Grazing Management During and After Extended Drought

By by Dr. Jeff Mosley, Extension Range Management Specialist, Department of Animal & Range Sciences, Montana State University, Bozeman

To me, drought and taxes have a lot in common: they’re both facts of life that must be dealt with periodically; they’re both royal pains in the rear; and they both carry serious consequences if we choose to ignore them.

Most ranch businesses can readily adjust to one or two dry years in a row, and I don’t believe that short-term drought necessitates major changes to most ranch grazing plans. However, three or more successive dry years challenge even the best graziers, and unfortunately, many range livestock producers across our state now face this situation. Besides the immediate concerns about how to feed the livestock, serious drought also stresses the land, often to the brink of change.

Years can pass without much apparent change to seeded pastures and rangelands, but extended drought can cause dramatic shifts in vegetation. The land then remains relatively unchanged until the next environmental trigger occurs. Drought conditions over the last three or four years have created an environmental trigger for Montana’s pastureland and rangeland, and failure to care for the land during this year may create serious consequences for decades to come.

Assess Drought Impact

How much of an adjustment is needed to your ranch grazing plan for Spring and Summer 2001? The answer depends, of course, upon how hard you’ve been hit by drought. The drought has not impacted everyone to the same extent, and even pastures or portions of pastures within one ranch have not been affected equally. Consider these questions to assess drought’s impact:

Were weeds a problem before the drought? If weeds were a problem before the drought, they’ll probably be even worse after drought. Drought stresses all plants, but weeds are usually stressed less than desirable forage plants because most weeds grow earlier in the growing season before soil moisture is fully depleted. Also, weeds are usually grazed less than other plants. When rainfall does occur, weeds are in better shape to respond and they get a jump-start on the desirable plants. Producers need to be especially vigilant about new weed infestations if they brought in hay from new sources this past fall and winter. Inspect areas where the hay was fed and plan to control new infestations this summer - before weeds get well established and before weed control becomes more costly.

Were poisonous plants common before the drought? Poisonous plant problems often worsen during or after an extended drought, especially early in the growing season. Many poisonous plants are "weeds" that survive drought better than desirable forage plants, and many poisonous plants green up early in the season (e.g., low larkspur, death camas, and locoweed). Poisonous plant infestations tend to thicken after serious drought, but toxicity problems can be more common after drought even when poisonous plants don’t increase in density. One reason for increased toxicity problems is that after a dry year there is less (if any) residual carry-over forage from the year before to buffer the toxins. Thus, dietary concentrations can reach toxic levels even when livestock don’t increase their consumption of poisonous plants. A related concern for this spring is grass tetany. Without last year’s residual carry-over grass to buffer the new green growth in the gut, grass tetany becomes more likely and strategic supplementation will be warranted.

When was the area grazed last year? One silver lining about drought years is that much more of the grazing season usually occurs after seeds ripen and when plants are dormant. Plants are more tolerant of grazing during these later stages of plant development, so some plants may have endured less stress from grazing than in normal years. The plants stressed most by last year’s drought were those grazed in early summer, because they were unable to regrow before soil moisture was depleted.

How heavily was the area grazed last year and in previous years? Light or moderate grazing doesn’t harm most plants, nor does heavy (< 60% utilization) or severe use in one year if the plants are given an opportunity to recover. Plants are stressed when heavy or severe use occurs for two or more years in a row. When drought breaks, plants grazed lightly to moderately in the past will recover from drought faster than plants that have been heavily grazed for many years.

Do plants appear stressed this spring? Stressed plants begin growth later and grow slower in spring, and most plants will be stressed after three or four drought years. Consequently, turnout in spring will likely need to be later this year in many areas across our state. The rooting depth of your forage plants and the length of drought in your area can help you judge how long plant growth will be delayed this spring. After one or two dry years, growth usually begins earlier in deep-rooted versus shallow-rooted plants because deep-rooted plants had access to more soil water and were less stressed. After an extended drought, however, deep-rooted plants may rebound slower because they remained green longer into the growing season and probably received extra grazing pressure during drought.

Grazing Strategies

Early planning will enable you to carefully consider potential alternatives for your grazing plan this summer. Waiting to plan until June or July will leave fewer options available. Some potential options include:

Reduce the Amount of Forage Needed

Cull more heavily before the grazing season begins and before the market becomes glutted. Reduce the number of replacements, if possible. Mature cows will survive and reproduce better than young cows or heifers that are still growing.
Wean calves early. Dry cows consume about 35% less forage than lactating cows and 400-lb calves consume about one-third as much as mature cows.

Graze Somewhere Else

Lease additional pasture.
Use tame pastures, especially subirrigated or irrigated ones, more heavily than usual. The improved forage species can tolerate heavy grazing more so than native rangeland, so allocate more of the load to those pastures that can tolerate it best.
Try to graze areas this year that didn’t get much or any grazing use last year. For example, consider areas near reservoirs and springs that went dry last year. These areas may have been grazed less than in a normal year when water is available. Herding, supplemental feeding, hauling or piping water, temporary fencing or shutting off water in over-used areas can all be used to control where livestock graze. Be sure to carefully evaluate the costs and benefits of these practices versus the costs and benefits of reducing livestock numbers.

Adjust the Timing of Grazing

Delay turnout in spring so that forage plants can recover vigor. Delayed turnout will also lessen problems with poisonous plants and grass tetany.
In rotational grazing systems, rotate more frequently.
Consider using any rested pastures and thereby spreading the use this year across all of your pastures.
For early season grazing this year, try to graze any areas that were ungrazed last year or those areas that were grazed after plant dormancy during last summer’s drought.
For late season grazing this year, try to use those areas that were grazed heavily last year before plant dormancy.

Beef: Questions & Answers is a joint project between MSU Extension and the Montana Beef Council. This column informs producers about current consumer education, promotion and research projects funded through the $1 per head checkoff. For more information, contact the Montana Beef Council at (406) 442-5111 or at beefcncl@mt.net