Effects of nitrogen uptake and use for summer maize under different soil fertility levels was studied in a pot experiment using 15N labeling techniques.The results showed that the grain yield under high soil fertility level(H NPK)was higher than it was under low soil fertility level(L NPK)and medium soil fertility level(M NPK),2307% and 1240%,respectively.The percentage of grain nitrogen absorption in total nitrogen absorption under H NPK treatment was highest,823%.The ratio of nitrogen which was absorbed from the indigenous soil supply and from applied fertilizer was close to 1∶1.The applied fertilizer nitrogen ratios of each maize organ under L NPK and M NPK was significantly higher than its under H NPK.Nitrogen apparent recovery efficiency under L NPK was higher than its under M NPK and H NPK,about 2 percent,while 15N use efficiency under H NPK and L NPK were significantly higher than M NPK,678% and 765%,respectively.Priming rate under L NPK was higher than its under M NPK,but unsignificantly,both of them were significantly higher than its under H NPK,3730% and 2698%,respectively.