Nutrient management crucial in alfalfa crop

Experts on alfalfa production recognize the growing season challenges many growers face this year and recommend producers continue to use sound practices that yield results.

From late to May, broadcasting fertilizer to boost production is justified if nutrient deficiency is detected by leaf tissue testing or visual symptoms, said Alex Rocateli, an associate professor of forage systems at Oklahoma State University, when he was asked what growers can do in mid- to late-May to boost production for the entire season.

“Take a soil test to determine the amount of fertilizer needed. Top-dress fertilizer right after a harvest to avoid contact with wet foliage,” Rocateli said. “If the recommendation is to apply more than 500 pounds per acre of total material, split the application to prevent salt damage. Apply half of the fertilizer after the most recent harvest and the remainder after the next harvest.”

Another specialist, Bruce Anderson, an emeritus forage Extension specialist with the University of Nebraska-Lincoln, said growers need to harvest at full bloom, which is when every alfalfa shoot has at least one bloom opening.

“This is earlier than when the field looks like every bloom has opened,” Anderson said. “During first growth, alfalfa plants sometimes do not bloom as regularly as they do during midseason.”

If delayed bloom is suspected, inspect the crowns of the alfalfa plants, he said. If new shoots have begun to grow from the crown, harvest as soon as possible because these new shoots are the start of the second growth. Further delay risks cutting off these second growth shoots, forcing plants to start regrowth all over again.

Growers also have to focus on additional cuttings in 2023 and so preparation has to be taken into account, the experts said.

Weed population

Growers will need to watch weed population and control it properly to improve yield and quality, Rocateli said. Some herbicide options, such as imazethapyr and terbacil, can be applied right after first cutting in late April or early May. Imazethapyr is a good option for controlling non-ALS-resistant pigweed, while terbacil is a better option for controlling grassy summer weeds. Glyphosate can be used in Roundup Ready alfalfa; however, it will not be effective on glyphosate-resistant weeds, such as horseweed, marestail and pigweed, he said.

Producers should contact their local agriculture educator for specific herbicide recommendations. In Oklahoma they can access, he said and added that growers need to always follow herbicide labels for proper use and harvest or grazing restrictions.

Don’t start too early

Anderson said growers should not cut plants before they are ready. During drought or high temperatures, alfalfa plants often begin to bloom earlier than usual. This can mislead growers into thinking that the plants have recovered sufficiently from the previous cut and are ready to be cut again, he said.

During drought or high temperatures, acute recovery is slower because plants are stressed by these environmental conditions, Anderson said, adding that instead of being ready to cut in 30 days, it may take 35 to 40 days or more of recovery before plants are ready to be cut.

Roctaeli said producers may harvest the field if a drought hits when the stand regrowth is over 10 inches and flowering. “To be conservative, waiting for 100% alfalfa bloom is highly recommended, ensuring the crowns are completely replenished with energy to survive the drought and regrow when conditions improve.”

Alfalfa grows new shoots from the crown so it is very important not to damage the crown when cutting, he said. Grazing is not recommended because it can damage the crown and that reduces the opportunity of regrowth when environmental conditions improve.

Producers should not harvest the field if a drought hits when the stand regrowth is less than 10 inches, even though the stand is flowering, Rocateli said.

"Cutting alfalfa stands when a drought hits at an early vegetative stage (plant height less than 10 inches) will seriously damage the stand,” Rocateli said. “At this point the crown reserves are meager and it is necessary to maintain all stems and leaves in the field for all their nutrients to be translocated to the crowns.”

By following that plan, alfalfa has enough energy to survive the drought, he said. If a cut is performed at that stage, chances are the stand will be drastically reduced or ultimately die. Also, the plant will start to flower prematurely when a drought hits.

His advice is to let the starving crowns store all canopy nutrients. While that advice helps growers with established stands, extra precautions are needed for new alfalfa seedings when a drought occurs. He says with new alfalfa seedlings do not harvest when a drought hits if the grower has expectations for the stand to survive.

Other management practices are also important, Rocateli said. It is tempting to bypass weed control during a drought. “Why would I spend money with herbicides in a field that I will not be profiting from?” is often asked.

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Unfortunately, this mindset can compromise the following year’s alfalfa yields quality. Weeds are well adapted to extreme weather conditions. They will continue growing during a drought. This continuous weed growth will extract the already limited soil water and produce seeds. As a result, the weed pressure will be much higher in the following years.

That translates into more herbicide usage in the future, he said.

Fertilizer is a different story

During a drought, Rocatelli said growers should avoid applying phosphorus and potassium. “The broadcast P and K will not get into the soil solution if the soil is already dry and rainfall is on the radar.” He said the biggest beneficiaries could wind up being weeds.

“Good P and K fertilization at spring green-up or after the drought (when good growing conditions resume) are essential to stimulate root growth development and carbohydrate storage in the crowns and increases the odds of stand survival,” he said.

Anderson said before drought stress is the best time as he noted that it takes moisture for the fertilizer to work.

Planning ahead

Proper long-term management is the best way to prepare an alfalfa stand for drought, he said. Adequate fertilization, weed control and cutting schedules will prepare a stand for tougher periods.

“The truth is well-managed alfalfa pastures are more resilient to adverse conditions, such as drought, and will recover much faster,” he said.

Anderson said thinking long term pays off. “Actions that may be helpful today have serious long-term consequences.”

Roctali said growers can look to information to help them. In his state they can access the Agronomic Calendar for Oklahoma Alfalfa Growers at Another good source is the Oklahoma Forage Pasture Fertility Guide and is available at

Other aspects

When it comes to prairie hay, Anderson said maximum protein and energy yield generally occurs at early heading. In a mixed species prairie where heading dates differ among species, Anderson said judgment is needed as to when early heading is reached by the dominant species.

“Since only one cut is expected, it may be better to cut a little late than too early to achieve optimum tonnage,” Anderson said.

Dave Bergmeier can be reached at 620-227-1822 or [email protected].