The appearance of our lawns has a lot to do with the curb appeal of our homes.
Yellow spots like these can be caused by several things including low spots in the lawn. After rain the water can collect and drown the grass especially if the lawn does not drain well. In this case adding top soil in the low spots can help. If the spots are deep you would want to reseed the area as a deep layer of top soil will take a long time to have grass grow back into it on its own.
These yellow spots can also be caused by our pets urine. You could either water the area well immediately after the dog urinates (who has time for that) or try spreading a handful of sugar over the spot. The sugar will neutralize the nitrogen in the urine and you should soon see new grass growing.
A lush green lawn not only looks better but will have fewer weeds. The hard part is getting it to that stage. Some of the things you can do include:
1) Don't mow too short. In the cool weather grasses we have here, you should mow at about 3". This provides a good surface area for photosynthesis, provides shade for the soil and helps with water retention. Cutting the grass shorter stresses the grass and dries out the soil faster.
2) Water in the early morning. Watering at night can lead to disease as the grass may not absorb the water before dew sets in making the lawn too wet.
3) Mulch the grass clippings. A good mulching mower will chop the grass into small pieces that will break down and add nutrients back into the soil.
4) If you have a thin lawn consider over seeding OR using a weed and feed product on the lawn. If you try to do both in the Spring you need to over seed first, then wait 5 weeks after germination to add the weed and feed type products, depending on the product. Many weed killers will prevent new grass from germinating or kill the young grass. Waiting 5 weeks after germination gives the grass time to mature before the weed killer is applied. Another option is to weed and feed in the late Spring and over seed in the Early Fall.