It is a tricky situation for many people to decide or figure out how much topsoil is required when it comes to their planting requirements.
The answer can vary a great deal and is dependent on whether it’s for raised bed gardening, planters, a new lawn or a traditional garden plot. You also need to have an idea about why you are adding the topsoil.
One reason people apply a topsoil to their planting area is because their soil just isn’t up to the standards they require. It could be you just need to add topsoil for general purposes such as adding organic material to you already existing soil. This would give you maximum water retention as well as stimulate plant growth. The topsoil can be mixed in with the existing soil for these purposes.
Another reason many add topsoil is for filler or top dressing of the gardening area. It will provide the same benefits such as holding water better and increasing your existing soils organic capacity. You can just spread the topsoil over the planting area and use it without mixing it into existing soil. It will be suitable for any type of planting. This is also so you can put a new garden area in where there was not one before, such as along a fence or in the center of a yard.
For either of these situations and to know specifically how much topsoil is required, you should calculate it per inch. For each inch of topsoil you want it will take about 3 cubic yards of topsoil to cover 1000 square feet. So, if your topsoil treatment area is 10,000 square feet it would take about 30 cubic yards of the additional topsoil to spread it one inch thick.
But for many reasons one inch is not necessarily the right amount. Most areas will benefit from more, three to four inches and in some circumstances up to six inches of topsoil coverage. Needing to know how much topsoil that is required depends on what the project is.
For a full out and out lush lawn you should consider putting a maximum of six inches of topsoil coverage to give it a firm start. It won’t take quite so much if you are adding sod instead of seeding your lawn. The topsoil covers everything; rocks, bare spots or low spots. A six inch or more depth of topsoil will usually guarantee that grass seeds take hold no matter what kind of soil or area you had to begin with.
If you are trying to decide how much topsoil is required for container planting then you can use the prepared topsoil to fill containers. The prepared topsoil alone won’t hurt plantings of any kind so just fill containers and go. The same goes for raised bed gardeners. Of course if you have pretty good planting soil and you just want to add topsoil for the organic benefits use the one inch calculation for the area and mix it in with existing soil about half and half.
How much topsoil is required to just support new fruit trees, shrub or single plants? If you only have a few plants or trees to set out you should spread about a four inch depth of topsoil. The area size depends on how big the root system of the plant or tree is. It needs to be enough to cover it. You’ll want to pack prepared topsoil about four inches over roots and around the plants.
The same process can be applied to existing trees or plants. Just put about a four inch depth of the topsoil all around the base of your plants or trees to add to their nutritional needs and water efficiency.
If you have an already existing or new spot for a garden where you are planting seeds then follow the calculator to apply one inch of topsoil to the top. (Remember, 3 cubic yards of topsoil per 1,000 square feet of existing soil.) If you want to till it into the ground just for soil amendment a minimum of three inches is suggested. This should give you a nutrient rich soil that is suitable for vegetable or flower garden planting.