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Critical dates help decision-making

by Wyoming Livestock Roundup

With the prospect of drought in the coming years, Area Rangeland Management Specialist for USDA Natural Resources Conservation Service Dwayne Rice noted that producers must be prepared to make the difficult decisions necessary to keep their operations functioning.

“Using trigger dates and monitoring forage production can help to make decisions,” commented Rice.

Trigger dates

“Trigger dates are simply tools,” clarified Rice. “They are supposed to be used to help managers adapt to variations in rainfall season by season, and certainly year by year.”

Because scientists understand that rainfall and effective moisture drives the major part of production in forage systems. Effective moisture, he explained, is the moisture that gets through the soil surface, become useful for plant growth.

Rice noted that trigger dates were developed and have been tested numerous times, though the true extent of the capabilities is yet to be seen.


“We have noticed that March, April and May precipitation drives April, May and June production,” Rice commented, adding that the grass that results in June is also dependent on heat, rates of transpiration and wind, as well as numerous other environmental factors.

He further added that precipitation arriving later in the summer has less of an impact on grass production.

“The production curve doesn’t respond as favorably to precipitation that happens in July,” he said. “That precipitation is important for the next year’s growth.”

Rice continued, “July precipitation helps the grasses to finish the season – they start putting energy back into the root crown and for reproduction. If we don’t finish the season well, the production line may be steep and it will peak lower.”

For example trigger dates, Rice said that April 15, June 15 and July 1 are important for making decisions. 

Recharging the soil

He also noted that taking into account soil moisture recharge is also important.

“We have to look at the past 12 to 24 months to ask how the pasture finished the growing season and did you leave enough standing residue,” said Rice. “Coming out of March and into April, is there enough grass or mulch to protect the soil? If we start getting rain, can it get through the soil surface to become effective precipitation instead of just rain?”

These questions, said Rice, allow the producer to determine if soils will be recharged with water to begin a good growing season. Also looking at the previous two year’s precipitation helps producers to establish if the soil is recharged. 

Late growth

Rice noted that the next area of importance is the late part of the growing season in September to November.

“If the grasses are short, like they were here last year, there is going to be little crown energy stored, so the plants are going to come out with less energy, and I would expect them to be not be as vigorous,” he said. 

Then during the winter, Rice noted that it is important at maintain at leas 800 pounds of residue to protect soil surface.

“Once we get into the longer term droughts, any residue on the soil surface is good – whether it is cool season, annual or perennials,” he said.

Maintenance of residual litter on the ground is important for collection of future moisture, though it isn’t easy. 

New year

“Once the November through April 1 decision is made, we are going to look at our initial stocking decisions,” explained Rice. 

If less than four inches of effective moisture has been received since November, Rice noted that he reduces stocking rates by at least 10 percent. Reductions are made by weight, said Rice, rather than by number. 

At the June 15 trigger date, Rice noted that 75 percent of the annual precipitation has occurred, but only about 50 percent of forage production has occurred. 

“In this case, if our precipitation for Nov. 1 through June 15 is less than 80 percent, we plan to reduce by 30 percent by weight,” said Rice.

In a situation similar to last year, where green-up occurred early, Rice noted that the phenology curve moves forward by two to four weeks, and producers must adjust their trigger dates forward to compensate.

Another big date is the July 15 date. By that point, approximately 75 percent of grass production occurred, and if rains come, it will not affect grass growth.

“Even if it starts raining, we will not get a catch-up growth in forage. The plants will grow, but they can’t catch up in forage production,” he explained. “They want to get into the reproductive stage as quickly as possible.”

Measuring the biomass may not show much of a loss, but forage production is lower.

“By July 15, we need to start making some serious decisions,” he commented.

Finally, looking at Aug. 15, Rice noted that producers should begin to look at how much grass is available going into winter.

“We are still looking to try to keep minimum residue on the ground for next spring and soil surface protection,” Rice commented. “We’ve also got to start thinking about how the pastures are going to recover, how fast they will recover and how we can get back in the ball game as a rancher.”

Developing dates

In order to develop trigger dates, Area Rangeland Management Specialist for USDA Natural Resources Conservation Service Dwayne Rice marked several important factors that need to be considered.

“As a producers, you will need to know you historic monthly average precipitation,” he said, “and you can get that data at the National Weather Service’s website.”

He also noted that forage phenology data is also important.

“Forage phenology looks at when the grass grows and how much of it grows,” Rice explained. “Most of the time, Extension or your local NRCS can help you develop that, considering different types of forages, different elevation and different pastures where the phenology curves might be different.”

Lastly, Rice noted that ranchers must understand their operation’s average sustainable carrying capacity.

“The trigger dates only work if you are properly stocked,” he added. “The only way to be properly stocked is to have a grazing plan and understand what your carrying capacity is.”

Rice presented in a webinar hosted by the National Drought Mitigation Center on Feb. 27. Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at 

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