Irrigation Schedule Description

The AgFleet® Irrigation Schedule is based on the "water budget" method. In its simplest form, the water budget adds precipitation and subtracts soil evaporation and crop transpiration to compute the daily available water in the soil. The combined soil evaporation and crop transpiration are commonly referred to as "evapotranspiration."

The budgeted available water fluctuates between a maximum (field capacity) value that is determined from the root zone, an intermediate value marking the beginning of stress, and a lower value marking the maximum deficit (or value). When the available water drops below the lower value or exceeds the maximum deficit, irrigation is scheduled to replenish the available water back to its maximum (field capacity) value. The value for the maximum deficit depends on the irrigation method and frequency. For each crop, there are three scheduling frequencies (low, mid, and high) to cover the range of water application methods and equipment.

Irrigation Scheduler water balance diagram
Click to enlarge

While the water budget method is at its core, the irrigation schedule is a bit more sophisticated in the way it determines the maximum available water and in the way it handles the weather inputs.

First, there is a crop development model to adjust the root zone throughout the season. The root zone determines the maximum available water in the soil. The crop development model is sensitive to the prevailing weather conditions and the time of year.

Second, an "effective" precipitation is calculated according to the amount of moisture entering the soil. While a certain amount of precipitation may reach the surface, only a fraction of that total replenishes the soil available water.

Third, the evapotranspiration is calculated based on the crop stage, soil moisture, and the prevailing weather conditions. The incorporation of weather "feedbacks" in the inputs makes for more realistic estimates of the water added and lost from the soil water budget.

In each crop schedule, the weather, soil, and irrigation variables are presented as absolute values. The decreasing or increasing available water, in inches, can be tracked relative to maximum, stress, and minimum values. The same fluctuation in the available water can be translated into daily and accumulated soil moisture deficits, and their equivalents as irrigation applications.

AgFleet® Irrigation Schedules are currently available for a number of grain and vegetable crops. Please contact your AgFleet® support group to get a complete listing of available crop irrigation schedules.

Learn more about Irrigation Scheduler's available products.

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Zedx, Inc.

369 Rolling Ridge Drive
Bellefonte, PA 16823

(814) 357-8490
(814) 357-8499 (fax)

Brian Antonucci

Customer Relations

(814) 357-8498
(814) 357-8499 (fax)