Abstract: 【Objective】The objectives of this study were to investigate the effects of drip irrigation uniformity and soil properties on the spatial and temporal variability of water and nitrogen in the soil and to quantitatively evaluate the suitability of current design standard of drip irrigation uniformity.【Method】Field experiments were conducted on drip irrigated spring maize  (Zea mays L.) in north China plain. Three Christiansen uniformity coefficients (CU) of 0.66 (low), 0.81(medium), and 0.99 (high) and three levels of water application at 50%, 75%, and 100% of the irrigation requirement were used. Soil water and nitrogen content were periodically measured during the growing seasons of spring maize.【Result】The result indicated that the uniformity coefficient of soil water content was higher than 0.85 in 2009 and higher than 0.80 in 2010. The low uniformity treatment did not produce a uniformity coefficient of soil water content that was significantly different from the medium and the high uniformity treatments. For the low uniformity treatment, the uniformity of soil water content was considerably higher than its irrigation uniformity (0.66). The influence of the uniformity of initiate soil water content was more important than the uniformity of water application and irrigation amount. Drip irrigation uniformity imposed an insignificant influence on the uniformity coefficients of nitrate content.【Conclusion】The results suggested that drip irrigation uniformity was not the main factor influencing the spatial and temporal variability of soil water and nitrogen for spring maize in the semi-humid regions such as the north China plain. The current design standard of drip irrigation uniformity coefficient (CU≥0.80) could be fairly lowered to reduce the initial cost of drip irrigation systems.

Key words: drip irrigation, uniformity coefficient, application amount, spring maize, soil water content, nitrate nitrogen