【作者】 陆敏；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 自然地理， 2007， 博士

【摘要】 氮素是地球上生物的重要生源要素，长期以来人类一直从生物圈生态发展和满足人类食物需求的角度加以研究和利用。而随着农田化肥施用量的不断增大，农田养分物质的大量流失已成为内陆湖泊富营养化的主要原因。农田过量施入的氮通过氨挥发和反硝化作用，成为重要的温室气体影响大气质量和生态平衡。农业非点源污染已成为人们关注的一个热点问题。本文选择上海市郊最主要的农业生产方式—水旱轮作方式（稻-麦轮作），以农田生态系统中土壤-作物-水作为整体研究对象，分析和探讨了在大田条件下，各系统间物质的氮转换、循环和平衡特征，估算水旱轮作时氮素的流失量以及对水环境影响。主要研究结论如下：（1）水旱轮作过程中土壤水的运动和方向均表现出不同的特点。稻季主要在淹水条件下的饱和运动，而麦季则主要是受降雨影响下的不饱和运动。研究表明，稻季农田径流以及麦季径流和渗漏均与降雨事件有关，表现出随机发生的特性，同时在特定的土壤和环境条件下，又表现出一定的规律特征。稻季和麦季降雨量与降雨径流量均呈显著指数相关；而麦季降雨量和土壤渗漏水量则呈显著线性相关。（2）水旱轮作过程中，土壤氧化还原交替变化是控制和影响土壤氮转化方向和结果的主要因素，土壤剖面氮的形态和浓度变化也影响着土壤水的变化规律。稻季由于经常灌溉淹水，还原作用强，抑制了土壤NH₄⁺-N转化为NO₃^--N物质，土壤NO₃^--N在季节上和剖面变化均较小，变幅在0.95～6.42 mg／kg，施肥处理与不施肥处理差异不明显。而麦季土壤转化为氧化状态，硝化作用增强，施肥处理土壤NO₃^--N含量在季节变化和剖面分异均较显著，浓度变幅在1.22～15.2mg／kg。由于土壤对NH₄⁺-N具有较强的吸附能力，在整个水旱轮作过程，施入土壤中的氮肥主要影响表层土壤NH₄⁺-N变化和转化，向下迁移数量极少。在仅施化肥条件下，种植前后施肥处理土壤NH₄⁺-N和NO₃^--N没有明显累积，而总氮略有增减，对土壤氮素肥力水平没有明显影响。（3）土壤水旱轮作过程中，土壤NH⁺-N含量与土壤水中NH⁺-N浓度相关性不显著，NH⁺-N主要被土壤大量吸附并保持，土壤剖面各层水中NH⁺-N浓度均较低，大多小于1mg／L。而土壤NO₃^--N含量与土壤水中NO₃^--N浓度存在较显著相关特性，也反映NO₃^--N物质不易被土壤吸附并保持。稻季土壤淹水还原，各层水中NO₃^--N浓度较低，淋移不明显。麦季施肥处理土壤水中NO₃^--N浓度变化明显，在0.09～30.58mg／L之间，60cm以上土层水中76％超过5mg／L，51％超过10 mg／L，并有向下淋移的特点，浅层地下水（120cm处）NO₃^--N不同程度有所抬高。（4）农田氮素流失与氮肥用量和种类、土壤性质、降雨、水文条件、耕作方式和管理、植被等因素有关。其中，施肥量和降雨是最基本的影响因子，而土壤氧化还原作用的差异，使麦季和稻季径流和渗漏水中氮形态和浓度表现出不同的特征。稻季氮素流失中，以施肥后一周内发生降雨径流中NH₄⁺-N浓度较高，对水环境质量产生一定影响。而麦季降雨氮径流和渗漏流失，均受施肥影响，表现出浓度高和流失量大的特点，严重影响地表和地下水质量，是水旱轮作最主要的氮污染源。设计控制的减量施肥技术在不影响作物产量下对减少农田氮流失效应是显著的。（5）农田氮素随降雨径流流失是一个重要的过程，根据本次农田NH₄⁺-N降雨径流流失规律，在试验的基础上提出其运移和转化的数学模型，并对其流失动态进行模拟研究，其模拟值与试验值拟合度较高，R值达到了0.89和0.99。认为模型中的参数和数据容易在农田生产过程中获取，且计算方法简便，是一个较好的预测和控制农田氮径流流失的数学模型。（6）两年水旱轮作农田氮素流失定位监测和分析，过量施肥、不合理的耕作和管理方式是农田氮素大量流失的主要原因。改进施肥技术，考虑化肥用量的增产经济效益，采用节水灌溉技术，提高肥料利用效率，以减少对环境的污染排放。尽快制定相关法律法规和教育宣传，并推出有效的激励措施，保证环境保护目标的实现。（7）采用氮收支法研究了试验区农田系统氮平衡特征，氮表观回收率在59％～78％之间，水稻略高于小麦。农田氮素随水流失量少，稻季和麦季平均分别为2％和7％，而气态损失则高达25％和29％，农田氮素气态损失是水旱轮作最主要的损失途径，也是大气环境的重要的污染源。更多还原

【Abstract】 Nitrogen is the important growth source of biological living on earth. Human being study and utilizes nitrogen from biosphere development and satisfaction of food needs all the while. With the increase of fertilization, nutrient matter loss has become the main reason of eutrophication of the inland lake. Excess nitrogen in the field from using fertilizer, being partially lost through ammonia volatilization and denitrification, can become important greenhouse gas and affect the atmosphere quality and ecological balance. Agriculture non-point source pollution has received much attention today.A field experiment was conducted in a paddy-wheat planting soil in the support of Shanghai. Base on the soil- crop- water systems as the overall object of study, discusses the nitrogen changes , cycles, balances process and the characteristic between every sub-system under field condition, and estimates the total N loss in the paddy-wheat planting and effect to the water environment. The main conclusions can be summed up as follows:（1） There are the different characteristic at the motion and direction of soil water in process of paddy- wheat rotation. In paddy season, the main saturation motion is under water-flooding condition, while the dominating motion is unsaturated motion by affection of rainfall in wheat season. The study result indicates that the runoff and leaching both in paddy and wheat season are relate with rainfall and show the characteristic happening randomly, while they also appear law characteristic under the given soil and environment condition. There is obvious index correlation between rainfall runoff and rain fall in paddy and wheat season, meanwhile, the linear correlation between rainfall and leaching in soil is also very clear in wheat season.（2） Oxidation-reduction changing alternately in process of paddy- wheat rotation is the main element for controlling and affecting to the result and direction of nitrogen conversion in soil. The form and concentrations change of nitrogen in the soil profile also influence changing of soil water. Because of the frequent irrigation in paddy season, the reduction is strong and the NH₄⁺-N of soil cannot convert to the NO₃^--N in soil, the seasonal change of NO₃^-N in the soil profile is small and the range is from 0.95 mg/kg to 6.42 mg/kg. Fertilization or not is not have significant difference. However it changes to oxidation condition and nitrification is enhanced in wheat season. The content of NO₃^--N with fertilization is obvious change both in season and soil profile. The range of the concentration is from 1.22 to 15.2 mg/kg. Because of soil matter has strong adsorption ability to NH₄⁺-N, during the whole paddy-wheat rotation, the N fertilizer is main influence the change and transform of NH₄⁺-N in surface soil and little of them move down. Under using abio-fertilizer only, NH₄⁺-N and NO₃^--N in soil do not cumulate obvious at the front and end of cultivate and the total N changes slightly. There is not evident influence to the level of nitrogen fertility in soil. （3） Because of soil matter has strong adsorption ability to NH₄⁺-N, during the whole paddy-wheat rotation, the concentrations of water in soil profile is low all, most of them lower than 1 mg/L.The concentration of NO₃^--N is lower in the water of soil profile in paddy season, leaching is not obvious. The change concentrations of NO₃^--N in soil water with fertilization is markedly, from 0.09 to30.58 mg/L. The 76% of NO₃^--N concentration in soil water are exceed 5 mg/L above 60 cm of soil and 51% of that exceed 10 mg/L. with the characteristic of leaching, concentrations of NO₃^--N at shallow groundwater（120 cm） increase in different degree.（4） The N loss from farm relate to the factors about the amount and species of fertilizer, the texture of the soil, the rainfall, the hydrology conditions, cultivation, management and vegetation. From these, fertilizer and rainfall are the basic factors of effect, redox condition of the soil is different tent to form and concentration of nitrogen in the surface runoff and leaching are different in paddy and wheat season. NH₄⁺-N concentration is higher during the first week after fertilizer and affect the quality of water environment in paddy season. The N loss both of runoff and leaching are affected by the fertilization and have high concentration and great loss in the wheat season’s rainfall. It severity affected the quality of groundwater and surface water. It was the main N pollution source in process of paddy- wheat rotation.（5） The N loss of surface runoff is a key process from farm. A math model was developed according on the rule of NH₄⁺-N loss of surface runoff from this experiment. The model simulated the process and transform of the surface runoff. The results are very approach the real experiment date: the R is 0.89 and 0.99, respectively. This model’s parameter and date is considered easily to get from production process. Since it can also calculate conveniently, it’s a good math model to predict and control the NH₄⁺-N loss of surface runoff from farm.（6） On two years’ monitor and analysis of the paddy- wheat rotation, over fertilization and irrational cultivation and management is the main reason of N loss from farm. In order to reduce the pollution environment, the technique of fertilizer, increase the efficiency of fertilizer using, introduce irrigate technique, and other techniques should be improved, related law and regulations be established, education and propaganda be done and efficient encourage measure be mapped out to protect the environment.（7） Adopting N income and expenses methods to study the N-balance character in the farm system. The results show that the N’s apparent recovery is between 59% and 78%, paddy is a bit higher than wheat. The N loss with farm water outflow is comparatively low, about 2% and 7% in paddy and wheat season, respectively. The gas loss is higher in 25% and 29%. So the gas loss is the key way of N loss in paddy-wheat rotation from farm and the important pollution source of atmosphere pollution.更多还原