An ISU research project aimed at finding ways to spread fertilizer uniformly over crop land will help protect Iowa’s waters from excess nitrogen flow, experts said.

Mark Hanna and James Baker, both from ISU agricultural and biosystems engineering, teamed to head the three-year project that is being funded by a Leopold Center of Sustainable Agriculture grant.

Anhydrous ammonia has been applied to fields for more than 50 years as an inexpensive source of nitrogen fertilizer, they said.

More than 50 billion pounds of anhydrous ammonia are applied to Iowa fields each year, costing farmers more than $150 million.

“Anhydrous ammonia is the most popular fertilizer because it’s the least expensive,” said Hanna, scientist in agricultural and biosystems engineering.

He said cutting back usage of the fertilizer by just 5 percent would save 50 million pounds of anhydrous ammonia every year.

However, Baker, university professor of agricultural and biosystems engineering, said one downfall to anhydrous ammonia is the difficulty in spreading it evenly over fields. This task is very difficult because anhydrous ammonia comes in both a liquid and gas form.

“Anhydrous ammonia is mostly liquid, with a vapor over top,” he said. “As soon as you release pressure [in the tanks], more gas forms.”

Baker said it is difficult to measure how much ammonia flows onto the field at any given time because the amount of gas and liquid in the tank can be highly variable, so it is released at different rates.

“Typically anhydrous ammonia is applied using subsurface injections on either side of the crop row,” Hanna said. “It is not uncommon for a knife to put on fertilizer at twice the rate the farmer has set.”

Baker said surface water washes away some of the nitrogen, but most of it is lost through the subsoil around the plants’ roots.

“When you go through wet and rainy periods, the nitrogen gets pushed below the root zone in the ground water,” Hanna said. “If it is pushed below the root zone, it is wasted because the roots can’t reach it. That is when it is washed into the groundwater.”

Baker and Hanna are currently searching for equipment that would help spread out the nitrogen more evenly on the fields.

They are testing machines that are currently commercially available and are also looking at new designs.

“We hope to be able to identify one or more manifolds that give a more unified application and give growers the confidence to cut back on the amount of nitrogen applied,” Hanna said.