Photo Caption:Since 1991, a nitrogen leaching study guided by Dr. Kevin Frank (shown above) at Michigan
State University determined that nitrogen leaching can occur on mature turfgrass sites if too much
fertilizer is applied.
One of the most important responsibilities of superintendents is to manage the golf course while still protecting the environment. An important aspect of this responsibility is to minimize the transport of nutrients, particularly nitrogen (N) and phosphorus (P), to ground and surface water. Both nitrogen and phosphorous are essential for healthy turfgrass growth, but superintendents need to be cautious when considering how much fertilizer to apply to minimize the risk of nutrient pollution.
Since 1998, the USGA has provided funding to Michigan State University scientists to analyze the amount of nitrogen that moves downward through the soil under Kentucky bluegrass turf. The grass was fertilized with nitrogen at a low and high rate (e.g., 2 and 5 lbs N per 1,000 sq. ft.). In 2003, the high fertilizer rate was reduced to 4 lbs N per 1,000 sq. ft. because nitrogen was detected in water that leached four feet below the surface at levels above what is considered safe for the environment. The good news is that this small adjustment returned nitrogen levels for the next seven years to an acceptable level.
The take home message from the research at Michigan State University is that higher rates of nitrogen fertilizer may be acceptable during turfgrass establishment; however, as the grass matures over several years, nitrogen fertilizer rates should be reduced. If the higher nitrogen rates used during the first few years following establishment are not significantly reduced, unacceptable levels of nitrate leaching can occur, especially during the winter months when turf is dormant.