By: David Yost, Merrifield Plant Specialist
To grow healthy grass and keep weeds at bay, the pH level of your soil needs to be between 6.2 and 6.8. Soil pH influences the availability of plant nutrients. If the pH level of the soil is too low, phosphorus remains bound to the soil and cannot be absorbed by your lawn. Without adequate phosphorus, your lawn will not grow vigorously and healthy.
In our Washington, D.C. metro area, our native pH level is generally between 5.0 and 5.5 (on a scale from 0 to 14). A pH level lower than 7 is acidic, and higher than 7 is basic or alkaline. Our native soil pH is great for acid-loving plants like azaleas, rhododendrons and camellias. But to grow thick, healthy lawns in our area, we generally need to raise the pH level of our soil, which is where liming comes in.
Each time you apply lime at the recommended rate, it will raise the pH level of your soil approximately ½ point over the course of a few months. If you need to raise it further than that, you can reapply lime as needed, as long as there is at least a six-week interval between applications. Once you get your soil pH to the desired level, you typically need to apply lime once every two years to keep it at that level.
Spring is an ideal time to apply lime, but it can be done any time of year, except when the ground is frozen. After you apply lime, you need to water the lawn thoroughly. This will help wash all of the product off the grass and down into the soil where it belongs.
Testing your soil
To determine the pH level of your soil you can use a pH meter, a pH test kit, or you can send a soil sample to Virginia Tech and they will send back a detailed analysis of your soil, including the pH level. You can pick up all of these supplies at Merrifield Garden Center.
There are several different forms of lime. Some come in granular form, while others come either pulverized or pelletized and packaged in 50 lb. bags, which cover 1,000 square feet. The pulverized or pelletized packages are ideal for large properties with extensive lawn areas.
Fast Acting Lime is an easy to use, pelletized lime that can be applied at lower rates. Mag-I-Cal is lime combined with humates, an organic supplement that improves soil structure, nutrients and moisture holding capacity. If you are not sure which lime is best for your situation, please ask one of our lawn specialists for assistance.