This paper presents a reproducible, stepwise implementation and field validation of a photovoltaic (PV)-driven smart irrigation controller that tightly couples soil moisture feedback, low-cost sens-ing to improve energy and water efficiency in semi-arid agriculture. We document hardware selec-tion, laboratory calibration of FC-28 sensors against volumetric water content (VWC) reference samples (including regression statistics), controller design (bounded proportional law and safety interlocks), and an energy accounting inline power measurement. A field deployment in Biskra (March conditions) demonstrates soil moisture regulation within target bounds while reducing pump electrical consumption by approximately 18 % relative to a fixed speed benchmark. We dis-cuss limitations, sensor drift mitigation, and extensions, predictive scheduling using short term irradiance forecasts and distributed sensing for larger fields.

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