For centuries horticulturists have attempted to modify the environment in which vegetable crops are grown. A wide variety of techniques, such as glass cloches, hotcaps, cold frames, hotbeds, and various types of glass greenhouses, have been used to extend the production season. The discovery and development of the polyethylene polymer in the late 1930s, and its subsequent introduction in the early 1950s in the form of plastic films, mulches, and drip-irrigation tubing and tape, revolutionized the commercial production of selected vegetable crops and gave rise to a system of production known as plasticulture. Simply defined, plasticulture is a system of growing vegetable crops where significant benefit is derived from using products derived from polyethylene (plastic) polymers. The later discovery of other polymers, such as polyvinyl chloride, polypropylene, and polyesters, and their use in microirrigation systems, pipes, fertigation equipment, filters, fittings and connectors, containers for growing transplants, picking and packaging containers, and row covers further extended the use of plastic components in this production system. The complete plasticulture system consists of plastic and non-plastic components: plastic mulches, drip-irrigation, fertigation/chemigation, soil sanitation (fumigation and solarization), windbreaks, stand establishment technology, season-extension technology, integrated pest management, cropping strategies, and postharvest handling and marketing. In the plasticulture system, plastic-covered greenhouses, plastic mulches, row covers, high tunnels, and windbreaks both permanent and annual are the major contributors to modifying the cropping environment of vegetable crops, thus enhancing crop growth, yield, and quality. In addition to modifying the soil and air temperatures, there are also the benefits of protection from the wind and in some instances rain, insects, diseases, and vertebrate pests.

Research was conducted to determine the optical properties of eight plastic mulches and evaluate their effects on soil, mulch, and air temperatures in the field. Optical properties of the mulches were measured in the laboratory in the shortwave (0.3 to 1.1 μm) and longwave (2.5 to 25 μm) wavebands using a spectroradiometer and Fourier transform infrared spectrophotometer, respectively. Additionally, each mulch was installed on a fine sandy loam soil near Manhattan, Kan. Air and soil temperatures were measured 5 cm above and 10 cm below the surface, respectively. Measurements of longwave radiation emitted and reflected from the surface were used to approximate the apparent temperature of the surface. Shortwave transmittance of the mulches ranged from 0.01 to 0.84, and shortwave reflectance ranged from 0.01 to 0.48, with the greatest reflectance from white and aluminized mulches. Infrared transmittance ranged from 0.87 for a black photodegradable mulch to 0.09 for aluminized material. Air temperatures at 5 cm were similar for all mulch treatments, but were typically 3 to 5C higher than the air at 1.5 m during the day. Midday soil temperatures were highest beneath mulches with high shortwave absorptance (black plastics) or those with high shortwave transmittance coupled with low longwave transmittance. Apparent surface temperatures approached 70 to 80C during midday, with the highest temperatures occurring on mulches with high shortwave absorptance. For some mulches, both, shortwave and longwave optical properties of the plastic governed the level of radiative heating. Our results suggest that conduction of heat between the plastic and the soil surface also affects the extent of soil heating in a mulched field.

High tunnels have been used for many years worldwide, but in the United States, the utilization of high tunnel technology for the production of horticultural crops is a relatively recent phenomenon. Single and multibay high tunnels are used throughout the world to extend the production season. One big advantage of high tunnels in the temperate and tropical regions of the world is the exclusion of rain, thus reducing the amount of disease pressure and crop loss while improving crop quality and shelf life. In temperate regions of the world, high tunnels are used to increase temperatures for crop production in spring, fall, and sometimes winter seasons. The use of high tunnels in their many forms continues to increase worldwide, and many different kinds of vegetables, small fruit, tree fruit, and flowers are being cultivated. One impediment in determining high tunnel usage worldwide is the failure of many authors and agricultural census takers to distinguish between high tunnels and plastic-covered greenhouses. In many instances, they are presented together under the heading “protected cultivation.”

High tunnels are becoming an increasingly important production tool for vegetable, small fruit, and cut flower growers in many parts of the United States. They provide a protected environment relative to the open field, allowing for earlier or later production of many crops, and they typically improve yield and quality as well as disease and pest management. Producers, ranging from small-scale market gardens to larger scale farms, are using high tunnels of various forms to produce for early markets, schedule production through extended seasons, grow specialty crops that require some environmental modification, and capture premium prices. The rapid ongoing adoption of high tunnels has resulted in numerous grower innovations and increased university research and extension programming to serve grower needs. An informal survey of extension specialists was conducted in 2007 to estimate numbers (area) of high tunnels and crops being grown in them by state, and to identify current research and extension efforts. Results of this survey provide an indication of the increasing importance of these structures for horticultural crop production across the country.

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At the Pennsylvania State University (Penn State) High Tunnel Research and Education Facility, a system of production of high-value horticultural crops in high tunnels has been developed that uses plastic mulch and drip irrigation. The Penn State system involves small-scale, plastic-application equipment that prepares and applies plastic mulch and drip-irrigation tape to individual raised beds. It differs from the production system developed by researchers at the University of New Hampshire in which drip-irrigation tape is manually applied to the soil surface and then the entire soil surface in the high tunnel is covered with a black plastic sheet. An overview of the production system used in the Penn State high tunnels is presented in this report.

Plasticulture, simply defined, is a system of growing crops wherein a significant benefit is derived from using products derived from plastic polymers. The discovery and development of the polythylene polymer in the late 1930s, and its subsequent introduction in the early 1950s in the form of plastic films, mulches, and drip-irrigation tubing and tape, revolutionized the commercial production of selected vegetable crops and gave rise to plasticulture. The later discovery of other polymers, such as polyvinyl chloride, polyproplene, and polyesters, and their use in pipes, fertigation equipment, filters, fittings and connectors, and row covers further extended the use of plastic components in this production system. The plasticulture system consists of plastic and nonplastic components: plastic mulches, drip irrigation, fertigation/chemigation, fumigation and solarization, windbreaks, stand establishment technology, season-extending technology, pest management, cropping strategies, and marketing.

Mulches usable in organic production were evaluated in high tunnels for their ability to suppress weeds. Mulch treatments were shredded newspaper, sheets of newspaper, straw, and a no-mulch control that was weeded once. Four cucumber (Cucumis sativus) cultivars were also evaluated. Yields were highest and fruit largest from ‘Sweet Marketmore’ and lowest from ‘Lemon’. Yields were unaffected by mulch treatments. Weed populations were highest in control plots and lowest in those with shredded newspaper. Cultivars did not affect weed populations. Sheets of newspaper degraded the most, followed by shredded newspaper and straw. Yields were not influenced by any mulch treatment, indicating weed populations remained below yield-depressing levels regardless of treatment.