My wife thinks I'm smart. She heard an audiobook I was listening to in the truck called "The Fundamentals of the Universe." What I didn't tell her was that I didn't understand most of it. I was hoping my intelligence would rise through osmosis. Fortunately, the universe keeps working without my understanding.
The same is true for gardens. We put the plants in the ground and nature takes care of the rest. But occasionally, we get in the way. This is especially true when it comes to irrigation.
Irrigation needs to be applied in the right amounts. More is not necessarily better. In a lot of cases, irrigation systems do more damage than if they were just turned off. Too much water reduces soil oxygen, which roots need to function. Roots also remain shallow when overwatered and fewer roots mean less heat tolerance. Excess water also means more disease, because wet foliage encourages leaf spot disease and saturated conditions can lead to root rot.
Rain sensors are inexpensive and help prevent overwatering when rain is plentiful, but they don't do enough to match irrigation to plant needs.
So how much should you water?
It depends on the irrigation system, weather conditions and plants.
All plants require supplemental water during the first year after planting. But once established, lawns only need it during drought and trees and shrubs may need none at all. In theory, good irrigation practices only replace the water that is lost to the atmosphere through evapotranspiration, which is mostly affected by temperature.
In the hottest part of summer, the soil loses about 0.2 inch of water every day. In summer, a typical irrigation system would run every other day to replace a total of 0.4 inch of water since we lost 0.2 inch each day.
Rotary sprinklers have a single stream that rotates back and forth and should run about 30 minutes every other day. Spray head sprinklers disperse a fan of water and should run about 10 minutes every other day. Rotary nozzles are newer technology that disperse thin, multiple streams of water and should run about 20 minutes every other day.
These are summer estimates, when water loss is at a peak. What about the fall and spring when temperatures are moderate? In the winter, an irrigation system running a summer schedule will be too much water. Most people turn their irrigation system off during the winter, but new irrigation technology helps determine exactly how many minutes your irrigation should run at all times of the year.
Smart controllers automatically adjust the irrigation schedule based on weather conditions, soil type and type of plants. In arid parts of the country, rebates are offered to customers using a smart controller because it can reduce water consumption by 15 percent to 30 percent. Not only are consumers saving money, the watering schedules more closely match plant needs.
There are several brands of smart controllers.
You can find a list at http://www.irrigation.org/swat/control_climate.
Nowadays, all the major brands have smart controllers: Rainbird, Toro, Hunter, Weathermatic, etc. You are more likely to find one at local irrigation suppliers than a garden center, such as WP Law, John Deere, Simmons, Ewing or Atlantic.
Some smart controllers circumvent the weather and use a sensor to measure soil moisture and alter the program, but most models come with a weather station that measures temperature and, in some cases, rain.
The controller uses this data to calculate water loss in the form of evapotranspiration and automatically adjusts the number of minutes the irrigation will run.
In some cases, a new controller isn't necessary. Brands such as Hunter have modules that can be added to the existing controller. Once a few inputs are made, the controller becomes smarter.
The beauty of these controllers is low maintenance. You don't have to go to the controller several times throughout the year to manually adjust the minutes to match the weather conditions. The controller does it automatically.
It's technology that makes you a smarter gardener.
Tony Bertauski is a horticulture instructor at Trident Technical College.
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