Rotation crops also may affect pH. He said phosphorus, potassium and secondary nutrients also may be affected by rotation and a more intense management system.

But nitrogen management is the most difficult and the most intensively managed nutrient.

Phillips said nitrogen management includes four critical factors — source, rate, timing and placement. If either of those factors is off, the efficacy of application may be adversely affected. “Think about it holistically,” he said.

He said many farmers adhere to established routines in nutrient management. “It’s tradition, the way we’ve always done things,” he said. “But we can and should think about manipulating fertilization programs.”

Phillips said most of his recent work has been for Southeastern conditions. “But fertility rate decision principles are universal.” He said precise rates from a Southeastern state might not work for Oklahoma, but the principle by which that rate is established will be just as effective in one state as another.

He said nitrogen source is often a matter of what’s cheapest or what’s available. “But we need to think about supplying the plant a nitrogen source in available form and recognize any synergism among elements. The best value depends on being more selective,” Phillips said.

He said “enhanced efficiency products” may have a place in intensive wheat production but producers must know what each product is intended to do. “There are no silver bullets,” he said. “Each of these products does something different and often work in specific conditions. They work in the environment they were designed to work in.”

He said the best nitrogen source will be available to the plant. “Also, recognize the existing loss pathways (leaching, volatilization, etc.).”

Rate depends on yield goal. “For 40 bushel wheat, you need 74 pounds of nitrogen per acre,” Phillips said. “Soil test regularly — every two to three years and annually when justified by research. And apply recommended rates.”

He said farmers using grid sampling should sample “every three years or so after establishing management zones. Follow that with yield mapping and adjust or re-sample if conditions change.”