Mulching is an important aspect of organic gardening as the mulch is able to achieve many goals. When deciding on a form of mulch, whether it is to preserve the soil structure, develop soil structure, preserve moisture or simply to present a decorative surface layer there are some other considerations.
These include:
Chemical
- Consideration of the carbon to nitrogen ration of the mulch
- Nitrogen draw down
- Ph balance of the soil and the effect of the mulch
Physical
- Mulchers
- Mulcher mowers
Philosophical ethical.
- Non-organic sources.
Problem solving
The C:N ratio refers to the relatively amounts of carbon and nitrogen in the mulch. Too much of either may cause problems. The less nitrogen the longer a product takes to break down, too much nitrogen and decomposition is too rapid and becomes unthrifty. Generally something like wood chips has a great deal of Carbon and little nitrogen but leafy green weeds are lost quickly and must be replaced.
Balanced mulch allows for the growth of soil biota and the gradual breakdown and so slow release of nutrients.
Sawdust is about 500 to 1, Hay is 25:1 as is horse manure, grass clippings 20:1,
alfalfa 12:1 and blood and bone 7:1.
Authorities have different opinions about the best ratio – anywhere from 12:1 to 50:1, probably somewhere between 20-35 : 1 is suitable.
Nitrogen drawdown.
The life in the soil that will break down the mulch, releasing nutrients needs nitrogen to grown and survive. If this is not supplied in sufficient amounts from the mulch it will be taken from the soil’s reserved thus depleting it. Woodchips, for example, need some nitrogenous material placed beneath it. There is no point in placing nitrogen (so blood and bone) on top as it is likely to give off its nitrogen in the form of ammonia to the ambient air.
The PH balance
Ph balance is simply the relative acid to alkali balance. This can be measured easily from a store bought kit. Some plants prefer a slightly alkaline soil whereas others such as blueberries, azaleas, and rhododendrons like a more acid environment. The scale is 1 to 17 with 7 being neutral, usually from 5.5 to 7 is fine. A highly nitrogenous fertilizer is likely to make the soil more acid hence if the soil is edging toward being too acid a neutralizing agent such as lime or dolomite (calcium magnesium carbonate) is used.
Mulchers - shredders
Shredders or mulching machines are very useful in cutting up woody and semi hard plants into a finer mulch more easily laid out on the garden and which breaks down more rapidly. Because the mulch is finer, weeds are lass likely to penetrate.
Mulcher mowers.
Some lawn mowers are also mulcher mowers and cut the grass more finely so making it easy to use as a mulch. Even ordinary motor mowers can be run over a pile of clippings to reduce them to a finer product.
Organic considerations.
There are always difficulties when bringing in vegetation from outside. Peat may be an environmental concern in some parts of the world. Residual synthetic chemicals on plants – especially on high input crops such as sugar cane allow the importation of undesirable products. Finally paper used should be unbleached so that dioxins that leach from magazine and office papers are not added to the garden.
Basic Problem solving
If the mulch seems to become too wet, fork in a more high carbon addition.
If it smells – too much nitrogen – add carbon
If it is not decomposing wet it and consider adding more nitrogen.
If weeds grow through :pull them and consider adding more mulch
If it is dry beneath the mulch - aerate .
