Change of nitrogen use efficiency of maize affected by long-term manure fertilization in the typical black soil

【Objectives】 Based on a long-term experiment in black soil in Gongzhuling City, we analyzed the changes of maize yield and nitrogen fertilizer efficiency and the correlation between nitrogen use efficiency (NUE) and soil nutrient contents, aiming to provide scientific references for establishing manure fertilization mode and improving NUE. 【Methods】 Treatments of no fertilization (CK), N fertilization (N), P and K fertilization (PK) and NPK fertilization (NPK), combined with different manure rates (0, 30 and 60 t/hm2), were chosen to research the effect of long term fertilization on nitrogen agronomy efficiency, annual nitrogen use efficiency and accumulated nitrogen use efficiency of maize.【Results】 All levels of manure treatments and NPK significantly have increased maize yield. The treatments of NPK combined with manures (M30+NPK and M60+NPK) have reduced the variation of maize yield (CV) and improved the sustainable index of maize yield (SYI). The nitrogen agronomy efficiency, annual nitrogen use efficiency and accumulated nitrogen use efficiency show increase trends with long-time chemical fertilization, and the increases reach significant or extremely significant levels. The soil fertility is improved with the applications of manures, but the variation of nitrogen agronomy efficiency, annual nitrogen use efficiency and accumulated nitrogen use efficiency are not significant, and the variation trend is significantly decreased with the elongation of experiment time. The nitrogen use efficiency is negatively correlated with soil organic carbon, soil total nitrogen, soil total phosphorus, and soil available potassium. 【Conclusions】 In black soil with relatively high fertility, the nitrogen use efficiency of maize is stable, but shows significantly declining trend, which provide scientific references for the partial replacement of chemical fertilizer by manure.