Wednesday, October 01, 2014

Managing Drought Risk on the Ranch

Management Priorities After Drought

Rangeland after prolonged drought.
Image: Pat Reece.

1. Restoring hyrologic condition

Restoring hydrologic condition is the number one priority, especially in semiarid areas. The efficiency of precipitation is reduced until enough ground litter and standing plant material occur to optimize infiltration and minimize evaporation. It is especially important to accomplish this objective before thunderstorms are most likely to occur.

Considerable variation in surface conditions may exist among pastures. Priority should be given to pastures with fine-textured soils and long slopes where runoff is most likely to occur.

Effective management could vary from a 2-week delay from traditional turnout dates to a full year of nonuse.

2. Restoring Plant Vigor

The second priority is restoring plant vigor, especially in species most preferred by livestock. This requires uninterrupted and relatively rapid plant growth.

Length and frequency of growing-season nonuse periods needed to restore and maintain relatively high levels of plant vigor decline as annual precipitation and/or yield per inch of average annual precipitation increase.

The primary effect of drought stress and grazing stress is reduced belowground plant growth. Root and rhizome growth are proportional to top growth. Production and retention of photosynthetically active foliage is critical for maximum belowground growth.

The only way to improve vigor when pastures are grazed season-long every year is to change the season(s) of grazing or periodically rest a pasture. Leo Merrill developed a 4-pasture, 3-herd grazing system in Texas to accomplish this objective. Cattle are divided into 3 herds, each placed in 1 of 4 pastures for year-long grazing. Each pasture receives 1 year of rest every 4 years. Where rangelands are not grazed year-long, delaying spring turnout by 2 to 4 weeks will increase the amount of current-year herbage and reduce grazing pressure on preferred plant species.

Where deferred-rotation or rest-rotation grazing is in place, adequate growing-season deferment can be provided to every pasture during 3 to 4-year cycles. The likelihood of accomplishing this objective in semiarid regions increases when the length of the grazing season extends well beyond the end of the growing season. If pastures are grazed only once per season, late-used pastures would receive full growing-season deferment.

In areas with high enough annual precipitation to sustain multiple grazing periods, individual pastures may be skipped during 1 or more grazing cycles to enhance plant vigor. When average annual precipitation is greater than 25 to 30 in, removing all livestock in July will maintain relatively high vigor in most plant species even when pastures are double stocked from spring greenup to July during non-drought years.

Animal Production Objectives

If drought induced the sale of livestock and the income is exempt from state and federal taxes, a 1-year extension or progressive restocking would enhance rangeland recovery.

Additionally, livestock marketing plans can influence vegetation recovery after drought.

Economic success of enterprises that sell growing livestock off grass is closely linked to achieving near maximum possible average daily gains. These enterprises favor relatively high levels of plant vigor in semiarid areas because stocking rates must be relatively low to optimize average daily gains during a 4-month grazing season.

In contrast, retained ownership of growing cattle after grazing may result in relatively high summer stocking rates because recovery of compensatory gain in the next phase of production can enhance overall profitability. These enterprises will likely need to use rest-rotation grazing and/or delay spring turnout to maintain relatively high vigor in preferred plant species in semiarid regions.


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