Top dressing is the application of bulky material to the surface of the turf. This is a key part of a professional groundsmans annual activity but rarely applied regularly to domestic lawns. The top dressing will consist of soil, sand and peat mixed in differing ratios dependent upon the application and type of soil applied to.
The benefits of top dressing are that minor hollows may be smoothed out to provide a truer, more level surface, the nature of the existing subsoil may be altered and improved and the top dressing may stimulate and improve plant growth.
For sandy soils which are relatively free draining a mix may be 4:1:2 (soil, sand, peat) to enable greater or longer water retention. Heavier soils may require a mix of 2:4:1 to try to break down the soil and allow improved drainage whilst for loamy soils the mix may be 4:2:1.
The best time to apply a top dressing is in early autumn, probably after a scarification (in conjunction perhaps with an over seeding) and after an aeration, especially in heavier soil types.
Apply as evenly as possible with a mechanical top dresser or manually using a lute, drag mat or the back of a rake. The objective is to spread it evenly so as not to create new humps or depressions and to get it into the sward of the turf.