长期施肥导致农田土壤酸化的机制及缓解策略

发布时间：2018-03-19 21:32

本文选题：农田土壤酸化　切入点：氢离子产生　出处：《中国农业大学》2017年博士论文　论文类型：学位论文

【摘要】：近几十年来,过量氮肥投入导致中国农田土壤发生显著酸化,对未来粮食安全的风险日益加剧。在自然生态系统中,大量研究表明,定量评价土壤酸化过程不仅为阐明酸化机制提供理论基础,还能为未来酸化治理提供政策建议。相比而言,对于农田土壤酸化过程定量化的研究相当缺乏。为深入理解农田土壤酸化过程,特别是揭示驱动土壤酸化的关键过程,定量研究土壤酸化主要驱动力的贡献,明确未来基于酸化改良的农田管理措施,验证基于模型分析的缓解土壤酸化的有效措施,本研究以产生氢离子(H+)的农田物质循环过程为研究对象,通过盆栽试验揭示物质循环过程H+产生与土壤实际酸化的定量关系,明确土壤pH对土壤氮素循环和氮肥产酸量的影响;利用土壤酸化模型定量评价长期施肥条件下,农田土壤酸化主要驱动力的贡献,提出缓解农田土壤酸化的措施,并结合田间试验验证改良措施对缓解土壤酸化的贡献。主要研究结果和结论如下:1.定量了不同类型氮肥的氢离子产生量、以及物质循环过程氢离子产生与土壤实际酸化的关系。铵态氮肥处理的H+产生量是尿素处理的3.8倍,高于两种肥料H+产生的理论比值2.0;实际肥料产酸量的高低很大程度上取决于土壤的硝化反应能力,硝化能力越强的土壤两者H+产量比值越接近理论值。在非钙质土壤上,氮(N)和碳(HCO3-)循环过程的产酸量与土壤盐基离子库的减少量呈显著的1:1正相关;在钙质土壤上,两者仅呈正相关。验证了非钙质性农田土壤,可以通过外源物质的输入-输出平衡计算H+产生量,量化土壤酸中和能力的变化,即实际土壤酸化速率,为进一步深入研究奠定了理论基础。2.揭示了土壤pH对氮素循环进而对肥料H+产生量的影响。随着土壤pH值的降低,土壤硝化、反硝化、氨挥发降低,淋洗液中的铵硝比显著增加,氮循环过程的氢离子产生量也显著降低;不同土壤类型对pH改变肥料产酸量的效应有一定的影响,这种效应在硝化能力弱的土壤上不显著;等量氮肥施用条件下,中性土壤与碱性土壤实际酸化速率相近,显著高于酸性土壤,而中性土壤缓冲能力一般较低,其酸化问题应受到关注。3.明确了长期施肥情况下农田土壤酸化的主要驱动力,并量化其贡献。基于我国三个长期定位试验的测定数据,应用进一步发展的VSD+模型模拟了农田土壤酸化趋势。模型很好的反映了不同条件下(气候、轮作体系和土壤类型)长期施用肥料对土壤pH和盐基饱和度的影响;在酸敏感区域的土壤上,定量了土壤酸化主要驱动力,发现在氮肥施用处理中N过程占总H+产生量的80%,而在不施氮处理中,盐基离子吸收也是土壤酸化的重要来源,约占总H+产生量的1/3。4.证明了提高氮肥利用率(NUE)能够显著降低农田土壤酸化速率。通过对不同缓解措施的预测发现,最有效的土壤酸化防治措施是优化氮管理,降低铵态氮的输入和硝态氮的淋洗,以及施用有机肥来增加盐基离子(BC)的输入,维持土壤BC平衡。结合三年的田间试验表明,NUE提高20%能够降低23%的肥料H+产生量。综上所述,本研究系统阐明了农田土壤酸化的过程,即揭示了非钙质性土壤上外源物质输入产酸量与实际土壤酸化1:1的正相关关系,从外源物质产酸量的定量研究中,明确了中性土壤的酸敏感,定量评价了农田土壤酸化主要驱动力的贡献,指出优化氮肥管理,合理降低氮肥用量、提高氮肥利用率、减少硝态氮的淋洗,通过施用有机肥、石灰等,保持土壤盐基离子平衡,是缓解高度集约化农业土壤酸化的重要途径。
[Abstract]:In recent years, excessive nitrogen fertilizer caused significant China acidification of farmland soil, the risk of future food security is increasing. In the natural ecosystem, a large number of studies show that the quantitative evaluation of soil acidification process not only provides a theoretical basis for elucidating the mechanism of acidification, also can provide policy suggestions for future acidification governance. In contrast, for the study of the soil acidification process is lack of quantitative. For further understanding the soil acidification process, especially the key to reveal the process driven soil acidification, the main driving force of the quantitative contribution of soil acidification, acidification clear future farm management measures based on the improvement of verification, effective measures to alleviate the soil acidification model based on the analysis, the research to produce the hydrogen ion (H+) of farmland material recycling process as the research object, to reveal the material recycling process H+ production and soil by pot experiment The quantitative relationship between rhizosphere acidification, a clear effect of soil pH on soil nitrogen cycling and nitrogen acid production; evaluation of long-term fertilization conditions by quantitative soil acidification model, the main driving force of soil acidification contribution, and puts forward some measures of soil acidification, and combined with the contribution of field test validation of improved measures to alleviate soil acidification. The main research the results and conclusions are as follows: 1. quantitative hydrogen ions of different types of nitrogen fertilizer production, and material recycling process of hydrogen ion has a relationship with the real soil acidification. Ammonium nitrogen fertilizer of H+ production is 3.8 times higher than that of urea treatment, the theoretical ratio of two H+ fertilizer produced 2; nitrification ability actual fertilizer production acidity depends largely on the soil, soil H+ yield ratio nitrification ability is stronger the more close to the theoretical value. In non calcareous soil, nitrogen (N) and carbon (HCO3-). Ring process of acid production and soil base to reduce the amount of base cations was significantly positively related to 1:1; in calcareous soil, both were positively correlated. Verify the non calcareous soil, by exogenous substances input-output balance calculation of H+ production, change to quantify soil acid neutralizing capacity, the actual soil the acidification rate, laid the theoretical foundation of.2. reveals the soil pH in nitrogen cycle of H+ fertilizer production was analyzed for further study. With the decrease of soil pH value, soil nitrification, denitrification, ammonia volatilization reduction, increase in eluent ammonium nitrate ratio significantly, hydrogen ion nitrogen cycling process yield decreased significantly; have certain influence effect of different soil types on pH fertilizer acid production, this effect is not significant in the nitrification ability weak soil conditions; nitrogen fertilizer amount, neutral soil and alkaline soil acidification practice The rate was significantly higher than that of similar, acidic soil, neutral soil buffer capacity is generally low, the acidification problem should be paid close attention to.3. long term fertilization condition of main soil acidification of the driving force, and quantify their contribution. Determination of three long-term positioning of our test data based on the VSD+ model for further development and application of simulation the soil acidification trend. The model reflects the different conditions (climate, cropping system and soil type) effects of long-term application of fertilizers on soil pH and base saturation; in acid sensitive areas of soil, soil acidification quantitatively the main driving force, found in the nitrogen fertilizer treatment N total H+ production process 80%, while in the treatment without nitrogen, an important source of base ion absorption is soil acidification, about the total amount of H+ produced 1/3.4. proved that the utilization ratio of nitrogenous fertilizer (NUE) can significantly reduce soil The acidification rate. By predicting the mitigation measures for different found that soil acidification prevention is the most effective way to optimize nitrogen management, reduce the input of nitrate nitrogen and ammonium nitrogen leaching, and application of organic fertilizer to increase the base cations (BC) input, maintain soil BC balance. According to field test for three years. 20% increase in NUE can be reduced by 23% H+ fertilizer production. In summary, this study illustrates the process of acidification of farmland system, which reveals the non calcareous soil on the exogenous material input and actual soil acidification yield was positive correlation between 1:1, from quantitative research abroad source acid production in the neutral soil acid sensitive, quantitative evaluation of soil acidification of the main driving force of the contribution, pointed out that the optimization of nitrogen management, reasonably reduce the amount of nitrogen fertilizer, improve the utilization rate of nitrogen fertilizer, reduce nitrate leaching, by applying organic manure, lime, etc., Maintaining the ion balance of soil salt base is an important way to alleviate the acidification of highly intensive agricultural soil.

【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S156.6

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