摘要:农田氮素管理不当导致水体污染、土壤结构破坏和全球变暖等环境问题。从经济与生态环境各方面探讨华北平原冬小麦的最优施氮量可为粮食生产及区域农业生态保护提供重要的科学参考。本文利用华北平原9个站点1981—2017年的逐日气象数据及冬小麦物候和产量观测资料, 借助CERES-Wheat模型, 基于5个约束指标(产量、氮肥偏生产力、氮素吸收、增产-节氮权衡和环境-经济效益)和施氮量的关系曲线, 揭示华北平原冬小麦在不同约束条件下的最优施氮量。结果表明: 华北平原各站点基于不同目标约束所得的最优施氮量有所不同, 其大小顺序为氮素吸收>产量>环境-经济效益>增产-节氮权衡>氮肥偏生产力, 且各地区最优施氮量的参考值也存在一定的空间差异。通过对粮食安全与生态友好的综合考量, 本研究认为增产-节氮权衡和环境-经济效益约束条件下的最优施氮量能够实现经济效益和生态效益的统一, 是较合理的区域施氮参考, 该条件下最优施氮量分别为173 kg?hm?2和190 kg?hm?2, 比当前华北平原农民实际施氮水平分别减少约47%和42%, 可以作为冬小麦种植施氮的区域参考值。该目标约束下最优施氮量的低值主要分布在Ⅱ区和Ⅳ区, 分别为150 kg?hm?2和170 kg?hm?2, Ⅰ区和Ⅲ区则相对较高, 最优施氮量分别为200 kg?hm?2和225 kg?hm?2, 原因可能在于长期施氮降低土壤有机碳含量, 进而影响土壤供氮能力。
关键词:华北平原/
CERES-Wheat模型/
冬小麦/
农业生态环境/
最优施氮量/
多目标约束
Abstract:The oversupply of nitrogen fertilizers has caused serious environmental problems, such as water pollution, destruction of soil structure, and global warming. Thus, the optimal nitrogen application rate of winter wheat should consider the environmental impacts. Many attempts have been made to evaluate the optimal winter wheat nitrogen application rate using different indicators, such as yield, nitrogen use efficiency, and nitrogen uptake. However, previous studies have only focused on economic benefits and did not consider the ecological benefits. Furthermore, the optimal nitrogen application rates have been evaluated with individual indicators; a systematic approach that integrates these indicators has not yet been presented. To better understand the optimal nitrogen application rate for winter wheat under multi-objective constraints in the North China Plain, this study used the daily meteorological data, observation data of the phenology, and the yield of winter wheat at nine stations (Tangshan, Huanghua, Luancheng, Huimin, Nangong, Ganyu, Shangqiu, Zhumadian, and Shouxian) from 1981 to 2017, to simulate five indicators of the economic and environmental benefits of the winter wheat (yield, nitrogen partial factor productivity, nitrogen uptake, the balance between yield increase and nitrogen saving, and environmental-economic benefits) by using the crop estimation through resource and environment synthesis (CERES)-Wheat model. The relationship between each indicator and the nitrogen application rate was investigated to determine the optimal nitrogen application rates under different constraints. Finally, the comprehensive optimal nitrogen application rate was determined according to the economic and ecological benefits. The results indicated that the optimal nitrogen application rates varied across stations and objective constraints. The average value of the optimal nitrogen application rate for the nine stations from high to low were that constrained by nitrogen uptake (363 kg?hm?2), yield (257 kg?hm?2), environment-economic benefits (190 kg?hm?2), the balance between yield increase and nitrogen saving (173 kg?hm?2) and nitrogen partial factor productivity (30 kg?hm?2). The optimal nitrogen application rates under the constraints of the balance between yield increase and nitrogen-saving and environmental-economic benefits were 173 kg?hm?2 and 190 kg?hm?2, respectively. This indicates a reduction by approximately 20%?30% of the nitrogen application rates for constraints related to yield maximization, and reductions by 47% and 42% compared to the actual nitrogen application rates of farmers in the North China Plain. Thus, the environmental damage caused by nitrogen fertilizers can be minimized under these constraints. Meanwhile, approximately 90% of the wheat yield can be obtained with these optimal nitrogen application rates, and economic and ecological benefits can be simultaneously guaranteed. To secure grain production and minimize environmental impacts, the optimal nitrogen application rates under the constraints of the balance between yield increase and nitrogen-saving and environmental-economic benefits can be regarded as the regional reference for winter wheat planting in the North China Plain. The regional reference of the optimal nitrogen application rates for winter wheat varied with zones, it was 150 kg?hm?2 in the piedmont plains of Taihang Mountain and Yanshan Mountain, and 170 kg?hm?2 in the Nanyang Basin. For the winter wheat in the Shandong Peninsula and the plains around Bohai Sea, the optimal nitrogen application rate was higher (200 kg?hm?2), and in the Haihe Plain, the optimal nitrogen application rate was 225 kg?hm?2.
Key words:North China Plain/
CERES-Wheat model/
Winter wheat/
Agricultural ecological environment/
Optimal nitrogen application rate/
Multi-objective constraints
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