University of Connecticut Cooperative Extension System: Water Quality and the Home Landscape


Sustainable Landscaping: Turf

by Karl Guillard

karl.guillard@uconn.edu

Fertilization Frequency

In many turf situations, there may be sufficient nitrogen mineralization in the soil to provide adequate growth and quality of the turf. If color and density of the turf is acceptable, then little or no nitrogen may be needed at that time. This would be particularly true for the low-maintenance grasses. If turf color and density is below acceptable levels, then some nitrogen may be needed.

There is a tendency to over-fertilize grasses with nitrogen, especially if clippings are returned to the turf. For most established lawns with clippings returned, two pounds of nitrogen per 1,000 square feet per year may be sufficient. Under this approach, one pound of nitrogen per 1,000 square feet is applied in late spring and one pound of nitrogen per 1,000 square feet in fall before October 15. If turf quality and density is acceptable before fertilization, it may be possible to reduce the nitrogen rate or eliminate entirely. Evaluate the turf before you decide to fertilize. With low-maintenance grasses, one pound of nitrogen per 1,000 square feet per year may be sufficient if clippings are returned. Split the applications at one-half pound of nitrogen per 1,000 square feet in the spring and the remaining one pound of nitrogen per 1,000 square feet in the fall before October 15.

To determine how much fertilizer to apply, it is necessary to figure out the size of the lawn in square feet. Bags of commercially available lawn fertilizers will list on the front of the bag how much lawn area the fertilizer in the bag will cover. If the clippings are returned to the lawn with each mowing, the amount of coverage shown on the bag should be doubled since returning clippings meets 50% of the lawn's nitrogen needs.

Applying nitrogen later than October 15 in our climate does not improve turf quality, but increases the nitrate leaching losses in late fall and winter. For turf, greener is not necessarily better as really dark-green turf imparted by high nitrogen fertilization weakens the grass, decreases its health, wastes money, needs more frequent mowing, and increases nitrogen losses from the system due to leaching below the root zone or off site with water runoff.