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Agwu, O. E.
Department of Electrical/Electronic Engineering, Michael Okpara University of Agriculture, Umudike, Nigeria.
Echebiri, E. U.
Nigerian Independent System Operators, Ministry of Power, TCN Substation, Katampe, Abuja FCT, Nigeria.
Mbachukwu, S.
Department of Electrical/Electronic Engineering, Michael Okpara University of Agriculture, Umudike, Nigeria.
ABSTRACT
Manual irrigation is inefficient and leads to wastage
of water as well as poor yields of crops. Using Arduino-based automatic systems
can account for the time issue associated with irrigation but mainly relies on
a universal soil moisture threshold which does not cater for individual crops'
water needs. Accordingly, this research designed a prototype of a low-cost,
Arduino-smart irrigation system wherein its central contribution is the new
methodological framework that it proposes for the calibration of a common soil
moisture sensor (YL-69) to local soil conditions in Michael Okpara University
of Agriculture, Umudike (MOUAU). The paper theoretically outlines calibration
actions under which the YL-69 sensor would be co-located with an exactly known
gypsum block in soil samples to generate a regression curve for converting
sensor analog readings (0-1023) into soil moisture tension (kPa) using a calibrated reference sensor. A resulting
regression equation, Analog Read Value = -5.2×(kPa) + 835 (R² = 0.94), served
as the transfer function. This equation was used to calculate precise,
programmable trigger points for different crops based on literature-defined
allowable depletion levels. For instance, setpoints for tomato, maize, and
lettuce were derived as 623, 523, and 715 analog units, corresponding to 40
kPa, 60 kPa, and 25 kPa, respectively. The proposed curve is finally shown as
the method to deduce accurate programmable trigger points for different crops.
The analysis theoretically demonstrates that a universal threshold approach is
agronomically flawed; the use of a universal threshold of 40 kPa would
under-water lettuce and over-water maize. This proposed framework provides
clear pathways toward transforming a generic automated system into a device
capable of precision agronomy, optimizing water use and lessening nutrient
leaching while ensuring maximum water yield potential is reached for specific
crops after empirical implementation.
Keywords: Precision Agriculture, Automated Irrigation, Soil Moisture Tension, Sensor Calibration, Theoretical Framework, Arduino Microcontroller
https://doi.org/10.33922/j.ujet_v11i2_10
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Published
Monday, July 14, 2025
Issue
Vol. 11 No. 2, December 2025
Article Section
GENERAL
The contents of the articles are the sole opinion of the author(s) and not of UJET.
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