Until genetic engineering makes this a brave new world, water is the most limiting factor in plant growth. It is not by accident that the largest production of biomass is in the rain forests. Humid atmospheres such as the Amazon basin, the Pacific Northwest and certain temperate forests encourage fast, lush growth of plants and giant trees. Desert conditions produce slow, sparse growth.
To increase growth and lessen dependence on unpredictable rainfall, irrigation was invented. In biblical times and in prehistoric America, early irrigation projects were primarily man-made catch basins to contain the rain. Food plants and trees were then grown in the basins. Later water was carried from the rivers to the fields, as from the Nile in ancient Egypt.
Today we have efficient irrigation systems of great sophistication. Although developed for farming, the improvements can be used by everyone. When irrigation is used in agriculture, crop needs are first calculated. Then a system is laid out that delivers the exact right amount of water at the right time, all controlled by computer. A soil meter tests the soil-water availability and indicates when the plants are dry. A rain gauge, which automatically overrides the irrigation computer when it rains a lot, saves water.
All irrigation systems need maintenance. The pipes have to be cleaned of dirt, debris and sometimes gelatinous fungus that clog the holes. Tears and ruptures have to be plugged or repaired. Emitters, that spray or drip water, are fragile, and often need to be adjusted or replaced. In cold climates, the pipes have to be blown free of water in the fall, for freezing would rupture the pipes.
In communities where the sewer rate is tied to the rate of water usage, it is important to haver a separate water meter for any irrigation system, or else one is charged for sewer usage even though the water goes into the ground. Without a separate meter, money is wasted.
Types of Irrigation Systems
Leaky hose is the simplest kind. It has many names, but all are based on the same principle. Old rubber is recycled into a permeable hose. Water leaks out all along the length. It is excellent for vegetables and flower gardens. The hose can be laid on the surface, covered with mulch or buried. It does not suffer much from freezing because it already has holes in it and most of the water self-drains. It can be used with a simple computer-timer attached to the hose. A filter helps if the water supply is not perfect. The main problems are that the amount of water cannot be controlled easily and sometimes dirt or fungus plugs the line.
Spray sprinklers are the conventional system commonly used. Pipe is laid underground, with emitters that pop up when water is required. They spray the water into the air, where much of it evaporates, which is wasteful in most places. The exception is in very hot-arid climates, where the evaporation cools the air and humidifies it. These conventional sprinklers are always controlled by a complex computer, which is usually set incorrectly.
These systems are difficult to install and are best done by a professional irrigation company. They almost always need servicing each spring to keep the pipes clean, repair holes, level any part that gets out of line and fix sprinkler heads. In cold climates, these have to be drained and all of the water blown out with compressed air in the fall to prevent freezing.
Drip systems, or trickle irrigation, are the most sophisticated, efficient and cost-effective. Professional companies don’t like to lay them because they don’t make the same profit as with conventional sprinkler systems. Drip systems supply water slowly and directly to the roots through plastic tubing with small holes (emitters) near each plant. They can be buried or laid on top of the soil and may be covered with mulch. Developed in the Israeli desert, they have been used for years in our western desert, California and Florida. No water is sprayed into the air. Nothing evaporates. Nothing is wasted.
In the old variety holes are punched in thin plastic tubing where water is needed. An emitter, which delivers a calibrated amount of water, is put into the hole. Some emitters deliver one gallon an hour; others, different amounts. Angle brackets make it possible to go around corners. An in-line filter and a pressure regulator are also needed. A computer-timer may be attached.
The problem with drip systems is that they are difficult to calibrate as to how much water should be given to each plant and punching each hole is time consuming.
A new Israeli tubing called Netafim has been developed, which takes out all the guess work. It has pre-punched holes, 18 inches apart, each with a pressure-regulated emitter already installed that delivers exactly 1/2 gallon of water per hour. It is very easy to lay. The only tool needed is a pair of garden shears or a knife to cut the tube where corner angles or T-angles need to be put in. It can be flushed by opening the ends and because each holes individually pressure regulated, it can be laid uphill. It is easily repaired by cutting out any tear and putting in a new section of tubing. To date, this is the most cost-effective way to get irrigation. Installation doesn’t take too long; it just requires a little forethought.
Using a Sprinkler Wisely
When one tires of forever dragging heavy hoses through mud and fragile flower beds, thoughts naturally turn to the joys of a sprinkler system. It sounds easy; just set a computer in the basement and science will take care of the plants.
A sprinkler is certainly a joy, but it’s not that simple. An incorrectly set sprinkler is a silent killer. Much damage is done by wrong settings on the timers, which are usually set by the irrigation companies themselves.
Yet sprinklers are a real benefit. When properly set, everything grows better and bigger and with much, much less work. Most sprinkler companies try very hard to do the best for their clients. They are just trained with the wrong information about how plants grow.
Understanding why this happens helps avoid the problem. Sprinkler systems were developed for hot, dry climates such as southern California and Israel, which have sandy soil and no frost. The main markets were agriculture and golf courses, which require frequent sprinklings for optimal growth. Their schedules have become the standard for all systems everywhere.
Consider golf course grass. It is heavily fertilized, grown on sand and treated with fungicides. The grass that develops is shallow rooted and chemical dependent. So more shallow watering is needed and more fertilizer is added. It becomes a Catch-22; if either is stopped, the grass is not tough enough to survive.
Irrigation suppliers have sent this watering schedule to northern homes where it makes no sense. For example, in New England it rains a lot. The main dry months are July and August, with occasional hot spells in June and September. Except for new grass seed, sprinklers should be turned off in September or plants won’t harden for the winter.
For New England, the proper watering schedule is to deliver deep watering once a week from mid-June to early September. It should be 1 inch of water per week. In case of severe drought, a manual override might deliver extra water in July or August.
How does one calibrate a sprinkler system to know when it has delivered 1 inch of water? Set out several glasses or cans at various places under the sprinkler area. Mark them in inches with magic marker. Then turn the water on half an hour. Measure how much water is in each glass or can and average them. That tells how many inches of water the system delivers in a half hour. Some old systems will flood if 1 inch of water is given at once. Such systems have to be set for 1/2 inch of water twice a week. Systems used in Florida, California, and the Southwest also need to be set to compensate for their hot climates.