Applying compost over established lawns is an effective way to boost the nutrient value of the soil and health of the lawn while minimizing the use of synthetic chemical fertilizers. Applying compost or aged manure over an established lawn with significant thatch buildup is best done after aerating or dethatching. Though this is not a prerequisite, it will increase the speed with which the compost nutrients percolate down into the soil below the grass and thatch. Young lawns or those with little thatch do not require this step.
Purchase bagged or bulk compost in an amount to cover the square footage of your lawn with an even 1/2-inch to 1-inch layer of compost.
Pull the dethatching rake through the lawn in one direction and then make a second pass walking and pulling at a 90-degree angle to the first pass. Alternatively, use an aerating tool to punch holes into the lawn and extract divots of thatch and old soil. Rake up all of the lifted thatch or divots with a flexible timed rake and discard in the trash.
Hand scatter or shovel on an even layer of compost over the entire lawn surface. Start by walking the perimeter of the lawn and covering all of the edges well. Start at one end and walk backwards while casting the compost to avoid stepping on it. Spread the compost in a roughly even layer with the flexible timed rake if necessary.
Water the lawn and freshly sown compost deeply and evenly to wash some of the compost down into the grass thatch. Use a light spray to avoid displacing the compost or flooding the lawn.