Chapter 12

Greenhouse Irrigation Systems

Types of Greenhouse Irrigation Systems

There are many ways of applying water to crops. They range from a handheld hose to sophisticated semiautomatic systems that can be programed to water an entire range of greenhouses. There are generally two types of greenhouse irrigation systems—the open system and the closed system. In an open system, water or fertilizer solution is applied to the upper surface of the substrate in a bench or pot, and any excess solution applied is allowed to drain from the bottom of the container out to the environment. By contrast, a closed system, also known as a sub-irrigation system, is one in which the nutrient solution provided at the base of the container rises by capillary action through holes in the bottom and is absorbed by the growing media. Solution that is not absorbed by the media drains back into a tank for recirculation. Open-irrigation systems can cover large areas, prevent fertilizer salt accumulation in medium, and be installed with relatively little expense. From a water and nutrient management perspective, however, these systems can be inefficient, may result in significant fertilizer leaching, runoff, irrigation inefficiency, and heavy use of water. Closed-irrigation systems with recycling of nutrients, is one of the promising strategies aiming to minimize pollution and increase water and fertilizer-use efficiency in irrigated greenhouse agriculture. Unfortunately, this also means that all fertilizer, substrate-applied pesticides, and possibly disease organisms remain in the closed system to be re-applied to the plants. Applied fertilizer can build up in the substrate, so monitoring fertility is important in any closed system. Plants tend to require approximately half the typical recommended rates for open, overhead irrigation systems. Hence, it is easy to unintentionally over fertilize plants. 

Open-irrigation Systems

Closed-irrigation Systems

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