The effect of different irrigation methods (sprinkler, surface, surface-drip, and subsurface-drip) using treated wastewater, on alfalfa yield quantity and quality, was studied under semi-arid conditions. Randomized complete block design considering irrigation methods on 5 × 5 m plots replicated four times. Applied irrigation water was based on the Penman–Monteith equation using the FAO Cropwat software and accounting for the efficiencies of used irrigation systems. Surface irrigation gave the highest alfalfa fresh yield without significant difference compared to subsurface-drip. Average fresh production was 123, 120, 109, and 91 tons/h for surface, subsurface-drip, surface-drip, and sprinkler irrigation, respectively. Alfalfa fresh weight from subsurface-drip irrigation was 32 and 10% higher compared to sprinkler and surface-drip irrigation. Alfalfa dry weight from subsurface-drip irrigation was 10, 21, and 47% higher compared to surface-drip, surface, and sprinkler irrigation, respectively. N percentage in alfalfa leaves was significantly lower by 12% under subsurface-drip irrigation as compared to the other irrigation methods. Escherichia coli (E. coli) and fecal coliform (FC) were not detected on alfalfa leaves using subsurface-drip irrigation. E. coli and FC counts were high on leaves using sprinkler and surface irrigation. Subsurface-drip irrigation may be adapted as an efficient irrigation method when using non-conventional water under semi-arid conditions.

  • Irrigation study: Examined methods using treated wastewater in semi-arid areas.

  • Subsurface-drip: Tops in dry yield, matches in fresh yield.

  • Health benefits: Subsurface-drip reduces E. coli and fecal coliform on alfalfa.

  • Smart water use: Advocates calculated use with FAO Cropwat insights.

  • Alternative water: Recommends subsurface-drip for treated wastewater in semi-arid regions.

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