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Effective alfalfa irrigation requires a thoughtful plan

by Wyoming Livestock Roundup

Riverton – University of Wyoming Extension Specialist Caleb Carter asked attendees of the annual Fremont County Farm and Ranch Days if they were prepared to endure another hot, dry year, such as 2012. 

Carter, along with other industry professionals, presented a variety of topics to educate farmers and ranchers in and around Fremont County, and Carter specifically looked at raising and irrigating forages for maximum production.

The nature of alfalfa 

“Alfalfa is a cool-season, perennial plant,” Carter explained. “This makes irrigating it different and more complicated than other annual crops.

Carter said, “When we find ourselves in drier-than-normal conditions, we need to prioritize tasks and establish long-term goals.”

He explained since alfalfa is a cool-season plant, it becomes the most stressed in the summer and does not utilize water effectively during this time. This is a critical consideration during drought conditions. 

“Simply, perennials come back every year,” he said. “When we are making decisions on how to go about irrigating, this is something we have to keep in mind.”

“Alfalfa yields have a very direct correlation with water applied,” Carter said. “We need to be sure when we are irrigating to pay attention to the consistency of water output.”

Consistency is key

“Due to the perennial nature of alfalfa, the implications of inconsistent water can be seen for years to come,” Carter explained. “It’s so important to understand the output of an irrigating system and fix any issues.”

“Small leaks add up over time,” he said. “If we have parts that aren’t spraying enough and some that are over-spraying, it will affect yields in the end.” 

He suggested ensuring we have a uniform nozzle package to ensure uniform water application. 

“We want to consider our flow rate, water pressure, pivot capacity and acreage,” he says. “Understanding the extent and limitations of our systems will help in creating a consistent, effective plan for irrigating alfalfa.” 

Planning for irrigation 

“In times of drought, we have to create goals and stick with them,” Carter said. “We have to consider field health and water availability.”

“First, we need to determine if max yield or longevity is the goal,” he noted. “There are times when both these goals are appropriate, but we must evaluate fields on an individual basis to determine which is more appropriate. 

He explained in the case of fields with less fertile or older plants, maximum yield is the more logical goal. 

“If we have older or less fertile fields that need to be replaced soon regardless, we should go ahead and get the most we can out of them and water appropriately,” Carter said. 

He commented in fields with younger, more fertile plants, longevity should be the goal. 

“If we have fields that are still very young and fertile, we want those plants to last as long as they can,” he said. “It’s unlikely they were in the rotation to be replaced if they are still producing well.” 


“Once we establish our goals, we need to look at how we’re going to achieve them,” Carter stated. “We have to understand the ‘red zone’ of plant moisture. Once plants are in the red zone with too little moisture, they will become extremely stressed.”

He explained, in drought situations, farmers have a choice between a limited irrigation strategy and utilizing a deficit irrigation plan. 

“Limited irrigation can be problematic,” he explained. “It consists of spreading the small amount of water we have over a period of time.” 

Carter commented utilizing limited irrigation would generally decrease yields over time and should be done with caution. 

“The deficit irrigation technique utilizes strategic timing,” he said. “When we use deficit irrigation, we are only watering plants when their needs are the highest and they can best utilize water.” 

He explained alfalfa is most efficient in water usage in the spring and fall. These times would be the best to water under a deficit strategy because the plant will waste less water than in seasons such as summer or winter when it is under stress or dormant.  

Callie Hanson is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to

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