In this study, we sought to define system features that impact air delivery in subsurface drip irrigation systems. A 58% decrease in emitter cross-sectional area caused a 71% reduction in the water flow rate, but the 37% decrease in emitter air flow rate was statistically non-significant. For emitters with symmetric connectors, delivery of air from the emitters depended on the length of the connector relative to the air layer flowing at the top of the pipe. Emitters with asymmetric connectors yielded greater air flow rates compared to those with symmetric connectors, a result ascribed to a low-pressure region at the tip of asymmetric connectors. When symmetric connectors were used, an increase in pipe diameter was directly related to an increase in the uniformity of emitter air flow rate distribution expressed by the Christiansen uniformity coefficient (CUC), and inversely related to the efficiency of air bubble delivery and mean emitter air flow rate. In contrast, when asymmetric connectors were used, an increase in pipe diameter was associated with a decrease in CUC, and an increase in the efficiency of air bubble delivery and mean emitter air flow rate.
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