以“国家褐潮土土壤肥力与肥料效益长期监测基地”的大田肥料长期试验为平台，研究了长期施肥对夏玉米叶片中硝酸还原酶（NR）、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)和谷氨酸脱氢酶(GDH）活性的影响。结果表明，长期N、P、K化肥配合（NPK处理）以及N、P、K化肥与有机肥或秸秆配合施用（NPKM与NPKS处理），叶片氮代谢酶（NR、GS、GOGAT和GDH）在籽粒灌浆时期均具有较高的活性，有利于玉米籽粒产量的形成；长期N、P、K化肥非平衡施肥的处理（NP、N、NK、PK处理）以及不施肥的CK，叶片氮代谢酶活性变化差异较大，且活性高峰期和籽粒灌浆关键期时间不一致，植株整体生产能力较弱，玉米籽粒产量较低。不同的酶对籽粒产量的贡献不同，因而系统研究长期定位配比施肥处理下玉米叶片的氮代谢酶活性具有重要的意义。
In order to understand the effect of long fertilization to nitrogen metabolism, we studied the effects of long-term(13 years) fertilization on activities of key enzymes (NR,GS,GOGAT and GDH) related to nitrogen metabolism (ENM) of maize leaf. The experiment was conducted in the base of soil fertility and fertilizer effect monitoring in fluvo-aquic soil in Changping County, Beijing, China with 8 treatments as CK(no fertilizer), NPK(N, P, K fertilizers), NPKM(N, P, K fertilizers and manure), NPKS(N, P, K fertilizers and stalk mulching), N(only N fertilizer), PK (P, K fertilizers), NK(N, K fertilizers), NP(N, P fertilizers). The rates of fertilizer application were 150 kg N ha-1, 75 kg P2O5 ha-1 and 45 kg K2O ha-1 per cropping season, and the manure and maize stalk were applied with 22.5 t ha-1 and 2.25 t ha-1 per year. The key enzymes related to nitrogen metabolism were measured. Yield investigation showed that NPKM treatment had the highest grain yield, and N treatment had the lowest one. Balanced fertilization treatments such as NPK, NPKM and NPKS had higher activities of enzymes related to nitrogen metabolism (ENM) of maize leaves during the grain filling phase and higher yields than the treatments of imbalanced fertilization systems (N, NK, NP and PK treatments). Long-term imbalanced fertilization systems such as NP, N, NK, PK and CK did not well match the high activities of enzymes related to nitrogen metabolism (ENM) with high grain filling phase, resulting in lower active growth and lower yields. The high activity of only some single enzyme had little effect on maize yield and quality. That all the key enzymes related to nitrogen metabolism (ENM) of maize leaf had higher activities could be effective on maize yield and quality formation. Even if the Glutamine sybthetase (GS), Glutamate synthase (GOGAT) and Glutamate dehydrogenase (GDH) activities on average of N and CK treatments were higher than others, the grain yields of these treatments were lower markedly than others. Different enzymes have different roles in the formation of grain yield and quality, so the study on all enzymes related to the activities of nitrogen metabolism (ENM) will help to understand the nitrogen metabolism of maize and improve the efficiency of fertilizer utilization.
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