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Fertilizer management looks different in times of drought

Fertilizer management looks different in times of drought

Michael Castellano

Michael Castellano

In years of drought, farmers need to give extra consideration to fall nitrogen applications.

Based on prior years’ soil nitrate levels and precipitation, research shows there is currently higher-than-normal nitrogen levels in Iowa soils due to the ongoing drought. That’s according to agronomy professor Dr. Michael Castellano and soil science professor William T. Frankenberger of Iowa State University. Research at their lab over the last 30 years has examined nitrogen following a drought.

“Based on Iowa State University research, we know that during a drought year, the soil retains more nitrogen for a number of reasons,” Castellano said. “Not only does the crop utilize less nitrogen, but there is also a major reduction in the amount of nitrogen lost to leaching and denitrification.”

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This soil map of Iowa shows the amount of nitrogen in the soil as of September. Crops use less nitrogen in dry years.

As a result, he encourages farmers to have their soil tested before making fall application decisions that not only impact the environment, but also their profitability.

Shawn Richmond, environmental services director at the Agribusiness Association of Iowa, encouraged farmers to work with their ag retail partners to consider soil testing for nitrogen, reduce rates of fall fertilizer application and consider split rate of spring applications instead.

“Fertility decisions are always important, but especially so following drought conditions. Taking steps this fall like soil tests for nitrates to inform fertility decisions can help with meeting goals for next year’s crop needs,” Richmond said.

Iowa Secretary of Agriculture Mike Naig also stressed the importance of fertilizer management in a drought year. In addition to making smart nutrient management decisions, he encouraged Iowa farmers to utilize cover crop cost share programs.

“Cover crops can help scavenge and hold onto excess nitrogen in the soil so it’s available for the following crop instead of being lost through runoff or leaching,” said Paige Frautschy, Iowa agriculture program director at The Nature Conservancy.

Farmers and their advisors can learn more about conservation practices, like cover crops, that can make their operations more efficient and resilient by visiting

In addition to the important water quality and conservation implications of fall nitrogen decisions this year, high fertilizer prices make a compelling economic case as well.

“Increasing nutrient use efficiency through improved fertilizer management is a smart thing for farmers to do every year, but in drought years like 2021, it’s imperative,” said Sean McMahon, executive director of the Iowa Agriculture Water Alliance. “Farmers have a great opportunity this year to save money by reducing fall fertilizer applications considering the already higher than normal nitrogen levels in our soils due to the ongoing drought. That’s a win-win for farmers’ profitability and improving our water quality.”

The Clean Water in Iowa Starts Here campaign was created by the Iowa Department of Agriculture and Land Stewardship, Iowa Soybean Association and Newsradio 1040 WHO in 2020. It aims to raise awareness about the conservation work underway across Iowa. It also highlights opportunities for both rural and urban residents to use soil health and water quality best practices and play an active role in conservation projects happening in their communities.

During the Clean Water in Iowa Starts Here campaign, The Big Show will visit locations throughout the state, showcasing the people and practices that are having a positive and measurable impact on water quality. The conversations with farmers, landowners, agribusinesses and community leaders will be broadcast on Wednesdays during The Big Show airing from 11 a.m. to 1 p.m. on WHO and 11:30 1 p.m. on WMT.

For more information about the campaign, upcoming stops, and rural and urban soil health and water quality practices, visit

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