Regulated Deficit Irrigation

Regulated deficit irrigation has many benefits for landscape contractors, avid gardeners and cities faced with green waste disposal problems. These benefits are so significant that the Irrigation Association (IA) has created an entire chapter to discuss implementation of Deficit Irrigation in a Landscape Irrigation Scheduling and Water Management document. See Chapter 6 starting on page 147 (large PDF file of 1.4Meg).

In landscape, Regulated Deficit Irrigation will

• reduce labor costs of pruning,
• reduce green waste disposal costs,
• create denser roots and
• create stronger stems.

If the landscape has been well designed, installed and managed, then these results can be achieved with negligible loss of plant health even at mild drought levels.

The biggest obstacle to practicing deficit irrigation has been the high labor costs of constantly adjusting "dumb" irrigation controllers to follow changes in weather. The requirement of constantly adjusting "dumb" irrigation controllers is acutely important when watering in the deficit region.

WeatherSet's Smart Timers™ eliminate the barrier to practicing deficit irrigation. You create a frugal watering program and then WeatherSet's weather-based irrigation controllers will automatically adjust that frugal program to follow changes in weather...rain or shine. This adaptive, self-adjusting watering is easily seen in the chart below. The blue graph is watered delivered while the red jagged line is the corresponding ET (evapotranspiration).

WeatherSet smart controllers provide an easy way to strengthen landscape for regulated deficit irrigation. Chapter 6 of the IA document says that the technique to train landscape is to "widen the normal interval between irrigations." WeatherSet makes this step very easy and eliminates the complex calculations of irrigation schedules which fills most the 190 pages in the IA document.

WeatherSet has labeled its irrigation programs in its Smart Timers™ as Flowers™, Lawn™, Shrub™ and LWU (Low Water Usage). These labels are metaphors for shallow, medium, deep and very deep rooted plants. Under any ET conditions, WeatherSet's smart weather based controllers will give fewer watering days to the deeper rooted plants.

Simply, move valves down the following watering scales in WeatherSet's controllers to "widen the normal interval between irrigations" as suggested by the IA is to .

1. Flowers™
2. Lawn™
3. Shrub™
4. LWU1
5. LWU2.

With each step down the watering scale, WeatherSet's ET controllers "widen the normal interval between irrigations." You must observe the plants at each step for stress (blue-blocker sunglasses are good for this). The plants will tell you which step is "generous" and "frugal" for each valve. Take notes and record where the "frugal" step is for each valve. With WeatherSet self-adjusting, smart ET controllers, you will learn how to create healthier, stronger landscapes with automatic water conservation and how little water your plants really need.

A landscape which has been weakened by years of over watering may need training for a year or two. Oscillating the valves between the "frugal" step and the "generous" step every 2-3 weeks for the first spring and summer may strengthen the plants enough so that in the fall, "frugal" steps become the norm. You may find the next year that the "generous" and "frugal" steps have shifted down. Most plants will be comfortable with the first 3 steps. California Natives and cedars will be happiest in the LWU programs.

With weather-sensitive watering like that shown below,
regulated deficit irrigation can safely and economically be implemented.