with brush packing, mulching, and creating a micro-climate
One of the best ways in which to rehabilitate bare, soil eroded areas is to apply brush-packing, or mulching. Brush-packing is done by covering the exposed soil surface with organic plant material such as branches, plant cuttings, leafy material, crop residues, straw, and reeds. This treatment on exposed soil simulates the protective effect of a plant cover.
Brush-packing, or mulching is a valuable soil erosion control method on its’ own because:
- It functions as a protection against rain splash erosion.
- It assists with the retention of moisture in the soil.
- It decreases soil temperature and thereby improves the microclimate for soil organisms and germinating plants.
- It restricts soil and humus movement in runoff by collecting soil and organic material particles against the network of branches or mulch material lying on the soil surface.
- It protects the exposed soil against the effects of wind erosion and also serves to trap windblown sand grains.
- A mulch of chopped branches will protect germinating plants from grazing animals that seek out the new, succulent growth.
- It eventually decays and contributes to the organic content of the topsoil.
- It traps windblown plant seeds and fungal spores.
- It creates cover habitat for soil-living animals that burrow and help to aerate the soil.
Brush-packing and mulching is spread evenly over the soil and should cover at least 70 – 75% of the soil surface to effectively prevent soil erosion. How much to put down depends on the type of brush or mulch used – too little will not protect the soil adequately and too much will suppress plant growth. A good rule of thumb is that the material used, must not form a sealed cover. Sunlight, water, and air must be able to freely infiltrate the layer to ensure successful plant germination and growth.
In some arid habitats a deep layer of mulch actually prevents the germination of some succulent dwarf shrubs. This is because those arid habitats do not naturally support a dense layer of mulch and the seeds of the plants are able to germinate in harsh conditions. The mulch will, however, help to prevent further soil loss where necessary.
When using branches, take care to cut the material up so that most of it lies relatively flat on the soil surface, giving it maximum protection. Branches can be packed in a 200mm thick layer. When using reeds, cut them up into short lengths and pack no thicker than about 100mm, as they can form a dense seal when they decompose, the material being finer than brush. When using finer organic material, it is a good idea to spread the material together with some coarser branch material so that a sealed soil surface cover does not form.
Brush-packing can be used in conjunction with almost any other soil erosion control method or as a method on its own. In Figure 1, it is used together with erosion “fences”. The low fences are constructed across sloping sites to hold the brush-packing in place in strips across the site. In many cases, brush-packing alone may be all that is required. In windy areas, finer material may have to be held down with wire netting, geotextile or wire strands pegged over the brush-packed surface. Sometimes a few stones or bigger branches scattered over the mulch layer will be sufficient to prevent removal by strong wind.
Brush-packing or mulching is thus an ideal method for controlling water and wind erosion on exposed, degraded soil surfaces in areas where a plentiful source of harvestable brush material is available. In areas where brush or mulch is limited, use should rather be made of the puddling method, or organic geotextiles, such as Soilsaver, which is made from jute can be used as a ground cover.The full article is for subscribed members only. To view the full article please subscribe. It’s FREE!Log In Register
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