【作者】 马林；

【导师】 马文奇； 张福锁；

【作者基本信息】 河北农业大学 ， 土壤学， 2010， 博士

【摘要】 过去几十年以来,中国人口不断增长,国民生活水平不断提高,为了满足日益增长的食品需求,生产更多的农畜产品,农民施用了大量氮肥。过量的氮素将导致一系列严重的生态环境问题。然而当前,对于食物氮素需求、氮素投入和环境排放的定量化研究、对于氮素在食物链系统的流动规律研究以及氮素在区域尺度上调控策略的研究仍然十分匮乏。因此本研究通过构建模型进行定量分析,揭示氮素在食物链系统中的流动规律,阐明中国食物链氮素流动的现状及其历史变化趋势,探究氮素流动引发的资源和环境代价,为实现氮素(或者养分)优化管理和可持续的现代农业发展策略提供科学依据。本文主要研究结果如下：(1)首次实现在国家和区域尺度上,从食物链角度对氮素平衡、环境排放、利用效率及流动规律进行定量分析。NUFER模型是中国第一个能够在国家和区域尺度上对氮素流动,氮素生产效率,NH3、N2、N2O挥发,淋溶,径流和侵蚀损失进行综合评价的模型。该模型还可以根据不同的养分管理技术和政策法规对流动状态的影响进行评估。(2)2005年,中国食物链系统氮素总投入为48.8百万吨,而食物氮素产出仅为4.4百万吨,绝大部分氮素排放到环境中,其中23百万吨进入大气环境,20百万吨排放到水体环境。2005年,中国食物链系统氮素利用效率(NUEf)仅为9%,这意味着,每生产1 kg食品氮需要投入外源氮11 kg。作物生产子系统和畜禽生产子系统氮素生产效率分别为26%和11%。(3)2005年,黄淮海区化肥、饲料、植物食物和动物食物氮素盈缺率分别为33%、-120%、38%和65%。养分势是区域食物链养分流动的原动力,此外,人口数、城镇化率、耕地面积、GDP、运输距离、运价、市场价格和政府调控等也是影响食物链氮素养分在区域间流动的重要因素。2005年,黄淮海区不仅是化肥、食物氮素的源,而且是饲料氮素的汇。北京地区无论化肥、饲料和食物氮素都为汇。北京地区单位耕地承载外地区调入的氮素养分负荷为872 kg hm-2。即使这些养分全部在本区域返还农田还存在很大的环境风险。因此,对环北京都市圈食物链氮素养分应该进行区域间协同管理。(4)2005年中国农田和畜牧体系氮素排放量分别为216和111 kg N hm-2,通过水体排放、NH3、N2和N20损失分别为155、117、52和4 kg N hm-2。情景分析显示通过供需平衡、畜禽粪尿管理和作物综合管理可以提高氮素生产效率,减少环境排放,同时提高作物产量。(5)随着GDP增长,在食物消费拉动下,2005年人均化肥、饲料、食物氮素消费量分别为1980年的2.1、2.2和1.3倍,养活一个中国人的资源代价在增加。中国食物链氮素库存量和流量大幅增长,1980年到2005年农田氮素总流量从2104万吨增加到4355万吨,动物生产体系氮素流量从745万吨提高到2255万吨。家庭消费系统氮素流量从313万吨增加到436万吨。然而,2005年食物链氮素生产效率仅为9%,废弃物循环率下降。与此同时,食物链氮素流动排放造成巨大环境压力,2005年食物链系统进入环境氮素为4288万吨,是1980年的2.4倍。(6)氮素在食物链系统流动受到拉动力、控制力、约束力和推动力等力的合力影响,各种力从不同角度影响着氮素在食物链系统的流动,既包括自然因素又包括社会因素。通过线性规划,定量各种力的作用下的不同发展情景。结果表明：在拉动力、约束力、控制力和推动力的合力的作用下(情景5),在人口数、膳食结构、城镇化率等因素的拉动下,食品氮素消费量将达到6.5百万吨,比2005年增加48%。而约束力是不能支持大量的外源氮投入,环境承载力也是不允许的。因此,唯有在调控力和推动力的作用下,外源氮素投入仅增加12%,氮素环境排放量仅增加7%。于此同时,食物链系统氮素生产效率由9%增加到16%。更多还原

【Abstract】 Increasing nitrogen (N) fertilizer application has greatly contributed to the long term food security in China during the last four decades but also contributed to rapidly increasing N losses to groundwater, surface waters and air. However, the quantitative insight and relationship between food N demand, N input and N losses to environment, the mechanism of nitrogne flow in the food chain, the pathways and effect of different nitrogen managements are still lacking. Here, we present N flow budget, the feature of nitrogen flow from food chain perspective and the effect on envrioment at national and regional scale of year 2005, using the model NUFER (NUtrient flows in Food chains, Environment and Resources use). The nitrogen flow mechanism and managemtent strategies in the Food Chain of China should be expolored further. The main results were as follows:(1) It is the first comprehensive overview of N balances, losses, use efficiencies and N flow mechanism of the food chain at national and regional scale in China. NUFER also allows to estimat changes in N flow budget due to different N management strategies.(2) Total amount of ’new’ N put to the food chain was 48.8 Tg in 2005. Only 4.4 Tg reached households as food nutrient. Average N use efficiencies in crop production, animal production and crop and animal production and food processing were 26.4,11.1 and 8.9%, respectively. Most of the applied N was lost to the environment, in which 23 Tg N to atmosphere and 20 Tg to waters.(3) The surplus and deficiency rate of fertilizer、feed、plant food and animal food was 33%、-120%、38%、65%, respectively in 2005 in Huang-Huai-Hai. The driving force of nutrient flow in local food chain is the potential nutrient. But the factor of population、urbanization、arable land area、GDP、transport distance、transport price、market price and policy etc also have influence on it. In 2005, the area of Huang-Huai-Hai is the source of nitrogen of fertilizer and food, and the stock of nitrogen of feed. But in Beijing, nitrogen of fertilizer, food and feed all is the stock. The average cropland load of nitrogen which comes from other provinces is 872 kg hm-2, which still has a great risk to environment even though all this nitrogen has been returned to the cropland. So the collaborative management of nutrient should be carried on in Beijing-Tianjin metropolis circle immediately. (4) Mean N losses from crop and animal system amounted to 327 kg hm"2 agricultural land in 2005. On average 66% of the N losses originated from crop production and 34% from animal production systems, but regional variations were large. Leaching to groundwater and surface waters was the main loss pathway, ranging from 33 to 300 kg N hm-2 among provinces. Volatilization of NH3 was the 2nd main loss pathway (range from 29 to 215 kg N hm-2). Mean emissions of N2O ranged from 1 to 6 kg N hm-2. Highest N losses were estimated for provinces in south east and in the North China Plain with highly intensive agricultural systems, In the balanced fertilization scenario, mean N losses decreased by 34% relative to the baseline scenario, but with large differences between provinces (range from-35% to 57%). In scenario 2 (improved manure management), mean N losses by another 7%. In scenario 3, we assumed a 20% increase in crop yields, as a result of higher-yielding varieties and improved water, nutrient and pest management.(5) With the growth of GDP and food consumption, the amount of fertilizer, feed, the food nitrogen consumption per capita are increasing dramatically, which in 2005 were 2.1,2.2 and 1.3 times of that in 1980 respectively, and the resources cost to support one Chinese is increasing year by year. With the increasing of food demand, the nitrogen amount of pool and the flow in the food chain in China grew remarkably. In 2005, the amount of nitrogen flow of crop production, animal production and household consumption were 43.5,22.6 and 4.4 Tg and that in 1980 were only 21.0, 7.5 and 3.1 Tg, respectively. However, the nitrogen use efficiency of food in china was only 9% in 2005 and the waste recycling rate was decreased. Meanwhile, the remainder of nitrogen to a great part lost to the environment, which means that 42.9Tg N lost to atmosphere and water in 2005, which were 2.4 times of that in 1980. Hence, food chain system has become the channel of nitrogen activated.(6) With composition forces of the pull, impetus, sanction and control forces (scenario 5), the food N consumption woule be 6.5 Tg and increasing 48% compared with that in 2005, based on the changing of populations, food structure and urbanization etc. But there are limited resources, which can not surport so many "New N" input, and environment effect as well. Hence, nitrogen use efficency should be increased under the control forces and impetus. Extending the implementation of nitrogen management, "New N" will be increasing 12%, losses to environment increasing 7%, and nitrogen use efficiency will increase from 9% to 16%.更多还原