酸性土壤中度和高度稳定有机磷的分组研究

The fractionation of moderately and highly organic phosphorus (P_o) in acid soil was studied by two methods. By the first method, after incubation for 40 d, the mineralization rates of eight constituents of stable P_o in the soil were determined. By the second method, five constituents of precipitates of stable P_o in the soil were separated, then the five precipitates were put back into the original soils and incubated for 40 d and 60 d. Then, mineralization rates of the five precipitates were determined. The same results were obtained by the two methods. When the pH of the alkali solution containing stable P_o was adjusted from 3.00 to 3.10, the mineralization rate of moderately stable P_o was rapidly raised. Therefore, the pH 3.00 is the critical point between moderately and highly stable P_o.     

水氮耦合对设施农田土壤自养和异养硝化作用的影响

水氮措施影响设施土壤氮素的转化及硝化微生物活性,但水氮耦合对设施土壤自养和异养硝化作用差异的影响尚不明确。以连续8年设施水氮耦合田间定位试验土壤为研究对象,控制不同土壤田间持水量(WHC)(40%WHC、60%WHC和80% WHC)进行室内微宇宙培养试验,通过添加乙炔抑制剂抑制自养硝化途径,研究水氮耦合对设施土壤自养和异养硝化速率及参与自养硝化的氨氧化微生物的影响,分析氨氧化微生物氨氧化古细菌(AOA)和氨氧化细菌(AOB)对自养硝化作用的贡献。结果表明,水氮耦合下,不同硝化途径NH4+-N、NO^3--N含量以及参与自养硝化的AOA amoA和AOB amoA基因拷贝数均有显著差异。无乙炔培养7 d后,NO^3--N含量显著增加,而NH4+-N含量显著降低,AOA amoA和AOB amoA的基因丰度显著增加。添加乙炔后,NO^3--N、NH4+-N含量基本保持恒定,AOA amoA和AOB amoA基因丰度显著减少。水氮耦合显著影响自养和异养硝化速率,冗余分析(RDA)表明,NH4+-N含量、AOB amoA、NO^3--N-C2H2、AOA amoA可分别解释自养和异养硝化速率变异的68.9%、34.9%、32.8%和24.4%。设施土壤存在自养硝化和异养硝化两种途径,60%～80%WHC各施氮处理均以自养硝化为主,占总硝化速率的65%～86%;仅40%WHC下,氮纯养分量300和525 kg·hm-2处理以异养硝化为主,占总硝化速率的61%～77%。AOB和AOA共同驱动自养硝化,且AOB贡献更大。     

亚热带湿润地区城市公园重建强度对其土壤酸化和土壤中重金属的影响

Soil quality is a major concern in the management of urban parks. In this study, the soils at 0–3, 3–13, and 13–23 cm depths were sampled from six urban parks, differing in reconstruction intensity(mainly changes made during conversion of natural forests into parklands), in the Pearl River Delta, China to determine how reconstruction intensity influenced the extent of acidification and heavy metal levels in the soils of urban parks in a humid subtropical environment. High reconstruction intensity(HRI) was practiced in three parks and low reconstruction intensity(LRI) in three other parks. The LRI soils were strongly to extremely acidic(with low exchangeable Ca, Mg, and K concentrations) while the HRI soils were much less acidic. Both total and extractable concentrations of soil heavy metals were related to the specific management practices and age of the park, but did not differ significantly between LRI and HRI parks or among soil depths. Soil p H was significantly related to soil exchangeable cation concentrations and base saturation but was weakly related or unrelated to soil heavy metal levels. Our results suggest that high intensity but not low intensity reconstruction significantly reduces the extent of soil acidification in the urban parks in a humid subtropical environment.     

红壤侵蚀区马尾松林恢复过程中土壤异养呼吸及微生物多样性的变化特征

土壤异养呼吸是影响土壤有机碳积累的关键因素。以南方红壤水土流失区不同恢复年限的马尾松林（未治理地（Y0）、恢复14 a（Y14）、恢复31 a（Y31））为对象,对不同呼吸组分进行测定并结合温度、水分以及微生物等因子,研究马尾松林恢复对土壤异养呼吸的影响。结果表明：不同恢复年限马尾松林土壤异养呼吸差异显著,恢复31 a显著大于恢复14 a以及未治理地,未治理地异养呼吸速率仅为0.99 μmol?m-2?s-1,而治理14 a、31 a分别为2.20、2.80 μmol?m-2?s-1;温度是异养呼吸季节变化的主要影响因子,分别解释季节变化的40.6%（Y0）、62.2%（Y14）、66.6%（Y31）;马尾松林恢复后土壤异养呼吸温度敏感性（Q10）显著增加,Y0、Y14、Y31的 Q10分别为1.58、1.93和1.82;不同恢复年限土壤异养呼吸占土壤总呼吸比例为77.94%（Y0）、70.84%（Y14）、77.35%（Y31）。结构方程表明,在马尾松林恢复过程中,土壤有机碳（SOC）、温度以及土壤微生物多样性变化是影响土壤异养呼吸变化的主要因子,其中SOC、土壤微生物与异养呼吸显著正相关,而植被恢复过程中土壤温度变化与异养呼吸显著负相关。本研究结果表明,马尾松林植被恢复过程中SOC的积累以及缺乏有效的物理保护增加了微生物对SOC的分解,另一方面土壤环境温度的降低和细菌、真菌丰度的增加以及群落中变形菌、子囊菌、酸杆菌的增加,更进一步加剧微生物对原有土壤有机质的分解强度,导致异养呼吸碳排放的持续增加,最终限制了马尾松林土壤碳吸存效率。因此,较高的土壤异养呼吸可能是影响红壤侵蚀退化区土壤有机质进一步提升的关键。     

上海市土壤中持久性毒害污染物和盐分含量特征研究

Some farmland soils in Shanghai had high salinity levels, suggesting secondary salinization of the soils. The soil problems in Shanghai were studied, including the salinity and nitrate nitrogen (NO₃^--N) concentrations, heavy metal pollution characteristics, and organochlorine pesticide (OCP) residual levels and polycyclic aromatic hydrocarbon (PAH) contents. Accumulation of NO₃^--N in vegetable soils was the most significant among different functional soils. Heavy metal pollution was significant in the samples collected from the sewage-irrigated land and roadside. The identification of the metal sources through multivariate statistical analysis indicated that Pb, Zn, Cu and Cr in urban soils were from the traffic pollutants; excessive application of fertilizer and irrigation were the main reasons for the metal pollution in agricultural soils; Ni in the observed soils was controlled by parent soils. OCPs could still be detected in farmland soils but degraded greatly in last 20 years after prohibition of their usage. PAHs with 2-3 rings were the main components in industrial soils. The concentrated PAHs in the investigated soils were likely from petroleum and coal combustion.     

铜对土壤中功夫菊酯和氯氰菊酯迁移和扩散的影响

Repeated applications of bordeaux mixture （a blend of copper sulfate and calcium hydroxide） and pyrethroid insecticides （Pys） have led to elevated copper （Cu） and Pys concentrations in vineyard surface soils. To understand the potential influence of Cu on the fate of Pys in the soil environment, we selected two Pys, cypermethrin （CPM） and lambda-cyhalothrin （λ-CHT）, and two typical Chinese vineyard soils, Haplic Acrisol and Luvic Phaeozem, as experimental samples. The dissipation experiment was conducted at room temperature in the dark, and the transport of both Pys through the soils was investigated using soil thin-layer chromatography. The results showed that the transport of Pys in both soils increased as the Cu²⁺ concentration increased from 0 to 100 mg L^-1 , and Pys were more transportable in Haplic Acrisol （HA） than in Luvic Phaeozem （LP） under the same experimental conditions. For CPM, only 100 mg L^-1 of Cu²⁺ significantly （P<0.05） increased Pys transport through both soils relative to water. Lambda-CHT was significantly （P<0.05） transported through HA by all the Cu²⁺ concentrations compared to water, and all but the 1 mg L^-1 of Cu²⁺ significantly （P<0.05） increased the transport of λ-CHT through LP relative to water. However, the dissipation rates of CPM and λ-CHT decreased with the addition of Cu to soils. Our findings suggest that the risk of groundwater contamination by Pys increases in the soils with elevated Cu concentrations.     

对比景观土壤性质普通克里格法和回归克里格法的比较研究

The accuracy between ordinary kriging and regression kriging was compared based on the combined consideration of sample size, spatial structure, and auxiliary variables (terrain indices and electromagnetic induction surveys) for a variety of soil properties in two contrasting landscapes (agricultural vs. forested). When spatial structure could not be well captured by point-based observations (e. g., when the ratio of sample spacing over correlation range was > 0.5), or when a strong relationship existed between target soil properties and auxiliary variables (e. g., their R² was > 0.6), regression kriging (RK) was more accurate for interpolating soil properties in both landscapes studied. Otherwise, ordinary kriging (OK) was better. Soil depth and wetness condition did not appear to affect the selection of kriging for soil moisture interpolation, because they did not significantly change the ratio of sample spacing over correlation range and the relationship with the auxiliary variables. Because of a smaller ratio of elevation change over total study area (E/A = 1.2) and multiple parent materials in the agricultural land, OK was generally more accurate in that landscape. In contrast, a larger E/A ratio of 6.8 and a single parent material led to RK being preferable in the steep-sloped forested catchment. The results from this study can be useful for selecting kriging for various soil properties and landscapes.     

磷改良剂对中度和高度含碳酸盐的菜园土壤中Cd和Pb环境有效性和植物有效性的影响

The behaviour of metals mainly depends on soil p H, carbonate contents and contamination level, which should be considered for the management of contaminated soils. In this study, kitchen garden topsoils(0–25 cm) were sampled from the area around three smelters in France, with different Cd and Pb contamination levels. Effect of a phosphate amendment(a mixture of diammonium phosphate and hydroxyapatite) on the environmental availability and phytoavailability of Cd and Pb was evaluated by different chemical extractions and cultivating lettuce(Lactuca sativa L.), respectively. Changes in the distribution of Cd and Pb were found in most contaminated soils after phosphate amendment. An increase of Cd and Pb in the residual phase was highlighted in almost all carbonated contaminated soils, whereas a decrease of Pb in the exchangeable, water and acid-soluble phase was observed in most contaminated soils with the lowest carbonate contents. The concentrations of extractable Cd and Pb using calcium chloride and acetic and citric acids generally decreased after the soil amendment. Lettuces grown on amended soils were acceptable for human consumption as regard to Pb concentration. In contrast, some lettuces were unacceptable for human consumption, since the concentrations of Cd in the leaves were higher than the European legislation limit. Surprisingly, in carbonated soils with very low concentration of Cd, the Cd concentrations in lettuce reached up to the European legislation limit, making the lettuce unacceptable for human consumption.Our study highlighted the fact that the total metal concentration in soils does not always allow to predict the metal accumulation in the edible parts of vegetables in order to make a judgement about their acceptability or unacceptability for human consumption.     

中国西北干旱土壤中固定二氧化碳的RuBisCO基因丰度及其多样性研究

Arid soils where water and nutrients are scarce occupy over 30% of the Earth's total surface. However, the microbial autotrophy in the harsh environments remains largely unexplored. In this study, the abundance and diversity of autotrophic bacteria were investigated, by quantifying and profiling the large subunit genes of ribulose-1,5-bisphosphate carboxylase/oxygenase(Ru Bis CO) form I(cbb L) responsible for CO2 fixation, in the arid soils under three typical plant types(Haloxylon ammodendron, Cleistogenes chinensis,and Reaumuria soongorica) in Northwest China. The bacterial communities in the soils were also characterized using the 16 S r RNA gene. Abundance of red-like autotrophic bacteria ranged from 3.94 × 105 to 1.51 × 106 copies g-1dry soil and those of green-like autotrophic bacteria ranged from 1.15 × 106 to 2.08 × 106 copies g-1dry soil. Abundance of both red- and green-like autotrophic bacteria did not significantly differ among the soils under different plant types. The autotrophic bacteria identified with the cbb L gene primer were mainly affiliated with Alphaproteobacteria, Betaproteobacteria and an uncultured bacterial group, which were not detected in the 16 S r RNA library. In addition, 25.9% and 8.1% of the 16 S r RNA genes were affiliated with Cyanobacteria in the soils under H. ammodendron and R. soongorica, respectively. However, no Cyanobacteria-affiliated cbb L genes were detected in the same soils. The results suggested that microbial autotrophic CO2 fixation might be significant in the carbon cycling of arid soils, which warrants further exploration.     

从土壤中分离获得的五氯硝基苯降解菌株降解五氯硝基苯特性研究

A bacterial strain,pcnb-21,capable of degrading pentachloronitrobenzene(PCNB) under aerobic and anoxic conditions,was isolated from a long-term PCNB-polluted soil by an enrichment culture technique and identified as Labrys portucalensis based upon its morphological,physiological and biochemical properties,as well as 16S rRNA gene sequence analysis.Effects of different factors,such as temperature and pH,on PCNB biodegradation were studied.Strain pcnb-21 efficiently degraded PCNB at temperatures from 20 to 30 ℃ and initial pH values from 4 to 7,which might be the first time that a Labrys strain was found capable of efficiently degrading PCNB.The degradation of PCNB was affected by oxygen,and the degradation decreased with increasing aeration.Exogenous electron donors such as glucose,lactic acid and succinic acid promoted the biodegradation of PCNB,while electron acceptors such as sodium nitrite,sodium sulfate,sodium nitrate and sodium sulfate inhibited PCNB biodegradation.The degradation of PCNB in sterile and non-sterile soils by a green fluorescent protein(GFP)-labeled strain,pcnb-21-gfp,was also studied.Cells of pcnb-21-gfp efficiently degraded 100 mg kg -1 PCNB in sterile and non-sterile soils and could not be detected after 42 days.Strain pcnb-21 might be useful in bioremediating PCNB-polluted soils and environment.     

Organic nitrogen stimulates the heterotrophic nitrification rate in an acidic forest soil

Many previous studies have demonstrated that heterotrophic nitrification processes play an important role in the production of NO₃⁻ in acidic soils. However, it is not clear whether a low concentration of nitrogenous organic compounds support heterotrophic nitrification processes in natural soils. In this study, we performed an ¹⁵N tracer experiment with a glycine concentration gradient (20, 40, 80, and 160 mg N kg⁻¹) to investigate the effect of the organic nitrogen concentration on the heterotrophic nitrification rate and its relative contribution to the total nitrification of the studied acidic forest soil. This experiment demonstrated that ¹⁵N–NO₃⁻ accumulated over time with all nitrogen treatments in the presence of acetylene, confirming that heterotrophic nitrification occurred even at a low organic nitrogen concentration (20 mg kg⁻¹) in the studied acidic forest soil. In the presence of acetylene, the ¹⁵N–NO₃⁻ concentration in the 20 and 40 mg kg⁻¹ glycine-N treatments was significantly lower than in the 80 and 160 mg kg⁻¹ glycine-N treatments (p < 0.05), indicating that a high organic nitrogen concentration stimulated the heterotrophic nitrification rate. There was no significant difference in the average contribution of heterotrophic nitrification to total nitrification among the different nitrogen treatments, suggesting that the organic nitrogen concentration did not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil. Our results confirmed that a low concentration of organic N (20 mg kg⁻¹) supported heterotrophic nitrification in the studied soil. The organic nitrogen concentration stimulates the heterotrophic nitrification rate, but does not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil.     

Effect of labile and recalcitrant carbon on heterotrophic nitrification in a subtropical forest soil

Carbon (C) is an important factor controlling heterotrophic nitrification in soil, but the effect of individual C components (e.g., labile and recalcitrant C) is largely unclear. We carried out a C amendment experiment in which either labile C (glucose) or a recalcitrant C (cellulose and biochar) was added to a subtropical forest soil. A ¹⁵N-, ¹³C-tracing and MiSeq sequencing study was performed to investigate soil gross heterotrophic nitrification rates, carbon utilization for soil respiration and microbial biomass production and microbial composition, respectively. After 2 days, results showed a significant increase of gross heterotrophic nitrification rate in glucose (GLU) (on average 3.34 mg N kg⁻¹ day⁻¹), cellulose (CEL) (on average 0.21 mg N kg⁻¹ day⁻¹) and biochar (BIO) (on average 0.13 mg N kg⁻¹ day⁻¹) amendment in comparison with the unamended soil (CK) (on average 0.01 mg N kg⁻¹ day⁻¹; p < 0.05). The contribution of heterotrophic nitrification to total soil nitrification was significantly larger in GLU (average 85.86%), CEL (average 98.52%) and BIO (average 81.25%) treatments compared with CK (average 33.33%; p < 0.01). After 2-month amendment, the gross rates remarkably decreased in GLU (average 0.02 mg N kg⁻¹ day⁻¹), and the contribution to total nitrification (average 8.73%) were significantly lower than that in CK (p < 0.05). A decrease in the proportion of heterotrophic nitrification to total nitrification in soil was also observed in CEL (average 38.40%) and BIO (6.74%) treatments. Nevertheless, BIO amendment (compared to CK, GLU and CEL) showed the highest gross heterotrophic nitrification rate, accompanied by a notably higher abundance of specific heterotrophic nitrifiers, i.e. Trichoderma, Aspergillus and Penicillium. These results point to a stimulatory effect of C addition on soil heterotrophic nitrification in the short term, while the stimulatory impact of C amendment diminishes with the decline in easily available C. In addition, a shift of the microbial composition in the long term can possibly be sustained for longer if additional recalcitrant C is available to heterotrophic nitrifiers. The dynamic response of heterotrophic nitrification to labile and recalcitrant C in this study offered an explanation for the positive effect of plantation and plant root exudation on the process.     

土壤pH值和含水量对土壤硝化抑制剂效果的影响

硝化抑制剂如2-氯-6-三氯甲基吡nitrapyrin,通常与氮肥配施来抑制硝化作用提高农田中肥料的利用率,但是其抑制效果会受到土壤理化性质的影响。采用新工艺重新合成后的新型nitrapyrin纯度高达98%,由于杂质减少而具有更好的硝化抑制效果。为了研究土壤pH值和含水量对新型nitrapyrin抑制效果的影响,明确nitrapyrin适合施用的土壤条件,采用室内培养试验,研究了在不同的土壤pH值和含水量下nitrapyrin对无机氮含量动态变化和硝化作用强度的影响,以及其硝化抑制率的变化规律。结果表明:随着土壤pH值的升高,铵态氮含量降低,硝态氮含量和表观硝化率呈现上升的趋势,并且在所有pH值处理下氮肥配施nitrapyrin均显著地降低了矿质氮库铵态氮的转化量,均不同程度地抑制了硝化作用;在培养的第9天,nitrapyrin在pH值7.70处理下对硝化作用抑制效果最好,硝化抑制率达到91.53%,但硝化抑制率的降低速率在高pH值处理上更快;在培养的第45天,当pH值为4.66时,硝化抑制率为36.43%,显著高于其他处理;在整个培养过程中,施用nitrapyrin能显著抑制各处理的硝化作用,硝化抑制率在不同土壤含水量上的表现为:40%WHC60%WHC80%WHC。可见,nitrapyrin更加适合施用在酸性土壤以及旱地土壤上,该研究可以为新型硝化抑制剂nitrapyrin在农田中施用的最优条件提供理论依据。     

脲酶抑制剂与硝化抑制剂对稻田土壤硝化、反硝化功能菌的影响

[目的]在农业生产中,脲酶抑制剂(urease inhibitor,UI)与硝化抑制剂(nitrification inhibitor,NI)常作为氮肥增效剂来提高肥料利用率。本文研究了在我国南方红壤稻田施用脲酶抑制剂与硝化抑制剂后,土壤中氨氧化细菌(ammonia oxidizing bacteria,AOB)、氨氧化古菌(ammonia-oxidizing archaea,AOA)以及反硝化细菌的丰度以及群落结构的变化特征,旨在揭示抑制剂的作用机理及其对土壤环境的影响。[方法]试验在我国南方红壤稻田进行,共设5个处理:1)不施氮肥(CK);2)尿素(U);3)尿素+脲酶抑制剂(U+UI);4)尿素+硝化抑制剂(U+NI);5)尿素+脲酶抑制剂+硝化抑制剂(U+UI+NI),3次重复。脲酶抑制剂与硝化抑制剂分别为NBPT[N-(n-butyl)thiophosphrictriamide,N-丁基硫代磷酰三胺]和DMPP(3,4-dimethylpyrazole phosphate,3,4-二甲基吡唑磷酸盐)。通过荧光定量PCR(Real-time PCR)研究水稻分蘖期与孕穗期抑制剂对三类微生物标记基因拷贝数的影响,并分析土壤铵态氮、硝态氮与三种菌群丰度的相关性;利用变性梯度凝胶电泳(DenaturingGradient Gel Electrophoresis,DGGE)分析抑制剂对土壤AOB、AOA以及反硝化细菌群落结构的影响,并对优势菌群进行系统发育分析。[结果]1)荧光定量PCR结果表明,施用氮肥对两个时期土壤中AOB的amoA基因与反硝化细菌nirK基因的拷贝数均有显著提高,而对AOA的amoA基因始终没有明显影响;AOB与nirK反硝化细菌的丰度与两个时期的铵态氮含量、分蘖期的硝态氮含量呈极显著正相关,与孕穗期的硝态氮含量相关性不显著;DMPP仅在分蘖期显著减少了AOB的amoA基因拷贝数,表明DMPP主要通过限制AOB的生长来抑制稻田土壤硝化过程;NBPT对三类微生物的丰度无明显影响;2)DGGE图谱表明,在分蘖期与孕穗期,施用氮肥均明显增加了图谱中AOB的条带数,而对AOA却没有明显影响;氮肥明显增加了孕穗期反硝化细菌的条带数;与氮肥的影响相比,抑制剂NBPT与DMPP对AOA、AOB以及反硝化菌的群落结构影响甚微;系统发育分析结果表明,与土壤中AOB的优势菌群序列较为接近的有亚硝化单胞菌和亚硝化螺菌。[结论]在南方红壤稻田中,施入氮肥可显著提高AOB与反硝化细菌的丰度,明显影响两种菌群的群落结构,而AOA较为稳定;NBPT对三类微生物的群落结构丰度无明显影响;硝化抑制剂DMPP可抑制AOB的生长但仅表现在分蘖期,这可能是其缓解硝化反应的主要途径;这也说明二者对土壤生态环境均安全可靠。     

Fluctuations in the abundance of ammonia oxidizers and the contents of inorganic nitrogen in solarized soil

Solarization makes a great impact on the abundance of ammonia oxidizers and nitrifying activity in soil. To elucidate fluctuations in the abundance of ammonia oxidizers and nitrification in solarized soil, copy numbers of amoA gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA), viable number of ammonia oxidizers and inorganic nitrogen contents were investigated in greenhouse experiments. The copy number of amoA gene and the viable number of ammonia oxidizers were determined by the quantitative polymerase chain reaction and most probable number methods, respectively. Abundance of AOB based on the estimation of amoA gene copy numbers and viable counts of ammonia oxidizers was decreased by the solarization treatment and increased during the tomato (Solanum lycopersicum L.) cultivation period following the solarization. Effect of solarization on the copy number of amoA gene of AOA was less evident than that on AOB. The proportion of nitrate in inorganic nitrogen contents was declined by the solarization and increased during the tomato cultivation period following the solarization. Positive correlations were found between the proportion of nitrate in inorganic nitrogen content and the copy number of bacterial or archaeal amoA gene or the viable number of ammonia oxidizers; the copy number of bacterial amoA gene showed a strong correlation with the viable number of ammonia oxidizers. The present study revealed influences of solarization on the fluctuation in the abundance of ammonia oxidizers and dynamics of inorganic nitrogen contents in soil and the results indicate that the determination of amoA gene of AOB is possibly a quick and useful diagnostic technique for evaluating suppression and restoration of nitrification following solarization.     

水稻生育期内红壤稻田氨氧化微生物数量和硝化势的变化

利用荧光定量PCR(Real-timePCR)技术,通过特异引物检测amoA基因拷贝数分析了水稻不同生育期红壤稻田土壤中氨氧化细菌(Ammonia oxidizing bacteria,AOB)和氨氧化古菌(Ammonia oxidizing archaea,AOA)的数量变化,并测定了土壤潜在硝化势。结果显示:红壤稻田土壤中AOA数量显著高于AOB,二者比例在1.6～120.7之间;红壤稻田根层土中AOA数量显著高于表土,随水稻生长根层和表土中AOA数量均逐渐增加,且根层土中增加幅度更大;在水稻生长前期表土中AOB数量较多,孕穗期后根层土中AOB数量显著增加且高于表土。水稻生长期内土壤潜在硝化势也具有逐渐增加趋势,且根层土潜在硝化势增加幅度更大。根层土中潜在硝化势与AOB和AOA数量均呈显著正相关,而表土中潜在硝化势只与AOA数量存在显著正相关。研究表明,红壤稻田土壤中AOA数量更为丰富,且与硝化作用的关联程度更为密切,证实了氨氧化微生物在红壤稻田土壤微生物组成及其生态系统功能中的重要性。     

红壤稻田不同生育期土壤氨氧化微生物群落结构

以福建省红壤稻田土壤为对象,通过提取土壤总DNA,利用特异引物进行PCR(聚合酶链反应)扩增和DGGE(变性梯度凝胶电泳)并结合DNA克隆测序,研究了水稻生长过程中稻田土壤氨氧化细菌和氨氧化古菌群落结构的变化。结果显示:稻田土壤具有丰富的氨氧化细菌和氨氧化古菌资源。水稻生长过程中土壤氨氧化细菌群落组成较为稳定,只表现出水稻生长前期(苗期、分蘖期)和中后期(孕穗期、成熟期)间存在一定差异。而土壤氨氧化古菌群落组成变化较大,在水稻生长的苗期、分蘖期、孕穗期和成熟期4个时期间均存在一定差异。在水稻生长过程中,土壤氨氧化细菌群落多样性指数无显著性变化,但氨氧化古菌群落多样性指数随水稻生长明显提高,孕穗期后才达到平稳。水稻生长前期土壤硝化势也具有显著上升趋势,孕穗期时达到最高,而后有所下降。土壤硝化势与氨氧化古菌群落多样性指数具有显著正相关性,与氨氧化细菌没有相关性。研究表明,氨氧化古菌对红壤稻田土壤硝化作用的影响程度较大,证实了氨氧化微生物尤其是氨氧化古菌在稻田土壤微生物组成及其生态系统功能中的重要性。     

硝化抑制剂对春玉米氮素利用及土壤pH值和无机氮的影响

通过大田试验,研究了黑土区春玉米施用硝化抑制剂对土壤pH值、土壤铵态氮和硝态氮变化、硝化抑制率、产量及氮素利用率的影响。试验结果表明:硝化抑制剂处理中,混合物B的中水平添加量处理(B2)玉米产量较一次性全施肥处理(AF)能够增产且增产率最高,为5.60%,氮素利用率较追肥处理(TP)提高5.43%,硝化抑制作用和增产的效果明显;施用硝化抑制剂可使土壤pH值缓慢阶梯式下降;土壤含水率与土壤铵态氮含量呈负相关性(P0.01);土壤铵态氮含量与土壤pH值呈显著正相关;所选用的两种硝化抑制剂的配方中,B2和A3(混合物A的低水平添加量)处理的增产和硝化抑制效果最佳。     

长期施用含氯化肥对棕壤硝化作用及氨氧化微生物的影响

【目的】氨氧化微生物是氨氧化过程的主要驱动者,氨氧化过程作为硝化作用的限速步骤对氮循环具有重要作用。本研究以沈阳农业大学棕壤含氯化肥长期定位试验的土壤为研究对象,探讨了连续34年施用高氯和低氯化肥对棕壤硝化作用及氨氧化微生物的影响。【方法】该长期试验在等量氮、磷、钾条件下,设置高氯和低氯处理,共8个处理:T1(不施肥);T2(单施尿素);T3(尿素+氯化钾);T4(尿素+过磷酸钙);T5(尿素+过磷酸钙+氯化钾);T6(尿素+磷酸一铵+氯化钾);T7(尿素+氯磷铵+氯化钾);T8(硝酸磷肥+过磷酸钙+氯化钾),T7为高氯处理。采集0—20cm土壤样品,利用荧光定量PCR技术测定氨氧化细菌(AOB)和古菌(AOA)丰度,并结合土壤硝化潜势和基本化学性质,分析长期施用含氯化肥对棕壤硝化作用及氨氧化微生物丰度的影响及影响氨氧化微生物丰度的主要环境因素。【结果】长期施肥降低了土壤pH值,高氯处理降低得最多,显著低于其他处理;高氯处理的土壤硝化潜势也显著低于其他处理,且除高氯处理外,配施磷肥的处理土壤硝化潜势显著高于不施磷处理。各处理土壤中AOA丰度均显著高于AOB,高氯处理土壤中AOA、AOB丰度均显著低于其他处理,土壤硝化潜势与AOA和AOB均呈显著正相关关系。【结论】连续施用高氯化肥34年显著降低了棕壤AOA和AOB丰度,抑制了硝化潜势。该结果可为通过含氯化肥的合理施用来调节土壤AOA和AOB,进而调控土壤氮素循环提供参考。     

硝化/脲酶抑制剂对秋马铃薯植株及土壤氮素利用的影响

通过添加硝化/脲酶抑制剂达到秋马铃薯生产中减氮增效的目的,为制定秋马铃薯的农田氮素管理措施及节肥增效策略提供依据.采用随机区组试验设计,设置30、60、90、120 kg/hm24个施氮水平与硝化/脲酶抑制剂N-丁基硫代磷酰三胺(NBPT)、双氰胺(DCD)、2-氯-6-三氯甲基吡啶(CP)、未添加硝化/脲酶抑制剂(C...