What is mulch

 
Mulch is a specially prepared organic or inorganic materials used for covering the soil surface around plants and beds of rows, as well as track, play areas and paths lining. Mulch fulfils both decorative and practical functions ensuring favourable growth conditions for plants and preventing from weeds growing. Depending on the raw material and its structure, there are distinguished different types of mulch.
Organic mulches are the materials of plant origin that gradually decay in soil contributing organic matters thereto and increase its fertility. The most frequently used organic mulching materials are bark mulch, wood chips, sawdust, pine cones, peat, compost, straw, leaves and cut grass mass. In turn, inorganic mulch originates from inanimate nature, and this category include a variety of rock tops, for example, tumbled pebble, gravel, decorative stone, pottery fragments, brick and stone chips as well as synthetic materials - agrofilms, geotextile, mulching films. Sometimes, large vegetable farms also use cut rubber or plastic mulch, but this method is considered to be harmful to the nature and, therefore, undesirable.  
Every type of mulch has its own optimal scope of use. For example, synthetic materials - agrofilms, mulching film, are mainly used for producing horticulture. They effectively prevent from weed growing and retain moisture for a long time, but it is visually unappealing. Also, in steep slopes, where the light organic mulch can’t hold, the inorganic material such as pebbles or decorative stones will fit better. However, unlike organic materials, the inorganic materials will have not practical use in soil enrichment.  
Organic mulching materials not only perform weed control and moisture retention functions, but also protect plant roots from temperature fluctuations and black frost, and enrich the soil with mould humus. However, almost every organic mulching material has its own pros and cons. For example, peat is not effective for weed suppression, but is useful for soil improvement and help to keep soil moisture, if it is applied to at least 10-15 cm thick layer. Wood chips are quite coarse material, which decomposes more slowly than bark mulch and often contain a dye, so it is usually used in small areas where there is a special design effects are achieved by combining different colours. Sawdust is the cheapest, but the least popular mulching material because, if packed, its particles prevent water penetration in the soil; moreover, decaying it consumes a lot of nitrogen. Grass cuttings, straw, leaves are more practical than decorative mulching materials and are available seasonally. In autumn they can be spread out beneath trees to enrich the soil with mould humus and protect the roots from frost-killing, however, be wary of the plant contamination with weed seeds.  

Thanks to its excellent decorative and practical qualities, the most popular and the most widely used organic mulching material is pine bark mulch. This mulch is made from chopped and sieved pine bark and is available of three fractions: smaller, medium and larger sized. Pine bark mulch shall be laid in at least 5 cm thick layer, and about 1 cm layer shall be replenished each year, because the mulch decays with the time and mixes with soil. Fine pine bark mulch is excellent for soil improvement - by mixing it with the soil, soil friability and good air permeability is ensured.