Topsoil is the top layer of the soil, and it should be nutrient-rich and high in organic matter. You may already have rich, natural topsoil ready for planting, but if you do not, all grades of topsoil are available in bags and in bulk from commercial suppliers. The three grades of topsoil are premium, general purpose and economy. When buying topsoil, the Royal Horticultural Society recommends checking it for weeds, large stones, and other contaminants.
Premium grade topsoil is the most expensive of the three grades and has a good structure and a loamy texture, which is to say it is made up of sand, clay, and organic materials. It is very fertile and nutrient rich, and nurseries mix it with compost for container grown plants. It is suitable for creating new plant beds, for gardens, for the most demanding plants and where there will be frequent cultivation.
General Purpose Grade
General purpose topsoil may be natural topsoil, some manufactured topsoils, premium topsoil that has been downgraded due to poor handling, or a mixture of the three. It is sold in different screen size grades that are based on the maximum particle size. General purpose topsoil is suitable for good agriculture and horticulture, as a base for new lawns, and for some new plant beds. The finer screen size grades are useful for top dressing lawns, while the coarser grades are ideal for sod and turf laying.
Economy grade is the least expensive and lowest quality of the three grades. It is made from lower quality topsoil that may be mixed with crumbled or crushed mineral matter. It may contain river silt, green sand (sand or silt rich in glauconite), and/or glacial moraine (soil and rock debris deposited by glacial action.) It is not screened for particle size and is most commonly used to build up areas where volume is more important than soil quality. It is useful for woodlands, parks, and low-use grassland.