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Is Now the Time to Fertilize Bermudagrass?

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James Locke

By James Locke
Planned Consultation Manager and Senior Soils and Crops Consultant

Posted Jul. 31, 2011

It is near the end of the 2011 growing season, fertilizer prices are high and we are suffering severe drought conditions. Why would anyone consider fertilizing bermudagrass or other warm-season grasses now? There are good reasons to consider a late summer or early fall fertilization program, namely to extend the grazing season and improve the quality of available forage. Of course, unless the drought breaks, rainfall - not fertility - will be the limiting factor, so added fertilizer would not help. However, even if we don't get additional production this fall, much of that fertilizer will still be available next spring.

In the Noble Research Institute's Oklahoma and Texas service area, we usually have 90 to 110 growing days from Aug. 1 until our first hard freeze. Additionally, if you look at Carter County, Okla., as the middle of the service area, we average about 11 inches of rainfall from August through October. With proper fertilization and adequate moisture, there is enough time to produce more than 2,000 pounds dry matter per acre. Although I am not advocating baling hay in October, the old adage "Make hay while the sun shines" seems appropriate.

To get the best quality and growth response from late summer nitrogen, the grass should be grazed or hayed to a 3-inch stubble height by at least the middle of August. Fifty to 75 pounds actual nitrogen per acre plus phosphorus and potassium as indicated by soil analysis should be applied by Sept. 1. Either rainfall or irrigation will be necessary to move the nitrogen into the soil and sustain forage growth. Unfortunately, without favorable weather we will not get the growth we expect. Within reason, farmers and ranchers must be optimistic and have faith that they will receive adequate rainfall.

We assume at least 20 pounds additional dry matter will be produced per pound of nitrogen, so 50 pounds of nitrogen will produce at least 1,000 pounds dry matter, more than what would have grown without fertilizer. This fertilized forage should have 12 to 15 percent crude protein content instead of the 8 to 10 percent expected without fertilizer. Nitrogen cost (for 46-0-0) is approximately 58 cents per pound of nitrogen, so 50 pounds actual nitrogen costs $29. At that price, the nitrogen cost per ton of the additional forage is $58.

Once the forage is produced, a decision has to be made on how best to use it. The most common method is to stockpile the forage as a standing hay crop and graze it after frost. Depending on weather conditions, stockpiled bermudagrass can maintain excellent quality into January. Test the standing forage just as you would hay in order to determine if supplementation is needed to meet nutrient demands. Another option is to graze stockers on the freshened forage until annual winter pasture is ready to graze. This can fill a forage production gap when many producers put calves on full feed or hay.

Regardless of how the forage is used, implementing a strip grazing system that only allows access to two or three days' worth of grazing at a time may increase utilization efficiency. If cattle are allowed access to larger areas, significant losses can occur due to trampling and animal waste. Although we want to make cattle consume most of the forage, monitor body condition and behavior to ensure that dry matter intake is not limited. If you note that body condition is slipping or that cattle have to work all day to eat their fill, either increase the size of the strip or allow them earlier access to the next strip.

With drought conditions across most of the southern United States, hay is in short supply and expensive. This, coupled with high commodity prices driving up the cost of feed, means we need to find affordable alternatives wherever we can. Look at your operation and consider if fertilizing warm-season pastures in late summer or early fall is a fit. If so, now is the time to start. For additional information on management strategies before, during and after drought, refer to the Noble Research Institute publication Drought Management.