Causes of a Yellow Lawn
When a lawn turns yellow, there are several factors that may be to blame, including bacterial and fungal diseases, pests, nutrient deficiencies, and a pH imbalance. To successfully treat this common lawn problem, it's important to first determine the underlying cause of the discoloration.
Causes of a Yellow Lawn
Drought or dormancy can lead to a yellow lawn. This is because certain grasses go dormant during their off season, causing them to yellow. While warm-season grasses go dormant during the winter, cool-season grasses are usually inactive during the summer when it's hot and dry.
To avoid a drought or dormancy issue, it's recommended that a lawn is properly watered during times of drought. For those with warm-season lawns, you can use annual ryegrass to overseed in the winter. This will help hide dry "yellow" dormant warm-season grasses.
A pH imbalance can result in nutrient loss. Lawns suffering from nutrient deficiencies commonly have yellow leaves. In addition to discoloration, nutrient-deficient lawns are unable to prosper because they lack essential primary, secondary or micronutrients needed for proper plant growth.
If your lawn is showing signs of a pH imbalance, you may want to perform a soil test. This test measures the pH level of soil. If the pH level is above 8.0, the soil is too alkaline. Iron chlorosis is a common problem in overly alkaline soils (pH above 7.5). This means that iron is unavailable to plants. To lower the pH level, you can apply aluminum sulfate to the soil. If the soil is too acidic (below 6.0), you can add lime to slight raise the pH level. If the lawn is still yellow after treatment, then there's another factor at work.
Chinch bug damage usually results in yellow patches throughout the lawn, as opposed to an even yellow. Chinch bugs are especially harmful because they draw nutrients and water from plant leaves, causing them to lose their lush green color. To discover if chinch bugs or other insects are to blame, use a coffee can with both ends removed (use a can opener to open the bottom). Push the coffee can into the soil about 2 inches deep. Fill the can in the soil with soapy water. If the bugs are present, they will float to the top of the water.
Since drought stressed lawns have more problems with chinch bugs, watering the lawn may prevent these pests from taking over. Cutting back on fertilizer use and raising the mower height can also help.
Nutrient deficiencies can cause lawns to discolor, especially those that lack a primary nutrient like nitrogen. This nutrient is responsible for aiding shoot growth and turning plants green. For this reason, a nitrogen-deficient lawn will weaken and turn yellow.
Testing the pH level is the quickest way to determine if the lawn has a nitrogen deficiency. If the pH level is normal, use fertilizer to increase the amount of nitrogen found in the soil. If the pH level is too low, you can add lime to increase the soil's level. This will increase the availability of nitrogen to plants. If the lawn is still yellow, you may want to use a high nitrogen fertilizer like one that has a ratio of either 5-0-0- or 10-0-0.
It can be difficult to determine the exact cause of a yellow lawn; however, contacting a professional lawn care company can reduce the time spent pinpointing the problem and lead to a quicker recovery.