What Should I do if newly installed grass sod is turning yellow on isolated areas?

If newly installed grass is turning yellow on isolated areas, there are several potential causes and steps you can take to address the issue.

1. Check soil moisture levels: The first step is to check the moisture levels of the soil in the affected areas. Yellowing can be a sign of both under- and overwatering. If the soil is too dry, increase the frequency or duration of watering, but if the soil is waterlogged or poorly draining, reduce the frequency or duration of watering.
   
2. Check for pests or disease: Yellowing can also be a sign of pests or disease, so it's important to inspect the affected areas for signs of infestation. Pests like grubs, chinch bugs, and armyworms can damage the grass and cause yellowing, while diseases like fungal infections can also affect the grass. If pests or disease are identified, you may need to treat the affected areas with appropriate treatments or consult with a professional lawn care service for guidance.
   
3. Check for soil nutrient deficiencies: Yellowing can also be caused by nutrient deficiencies, particularly nitrogen. You can apply a balanced fertilizer to the affected areas, following the manufacturer's instructions for application rates and timing. Be sure not to over-fertilize, as this can lead to other problems like burning the grass.
   
4. Check for soil compaction: Soil compaction can also cause yellowing by preventing roots from accessing air, water, and nutrients. Aerating the affected areas can help to alleviate soil compaction and promote healthier root growth.
   
5. Monitor and adjust: Finally, it's important to continue to monitor the affected areas and adjust your lawn care practices as needed based on weather conditions and other factors. Be sure to continue watering deeply and infrequently, and adjust your fertilization and pest management practices based on the specific needs of your lawn.
   

In summary, yellowing on isolated areas of newly installed grass can have several potential causes, including soil moisture levels, pests or disease, nutrient deficiencies, and soil compaction. By identifying and addressing these issues through proper lawn care practices, you can promote healthy root growth and ensure a lush, green lawn.