氮肥有效率的概念及意义——兼论对传统氮肥利用率的理解误区

THE CONCEPT AND MEANINGS OF NITROGEN FERTILIZER AVAILABILITY RATIO― DISCUSSING MISUNDERSTANDING OF TRADITIONAL NITROGEN USE EFFICIENCY

自氮肥发明和施用以来,人们一直想通过氮肥利用率来度量氮肥施用效果。传统氮肥利用率是指当季作物吸收肥料氮占施用肥料氮的百分率,而没有反映氮肥对土壤氮消耗的补偿效应。由于概念和算法本身缺陷,加之对结果解析和理解不够,在文献和日常交流中产生了许多误区。为此,国内外研究者尝试了许多改进算法,虽涉及到氮肥在后茬作物上的残效,但并未触及到残留肥料氮对土壤氮消耗补偿效应这一核心问题。本文根据土壤-作物体系氮素主要流动通量,及肥料氮-土壤氮-作物吸氮＂三氮＂之间关系,提出了氮肥有效率的概念和算法,其核心是将残留肥料氮作为补偿土壤氮消耗的有效部分。文章分析了国内15N示踪试验资料,认为我国现有农田管理水平的氮肥有效率在50%-60%,损失率在40%-50%之间,损失率很高。采取改进氮肥和农艺管理措施,我国未来将氮肥有效率提高至70%-90%,是完全有可能的。氮肥有效率拓展了氮肥效应理念,在解析氮肥对作物增产、维持土壤氮肥力的真实效果,对环境的实质影响方面具有重要意义。

Since the invention and application of nitrogen（ N） fertilizer,people always wanted to measure the effects of N fertilizer application by nitrogen use efficiency（ NUE）. The traditional NUE is the percentage of fertilizer N uptake by crop to N fertilizer rate,which didn＇t consider the replenishing effect of fertilizer N to soil N consumption. Due to the defects of the concept and calculation,and the poor interpretations and understands of the results,there are a lot of misunderstands in the literature and daily communication. Therefore,many improved method for calculating NUE were proposed by researchers. However,although these methods had been involved the residual effects of N fertilizer on succeeding crops,they didn＇t touch the core issue of the replenishing effect of fertilizer N to soil N consumption. Based on the main N flows in the soil-crop system and the relationships between the fertilizer N,soil N and crop N uptake（ called three N）,I proposed the concept and calculation of nitrogen fertilizer availability ratio（ NFAR） in this study. The core item for NFAR is that the residual fertilizer N is regard as the replenishing to soil N consumption. I recognize that the NFAR is 50% ～ 60% and the loss rate of N fertilizer is 40% ～ 50% under current N management practices in China based on the analysis the data from the 15 N tracer field trial,which reflects the high loss of fertilizer N in practices. It is possible to increase NFAR to 70% ～ 90% by improved fertilizer N and agronomic managements. The NFAR expand the idea for the effects of N fertilizer application. It would be important for demonstrating the real effects of crop N uptake and soil N fertility maintain by N fertilizer,and would reflect real loss to environments of N fertilizer application.