Abstract: 【Objective】In contrast to surface drip irrigation, both hydraulic design and spatial variations of soil properties may affect the system performance of subsurface drip irrigation (SDI). Field experiments were conducted on a sandy loam soil to investigate the influence of hydraulic design of SDI system and spatial variations of soil properties on water and nitrogen distributions and summer maize growth. 【Method】In the experiments, dripline depths were varied from 0 to 30 cm and two injector types, a differential pressure tank and a Venturi device, were used. Spatial variations of soil properties, including soil particle size distribution, bulk density, soil water characteristic curve, soil water content, and nitrate and ammonium nitrogen contents were tested. Saturated hydraulic conductivity was determined by an artificial neural network model from particle size distribution and bulk density. On harvest of summer maize, total dry matter above ground, yield, and nitrogen uptake were measured. 【Result】The results indicated initial nitrate content had the largest variability with a coefficient of variation Cv ranging from 0.51 to 1.58, saturated hydraulic conductivity had a moderate Cv of 0.31-0.44, and soil bulk density had a smallest Cv of 0.06. Dripline depth had a significant effect on the vertical distribution of nitrate following a fertigation event. A greater nitrate content of nitrate generally occurred at the proximity of the dripline buried positions, while injector types had an insignificant influence on nitrate distribution. No significant effect on ammonium distribution of dripline depths and injector types was found. The variability of total dry matter above ground, nitrogen uptake, and yield caused by hydraulic design and soil properties variation was least with Cv considerably smaller than soil nitrogen contents but approximate water and fertilizer applied Cv. 【Conclusion】Our experiments demonstrated that the nonuniform distribution of water and nitrogen in the soil following a fertigation event was mainly caused by the spatial variation of soil properties, especially the initial distribution of soil water and nitrogen contents. It is suggested that the spatial variations of soil properties should be considered in the design of SDI systems.

Key words: Subsurface drip irrigation, Hydraulic design, Soil properties, Nitrogen, Spatial variation, Summer maize, Yield