Irrigation (II)

Types of Irrigation systems

There are many types of irrigation systems that differ greatly in their performance, efficiency, and cost.   Choosing the proper irrigation system for your garden will help you save water, while providing your plants with their water needs and promoting their drought tolerance.

Hand watering requires time and effort, but is very simple to use.  It needs no maintenance and its initial cost simply consists of the price of a handheld water container.  Hand watering is specially suited for newly planted ornamentals and for selected plants that show signs of stress during the dry season.  To use water more efficiently when hand watering, build a shallow basin just outside the plant’s drip line (the line beyond the outer edge of the plant’s foliage) and apply water slowly in the basin.  If runoff occurs before the full required amount of water is applied to a plant, move on to another plant and return to the previous plant after the water applied to it has soaked in.

Flood irrigation provides a continuous layer of water over a fairly level surface of soil, and can be applied by using a hose.  Flood irrigation is easy to implement, and is considered the oldest irrigation method since it is similar in principle to the way in which rain irrigates plants. It requires time and effort, but does not require maintenance or any significant initial costs.  However, it does not promote healthy plant growth, and the excessive amounts of water provided to plants lead to weed growth and pest problems.  Also, it might give plants more water than their needs and at a faster rate than their ability to absorb it.  This results in reducing the drought tolerance of plants.  In addition, much of the water provided might be lost through evaporation or runoff.

Spray irrigation systems range from a single sprinkler attached to a garden hose to a complex system of underground pipes and pop-up spray heads.  The latter is more expensive, but more convenient and efficient.  Keep in mind that spray irrigation does not encourage the growth of deep root systems because it only wets the top layer of soil.  Consequently, limit its use to lawns, which have shallow root systems.   Also, keep in mind that up to a third of the water applied through spraying might be lost before it reaches the plant due to wind distortion or evaporation.

Drip irrigation consists of a system of PVC or polyethylene lines that carry water from the water source to specific plants through emitters.   It is appropriate for irrigating all landscape areas, except for lawn, and does not require much time or effort, but requires constant maintenance and a relatively high initial cost.  Drip irrigation promotes healthy plant growth, controls weed growth, and reduces pest problems because of the precise water placement it provides.  Also, the slow rate of water output gives the plants adequate time to absorb the water.  Drip irrigation wets a deeper, larger soil area in comparison to other irrigation systems, and thus encourages larger, more drought tolerant root systems.

Another advantage of drip irrigation is that it uses 30% to 50% less water than spray systems.  This is because very little water is lost to runoff, evaporation, or wind distortion.  Consequently, it is most suitable for irrigation in arid areas, as well as ones characterized by high winds or strong slopes.  Drip irrigation also is flexible. The number and location of emitters on the irrigation pipes, as well as the rate of water output, can be adjusted whenever the need arises.   In addition, retrofitting an existing landscape with a drip irrigation system is very easy.  To save water when using a drip system, consider using a filter to prevent dirt and debris from clogging the emitters.  This filter should be placed in the main line before water reaches any of the emitters.  Place emitters immediately beyond the drip line of the plants to encourage them to expand their roots.

Properly designed and well-maintained systems save water and promote healthy plant growth.  Using a combination of irrigation systems often provides better results than depending on a single system.

 Flood Irrigation

Flood Irrigation

 Spray Irrigation

Spray Irrigation

 Drip Irrigation

Drip Irrigation