Sustainable Living Through Organic Gardening

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Mulching

Mulching is another tool which organic gardeners can use to increase organic matter content and microbiological activity in their garden soils. Organic mulches on top of the soil reduce evaporation, prevent sunlight from initiating weed growth and insulate the soil. Mulches keep the soil cool when the weather is too hot and warm when the weather is too cold. They also prevent compaction caused by heavy rains.

Another benefit is that mulches provide nutrients for the soil food web and initiate the benefits of those processes in providing nutrients for plants.

Mulch selection is based on the form of nitrogen the plants prefer. Vegetables, annuals, and grasses prefer the nitrate form of nitrogen found in bacterial dominated soils.  Trees, shrubs and perennials prefer their nitrogen in ammonium form found in fungally dominated soils.

Grass clippings, seaweed, compost, and well rotted manure can be used and will lead to a bacterial dominated soil food web. While leaves, straw, and woody plant remnants, can be used as mulches for a fungal domination.

As a general rule, green materials will favor a bacterial soil food web, while brown materials will favor a fungal dominated soil food web. Grass clippings are good but avoid those from lawns which have been sprayed with weed killers. Avoid Cedar chips or sawdust as it contains a natural preservative which will impact the soil micro-organisms.

Coarse material will favor fungal while finely ground will favor bacteria, as will moisture, while fungal prefers dryer mulches. Mixing the mulch into the soil will support bacterial domination while placed on the surface will favor fungal soil food web.

So depending on what you are trying to accomplish select and apply the mulches to meet your objective.

Mulches work great when used in combination with compost. Compost first then cover it with the appropriate mulch.

The earth, land and sea compost made locally is a very useful mulch. Made from sawdust and fish wastes it has no weed seeds. As well it contains sea based trace minerals, vital ingredients for human health.

More information on mulches and their impact on the soil food web can be found in, “Teaming with Microbes”, by Lowenfels and Lewis.