【作者】 田波；

【导师】 蒋先军；

【作者基本信息】 西南大学 ， 土壤学， 2010， 硕士

【摘要】 土壤矿物质是组成土壤的最基本物质,它与其它因素结合决定着土壤的表面性质。土壤颗粒表面带有大量的负电荷,这样在土粒表面及附近溶液中形成一个“连续”分布的强大电场,对H+、NH4+和土壤微生物(带有负电荷)都产生影响,从而对硝化过程产生影响。在以前的研究中,人们较少考虑土壤颗粒表面电场的作用,本文从土壤颗粒表面不同电场强度的角度来研究土壤的微生物活性变化。本实验选用了重庆缙云山马尾松林土壤(酸性黄壤pH 5.2),在土样中加入3%、5%、8%、10%和12%浓度蒙脱石处理,风干、碾碎过1mm筛后待用。同时根据样品中由于加入蒙脱石引起的pH变化,制定了不同pH的样品。将两种样品调节含水率为田间最大持水量的50%,在25℃的恒温培养箱中先预培养一个月,土壤样品预培养一个月后,加入相当于干土重的100mg／kg含量的NH4+-N,加入NH4+-N后采样一次,然后土壤样品放置在25℃的恒温培养箱中培养,共培养4周每周采样1次。通过测定子样品的微生物生物量C和N,脲酶活性、脱氢酶活性,取得了如下实验结果。土壤颗粒表面不同电场强度下土壤微生物量的动态变化为：土壤颗粒表面不同电场下壤微生物C和微生物N随着培养时间的变化趋势相同,先增大后减小,在第14天时出现最大值。这是由于开始在土壤中加入一定量的NH4+-N后土壤的微生物活性增强,微生物生物量增大,但微生物的增大,同时NH4+-N量的减小,到了一定时间硝化细菌之间由于食物关系存在着竞争,这样微生物就会减少,微生物量自然会变小。通过28天后的变化,结束后微生物土壤颗粒表面不同电场强度下土壤微生物量的变化为随着土壤颗粒表面电场的增大,微生物量先增大后减小的变化趋势。在蒙脱石含量8%时为最大。由于土壤微生物的硝化细菌的大小在10-1000 nm之间,与土壤胶体颗粒相当并带一定负电荷,它们和土壤表面,土壤胶体颗粒间必然存在范德华作用力和静电作用力,所以硝化细菌的活性也受土壤颗粒表面电场影响较大。随着土壤颗粒表面电场强度的增大,对土壤硝化细菌先产生一定的吸引作用,当硝化细菌群落达到一定量时,微生物与土壤颗粒表面电场又会产生一定的吸引作用,造成土壤中微生物量的减少。这些推论还需要以后对微生物群落的测定来补充说明。土壤酶活性变化。土壤颗粒表面不同电场强度下土壤酶活性均有变化,其中土壤脲酶活性表现为：随着电场增大脲酶活性为先增大后减小,这与微生物量的变化趋势相同,也是由于NH4+-N的加入对其的影响,土壤脱氢酶均表现为：表面电场影响下脱氢酶活性趋近于一定的值为,为2.6mg·kg-1·d-1。脱氢酶的活性远远小于原样中的值,这说明,土壤处理过程中由于土壤磨细过筛,土壤的孔隙减小,影响土壤呼吸作用,而土壤脱氢酶与土壤的呼吸作用显著的正相关,所以脱氢酶显著变小。在对照试验中不同pH土壤样品,由于土壤pH的变化幅度小,各项指标变化不明显。在时间的动态变化上与不同表面电场的变化情况相同。培养结束后,比较28天后的数据,微生物量的变化为pH=5.20MBC为571 mg／kg pH=5.51为678 mg／kg pH=5.68为772 mg／kg pH=5.87为760 mg／kg pH=5.95为787 mg／kg pH=6.04 m为796 mg／kg,微生物量C随着pH的小幅增长在快速升高,pH在pH=5.20MBN为62mg／kg pH=5.51为68 mg／kg pH=5.68为74 mg／kgpH=5.87为75mg／kg pH=5.95为77mg／kg pH=6.04 m为82mg／kg,微生物量N随着pH的小幅增长在缓慢的增长。酶的活性变化为pH在5.20与6.04之间脲酶、脱氢酶活性没有很大差别。由上述结果可知,在土壤中加入不同浓度的蒙脱石,增大了土壤颗粒表面电场强度,由于土壤颗粒表面带有大量负电荷,随着负电荷密度的加大,对于本身带有负电荷的土壤微生物产生一定排斥作用,使土壤硝化微生物数量减少,出现这种结果的原因,除了土壤颗粒表面电场对微生物的影响外,还有就是在制备子样品过程中磨细过筛,使土壤微生物数量受到一定影响,破坏了微生物群落结构。此外,土壤颗粒本身的性质对土壤硝化作用产生一定影响,其中土壤有机质对土壤硝化细菌有抑制作用。由于土壤微生物受环境因素影响较为复杂,颗粒表面电场强度影响土壤微生物、硝化作用的具体程度,有待于进一步的研究。Ⅱ更多还原

【Abstract】 Soils mineral composition of the soil is the most basic materials, combined with other factors determine the nature of the soil surface. Since the surface of soil particles with a large amount of negative charge in solution near the soil particle surface and which form a"continuous" distribution of the strong electric field, on the H+,NH4+,and soil (with a negative charge) have an impact on the nitrification process. In previous studies, few people consider the role of electric field of the surface of soil particles; soil particles from the surface of this electric field strength of different angle of soil microbial activity.This experiment used the soil in Jinyun Mountain pine (Acid Yellow pH 5.2), in soil samples by adding 3%,5%,8%,10% and 12% concentration of montmorillonite treatment, air-dried, crushed through 1mm sieve to be use. At the same time according to the sample resulting from the incorporation of montmorillonite pH changes, thereby developing into samples of different pH. Regulate the two kinds of sample moisture content to 50% of the field moisture content, constant temperature incubator at 25℃in the first month of pre-culture, one month after pre-incubation of soil samples we added the equivalent weight of 100mg/kg dry soil NH4+ -N, NH4 +-N added after the sampling time, and then soil samples placed in the 25℃constant temperature incubator, samples were cultured once a weeks for 4 times Sub-samples were obtained by measuring microbial biomass C and N, urease activity, dehydrogenase activity, and achieved the following results.The surface of soil particles under different electric field strength changed the soil microbial biomass. Soil particle surface electric field under different soil microbial C and N had the same changes-first took an upward trend then decreased, with a maximum value at 14 days. The addition of a certain amount of NH4 +-N to the soil increased the soil microbial activity, increasing soil microbial biomass, but because micro-organisms increase and NH4 +-N decrease within a certain period of time the different kinds of nitrifying bacteria go into competition for food,thus reducing the amount of microbes which results in a reduction in microbial biomass as well.After 28 days, soil microbial biomass first took an upward trend then decreased with an increasing surface electric field of soil particles. As the surface electric field reaches -83.5*107 J/m·C microbial becomes the largest. As the soil of the nitrifying bacteria in the 10-1000 nm in size between the colloidal particles of soil take some considerable negative charge, soil colloidal particles must exist between the van der Waals force and electrostatic force, the nitrifying bacteria activity of the soil particle surface electric field by have a greater impact. As the soil particle surface electric field intensity, the soil nitrifying bacteria have certain attraction, when the community reaches a certain amount of nitrifying bacteria, the microbes and soil particle surface electric field will have a certain attraction, resulting in soil microbial biomass reduction. These inferences need the determination of the future of the microbial community to supplement.Soil enzyme activity:The surface of soil particles under different electric field strength changes in soil enzymatic activities in urease activity were as follows:When the electric field increases urease activity decreases for the first increase and then decrease afterwards, which is the same trend of microbial biomass, adding NH4 + -N to the soil impact. Soil dehydrogenase were as follows:dehydrogenase activity under the influence of surface electric field converge at same point, for the 2.6mg·kg-1·d-1. Dehydrogenase activity of treated sample is much less than that of the original sample, because of the soil treatment process including pulverizing,sieving, which decreased the soil porosity and respiration. Soil dehydrogenase and soil respiration had a significantly positive correlation., therefore dehydrogenase was significantly smaller.In the control test, soil samples at different pH of the index did not change significantly due to changes in low soil pH range. Dynamic changes in the time of surface electric field with the same changes, cultured after 28 days compared to data of microbial biomass in the pH=5.20MBC to 571 mg/ kg pH=5.51 to 678 mg/kg pH=5.68 to 772 mg/kg pH=5.87 to 760 mg/kg pH=5.95 to 787 mg/kg pH=6.04 m for the 796 mg/kg, microbial biomass C with the pH of the small growth in the fast-rising pH at pH=5.20MBN to 62mg/kg pH=5.51 to 68 mg/kg pH=5.68 to 74 mg/kg pH=5.87 to 75mg/kg pH=5.95 to 77mg/kg pH=6.04 m for the 82mg/kg, microbial biomass N increased slightly with pH, giving rise to slow growth. Between pH 5.20 and 6.04, urease, dehydrogenase activity are not very different.These results suggest that, in soils with different concentrations of montmorillonite, the surface of soil particles increases the electric field strength, due to the surface of soil particles with a large negative charge.Negative charge density increased, with a negative charge of the soil having a certain repulsion to reduce the number of soil microbial nitrification, in addition to the soil particle surface electric field on microorganisms. In the preparation of sub-samples of finely ground soil, microbial community structure is destroyed. In addition, natural soil particles have a certain impact on soil nitrification, in which soil organic matter on soil nitrifying bacteria was inhibited. Because soil is more complicated by environmental factors, soil particle surface electric field strength, the specific degree of nitrification, need further investigation.更多还原