Mulching may be defined as the process of covering the soil surface around the plants to create congenial conditions for the crop growth.
This may include moisture and soil conservation, temperature moderation, salinity and weed control etc. It exerts a decisive effect on earliness, yield and quality of the crop.
Types of Mulching / Mulch Materials
The mulch and more materials that may be used for laying over the soil may be organic plant residues, insert material like pebble etc. or and synthetic materials like plastics. Every material has got its marits and demerits.
Advantages of Mulching
(1) Mulching as a source for Weed Control
As every plant requires a process of photosynthesis for generation of food, which requires sunlight, on using of plastic mulch film the weed plant which will be below the plastic mulch sheet, the sheet does not allow the sunrays to pass through it, as our film has a unique quality of reflecting back the sunlight, which will not allow the weed to grow.
(2) Mulching improves Moisture Conservation
Plastic film with its moisture barrier properties does not allow the soil moisture to escape Water that evaporates from the soil surface under mulch film, condenses on the lower surface of the film and falls back as droplets.
Thus moisture is preserved for several days and increases the period between two irrigations.
Plastic mulches also aid in evenly distributing moisture to the soil which reduces plant stress.
Savings in water is one of the greatest advantage with plastic mulch and such savings are found to vary from 20% to as high as 75%.
The savings in water are more pronounced in dry areas.
(3) Reduction in the Cost of Fertilizer
Basically water has the property to go deep into the soil (also called as leaching property), where as the roots cant go too much deep into the soil, when fertilizer get dissolved in the water because of the leaching property there is a huge wastage of fertilizer, the use of plastic mulch along with drip irrigation allows the dissolved fertilizer not to go deep into the soil and allows timely and evenly distribution of nutrients to the plant, which helps the plant to grow faster and healthier.
Based on the above concept fertilizer use efficiency by the plant will be more than 95%, hence there will be an approximate saving of 50% in the cost of fertilizer.
(4) Quality Produce
Plastic mulches avoid the ripening fruits from direct soil contact. There by decreases fruit rot as well as keeps the fruit and vegetables clean.
This gives quality produce and better marketability.
(5) Mulching is useful for Reduction in Soil Compaction
The plastic mulch covering the soil decreases the crusting effect of rain and sunlight.
The reduction in weed quantity means a decreased need for mechanical cultivation. Weed control between beds of plastic can be done using directly applied herbicides and through mechanical means.
The soil underneath the plastic mulch stays loose and well aerated. This increases the amount of oxygen in the soil and aids in microbial activity. There by more active root zone will be developed.
(6) Reduction in Root Damage
The use of plastic mulch creates a practically weed free area around the plant, removing the need for inter cultivation except between the rows of plastic.
Root damage associated with inter cultivation is therefore eliminated. Due to these factors, the use of plastic mulch can lead to an improvement in the overall growth of the plant.
(7) Chimney Effect
Carbon dioxide (CO2) is slightly heavier than air during night. The CO2 tends to stay low near the plant before it finally defuses into the air.
The green leaves of all plants feed from CO2. They take out the carbon and release the oxygen.
Based on the above concept some of the CO2 will be preserved under the mulch film during the night, during the day time because of heat the CO2 will become lighter and goes upwards through the mulch whole at the stem of the plant, there by reaching the leaves above, which helps effective photosynthesis.
(8) Mulching helps to control Soil Erosion
Ideally soil erosion should be less than 4 to 5 tons/ha/year. The reduction of water runoff and erosion is one of the greatest advantages of having a plastic mulch by intercepting raindrops, hence the valuable fertile soil( humus layer) will be protected.
(9) Early Production
The use of plastic mulch alters soil temperature. Mulch applied to the soil intercept sunlight warming the soil allowing earlier planting as well as encouraging faster growth early in the growing season.
White mulch reflects heat from the sun effectively reducing soil temperature.
This reduction in temperature may help establish plants in mid-summer when cooler soil might be required.
(10) Salinity Management
(11) Mulching as a source for Pest Control
Plastic mulches like silver have the property to repellent the sucking pests like white flies, moreover plastic mulches will reduce the effect of soil born pathogen.
(12) Soil Micro-climate
Mulches create a micro environment which alters plant growth and development.
Plastic mulches affect plant microclimate by retaining soil moisture and changing root-zone temperatures and the quantity and quality of light reflected back to the plants there by altering the soil energy balance and restricting soil water evaporation, benefiting the plant growth and give better yield.
Precautions in Mulch Layering
• 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.
• The film should not be laid on the hottest time of the day, when the film will be in expanded condition.
Recommended Width for Mulching
This depends upon the inter row spacing. Normally a one to one and half meter width film can be easily adapted to different conditions.
Mulch Laying Techniques
Mulching materials should be laid on a non-windy condition
ii. The mulch material should be held tight without any crease and laid on the bed
iii. The borders (10 cm) should be anchored inside the soil in about 7-10 cm deep in small furrows at an angle of 45°.
Mulch Colours Effect
Black: This is the most popular color used in crop production, especially for weed control.
As a blackbody absorber, this plastic absorbs most incident solar radiation, including visible, infrared and ultra-violet light.
Clear: It has been used in solarizing or disinfecting the soil in order to reduce soil borne diseases and some weeds.
In such cases the soil must remain covered for several weeks during the hot part of the summer s as to achieve sufficiently high temperatures for solarization.
White: In this case, light is reflected back into the atmosphere or the plant canopy, resulting in slightly cooler soil temperatures.
White plastic mulches can be used to establish crops in the summer, when a reduced soil temperature might be beneficial.
Coextruded white on black plastic mulch helps cool the soil by way of white colour while controlling weeds by way of black colour.
Silver/aluminium: Reflective silver or aluminium mulches also give cooler soil temperatures.
They tend to repel aphids, which could serve as vectors for various viral diseases.
Red: Red plastic mulch has been reported to increase tomato yields and quality by various scientists, while others have reported a reduced severity of early blight in tomatoes.
It also has been shown to increase yields of strawberry, honeydews, muskmelons and zucchini.
In addition, it has been shown to significantly increase soil temperatures. Not all red colors are the same, however, and results have not been consistent.
Other colors: Blue, orange, or yellow mulches reflect different radiation patterns into the canopy of a crop, thereby affecting photosynthesis and/or plant morphogenesis, and can increase early yields, as was the case with red mulch.
The colors of mulching can also affect the behavior of certain insects. Yellow and, to a lesser degree, orange surfaces attract the green peach aphid.
Mulches with an aluminum or silver surface color have been used to repel certain aphids and reduce incidence of aphid-borne viruses in summer squash plantings.
Such mulches might be used in a field to grow “catch crops” to pull insects away from other crops.
Blue-colored mulches have been shown to increase zucchini and honeydew yields.
More research needs to be conducted to determine the effects of these colors on plant growth, yields, earliness and pest resistance.
Wave length-selective mulches
These mulches selectively absorb Photosynthetically Active Radiation (PAR), while transmitting solar infrared radiation. Also called infrared-transmitting (IRT) mulches, they help control weeds and exhibit improved soil-warming characteristics, although generally not as well as clear plastic. Colors range from blue-green to brown.
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