Provided by Dr. William Lamont, Jr. and Dr. Michael Orzolek
The Center for Plasticulture, Penn State University

Abrasion injury – injury observed on a plant that was caused by sand, hail, or wind resulting in moderate to severe tissue loss on stem, leave, flower or fruit.

Absorptivity - the property of a body that determines the fraction of incident radiation absorbed by the body.

Anthesis – the opening of flowers with appropriate plant parts available for pollination.

Available water in soils – the part of the water in the soil that can be taken up by plants at rates significant to their growth; it is useable; obtainable.

Antioxidant – formulation ingredient that prevents or slows down oxidation of plastic material exposed to air.

Backflow – a flowing back or return of water to its source (well or pond).

Blackbody – an ideal body or surface that completely absorbs all radiant energy of any wavelength falling upon it with no reflection of energy.

Blown film – a thermoplastic film that is produced by extruding a tube, applying a slight internal pressure to the tube to expand it while still molten and subsequent cooling to set the tube. The tube is then flattened through guides and wound up flat on rolls. The size of the blown film is determined by the flat width in inches.

Capillary porosity – The small pores or the bulk volume of small pores that hold water in soils against a tension usually greater than 60 centimeters of water. These pores are commonly filled with water when the soil is at field capacity.

Cation Exchange Capacity (CEC) - the total quantity of cations that a soil can adsorb by cation exchange, usually expressed as milliequivalents per 100 grams of soil. Measured values of cation exchange capacity depend somewhat on the method used for the determination.

Chemigation – application of various pesticides through an irrigation system.

Convection – transfer of energy in fluid motion.

Desiccation – a drying out of plant material or soil.

Double cropping – production of two different crops in a given area in the same year.

Easily available water – the portion of water in the soil that is readily absorbed by plant roots, usually capillary water between 0.3 and 15 bars of suction.

Elasticity – that property of a material by virtue of which it tends to recover its original size and shape after deformation. The tendency of a material to recover its natural size and shape when deforming load is removed.

Embossing – techniques used to create depressions of a specific pattern in plastic film and sheeting.

Erosion – the wearing away of the land surface by detachment and transport of soil and rock materials through the action of moving water, wind or other geological agents.

Evapotranspiration – the total loss of water by evaporation from the soil and by transpiration from plants for a given area.

Fertigation – application of soluble fertilizers through a drip irrigation system.

Field capacity – the percentage of water remaining in a soil two or three days after having been saturated and after drainage due to gravity has stopped.

Fumigation – treatment of soil with a volatile or gaseous fumigate for the control of crop pests (soil pathogens, soil insects and weeds).

Gas transmission – the movement of gas through film materials. The gas transmission property (permeability) of a film is measured in terms of volume of gas (at standard temperature and pressure) transmitted through a given area of film of a given thickness within a given time.

Growing degree days – method for calculating the amount of heat units based on daily temperatures that contribute to the physiological growth and development of plants. GDD = Tempmin + Tempmax divide by 2 – base 40°F or 50°F.

Hardpan – a hardened or cemented soil horizon or layer. The soil material may be sandy or clayey and may be cemented by iron oxide, silica, calcium carbonate or other substances.

High tunnel – structures that resemble plastic covered greenhouses but are considered non-permanent structures that have no automated heating or ventilation and are covered with a single layer of 6-mil plastic.

Integrated Crop Management (ICM) – a management system that recognizes and integrates the individual production practices required for success and profitability as dependent variables that can be controlled by the grower in some cases (i.e., drip irrigation to control plant growth or use of row covers to modify/prevent frost damage to crops).

Infrared light – light that is outside the visible spectrum at its red end (greater than 800 nm).

Injectors – devices which are able to inject (mix) concentrated fertilizers and chemicals with flowing water in an irrigation system. There are two types of injectors: venturi, (vacuum type) and hydraulic type (water drives a piston pump).

Langley – a unit of solar radiation equivalent to one gram calorie per square centimeter of irradiated
surface.

Leaching – the removal of materials (elements) in solution by the passage of water through soil.

Light transmission – the percent of total available light that passes through a material.

Low tunnel – a structure placed over crop rows in the field consisting of # 9 wire bent in a half circle with a peak height from 18” to 36” from the soil surface. Either plastic film with vent holes or slits or row cover material are placed over the hoops and secured on both sides with soil.

Mil – a unit of length equal to 0.001 inch, often used for reporting film thickness. To convert mil to millimeter, multiply by 0.0254.

Nanometer – a unit of length equal to 1/1000 of a micron. A micron equals 1/1000 of a millimeter.

Opacity – the measure of how opaque or see through a plastic film is. Certain pigments added to the polyethylene resin will make the plastic more opaque or less see-through.

Oxidation – removal of electrons from a molecule.

Percolation – the downward movement of water through soil.

Photosynthetic Active Radiation (PAR) - the measured flux between 400 and 700 nm that is utilized by plants during the carbohydrate-producing reactions associated with photosynthesis.

Phytochrome – pigment in plants in small concentrations that exists in two photoreversible forms, the red form and the far-red form.

Plasticulture – the use of plastics in agriculture for both plant and animal production including; plastic mulch, drip irrigation, row covers, low tunnels, high tunnels, greenhouses, silage bags, hay bales and in food packaging and nursery pots and containers for growing transplants.

Polyethylene – there are two major types with different chain structures: the stiffer, stronger, linear material sometimes called high –density (HDPE) and the low-pressure and more flexible, lower melting, branched polyethylene known as low-density (LDPE) or high –pressure polyethylene. More recently, linear low-density polyethylene (LLDPE) has become a major product.

Radiant flux - a measure of radiometric power. Radiometric flux, expressed in watts, includes light at all wavelengths of the spectrum; ultraviolet (200 to 400 nm), visible (400 to 700 nm), and infrared (700 to 30000 nm).

Reflectance – energy that has not been transmitted or absorbed.

Root Zone – the part of the soil that is penetrated or can be penetrated by plant roots.

Row covers – flexible, transparent coverings made from polyester or polypropylene that are installed over single or multiple rows of horticultural crops for the purpose of enhancing plant growth by warming the air around the plants in the field.

Runoff – that portion of precipitation on a drainage area that is discharged from the area in stream channels. Types include surface runoff, ground water runoff, or seepage.

Sandblasting – damaged caused to plants (young plants especially) by blowing sand. Moderate to extreme sandblasting can damage stems and kill plants.

Sand Media Filter – filters that are steel tanks filled with sharp or coarse sand. The sand bed itself creates the filtration as water passes through the sand bed and the silt and algae remain in the sand as the water passes through.

Soil Moisture Tension - the force by which moisture is held in the soil. It is a negative pressure and may be expressed in any convenient pressure unit. Tension does not include osmotic pressure values.

Solarization - a simple nonchemical technique that captures radiant heat energy from the sun. This energy causes physical, chemical, and biological changes in the soil. These changes lead to control or suppression of soilborne plant pathogens such as fungi, bacteria, nematodes, and pests along with weed seed and seedlings.

Solar Infrared energy – that portion of sunlight ranging from 700 to 2,500 nanometers wavelength, often called “Near Infrared”. “Far Infrared” or blackbody radiation ranges from 2,500 to 10,000 nanometers.

Solar Radiation – the entire energy spectrum (all wavelengths) created by the sun. The wavelengths reaching earth range from 300 to 3,000 nanometers.

Solenoid valve – water valves that open by electrical impulse and not manually.

Subirrigation – applying irrigation water below the ground surface either by raising the water table within or near the root zone, or by using a buried perforated or porous pipe system that discharges water directly into the root zone.

Tensiometer – sealed, water-filled c tip on the lower end and a vacuum gauge on the upper end to measure the amount of water in a soil.

Thermal radiation – electromagnetic radiation emitted from a heat or light source as a consequence of its temperature; it consists essentially of ultraviolet, visible, and infrared radiation.

Translocation – the movement of carbohydrates from photosynthesis in the plant from one part of a plant to another.

Transpiration – the evaporative loss of water (as water vapor) from plants, mostly through their stomata.

Triple cropping - production of three different crops in a given area in the same year.

Ultraviolet – zone of invisible radiation beyond the violet end of the spectrum of visible radiation. Since UV wavelengths are shorter than the visible wavelengths, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastic.

Ultraviolet light – that portion of sunlight ranging in wavelength from 200 to 400 nanometers. Wavelengths below 300 nanometers do not pass through the atmosphere in appreciable amounts.

Venturi injector – this type of injector operates by generating a differential pressure or vacuum across a venturi device. This draws the chemical into the drip irrigation system.

Windbreak – a narrow barrier of living trees or combination of trees and shrubs, usually from one to five rows wide, established within or around a field for the protection of land and crops. May also consist of narrow strips of annual crops such as corn, sorghum or wheat.