Farm Progress

Growing wheat? Consider manure as a phosphorus source

In areas where manure and litter are readily available, they can provide a way to meet higher phosphorus demands for wheat.

Tyler Harris

June 15, 2017

4 Min Read
A WIN-WIN SITUATION: At a recent Winter Wheat Field Day near Hooper, Rick Koelsch (left), UNL biological systems engineering professor, discussed how manure can be a win-win for growers. As a strong source of phosphorus, he notes, it can be a good fit for winter wheat.

Historically, producers have looked at manure as waste to get rid of, but Rick Koelsch is encouraging growers to think about manure as a potential win-win situation. "We've talked too much about the negatives associated with manure," Koelsch, a University of Nebraska-Lincoln biological systems engineering professor, told growers at a recent Winter Wheat Field Day near Hooper. "There's an opportunity to win economically, and there's also an opportunity to win from an environmental standpoint."

That's true for winter wheat growers with an available source of manure or litter, who have an additional window to apply in late summer or early fall when there's a lower risk of compaction.

Manage phosphorus, nitrogen
There are three benefits manure brings to a cropping system, Koelsch says. From a fertility standpoint, the first is phosphorus. Generally speaking, that's the most valuable component in manure.

For wheat growers, the benefit is more apparent, since wheat has a higher phosphorus soil level requirement than corn. For wheat, it's recommended to apply manure when soil phosphorus levels are 25 parts per million or lower. For corn, it's 15 ppm.

"Manure is a great way to bring the soil's phosphorus level up to raise a good wheat crop. Maintaining soil phosphorus at levels needed by crops, but minimizing excess phosphorus in our soils, is important for achieving both an economic 'win' and an environmental 'win' from manure," Koelsch says, adding that historically, growers with livestock have applied manure on the same crop field year after year, resulting in building phosphorus levels up too high. "I think that was part of the reason we thought of manure as a waste product. There was no value from that phosphorus."

With that in mind, there will likely be enough phosphorus left over for the following crop after wheat, Koelsch adds. For that reason, it's probably best to avoid applying manure on the same field two years in a row, and target fields that are low in soil phosphorus to get the most value.

There's also a nitrogen component, but depending on the manure source, the amount of organic nitrogen and ammonium nitrogen can vary. With beef feedlot manure or broiler litter, roughly 75% will be organic nitrogen, while 25% will be ammonium nitrogen. Koelsch notes the organic nitrogen may be difficult to credit for a crop with a spring need for nitrogen, such as wheat. However, if applying from a swine or dairy facility, roughly 75% of the nitrogen will be ammonium nitrogen and will be available almost immediately if injected or incorporated.

"Organic nitrogen is made available to the crop by soil microbes. That happens as soil warms up through the summer. For feedlot manure for example, about 25% of the organic nitrogen will be available in the first year. After that, it drops down about half each year," he says. "The problem with wheat is nitrogen is required around March and April, and the organic nitrogen may not be available in time for wheat."

That's why when applying feedlot manure or poultry litter high in organic nitrogen, it's best to apply it for the following corn crop. Swine or dairy slurry manure's higher ammonium N content will better meet a wheat crop's nitrogen requirement.

Nitrogen and phosphorus values and requirements will vary greatly between manure types, cropping systems and the individual field. So, it's a good idea to conduct a manure analysis and test for soil phosphorus levels before making a decision.

Biggest value is organic matter
The biggest value of manure and litter is an improvement to soil organic matter, Koelsch says. "That's the real advantage manure has over any commercial fertilizer," he says. "It's not a value you can put in the pocket book, but a value for resiliency of the soil."

Higher soil organic matter means more food for the microbial population in the soil to make polysaccharides, which Koelsch describes as "the glue that forms aggregates in our soil." Higher aggregate stability means improved infiltration, water-holding capacity and reduced erosion.

This change improves a soil's resilience to drought and reduces the movement of pollutants to nearby surface waters. "Animal manures can contribute to water and soil quality improvements, if we keep soil phosphorus levels near an agronomic level of value to crops," Koelsch adds.

In east-central Nebraska, Costco recently announced it selected Fremont as the site to build a state-of-the-art poultry processing facility. Because it will need over 300 broiler houses in the surrounding area to supply it, crop growers will soon have another source of litter in addition to those from swine and dairy facilities and feedlots in the region. "You're going to have an opportunity in this region with poultry," Koelsch says. "I encourage you to ask, 'Which of my fields can achieve an economic and an environmental win from animal manures?'"

To learn more, contact Koelsch at [email protected], and check out Extension publication EC143, Fertilizing Winter Wheat.


About the Author(s)

Tyler Harris

Editor, Wallaces Farmer

Tyler Harris is the editor for Wallaces Farmer. He started at Farm Progress as a field editor, covering Missouri, Kansas and Iowa. Before joining Farm Progress, Tyler got his feet wet covering agriculture and rural issues while attending the University of Iowa, taking any chance he could to get outside the city limits and get on to the farm. This included working for Kalona News, south of Iowa City in the town of Kalona, followed by an internship at Wallaces Farmer in Des Moines after graduation.

Coming from a farm family in southwest Iowa, Tyler is largely interested in how issues impact people at the producer level. True to the reason he started reporting, he loves getting out of town and meeting with producers on the farm, which also gives him a firsthand look at how agriculture and urban interact.

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