The contribution of wastewater irrigation with the improvement of irrigation practices to the productivity of silage maize is a priority issue to investigate considering the saving of scarce freshwater resources and the necessity to dispose wastewater. The aim of this study was to evaluate the effect of different irrigation levels (L100, L67 and L33) of recycled municipal wastewater (RW) compared to freshwater (FW) using subsurface drip (SSDI), surface drip (SDI) and furrow irrigation (FI) methods on yield and some physiological traits of silage maize in semi-arid conditions at a high altitude. When the total daily reference evapotranspiration value reached 50 +/- 5 mm, irrigation quantities corresponding to 100%, 67% and 33% of soil moisture deficit based on field capacity in fully irrigated plots with freshwater were applied in different irrigation levels. Crop actual evapotranspiration (ETa) values were found close in both water types. SSDI reduced ETa by 18.5% and 45.6% in L100 level, 15.2% and 38.9% in L67, and 11.6% and 32.6% in L33, respectively compared to SDI and FI. The highest fresh biomass yield was determined in the SSDI-RW-L100 combination as 77.55 t ha-1, and resulted in 5% and 12.9% higher values than in SDI and FI. Leaf relative chlorophyll and water contents, leaf area index and electrolyte leakage showed strong linear correlations with yield and evapotranspiration values. The highest water productivity was determined in the SSDI-RW-L100 combination as 21.48 kg m-3 and it was higher by 28.2% and 99.4% than those in SDI and FI, respectively. Improvement of productivity with increased irrigation quantities in SSDI delivered the high yield response factor of 1.70-1.77. Therefore, it is concluded that the SSDI method can be a successful practice to improve productivity by alleviating the need for water for silage maize especially under full irrigation with RW.
