Mulching is a method of covering the soil around the growing the crop.
This method prevents soil erosion, weed infestation and retains soil moisture by reducing evaporation.
Different materials are used as Mulch for covering the soil, like straw (crop waste), plastic, leaves, wood chips, sawdust, newspaper, cardboard, etc.
Mulching is done in a wide range of vegetable and orchid crops.
Especially for vegetable gardens like capsicum, cabbage, cauliflower, chili, okra, tomato, brinjal, papaya, potato, pomegranate, lemon, guava, banana, apricot, and guava show better results with mulching.
With the extensive use of this technology and the adoption of various methods, the farmer gets maximum yield in a minimum area.
So, mulching is one of the techniques that helps in maximum yield in a minimum area.
Types of mulches
Mulches are categorized into organic and inorganic mulches based on their chemical composition.
1. Organic Mulch
These mulches are farmer-friendly as they convert to manure after decomposition, improving soil fertility.
Organic mulches are leaves, sawdust, wood chips, pruned bark parts, coconut coir, gunny bags, jute bags, Kitchen waste, newspaper, cardboard, Peat moss, animal waste, grass clippings, dried leaves, Garden waste, farmyard manure, etc.
A fully decomposed compost is used to reduce phytotoxicity. The mulching materials must be free of weeds to avoid the growth of weeds.
a. Compost/ Manure/ Peat
It is a widely used organic mulch and helps to improve soil fertility. It has to be spread as a 2- 3-inch layer on the soil surface.
b. Grass clippings
This is the most available form of Mulch. Fresh grass pieces add nitrogen to the soil.
However, it is not suggested as it may develop roots and develop as weeds. So dry grass clippings are ideal to use as Mulch. Still, there could be chances of weed seeds being dropped from the clippings.
c. Dry leaves
Shredded leaves are readily available material and are suitable for mulching.
These dry leaves are light in weight and may be blown away even by a light wind.
Hence, one can use stone, bark, or any other heavy material to reduce this problem.
This is also lightweight and a material that lasts very long due to its high carbon-nitrogen ratio.
It must be partially rotted before the application. It is acidic and, thus, should be avoided in acidic soils.
Paddy and wheat straw and other crop residues, like groundnut shells, stubble, etc., are also used as Mulch for conserving soil moisture.
This straw is poor in nutrient supply, but after decomposition, it aids in improving soil fertility.
As a mulch, it must be spread in a 5-10 centimeters thick layer.
This is a cheap and most available form of Mulch.
Due to their lightweight, they may be blown by wind or water. So, these are difficult to use as Mulch.
Using 2-3 layers of newspaper as a mulch under any expensive mulch is an ideal way to use them.
2. Inorganic mulches
These mulches do not have any soil-improving properties as they do not get decomposed. Plastic Mulch is mainly used as an inorganic Mulch.
a. Plastic mulches
Polyethylene is widely used as a mulch, as it can absorb long-wave radiations and increase the temperature around plants at night.
Crops grow through slits or holes in thin plastic sheeting. This method is used mainly for growing vegetables on a large scale.
They show positive control of weeds, prevent dryness, reduce nutrient loss by leaching, etc.
They must be disposed of properly to reduce their effects on the environment.
The thickness of plastic depends on the crop duration.
- Annuals (short duration crops)- 20 to 25 Micron thickness
- Biennials (medium duration)- 40 to 50 Micron thickness
- Perennials (long duration crops) – 50- 100 Micron thickness
Plastic mulches are classified as
Black polyethylene mulch
They do not allow sunlight to pass through them, thus inhibiting the growth of weeds.
They help to warm soil on cold days and maintain soil moisture.
Clear polyethylene mulch
They allow sunlight to pass through them and are not successful in controlling weeds to a large extent.
However, using herbicide coating inside the plastic can control weeds.
These are most successful in the nursery and suitable for increasing soil temperature in hilly areas.
Gravel, Pebbles, and Crushed stones
These materials are used in dryland fruit crops.
3-4 cm of stone or rock layer helps weed control and facilitates rainwater infiltration into the soil.
But they reflect the solar radiation, leading to a hot soil environment during summers.
Benefits of mulching
Retains soil moisture
Due to mulching, the rate of evaporation is reduced. So, irrigation at infrequent intervals is not required.
This helps to retain soil moisture, preventing drying of the soil and conserving water.
Mulch does not allow sunlight to pass through it, thereby suppressing the growth of weeds.
Increase soil nutrition
Mulching can increase, decrease, or have no effect on soil nutrition, depending on the type of Mulch used.
Organic Mulch with higher nitrogen content often results in higher yields and improves soil quality.
Few other organic mulches like sawdust, straw, and bark can also aid soil fertility.
Control soil erosion
Mulch stands as a barrier between soil and wind / running water.
So they do not come in direct contact with soil, and the soil does not blow or wash away.
Regulates soil temperature
Mulching plays a vital role in regulating soil temperature. This regulation varies based on the type of Mulch used.
White or reflective plastic mulches reflect solar radiation. This keeps soil cooler and prevents evaporation.
Black plastic mulch helps to increase temperature. Crop residues moderate temperature by rising in winter and decreasing in summer.
Organic Mulch in the soil reduces rainwater run-off and increases the absorption by soaking the water into the soil.
So it reduces the need for irrigation.
Efficient use of waste
Weeds, pruned leaves, branches, etc., can be used as Mulch, thus reducing the waste.
Prevents leaching of fertilizers
Water runs off the Mulch and does not allow the leaching of fertilizers.
Prevent the spread of pests and diseases.
Mulch acts as a barrier between the soil and the pest, thus reducing the attack of soil-borne pests.
It reduces the splashing of water, which can carry disease-spreading spores.
Plastic mulches reflect light, making controlling aphids, whiteflies, and leaf miners easier. Mulches are effective against nematodes.
Mulches can increase beneficial microorganisms that act on soil pathogens. Thus, mulching helps to reduce pests and diseases.
Reduce pesticide use
Mulching reduces weeds and pathogens, which reduces the need for the use of herbicides and pesticides.
Disadvantages of mulching
- Not economical: Few mulching materials like plastic films are costly and are not affordable.
- Readily unavailable: Some mulching materials like compost and manure are unavailable.
- Create nitrogen deficiency: Sawdust or straw sometimes creates nitrogen deficiency.
- Keeps the soil moist: Organic mulches may keep the soil too wet. This restricts oxygen in the root zone, where the soils have a poor drainage system.
- May be harmful- Plastic mulches may be detrimental to the environment or humans.
Best time for mulching
The end of the rainy season is the ideal time for mulching.
Mulching can be done permanently or temporarily.
These mulches are laid for a long time before growing the crop.
To make permanent Mulch, a layer of well-rotted compost, decomposed biomass, and fresh biomass is put on the soil, and seeds or saplings are planted into this. New Mulch may be added twice a year.
Preparation of Permanent Mulch
- Plow the land and add compost.
- Over it, add 3-inch layers of semi-deposed biomass like straw, litter, leaves, etc.
- Do watering for each layer.
- Now, on the top of the decomposed biomass, add fresh, green biomass. Ex- Weeds (without seeds), pruned parts of plants, etc.
- Do watering for each layer.
- It is ready for sowing. For planting, take a stick and dig a hole.
This is made of shredded leaves, little straw, etc., and is used for a short duration.
Preparation of temporary Mulch
- Add mulching materials to the compost and mix them.
- Apply this mixture to the soil and plow the land. They may be used on fallow land or mulched after crops are planted.
- The Mulch will rot while the plants grow. Ex- Potato, Onion, Garlic
How to maintain a mulch
- Before applying the Mulch, clean the area and remove weeds, stones, waste, etc.
- Check the moisture content regularly and water when necessary.
- Add new biomass twice a year.
- While using the Mulch, cover it partially to allow the air to enter the soil.
How does Mulch work?
The Mulch spreading over the soil prevents direct sunlight penetration and minimizes evaporation. Thus, it reduces the need to irrigate the crop continuously.
Sunlight is crucial for the development of weeds. But mulching inhabits sunlight, thus barring the growth of weeds.
It prevents rain from directly gushing into the soil and reduces soil erosion.
The organic Mulch breaks down, releases nutrients to the soil, and becomes food for microbes, protecting the healthy soil microorganisms.
Mulching is an age-old practice that has been popularised these days. It not only helps in protecting the plant from intense heat and nutrient loss but also aids in improving the yield.
The mulching materials help to save water resources by retaining moisture in the soil.
They reduce the cost of farmers purchasing farm inputs by inhibiting weeds and preventing nutrient leaching from the soil.
Organic mulches are recommended over plastic mulches due to their nutrient-enriching properties and environment-friendly nature.