Discovery Farms Nitrogen Survey brings experts together

Gloria Hafemeister
Cover crops, particularly when there is a mix of them, contribute to soil health and nutrients for future crops.

JEFFERSON -  Farmers in Jefferson and surrounding counties met last week in Jefferson with UW-Discovery Farms officials to learn about ways farmers can work with the Discovery Farms program to evaluate practices on their farm and help find ways to make more efficient use of nutrients in fields.

Abbey Augarten, of the Discovery Farms program shared results from the nitrogen management studies so far on 40 participating farms and said Discovery Farms plans to enroll even more farms in the study in the future.

“The goal is not to define a perfect data for everyone but to help farmers understand what, on their farm, is the best rate to maximize production without wasting nitrogen,” she explains.  “When excess nitrogen is lost it is gone and if not enough is used the crops will deplete the soil of organic matter.”

As a part of the Nitrogen Use Efficiency study, the researchers tracked nitrogen from all sources as it cycles through the growing season from the soil into corn plants.

More not always better

Applying more nitrogen to a growing crop does not always equal more yield, she points out.

In fact, the percentage of supplied nitrogen that is taken up in the grain decreased as the total amount of nitrogen supplied increased.

“Fields that supplied less than 160 pounds of nitrogen on average had a nitrogen recovery greater than 100 percent, suggesting that all the nitrogen supplied was taken up along with additional nitrogen supplied by the soil,” she points out.

By accounting for nitrogen from all sources including manure and legumes the input cost of commercial fertilizer can be reduced.

Consider rotational benefits

After alfalfa, all grain fields in the study had an average yield of 233 bushel per acre and yield did not depend on the nitrogen rate. Farmers who applied less than 90 pounds to their corn following alfalfa had much higher efficiency, compared to those who partially credited alfalfa or did not credit at all.

After soybeans, all grain fields had an average yield of 232 bushel per acre and yield did not depend on the nitrogen rate. Farmers who decreased their nitrogen rates following soybeans had higher efficiency compared to those who partially reduced their nitrogen rates or did not reduce rates at all.

In corn silage fields, just like in corn grain fields, decreasing nitrogen rates following alfalfa increases efficiency without hurting yield.

Tillage Differences

A final part of the study was looking at the comparison between tilled and no-till fields.

On average, the no-till corn silage fields had nitrogen rates that were 30 pounds less per acre than tillage fields. Although the rates were lower, no-till fields did not suffer a yield decrease.

“Because yield was similar and nitrogen rates were lower, the nitrogen use efficiency values from corn silage in no-till systems were on average greater than values in tillage systems,” she said.

Other studies

In future studies Discovery Farms plans to consider things like “Do no-till farmers use less nitrogen for conservation reasons? Does the practice of no-till allow for a reduced rate? Does soil health play a role in this?”

She encourages farmers to consider participating in studies or to monitor fields on their own, comparing various practices and fertilizer rates.

Matt Ruark shared results of a long-term study at the Arlington Research Farm measuring nitrogen and carbon in fields that have not received additional nitrogen for many years.

He points out that an extreme removal of the crop, like corn silage, mines the soil over time and removes carbon. Studies are currently looking at the role of cover crops in corn silage fields as a way to build or maintain the soil organic matter.

He too encouraged growers to monitor the benefits of their fertilizer program in order to fine-tune their applications.

“There is a real value in using zero nitrogen plots to learn about the true value of the fertilizer and to be used as an indicator of soil health,” Ruark said.

Waterway Network

One of the latest projects of the Discovery Farms program is the development of the Waterway Network.

Erica Olson was on hand to described the program and encourage participation in it. The Network is a password protected, on-line discussion forum focused on using science and local experience to answer conservation questions.

Currently registration is open to all Wisconsin and Minnesota farmers and crop consultants.

“We’re adding some hand-picked experts every month. We’re keeping it private, by using the password, to foster more open dialogue,” she explains.

There is no cost to participation and growers and consultants have unlimited access to the experts by bringing scientists and area farmers and crop consultants together to contribute decades of experience.

To join the program, visit  Click on “register here.”  Instructions will then be provided for establishing a password and getting started.