Saturday, November 01, 2014

Managing Drought Risk on the Ranch

Grazing Systems: Rotation Grazing Alternatives

Benefits of rotation grazing accrue when these systems are used during the years before drought. Moderate stocking rates in conjunction with rotation grazing will improve plant vigor and range condition.

 

Rest-Rotation Grazing

These grazing systems were initially developed to improve range condition by resting one or more pastures for a minimum of one year. Rest-rotation is also used to enhance wildlife habitat especially for ground-nesting birds. The diagram at the right depicts a 6-pasture rest rotation. Two pastures are rested each year. When rested, each pasture is not grazed for two full years to optimize the quality of nesting cover.

Historically, stocking rates in grazed pastures were increased to compensate for non-use in the rested pasture(s). If stocking rate is increased in the remaining pastures to offset non-use in the rested pasture(s), higher cumulative grazing pressure is expected to reduce animal performance in the last one or two pastures grazed each year compared to other rotation systems.

In contrast, use of light to moderate stocking rates in grazed pastures is likely to result in relatively high levels of animal performance and enhanced vegetation response to rest-rotation systems. Additionally, increased levels of residual herbage in the rested pastures are likely to provide longer-lasting benefits for wildlife species that benefit from high levels of plant cover.

 

Deferred-Rotation Grazing

Efficient deferred-rotation grazing systems generally include four to eight pastures with one grazing period per season in each pasture and moderate stocking rates.

Year to year changes in the order in which pastures are grazed, pasture-use sequences, can be used to maintain high levels of vigor in preferred plant species, improve range condition and enhance the recovery of disturbed areas.

Distribution of grazing is likely to become more uniform when cross-fencing reduces diversity of range sites within pastures and distance to water is reduced.

Advanced plant maturity in the last pasture(s) under deferred-rotation may reduce animal performance late in summer grazing seasons compared to season-long continuous or intensively managed grazing.

Deferred-rotation grazing systems are well suited for seasonal rotation especially with cow-calf enterprises. Dormant-season and growing-season use can be rotated among pastures over years where logistically feasible.

Inadequate protection from winter storms, readily available crop residue for winter grazing, or short-term livestock ownership plans may reduce the feasibility of dormant season grazing.

 

Intensively Managed Grazing

These systems involve a wide range in number of pastures, from five to more than 60, and generally high concentrations of livestock for multiple, short-duration grazing periods in most or all pastures each year. Another phrase used to describe this type of grazing plan is "rotational grazing."

Based on economic and ecological efficiency, the optimum number and size of pastures depends on the production environment and plant species.

Rates at which fence and water investments can be recovered decline as forage production potential declines. Additionally, risk of reducing current-year and subsequent-year herbage production with heavy defoliation increases as average precipitation or site productivity decline. 

Relatively efficient intensively managed grazing systems on irrigated perennial grass in the central and northern Great Plains involve 4 to 6 pastures with 22 to 30 days of deferment between grazing periods.

The size of pastures used by ranchers on rain-fed sites are generally much larger compared to irrigated or sub irrigated sites. As the long-term average precipitation declines below 22 inches, the need for longer growing-season deferment and the need to graze pastures no more than once during the growing season increase. 

The relatively large number of pastures often used on rangeland for these systems provides opportunities for accomplishing individual pasture management objectives. Grazing plans can be designed to alter stocking rates and dates or provide full growing-season deferment or rest in selected pastures.

Consistently placing high concentrations of cattle in semi-arid rangeland pastures when preferred plant species normally grow rapidly can cause measurable reductions in the vigor of key species. Relatively high levels of grazing pressure and numerous decisions of when to begin and end grazing in individual pastures require a high level of commitment to monitoring and management.

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