AMES, Iowa — Increasingly volatile weather conditions may be changing how U.S. farmers handle their crop nutrients – and the effectiveness of their fertilizers, according to Elwynn Taylor, Iowa State University (ISU) meteorologist and agronomist. 

“We’ve just come to more uncertain conditions, which is not an uncommon thing,” he said.

As weather patterns change, Taylor said, some farmers are finding they are losing more nitrogen from their fertilizers to the surrounding environment.

In many cases, he added, this is because of increased and unseasonal rainfall, followed by long dry spells and warmer winters.

“If we look at the history of corn yields since we started keeping records in the 1860s,” he said, “we have had four 25-year periods of highly variable corn yields because of variability in the weather. 

“Those four periods were separated by four 18-year-long periods of consistent crop yields,” he added. “I believe what we’re seeing is the beginning of a period of variable yields and weather.”

According to Taylor, increased weather volatility is causing bacteria and other microorganisms to become more active earlier than normal.

“We might get this really warm weather that we usually don’t have where the soil temperature goes up into the 50s in December,” he said. “Microorganisms in the soil can begin to convert nitrogen to a form that can be lost. 

“Usually, if you put on nitrogen in the fall, it will remain with the crop and not be lost to microorganisms in the winter months,” he added.

Kurt Seevers, technical services manager with Verdesian Life Sciences in Visalia, Calif., said increased temperatures also allow soil bacteria to be active for longer periods of time.

“Variability in rainfall may also play an increasing role in nitrogen loss, if we see heavy rains like we’ve had in some areas of the country the past couple of years,” he added. “A combination of these factors could increase the likelihood of nitrogen loss.”

According to Seevers, nitrogen loss can lead to reduced yields and increase the potential for disease pressure due to less vigorous plants, with lost nitrogen ending up in ground water if it leaches from the root zone as nitrate, or if it enters the air as ammonia.

In addition, Seevers said up to half of nitrogen applications can be lost through three main causes: leaching, volatilization and denitrification. 

Seevers added it’s important that farmers protect their profitability and crops from a more volatile environment.

“The use of nitrogen stabilizers is a common way to address potential nitrogen loss,” he said. “Most work by reducing or eliminating the activity of the bacteria or enzymes responsible for metabolizing nitrogen into forms that are lost to volatilization or leaching, or are more readily tied up in the soil.”

But Ryan Bond, Verdesian vice president of marketing and technical development, said farmers need to be aware that not all products guard against these three types of nitrogen loss. 

In Missouri, losses of nitrogen can be large in years with wet June weather, especially on poorly drained soils, according to University of Missouri (UM) Plant Sciences Extension. 

Because of the volatile weather conditions, nitrogen management products may be necessary, Taylor said. 

“With changing temperatures, microorganisms become more active in the soil,” he said. “Nitrogen stabilizers protect your investment by giving your crop more opportunity to use those nutrients before the microorganisms do.”