氮肥减量配施生物炭对稻田有机碳矿化及酶活性影响

氮肥减量配施生物炭对于提升土地生产力、提高土壤碳汇能力以及缓解气候变暖具有重要意义。依托大田试验,设置5个氮肥用量梯度(T0～T4):100%化肥氮,90%化肥氮,80%化肥氮,70%化肥氮,60%化肥氮,采用等氮原则,氮肥减少量用等氮量生物炭替代,以不施肥为对照(CK),结合室内矿化培养,揭示稻田有机碳矿化及酶活性对氮肥减量配施生物炭的响应。结果表明:与T0处理相比,T3处理(70%化肥氮+7.5 t/hm~2生物炭氮)土壤全氮,碱解氮及速效磷依次显著提高了6.67%,8.36%及30.94%(P0.05),T4处理的速效钾含量最高,显著提高了23.78%(P0.05)。氮肥减量配施生物炭可有效提升土壤有机碳(SOC)含量,且随配施生物炭比例的增大而增大;与矿化前相比,各处理矿化后SOC,微生物量碳(MBC)及微生物熵(qMB)依次下降1.39～1.75 g/kg, 24.62～67.57 mg/kg及0.13%～0.32%(P0.05)。SOC矿化速率在培养的第1天达到峰值,第1阶段(第1～6天)迅速下降,第2阶段(第6～30天)缓慢下降,第3阶段(第30～45天)矿化速趋于平稳,矿化速率与培养时间呈对数函数关系(P0.01)。培养结束时SOC累积矿化量和累积矿化率的变化范围分别为1.39～1.75 g/kg和6.02%～8.43%,均以T3处理最低。与CK和T0处理相比,T3处理的过氧化氢酶、脲酶和蔗糖酶活性最高,T1处理的酸性磷酸酶活性最高。水稻产量以T3处理(7.37 t/hm~2)最高,比T0处理增产39.58%(P0.05)。综上,氮肥减量30%配施生物炭可明显提高土壤肥力,减少SOC矿化,增加土壤固碳,提高土壤酶活性及水稻产量。     

Fungal endophyte Phomopsis liquidambari B3 enriches the diversity of nodular culturable endophytic bacteria associated with continuous cropping of peanut

Previously, the application of the fungal endophyte Phomopsis liquidambari B3 exhibited notable effect in alleviating soil obstacles caused by continuous cropping of peanut. It was supposed that P. liquidambari B3 could enhance the efficiency of nodulation and nitrogen fixation by enriching the diversity of nodular endophytic bacteria under continous monocropping system. To verify this hypothesis, a pot experiment was conducted under natural conditions. Four treatments were set as follow: discontinuous cropping soil (NS), continuous cropping soil (CK), continuous cropping soil inoculate with actived P. liquidambari B3 (CSB3), and continuous cropping soil inoculate with sterilized P. liquidambari B3 (CSIB3). As a result, a total of 120 isolates were obtained. Our study clearly declared that the addition of fungal endophyte effectively enriched the genetic diversity and the community composition in CSB3. In contrast, a low genetic diversity level and simplex community structure were exhibited in CK and CSIB3. Meanwhile, the positive percentage rate and corresponding community composition of the plant growth-promoting isolates in NS and CSB3 were larger and more abundant than the other. This is the first time to describe the effects of fungal endophytes on the diversity of the nodular culturable endophytic bacteria associated with continuous cropping of peanut.     

电子鼻和电子舌单独与联合检测掺大豆蛋白或淀粉的鸡肉糜

为实现掺杂掺假鸡肉的快速、客观评价,该研究利用电子鼻和电子舌联合检测技术对掺杂鸡肉糜进行快速检测,通过对采集的数据进行主成分分析和偏最小二乘法分析,所得结果表明,采用主成分分析,电子鼻和电子舌联合检测掺大豆蛋白鸡肉糜和掺淀粉鸡肉糜的主成分总贡献率分别为99.8%和99.1%;采用偏最小二乘法分析,电子鼻和电子舌联合检测鸡肉糜中掺杂大豆蛋白含量的预测值与真实值之间的决定系数为0.992,均方根误差为2.8%;联合检测鸡肉糜中掺杂淀粉含量的预测值与真实值之间的决定系数为0.996,均方根误差为2.4%。表明电子鼻和电子舌联合检测对鸡肉糜的掺杂情况具有良好的区分和预测能力,并且是一种有效、高精度的肉类掺假检测方法。     

亚热带红壤区不同土地利用方式下的土壤剖面水流特征

以江西省鹰潭市的典型旱地、稻田和林地为研究对象,采用野外亮蓝染色示踪试验结合室内图像处理的方法,量化了各样地土壤剖面染色特征参数,明确了水流类型的剖面分布规律,并揭示了土壤理化性质对水流特征的影响机制。结果表明:染色面积比(SAR)随着土层深度的增加急剧降低,0—60 cm土层的平均SAR表现为稻田(28.16%)高于旱地(21.95%)和林地(18.64%),SAR差异主要体现在5—25 cm土层;染色路径数(SPN)随着土层深度的增加先增加后减小,整个剖面的平均SPN为稻田最多(20条),旱地其次(12条),林地最少(9条)。各样地0—20 cm土层染色路径宽度(SPW)均以1—10 cm为主,水流类型从上至下依次为均质流、非均质指流和高相互作用大孔隙流;对于20 cm以下土层,旱地和稻田的SPW以1 cm为主,水流类型分别以低相互作用大孔隙流和混合作用大孔隙流为主,林地以1—10 cm的SPW为主,主要水流类型为高相互作用大孔隙流。有机质含量、根系密度和土壤机械组成等性质影响了土壤的孔隙特征,进而影响了土壤的饱和导水率和水流特征。为提高红壤区的水分利用效率、减少水土流失,可以通过破除旱地犁底层、减少稻田干湿交替下的裂隙发育,以及增加林地植被多样性等多种方式实现。     

CT扫描分析秸秆隔层孔隙特征及其对土壤水入渗的影响

为阐明不同物理形态玉米秸秆建立的隔层对盐碱土壤灌溉水入渗特征的影响机制,该文采用室内模拟试验方法,在距地表40～45 cm处均匀铺设同一隔层厚度(5 cm)段状秸秆(SL)、颗粒状秸秆(SK)与粉末状秸秆(SF),以不埋设秸秆隔层为对照(CK),并利用CT扫描和图像处理技术,定量分析不同形态秸秆隔层内部孔隙度、孔隙大小分布、连通度等孔隙参数及其与灌溉水入渗特征之间的关系。结果表明:与CK处理相比,不同物理形态的玉米秸秆隔层均显著提高了40～45 cm隔层处总孔隙度,其中以SF处理最高,分别较CK、SL与SK处理显著提高了29.25、12.09与12.61个百分点(P 0.05),但SL与SK处理间差异不显著。SF处理在灌溉水入渗各阶段均显著增加了孔隙直径≤1 mm的孔隙度(P 0.05),入渗开始前、结束后分别较SL与SK处理提高了19.18、17.25和9.45、9.41个百分点,从而增大了封闭气体体积,导致灌溉水入渗速率较慢,而SL处理在灌溉水入渗开始前孔隙直径1 mm孔隙度较SK处理提高了1.04个百分点,但在入渗结束后SK处理孔隙直径1 mm孔隙度较SL处理显著提高,这种 1 mm大孔隙的变化导致SK处理出现湿润锋通过秸秆隔层耗时长于SL处理,而湿润锋通过隔层后至土柱底部耗时短于SL处理的现象。相关性分析结果表明:湿润锋通过秸秆隔层用时与入渗开始前、结束后隔层处总孔隙度、≤1 mm直径孔隙度均呈极显著正相关,与入渗前 1 mm直径孔隙度呈极显著负相关(P 0.01),而在入渗结束后这种大孔隙的作用减弱,但≤1 mm孔隙度的阻渗作用依旧显著,孔隙连通度对灌溉水入渗速率的影响较总孔隙度小。可见,不同形态玉米秸秆隔层均影响灌溉水入渗过程,CT扫描技术可作为定量研究秸秆隔层内部孔隙结构及其对灌溉水入渗影响机制的手段,该结果可为筛选和建立盐碱土壤最佳灌溉淋盐效果的物理形态秸秆隔层提供参考。     

发酵床垫料翻耙结合网床养殖改善鸭舍空气质量与鸭生产性能

为解决规模化肉鸭生产中粪污影响鸭健康和污染环境的问题,研发了一种发酵床结合网床架养新技术及其配套的可移动式网床下发酵床垫料翻耙系统,并研究了该模式在控制舍内气载微生物数量和提高鸭生产性能中的优势。结果显示:1)可移动式发酵床垫料翻耙系统实现不同发酵床体共用一台翻耙机。2)与发酵床平养相比,鸭26日龄之前未翻耙垫料时,发酵床网养舍内需氧菌总数(1.531×105 CFU/m3)和大肠杆菌数量(1.298×104 CFU/m3)显著升高(P0.05);鸭27~34日龄时每4 d翻耙垫料,发酵床网养舍内需氧菌总数(2.304×105 CFU/m3)和金黄色葡萄球菌数量(1.353×105 CFU/m3)显著降低(P0.05);鸭35~39日龄时每天翻耙垫料,发酵床网养舍内需氧菌总数(1.255×105 CFU/m3)和"沙门+志贺"氏菌数量(14.13 CFU/m3)显著降低(P0.05)。3)在发酵床平养舍内,与每4 d翻耙1次垫料相比,每天翻耙1次垫料舍内需氧菌总数(2.688×105 CFU/m3)、大肠杆菌(2.038×104 CFU/m3)、金黄色葡萄球菌(8.90×104 CFU/m3)和"沙门+志贺"氏菌(47.11 CFU/m3)数量显著(P0.05)降低,而在发酵床网养舍内,每天翻耙1次垫料舍内需氧菌总数(1.255×105 CFU/m3)和"沙门+志贺"氏菌(14.13 CFU/m3)数量显著降低(P0.05)。4)与发酵床平养相比,发酵床网养增加鸭体质量(P0.05),降低死亡率和上市淘汰率(P0.05)。结果表明研发的肉鸭养殖新模式能更好地减少舍内空气中病原菌浓度,改善鸭舍内空气环境,提高鸭生产性能。该研究为发酵床结合网床架养新模式在规模企业中推广应用提供技术支持。     

pH-dependent distribution of soil ammonia oxidizers across a large geographical scale as revealed by high-throughput pyrosequencing

Purpose

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) are ubiquitous and important for nitrogen transformations in terrestrial ecosystems. However, the distribution patterns of these microorganisms as affected by the terrestrial environments across a large geographical scale are not well understood. This study was designed to gain insights into the ecological characteristics of AOA and AOB in 65 soils, collected from a wide range of soil and ecosystem types.

Materials and methods

Barcoded pyrosequencing in combination with quantitative PCR was employed to characterize the relative abundance, diversity, and community composition of archaeal 16S rRNA gene, and AOA and AOB amoA genes in 65 soil samples.

Results and discussion

The operational taxonomic unit richness and Shannon diversity of Thaumarchaeota, AOA, and AOB were highly variable among different soils, but their variations were best explained by soil pH. Soil pH was strongly correlated with the overall community composition of ammonia oxidizers, as measured by the pairwise Bray–Curtis dissimilarity across all sites. These findings were further corroborated by the evident pH-dependent distribution patterns of four thaumarchaeal groups (I.1a-associated, I.1b, I.1c, and I.1c-associated) and four AOB clusters (2, 3a.1, 10, and 12). The ratios of AOA to AOB amoA gene copy numbers significantly decreased with increasing pH, suggesting a competitive advantage of AOA over AOB in acidic soils.

Conclusions

These results suggest that the distribution of ammonia oxidizers across large-scale biogeographical settings can be largely predicted along the soil pH gradient, thus providing important indications for the ecological characteristics of AOA and AOB in different soils.     

长期施肥对黄壤性水稻土有机碳矿化的影响

以贵州省农业科学院内黄壤性水稻土长期(22年)定位施肥试验为对象,采用室内模拟培养试验研究了不施肥(对照,CK)、施化肥(NPK)、低量有机无机肥配施(0.5MNPK)、施牛粪(M)和常量有机无机肥配施(MNPK)对土壤有机碳矿化的影响。结果表明:NPK处理土壤有机碳含量(21.6 g kg~(-1))与CK处理(22.8 g kg~(-1))基本相同,而0.5MNPK、M和MNPK处理的土壤有机碳含量较CK处理分别提高了30.6%、72.9%和62.2%,其中,M和MNPK处理差异达显著水平(p0.05)。模拟培养条件下,CO2产生速率在培养的第2天达到最大值,然后迅速下降,而后缓慢下降(第4~24天),后期(第24~30天)趋于稳定;各处理土壤有机碳矿化速率大小依次为:MMNPK0.5MNPKCKNPK,各处理土壤有机碳矿化速率随时间的动态变化均符合对数函数关系(p0.01)。培养结束(30 d)时,各处理土壤有机碳累积矿化量为1.23~2.37 g kg~(-1),以M处理和MNPK处理较高,较CK处理(1.46 g kg~(-1))分别增加了62.6%和44.2%(p0.05);各施肥处理土壤有机碳的累积矿化率(土壤有机碳累积矿化量/土壤有机碳含量)较CK处理(6.4%)均有所下降,以M处理和MNPK处理下降较多,降幅分别为1.2%和0.9%。土壤有机碳累积矿化量随培养天数的动态变化可以用一级动力学方程拟合(p0.01),模拟结果表明,CK处理土壤潜在可矿化有机碳量为1.55 g kg~(-1),与CK处理相比,NPK处理下降了11.6%,但差异不显著(p0.05),而有机肥处理(0.5MNPK、M和MNPK)有不同程度的提高(21.3%~73.6%),其中,M和MNPK处理提高幅度较大(p0.05);同时,MNPK处理能够提高土壤有机碳的周转速率,减少周转时间。上述结果指示黄壤性水稻土长期施用有机肥(0.5MNPK、M和MNPK)能够提高土壤有机碳的矿化速率,在促进土壤有机碳积累的同时降低其累积矿化率(单位有机碳矿化水平),增强土壤固碳能力。     

鱼稻共生条件下陶粒载体水稻浮床提高细菌活性及多样性

以轻质陶粒为主要原料开发出一种新型生物浮床载体,并通过种植水稻构建了陶粒载体水稻浮床对池塘水环境进行修复。研究了陶粒载体水稻浮床对精养池塘的水质净化作用,并采用Biolog-ECO技术分析了陶粒载体水稻浮床对池塘浮游细菌碳源代谢模式和多样性的影响。结果显示,试验组池塘水中总氮(TN)、总磷(TP)和亚硝态氮(NO2–-N)等水质指标在8月份显著低于对照组,高锰酸盐指数(IMn)在8月份和10月份显著低于对照组。试验组池塘浮游细菌群落代谢活性(AWCD)、Shannon指数和丰富度指数在8月份显著高于对照塘,Shannon均匀度指数在10月份显著高于对照塘。浮床种植水稻产量达到5 900 kg/hm~2。结果表明陶粒载体水稻浮床在具备一定生产性能基础上,降低了精养池塘水中氮磷营养水平,改变了精养池塘浮游细菌群落碳源利用模式,并提高了池塘浮游细菌群落代谢活性和功能多样性。结果可为应用陶粒载体水稻浮床调控池塘水环境提供理论指导。     

Effect of Assessment Scale on Spatial and Temporal Variations in CH4, CO2, and N2O Fluxes in a Forested Wetland

Emissions of methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) from a forested watershed (160 ha) in South Carolina, USA, were estimated with a spatially explicit watershed-scale modeling framework that utilizes the spatial variations in physical and biogeochemical characteristics across watersheds. The target watershed (WS80) consisting of wetland (23%) and upland (77%) was divided into 675 grid cells, and each of the cells had unique combination of vegetation, hydrology, soil properties, and topography. Driven by local climate, topography, soil, and vegetation conditions, MIKE SHE was used to generate daily flows as well as water table depth for each grid cell across the watershed. Forest-DNDC was then run for each cell to calculate its biogeochemistry including daily fluxes of the three greenhouse gases (GHGs). The simulated daily average CH₄, CO₂ and N₂O flux from the watershed were 17.9 mg C, 1.3 g C and 0.7 mg N m⁻², respectively, during the period from 2003–2007. The average contributions of the wetlands to the CH₄, CO₂ and N₂O emissions were about 95%, 20% and 18%, respectively. The spatial and temporal variation in the modeled CH₄, CO₂ and N₂O fluxes were large, and closely related to hydrological conditions. To understand the impact of spatial heterogeneity in physical and biogeochemical characteristics of the target watershed on GHG emissions, we used Forest-DNDC in a coarse mode (field scale), in which the entire watershed was set as a single simulated unit, where all hydrological, biogeochemical, and biophysical conditions were considered uniform. The results from the field-scale model differed from those modeled with the watershed-scale model which considered the spatial differences in physical and biogeochemical characteristics of the catchment. This contrast demonstrates that the spatially averaged topographic or biophysical conditions which are inherent with field-scale simulations could mask “hot spots” or small source areas with inherently high GHGs flux rates. The spatial resolution in conjunction with coupled hydrological and biogeochemical models could play a crucial role in reducing uncertainty of modeled GHG emissions from wetland-involved watersheds.