Cultivating or tilling the top layer of soil before planting seeds allows air into the soil and activates the nutrients for the seeds to absorb. They soil should be fairly dry when this is done so if you can make compact moist balls when squeezing the dirt with your hand, then it should be allowed to dry a little longer.
Continuous cultivating around established plants, with a hoe or claw type tool, keeps the soil aerated and aids in weeding.
Any material such as grass clippings, hay, or plastic sheeting, used around the base of plants is called mulch. Mulch protects roots from the freezing and thawing of the ground, as well as helps retain moisture during dry spells. It can be a deterent to prevent existing weed seeds in the soil from developing, but many weed seeds are airborne and will land on your soil & mulches and develop anyway. An important advantage of organic mulches is that they will eventually compost and further enrich the topsoil.
Avoid using fallen leaves as a mulch because when wet, they form a heavy soggy barrier which prevents air from getting to the soil.
If you have any Cultivating & mulching tips, please share them with us on the Community Forum.