【作者】 杨剑波；

【导师】 李辉信；

【作者基本信息】 南京农业大学 ， 生态学， 2012， 博士

【摘要】 尿素是我国农业生产中应用较为广泛的肥料,但在一般情况下,尿素的利用率很低。尿素施入土壤后在脲酶的作用下水解成氨,经硝化作用转化为易于移动的硝态氮,增加了氮素淋失和N20排放的风险。因此,调控硝化过程是减少氮素损失的有效途径。目前的研究表明,施用硝化抑制剂是一种有效的氮肥管理措施,能通过抑制氨的氧化,有效减少施肥导致的氮素淋失和N20排放,提高氮肥利用率。3,4-二甲基吡唑磷酸盐(DMPP)是一种新型的硝化抑制剂,具有用量低、抑制效果好的优点,并且对土壤和作物均没有毒害作用。本研究旨在调查DMPP在特定土壤上的抑制效果和影响范围,了解DMPP在土壤微生物学和酶学上的作用,探讨DMPP6勺作用机制,为DMPP的合理施用提供理论依据。具体研究结果如下：1、硝化抑制剂DMPP在不同土壤中的抑制效果不同。在培养期内,四种土壤的pH和铵态氮含量呈先上升后下降的趋势,硝态氮含量和表观硝化率呈逐渐上升的趋势。与单施尿素相比,施用DMPP显著增加了土壤pH和铵态氮含量,降低了硝态氮含量和表观硝化率。在水稻土和潮土中,单施尿素处理的硝化过程到第14天时基本完成,施用DMPP使硝化过程延长了28天完成。在黑土和红壤中,尤其是红壤,硝化过程相对缓慢,施用抑制剂虽然降低了土壤的表观硝化率,但降低的程度低于水稻土和潮土。2、硝化抑制剂DMPP改变了土壤微域环境(包括水平和垂直方向)中的氨氧化细菌群落结构,这种改变与土壤pH和无机氮的变化有关。在施肥区内,施用DMPP显著提高了土壤pH、铵态氮含量和无机氮总量,同时显著降低了土壤中硝态氮的含量,表现出强烈的抑制作用。在0-5cm范围内(包括水平和垂直方向),DMPP的抑制作用随着与施肥区距离的增加而逐渐减弱。单施尿素时,DGGE条带数量在水平和垂直方向上均是从施肥区开始逐渐减少,与铵态氮含量的变化趋势一致。相反,施用DMPP时,DGGE条带数量在水平和垂直方向的0-5cm内均呈增加趋势。两个处理相比,施用DMPP处理的条带数量在0-3cm内低于单施尿素处理,而在3-5cm内则高于单施尿素处理。DGGE条带的DNA序列分析表明本试验中氨氧化细菌的主要种类属于亚硝酸螺菌。3、硝化抑制剂DMPP通过抑制氨氧化细菌的生长有效延缓了土壤中的硝化过程。施用DMPP显著减少了氨氧化细菌的数量,提高了土壤pH和铵态氮含量,降低了亚硝态氮和硝态氮含量,而对氨氧化细菌群落结构无明显影响。随着培养时间的延长,DMPP的抑制效果逐渐减弱。在培养的前35天,不同用量DMPP处理之间的氨氧化细菌数量无显著差异,从第35天起0.5%DMPP处理的氨氧化细菌数量显著高于1%DMPP和2%DMPP处理。4、施用硝化抑制剂DMPP对尿素水解过程和硝态氮的还原过程无显著影响。在整个培养期内,土壤脲酶、硝酸还原酶、亚硝酸还原酶和羟胺还原酶活性在单施尿素处理和施用DMPP的处理之间均无显著差异,且在不同用量的DMPP处理之间也无显著差异。5、施用DMPP显著减少了温室气体N2O和C02的排放量,但是增加了氨的挥发。与单施尿素相比,施用DMPP延长了氨挥发的持续时间,显著增加了氨挥发总量。不同处理土壤中的N2O和C02释放趋势相似,二者的释放高峰在单施尿素处理中处于培养前期(1-7天),而在施用DMPP的处理中处于培养后期(20-35天)。与单施尿素相比,施用DMPP显著减少了N20和C02的排放总量。不同用量的DMPP对氨挥发量无显著影响,但是1%DMPP处理的N20和CO2排放量显著低于0.5%DMPP处理,且与2%DMPP处理无显著差异,因此推断DMPP在潮土中的适宜用量为施肥氮量的1%。更多还原

【Abstract】 Urea is widely used in agricultural production as a convenient source of nitrogen. However, when applied to soil, urea has been reported to have low N response efficiencies due to volatilization, nitrification, denitrification, erosion, runoff, and leaching. Previous studies indicate that nitrification inhibitors are useful in improving N use efficiency which can inhibit the oxidation of ammonium. Nitrification inhibitors have also been shown to be effective in reducing nitrate leaching and nitrous oxide emissions. More recently, the nitrification inhibitor,3,4-dimethylpyrazole phosphate (DMPP), has become available and was reported can be used at low application rate with high efficiency, and is also environmentally friendly.The objective of this study was to determine the inhibitory effect of DMPP on particular soil. The effect of DMPP on soil microbes and soil enzymes were also examined in order to demonstrate the mechanism of DMPP on nitrification inhibition. The outcome of this research may help formulate management decisions that aid in improving N application efficiency.The results of this research are as follows:The effect of nitrification inhibitors3,4-dimethylpyrazole phosphate (DMPP) on soil nitrogen transformation in different soils was investigated in a laboratory incubation experiment. During the incubation, soil pH and NH4+-N increased at the beginning of the experiment and then decreased, soil NO3--N and the apparent nitrification rate (ANR) increased throughout the incubation process. The concentration of NH4+-N and the soil pH were significantly higher in the treatments with DMPP compare to the urea-only treatment, which also possessed low concentration of NO3--N and low ANR. In the treatments of paddy soil and fluvo-aquic soil, nitrification was observed from the urea-only treatment until day14. After the addition of DMPP, this process was extended to28days. Nitrification was also found to be slower in black and red soils compare to paddy and fluvo-aquic soils, especially in red soil. The addition of DMPP affected the soil ANR, but this effect was found to be as strong in paddy and fluvo-aquic soils.The effect of the nitrification inhibitor3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated, at centimeter scale in a microcosm experiment under laboratory conditions. After28days samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from0to5cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH, NH4+-N and mineral N (NH4+-N, NO3--N and NO2--N) concentrations but decreased (NO3-+NO2O-)-N concentration and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis (DGGE) showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH4+-N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH4+-N concentrations and decreased AOB diversity from0to3cm but promoted diversity from3to5cm distance from the fertilizer zone. A phylogenetic analysis showed that the AOB communities were dominated by Nitrosospira cluster3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration.Nitrification was delayed due to the inhibitory effect on the reproduction of AOB when DMPP was applied. Although the addition of DMPP significantly decreased N02--N and N03"-N concentrations, and increased the soil pH and NH4+-N concentration, no significant effect was observed on the AOB community structure. Based on the RT-PCR results, the quantity of AOB was significantly lower in the DMPP treatments compared to the urea-only treatment.Compared to the urea-only treatment, no significant effect was observed on urea hydrolysis and the prosess of nitrate reduction to ammonium when the DMPP was added. There was no significant difference in the activity of soil urease, nitrate reductase, nitrite reductase and hydroxylamine reductase between different DMPP application rates.The addition of DMPP significantly reduced the emission of N2O and CO2compare to the urea-only treatment, however, ammonia volatilization was increased during the incubation period due to the high concentration of NH4+-N inside the soil. The same trends of N2O and CO2emissions were observed from different treatments of soil. In the urea-only treatment, N2O and CO2peak emissions were observed in the first week, whereas N2O and CO2peak emissions in the DMPP treatments occurred after20days of incubation. The cumulative emissions of N2O or CO2were significantly lower in the DMPP treatments compared to the urea-only treatment. There was no significant effect of DMPP application rate on ammonia volatilization. However, N2O and CO2emissions were increased when the DMPP application rate was lower than1%. Hence, we suggested that1%of N is the best application rate of DMPP.更多还原