Employing the 4Rs of Fertilizer Management

Every field in Iowa has unique nutrients needs. Applying fertilizer to meet those specific needs helps ensure the highest profitability for the farm and protects the environment from unnecessary nutrient runoff. It’s known as nutrient stewardship.

There are four principles of nutrient stewardship, otherwise known as the 4Rs:

  1. Right source
  2. Right time
  3. Right rate
  4. Right place

Leveraged together, they play an important role in Iowa’s Nutrient Reduction Strategy.

“Obviously, if we are applying higher nutrient rates than are needed — especially with nitrogen and phosphorus — it’s a problem because we have nitrates going to ground water or to surface water and phosphorus loss with surface runoff,” said Antonio Mallarino, a professor of Agronomy at Iowa State University.

The Bissell family in Taylor County is in the second year of analyzing their nitrogen application through the Iowa Nitrogen Initiative.

“I love data just by nature, and I was really interested in doing the study on how much nitrogen do we actually need,” said Aimee Bissell. “How can we cut our costs but still grow a crop?”

While a field’s nitrogen needs may vary broadly year-to-year, the Bissells found in the first year of the test they did not need as much nitrogen as they had thought.

“We’ve lowered our nitrogen rates a little bit and it’s cost savings on top of using less product,” said Klint Bissell. “And we haven’t seen yield lag.”

In Iowa, decades of soil testing provide solid guidance on phosphorus application. For nitrogen, the right amount is more of a moving target. Mallarino recommends applying a conservative rate pre-planned and then using in-season diagnostic tools to adjust the rate.

“We need to raise a crop, and we need to feed the world,” said Aimee. “We need to do more with less. It’s like solving a puzzle.”

The 4Rs of nutrient management are key to a farm’s bottom line and the reduction of nutrient losses.

“Using less product without affecting yield is a win-win,” Klint said.