Greenhouse Management
Glossary
D
DAMPING-OFF – A fungal disease that attacks seedlings, causing them to shrivel at the base. Damping-off is brought on by one of several fungi, including Pythium and Rhizoctonia, which thrive in stagnant air and high humidity.
DECIDUOUS – A plant that loses its leaves seasonally, usually in the fall.
DEIONIZED WATER – Water from which all ions are removed by means of the ion-exchange process.
DENITRIFICATION – The process by which soil organisms convert dissolved nitrate to gaseous nitrogen under anaerobic (low-oxygen) conditions. This occurs when soils become saturated and results in losses of nitrous oxide (a potent greenhouse gas) and nitrogen gas (N2, an inert gas).
DETERMINATE – A plant growth habit in which stems stop growing at a certain height and produce a flower cluster at the tip. Determinate tomatoes, for example, are short, early fruiting, have concentrated fruit set, and may not require staking.
DIATOMACEOUS EARTH – The fossilized remains of diatoms (a type of tiny algae) used to kill insect pests, snails, and slugs.
DILUENT – Anything used to dilute a pesticide. Water, for example, is a diluent. Not to be confused with carrier.
DIURNAL TEMPERATURE CYCLE – The diurnal temperature variation is the variation between a high temperature and a low temperature that occurs during the same day.
DOLOMITIC LIME – A naturally occurring liming material composed chiefly of carbonates of magnesium and calcium.
DORMANT – Alive but in a state of suspended animation until all conditions are right for growth.
DRIFT – Pesticide movement away from the release site in the air.
DRIP IRRIGATION – This is the practice of applying water slowly through various types of pipes, tubes or specialized hoses.
DYNAMIC WATER PRESSURE – This is also called working or operating pressure and is the water pressure that is measured in an operating drip irrigation system. In a drip system, a pressure gauge can be used to gauge your system's dynamic water pressure.
