Fertilizing Home Lawns
The first step in developing a fertilizer program
for your lawn is to identify the
objectives for the lawn area on your
property. Homeowners demand a wide range of functions
from their lawns. Many property owners desire a formal
appearance with the lawn providing a uniform and manicured
setting. Others may utilize their lawns as highly trafficked play
areas, while others are interested in as little maintenance as
possible to provide a reliable and stable surface. Carefully
consider the function for your lawn along with the growing
conditions on your property, and then set realistic objectives
for your lawn. The fertilizer programs described below are
structured into three levels of maintenance-low, medium and
high. Choose the level of maintenance that will best fit the
level of input you want to dedicate to your lawn area and also
achieve your objectives.
All property owners should understand the environmental
considerations of their lawn maintenance activities. Fertilizers
can be used in a manner that will minimize the potential for
off-site movement. Properly fertilized turfgrasses can provide
an excellent filter for environmental contaminants, but excessive,
poorly timed or misapplied fertilizers have the potential
for off-site movement resulting in degraded water resources.
Of particular concern are fertilizer particles that land on
impervious surfaces such as driveways and sidewalks. These
materials are likely to run off in rainwater and be carried
downstream. Be aggressive in sweeping these particles back
into the lawn area where they will be utilized. Homes located
in urban areas with curb and gutter systems that are connected
to storm water drainage systems should consider themselves
connected to surface water resources via the storm
water handling system. Sensitive sites such as waterfront
properties should refer to Turf Tips E11TURF, “Maintaining
Waterfront Turf” for special instructions.
The three main components of turf fertilizers are nitrogen (N),
phosphorus (P) and potassium (K) (potash). A fertilizer
labeled 20-5-15 contains 20 percent nitrogen, 5 percent phosphorus
and 15 percent potash by weight. The importance of
each of these components is discussed individually below.
Soil Testing
Knowing the conditions of your soil is one of the
most important factors in growing a healthy lawn. Your MSU
Extension office can instruct you on how to conduct a soil test
through the MSU Plant and Soil Nutrient Laboratory.
Components of a Fertility Program
Nitrogen
Nitrogen is an essential nutrient for all plant growth and is
available in many forms from garden centers or professional
lawn care services. To successfully meet the objectives of
most lawn areas, annual applications of nitrogen are required.
The total amount of nitrogen required each season will vary,
depending on the desired level of maintenance and the growing
conditions on your property. Recommendations for the
amount of nitrogen and time of application for each maintenance
level (low, medium, high) are listed below in the timing
chart.
High maintenance situations are those where a high quality,
uniform, dense lawn or athletic field is desired and an irrigation
system is available. The primary turf grass species used in
this situation is Kentucky bluegrass. The medium maintenance
situation is for most general lawn or athletic field areas
where no supplemental irrigation will be applied, but the intention
is to optimize turf growth for quality, density or playing
conditions. The low maintenance situation is intended for lawn
areas where the lowest level of input to maintain turfgrasses
for a stable surface is desired.
Please consider the environmental responsibility of applying
nitrogen to your lawn. Nitrogen is easily dissolved in water.
When too much nitrogen is available for turfgrass plants to
consume and excessive water is present, nitrogen can move
away from the lawn and into water resources. This situation
can be easily avoided by following these suggestions.
-Do not apply more than 1 pound of nitrogen to 1,000
square feet of lawn per application.
In general, the recommendations located on lawn fertilizer
bags are designed to apply the desired amount — 1 pound of
nitrogen per 1,000 square feet of lawn. For example, if a bag
of fertilizer lists that it will cover 5,000 square feet of lawn, it
will deliver approximately 5 pounds of nitrogen to that area.
Follow the bag directions and don’t overapply.
-Consider using slow-release forms of nitrogen.
Slow-release nitrogen fertilizers are designed to release nitrogen
to the plants over a long period of time. Slow-release fertilizers
include organic sources such as poultry manure or
sewage sludge. Others include common nitrogen sources
such as urea or ammonia nitrate that are coated with materials
that release the nitrogen slowly over time. The portion of
slow-release nitrogen available in the fertilizer product is listed
as “water insoluble” nitrogen on the label.
Choose products with slow-release nitrogen to reduce the
potential for off-site movement.
-Keep fertilizers off impervious surfaces. Sweep fertilizer
particles from driveways and sidewalks back onto the lawn
area. This will prevent them from moving downstream with
rain water.
Phorosphorus
Phosphorus is a common component in most turfgrass fertilizers.
It is an important element for turf growth and is critical
for establishment of new seedlings. Phosphorus levels in soil
are stable, and most Michigan soils have adequate phosphorus
levels and therefore may not need continual applications
of phosphorus. A soil test will reveal the amount needed
annually on your lawn. Phosphorus is a primary water quality
concern in Michigan. Phosphorus applied to lawns is quickly
bound to soil particles after the fertilizer has been adequately
watered into the lawn. It is important to sweep these fertilizer
particles from impervious surfaces to reduce the potential for
them to move away from lawn areas. Sensitive lawn sites
adjacent to lakes, streams and ponds should use no-phosphorus
fertilizers when soil levels for lawns are adequate.
Potassium
Potassium is also a primary turfgrass fertilizer element. It is
usually applied in quantities ranging from 50 to 100 percent
of the nitrogen rate at each application. Potassium levels in soil are relatively stable. A soil test will reveal the amount
needed annually on your lawn. Levels below 120 pounds of K
per acre are low for lawn turf; soils with levels above 250
pounds of K per acre need no additional potassium.
Potassium is not regarded as a major water quality concern.
Putting Your Program Together
Identify the objectives for your lawn and choose the nitrogen
fertility program from the chart below that will best fit your
objectives. Phosphorus and potassium should be added to
the program on the basis of soil test information.
Once you have picked the level of maintenance and quality
for your lawn, you can target the application time for the most
effective use of the nutrients. The application times listed in
the table take advantage of late fall fertility. Research at
Michigan State University has demonstrated several benefits
for late fall nitrogen applications. During this time of year, the
top growth of the plant slows down as the temperatures cool,
but root growth continues to be active. Fertilizing at this time
of year will enhance the root growth and enable the plant to
store additional carbohydrates. These reserves provide vigorous
spring green-up, allowing the traditional early spring fertilizer
applications to be delayed. This adjustment helps limit
the heavy top growth usually associated with early spring fertilizer
applications. Environmental studies at MSU reveal that
this late fall application does not pose an elevated risk to
water quality. The application times listed in the table are
general guidelines for the mid-Michigan area. Adjustments
can be made for growing conditions in northern or southern
areas.
Special Considerations
You will need to adjust fertility for grasses grown in shady
areas by reducing the overall nitrogen applied. The overall
nitrogen applied can also be reduced by approximately 1
pound of N per 1,000 square feet when you return clippings
to the turf.
Home Lawn Fertilization Timing Chart
Pounds of nitrogen per thousand square feet of lawn
| Fertility Level |
April |
May |
June |
July |
Aug |
Sept |
Nov |
| Low 1-2# per year |
|
|
|
|
|
1.0 and/or 1.0 |
| Medium 3# per year |
|
1.0 or 1.0 |
|
|
1.0 |
1.0 |
| Medium 4-6# per year |
|
1.0 and/or 1.0 |
0.5-1.0 |
0.5-1.0 |
1.0 |
1.0 |
