In horticulture, the word mulch is used to describe any material that covers the surface of the garden for a more aesthetically pleasing look, to protect from wind or water erosion, to moderate soil temperatures, reduce the evaporation of water or simply keep weeds down to a minimum, but neither compost, nor the product from a compost pile is mulch, compost is soil amendment.
Cutting up landscape debris, such as putting branches and leaves or dry grass clippings through a chipper, can be called mulching, but this process is more often used in creating a more efficient C/N ratio for the compost pile and eventually a more efficient soil amendment than it is in being directly used as a mulch per-say.
Therefore, what is mulch? Mulch can be a layer of plastic, gravel, sand, white clay, fine sawdust, wood chips, mulched landscape refuse even half-done compost, basically, anything that keeps weeds, moisture and nutrients in the ground near the roots of the plants you are looking to grow in your garden bed, mulch is nutrient protection from the surface elements.
Mulching organic materials to compost means to shred them up, yes, and has become very much a bit of a trend in the US as of late, especially to use the word openly in hardware stores to sound astute; but applying mulch to the garden, does not mean putting compost humus or even half-done compost directly into the soil around the plants, this is applying amendment to the soil, to enhance nutrients and growth, not preserve nutrients.
These are two very different concepts completely; mulch is to preserve nutrients and compost is to enhance nutrients.
The shredding or mulching process makes decomposition or composting quicker, allowing microorganisms to get to the breakdown stages more efficiently while composting carbons and nitrogens into a fine black humus that is nutrient rich in all the things plants need to grow big and strong.
The role of mulch is to protect those same nutrients that plants need, and usually, the surface is a rather wild place, that can rip nutrients away quickly, and while mulch made of half done compost will tend to continue breaking down under the surface, eventually becoming soil additive, that is not the initial use when applied to the surface.
Any mulch made from organic refuse, such as wood chips, sawdust or half-done compost, are sure to continue the composting process, while acting as a protective layer, but once their service as a protective layer has come to an end, and they broken down so much that they are ready to become a soil amendment, a new layer of mulch is then required.
This process of replacing mulch, over and over, is one of the reasons why many people choose to use sheets of plastic and other non-organic substances as mulch, as it still acts as a protective layer for the nutrients, but doesnt ever breakdown and become soil amendment.
What is mulch? Mulch is any substance that is used to create a protective layer across the surface of the garden, keeping nutrients in the ground, near the plant roots, while compost is nutrient rich soil amendment, that plants need to enhance their growth and stay happier throughout the season.
Related Website:
The Compost Bin - Learn about composting.
External Links:
Mulch Calculator - How much mulch do you need for yor landscape?
Mulching Trees and Shrubs - via NC State University
