Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, October 5, 1995 TAG: 9510050015
SECTION: CURRENT PAGE: NRV-10 EDITION: NEW RIVER VALLEY
SOURCE: JOE HUNNINGS
DATELINE: LENGTH: Medium
These facts are supported by research conducted by agronomists such as Virginia Tech's Roy Blaser, R.E. Schmidt and John F. Shoulders. Their observations indicate that excessive spring fertilization often leads to summer death of cool-season grasses. Agronomists have shown us the importance of fall fertilization to enhance the quality of bluegrass, fescue and ryegrass lawns.
What is important about the fall? As temperatures cool in autumn, grass top growth slows down. However, photosynthesis (the process of plant food production) is temperature insensitive, so plant food (carbohydrates) continues to be produced into December. This enables carbohydrates produced in the fall to be used for root growth and for storage. Root growth is important in replacing roots that may have suffered during the summer. The food reserves will be utilized to produce sustained, even growth in the spring and to allow recuperation from summer heat stress.
Spring nitrogen fertilization creates the opposite reaction in turf. Top growth is encouraged at the expense of the root system, causing the plant to significantly lose roots, a difficult condition for moving into the heat and drought stress of summer. This "deficit spending" can lead to eventual weakening or death of the plant. A weakened turf is more susceptible to diseases, insect attacks and weed encroachment.
The first step in lawn fertilization is to have the soil tested. Test results determine which nutrients are available in the soil, and indicate recommendations for liming and fertilization. Forms and sample boxes, along with instructions for obtaining good samples, are available from your Cooperative Extension Service office. Samples should be taken from several areas in the lawn. Samples from areas that have similar soil types should be combined. For most yards, one combined sample is adequate. Large yards with widely varied conditions may require more samples. There is no need to submit more samples than you are willing to individually treat.
After receiving your soil-test report, you will be ready to purchase your fertilizer. The numbers on the fertilizer bag (such as 10-10-10 or 46-0-0) indicate the percent of nitrogen, phosphate, and potash in the fertilizer. If your soil test indicates low or medium levels of phosphorus or potassium, complete fertilizers should be used. If high levels of phosphorous and potassium are present in the soil, then fertilizers supplying only nitrogen will be adequate.
There are two types of nitrogen sources: quickly available, and slowly available. Quickly available materials are water-soluble and can be immediately utilized by the plant. Slowly available nitrogen sources release their nitrogen over extended periods of time and, therefore, can be applied less frequently and at higher rates than the quickly available nitrogen sources.
If more detailed information is needed on fertilization, ask your local Extension Agent for Virginia Extension publication 430-011, Lawn Fertilization in Virginia.
Joe Hunnings is the Virginia Cooperative Extension agent for agriculture in the Montgomery County Extension Office in Christiansburg. If you have questions, call him at 382-5790.
by CNB