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Beefs and Beliefs

Drought tool you need now is critical rainfall dates

Ryan_H_Photos-iStock-Thinkstock Cows on droughty pasture
Plan for drought destocking by learning relationships of your forage growth to rainfall pattern.

A big part of the Great Plains is sub-par for moisture this winter and I've heard rumblings about drought planning and destocking already.

It's a good time to be planning, but in most areas its far too early to destock.

One of the key components to help you make the destocking decision is called critical rainfall dates. I wrote several years ago these are "the absolute core information needed to develop an effective drought-management plan." I still believe this is true, as these can help you know whether you have enough rainfall (and soil moisture) to grow the forage you need for the year.

It is important to know what to expect relative to your average rainfall, or a similar moisture level you choose. Data recorded from tracking precipitation with the use of rain gauges placed strategically across your ranch should be used to determine what will be your "trigger" rainfall amounts relative to these critical dates, which are usually about halfway through your forage-growing season.

For example, Kansan Ted Alexander explained to us many years ago that on his predominantly warm-season-grass ranch, slightly west of south-central Kansas, he and son Brian have four critical dates:

  • April 1
  • June 15
  • August 15
  • November 1

His use of these dates is actually pretty complex, and can be viewed on this page, but generally April 1 is the start of the growing season and lower moisture triggers management changes. June 15 is their midpoint and so will trigger destocking according to how short the moisture is. August 15 signals about 90% of their production is through, and can trigger earlier destocking of remaining stocker cattle if rainfall is at certain low levels. November 1 is the end of the growing season and low rainfall for the year can signal the beginning of a drought for the next growing season. Be sure and read the Alexanders' plan, as it is a masterful use of this technology. There are other examples on the website, as well.

The National Drought Mitigation Center at the University of Nebraska-Lincoln, has some good information on how to calculate a plan for critical rainfall and growth dates. Use this link.

At your location, you'll need to understand the forage mix of cool-season to warm-season and the primary growth spring season, which is surprisingly short. In my home in north-central Oklahoma, agronomists have long said about half the warm-season forage is in place by June 15, and getting additional rain after that point will not grow as much leaf material as it will stems and seeds. This is about a 120-day primary growth season, but the bulk of the growth comes in 45-60 days centered around that June 15 date.

If you have a relatively even amount of warm and cool-season forage, you might need critical dates for both growing seasons -- one for the earlier spring flush of cool-season growth and one for the rapid summer growth of warm-season forages.

Of course, introduced forages are different from native mixtures, and growth patterns and growth curves vary north to south and east to west.

Typically, the critical date is early in the growth season because there needs to be moisture in place for the first half of the big forage growth curve.

The dates and rainfall amounts you decide upon will become the trigger points of a drought plan by which your management decisions will be made. In addition, precipitation data gained from sources like SNOTEL and the Western Regional Climate can be used to help you. Information of plant growth-curves for many range sites can be self developed or may be available through the National Resources Conservation Service’s Web Soil Survey.

Further, if you have built up your soil and forage quality by controlled grazing you should have much better resiliency, but hopefully also you'll have good grazing records to tell you how much production you've been able to graze from the various paddocks on your ranch.


The Jan. 4 drought monitor map shows moderate or worse drought across a major portion of the US, but it's winter. Learn how to plan now in case real drought strikes.

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