Water for Greenhouse Production
Water Resource Management for Greenhouse Crop Production
Water Monitoring and Delivery Control
Greenhouse Boom Irrigation
Uniform Fertigation - Boom irrigation can improve greenhouse operations by automatically delivering uniform fertigation distribution or even, through customization and sensors, deliver different portions to different bench areas or individual plants.
More sophisticated boom delivery systems can water or mist different individual plants at different amounts using boom sensors and controls.
Uniform Fertigation - Boom irrigation can improve greenhouse operations by automatically delivering uniform fertigation distribution or even, through customization and sensors, deliver different portions to different bench areas or individual plants.
More sophisticated boom delivery systems can water or mist different individual plants at different amounts using boom sensors and controls.
Measurement of Dryness and Moisture Probes
An experienced greenhouse grower tends to know when to water the plants. However, many modern, large greenhouses are fitted with electronic sensory feedback, information processing, computerized control systems, and robotics for automated water application. Boom irrigation sweeps over greenhouse benches and stopping to selectively irrigate different plants in various ways and with different amounts of water.
To detect irrigation need, a tensiometer measures the soil moisture tension, the force between soil particles and water. As well, data feeds from soil moisture probes, bouyoucos blocks and container weight measurement, analyzed by computer or humans to know if more water is needed. Other devices measure soil moisture conductivity, when the moisture reaches a certain level irrigation begins. Devices to monitor water needs can be managed with the assistance of computers and software.
The amount of water for irrigation depends on the crop, its development stage, and a host of other factors. Over-irrigation can lead to excess leaching of fertilizers, whereas too little irrigation will lead to poor fertilizer distribution. There is a tendency to apply about 10% more than the water holding capacity of the bench or container.
Methods of Application
Overhead Irrigation. Boom irrigation and fertigation systems are used in greenhouses where millions of plants are growing. More space in such greenhouses is purposed for growing plants and less for human traffic. Boom irrigation setups eliminate the necessity of wide aisles required for hand-watering operations. Boom irrigation deployments can supposedly result in a ~40 percent cost saving with fertilizer and water over less efficient hand operated systems. Solutions of fertilizer, growth retardants, plant growth regulators, insecticides, fungicides, etc. can be applied uniformly, much more efficiently, and with less worker exposure. In fact, fewer workers can irrigate larger areas. Boom irrigation may be especially suited for vegetatively propagated crops, vegetative propagation, bedding plants, plug trays, and certain potted plants.
Subirrigation. Where water in direct contact with plants can help spread plant diseases in the greenhouse, many growers deliver water below the soil surface. Water and fertilizer savings can be substantial and subirrigation systems are also known as zero runoff systems. There are various techniques. For example, capillary mat systems are basically moist fabric with potted plants on top. Ebb and flood irrigation systems are used on very level, watertight, greenhouse benches where the crop is flooded and drained as needed.
Water Conservation and Water Recycling
The motivation to conserve water can be: economics - the cost of water; environmental and ecological concerns of the farmer and consumer; and, legal - in some areas greenhouse farmers must adopt water conservation practices by law. Where high-levels of water recovery are desired, the greenhouse farmer can filter and sterilize the water, eg with UV or Ozone treatment, for a complete water loop.
First of all, the substrate mix composition and quality are important in water conservation in that it is well balanced in terms of drainage and water holding capacity. Most crops grow best in a well-drained media with sufficient porosity. The media should also retain some moisture. Substrate mixtures with greater water holding capacities will require less frequent watering.
Boom and other types of overhead irrigation can be wasteful in terms of evaporation. More conservative irrigation methods have been: subirrigation, trickle tubes, drip, and soaker hose. However, in some of the more modern greenhouse facilities, boom irrigation systems have sensors and such that water is applied at different rates to different individual plants.