BMPs for Lawn Care in Idaho

Idaho's Water
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.

Pesticide Concerns:
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 grass growth.
• 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 future.

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:

1. Know what is in your lawn!
• 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, etc.)
2. When a problem is identified, use the most environmentally sound solution.
• Consider:
• hand-pull weeds,
• change water management as an alternative to a fungicide to control a lawn disease,
• live with a low level of plant damage,
• use nontoxic solutions to hinder pests.
3. Use pesticides correctly.
• Follow pesticide label directions.
• Match pesticide with pest.
• Use correct application rate.
• Buy only what you need.
4. Store and dispose of pesticides properly.
• Buy in small quantities.
• Store in secured area.
• Dispose of in accordance with federal, state, and local regulations.
5. Use water wisely on lawns.

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!

Fertilizer Concerns
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!

Fertilizer Management BMPs
Fertilizer management BMPs you should implement on your lawn include:

1. Base fertilizer appplication rates on a sound scientific strategy.
• Nutrient ratio strategy:
• base nitrogen (N) application on lawn growing season,
• phosphorus (P), potassium (K), and sulfur (S) applications are based on ratio to N,
• 1,000 square feet of lawn requires 0.5 pound of N per month of active growth,
• 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 N.

3	:	1	:	2	:	1
N		P		K		S

Example Problem:
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 = 3.0 pounds N/1,000 ft2

3	:	1	:	2	:	1
3 lb N		1 lb P		2 lb K		1 lb S

• 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.
2. Correctly time your fertilizer applications.
• 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)
  Example Problem:
  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
  
3. Use slow-release N fertilizers
• Slow-release fertilizers improve N use efficiency by plants and reduce leaching.
• Look for fertilizers with the word WIN on the bag. WIN stands for water insoluble nitrogen. This is one type of slow-release nitrogen.
4. Use water wisely on lawns!
• Nutrients in the soil move with water.
• Over-watering causes nutrient leaching and possible environmental damage.
• 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.

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.

3M 4-94

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Revised: January 3, 2003

URL: http://www.uidaho.edu/wq/wqbr/wqbr28.html