is a product used, in a similar
fashion to mulch
, to suppress weeds
and conserve water
. Certain plastic mulches
also act as a barrier to keep methyl
, 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
The idea of using polyethylene film as mulch in plant production
saw its beginnings in the mid 1950’s. Dr. Emery M. Emmert of the University of
Kentucky was one of the first to recognize the benefits of
using LDPE (low density polyethylene) and
density polyethylene) film as mulch in vegetable
production. His work in this area was done at the
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, of agricultural land utilize
polyethylene mulch and similar row covers for crop production in
The use of plastic mulches along with the use of drip irrigation
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 season
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
. This means less water
will be needed for irrigation
mulches also aid in evenly distributing moisture to the soil which
reduces plant stress.
Plastic mulches prevent sunlight from reaching the soil which can
inhibit most annual and perennial
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 irrigation
conjunction with plastic mulch allows one to reduce leaching of
fertilizers. Using drip irrigation eliminates the use of flood and
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
There are a few disadvantages to using plastic mulches in crop
production as well.
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.
Although biodegradable plastic
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 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
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 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.
- Plastic mulch film recycling process Agricultural
plastics recycling website, accessed 07.03.08
- 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