Fall News Article
GROW HEALTHY LAWNS WITH LESS NITROGEN
Sid Bosworth, Extension Agronomist, and
Leonard Perry, Extension Horticulturist
University of Vermont
Most know nitrogen is important for growth and good quality lawns. But some may think that if some is good, more is better. But this is not necessarily true.
Nitrogen is one of the main fertilizer elements, the percent in a fertilizer represented by the first number in the analysis. So a 5-3-4 fertilizer would have 5 percent nitrogen. This element maintains dark green color, enhances shoot density, and increases grass resistance to stress and pest injury.
Too much nitrogen, however, can be detrimental to the turf grass. The grass may grow too lush, and so have increased disease problems. Too much nitrogen can reduce the lawn grass tolerance to high and low temperature stress. And too much nitrogen increases growth excessively, resulting in moisture stress and the potential for thatch (the dense layer of intermingled roots and shoots, both living and dead, near the soil surface that tends to block water and air).
Too much nitrogen also can be detrimental to the environment. Excess nitrogen can increase the risk of ground water pollution. More growth means more mowing. This means more time on the mower, more fuel used, and more air pollution from the mower.
Since nitrogen moves readily into the soil with water ("leaches"), it usually needs applying yearly in some form. There are some ways you can reduce the amount applied, or applied as fertilizers, and so reduce the risk of pollution.
· Be willing to have good quality turfgrass that is green, but
perhaps not as dark green as the slick ads on television and in magazines.
This is possible by using less nitrogen fertilizer-- no more than one pound
of actual nitrogen per 1000 square feet per application, and no more than
two applications per year. So if using a fertilizer with 10 percent
nitrogen, you should use 10 pounds to get this amount of nitrogen.
· Raise the mowing height to reduce turf stress and weeds.
We find that many still mow too low. Low mowing often is only justified
on highly maintained golf courses and similar situations.
· Use specialty turf fertilizers that have a high proportion
of water insoluble nitrogen (WIN). When possible use fertilizers
with at least 50 percent WIN of total nitrogen. Natural organic sources
are 100 percent slow release, which is desirable.
· Apply fertilizer at appropriate times of year. Avoid
or reduce summer applications. The best once-a-year application is
in late summer or early fall.
· Recycle grass clippings back into the lawns, such as with
a mulching type mower. About 46 to 59 percent of the applied nitrogen
from fertilizer ends up in the clippings. One estimate shows that
returning grass clippings can contribute about two pounds of nitrogen per
1000 square feet a year. Returning grass clippings to the turf can
reduce fertilizer needs by 25 to 40 percent.
· For some lawns, you may add or rely on a legume (such as white
clover) among the grass to add nitrogen. Legumes have bacteria on
their roots that take nitrogen from the atmosphere and convert it to nitrate
forms that plants can use.