Lawn grasses grow best when the soil pH falls between 6.0-7.0. Over time, acid rain, nitrogen fertilizers, and other factors can cause pH to drop too low for optimal turfgrass health. Applying lime raises pH back into the target range and provides much-needed calcium. But how do you accurately assess if your lawn would benefit from liming? Watch for these key signs that indicate your grass is suffering from excess acidity and needs a pH adjustment.
Test Soil pH Directly
The most definitive way to determine your lawn’s acidity status is to directly test the pH of soil samples. Home soil test kits provide a quick and inexpensive means to check pH. To use one properly:
- Collect samples from several areas around the lawn at a depth of 2-4 inches where roots are most active.
- Combine and mix the samples thoroughly to get an average reading.
- Add the indicator powder or solution according to kit instructions.
- Compare the color that develops to the reference chart to identify the pH number.
- Results between 6.0-7.0 are ideal. Below 6.0 indicates liming is needed.
For the most accurate analysis, you can send samples to your local agricultural extension office for professional testing. This provides pH numbers plus tailor-made lime recommendations based on your lawn’s specific needs.
Assess Grass Growth and Color
Visible symptoms in the lawn’s appearance can also signal overly acidic soil conditions requiring lime:
Poor, Stunted Growth
- Grasses fail to establish or have thin, patchy growth despite adequate irrigation and fertilization.
- Bare areas of slow growth allow weeds to invade which tolerate acidity better than grass.
- At very low pH below 5.5, turfgrass may nearly completely die out due to extreme acidity.
Yellowing Grass Blades
- Initially leaf tips and margins turn yellow as acids burn these areas first. Eventually the yellowing can spread across the entire blade.
- Lime green color or overall chlorotic, nutrient-deficient appearance results from the grass being unable to take up nutrients properly at low pH.
- Rust fungus outbreaks also increase in acidic environments.
- Correcting low pH by applying lime promotes lush, thick, vibrant green turfgrass growth.
Identify Acid-Loving Weed Invaders
Certain weed species tolerate or prefer acidic soils. Spotting these invaders taking over your lawn can indicate pH has dropped too low:
Clover and chickweed thrive at lower pH levels, crowding out grass.
Moss forms thick green mats and is a common invader of acidic lawns.
Low-growing broadleaf weeds like common sorrel and prostrate knotweed favor acidity.
Liming rebalances soil conditions to better suit desired grasses and limit acid-loving weed problems.
Notice Soil and Thatch Changes
Other visible indicators that soils are too acidic include:
Excess Thatch Buildup
Low pH impairs microbiological activity that decomposes thatch. Liming raises pH to support better decomposition and thinning of thatch layers.
Compacted, Poorly Draining Soil
Acidic conditions promote tightly bound, dense soil structure leading to compaction issues and poor drainage. The calcium in lime improves structure. Check for stunted root growth.
As pH drops, iron and aluminum ions leach from the soil. These coat concrete surfaces like driveways and foundations with orange stains and splotches when they oxidize and deposit.
Know When to Apply Lime
If multiple signs indicate your lawn has very low pH, have your soil tested to determine precisely how much lime you need to raise it to the proper level. The ideal times to apply lime are early spring or fall, which allows it to fully incorporate during the off-season for maximum effectiveness the following growing year. With attentive monitoring and properly timed liming, you can maintain ideal acidity levels for robust grass growth.