattle from wheat pasture in late
winter and harvest a grain crop (dual-purpose). • In a dual-purpose wheat production system, grazing intensity can
range from high to low. Grazing intensity affects wheat canopy closure, and canopy closure influences yield potential of wheat after grazing. This study evaluates the effect of mid-season canopy closure on final grain yield.
Objectives1. Determine the relationship between wheat canopy closure and grain
yield2. Evaluate the impact of simulated grazing intensity on winter wheat
grain yield3. Determine if plant growth habit (planophile or erectophile) affects
crop response to simulated grazing intensities
Materials and Methods • Overley (erectophile growth habit) and Fuller (planophile growth
habit) wheat were sown in a RCBD at 120 kg/ha on 21 September 2009 at Stillwater, OK.
• Grazing intensity was simulated using a rotary mower set to clip plots at 3, 7.5, or 12 cm. The mower included a bagging unit to catch clippings.
• Simulated grazing began 5 November 2009 and ended 5 March 2010.• Canopy closure was determined before and after each mowing
treatment using digital photography analysis (SigmaScan Pro V 5.0) and at Feekes Growth Stage 10.5 with a line quantum sensor.
• Plots were harvested 22 June 2010 with a small plot combine.
Image 1. Light interception measurements made by digital photography analysis.
Conclusions• Fractional canopy closure values were lowest throughout the growing
season for the most intense simulated grazing treatment (3cm) and increased as simulated grazing intensity decreased.
• Grain yield had an asymptotic response to fractional canopy closure measured at grazing termination.
• There was a large decrease in grain yield when fractional canopy closure at flowering fell below 0.9. Overley had lower canopy closure values for all simulated grazing regimens but produced grain yield equal to or higher than that of Fuller.
• Intensifying simulated grazing from a 7.5-cm mowing height to a 3-cm mowing height reduced yield of Overley by 42% and Fuller by 22%.
For more informationDillon ButcheeGraduate Student / Department of Plant and Soil SciencesOklahoma State [email protected]
Figure 4. Grain yield of cultivars at each mowing treatment. Columns with the same letter are not significantly different at the 0.05 level.
3 7.5 12 control0
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Fuller
Overley
Mowing Height (cm)
Gra
in Y
ield
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1)
aa
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cdcdde
e
Figure 3. Average fractional canopy closure at Feekes Growth Stage 10.5 of each cultivar at each mowing treatment. Canopy closure measured by a line quantum sensor.
3 7.5 12 none0.0
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ctio
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y C
losu
re
Figure 1. Average canopy closure for each mowing height. Canopy closure of all plots decreased during winter dormancy, but the decrease was much greater for more intensively grazed plots.
11/5/2009
11/24/2009
12/14/2009
2/15/2010
3/5/2010
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Image 2. Stillwater location after simulated grazing treatments on 5 March 2010.
Figure 2. Relationship between 5 March 2010 canopy closure of both cultivars and final grain yield.
