| Remember These Drought Management Strategies During the Rest of the Summer |
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 Pasture & Range: July 2005 Other Pasture & Range Articles |
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by Hugh Aljoe |
Generally, about 70 percent of the annual forage production for warm-season perennial forages in southern Oklahoma and North Texas will have occurred by early July. The amount of rain in April and May often determines whether or not it's a good or poor production year. Spring 2005 was one of the driest springs on record for most of the Noble Foundation's service area (a 100-mile radius of Ardmore, Okla.). At Ardmore, rainfall from March through May was 4.03 inches, with 1.88 inches coming during the last five days of May. The 104-year rainfall average for Ardmore over this time period is 12.06 inches. Unless we have an atypically wet summer, many producers will be forced to implement some drought management strategies, if they have not already. Here are a couple of topics to keep in mind looking forward to the remaining summer.
Have a drought management plan in place for your operation. Hopefully, you will never have to impose it. However, the more aggressively stocked you are, the greater the probability you will actually have to use it. Drought plans have elements of de-stocking, relocating and perhaps feeding of livestock. Know and understand the economic ramifications of each alternative, as well as potential long-term effects on the forage resources. Keep in mind that introduced pasture like bermudagrass can withstand and recover from overgrazing much easier and quicker than good native pastures. It is always best to plan for and maintain a minimum amount of residual plant material, regardless of the circumstances.
Manage the use of potentially problematic forage grasses such as the toxic endophyte-infected fescue and the sorghum-sudan type grasses. These are usually good forages, but, as summer progresses, they do have the potential to cause management problems for livestock.
Toxic endophyte-infected fescue is an excellent forage during the cool-season months. However, in late spring, as plants develop stems and seedheads and as temperatures rise, levels of endophyte are at concentrations that can cause health problems (reproductive failure, general unthriftiness, elevated body temperatures, poor blood circulation to extremities) if consumed at significant levels. It is best to remove cattle from these areas or at least have access to alternative forages where they can dilute their fescue intake. If it's necessary to utilize the fescue, you can mow pastures, removing much of the old growth and stems and seedheads and allowing cattle to graze new growth.
Sorghum-sudan type grasses pose different management issues. Nitrates and prussic acid, both of which can be deadly, can accumulate in these grasses. Tests can be conducted for both to determine presence and amount, but a negative test does not mean that the pastures are free of nitrates or prussic acid. The Noble Foundation can test forages for nitrates but not prussic acid. Fortunately, prussic acid dissipates from the plant tissues if cut for hay. This is not the case for nitrates.
 Johnsongrass |  Tall fescue |
The best means for managing nitrate accumulation is to match nitrogen fertility to moisture conditions. For example, if you fertilized Haygrazer or johnsongrass this spring based on the moisture conditions at the time, you would have applied 50 units of nitrogen or less. In a good moisture year or under irrigation, you would be applying 70 units or more. Regardless, sample pastures prior to grazing or haying to determine levels of nitrates. Assuming that nitrates are not an issue (you have had adequate moisture and growth for the amount of nitrogen applied), but conditions are anticipated that would contribute toward prussic acid accumulations, graze cattle on the pasture prior to drought conditions and maintain their access to the fields constantly. Cattle appear to be more tolerant of prussic acid if they are in constant exposure to it as levels increase. It is the cattle that are suddenly exposed when prussic acid has accumulated in the plant tissues that seem to be at the greatest risk.
More information about drought management, nitrates and prussic acid, is available on the Noble Foundation's Web site, www.noble.org, under the Agricultural Division section.