Organic mulch is a layer of loose organic matter such as straw, grass clippings, leaves and other similar materials used for covering the soil surrounding the plants or which is positioned between rows of plants to protect the soil. The mulch helps in maintaining favorable condition of the soil. Because it is derived from plant materials, it decomposes well which has several positive effects, both on the ground and on plants.
Living Mulches or ground covers:
Cover crops have many advantages in gardening systems. One of the most important is undoubtedly the elimination of weeds. Species of cover crops with the main crop cultures are sometimes called choking or living mulch. Species for covering the soil can be grown before or after the growing season. This allows the removal of weeds and provides other benefits outside the growing season too.
A good cover crop used as a living mulch should be able to settle quickly, tolerate traffic on the field, tolerate drought and poor soil fertility and have low maintenance costs.
Living mulch consists of plants such as legumes (mustard, clover and white clover in particular), the phacelia, spinach and other species that grow close to the ground and can hinder the development of weeds and enrich the soil in organic matter and nitrogen. They act as cover crops and may have to be ultimately killed when they start competing with the main crop.
A large number of plants can be used for this purpose, the only two requirements are the ability ‘to thrive even if sown very dense and high speed of germination’. This so-called “living mulch” can ‘be used both to keep the inter-row clean and free by the cultivation and keeping the soil from being infested if intended to be used at a later time.
This mulch is particularly effective against perennial weeds such as yarrow, mallow canapina, marshmallow, the gigaro, the thistle, the clematis, the bindweed, couch grass, horsetail, the mint, the Phytolacca, the plantain, etc. In these cases one should cover the infested area, continuously, for at least one to two years with a thick layer of mulch distributed in late February and renewed every six months. A treatment of this kind is the best solution to effectively eliminate weeds.
Effects of Mulch on soil:
1. Physical Effects.
- When the organic mulch mixes with the topsoil, the material keeps the soil moist and generally enhances the growth of roots.
- Significantly reduces evaporation.
- The mulch improves and stabilizes soil structure, acts as a buffer, reduces soil compaction favoring moisture retention.
2. Chemical effects.
- The mulch in tropical climates decomposes in 2 to 3 months, releasing small amounts of nutrients that can be used by plants. In temperate climates decomposition delays to 3 to 5 months.
- There may be a deficiency of nitrogen in plants due to nitrogen intake by microorganisms that decay mulches. To avoid this, you must apply a liquid organic fertilizer to plant as nitrogen supplement.
- On the contrary, some living mulches as Legumes carry out Nitrogen fixation.
- They might increase or decrease the pH of the soil.
3. Biological effects
- The organic mulch serves as a food for many microorganisms found in the soil.
- It also helps to maintain a constant temperature for the activity of the microorganisms.
- Sometimes, the mulch can introduce unwanted organisms to the soil, such as fungi, bacteria and nematodes.
- It is important that during the rainy season, mulch is removed to prevent plant diseases and pests.
Advantages of mulches:
- living mulch keeps the earth clean, severely limiting the development of competing weeds.
- Living mulch maintains ventilation and flexibility by loosening the soil and prevents compaction and crusting on the surface during heavy rains.
- Organic mulch provides a source of humus after degradation favorable to soil fertility and plant vitality. It promotes biological life and work of earthworms.
- Reduces drying in summer.
- Living mulch provides protection to plants against cold.
- Living mulches may ultimately act as fertilizers when mixed with the main crop.
All mulches, whether living or organic, are very useful for organic gardening as organic gardening restricts the use of synthetic fertilizers. The best that a farmer can do to his organic gardening efforts is to use mulches to keep plants healthy and the soil weed free and drought resistant.