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What's the Effect of Nitrogen Rate and Timing of Application on Stockpiled Bermudagrass?

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Posted Aug. 31, 2004

Feeding hay through the winter accounts for a large portion of the costs associated with cow-calf production. Forage management strategies to lengthen the grazing season and reduce hay consumption could be beneficial in increasing profitability. Bermudagrass (Cynodon dactylon) is used extensively throughout southern Oklahoma and north Texas for spring/summer grazing and hay production. However, stockpiling bermudagrass for livestock consumption in late fall and winter has not been thoroughly evaluated in our region. Bermudagrass has a high production potential, it is extremely responsive to nitrogen fertilizer and has good grazing tolerance. Late summer and fall rainfall patterns in southern Oklahoma and north Texas, along with added nitrogen fertilization, should provide the potential for excellent bermudagrass production to be used as dry-standing forage well into the winter. At the Pasture Demonstration Farm (Ardmore, Okla.) in 1982, Wadell Altom and Jerry Rogers reported crude protein levels as high as 13 percent in mid-October when 50 pounds of nitrogen per acre was applied in late August. The forage protein values reported above should be adequate to support a pregnant, non-lactating mature cow to at least January 1, annually. In addition, fall fertilized bermudagrass forage with a high nutritive value should be able to support growing animals from September through October prior to grazing winter pasture. A study was initiated to evaluate the effect of N rate and timing of application on forage yield and the crude protein content of fall stockpiled bermudagrass.

Materials and Methods
Location: Noble Research Institute Red River Research and Demonstration Farm, Burneyville, Okla.
Treatments: N Rates = 0, 50, 100, 150 lbs. per acre
Application Dates = 8/20, 9/1, 9/15, 9/30, 10/15

Plot management:

  1. 100 lbs. N/ac applied in the spring for hay production.
  2. P and K applied as needed from soil test.
  3. Hay in June and mow to a 3-inch stubble height prior to first treatment in August.
  4. Dry-matter yield was measured by harvesting 10 days after the first killing frost.

A sample was taken every 15 days from the first harvest date to evaluate forage quality into winter (4-6 samples collected depending on forage availability).

Results and Discussion
Even though this study did not define an exact application date or rate of nitrogen, it was revealing in several areas. First, it was observed that the date of application had no influence on yield in any of the four years. Second, three of the four years showed a linear response to applied nitrogen. This simply means that forage yield increased as nitrogen rate increased as noted in Figure 1.

It is important to note the low yields in 2000. This was due to high air temperatures and no rainfall in early September. The rains finally came in October, but it was too late to make a difference in 2000. In 2001 through 2003, fall weather was ideal for grow-ing bermudagrass. Air temperature was favorable, and rainfall was timely beginning in late August to early September. As a result, forage yields were tremendous. Third, we learned that forage quality (reported as percent crude protein) was affected by both nitrogen rate and date of application in 2001 and 2002. As noted in Figure 2, percent crude protein was high enough to support a pregnant, nonlactating cow without any additional protein supplementation through the month of December.

The first harvest date is the average date of the initial harvest for the four years of the study. Crude protein averaged over 10 percent and increased with increased nitrogen rates as expected. Last, we learned that drystanding bermudagrass continues to hold its quality well into the winter. Typically, the two driest months in our region are December and January. As a result, percent crude protein remained well above the National Research Council's (NRC) spring calving cow's requirement until February when a rain, ice or snow event occurred.

It is obvious that weather has the largest influence on both yield and quality of fall stockpiled bermudagrass. However, it is interesting to find that no matter the nitrogen rate or time of application, simply by starting with a 3-inch stubble height in August, applying some rate of nitrogen fertilizer by mid September, and deferring grazing until late fall or first frost, more than a ton of bermudagrass can be produced. Using this forage management method will lengthen the grazing season at least through December replacing hay feeding and as a result lower your winter feed bill.

For example, a rule of thumb often followed when feeding hay is a bale of hay per head per month. If true, it would require a 1,200-pound bale fed at 80 percent efficiency to support a 1,200-pound cow for one month. To replace this bale of hay with stockpiled bermudagrass, it will require 1,600 pounds of drystanding forage per acre grazed with at least 60 percent harvest efficiency. Unlimited access to stockpiled bermudagrass often results in lower harvest use efficiencies. Applying 50 pounds of nitrogen per acre will easily produce more than the needed 1,600 pounds of dry matter forage per acre (assuming adequate growing conditions). Even with today's fertilizer prices, it is still more economical to apply 50 pounds of nitrogen per acre than to feed a bale of hay.