Irrigation Decisions Simplified with Electronics and Soil Water Sensors

Cary, J.W. and Fisher, H.D. (1983) Irrigation Decisions Simplified with Electronics and Soil Water Sensors. Soil Science Society of America Journal. 47(6):1219-1223.

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Abstract

Two simple, inexpensive systems use electrical resistance measurements
to provide useful, immediate information to assist decisions
made on irrigation water application. in one system a microprocessor-based
circuit coupled to a programmable calculator provides
an on-site estimate of the time until the next irrigation will be required,
based on field data and an operator-supplied parameter. The
second system simply signals the arrival of the wetting front at any
location in the soil by giving a visual indication, such as raising a
mechanical flag. The microprocessor-based circuit measures and
stores the resistance of four gypsum blocks once a day. The program
in the portable calculator accesses this information and uses it to
extrapolate the soil drying rate to predict the number of days until
the next irrigation. By restricting the microprocessor circuit to data
acquisition only and putting all number-handling routines into the
calculator program, the cost and complexity of the microprocessor
circuit is minimized, whereas maximizing the programming flexibility.
This makes it feasible to install a number of these devices at
different locations, all serviced by the same portable calculator.
The water infiltration circuit intermittently scans eight sets of
stainless steel electrodes to locate the soil wetting front during irrigation.
When the resistance across the electrodes decreases, sig-
'sling the arrival of the front, the circuit trips a spring-loaded Bag.
This provides a visible sign that the wetting front has reached that
point in the soil. The equipment worked well. When irrigation was
required in six or fewer days, the microprocessor/calculator system
made correct predictions 85% of the time. An example of how easily
any irrigation scheduling method may be converted to the microprocessor/calculator
system is presented.

Item Type:	Article
NWISRL Publication Number:	0519
Subjects:	Soil > Soil water (soil moisture) Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:52
Last Modified:	13 Jan 2017 23:27
Item ID:	411
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/411