Irrigation Interval
&
Pre-Existing Moisture
Garden Tip
TB9001
Technical Bulletin Series
Support Info for the Garden Calculator Pro I

Irrigation "Interval" is the amount of time (in days or weeks) between one irrigation day and the next scheduled day.
Interval versus Times per day: If the irrigation schedule is set to water 2 times on Monday, Thursday and Saturday, the "Interval" is three days a week. Even if it is to water only one time on Monday, Thursday and Saturdey - the Interval is three days a week.
Multiple waterings in a single day simply allows more time for the moisture applied to soak into the soil, and has a much different impact on soil moisture than the number of days between watering has.
Days bewtween irrigations provides the time necessary for evaporation and transpiration (plant water consumption) to allow air into the soil, so the plant can respire (or breathe). If the soil is not given enough time to adequately dry during the irrigation interval, the root system will suffocate, causing the roots to be unable to absorb moisture.

Pre-Existing Moisture is the amount of soil moisture remaining following the irrigation interval, and before the next irrigation begins. The warmer the temperature the less soil moisture will remain, so Interval must be adjusted seasonally.

Adequate and appropriate irrigation interval is vital for plant health. The Garden Calculator Pro-I provides both the amount of water to apply during a watering day, AND the proper irrigation interval to allow for adequate drying before re-applying water again.
The Importance of Deep Water

The primary reasons that lawn or grass consume so much water is: (1) grass has shallow roots, so evaporation is high, and (2) the leaves and stems for grass are not succulent which would allow it to have a much longer interval between irrigations.
If an irrigation schedule provides shallow water with frequent irrigations, or short intervals; the plants being watered like this will exhibit that same "high water" consumption as would be found with grass.

Throughout the resommendations provided by the Garden Calculator Pro-I, the optimum volume of water is sufficient to permeate deeply into the soil. Results provided also include how deeply the recommended water will travel into the soil as an aid to understand the recommendations.
With shallow moisture
Plants look like this



When they should look like this

Thriving on good distribution
and adequate deep water
Variations from Optimum

Sometimes it is necessary to water a plant more often (shorter interval) than optimum (ex; on same zone as other type plants). So, to provide flexibility for the calculator user, a selection is available in order to choose "less than optimum" moisture depth.


In regions where annual rainfall is not enough to support normal plant life, or areas impacted by seasonal drought, proper irrigation is vitally needed in order to sustain plant life and plant health for local landscapes and gardens.

There is a genuine science for proper irrigation. Soil composition, the make-up or mix of the soil particles, differs greatly between various soils in each neighborhood. If the irrigation system does not properly match the composition of the soil, either water will be wasted or the plant will stress and decline.

Gone is the era of "guesswork-irrigation" for drought prone regions. Water is a precious resource, and plant health is vital towards each human beings' sense of happiness. We need beautiful and healthy landscapes and gardens, just as we need to conserve water.

Have you inherited an irrigation system
and schedule that needs an overhaul?
Way too often irrigation systems are simply copied from other popular local systems. Unfortunately, many irrigation systems in the desert southwest utilize spray type, or rapid drip emitters. These fast flow devices put out too much water to allow for adequately deep moisture permeation of the soil. The result is poor distribution, high evaporation, and wasted water. This also creates shallow root systems causing stressed plants.

By selecting a few plants at a time, and run a "Pro-I" analysis on them, you can gradually upgrade your system, provide deep water and reduce waste.

Because the science for dealing with this can be quite complex, the Garden Calculator Pro-I has been created and designed to make this method of accomplishing these objectives understandable and practical. This science is based on matching the irrigation being applied to a soil to its' composition.