Now is the time of year that I start getting phones calls regarding spring renovations that went wrong. The complaint is usually that they brought in soil and seeded in the spring and now they have a lot of crab grass and very little actual grass. They are particularly frustrated because they often have spent a lot of money and expected to have a lush lawn by summer.
Spring is actually a very difficult time to seed a lawn because it is the start of weed season and of hot dry weather in general. Grass is a plant that, even when well established, likes cool wet weather. Those little seedlings don't stand a chance to the weeds that are inherently suited to hot, dry weather and poor soil. However, the good news is that Fall is a great time to reseed or renovate your lawn.
A couple pointers:
1. If you bring in top soil or even compost, test the pH and adjust accordingly. It is always good to test your pH every couple of years. Cornell Cooperative does a soil pH test for a buck.
2. Aerating or dethatching can help improve soil to seed contact which will increase the amount of seed that germinates.
3. It helps to remove the crabgrass plants so that they don't drop their seeds on the soil. Pulling out the plant will also loosen the soil as well.
4. Keep the area manageable in size. If your seed completely dries out before it germinates its lost its viability and won't germinate no matter how aggressively you water after the fact. It's hard to keep up the water schedule if you don't have a sprinkler system.
5. Use a starter fertilizer, preferably organic.