Soil that has little space between the soil particles is considered compact. Severely compact soil has many disadvantages such as inhibiting root growth and limiting the amount of water than the soil can hold. However, soil that is slightly or moderately compact can help improve seed contact with soil, which can in turn increase seed germination rates. It can also help the roots absorb some nutrients such as phosphate. Hook your water hose up to a sprinkler or irrigation system, and with the use of a roller, you can compact your light and airy soil.
Water the area in which you want the soil compacted for about an hour or two. Water it slowly so the water seeps into the soil as it is being watered rather than puddling on top.
Repeat this watering for two or three days. Continue to avoid puddling and also muddy soil conditions. The water should be draining into the soil, getting the deeper soil moist rather than sitting on top making a sloppy mess.
Compact the soil with a roller. There are push rollers as well as rollers that can be hooked up to the back of a tractor. The heavier the roller, the slower you go and the more passes you make, the more compact your soil will get.
Dig a 6 inch or wider hole that is 18 to 24 inches deep to conduct a soil drainage test to make sure you have not created soil that is too compact. Fill it with water and let it drain overnight. The next day, refill the hole to about 2 inches from the top. In several hours, measure how much water drained and divide by how many hours have passed. If it averages less than 1/2 inch or less an hour, your soil is too compact or just doesn't drain well. Till and aerate your soil and amend with organic matter.