Topsoil is the necessary top 2 to 10 inches of soil in any lawn or garden. Without a good layer of topsoil, plants will not grow well, if at all. When you encounter a large area covered with gravel that you want for agricultural use, it is possible to lay topsoil over the gravel and plant a productive garden or healthy lawn. Though the process is labour intensive, you only need basic tools.
Determine how much topsoil is necessary for the project. Measure with a tape measure the length and width of the gravel area on which you want to place the topsoil. Decide the desired depth of the garden area--a depth of 4 to 6 inches for a lawn and eight to 10 inches for a vegetable garden is ideal. Multiply the length by the width by the depth--this is the volume of topsoil necessary for the project. For a garden 12 feet long and 12 feet wise, as well as 10 inches deep (approximately .8 of a foot), you would multiply 12 by 12 by .8 to determine that you need 115 cubic feet of topsoil.
Level and smooth the gravelled area with the rake.
Shovel the required amount of topsoil onto the gravel.
Smooth and level the topsoil with the rake.
Apply water to the new topsoil with the sprinkler or hose and hose sprayer.
Some experts say it is preferable to remove as much gravel as possible before laying topsoil. It may be desirable to use wood, rocks or cement boundaries around the area to ensure retention of the topsoil. There are a variety of topsoil calculators available online to assist with the necessary calculations.