Manage Forage Before (and During) Drought

by James Rogers

No one wants to hear the word "drought" this time of year, especially after the rains in March. However, Mesonet rainfall data from Sept. 24, 2003, to March 21, 2004, reveals that Oklahoma statewide rainfall is almost 3 inches below normal. If we go back a year, March 23, 2003, to March 21, 2004, statewide rainfall is 6.41 inches below normal. What are rainfall levels going to be like in the remainder of 2004? My sincere hope is that we will be above normal. But are you flexible enough to manage for that unspeakable term … drought?

Drought is a normal part of virtually all climatic zones, and if there is a silver lining to drought, it is this: drought is normal and temporary. Unfortunately, it is a recurring feature of climate and can have broad impact. To manage for the inevitable drought, start with forage selection. Oklahoma ranges in normal precipitation from west to east by about 36 inches of rainfall. Forage moisture requirements and water use efficiency vary as well, and these variations should be taken into account when developing your forage base. Moving from west to east in the state, predominant forages change from range areas completely dominated by native warm-season perennial grasses to areas of more cool-season perennials. Table 1 gives a good indication of why that is. From the data presented, it would be questionable to put tall fescue in a climate with limited rainfall, as it will probably not persist. Warm-season perennials tend to root much deeper than cool-season perennials, allowing them to pull water reserves from deeper in the soil and making them more adapted to drier climates.

Water use efficiency also varies according to species. In Table 2, Coastal bermudagrass and Pensacola bahiagrass require much less water to produce a pound of forage than common bermudagrass. During dry conditions, the plant’s ability to produce that little bit extra will mean more grazing days.

Having the proper forage base for your climate is only one step toward managing for the inevitable drought event. Equally important is having the proper stocking rate based on the amount of forage your property will produce and grazed at the proper utilization rate for the forage species. Combine proper stocking rate with good grazing management, such as a rotation, to eliminate spot grazing and maintain ground cover. Spot grazing will become a weak link during drought, ultimately creating bare spots that are inefficient in capturing rainfall.

Having the ability to recognize that you are on the verge of or in the early stages of drought allows time to plan drought management strategies. Numerous Web sites are available to help monitor short and long-term climate events:

• Oklahoma AgWeather — http://agweather.mesonet.org
• National Drought Mitigation Center — www.drought.unl.edu
• U.S. Drought Monitor — www.drought.unl.edu/dm/
• NOAA — www.noaa.gov.

Once a drought is recognized, don’t abandon rotational grazing. In severe cases, you may have to move to a sod-based sacrifice pasture and feed, but, until then, maintain sound grazing management. This will allow you to:

1. accumulate grazing days ahead of you;
2. maintain or lengthen forage rest periods; and
3. monitor forage residual. Don’t abandon your fertility program.

On introduced forages, you will want to be able to grow grass when moisture is available, and proper fertility will improve their water use efficiency. If you have begun to de-stock, fertility rates may be changed to grow only the amount of grass required.

Monitor animal health and condition score during dry weather events. If emergency forage crops have been planted, be aware of potential toxicity problems with nitrate accumulation and prussic acid. In severe drought, de-stocking may be the only alternative to save your grazing resource. In the July 2003 issue of Ag News and Views, Billy Cook wrote a good reference article on culling strategies during drought.

Remember: drought, though inevitable, is also temporary. After a drought event occurs, carefully rebuild your stocking rate. If it has been a severe event, forage plants have probably been lost and remaining plants are weakened. Implement a grazing plan that will allow for deferment of the most decimated pastures and appropriate rest periods for the forage base.

Management of resources prior to a drought (proper stocking rate and grazing management) will greatly improve your drought tolerance. Once drought conditions are recognized, avoid doing nothing!