Nitrogen uptake and use of summer maize under different soil fertility levels

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.