Mulching

T(caps)he National Committee on Plasticulture Application in Horticulture (NCPAH) has defined mulching as ‘A process of covering soil around the plant root area with a view to insulating the plant and its roots from the effect of extreme temperature fluctuations’. The farmers have been using natural organic products of plant origin like paddy straw, sugarcane leaves, dry leaves, coconut leaves etc to conserve the moisture in the soil since long term. Thus mulching can be defined as a process in which plant roots zone soil is covered with organic or inorganic materials to conserve soil moisture, check weeds and control soil temperature.
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Types of mulches

The mulches are of following types depending upon materials used as mulch:

Organic mulches

The organic mulches are loose organic materials such as dry leaves, paddy straw, paddy husk, dry grasses, sugar can leave, bark products, sawdust, coconut leaves and husk, pine needles, manures, compost and other crop residues. The organic mulches are good for both soil health and free from post use disposal problems but the availability of mulching materials is a limiting factor in the commercial use of organic mulch.

Inorganic mulches

The inorganic mulches are inorganic materials used as mulching that add no nutrients into the soil. The inorganic mulches are of two types:

Loose inorganic mulches

The peat, coarse sand, small stones and pieces of broken earthen pots are used as loose inorganic mulch.

Plastic sheets or Plastic mulches

When plastic sheets are used as mulch, the mulch is called plastic mulch. The plastic mulches are grouped into   two types:

Non-degradable plastic mulches

These are Non-degradable plastic films made up of LDPE (Low-density polyethylene) and LLDPE (Linear low-density polyethylene). The plastic films may be transparent or black in color. The transparent plastic mulch solarize the soil and reduces soil borne diseases whereas black mulch is more efficient in weeds control and moisture conservation. The thickness of plastic mulches varies from 20 to 100 microns depending upon the duration of crops. The annual crops need 20 to 25 microns, biennial 40-50 microns and perennials require 50-100 microns thick plastic mulches.

Degradable plastic mulches

These are two types: those that disintegrated under sunlight over a certain period are called photo degradable mulches and those that get disintegrated and mixed in the soil after mulching period under natural environmental conditions are termed biodegradable. The biodegradable mulches must break down into CO2, water,and environmentally benign harmless substances within one or two years, leaving no harmful residues. According to ASTM International (formerly known as the American Society for Testing and Materials), ‘Bio-gradable plastic is a degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae. The biodegradable plastic mulches are made from plant starch using conventional plastics processing technology.

Benefits of mulching

There are following advantages of mulching:

1. It conserves soil moisture by reducing the evaporation of water from the soil.
2. It suppresses the weeds and thereby checks the loss of water and nutrients from the soil.
3. It controls the fluctuation of soil temperature by insulting soil surface which prevents freezing injury to roots and provides a warmer condition for better root growth and physiological activities.
4. The organic mulch increases the organic matter content of the soil and improves the soil fertility and availability of plant nutrients.
5. The organic mulch provides a congenial soil environment for earthworms.
6. It protects soil from wind and water erosion.
7. The plastic mulch improves the fruits quality and reduces the fruits rotting by preventing the fruits from contacting soil.
8. It improves the seed germination and checks the loss of fertilizers by leaching.
9. It reduces the compaction of soil and particularly organic mulch enhances the soil aeration.
10. It conserves the depleting natural resources like water.

Demerits of mulching

• The harmful pests can get shelter beneath the mulch.
• The warm and moist environment beneath the mulch provides     favorable conditions for disease development.
• The pollution and post use disposal issue arise when non-degradable plastic is used in mulching.
• The crop residues and hay used in mulching may carry and           spread the seeds of pernicious weeds.
• The plastic mulches may cause anaerobic condition harmful for      roots.