Introduction to Mulching in Agriculture
The following information is about Types of Mulching and Its advanatges.
‘Mulch’ originally means something that is soft and is beginning to decay. Materials that can be used on the soil surface mainly to prevent loss of water by evaporation, to cut down weed growth, to reduce temperature fluctuations and to promote soil productivity are all designated as Mulch. Mulching is referred to as a mixture of wet straw, leaves and loose earth evenly spread on the ground to protect the newly planted trees, shrubs and their roots. Tropical areas, sometimes use crop residues as Mulch material such as sugar cane trash, banana leaves or elephant grass, etc. Areas under the wet tropics having uniform rainfall distribution use cover crops instead of Mulch materials. Mulch is of extreme use in the dry season, especially during cultivation of certain crops like the sugar cane and coffee. Straw and stalks from cereal crops and fodder crops can be treated as Mulch material and can be either left on the soil surface or can be incorporated partially into the soil surface. Mulching is considered to be one of the most beneficial practices a farmer can do to keep his farm healthy. Basically Mulching creates a micro-climate for the plant to grow and perform better in an area that has regulated moisture content, suitable temperature, humidity, carbon-dioxide and proper microbial activity within the soil.
Application areas of Mulching
Mulching is generally applied in the following area of lands:
- In rain-fed areas to conserve moisture.
- In areas that need irrigation, Mulching reduces the frequency of irrigation.
- In greenhouses to maintain the soil temperature.
- In areas with soil borne diseases, Mulching is needed for solarisation.
- In heavy rainfall areas to reduce the impact of rain and prevent soil erosion.
- In lands where high value crops are being cultivated.
Types of Mulching
Mulch material can be classified into two major categories: organic and inorganic. Mulches derived from plant sources like compost, grass clippings, etc. is termed organic and the ones derived from plastic or other equivalent resources are termed inorganic.
Organic Mulch materials
Grass from mowed lawns can be used as an inexpensive Mulch material. A thin layer of these grass clippings can be spread over emerging seedlings and later a thicker dry layer of grass is applied in the crop area. It is important to note that grass clippings treated with pesticides should not be used as Mulch. When grass decomposes it supplies nitrogen to the soil.
Straw and hay
This is the most commonly used Mulch material in agriculture fields because it has long life when compared to other materials and they make the soil extremely fertile upon decomposition. Straw and hay reflect light from the surface of the soil and keep it cool. Sometimes there could be risk of weed growth, but a thick layer of straw can prevent it. It is recommended that nitrogen fertilizer is applied to the soil before straw Mulching because straw is high in carbon content and steals the nitrogen from the soil.
The drop of foliage from deciduous trees is natural Mulch occurring in the nature. It is a great insulator and is useful during root crops like carrots and parsnips.
This Mulch is long lasting in nature and is considered to lower the pH of the soil, so generally it is used on the land with plants requiring acidic soil conditions.
Some limitations of organic Mulch are:
- Create adverse effect on low draining soil by increasing the oxygen level near the roots.
- Provide shelter to pests like snails, and mice.
- The plant foliage or straw may contain seeds which may turn into weeds.
Inorganic Mulch materials
Unavailability of organic Mulch at all times has resulted in the use of plastic materials as Mulch. These plastic films are available in different colours and sizes depending on one’s need. The types of inorganic Mulches are:
It stops the sunlight from penetrating into the soil, thereby stopping the photosynthesis activity below the black film. This helps in the control of weed growth, but may increase the soil temperature.
This film allows light to pass through and aids in weed growth, but applying herbicide on the inner surface of the film can check the weed growth. Mostly it is used while soil solarisation is being done in nurseries so as to obtain 100% seed germination and a disease free nursery. It is useful in hilly areas for increasing the temperature of soil during winter season.
Double coloured Mulch
These types of Mulches are wavelength selective and are designed to absorb certain wavelengths from the sun’s radiation. These changes in the light can be effective on plant growth and development. It is considered that these films help in controlling different plant properties like fruit size, color, root development, height, etc. the colored Mulches re-emit less heat therefore maintains lower leaf temperatures. Some varieties are:
- Yellow-black/brown – brown or black side touches the soil and the yellow side faces upwards. It attracts whitefly and acts as a trap, thereby prevents disease.
- White-black – it is expected to transfer more than 60% of the photoactive radiation into the plant resulting in enhanced growth, thicker and stronger leaves. This film cools the soil.
- Silver-black – it’s the most popular type of Mulch used in farming and is suitable for all crops. It reflects almost 25-30% light back into the plant or fruit.
- Red-black – it is a partially translucent material which allows radiation to pass through it and makes the soil warm. The film also reflects light and helps in increased yield, early fruiting, good flower development etc.
There are again two types of degradable Mulches such as the photo-degradable and bio-degradable Mulch. The photo-degradable Mulch as the name suggests getting disintegrated under the sun over a certain period of time. Similarly, bio-degradable Mulch gets disintegrated under natural environmental conditions after a certain duration of time.
Potential problems of improper Mulching
Improper Mulching can be a cause of concern if done improperly. Too much is harmful to the plants. The general recommendation of Mulching depth is around 2 to 4 inches. Moderate Mulch can be beneficial while over Mulching can be dangerous. It is known that organic Mulch needs to be replenished over time, but if decomposition is slower that reapplication then there could be a possibility of Mulch build-up in the farm area which is not advantageous for the plants. Deep Mulch should be used only to suppress the weed and cut down maintenance, but some potential problems associated with it are:
- Deep Mulching when the soil is wet creates excess moisture in the root zone, which can stress the plant and result in root rot.
- If Mulch is piled against the trunk or stem of a plant then it causes stress on the stem tissues and leads to the development of disease and pests on the tree trunk or may lead to stem girdling roots.
- Mulch containing fresh grass clippings causes nutrient deficiencies in the soil by altering the pH of the soil adversely. It can also build up toxic levels in the soil.
- If Mulch is piled high against the stems of young trees, then this may attract rodents. They chew the bark and girdle the trees.
- Fine Mulch when laid as thick blankets becomes matted and reduces the penetration of water and air.
- ‘Sour’ Mulch that is anaerobic in nature may have a pungent smell. The Mulch may contain alcohols and organic acids which can be toxic to the young plants.
Selection of Mulch material
The Mulch that is selected for the farm should have certain properties for delivering maximum benefits. Organic Mulch cannot be altered in its characteristics, but inorganic or artificial Mulch is expected to have certain attributes. Various ecological factors may need different Mulch material to function properly. The important aspects of Mulch material are:
Thickness – generally thickness of the material has little or no effect on Mulching except for solarisation technique. The thickness of the artificial Mulch film should be around 15-30 microns for vegetable crops, 100-150 microns for orchids and 25 microns for small duration crops.
Width – the film should be selected such that it matches the inter row spacing. The average width of the film is around 1 or 1½ m under general growing conditions.
Perforation – unperforated Mulch film should be selected for efficient water and fertilizer distribution. To prevent water stagnation around the plants, perforated film is needed, but this may facilitate weed growth.
Color – the color of the Mulch can affect soil temperature, air temperature around the plants, the salinity of the soil, weed growth and incidence of insects.
Testing the Mulch film before using it on the farm is highly important because if the film transmits light, then it is no good for the plants. The material should be durable, air proof and thermal proof. It should always be remembered that the Mulch material should be purchased from a reliable source.
Type of Mulch according to the need:
- Rainy season – perforated
- Orchards – thick Mulch
- Solarisation – thin, transparent
- Weed control with solarisation – transparent
- A cropped area weed control, sandy soil, saline water use, etc. – black film
- Summer crop – white film
- Insect control – silver film
- Seed germination – thinner film
Techniques of Mulching
There are some precautions that should be taken before installing the Mulch on the fields such as:
- The area of the Mulch should be equal to the canopy of the plant.
- The Mulch sheet of required size should be cut from the main roll.
- Before the application of the Mulch, the area should be cleaned properly and stones, pebbles and weeds should be removed.
- The land should be tilled and watered before application of Mulch.
- To anchor the Mulch material properly in the area, making trenches around the area is helpful.
- The material is spread around the tree or plant and the ends should be buried into the ground at least 7-10 cm deep or into furrows at an angle of 45˚.
- Holes at the corners of the sheet can facilitate water movement.
- The opening of the Mulch material should be parallel to the wind direction.
- The sides of the Mulch material should be covered with 4-6 inches of soil to make the Mulch immovable.
- Mulch has to be laid during non-windy conditions.
- It should be laid evenly on the soil bed without any creases, but should not be very tight so as to facilitate expansion and shrink during various weather and environmental conditions.
Installing the Mulch on the fields for closed space crops
- Short duration crops need to be Mulched with thin films. Holes are made at the center of the film with sufficient diameter for the plants with the help of hot pipe or stainless steel glass.
- The soil should be tilled properly and required amount of FYM and other fertilizers are applied before Mulching.
- The rows are marked and the primary bed is prepared.
- Final soil bed width for single row crops should be 45-60 cm and for double row crops should be 75-90 cm.
- Check the drip laterals for their proper functioning.
- The Mulch film is spread evenly on the soil bed by stretching either manually or mechanically.
- Care should be taken such that the darker side of the Mulch film faces the soil and the corners of the Mulch are covered along the length of the soil.
Advantages of Mulching in farming
Mulching the farm land can have many advantages apart from weed control and water conservation. The major advantages of soil Mulching are outlined here:
- It helps with water conservation by preventing direct evaporation of water from the soil, thereby reducing the need for irrigation or water supply.
- Helps in weed control by cutting off the energy supply to the weeds.
- It helps to retain water in the soil and keep it moist for a longer period of time. It is also found to control the humidity level within the plant root zone.
- It helps in the development of white root of the plant above the surface of the soil.
- It forms as a substrate for the plant and its parts by preventing flowers, fruits and other plant parts to get in direct contact with the soil thereby improving their flower and fruit quality.
- It keeps the insect pests away from the plants because the Mulching film reflects light, thereby controlling the incidence of pests.
- It works as a heat and cold insulator by preventing freezing of soil during winter and drying of soil in the summer.
- Mulching protects the soil from erosion during heavy rainfall because soil is not directly exposed to rain.
- Mulching reduces the salinity level of the soil.
- It prevents the leaching of fertilizers from the soil.
- Sometimes it helps with seed germination, early maturity and higher production.
It is observed that after Mulching good production is obtained in vegetable crops like cabbage, cauliflower, capsicum, tomato, brinjal, chillies, okra, potatoes, etc. and some orchid crops like pomegranate, lemons, banana, papaya, guava, apricot, and grape etc. Care should be taken to apply Mulch that is suits the crop needs.