A soil column study showed that fertilization in a depth of 20-40 cm sustained the activities of superoxide dismatase (SOD) and catalase (CAT) in root system at a high level, meanwhile the root system vigor, the soluble protein content in root system decreased slowly, and the content of malondiadehyde (MDA) in wheat root system decreased, which delayed its senescence. It is considered that the depth (20-40 cm) of fertilization could be used as an index for delaying senescence.