Plastic mulch
Encyclopedia
Plastic mulch is a product used, in a similar fashion to mulch
, to suppress weed
s and conserve water
in crop production
and landscaping
. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant and ozone depleter, in the soil. Crops grow through slits or holes in thin plastic sheeting. Plastic mulch is often used in conjunction with drip irrigation
. Some research has been done using different colors of mulch to affect crop growth. This method is predominant in large-scale vegetable growing, with millions of acres cultivated under plastic mulch worldwide each year. Disposal of plastic mulch is cited as an environmental problem; however, technologies exist to provide for the recycling of used/disposed plastic mulch into viable plastic resins for re-use in the plastics manufacturing industry.
was one of the first to recognize the benefits of using LDPE (low density polyethylene
) and HDPE (high density polyethylene
) film as mulch in vegetable production. His work in this area was done at the University of Kentucky. Dr. Emmert also wrote on other topics such as the use of plastic for greenhouses instead of glass and plastic in field high tunnels. Today, Dr. Emmert is considered the "father of plastic greenhouses". He was jokingly also called the "plastic surgeon" due to his use of plastic instead of glass for greenhouses and his use of clear and black plastic as mulch in vegetable production. Approximately 2500 square miles (6,475 km²) of agricultural land utilize polyethylene mulch and similar row covers for crop production in the world.
has many benefits such as:
. 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.
. This means less water will be needed for irrigation
. Plastic mulches also aid in evenly distributing moisture to the soil which reduces plant stress.
in conjunction with plastic mulch allows one to reduce leaching of fertilizers. Using drip irrigation eliminates the use of flood and furrow irrigation that applies large quantities of water to the soil which in turn tends to leach nitrogen and other nutrients to depths below the root zone. Drip irrigation applies lower amounts of water with fertilizers injected and thus these fertilizers are applied to the root zone as needed. This also reduces the amount of fertilizer needed for adequate plant growth when compared to broadcast fertilization.
Due to these factors, the use of plastic mulch can lead to an improvement in the overall growth of the plant.
mulches exist, non-biodegradable plastics are more widespread. These non-biodegradable plastic mulches must be removed from the field and disposed of properly. Motes and McCraw of Oklahoma State University state that approximately 8 hours of labor is required to remove 1 acres (4,046.9 m²) of plastic mulch. There is one company, Crain Associates, Inc. that specializes in the building of plants designed to recycle agricultural film and other hard to clean plastics.
Mulch
In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....
, to suppress weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...
s and conserve water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
in crop production
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
and landscaping
Landscape architecture
Landscape architecture is the design of outdoor and public spaces to achieve environmental, socio-behavioral, or aesthetic outcomes. It involves the systematic investigation of existing social, ecological, and geological conditions and processes in the landscape, and the design of interventions...
. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant and ozone depleter, in the soil. Crops grow through slits or holes in thin plastic sheeting. Plastic mulch is often used in conjunction with drip irrigation
Drip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation or localized irrigation , is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves,...
. Some research has been done using different colors of mulch to affect crop growth. This method is predominant in large-scale vegetable growing, with millions of acres cultivated under plastic mulch worldwide each year. Disposal of plastic mulch is cited as an environmental problem; however, technologies exist to provide for the recycling of used/disposed plastic mulch into viable plastic resins for re-use in the plastics manufacturing industry.
History
The idea of using polyethylene film as mulch in plant production saw its beginnings in the mid-1950s. Dr. Emery M. Emmert of the University of KentuckyUniversity of Kentucky
The University of Kentucky, also known as UK, is a public co-educational university and is one of the state's two land-grant universities, located in Lexington, Kentucky...
was one of the first to recognize the benefits of using LDPE (low density polyethylene
Low density polyethylene
Low-density polyethylene is a thermoplastic made from petroleum. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries using a high pressure process via free radical polymerization. Its manufacture employs the same method today. LDPE is commonly recycled and has...
) and HDPE (high density polyethylene
High density polyethylene
High-density polyethylene or polyethylene high-density is a polyethylene thermoplastic made from petroleum. It takes 1.75 kilograms of petroleum to make one kilogram of HDPE...
) film as mulch in vegetable production. His work in this area was done at the University of Kentucky. Dr. Emmert also wrote on other topics such as the use of plastic for greenhouses instead of glass and plastic in field high tunnels. Today, Dr. Emmert is considered the "father of plastic greenhouses". He was jokingly also called the "plastic surgeon" due to his use of plastic instead of glass for greenhouses and his use of clear and black plastic as mulch in vegetable production. Approximately 2500 square miles (6,475 km²) of agricultural land utilize polyethylene mulch and similar row covers for crop production in the world.
Benefits
The use of plastic mulches along with the use of drip irrigationDrip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation or localized irrigation , is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves,...
has many benefits such as:
Earlier planting dates
The use of plastic mulch alters soil temperature. Dark mulches and clear mulches applied to the soil intercept sunlight warming the soil allowing earlier planting as well as encouraging faster growth early in the growing seasonGrowing season
In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....
. 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.
Soil moisture retention
Plastic mulches reduce the amount of water lost from the soil due to evaporationEvaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
. This means less water will be needed for irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
. Plastic mulches also aid in evenly distributing moisture to the soil which reduces plant stress.
Weed management
Plastic mulches prevent sunlight from reaching the soil which can inhibit most annual and perennial weeds. Clear plastics do not prevent weed growth. Holes in the mulch for plants tend to be the only pathway for weeds to grow.Reduction in the leaching of fertilizer
The use of drip irrigationDrip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation or localized irrigation , is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves,...
in conjunction with plastic mulch allows one to reduce leaching of fertilizers. Using drip irrigation eliminates the use of flood and furrow irrigation that applies large quantities of water to the soil which in turn tends to leach nitrogen and other nutrients to depths below the root zone. Drip irrigation applies lower amounts of water with fertilizers injected and thus these fertilizers are applied to the root zone as needed. This also reduces the amount of fertilizer needed for adequate plant growth when compared to broadcast fertilization.
Improved crop quality
Plastic mulches keep ripening fruits off of the soil. This reduced contact with the soil decreases fruit rot as well as keeps the fruit and vegetables clean. This is beneficial for the production of strawberries, for example.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.Reduction in root damage
The use of plastic mulch creates a practically weed free area around the plant, removing the need for cultivation except between the rows of plastic. Root damage associated with 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.
Cost
The benefits from using plastic mulch come at a higher cost than planting in bare soil. These costs include equipment, the plastic film used as the mulch, transplanters designed for plastic beds, and additional labor during installation and removal of mulch films. Specialized Mulch Application equipment must be used to install plastic mulch beds into a field. These machines shape the soil and apply the plastic to the prepared soil. Transplanters designed for plastic mulch can be used to plant the desired crop. Hand transplanting is an option but this is rather inefficient. The removal of plastic mulch also contributes to a higher cost through additional labor and equipment needed. Specialized designed undercutting equipment can be used to remove the plastic from the field after harvest.Disposal
Although biodegradable plasticBiodegradable plastic
Biodegradable plastics are plastics that will decompose in natural aerobic and anaerobic environments. Biodegradation of plastics can be achieved by enabling microorganisms in the environment to metabolize the molecular structure of plastic films to produce an inert humus-like material that is...
mulches exist, non-biodegradable plastics are more widespread. These non-biodegradable plastic mulches must be removed from the field and disposed of properly. Motes and McCraw of Oklahoma State University state that approximately 8 hours of labor is required to remove 1 acres (4,046.9 m²) of plastic mulch. There is one company, Crain Associates, Inc. that specializes in the building of plants designed to recycle agricultural film and other hard to clean plastics.
Application
The use of plastic mulch requires a unique application process to insure proper placement of the plastic film. This application process begins with the preparing the field the same way one would for a flat seed bed. The bed must be free of large soil clods and organic residue. A machine called a plastic layer or a bed shaper is pulled over the field creating a row of plastic mulch covering a planting bed. These beds can be a flat bed which simply means the surface of the plastic mulch is level with the inter-row soil surface. Machines that form raised beds create a plastic surface higher than the inter-row soil surface. The basic concept of the plastic bed shaper is a shaping box which creates the bed that is then covered by plastic via a roller and two coulters that cover the edges of the plastic film to hold the plastic the soil’s surface. These plastic layers also place the drip irrigation line under the plastic while the machine lays the plastic. It is somewhat important that the plastic is rather tight. This becomes important in the planting process.Planting
Planting also requires specialized planting equipment. The most common planting equipment is a waterwheel type transplanter. The waterwheel transplanter utilizes a rotating drum or drums with spikes at set intervals. The drum or drums have a water supply that continuously fills the drum with water. The transplanter rolls the spiked drum over the bed of plastic. As the drum presses a spike into the plastic a hole is punched a water flows into the punched hole. A rider on the transplanter can then place a plant in the hole. These drums can have multiple rows and varied intervals to create the desired spacing for that particular crop.Further reading
- Marr, C.W. 1993. Plastic Mulches for Vegetables. Kansas State University. October: 1-3.
- McCraw, D. Motes, J.E. 2007. Use of Plastic Mulch and Row Covers in Vegetable Production. Oklahoma Cooperative Extension Fact Sheets. 1-5.