ESP-SMT Smart Modular Control System
79
Applying the “Cycle and Soak” Principle
In most soil types, you would not want to run the zone’s
irrigation system for one hour in duration as this would
most likely cause significant water loss through runoff.
Based on the soil type and degree of slope information
entered into the controller for the zone, the ESP-SMT
controller will determine the maximum “cycle” time and
minimum “soak” time required to irrigate without runoff.
These prescribed cycle and soak times are based on
the Water Intake rate of the soil type as identified in the
following tables:
Soil Type or Class Basic Intake Rate
Soil Type or Class
Basic Intake Rate
(inches per hour)
Sand
0.60”
Loamy Sand
0.50”
Sandy Loam
0.40”
Loam
0.35”
Clay Loam
0.20”
Silty Clay
0.15”
Clay
0.10”
This process would continue on a daily basis as shown is
the table below:
Illustrative Scheduling Example
Day
ET/Day
Effective
Rain
Net Water
Req’t
Accumula-
ted Water
Req’t
Irrigation
Event
1
0.18”
0.00”
0.18”
0.18”
---
2
0.16”
0.00”
0.16”
0.34”
---
3
0.16”
0.16”
0.00”
0.34”
---
4
0.18”
0.00”
0.18”
0.52”
0.53”
5
0.14”
0.00”
0.14”
0.13”
---
6
0.13”
0.10”
0.03”
0.16”
---
7
0.15”
0.11”
0.04”
0.20”
---
8
0.14”
0.00”
0.14”
0.34”
---
9
0.11”
0.00”
0.11”
0.45”
---
10
0.16”
0.00”
0.16”
0.61”
0.60”
11
0.12”
0.00”
0.12”
0.13”
---
12
0.12”
0.00”
0.12”
0.25”
---
In this example the irrigation schedule for the zone would be:
Day 4 - 60 minutes (Cycle 1 = 30 minutes & Cycle 2 = 30 minutes)
Day 10 – 68 minutes (Cycle 1 = 30 minutes, Cycle 2 = 30 minutes,
Cycle 3 = 8 minutes).