By Tom Hughes, Feb 3 2018 09:50PM
What is Mulch?
Mulch is any material or substance that is placed on top of the soil in order to cover it. The Eco Gardener prefers renewable, multi-functional mulches, and endeavours to source them as locally as possible. Woodchip and leaf litter are great choices of mulch in most garden settings, but a plastic sheet can be used as a mulch, and so can cardboard, straw, and old carpets!
Renewable, biodegradable mulch materials include
Woodchip - Perfect for weed suppression and supporting woody perennials
Straw - Higher in Nitrogen and a very useful material for soaking up moisture
Grass cuttings - Very N-rich, and can tend to get slimy in large quantities
Food waste - Rich and well-rounded nutritionally but anaesthetic
Manure - Extremely Nitrogen rich
Cardboard - Carbon rich and good for layering and weed suppression
Other materials include:
Plastic sheeting - Effective at weed suppression and reducing evaporation
Rocks, gravel, stone - Natural and aesthetic, but not particularly effective
Carpet - Good heavy material for covering compost piles
What does mulching do?
By covering the soil and reducing its immediate contact with the atmosphere, it becomes more akin to how soils are found in nature. Woodland soil is buried deep beneath layers of organic matter and is rarely exposed to sun or wind, which are harmful to many soil dwelling lifeforms. Even in open floodplains the soil is mostly covered and protected by vegetation, and when bare soil is exposed, it is rapidly colonised by neighbouring plants, dormant seeds, and those that recently arrived from elsewhere.
The direct and indirect effects of mulching
1) Reduces evaporation from the soil and rhizosphere (root zone); thus it lowers the demand for irrigation by up to 50%.
2) Supports and enhances the soil community for months/years (depending on your choice of material);
i) Creates habitat for soil micro and macrofauna - the vasy majority of which are beneficial to plant growth
ii) Feeds and nourishes life at the base of the food chain
iii) Lowers the demand for fertilisers
iv) Helps control plant pathogens
3) Suppresses the germination and growth of fast-growing annual wild plants (weeds);
i) Reduces the demand for weeding
ii) Reduces competition for space, water, and nutrients
4) Buffers soil temperatures and moisture levels;
i) Reduces abiotic stress for the plants
5) Improves soil structure and texture;
i) increases oxygen levels by creating more pore spaces
ii) aids root expansion and therefore resource capture
6) Looks natually tidy and attractive
7) Protects the soil from erosion by wind and rain