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Ohio State University Extension


Efficient Lawn Care Practices to Help Protect Ohio’s Waterways

Agriculture and Natural Resources
Ashley Kulhanek, Educator, Ohio State University Extension
Eugene Braig, Program Director, Aquatic Ecosystems, School of Environment and Natural Resources, The Ohio State University
Zane Raudenbush, Turfgrass and Herbicide Specialist, Davey Tree

Ohio has many water resources from small streams and ponds to regional lakes, rivers, and Lake Erie. Harmful algal blooms (HABs) can have a significant impact on water quality, which effects human health, the economy, and recreation. For example, the HAB of 2014 in the Western Basin of Lake Erie resulted in a two-day water ban for 400,000 Toledo residents. The estimated economic impact of this event was $65 million (NOAA n.d.). HABs are now common enough to warrant annual forecasting. Several factors impact algae and water quality. Fertilizer nutrients are especially harmful. Ohio needs everyone’s help to improve Ohio waters and minimize nutrient contamination. Read on for tips on how to maximize lawncare effectiveness and reduce nutrient runoff into Ohio waters.

Wave colored an unnatural bright green moves toward Lake Erie shoreline.

Algae and Ohio Waters

Algae are a normal component of ponds, lakes, and other waters. However, excessive growth of certain organisms can result in HABs. They produce toxins and cause illness, irritation, or death in animals and humans. HABs also alter the taste and odor of drinking water, pollute beaches with scums, and cause fish kills due to reduced oxygen levels.Aerial view of Lake Erie, showing the water colored an unnatural bright green just beyond the shoreline.

Most HABs are caused by cyanobacteria, also known as blue-green algae. Like plants and true algae, these microorganisms use photosynthesis to convert sunlight into food. They can exist without causing a significant health threat, but under the right conditions their populations can explode causing a bloom or overgrowth. Knowing the conditions that lead to blooms can help everyone improve our waterways.

HABs are minimized by reducing excessive nutrients in the water. Just as fertilizers aid the growth of grass and plants, they also help algae and other photosynthetic water organisms grow. Research has found that the nutrients phosphorus (P) and nitrogen (N) contribute to algae growth. Nutrients come from many sources, including agriculture fertilizer, lawn fertilizer, wastewater plants, sewage overflows, and faulty septic systems. Nutrient movement can be driven by rain events. Unfortunately, nutrients in water are hard to remove. Therefore, one way we can contribute to improving water quality is by preventing nutrients from entering Ohio’s waterways.

To reduce excess nutrients in our waterways, landowners can take steps to keep nutrients in place and prevent the overuse of certain nutrients in lawns and landscapes.Metal soil probe tool on its side in the grass, displaying a cylindrical core of soil that has been removed from the lawn.

Soil Testing for Lawns

Test the soil in your lawn and garden before making fertilization decisions. A soil test measures the ability of your soil to provide nutrients to your grass and landscape plants. Homeowners may be surprised by the high levels of nutrients in their yards. If nutrients are needed, soil test results provide recommendations for fertilization and application rates. Minimal applications of nutrients over the length of the season are suggested rather than one large nutrient application. Large applications can result in nutrients being washed away before the plants can use it. A soil test also reveals a pH imbalance, which could be inhibiting existing nutrients from moving readily into plants. For more information on conducting and interpreting soil tests, review The Ohio State University fact sheet, “Soil Testing for Ohio Lawns, Landscapes, Fruit Crops, and Vegetable Gardens,” at

Know Your N-P-K

Granular fertilizers display three numbers (e.g., 14-2-14) on the packaging. These numbers correspond to the percent of the nutrients: nitrogen (N), phosphorus (P), and potassium (K) by weight. Nitrogen is the most important nutrient for maintaining quality turfgrass. It improves the lawn’s density and color. Phosphorus is important when establishing a new lawn from seed. Phosphorus applications also treat nutrient deficiencies in home lawns, but this is rare in Ohio, especially if clippings are left on the lawn after mowing. Potassium is an important nutrient to help plants mitigate the effects of drought stress. Many soils already contain adequate levels of potassium, but it is best to do a soil test.

Timing is Everything!

In Ohio, lawns can generally be fertilized in the months of April and May, and again in September and October when needed. Fertilizing during the heat of the summer increases the severity of several turfgrass diseases and is not recommended for the homeowner. Ideally, when fertilizing an established lawn, select a fertilizer with a minimal amount of phosphorus (e.g., 18-0-10 or 22-2-14) unless soil tests indicate a deficiency. Many lawn companies have reduced or eliminated phosphorus from their residential products. Read the label before purchasing lawn fertilizers to ensure they contain the nutrients the soil test recommends. Keep in mind that nitrogen (N) is not tested in soil. It is very mobile and changes every day. Nitrogen is best applied on a schedule, using less on established lawns than new plantings. This nitrogen application strategy avoids causing health issues in the lawn, and contamination of the waterways.Man pushing fertilizer spreader over the lawn of an athletic field.

Establishing a lawn from seed is one of the few occasions when supplemental phosphorus applications are warranted. Starter fertilizers (e.g., 18-25-12) contain substantially more phosphorus to encourage the rapid establishment of young seedlings. Ideally, seeding or overseeding of home lawns should be completed in late August or September. Turf-type tall fescue seed is a good choice for Ohio because it performs well in full sun and moderately shaded environments. Spring seeding competes with too many weeds to be successful without pesticide intervention. For best spring success, using fast-germinating seeds such as ryegrass is recommended. Bluegrass cannot compete with summer annuals in the spring, but incorporating a mesotrione-containing, pre-emergent herbicide treatment at seeding reduces competition from crabgrass and other annual weeds. Do not use other pre-emergent herbicides when establishing a new lawn because these will impede the germination of your turf seeds. Mesotrione is the exception (Adams 2014). Beware of freezing temperatures in spring which can injure young seedlings.

Be Neat! Don’t Fertilize the Street!Granular fertilizer laying on concrete surface next to blades of grass.

Most of the fertilizers applied to home lawns are formulated as granular products because they are easy to apply. These granular products can also be impregnated with material to control weeds and insects. Unfortunately, it can be difficult during a fertilizer application to prevent granules from spreading onto driveways, roadways, and sidewalks. If not removed, rainfall can wash these granules into storm drains and degrade our waterways. This scenario is easily avoided by sweeping or blowing fertilizer granules back into lawns after an application.


Adams, Ryan. 2014. “Establishing a Lawn from Seed.” Iowa State University, Extension and Outreach.

Boggs, Joe, Cindy Meyer, Gary Gao, and Jim Chatfield. 2017. “Soil Testing for Ohio Lawns, Landscapes, Fruit Crops, and Vegetable Gardens” (HYG-1132). Ohioline, The Ohio State University.

Braig IV, Eugene C., Joseph Conroy, Frank Lichtkoppler, William E. Lynch Jr., and Linda Merchant-Masonbrink. 2011. Harmful Algal Blooms in Ohio Waters. Ohio Sea Grant, The Ohio State University. PDF.

NOAA (National Oceanic and Atmospheric Administration). n.d. Harmful Algal Blooms (HABs) in the Great Lakes. NOAA, Great Lakes Environmental Research Laboratory. Accessed August 1, 2023. PDF.

Originally posted Feb 1, 2022.