| ||BMPs for|
Lawn Care in
Over 90 percent of the drinking water consumed in Idaho is supplied by
groundwater. This resource is vital to homeowners and industry as well as Idaho's
agricultural community. Best management practices (BMPs) for lawn management have
been and are becoming more important.
Groundwater is found in the pores and cracks of underground sand, gravel, and
rock deposits. The formation through which it slowly flows is called an aquifer.
The top of the water-saturated zone is the water table, and water percolating
down to it is called recharge.
Recent surveys by Idaho water quality specialists have found trace amounts of
chemicals -- nitrates -- and, in some cases, pesticides in some of Idaho's
drinking water. Nitrates can get into drinking water from many sources, but poor
management practices can cause pesticide contamination. Pesticides can get into
groundwater through agricultural, industrial, and homeowner uses as well as
spills and improper disposal. Contaminated water is difficult and expensive to
manage once it becomes dispersed underground.
Your Lawn and the Environment
Your lawn is something you should be proud of! It is an attractive part of your
landscape. In fact, a well-maintained lawn adds value to your property. Your lawn
helps to tie together your home and other landscape plants.
A healthy, good looking lawn actually helps improve your living environment. On a
hot day your lawn reduces the glare of the sun. Your lawn can also help keep
surrounding areas cooler. A well-maintained lawn is much more attractive than
pavement! Your lawn will attract birds and other wildlife. On windy days your
lawn will trap dust particles from the air. And most importantly your lawn
protects the soil on your property from erosion.
Inputs such as pesticides, fertilizers, and water when used incorrectly may
adversely impact surface and/or groundwater quality. To protect the environment
and water quality you should use BMPs, which are defined as implemented
strategies that eliminate or minimize environmental pollution. BMPs are designed
to be compatible with good, sound lawn management. BMPs can protect the
environment without compromising the beauty of your lawn.
Why should homeowners be concerned about pesticide use on lawns?
- On a square foot basis many homeowners use a large quantity of pesticides
on their lawns.
- Pesticide over-use will often harm or kill beneficial insects associated with
your lawn. In addition, earthworms in your soil, birds, and pets can also be
harmed or killed. Certain pesticides can also harm the applicator -- you -- if
over-used or misapplied.
- Pesticide over-use can harm your lawn and the surrounding environment.
Over-application of pesticides may result in chemicals running off the surface of
your lawn during rainfall or irrigation. The pesticides in the runoff water could
reach local streams, rivers, and/or lakes. On the other hand, some pesticides
could leach through your soil and comtaminate groundwater. This is likely your
source of drinking water. Over-application of pesticides may result in the
accumulation of residues in the soil. These residues may be directly toxic to
- Over-application of pesticides will often result in pest resistance to the
applied chemical. Naturally occurring mutations may create super insects or weeds
that will be almost impossible for you to control with pesticides in the
Many pests attack lawns. These pests fall under four broad categories: weeds,
insects, diseases, and other pests.
WEEDS: Weeds are simply plants growing in the wrong place. In the case of
your lawn a weed is any plant that is not the variety of grass that was
originally seeded to produce your lawn. There are over 30 weeds common to lawns
in the Pacific Northwest. Most of these weeds can be easily eliminated from your
lawn. Besides using pesticides, there are management options that discourage
competition from weeds. Some options include mowing to the proper height, not
over-fertilizing, and not over-watering. Chemicals applied to lawns that kill
weeds are called herbicides.
INSECTS: Several dozen different insects live in your lawn at any one
time. Most of these insects are harmless. In fact many insects are actually
beneficial. These beneficial insects prey on insect pests that harm your lawn.
Only a very few kinds of insects actually can damage your lawn. Chemicals applied
to lawns to kill insects are called insecticides.
DISEASES: Lawns are susceptible to several different diseases. Many of the
diseases that attack lawns are caused by improper management by the landowner.
Some potential management problems include improper watering, improper
fertilization, lack of thatch removal, and choosing the wrong grass cultivar for
the climate. Chemicals that are applied to lawns to control disease problems are
usually called fungicides.
OTHER PESTS: Several categories of non-insect pests attack lawns. These
include rodents such as moles and gophers, nematodes, snails and slugs, and ants.
Chemicals used to kill rodents are called rodenticides. Chemicals used to
kill nematodes are called nematicides.
Pesticide Management BMPs
Pest management BMPs you should implement on your lawn include:
- Know what is in your lawn!
When a problem is identified, use the most environmentally sound
- Identify your weeds.
- Identify your insect and other pests.
- Identify your disease problems.
- Learn about the type of grass in your yard (e.g., bluegrass, fescue,
Use pesticides correctly.
- hand-pull weeds,
- change water management as an alternative to a fungicide to control a lawn
- live with a low level of plant damage,
- use nontoxic solutions to hinder pests.
Store and dispose of pesticides properly.
- Follow pesticide label directions.
- Match pesticide with pest.
- Use correct application rate.
- Buy only what you need.
Use water wisely on lawns.
- Buy in small quantities.
- Store in secured area.
- Dispose of in accordance with federal, state, and local
Many pesticides applied to lawns move in the soil with water. Overwatering may
cause the pesticide to leach and eventually contaminate the groundwater.
- Never overwater your lawn!
Why should homeowners be concerned about fertilizer use on lawns?
- On a square foot basis many homeowners use large quantities of
fertilizers on their lawns.
- Fertilizer over-use can negatively impact the environment. Fertilizers can
run off the soil surface and contaminate nearby streams and lakes. Fertilizers
also have the potential to contaminate groundwater when over-applied. The
nitrogen applied to lawns is converted to nitrate by biological processes in the
soil. Nitrate is mobile in soils and can leach into the groundwater. High levels
of nitrates in water collected from wells can be hazardous to your health.
- Fertilizer over-use can negatively impact the health of your lawn. The
combination of large amounts of fertilizer, too much water, and water at the
wrong time of day sets up the perfect environment for many turfgrass diseases.
Diseases such as necrotic ring spot show up much more frequently in intensively
managed, highly fertilized lawns.
- Fertilizer over-use can result in excessive invasion by weeds. When given a
nutrient-rich environment there are several weeds that become very competitive
with the grasses you are trying to grow!
Lawns in Idaho generally need additions of only four nutrients. These nutrients
include nitrogen (N), phosphorus (P), potassium (K), and sulfur (S). If your soil
pH exceeds 6.8 your lawn may also require additions of iron (Fe). Soils in Idaho
contain adequate levels of boron (B), chlorine (Cl), copper (Cu), manganese (Mn),
molybdenum (Mo), nickel (Ni), and zinc (Zn) to meet your lawn's nutrient needs.
Improper use of either nitrogen and phosphorus fertilizers on lawns can have a
negative impact on water quality in your community.
Fertilizer Management BMPs
Fertilizer management BMPs you should implement on your lawn include:
- Base fertilizer appplication rates on a sound scientific
- Nutrient ratio strategy:
- base nitrogen (N) application on lawn growing season,
- phosphorus (P), potassium (K), and sulfur (S) applications are based on ratio
- 1,000 square feet of lawn requires 0.5 pound of N per month of active
- determine length of lawn growing season in months, and
- once N need is determined, P, K, and S applications are based on a ratio to
|Q.||How much N, P, K, and S do I need if my lawn is actively
growing for 6 months per year?|
|A.||0.5 pound N/1,000 ft2/month X 6 months =
|3 lb N||1 lb P||2 lb K||1 lb
Correctly time your fertilizer applications.
- Buy a fertilizer with as close to a 3:1:2:1 ratio as possible, or mix
different fertilizers together to make the desired analysis.
Use slow-release N fertilizers
- Apply fertilizer when the lawn needs it.
- Use split applications on your lawn -- divide the total nutrient application
by 4 and apply:
1/4 in early spring (Easter)
1/4 in late spring (Memorial Day)
1/4 in late summer (Labor Day)
1/4 in fall (Halloween)
If your year requirement for N is 3.0 pounds/1,000 ft2 (as
in the last example problem), apply as follows:
0.75 pound N around Easter
0.75 pound N around Memorial Day
0.75 pound N around Labor Day
0.75 pound N around Halloween
Use water wisely on lawns!
- Slow-release fertilizers improve N use efficiency by plants and reduce
- Look for fertilizers with the word WIN on the bag. WIN stands for water
insoluble nitrogen. This is one type of slow-release nitrogen.
- Nutrients in the soil move with water.
- Over-watering causes nutrient leaching and possible environmental
- Water lawns at optimal times -- in the morning between 6 a.m. and noon.
- Water deeply (6 inches) a couple times a week -- instead of shallowly every
day or every other day.
Remember, to protect the environment, your lawn management program must consider
BMPs for pest management and fertilizer management. Water management is a
component of each. Utilization of the BMPs presented in this brochure will make
you a steward of the environment. In most cases these BMPs will not increase
your costs. In fact you will probably have a better looking, healthier lawn!
Remember that your lawn management system can be environmentally friendly!
This brochure, WQ-28, was prepared by R. L. Mahler, J. Robbins,
and K. A. Loeffelman, Soil Science Division, University of Idaho, Moscow, Idaho
83844. Robbins is the Extension Agricultural Agent, Blaine County, Hailey, ID.
Comments to webmistress:
All contents copyright © 1997-2003.
College of Agricultural and Life Sciences, University of Idaho.
All rights reserved.
Revised: January 3, 2003