Fertilizing pastures

Tanner Schwab applies dry fertilizer to an eastern Iowa pasture. Fertilizing pastures in late-summer and early fall can provide a forage quantity and quality boost.

It’s been a dry summer for some and a wet summer for others, and those moisture levels will likely determine the need for late-summer or fall pasture fertilization.

Daren Redfearn, Extension forage agronomist with the University of Nebraska, says green pastures may not need that late-season boost, especially if they have a good mixture of warm-season grasses.

Pastures with a mix of brown and green could benefit from at least a nitrogen application.

“You are taking some risk that you’ll get some rain, but even if you don’t, most of the nitrogen will still be there in the spring and it won’t be a total waste,” Redfearn says.

He says producers must ask themselves three questions while making any decision — what are they trying to accomplish, do they need extra grazing days, and is there a backup plan?

“If you’re trying to stockpile forage for late fall grazing, it’s going to be beneficial,” Redfearn says. “You can have some pretty high quality grass that is going to put weight on those cows.”

He says in most cases, the cost of the application will more than pay for itself.

“It will cost your about $30 per acre for nitrogen and the cost of the application, and you can expect to get an extra one to 1.5 tons of forage,” Redfearn says. “That looks like a pretty good margin to me.”

He says there will be some labor costs associated with grazing, such as fencing and water, but says pasture fertilization will still pay off in the long run.

Late August and into September is the best time to apply fertilizer, says Rebecca Vittetoe, Extension forage agronomist with Iowa State University.

She says applying ahead of a rain event is usually preferable. A soil sample is also recommended to make sure phosphorus and potassium levels are acceptable.

“You really need that sample to see if you need to put some P & K back on the field if you have taken hay off it,” Vittetoe says.

She cautions producers to avoid overgrazing the pastures, adding that will cause extra stress for fields already dealing with hot weather and a lack of moisture.

Dry weather usually brings out the potato leaf hoppers, and Vittetoe says there have been reports of infestation in pastures. The quality of grass and legume stands could impact any decision for fertilization.

“Sometimes that second cutting will help get rid of them, but I would be out looking at your pastures and see what damage they are doing to alfalfa stands,” she says.

“Look at the cost of spraying and see if the benefit is worth the expense.”

Jeff DeYoung is livestock editor for Iowa Farmer Today, Missouri Farmer Today and Illinois Farmer Today.