Mulching is a method to cover the soil while growing the crop. This is done to protect from soil erosion, weed infestation, retain soil moisture and reduce evaporation, etc.
Various materials are used as mulch to cover the soil like straw, plastic, leaves, wood chips, sawdust, newspaper, cardboard, etc.
Mulching is done in a wide range of vegetable and orchid crops. Crops like capsicum, cabbage, cauliflower, chili, okra, tomato, brinjal, potato, pomegranate, papaya, lemon, guava, banana, apricot, and guava show better results with mulching.
With the extensive spread of technology and the adoption of various methods, a farmer is becoming progressive and is getting maximum yield in a minimum area. Mulching is one of the techniques that help to get maximum yield in a minimum area.
Types of mulches
Mulches are categorized into organic and inorganic mulches based on their composition.
1. Organic mulch
These mulches are farmer-friendly as they become manure after decomposition and improve 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 the widely used organic mulch and helps to improve soil fertility. It has to be spread 2- 3-inch layer on the soil.
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
c. Dry leaves
Leaves are easily available material and are good for mulching. Dry leaves are light in weight and maybe blown away even by a light wind. Using stone, bark, or any other material helps to reduce this problem
It lasts very long due to its high carbon-nitrogen ratio. It must be partially rotted before the application. It is acidic, thus should be avoided in acidic soils
paddy and wheat straw and other crop residues like groundnut shells, stubble, etc. are used as mulch for conserving soil moisture. It is poor in nutrient supply, but after decomposition, it aids in improving soil fertility. It is spread in a thick layer of 5- 10 centimeter as a mulch
The cheap and most available form of Mulch. Due to its lightweight, they may blow 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 considered an ideal way to use them.
2. Inorganic mulches
These mulches do not have any soil improving properties (adding fertilizers). Plastic mulch is mostly used as inorganic mulches.
a. Plastic mulches-Polyethylene is widely used as a mulch, as it can absorb long wave radiations and can increase the temperature around plants at night time. Crops grow through slits or holes in thin plastic sheeting. This method is used mostly for growing vegetables on a large scale.
They show positive control on weeds, prevent dryness, reduction of nutrients loss by leaching, etc. They must be disposed of properly to reduce 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 and 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. Though by using herbicide coating inside the plastic, weeds can be controlled. These are most successful in the nursery and are suitable in hilly areas to increase soil temperature.
Gravel, Pebbles, and Crushed stones: These materials are used in dryland fruit crops. 3-4 cm of stone or rock layer helps in weed control and facilitates the infiltration of rainwater 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 from drying of the soil and conserving water.
Control weeds- 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 improve the quality of the soil. Few other organic mulches like sawdust, straw, and bark can also aid in 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 an important role in regulating soil temperature. This regulation varies base 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 increasing in winter and decreasing in summer.
Water conservation- 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, and branches, etc. can be used as mulch, thus reducing the waste.
Prevents leaching of fertilizers- water runs off the mulch and does not allow 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 which makes easier to control aphids, whiteflies, and leaf miner. Mulches are effective against nematodes. Beneficial microorganisms that act on soil pathogens can be increased by mulches. Thus mulching helps to reduce pests and diseases.
Reduce pesticide use- mulching reduces weeds, 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 not affordable by everyone.
- Readily not available-Some mulching materials like compost, manure are not always available.
- Create nitrogen deficiency- Sawdust or straw sometimes creates nitrogen deficiency.
- Keeps the soil moist-Sometimes organic mulches may keep the soil too moist. This restricts oxygen in the root zone, where the soils have a poor drainage system.
- May be harmful- Plastic mulches may be harmful 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 on a temporary basis.
The 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 in 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 layer semi decomposed 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 leaves, little straw, etc. and 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 penetration of sunlight 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 and releases nutrients to the soil and becomes food for microbes, protecting the healthy soil microorganisms.
Mulching is an age-old practice that has got popularised these days extensively. 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 for purchasing farm inputs by inhibiting weeds and preventing nutrient leaching from the soil.
Organic mulches are recommended over plastic mulches due to its nutrient enriching properties and environment- friendly nature.