Courses OK on phosphorus runoff, need to work on nitrogen

Fertility professionals give superintendents a thumbs up for the efforts they’ve made to reduce phosphorus runoff into the Great Lakes and the Gulf of Mexico. However, professionals caution there still is work to be done when it comes to managing nitrogen.

“We are not overly concerned with golf courses and phosphate runoff,” says Harold Watters, assistant professor and extension field agronomist at The Ohio State University in Bellefontaine, Ohio. While he still has concerns over specific locations overloading P, he is more concerned with N runoff.

Watters notes that some of the pressure put on golf course managers, sports turf professionals and residents with lawns comes from the agriculture community. “Farmers are looking to move the blame somewhere else,” Watters says. “They want to shift the focus.” However, on an acre-by-acre basis, farms are the major users of N-P-K.

That said, several organizations and most college extension workers still see the occasional over-use of P on golf courses. “Absolutely soil test to meet your nutrient needs for pH, P and K,” Watters advises.

“I think you will learn that we’ve put on a little too much phosphorus over the years,” he continues. He says superintendents probably can ease up and mine their reserves to reduce phosphorous use. In Ohio, for example, about 35 percent of soil tests show an opportunity to draw down P.

While some superintendents favor applying phosphorous in the spring and others in the fall, seasonal timing of phosphorous applications seems to make little difference to turf. Rather, the key is to apply P when the risk of runoff from rainfall is low.

“We still have concerns about N,” Watters says of locations close to major bodies of water or where local creeks run off into streams or lakes. While acknowledging the need for N to keep turf green, he pleads with superintendents to pay attention to what they are doing. Testing for N is more difficult than testing for P and K.

Watters’ best recommendation: “Spoon feed rather than truck on the N.”