Fertilization in home lawns

Lawns need to be fertilized to maintain color, density, and vigor. The healthier and more vigorous a lawn is, the better it can withstand stress from heat, drought, traffic, and pets, as well as competition against weeds, diseases, and insects. Excessive fertilizing can produce a dark green lawn, but it is likely not the healthiest. Fertilizing in moderation to maintain moderate growth and good density is most effective for lawns.

Fertilization Adjustments 

The amount of fertilizer applied annually to a lawn depends on a number of factors. Fertilization programs may need to be adjusted to apply slightly more or less nutrients annually, depending on the following factors:

• Desires: A dark green and dense lawn will require more fertilizer than a lighter colored lawn. However, applying more fertilizer annually also requires more mowing, irrigation, pest control, and other inputs. 

• Location: Because the growing season is longer in southeast Nebraska than in northwest Nebraska, more fertilizer will be needed to maintain the same turfgrass quality in southeast Nebraska than in northwest Nebraska. 

• Species: Turf-type tall fescue or buffalograss perform better with less nitrogen than Kentucky bluegrass or perennial ryegrass. 

• Weather: A rainy summer will stimulate growth and will usually necessitate more annual fertilizer than a dry summer. The same holds for an irrigated versus an unirrigated lawn.

• Soil type: Turfgrass grown on a sandy or heavy clay soil will need more fertilizer than turfgrass grown on a silt loam soil. Soils with inherent high fertility will require less fertilizer than inherently infertile soils. Soil type and pH will have a large effect on phosphorus and potassium needs. Sandy soils will need more frequent applications at lower rates to minimize the potential for leaching.

• Age and quality of existing lawn: A new lawn will need more fertilizer for the first few years to enhance density. Improving a neglected or thin lawn may also require more annual fertilizer for the first few years. Annual nitrogen can likely be reduced with no consequences on a lawn fertilized for many years.

• Clippings: Clippings should always be returned to the lawn. Removing clippings for composting or mulch removes about 1.0 lb N/1000 sq ft/yr. 

• Indicators: Presence of white clover or the diseases rust or dollar spot indicates a shortage of nutrients, whereas the diseases brown patch or pythium indicate too much annual nitrogen.

Fertilizers Types

All fertilizers will have a series of three numbers displayed prominently on the label. These numbers represent the percentage by weight of nitrogen (N), phosphorus (as P₂O₅), and potassium (as K₂O). For instance, a 24-4-8 fertilizer will have 24% N, 4% P₂O_5, and 8% K₂O. A 46-0-0 fertilizer will have 46% N, 0%, and 0% K₂O. The rest of the bag will consist of carriers, inert products, other non-nutrients, or perhaps sulfur (S) or iron (Fe). Though all three elements are important in maintaining a healthy turfgrass stand, N will cause the greatest response. Because of this, most fertilizer recommendations for lawns are listed in lbs. N/1000 sq ft. 

Nitrogen fertilizers come in two basic forms: Fast-release (soluble) nitrogen and slow-release (insoluble) nitrogen.  Fast-release nitrogen normally causes a response in one week or less, whereas slow-release nitrogen will cause a response over three to ten weeks or more. Fast-release nitrogen is inexpensive and may burn leaf blades if applied improperly. Slow-release forms tend to be more expensive but will rarely burn leaf blades even when applied at temperatures above 85F. Both N forms can and should be used on lawns. Both forms of N are often blended in one fertilizer bag to provide a quick N response shortly after application, plus a more gradual and longer response. Examples of differences between fast and slow release nitrogen in Table 1. 

Combination Products

There are lawn-care products that combine fertilizer with a pesticide, such as an herbicide or insecticide. These products should be used only when both the fertilizer and pesticide are needed to address a specific lawn management issue. 

Natural Fertilizers

Naturally occurring resources can also be used as fertilizers that provide the extra benefit of adding organic matter to the soil. Natural organic fertilizers typically supply nutrients more slowly than synthetic chemical ones, meaning they can be applied less often. However, they also tend to be bulkier, so more pounds of product are required to deliver the same amount of any given nutrient. Examples of organic fertilizers with the highest percentage of actual N per pound include blood meal, feather meal, corn gluten meal, and soybean meal. Research has shown that the best time to apply such fertilizers is late summer to early fall when turfgrass plants are focused on root growth. 

More information on Natural (Organic) Lawn Fertilizers via Iowa State University Extension and Outreach Factsheet

Additionally, grass clippings and fallen tree leaves are natural sources of nutrients commonly available from the landscape itself. Grass clippings can be mulched onto the lawn instead of bagged to provide a steady source of nitrogen all season long. In the fall, dry leaves may be chopped finely by running them over with a mower and then spread evenly over the lawn in a light layer. Recycling leaf matter in this way does not contribute to thatch formation. Just make sure that any clumps are dispersed evenly via raking or remowing the area. 

Fertilization Programs

For cool-season grasses like tall fescue or Kentucky bluegrass, fertilize lightly in spring and early summer, apply little to none in summer, and apply most of the fertilizer after Labor Day. Applying high rates of N in spring and summer stimulates excess leaf growth at the expense of root growth. Not only does this increase mowing requirements, but it also reduces turfgrass quality during the summer and potentially increases susceptibility to heat, drought, and pests. Conversely, warm-season grasses like buffalograss should be fertilized primarily in summer after green-up with no fertilizer prior to green-up in spring or after the last mowing in the fall. 

The links below list the University of Nebraska recommendations for fertilization of different parts of Nebraska:

• Warm Season Grasses 

• Athletic Field Management 

• Lawns in Eastern Nebraska

• Lawns in Western Nebraska 

Fertilization Application 

Apply fertilizer uniformly over the lawn. Overlap wheel tracks for drop-type spreaders. For rotary spreaders, apply the fertilizer so the wheel is at the edge of the pattern from the previous pass. Improper spreading of fertilizer will result in “streaking”, the alternate dark- and light-green stripes in a lawn (Figures 1 and 2). Agricultural-type fertilizers (10-10-10, 12-12-12, etc.) that have large particle sizes should not be applied with a drop-type spreader; a rotary spreader should be used instead. Irrigation or rain following fertilization is important to move nitrogen off the leaf blades and into the soil. Be sure to read the label instructions on fertilizer/herbicide combination products because some need to be applied to dry turfgrass and watered, whereas others need to be applied to wet turfgrass so it sticks to the leaf blades of the weeds. Combination fertilizer/ insecticides for white grubs always have to be watered in. Avoid applying fertilizer to drought-stressed or dormant turfgrass, or when temperatures are over 80°F. 

How to apply the correct amount of fertilizer? 

It is critical to apply the correct amount of fertilizer to your lawn. Additionally, the fertilizer bag may list the proper spreader setting for your spreader. Refer to the "Calibration of Fertilizer for Home Lawns" on the turf.unl.edu website. Even if your settings are listed on the label, you should calibrate your spreader to make sure it is still accurate. As spreaders get older, settings gradually change because of wear and tear. Regular cleaning and lubrication of the spreader will help it last longer. One way to spread the correct amount of fertilizer is to calculate the amount of product needed for your lawn, set the spreader very light, spread one-half of the total in one direction, and spread the other half of the total in a perpendicular direction.

Fate of Nitrogen and Phosphorus

There is some concern about nitrogen leaching into groundwater or running off into surface water. Research shows that when applied correctly and accurately, nitrogen remains where it is applied. A dense turfgrass canopy prevents water run-off and thus prevents nitrogen from moving across a lawn. The thatch and dense rooting of grass plants absorb nitrogen and prevent it from moving through the root zone. However, fertilizing too late in the fall or over-fertilizing for many years increases the chances for N leaching. Also, avoid applying fertilizer to impervious surfaces like walks and drives, and sweep or blow fertilizer granules from these areas into turfgrass after fertilizing (Figure 3). 

Leave an untreated/unfertilized buffer strip around all water bodies to prevent spreading phosphorus-containing fertilizers into the water.  Do not apply near drain tile inlets or surface drains. Never dump clippings into water bodies or storm drains (clippings contain 1-2% P dry weight). Avoid dumping tree leaves into water bodies or storm drains for the same reason. Be sure to calibrate your spreader and follow all label instructions on the fertilizer bag to reduce the risk of nitrogen moving away from the target. 

More information on fertilization testing from the University of Wisconsin. 

Fertilizer Safety and Environmental Stewardship

Before use, carefully read and follow all label directions regarding application timing, irrigation requirements, personal protective equipment (PPE), environmental precautions, and any restrictions on when people and pets may re-enter treated areas. Using combination products only when necessary can help reduce unnecessary pesticide applications while maintaining a healthy lawn. 

Proper fertilizer/pesticide use not only helps keep your lawn safe but also your family, pets, wildlife, and nearby water sources. It is the law to always read and follow the fertilizer/pesticide label before use since application directions and precautions vary by product. The label provides important information on application rates, timing, proper use, storage, and disposal that will maximize fertilizer effectiveness while reducing risks associated with personal injury, turfgrass damage, or environmental contamination. The following information below covers information on how to safely use fertilizers. 

Safety of Using Fertilizers

Read and Follow the Label

The label is the primary source of information for using the product safely and effectively. If the fertilizer contains a pesticide, consider the following check list below. For additional information refer to the NebGuide Understanding the Pesticide Label G1955. 

Before Application

• Read the label before opening the product.

• Verify the product is intended for your lawn.

• Apply only at the recommended rate and frequency.

• Check weather recommendations and avoid applying before heavy rain or during windy conditions.

• Determine whether the product should be watered in after application.

Safety

• Review any recommended personal protective equipment (PPE), such as gloves or eye protection.

• Follow all precautions for protecting children, pets, wildlife, and the environment.

• For combination fertilizer/pesticide products, read and follow all additional safety directions and use restrictions.

After Application

• Follow any directions regarding when people and pets can safely re-enter treated areas.

• Sweep any fertilizer granules from sidewalks and driveways back onto the lawn.

• Clean application equipment according to the manufacturer's recommendations.

• Store unused fertilizer in its original container in a cool, dry, secure location.

• Dispose of empty containers and unused product according to label directions and local regulations.

Personal Protective Equipment (PPE)

Most lawn fertilizers present relatively low hazards when used according to the label, but this does not negate risk to exposure. Fertilizer dust can irritate the eyes, skin, and respiratory system. Wearing gloves, closed-toe shoes, and eye protection when handling fertilizer helps minimize exposure.

• Wear gloves when handling fertilizer products. 

• Wear closed-toe shoes and long pants to reduce skin contact. 

• Safety glasses are recommended when pouring or spreading fertilizer to protect against dust and granules. 

• Wash hands thoroughly after handling fertilizer and before eating, drinking, or smoking. 

• Wash contaminated clothing separately from other laundry if significant fertilizer dust or spills occur.

Safe Equipment Use

Properly maintained equipment helps ensure accurate fertilizer applications while reducing unnecessary exposure, over or under application, and preventing product waste. Calibrate your spreader regularly so the correct amount of fertilizer is applied and inspect it before each use for worn or damaged parts that could affect its performance. After each application, clean the equipment according to the manufacturer's recommendations and store it in a dry location to prevent corrosion and maintain accuracy. Avoid leaving fertilizer in the spreader for extended periods, as moisture can cause granules to clump, clog the equipment, and reduce application accuracy.

Protecting People and Pets

Keep children and pets away from fertilizer during application and follow the product label for any recommended re-entry intervals before allowing them back onto treated areas. After fertilizing, sweep or blow any granules that land on sidewalks, driveways, or patios back onto the lawn to reduce the risk of accidental contact from barefoot people or paws and prevent nutrients from entering storm drains. Always store fertilizer in its original container in a cool, dry, secure location that is inaccessible to children and animals. See the NebGuide Safe Transport, Storage and Disposal of Pesticides EC2507 for additional information. 

Nebraska Department of Agriculture Fertilizer Program

The Nebraska Department of Agriculture (NDA) administers the state's Fertilizer Program to help ensure that fertilizer products sold in Nebraska meet established quality and labeling standards. Through this program, the NDA licenses fertilizer manufacturers and distributors, reviews product labels for compliance with state requirements, collects and analyzes fertilizer samples to verify nutrient content and label guarantees, and investigates consumer complaints regarding fertilizer products. While the NDA helps ensure the quality of fertilizer products available in Nebraska, homeowners also play an important role in protecting people and the environment by following the steps above. If you suspect a fertilizer product is mislabeled, does not perform as represented, or appears to be contaminated, contact the Nebraska Department of Agriculture's Fertilizer Program for assistance and additional information. 

For more information about Nebraska's Fertilizer Program or to report a product concern, visit the Nebraska Department of Agriculture at https://nda.nebraska.gov/plant/fertilizer.

Fertilization in Home Lawns Math Help 

References

Beard, J. 1973. Turfgrass science and culture. Pg. 428. 

Originally known as Fertilizing Home Lawns (2012), University of Nebraska-Lincoln Turfgrass Science Program, Pub. Turf 2012f by Zac Reicher. 

Revised and Edited by: 

Amanda Folck, Assistant Extension Educator in Turfgrass Management, University of Nebraska-Lincoln

Rachel Anderson, Associate Horticulture Extension Educator, Nebraska Extension 

Joshua Villazana, Program Coordinator and Assistant Extension Educator in Pesticide Safety Education Program, University of Nebraska-Lincoln