Established MN Lawn Fertilizing Tips - Fertilzing OldLawns in Minnesota

Fertilizing Lawns

By: C. J. Rosen, B. P. Horgan, and R. J. Mugaas

Fertilizer Application for Established Lawns

The amount of nutrients required by an established lawn or turfgrass area depends on the type of grass plants and the management practices (how much care you decide to give the lawn balanced with demands of the grass variety). A vigorously growing, watered lawn from which the clippings are removed requires more added nutrients than a lawn that is not watered during the summer and where clippings are left on the lawn. Consequently, in developing a lawn fertilizer program, it is appropriate to divide lawns into high- and low-maintenance groups based on management practices.

High-maintenance lawns are characterized by vigorously growing plants such as improved Kentucky bluegrass and improved turf-type perennial ryegrass varieties. For best results these lawns are watered during the summer to maintain green growth. Clippings may or may not be removed. Usually there is no need to remove the clippings, in fact, clippings left on the lawn gradually decompose and reduce the need for fertilizer by about 1 lb N/1000 ft2 per year. A vigorously growing lawn may develop a thatch layer and require occasional aerifying or vertical mowing to control thatch.

The fertilizer schedule for a high-maintenance lawn should consist of 3 to 4 pounds of nitrogen per 1,000 square feet of lawn area each year. If quick-release nitrogen sources are to be used, 3 to 5 applications should be made according to the schedule in Table 6. The amount of phosphorus and potassium required for the lawn is determined by a soil test. Tables 7 and 8 give recommended amounts based on a test at the University of Minnesota Soil Testing Laboratory.

Low-maintenance lawns typically contain plants such as creeping red fescue, chewings fescue, hard fescue, or some of the common types of Kentucky bluegrass which grow and spread more slowly than those found in high-maintenance lawns. These low-maintenance lawns do not commonly receive watering (other than rainfall) during the summer months and grass growth is minimal during hot, dry periods. Clippings are usually left on the lawns.

A low-maintenance lawn will typically require only 1 to 2 pounds of nitrogen per 1000 square feet of lawn area per year. Table 6 suggests how to schedule these applications. Similar to high maintenance lawns, phosphorus and potassium requirements of low-maintenance lawns should be determined from soil tests. Phosphorus recommendations in Table 7 are applicable to low as well as high maintenance lawns. Potassium recommendations in Table 8 are based on soil test level and maintenance practices.