【作者】 颜冬冬；

【导师】 曹坳程；

【作者基本信息】 中国农业科学院 ， 农药学， 2013， 博士

【摘要】 保护地栽培和连作为土传病虫害的发生与发展提供了适宜的环境，目前土传病害和根结线虫已经成为严重制约保护地生产发展的重要因素。土壤熏蒸处理是防治土传病害最直接、最有效的方法。由于熏蒸剂的广谱性，在使用过程的同时也会影响到土壤中的非靶标土壤微生物。土壤中氮素矿化、硝化和反硝化作用是氮素循环过程中最为重要的3个过程，是提供土壤中植物可以吸收利用有效态氮的主要生物学途径，熏蒸对土壤氮素循环功能微生物的影响会直接影响到土壤中有效态氮含量的动态变化。本论文的研究目的之一是要明确不同熏蒸条件下土壤中硝化作用的生物学及动力学特性，包括不同熏蒸剂，不同土壤因素对土壤硝化作用的影响；研究目的之二是要明确熏蒸土壤中氧化亚氮的产生的生物学机制。论文的研究结果能够更加全面了解土壤熏蒸消毒的作用机理，达到从农业生产和生态环境角度综合评价熏蒸剂的经济和环境效益的目的。通过本实验研究得出以下主要结论：1、结合室内培养和田间试验定量评价了熏蒸土壤中矿质氮的动态变化，采用典型的土壤硝化作用动力学模型求解了不同熏蒸土壤中硝化作用的动力学参数，从动力学和生物学角度综合评价了熏蒸土壤中硝化作用的特性。室内不同熏蒸剂处理土壤研究结果表明，熏蒸剂延缓了土壤中铵态氮向硝态氮的转化，抑制了土壤中硝化作用过程。氯化苦、1,3-二氯丙烯、二甲基二硫和威百亩4种熏蒸剂处理土壤中，氯化苦处理对土壤中硝化作用抑制效应最持久，t_max（最大硝化作用速率发生的时间）为14.37周。通过添加不同浓度氯化苦和1,3-二氯丙烯处理对土壤中硝化作用的影响的数据结果可以看出，两种药剂对土壤硝化作用的抑制程度与处理浓度之间存在一定剂量效应关系，处理浓度与t_max值之间均呈显著的正相关（P<0.05）。以熏蒸剂处理浓度对数值为x、硝化作用抑制率机率值为y，建立熏蒸剂处理浓度与抑制率机率值之间的回归方程，求解得出熏蒸剂对硝化作用抑制中浓度，氯化苦和1,3-二氯丙烯IC50分别为65.73mg kg^-1和25.74mg kg^-1。室内熏蒸培养对土壤中氮素的矿化作用影响不明显。4种熏蒸剂田间试验结果表明，熏蒸处理短期内（1周）显著提高了土壤中铵态氮的含量，同时促进了短期内（1-2周）氮的矿化作用，提高了氮素的矿化速率，此外田间条件下熏蒸土壤中硝化作用的恢复速率要快于室内培养条件。2、熏蒸显著增加了土壤中铵态氮以及可溶性氨基酸含量，但不同地区熏蒸土壤中矿质氮的动态变化存在一定的差异。砂壤土熏蒸处理后土壤中铵态氮能较快的恢复至稳定水平，酸性土壤熏蒸处理土壤中铵态氮需要较长的恢复时间。5个不同地区熏蒸土壤中硝化作用强度均受到显著抑制，在后续的培养过程中均有不程度的恢复。5种未熏蒸的土壤中表观硝化率在培养第3周均达到90%以上，而熏蒸土壤中表观硝化率则明显低于未熏蒸处理的土壤，熏蒸处理后第1周5种土壤中硝化抑制率均在70%以上，除广西酸性土壤外其他4种土壤中硝化抑制率在培养第18周后均降至10%以下。4个不同地区土壤中硝化作用动力学结果表明，未熏蒸土壤中最大硝化作用速率均发生在培养过程的第2-3周之间，而在熏蒸土壤中t_max均要大于未熏蒸处理的土壤，熏蒸对陕西土壤的硝化作用抑制时间最长，对北京砂壤土硝化作用抑制时间最短。3、通过研究了4种不同熏蒸剂（氯化苦，1,3-二氯丙烯，二甲基二硫，棉隆）处理后土壤氧化亚氮的动态变化规律，明确了熏蒸处理对土壤中氧化亚氮的释放的影响。同时采用微生物-乙炔-氧气抑制法研究了熏蒸土壤中氧化亚氮的产生的生物学途径。研究结果表明，棉隆和氯化苦熏蒸处理能显著增加土壤中氧化亚氮的释放量，并且棉隆和氯化苦熏蒸处理后氧化亚氮的累积释放量也显著高于对照以及二甲基二硫和1,3-二氯丙烯熏蒸处理。对熏蒸处理土壤中可溶性氮素组分和硝化反硝化作用的结果看出，4种熏蒸剂都显著抑制了土壤硝化作用，而棉隆和氯化苦显著促进了反硝化作用。此外熏蒸能显著提高土壤中铵氮和可溶性氨基酸含量，减少土壤中微生物量碳氮的含量。微生物-乙炔-氧气抑制培养试验结果表明，氯化苦熏蒸土壤中氧化亚氮的主要贡献为好氧细菌的反硝化作用过程，而棉隆熏蒸土壤中氧化亚氮增加可能主要源于真菌的反硝化作用过程。氯化苦和棉隆在土壤中降解产物作为氮源促进了土壤中反硝化作用过程的进行，导致了熏蒸土壤中氧化亚氮含量的增加。更多还原

【Abstract】 Greenhouse cultivation and continuous cropping provide a suitable environment for occurrenceand development of soil borne diseases and pest. Soil borne disease and root knot nematodes havebecome a serious restriction upon greenhouse production. Soil fumigation is highly direct and effectivetechnique to control continuous cropping disease. However, fumigants are a class of pesticide withbroad biocidal activity and affect many non-target soil organisms. Soil nitrogen mineralization,nitrification and denitrification are the most important processes in soil nitrogen cycle and these threeprocesses are the main biological pathways which provided soil available nitrogen uptake by plants.Fumigation cause significant impact on soil nitrogen microorganisms would directly affect the dynamicchange of soil available nitrogen. One objective of this study was to quantify the dynamic effects offumigation on nitrogen mineralization and nitrification in laboratory incubation and field studies.Another objective of the study was to identify the soil biotic group responsible for the production ofnitrous oxide following fumigation as well as to investigate the potential mechanisms of this nitrousoxide formation. The main conclusions are as follows:1. The dynamics and biological characteristics on soil nitrification process in different fumigatedsoils were evaluated in order to quantify the effects of fumigation on mineral nitrogen in laboratoryincubation and field studies. The results indicated all the fumigation treatments depressed nitrificationtemporarily, although the treatments exhibited significant differences in the duration of nitrificationinhibition. In both studies, for a limited period of time, Pic showed a stronger inhibitory effect onnitrification compared to other fumigant treatments. The time of maximum nitrification (t_max) in DMDSand MS treatments were0.97week and1.03week, which is similar to the untreated control (t_max=1.02week). While Pic has the longest effect on nitrifying bacteria, nitrification appears to restart at a latertime (t_max=14.37week). Dose-response relationship between the inhibition effect of nitrification andPic and1,3-D was observed, fumigant concentration and t_maxare significantly positive correlated（P<0.05）. IC50of Pic and1,3-D were65.73mg kg^-1and25.74mg kg^-1respectively. No obvious imapcton nitrogen mineralization in laboratory fumigation study was observed. But in field condition, soilfumigation was shown to increase soil ammonium and short-term nitrogen mineralization rates.Nitrification in fumigated soil in field condition has a faster recovery rate compared with laboratoryincubation.2. Fumigation was significantly increased soil ammonium nitrogen and dissolved amino acidscontent, but changes of mineral nitrogen in fumigated soil have some differences. Soil ammonium afterfumigation in sandy loam soil recovered much faster, but ammonium in acidic soil needed a longerrecovery time after fumigation. Nitrification was significant inhibited in all5fumigated soils and forlong-term incubation nitrification tended to recover. Nitrification rate reached up to90%in allunfumigated soils at3WAF, which were higher than fumigated soils. Inhibition rates of nitrificationwere all over70%in5different fumigated soils at1WAF. In addition to the acidic soil from Guangxiinhibition rate was decreased below10%after18WAF. The nitrification dynamic results from4 different areas showed t_maxin all unfumigated soils were all between2-3wk and nitrification appearedto restart at a later time in all fumigated soils. Fumigation caused the longest inhibition effect ofnitrification in soil from Shanxi and shortest in soil from Beijing.3. Selective inhibition method was used in order to identify the soil biotic group responsible for theproduction of nitrous oxide （N2O） in fumigated soil as well as to investigate the potential mechanismsof nitrous oxide formation. The results indicated higher N2O productions were found in Pic and DZfumigated soils and the production rates of N2O in Pic and DZ fumigated soils were significant higherthan DMDS and1,3-D treatments. Nitrification potential was significantly suppressed in4fumigatedtreatments, but the significant increase of potential denitrification rate indicated great stimulation on soildenitrification after Pic and DZ fumigation. Besides fumigated soils had drastic increase in ammoniumand DAA content and decrease in MBN and MBC. Based on the results from selective inhibitionincubation studies we hypothesize that the production of N2O following Pic fumigation ispredominantly due to aerobic bacteria denitrification process and fungal denitrification process could bethe potential source contribute to N2O production in DZ fumigation. Degradation products of Pic andDZ in soil as nitrogen source caused a great stimulation on soil denitrification which resulted in asignificant increase of N2O production.更多还原