Effect of deficit irrigation and mulching on water use efficiency of pomegranate

Abstract:

Deficit irrigation—the controlled application of water below full crop evapotranspiration demand at specific growth stages—has emerged as a tool for balancing yield and water economy in fruit crops. This research evaluated the interaction of three irrigation levels (100%, 75%, and 50% of ETc) with two mulching regimes (with and without black plastic mulch) on Bhagwa pomegranate at the Karaj research orchard over the 2021-22 and 2022-23 seasons. Six treatment combinations were arranged in a split-plot design with four replications on vines aged six years at the start of the research. Full irrigation without mulch produced the highest absolute yield (18.4 t ha⁻¹) but the lowest water use efficiency (3.8 kg m⁻³). The 50% ETc treatment with mulch delivered 15.1 t ha⁻¹ at a WUE of 7.1 kg m⁻³, an 87% gain over full irrigation without mulch. Fruit aril TSS climbed from 14.2 to 16.8 °Brix under 50% ETc with mulch, while aril weight dropped only 5.3%. Water applied fell from 4,850 m³ ha⁻¹ under full irrigation to 2,130 m³ ha⁻¹ under 50% ETc with mulch. The research points to moderate deficit irrigation combined with plastic mulch as a practical water-saving strategy for pomegranate in semi-arid Iranian plateau environments.