An irrigation system is essential to growing plants in a greenhouse. Plants rely on water to live and grow and because a greenhouse will not allow natural rainfall in, artificial means for irrigation become necessary. A variety of irrigation methods exist, and each method has benefits and drawbacks. Choosing the best irrigation method depends largely on the size of the greenhouse and the types of plants growing inside. Often the most effective irrigation comes from a combination of methods.
Drip irrigation is one of the more efficient methods of watering, typically operating at a 90 percent efficiency rate. Runoff and evaporation are at a reduced rate when compared to other irrigation systems such as sprinklers. In drip irrigation, tubes that have emitters run alongside the plants receiving irrigation. The water leaves the tubing through the emitters by slowly dripping into the soil at the root zone. This method of irrigation minimizes leaf, fruit and stem contact with water resulting in reduced plant disease. It reduces weed growth by keeping the area between plants dry. Irrigation through the drip method can be set to run automatically or controlled manually.
In a misting irrigation system, a pipe with nozzles that spray a fine mist is located above a row of plants. The nozzles mist the plants throughout the day, keeping them moist. Some of the mist will evaporate which maintains humidity and temperature levels in the greenhouse. Misting may not provide the deep watering needed for large plants. This method can encourage fungal diseases since the plant's foliage remains moist throughout the day.
The soaker hose method is cheaper than the drip irrigation system but runs on a similar idea. Soaker hoses have small punctures through the length of the hose. The hoses run alongside the base of the plants and water seeps from the perforations to water the plants. The length of time the water runs can be set using a timer. This method of irrigation minimizes plant contact with water resulting in decreased plant disease. Soaker hoses minimize water loss due to runoff and evaporation. Soaker hoses work the most efficiently when kept at a maximum length of 100 feet and on level ground.
Overhead sprinklers involve the installation of pipes with nozzles above the plants. The nozzles spray water in various ranges so that all the plants in the greenhouse are watered. Overhead sprinklers are good for mass watering but are better for plants that tolerate wet foliage. Plants will be more susceptible to fungal disease because of the contact of its foliage with water. Sprinklers are not adjustable to meet the individual needs of the plants.
Hand watering is the most basic method of irrigation for a greenhouse. Watering cans or hoses with nozzles allow you to tailor watering to the needs of individual plants. This is also the most labor-intensive method for plant irrigation and may not be effective for large greenhouses.