Horticulture Principles and Practices

PLASTICULTURE IN NORTH AMERICA
DR. MICHAEL D. ORZOLEK, PROF. VEGETABLE CROPS
Department of Horticulture, The Pennsylvania State University
University Park, PA 16802
INTRODUCTION
Plasticulture very simply is the use of plastics in agriculture. There are more uses of
plastics in horticultural crop production than any other form of agriculture. Use of
plastics in horticulture can be traced back to the 1960’s when Dr. Emery Emmert at the
University of Kentucky constructed the first double layer inflated polyethylene greenhouse
with 6 mil thick clear greenhouse grade plastic for producing vegetable transplants and
commercial crops. Emmert also realized the tremendous advantage of using plastic film
for growing vegetables outside and also placed thin plastic film (1.25 to 1.50 mil thick)
in the field for the production of field grown vegetables. Dr. Emmert observed that
placing black plastic film over soil resulted in higher soil temperatures, higher soil
moisture levels, reduced leaching of nutrients, and control of most annual and perennial
weeds compared to no plastic mulch. Chemical composition of plastics used in horticultural
crop production are general either polyethylene or polypropylene in nature with
additives to reduce the affect of ultra violet (UV) light on plastic degradation. From these
resins, many plastic products have been manufactured for modifying the environment
when growing horticultural crops in the field. The list of plastic materials used in
horticultural crop production include; transplant trays, plastic pots, plastic mulch film,
drip irrigation tape, low tunnels, row covers, floating row covers, high tunnels, and
greenhouses. All of these materials will modify the environment and optimize conditions
for optimum plant production.
614 Chapter 20 Growing Vegetables Outdoors
PLASTIC MULCH FILM
Because of the many advantages of using plastic film to grow horticultural crops, use of
plasticulture in the United States and the world in general has grown 10% each year for
the last 10 years. What has caused this growth of plasticulture use in the last 10 years?
Plastic mulch film when placed in the field will increase soil temperature, maintain
higher levels of soil moisture, maintain optimum soil tilth, reduce leaching of nutrients
in the soil, reduce leaching of chemicals, reduce/eliminate weed problems, and generally
reduce the time to maturity of the crops being grown on the plastic film. Plastic mulch
film is manufactured in rolls 2,400 to 4,000 linear feet long and either 3, 4, or 5 feet in
width. The bulk of plastic mulch used in the US is applied in the field with a raised bed,
mulch layer with drip irrigation tape applicator. The reason the plastic film is placed on
raised beds (6 to 12 inches in height) is to increase soil temperature faster than flat culture
and reduce the risks of root diseases since excess water in the root zone of most plants
will cause disease problems and/or deplete oxygen in the soil. Prior to placing the
non-degradable plastic mulch in the field, the soil must be tilled to leave small soil
particles that will produce a very firm bed for seeding or transplanting without any large
soil clods. Large soil clods under plastic mulch will make it difficult to firm soil around
transplants, eliminate air pockets next to the roots and firm soil around and above the soil
cube (Figure 1).
Initially all plastic mulch film was produced as a non-degradable material which
had to be retrieved from the field at the end of the growing season or when the horticultural