Gardening: Fall fertilizations can help ensure lush lawns come springtime
When September and fall weather arrive, many homeowners look forward to winding down their home lawn maintenance activities for the season. But fall can be the most important time to accomplish the one lawn maintenance task that can have the greatest impact on lawn quality — application of fertilizer. Although many homeowners confine their lawn fertilization applications to spring, fall applications of fertilizer can have a greater impact on turfgrass quality than spring applications.
For maximum turf quality and health, a typical recommendation would be to apply fertilizer four times each year with the first application in April along with an application of pre-emergent herbicide if crabgrass was present the previous season. The second fertilizer application should occur in late May and can be combined with an herbicide application to control broadleaf weeds if they are present in the lawn.
The other two fertilizer applications are critical, and should be completed in early September around Labor Day and in late November around Thanksgiving. These two applications help grass plants develop stronger and more resilient root systems and store nutrients needed for spring green-up and growth.
Fall lawn fertilizing provides needed nutrients
Like most green plants, turfgrasses require three macro-nutrients for proper growth and development: nitrogen, phosphorous and potassium. Nitrogen is needed for leaf-blade growth and deep-green color; phosphorous helps plants develop healthy and extensive root systems; and potassium helps with movement of water, nutrients and carbohydrates in plant tissue, and is needed for photosynthesis.
Additional nutrients called micro-nutrients are also needed for plant growth, but these nutrients are typically needed in smaller amounts than macro-nutrients and are usually available in adequate amounts in most soils.
While phosphorus and potassium accumulate in the soil until they are used by the roots, nitrogen quickly leaves the soil by leaching down through the soil profile and denitrification into the atmosphere. Because of this, nitrogen is typically the limiting factor when attempting to grow a lush green lawn.
More:Gardening: Planting veggies in August? Of course! Cool-season crops are often sweeter
Don't guess — a soil test will tell you if you need to adjust the soil pH
Most turfgrasses require a total of 3 to 5 pounds of actual nitrogen per 1,000 square feet per year. Because they accumulate in the soil, the amount of phosphorous and potassium needed to grow a lush green lawn can only be determined by an analytical nutrient test. Late summer and fall is an ideal time to have your soil tested and apply needed phosphorous and potassium.
A soil test will also measure the acidity or alkalinity (pH) of your soil to determine whether a corrective application of lime is needed to adjust the soil pH. Most native soils in Greater Columbus tend to be alkaline with a high pH level, and hardly ever require an application of lime. This is because the parent material of local soils are limestones which are located fairly close to the soil profile.
Soil testing is available through Ohio State University Extension Offices and test sample kits are available for purchase at https://franklin.osu.edu/program-areas/agriculture-and-natural-resources/soil-testing.
Which fertilizer should I use in the autumn?
A complete fertilizer is one that contains all three macro-nutrients — nitrogen, phosphorus and potassium. Because phosphorous accumulates in the soil and has been over-applied in many areas, causing algae growth in lakes, streams and rivers, phosphorous has been removed from many lawn fertilizers in Ohio. If your soil test results require application of phosphorous, be sure that the lawn fertilizer you purchase contains phosphorous.
The fertilizer grade designates the percentages of nitrogen, phosphorous and potassium in the product. A 20-5-10 grade fertilizer contains 20% nitrogen, 5% phosphorous and 10% potassium. Thus, a 40-pound bag of 20-5-10 fertilizer contains eight pounds of nitrogen (20% of 40 pounds), two pounds of phosphorous (5% of 40 pounds), and four pounds of potassium (10% of 40 pounds). The grade of any fertilizer will always be listed on the container and always in the order of nitrogen, phosphorous and potassium.
More:Gardening: Tired of mowing the lawn? Consider alternatives to grass for easier maintenance
Tip for fertilizer application
Always apply lawn fertilizers when the grass is dry, and then water it in with a lawn sprinkler if precipitation is not expected. Only apply the amount of fertilizer needed based on your soil test and be sure not to spread fertilizer on impermeable surfaces such as sidewalks, driveways or street gutters as this fertilizer will wash into stormwater sewers that drain into streams and rivers.
Proper applications of lawn fertilizers this fall will pay dividends next spring in the form of early green-up and lush, thick stands of lawn grasses.
Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.
This article originally appeared on The Columbus Dispatch: Tips for fertilizing lawns now and in late fall for lush spring lawns
