Guide for Producing Nursery Crops
Third Edition


Absorption - a process in which one substance permeates another; a fluid (such as water) permeates or is dissolved by a liquid or solid through pores or membranes.


Acetic acid - a clear, colorless, pungent organic acid that may be found in container substrates that are stored in large piles with low air exchange. 


Acid - a substance that tends to give up protons (hydrogen ions) to some other substance or when dissolved in water.


Acidity - the property of being acidic; a substance is considered acidic if the pH is less than 7. 


Adsorption - the adhesion of gases, solutes, or liquids to the surfaces of solid bodies (such as substrates or soil) or liquids with which they are in contact.


Air space - the percentage of container volume occupied by air-filled large pores from which water drains following irrigation.


Alkalinity - concentration of bases often expressed as carbonate or bicarbonate equivalents. An alkaline substrate will have a pH greater than 7.


Anaerobic - living, active, or occurring in the absence of free oxygen.


Bicarbonate - salts of carbonic acid. These salts such as sodium, calcium, and magnesium (NaHCO3, CaCO3 and MgCO3), have an alkalizing effect.


Biological control - the use of living organisms to control crop pests.


BMP - the Best Management Practices include schedules of activities, prohibitions, maintenance procedures, and structural or other management practices found to be the most effective and practicable methods to prevent or reduce the discharge of pollutants to the air or waters of the United States. Best management practices also include operating procedures, and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.


Bulk density - the weight of dry substrate per unit volume of substrate (g/cc).


Cambium - tissue between xylem and phloem that is responsible for secondary growth in most vascular plants.


Carbonate - to impregnate with carbon dioxide or having high levels of carbon dioxide.


Cation Exchange Capacity (CEC) - total of exchangeable cations (positively charged ions) that a substrate can adsorb. Some cations include ammonium, potassium, calcium, and magnesium.


Collection structure (basin) - an enclosed body of water to collect irrigation runoff water or rainfall from storm events.


Constructed wetland - a shallow depressed area (with or without water) filled with selected vegetation (i.e. cattails) to serve as a biological filter for removing nutrients and chemicals.


Container area - area that a group of plants occupies during the production phase.  A typical, single area is 6-8 feet wide and 50-300 feet long.


Container capacity - the maximum volume of water that a substrate can retain following irrigation and drainage due to gravity and is a measure of the water reservoir of the container.


Controlled-release fertilizer - fertilizer in which nutrients are released over time. Release is controlled by physical or biological degradation, by the thickness of the coating (i.e. resin), or by the type of coating surrounding the mineral elements. 


Cyclic irrigation - irrigation practice where a plant’s daily water allotment is divided into a series of events with irrigation application and rest intervals throughout the day.


Deionization - a technique used to remove ions (charged particles) from irrigation water. Commercial systems are available that combine prefiltration, mixed-bed resins, activated carbon, and final filtration.


Denitrification - in the absence of oxygen, microorganisms use nitrate or other forms of oxidized nitrogen instead of oxygen during the respiration process.


Deposition infiltration - a term used to describe filtration of naturally deposited sediments or minerals.


Electrical conductivity (EC) - the measure of salt content of water based on the flow of electrical current. The higher the salt content, the greater the flow of electrical current. EC is measured in mmhos/cm or decisiemens/m.


Emitter - a device used to distribute water for irrigation that can discharge in droplets, small streams, or through mini-sprayers.


Evapotranspiration - the combination of water that is evaporated from container substrate or native soil and water that is transpired by plants as a part of their metabolic processes.


Half-life - the time required for a substance to degrade by one-half.


Hardness - a characteristic of water caused by the presence of various salts, e.g. calcium, magnesium, and iron. Hardness is often associated with the presence of bicarbonates and carbonates (alkalizing effect).


Hydrophobic - having a lack of affinity for water or may repel and not absorb water.


Hydrophyte - a plant that lives in water.


Leachate - the solution that drains from container substrate during and after irrigation and may contain nutrients and pesticides from the substrate solution.


Leaching fraction - the volume of leachate divided by the total volume of irrigation entering the container multiplied by 100. This fraction should be 10-15%.


Lime - a material containing carbonates, oxides, and/or hydroxides, and used to neutralize substrate acidity. A common form, dolomitic limestone, contains calcium and magnesium.


Microirrigation - an irrigation system that delivers small amounts of water through emitters (spray or drip) in which gallons of water per hour are applied rather than gallons of water per minute.


Mycelium - the vegetative part of a fungus, which consists of a mass of branching, threadlike hyphae.


Nematode - very small (microscopic) worms abundant in many native soils that can destroy plant roots.


Non-cyclic - a continuous cycle of irrigation where the entire daily amount is applied in one application.


Oxalic acid - a toxic colorless crystalline organic acid found in oxalis and other plants; used as a cleansing agent for bleaching and rust removal.


Pathogen - an agent that causes disease, especially a living microorganism such as a bacterium or fungus.


Perched water table - area of temporary saturation at the bottom of a container or area of temporary saturation in native soil saturated with water.


Percolation - the slow movement of water through a substrate or soil.


Permeability - the capacity of porous rock, sediment or soil to allow water movement through.


Pesticides - any form of chemical or substance used to control pests. Pesticides include fungicides, herbicides, and insecticides, etc.


pH - a logarithmic measurement, ranging from 0 to 14, of the acidity or alkalinity (concentration of hydrogen ions (H+)) of a solution which numerically equals 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. A change of one unit is a tenfold change in hydrogen ion concentration.


Pheromones - naturally occurring chemicals secreted by insects or synthetically produced substances that can influence the behavior or often functioning as an attractant of the opposite sex.


Post-emergence - herbicides that can kill actively growing broadleaf or grassy-type weeds.


Pot-in-pot - a nursery production system in which a container is recessed in field soil and used as a holder for another container that contains the substrate.


Pour-through - a technique used to monitor container nutrient status.


Pre-emergence - herbicides applied to bare soil or container substrate that inhibit weed seeds from germinating.


Reverse osmosis - process where water is forced under pressure through a semipermeable membrane to remove salts or impurities that cannot traverse the membrane.


Rhizosphere - the soil zone that surrounds and is influenced by the roots of plants.


Riparian buffer - Strips of grass, shrubs and/or trees along the banks of rivers and streams that filter polluted runoff and provide a transition zone between water and human land use.


Runoff - the portion of rainfall or irrigation on an area that is discharged from the area. Runoff which is lost without entering the soil is called surface runoff and that which enters the soil is called ground water runoff or seepage flow.


Sedimentation - the process of particles that were held in suspension settling out of water.


Sodium Adsorption Ratio (SAR) - the cation concentrations of calcium and magnesium relative to sodium. Sodium is often responsible for salinity problems when linked to chloride (Cl) or sulfate (SO4). The following formula is used to calculate the adsorption ratio:

The cation concentrations are expressed as milliequivalents per liter as determined by a water analysis.

Soluble salts - see electrical conductivity.


Solution fertilizer - soluble nutrient carriers dissolved in water.


Subirrigation - a method used to apply irrigation to the bottom of container grown ornamentals or to the root zone of field crops which allows water to move from the bottom through the substrate or soil by capillary movement.


Substrate - organic and inorganic materials, often bark, peat, and sand, used as media components in a container to support the plant and contain the root system.


Suction lysimeter - an extraction tool used to obtain substrate solution for measurement of EC, pH and nutrient concentration.


Topographical - graphic representation or map of the relative positions and elevations surface features for a place or region.


Total porosity - the total volume of pore space in a substrate and is expressed as a percentage of the total substrate volume.


Turbidity - the suspended particulate matter ranging in size from colloidal to coarse dispersions in water.


Volatilization - to evaporate or cause to evaporate.


Water holding capacity - the ability of container substrate to retain water after drainage.