Mulching is the process of covering bare garden soil with a porous material to improve the condition of the soil underneath. How the soil is improved depends upon what type of soil you have, what materials you use and how thick you apply the mulch. In general, mulch is used to provide the following benefits:
- Reduce weeds by blocking sunlight from reaching the soil and making the resulting spindly weeds easier to pull.
- Reducing water requirements by preventing evaporation and keeping the soil cool.
- Keep the soil cooler in summer and warmer in winter. A good layer of mulch can prevent the summer sun from wilting tender greens and the winter cold from killing tender roots and growth tips.
- Potentially modify the pH of the soil over time.
Performance of mulch
How well the mulch performs any of these functions depends upon the material selected as well as the factors listed above. Organic materials decay over time; that decay may enrich the soil, encourage earthworms, modify soil pH, loosen it or bind it. Again, the actual effect varies according to soil type and materials chosen. For example; oak leaf mold is an excellent choice for lowering the pH of alkaline soil, but may not be readily available in your area. Decomposed limestone helps raise the pH of acidic soil. In general, inorganic mulch is more permanent than organic mulch but has little benefit to the soil’s fertility or texture. River gravel won’t help earthworms grow but won’t wash away like shredded leaves and branches. It is entirely up to you to decide whether enriching the soil with an organic mulch that has to be amended every year or two is more important than using a decorative gravel that never decays but provides no nourishment. Check with your local garden center to see which materials are most readily available and for what price. Any nurseryman or landscaper will be able to discuss the benefits of each.
PURPOSE OF MULCHING
1. Conservation of soil moisture
Mulching prevents evaporation of moisture from the surface. It, thus, poses a restrain over the forces required to pull water from subsoil. Mulching further reduces loss of moisture by breaking up the the flow of air across the soil surface. Mulching minimizes soil compaction, and help ensure permeability of soil, prevents excessive run-off, checks soil erosion and consequently favors percolation of water in sub-surface layers of soils.
2. Regulation of soil temperature
Mulch acts as an insulation layer over the surface of the soil. It prevents emancipation of the heat absorbed and thus maintains average soil temperature slight higher than that of unmulched soil throughout the year. During summer, mulches prevent direct hit of soil surface and thus the average maximum soil temperature under mulched field remain lower. Mulching has its role in minimizing freezing in soil which is a haunting problem especially in temperate region. It minimizing almost equal to its thickness, applied over the surface of soil.
3. Suppression of weed growth
Needless to mention, almost all vegetation requires light to keep themselves alive. Mulches are especially those which impermeable to light (black polythene), excludes light from striking the surface of soil and makes the weed-the major competitor of crop, unable to grow. Small, low growing and less vigorous weeds are very easy to control by spreading mulch.
4. Prevention of soil erosion
Mulches minimize areolation effect of air, slowed down the impact of rain shower and help prevent the erosion of soil. It also prevents loss of sol brought about by rain splashes. Mulching improves physio-chemical characteristics of soil if followed continuously year after year over a particular piece of land and thus minimizes vulnerability of otherwise light textured soil to soil erosion.
5. Control of pest and disease
Many pests and diseases are detracted from the hosts when certain kind of mulches is applied. Neem cake and its kernel, horse manure etc. are effective against many soil dwelling pests and pathogens. The incidence of mildew disease is minimized following moisture retaining mulching. Warm and moist conditions maintained under mulch favor the growth of many beneficial microorganisms which may have predatory role in counteracting the pest survival. Pests like midge, gooseberry sawfly and raspberry beetle have been found to be controlled following watering and covering over night with a sheet of black polythene.
Demerits of mulching
• Warm moist condition favors spread of diseases/pests. In nursery such condition incites damping-off disease.
• Use of polythene mulch creates anaerobic condition may lead to root die back. Under such condition, plants experience oxygen starvation and its severity may prove lethal.
• Mulches of crop waste may carry seeds of pernicious weeds which may spread along with mulch.
• Mulch in arid region during fall monsoon, restrict seed germination, incite damping-off and counter successful crop production.
• Low growing plants are suppressed by mulches.
• In sub-tropics, dry mulches invite fire hazard.
There are types of mulching as –
Living mulch is usually a plant species that grows densely and low to the ground, such as clover. Living mulches can be planted before or after a crop is established. It is important to kill, till in, or otherwise manage the living mulch so that it does not compete with the actual crop.
Such materials as straw, bark, and composted material can provide effective weed control. Producing the material on the farm is recommended since the cost of purchased mulches can be prohibitive, depending on the amount needed to suppress weed emergence.
Materials such as black polyethylene have been used for weed control in a range of crops in organic production systems.