Why Is Seedling Grass Turning Yellow?

PH Levels

• Although lawn grasses have different pH requirements, depending on the variety and cultivar, most prefer slightly acidic soils. High pH levels are often the cause of seedling yellowing. Interveinal chlorosis, or blade yellowing, is common in grasses that grow in soils with pH levels above 7.5. Soils with high pH levels usually have too little iron. High pH levels can deplete the soil of several micronutrients, such as copper, zinc and manganese.

Nutrients

• In addition to a deficiency of iron that leads to high pH levels in the soil, yellowing in grass seedlings can indicate improper levels of other nutrients. Nitrogen plays a major role in creating the green color in grass and other plants. Soils with inadequate amounts of nitrogen can cause yellowing of the grass at an early age or after the grass matures. Young seedlings may appear pale green at first, turning yellow and dry as they grow. Lack of nitrogen in the soil can cause poor germination and sparse growth in lawn grasses.

Soil Preparation

• Testing the lawn soil prior to planting grass seeds is one of the most important steps in creating a healthy lawn and landscape. A soil test provides valuable information regarding the health of your topsoil and the proper methods for treating any unhealthy soil conditions. Loosening and enriching your existing soil by incorporating vegetative compost can help boost germination and promote healthy, green growth in lawns.

Treatment

• Although it is best to treat lawn sites prior to planting grass seed, prompt treatment that adjusts improper pH levels and nutritional deficiencies can help eliminate yellow growth in seedlings. Adding iron in the form of ferrous oxide will help treat an iron deficiency, while applying elemental sulfur will help lower a high pH level. Apply a nitrogen fertilizer to promote greening in yellow grass seedlings, following the instructions on the fertilizer label. Even moisture during the early growth stage helps boost the health of grass seedlings and encourages the absorption of fertilizers and soil amendments.