Authors: Vijay Kumar, Rakesh Kumar, K.R. Sharma Vikmas Shara
MULCH is a layer of material applied to the surface area of cultivated soil or it is any material used to cover the surface of cultivated soil to protect plant roots from heat, cold, or drought, to keep fruit clean, or to control weeds. Mulches are helpful to make more attractive, high yielding horticultural crops. The practice of mulching depends upon season, nature of crop, purpose of mulching and availability of mulching material. Mulches act as an insulating barrier between the soil and the air and thus play apparent role in moderating soil temperature. In mulches soil remains cooler in summer and comparatively warmer in the winter than the adjoining the unmulched soil.
The word mulch has probably derived from the German word “molsch” means soft to decay, which apparently referred to the gardener’s use of straw and leaves as a spread over the ground as mulch. The other advantage including enhancement of soil physical and chemical properties, augmentation the soil organic matter, the suppression of weeds and insect pests stress may favor the cultivation. With the increasing demand of horticultural produces and health consciousness among people it has became imperative for us to produce more as well as good quality produce to sustain in the international market. Mulching reduces the deterioration of soil by way of preventing the runoff and soil loss, minimizes the weed infestation and checks the water evaporation. Thus, it facilitates for more retention of soil moisture and helps in control of temperature fluctuations, improves physical, chemical and biological properties of soil, as it adds nutrients to the soil and ultimately enhances the growth and yield of crops. Further, reported that mulching boosts the yield by 50-60 per cent over no mulching under rainfed situations
TYPES OF MULCHES
There are many types of mulching materials, but they can be divided into two general categories:-
- Live mulch:- Live mulches are legumes (cover crop, inter crop, green crop)
- Dead mulch:-Dead mulch are organic, inorganic, synthetic and soil/dust mulch.
- Live mulch – These are usually as legume crop is the best choice for live mulch. It is practiced in fruit and plantation crops. Intercrop having good weed smothering ability can also be introduced in inter-rows of an economic crop. Examples of living much can be cover crop, inter crop, green crop velvet bean, subabool, barnyard grass, white clover, Ryegrass, etc.
- Dead mulch may divided into four categories:
- Organic mulches - These are those derived from plant and animal resources. Organic mulch properly utilized can perform all the benefits of any mulch with the possible exemption of early season soil warming. However, natural mulch materials are often not available in sufficient quantities for commercial operations or must be applied to the place of use. Natural materials are not easily spread on growing crops and require considerable hand labour. Organic mulches has three pronged function like-
- Conservation of soil moisture.
- Capable to weed smothering.
- Possible to nutrient enhancement.
(i) Residue mulch-This type of mulch attack of termite and on decomposition releases allelochemicals which may be phytotoxic to crops. That is why it is better to remove mulch material from the field after 35-40 days of sowing of crop when the purpose of weed control has been fulfilled. Crop residues are marvelous natural resource for recycling. These affect the physical, chemical, biological properties of soil and water quality. e.g., dry residues of plants/ crops, straw, sawdust, banana pseudostems).
(ii) Organic matter mulch-Organic substances are used as mulch; the thickness should be 3” Over mulching reduces oxygen levels in the soil and affect the root growth of a crop. This type of mulches provides good control of annual weeds but perennial weeds may be able to push through the mulch layer. Also, annual weeds may germinate and grow in the mulch layer. It includes compost, FYM, Sludge etc.
- Inorganic mulches - Generally polythene mulches which are different in colour may affect the temperature below and above the mulch through the absorption, transmission and reflection of solar energy. This affects the micro environment surroundings the plant. The degree of contact between the mulch and the soil also affects soil warming. The better contact the mulch has with the soil, the more effective the warming properties of the mulch. Now a day’s LDPE and LLDPE plastic films are commonly used for mulching. LLDPE black colour mulch film is most popular, owing to the twin properties of down gauging and better puncture availability.
- Weed control.
- Moisture conservation.
Advantage of mulching
Mulching is very favorable for number of reasons:-
1. It helps in conserving moisture by reducing the amount of soil water loss through evaporation and reduces the need of frequent watering.
2. It prevents/reduces the soil erosion and compaction from heavy rains and aid in water penetration rate.
3. It maintains a more even soil temperature. They act as insulators, keeping the soil warmer during cooler weather and cooler during warm months of the year.
4. It helps in preventing/minimizing the weed growth and lessening the amount of herbicide requirement.
5. It creates ideal environment for earthworms and other beneficial soil microorganisms.
6. It improves soil texture and organic matter helps in making the soil friable.
7. It helps in increasing root growth of the plant.
8. It significantly improves stand establishment of many horticulture, vegetable and floriculture crops.
9. Reduction in fertilizer losses, especially flood and furrow irrigation techniques tend to leach nitrogen and other water soluble nutrients below the root zone. Since plastic mulch techniques generally include drip irrigation, nutrient loss is kept to a minimum. Nutrients can be injected into the drip system and accurately delivered to the root zone as needed.
10. It is cheaper and safer technique and involves no phytotoxicity or herbicide residue.
11. Farmers can easily adopt mulching and get benefits.
Disadvantages of mulching
1. Limited availability of mulch material like husk, hay, saw dust etc.
2. Residue mulch is available at certain period only.
3. Difficulties in the removal and disposal of mulch particularly of synthetic mulch.
4. Specialized tools are required for special operations and add more expenditure in the cost.
5. Mulch if applied too thickly nay hinder seedling emergence by forming an impermeable barrier.
6. It is labour intensive process and need expertisation and experience.
7. It can introduce (particularly organic mulches) new pests, diseases into the main field when straw, peat, wood chips are used as mulching material alongwith infected weed seeds.
8. Plastic mulching is not sustainable or environment friendly.
9. Clear plastic mulch promotes weed growth that in turn deprive both soil moisture and nutrients from the crop. This mulch can offer greater soil warming capabilities over black plastic mulch.
10. Carbon rich materials create a risk of N- immobilisation. When organic matter is applied to the soil, the decomposing microbes multiply quickly. For growth, they need nutrients especially nitrogen if applied plant material does not contain sufficient nitrogen, the microorganism takes it from the soil and this nitrogen is fixed temporarily in the microbes and released after some time. During this time, the microbes compete with the plants for nutrient and the crop may suffer from malnutrition. This problem can also arise when straw or grain husks are applied.
When to apply mulch
Mulches are best applied from mid to late spring and autumn, when the soil is moist and warm. It is best to keep away from applying mulches in winter and early spring as the soil is too cold, and in summer, when it will be dry. They can be applied around new plantings or to established beds and specimen plants. Some commonly used mulched materials along with practical hints on their application are mentioned here as under:
| S.No | Mulch material | Thickness of mulching | Remarks |
| 1. | Compost | 3-4 inches | Improve water retention and physical property of soil. |
| 2. | Green Leaves | 3-4 inches | Chopped leaves are better |
| 3. | Dry Leaves | 6 inches | Chopped leaves are better |
| 4. | Grass clipping | 2-3 inches | Thick layer undergoes rotting. It becomes slimy and smelly |
| 5. | Bark | 2-4 inches | Good for use around trees and shrubs, smaller chips are convenient to use |
| 6. | Wood chips | 2-4 inches | Fresh wood chips are vulnerable to termite attack. mix it with lot of leaves and its use after compositing may be beneficial. |
| 7. | Newspaper | ¼ inches | Use text pages of newspaper which are imprinted with black ink only. Colour pages may harm the soil flora and fauna, if composted and use. Use 3-4 sheets together and cover it lightly with grass clipping and other mulch materials, soils may be used to another the newspaper. |
| 8. | Onion/ Garlic scale | 2-3 inches | Cover it with soil to another |
How to apply mulch
Mulch should be applied little bit away from the plants. Beds and borders can be mulched entirely, taking care not to smother low growing plants or to pile mulches up against the stems of woody plants. For smothering weeds and retain soil moisture, a 2-3 inch layer of mulch is necessary. Less than 2 inch of mulch will penetrate as much as necessary light and allow weed seeds to germinate. Before laying mulch, the following precaution should be taken-
- It should be laid on a non-windy condition.
- Mulch material should be held tight without any groove and laid on the bed.
- Borders (10cm) should be enchored inside the soil for about 7-10cm deep in small furrows at an angle of 45º.
5. Use of sawdust, wood or bark chips directly in the horticulture garden. Wood takes years to decompose and sawdust can create an imbalance of Nitrogen in the soil. Instead use these mulches in pathways around the garden where they can suppress weed growth.
6. Mulch is used under the canopy of the tree or whole field.
7. Before applying mulch, the field operations like tillage, removal of weeds, adding farm yard manure (FYM), irrigation and hoeing can be completed and land should be leveled to reduce contact angle between sheet and soil for more effectiveness.
8. In case of fruit plants plastic adjust the plant in center of the plastic mulch film from the cut portion of the film and cover whole area with plastic film. Care should be taken that the cut portion of film should not be in direction of wind. Otherwise, air may enter the film and there is a chance of damage to the sheet.
9. Transplanting is also done in the hole of plastic film.
10. If, mulching is done after the planting, care should be taken that plants are well established and they stand erect.
Table 1. Increase in yield of fruit crops through mulching
| S.No 1. | Crop | Yield (T/Ha.) | Increase in Yield (%) | |
| Unmulched | Mulched | |||
| 2. | Guava | 18.36 | 23.12 | 25.93 |
| 3. | Mango | 4.93 | 7.16 | 45.23 |
| 4. | Papaya | 73.24 | 120.29 | 64.24 |
| 5. | Ber | 7.02 | 8.92 | 27.06 |
| 6. | Pineapple | 10.25 | 11.75 | 14.63 |
| 7. | Banana | 53.99 | 73.32 | 33.95 |
| 8. | Litchi | 111.0 | 125.0 | 12.61 |
Precautions for mulch laying
1. Do not stretch the film very tightly. It should be loose enough to overcome the expansion and shrinkage conditions caused by temperature and the impacts of cultural operation.
2. The softness for black film should be more as the expansion; shrinkage phenomenon is maximum in this color.
3. The film should not be laid on the hottest time of the day, when the film will be in expanded condition.
About Author / Additional Info:
I am scientist working in research station at Raya