Technical information

www.digcorp.com 1.800.322.9146
Introducon
The LEIT-2ET system is a weather-based, wireless
irrigaon control system that adjusts user preset daily
or weekly irrigaon programming according to real me
weather informaon provided locally by DIG’s LEIT WWS
or LEIT WWSE wireless solar powered weather staons.
The LEIT-2ET system consists of a two-staon, ambient
light (solar) powered controller with a rain sensor
connecon, an ambient light (solar) powered weather
staon and a two-way, remote control handset. The LEIT-
2ET ambient light (solar) powered, wireless controller
is programmed to monitor, control and adjust irrigaon
schedules for each valve using the weather informaon
received from the LEIT WWS solar powered, wireless
weather staons along with programmed site informaon
received from the LEIT RC2ET remote control handset.
The LEIT-2ET controller receives and stores weather
data from a LEIT weather staon once every hour during
dayme hours from a distance of up to 350 . (100 m)
line of sight. The controller uses the weather staon data
and site informaon provided by the LEIT RC2ET handset
to calculate the hourly and daily local microclimate
evapotranspiraon (ET), and automacally adjusts the
irrigaon schedule.
Today, water use can be opmized through the use of our
weather based irrigaon control system developed for
landscape irrigaon. This can be achieved by monitoring
the soil, temperature, humidity, radiaon, rainfall, wind,
and environmental condions at the irrigaon site. Both
the plants’ water requirements and the amount of water
available to the plant roots can be measured or esmated
through a variety of technologies. These technologies
include the feel method, which is an esmate based on
the users knowledge of the irrigaon site, and the more
accurate method of ulizing tensiometers, or the use of
weather sensors designed to monitor real me condions
including water demands inuenced by the local
environment, the irrigaon method and the plant types.
Water Requirements
To simplify the relaonships between plants, water
requirements and the environment, the term
evapotranspiraon is oen used. Originally established
for agriculture, where irrigaon requirements are
well documented, evapotranspiraon measures the
loss of water for various crops planted by farmers.
Evapotranspiraon takes into consideraon the loss of
water from the plant surface, the evaporaon of water
from the soil and the water lost through transpiraon
during a specic me period. Historical values for many
crop types have been recorded and are made available
through agricultural extension services.
Evapotranspiraon (ET)
Several methods have been developed to esmate
crop ET. Most methods use weather data to provide an
esmate of reference, or potenal, evapotranspiraon
(ETo). Oen this esmate of reference is converted to
actual” ET using a factor known as a crop coecient
(Kc). In landscape irrigaon, reference evapotranspiraon
(ETo) is established for well-watered turf grass, however
most landscape species do not have values established.
The turf and landscape industry’s managers and users
are not equipped to measure the plants’ water loss. The
feel method is not praccal due to the large variety of
environmental and management condions. Due to this
inability to eecvely measure and record water loss for
landscape planng, formulas have been developed using
reference evapotranspiraon, plant factors, microclimate
factors and landscape coecients to esmate the water
used. DIG’s weather based irrigaon controller system
ulizes a version of these formulas as the baseline for
esmang water use.
Informaon from the environment, plant water
requirements and the tools to calculate how much water
is in the soil may help in reducing water use by increasing
irrigaon eciency. By viewing the soil as a reservoir for
the plants water, and calculang the daily water needs of
the plant using various crop and landscape coecients,
we can determine approximately how long plants can
survive on the water available in the soil. When the water
in the soil is close to depleon, a med irrigaon in the
proper amount can rell the soil prole, restarng the
cycle.
The Importance of Soil Texture in Seng ET
Before programming the LEIT RC2ET handset and using
the new ET features we recommend that the user read
about soil texture. Knowing the soil type is important
in seng the proper conguraon on the LEIT RC2ET.
Most users can determine the soil type by reviewing the
following:
Radiation
Temperature
Wind speed
Humidity
=
ET
o
ET
o
well watered
grass
grass
reference
crop
BASED ON
x =
ET
c
well watered crop
optimal agronomic conditions
K
c
factor
off