Plants grown in greenhouses are entirely dependent on artificial irrigation to meet their growth needs and there are plenty of options to handle the task, from hand watering to completely automated systems, but not all of them are optimal. Hand watering may be appropriate in certain limited situations, but it can take an enormous amount of time and is susceptible to problems related to uneven watering - too little, too much, or simply inconsistent. The healthiest, most beautiful plants come from ideal growing conditions and your greenhouse irrigation system should never be treated as an afterthought.
Managing Costs
High quality water is increasingly expensive, and if your location is beyond the reach of a municipal utility, delivery and storage can require a whole separate infrastructure. Some ways to manage these complications include:
- Use a highly efficient watering system.
- Use slightly lower quality water (non-potable) for less demanding crops. This solution is not acceptable for organic farmers (and not recommended for general vegetable and fruit production), since non-potable water could contain chemical contaminants or could even harbor dangerous microorganisms.
- Collect any runoff for re-use, while being watchful of the risks associated with using lower quality water.
- Consider establishing a regular testing and pre-treatment regimen to handle changing parameters of your water, including pH, changes in the presence of pesticide and fertilizer residue, and organic or suspended solids that could foul your irrigation equipment. Even municipal drinking-water treatment facilities can increase the amount of fluoride or chlorine bleach up to 4 ppm — within EPA standards, but too high for most crops — without notifying the end user.
Water Delivery
The variety of irrigation techniques available for greenhouse production can be dizzying. To determine the best solution for your specific situation requires an understanding of your operations, your specific needs, your budget, and how the systems will work within your enterprise.
Operations
Take into consideration the size of your greenhouse, all the types of plants you’ll be growing, and how much time and attention you and your staff will have to invest directly into caring for your plants.
Systems
To make a well-considered choice for the best system in your situation, you’ll need to start out by understanding every option that’s available. Listening to one (or more) sales pitches won’t give you a complete understanding. Do your own research.
Self-watering trays and capillary mats
This is a simple, uncomplicated system that is ideal for smaller greenhouses or those who are starting with a lean budget. This is also a great solution for plants that don’t like overhead watering like orchids and snake plants. A water compartment is kept filled and keeps a constant supply of water available to the soil and plants. Capillary mats can be added which absorb the water and release it slowly, minimizing root problems and wet feet. Potted plants can be placed directly on the wet mat.
This type of watering system is affordable and easy to set up. It provides a consistent water supply, encourages the development of deep roots, and promotes a humid atmosphere. Water reservoirs typically only need weekly refills, a great labor saver.
Overhead Sprinklers
Overhead watering is reserved for those plants who don’t mind getting their leaves wet. Pipes are suspended above the plants and fitted with nozzles that have settings for various spray ranges. Sprinkler systems are quick to operate, but they do require regular checking, particularly if you’re using lower quality water and the nozzles could become fouled with sediment or suspended solids. On the positive side, overhead sprinklers are cheap and easy to set up. They’re easy to use for regular watering and work well with automated systems, but there’s no control of water distribution over different areas - it’s pretty much one size fits all. Overhead sprinklers also use more water than other systems since the water is not precisely delivered to the soil.
Misting/Spray Systems
These systems work well for large greenhouses and for propagating seedlings, which need a regular, gentle application of water. Because less water is released, misters can run for longer periods than sprinklers or can be set to automatically spray in frequent intervals. Misters also can both increase the humidity in the greenhouse and lower the ambient temperature. This type of system is ideal for tropical plants and seedlings. While typically more expensive than sprinklers or watering trays, misting systems are still moderately priced.
Drip Irrigation
Drip irrigation systems use less water overall than the previous options, it is easily scalable for both large and small greenhouses and it’s suitable for all kinds of plants. Drip irrigation distributes water at soil level using a house and multiple emitters that operate throughout the day so that plants do not dry out. Water distribution can be precisely controlled by adjusting the emitters and it’s suitable for programmable automated systems. Drip irrigation may be more expensive to set up than misting systems, but the savings in water usage and plant health may be worth it.
Soaker Hoses
Like drip irrigation, soaker hoses deliver water directly to the soil, allowing plants to draw the moisture from deeper in the soil. Soaker hoses are porous, so they don’t depend on emitters. This saves the trouble of spacing out your plants to match emitters, but you cannot control the amount of water delivered to different areas. Since water is distributed evenly the whole length of the hose, this is a good solution for raised beds but not for individual pots.
Soaker hoses are quite simple to install and very low maintenance. They’re inexpensive and conserve water well. Automation is simple with a faucet-mounted tool and clogging isn’t an issue.
