Yield, Water Productivity, and Economic Performance of Alfalfa as Affected by Lateral Spacing in Subsurface Drip Irrigation Systems

This study was conducted during 2018–2019 to determine the effects of different lateral spacings under subsurface drip irrigation on alfalfa dry hay yield, irrigation water productivity, water productivity, economic water productivity, and land economic productivity. The experiment was established in a randomized complete block design with three replications. The treatments consisted of lateral spacings of 70 cm (S1), 105 cm (S2), and 140 cm (S3). Irrigation scheduling was based on soil moisture depletion, and crop evapotranspiration was determined using the soil water balance approach. Crop evapotranspiration varied between 866 and 1123 mm in both years, whereas irrigation water applied to the treatments ranged from 618 to 882 mm. The effect of lateral spacing on dry hay yield was significant at the P < 0.05 level. Among the treatments, dry hay yields ranged from 25276.1 to 27455.8 kg ha⁻¹. Irrigation water productivity, water productivity, economic water productivity, and land economic productivity ranged from 2.87 to 4.33 kg m⁻³, 2.25 to 3.09 kg m⁻³, 0.04 to 0.30 US$ m⁻³, and 376.2 to 2071.7 US$ ha⁻¹, respectively. In addition, the economic analysis indicated that the most profitable lateral spacing among the treatments was 70 cm. The results suggest that the 70 cm lateral spacing provided the most favorable balance between yield, water productivity, and economic return under the semi-arid conditions of the Menemen Plain.