不同有机肥源及其与化肥配施对稻田

比较了不同施肥方式对江苏金坛(31°39′41.8″ N, 119°28′23.5″ E)稻麦轮作体系下稻季土壤线虫群落结构的影响.试验共设CK(不施肥)、F(100%化肥)、PF(猪粪堆肥配施50%化肥)、SF(秸秆全量还田配施100%化肥)、PSF(猪粪堆肥和秸秆全量还田配施50%化肥)和PMF(猪粪商品有机无机复合肥)6个处理,在秋季水稻收获后进行采样.连续两年的试验结果表明: 线虫种群在不同处理和年份间存在变化.配施有机肥能够增加线虫总数,降低食细菌线虫的丰度,显著提高杂食/捕食性线虫的丰度;各处理食真菌线虫的丰度无显著差异;单施化肥和猪粪商品有机无机复合肥对植食性线虫的抑制作用不明显.第二年配施有机肥的食细菌线虫丰度较第一年相对提高,植食性线虫(潜根属Hirschmanniella)丰度相对降低.从土壤线虫生态学指数来看,配施有机肥处理第二年的土壤线虫多样性均显著提高,丰富度指数有上升的趋势,而线虫通路比值几乎没有变化.第二年瓦斯乐斯卡指数较第一年相对提高,而植食性线虫成熟指数相对降低.施用有机肥能够提高土壤食微线虫的丰度,使土壤环境趋于健康.     

Community Structure of Ammonia-Oxidizing Bacteria under Long-Term Application of Mineral Fertilizer and Organic Manure in a Sandy Loam Soil

The effects of mineral fertilizer (NPK) and organic manure on the community structure of soil ammonia-oxidizing bacteria (AOB) was investigated in a long-term (16-year) fertilizer experiment. The experiment included seven treatments: organic manure, half organic manure N plus half fertilizer N, fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and the control (without fertilization). N fertilization greatly increased soil nitrification potential, and mineral N fertilizer had a greater impact than organic manure, while N deficiency treatment (PK) had no significant effect. AOB community structure was analyzed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) of the amoA gene, which encodes the α subunit of ammonia monooxygenase. DGGE profiles showed that the AOB community was more diverse in N-fertilized treatments than in the PK-fertilized treatment or the control, while one dominant band observed in the control could not be detected in any of the fertilized treatments. Phylogenetic analysis showed that the DGGE bands derived from N-fertilized treatments belonged to Nitrosospira cluster 3, indicating that N fertilization resulted in the dominance of Nitrosospira cluster 3 in soil. These results demonstrate that long-term application of N fertilizers could result in increased soil nitrification potential and the AOB community shifts in soil. Our results also showed the different effects of mineral fertilizer N versus organic manure N; the effects of P and K on the soil AOB community; and the importance of balanced fertilization with N, P, and K in promoting nitrification functions in arable soils.     

Community structure of ammonia-oxidizing bacteria under long-term application of mineral fertilizer and organic manure in a sandy loam soil

The effects of mineral fertilizer (NPK) and organic manure on the community structure of soil ammonia-oxidizing bacteria (AOB) was investigated in a long-term (16-year) fertilizer experiment. The experiment included seven treatments: organic manure, half organic manure N plus half fertilizer N, fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and the control (without fertilization). N fertilization greatly increased soil nitrification potential, and mineral N fertilizer had a greater impact than organic manure, while N deficiency treatment (PK) had no significant effect. AOB community structure was analyzed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) of the amoA gene, which encodes the alpha subunit of ammonia monooxygenase. DGGE profiles showed that the AOB community was more diverse in N-fertilized treatments than in the PK-fertilized treatment or the control, while one dominant band observed in the control could not be detected in any of the fertilized treatments. Phylogenetic analysis showed that the DGGE bands derived from N-fertilized treatments belonged to Nitrosospira cluster 3, indicating that N fertilization resulted in the dominance of Nitrosospira cluster 3 in soil. These results demonstrate that long-term application of N fertilizers could result in increased soil nitrification potential and the AOB community shifts in soil. Our results also showed the different effects of mineral fertilizer N versus organic manure N; the effects of P and K on the soil AOB community; and the importance of balanced fertilization with N, P, and K in promoting nitrification functions in arable soils.     

Long-term effects of mineral versus organic fertilizers on activity and structure of the methanotrophic community in agricultural soils

Agricultural practices, such as mineral nitrogen fertilization, have an impact on the soil's ability to oxidize methane, but little is known about the shifts in the methanotrophic community composition associated with these practices. Therefore, the long-term effect of both mineral (NH4NO3) and organic (manure and GFT-compost) fertilizer applications on the soil methanotrophic community activity and structure were investigated. Both high and low affinity methane oxidation rates were lower in the soil treated with mineral fertilizer compared to the other soils. An enhanced nitrate concentration was observed in the mineral fertilized soil but nitrate did not show a direct affect on the high affinity methane oxidation. In contrast, the low affinity methane oxidation was slowed down by increased nitrate concentrations, which suggests a direct effect of nitrate on low affinity methane oxidation. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments specific for methanotrophs revealed a distinct community between the mineral and organic fertilized soils as extra Type I methanotrophic bands (phylotypes) became visible in the organic fertilized soils. These phylotypes were not visible in the patterns of the added organic fertilizers suggesting an indirect effect of the organic fertilizers on the methanotrophic community. Additionally, a molecular analysis was performed after the low affinity methane oxidation test. The enhanced methane concentrations used in the test enriched certain low affinity methanotrophs in the organic fertilized soils but not in the mineral fertilized soil. Supporting the molecular and functional observations, fatty acids characteristic for methanotrophs were less abundant in the soil treated with mineral fertilizer compared to the soil treated with compost. In conclusion, the function and molecular and chemical composition of the methanotrophic community are all altered in soil fertilized with mineral fertilizer.     

Co-composting of oil exhausted olive-cake, poultry manure and industrial residues of agro-food activity for soil amendment

The co-composting of exhausted olive-cake with poultry manure and sesame shells was investigated. These organic solid wastes were watered by the confectionary wastewater which is characterized by its high content of residual sugars raising its COD. Four aerated windrows were performed to establish the effects of confectionary by-products on the compost process. Different mixtures of the agro-industrial wastes were used. During the composting process, physico-chemical parameters (temperature, moisture, pH, electrical conductivity, total carbon and total nitrogen) were studied. The stability of the biological system was noticed after 70 days. The final products were characterized by their relatively high organic matter content, and low C/N ratio of 14-17. The humidification of the windrows with the wastewater seemed to have accelerated the composting process in comparison to a windrow humidified with water. In addition, the organic matter degradation was enhanced to reach 55-70%. The application of the obtained composts to soil appeared to significantly improve the soil fertility. Indeed, field experiments showed an increase in potato yield; the production was 30.5-37.5 tons ha(-1), compared to 30.5 tons ha(-1) with farm manure.     

不同施肥模式对雷竹林土壤真菌群落特征的影响

为探明施肥处理对雷竹林土壤真菌群落特征的影响,采用末端限制性片段长度多态性(T-RFLP)和荧光定量PCR技术,分析有机肥(M)、化肥(CF)、化肥配施有机肥(CFM)、化肥配施有机肥加覆盖(CFMM)及不施肥(CK)处理土壤真菌群落结构和数量特征.结果表明:施肥显著影响真菌群落结构与多样性,表层(0～20 cm)土壤中M、CFMM处理与CK,亚表层(20～40 cm)土壤中CF、CFMM处理与CK之间真菌群落结构均存在明显差异;且表层土壤中CF、CFMM处理真菌Shannon指数和均匀度指数显著低于CK.M、CFM处理表层土壤真菌数量显著高于CK.土壤有机质、全氮、铵态氮和速效钾含量显著影响了真菌群落结构的变异;全氮、铵态氮、硝态氮含量与真菌数量均呈显著正相关.表明雷竹林表层和亚表层土壤中真菌群落对施肥处理的响应存在明显差异,表层土壤真菌群落明显受有机质添加的影响,而亚表层则对化肥投入较为敏感;施肥对真菌群落多样性的影响主要集中在表层土壤.     

Traditional cattle manure application determines abundance, diversity and activity of methanogenic Archaea in arable European soil

Based on lipid analyses, 16S rRNA/rRNA gene single-strand conformation polymorphism fingerprints and methane flux measurements, influences of the fertilization regime on abundance and diversity of archaeal communities were investigated in soil samples from the long-term (103 years) field trial in Bad Lauchst?dt, Germany. The investigated plots followed a gradient of increasing fertilization beginning at no fertilization and ending at the 'cattle manure' itself. The archaeal phospholipid etherlipid (PLEL) concentration was used as an indicator for archaeal biomass and increased with the gradient of increasing fertilization, whereby the concentrations determined for organically fertilized soils were well above previously reported values. Methane emission, although at a low level, were occasionally only observed in organically fertilized soils, whereas the other treatments showed significant methane uptake. Euryarchaeotal organisms were abundant in all investigated samples but 16S rRNA analysis also demonstrated the presence of Crenarchaeota in fertilized soils. Lowest molecular archaeal diversity was found in highest fertilized treatments. Archaea phylogenetically most closely related to cultured methanogens were abundant in these fertilized soils, whereas Archaea with low relatedness to cultured microorganisms dominated in non-fertilized soils. Relatives of Methanoculleus spp. were found almost exclusively in organically fertilized soils or cattle manure. Methanosarcina-related microorganisms were detected in all soils as well as in the cattle manure, but soils with highest organic application rate were specifically dominated by a close phylogenetic relative of Methanosarcina thermophila. Our findings suggest that regular application of cattle manure increased archaeal biomass, but reduced archaeal diversity and selected for methanogenic Methanoculleus and Methanosarcina strains, leading to the circumstance that high organic fertilized soils did not function as a methane sink at the investigated site anymore.     

Fungi Benefit from Two Decades of Increased Nutrient Availability in Tundra Heath Soil

If microbial degradation of carbon substrates in arctic soil is stimulated by climatic warming, this would be a significant positive feedback on global change. With data from a climate change experiment in Northern Sweden we show that warming and enhanced soil nutrient availability, which is a predicted long-term consequence of climatic warming and mimicked by fertilization, both increase soil microbial biomass. However, while fertilization increased the relative abundance of fungi, warming caused only a minimal shift in the microbial community composition based on the phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) profiles. The function of the microbial community was also differently affected, as indicated by stable isotope probing of PLFA and NLFA. We demonstrate that two decades of fertilization have favored fungi relative to bacteria, and increased the turnover of complex organic compounds such as vanillin, while warming has had no such effects. Furthermore, the NLFA-to-PLFA ratio for ¹³C-incorporation from acetate increased in warmed plots but not in fertilized ones. Thus, fertilization cannot be used as a proxy for effects on warming in arctic tundra soils. Furthermore, the different functional responses suggest that the biomass increase found in both fertilized and warmed plots was mediated via different mechanisms.     

Relative effectiveness of various types and methods of zinc application on rice and maize crops grown in calcareous soil

Summary Application of zinc sulphate mixed with compost/poultry manure proved to be equivalent to the effect of dipping the seedling roots in 4% ZnO suspension with respect to rice yields but Zn-amended organic manures were superior to other treatments with regards to total Zn uptake. A marked residual effect of soil applied treatments was recorded on the succeeding maize crop. Application of poultry manure alone was about one and a half times more effective than compost alone in increasing the rice and maize grain yields. Poultry manure surpassed compost in increasing zinc uptake by the crops and at the same time it built up more available Zn in soil than compost for the following crop. The magnitude of yields and Zn uptake response were magnified when zinc sulphate was applied along with organic manures. Application of 25 kg zinc sulphate/ha alone had the same effect as 50 quintals poultry manure alone or 12.5 kg zinc sulphate applied with 50 quintals compost/ha with respect to crop yields. A significant positive correlation was, recorded in both the crops between Zn concentration in grain or straw and their respective yields.     

Organic matter components and aggregate stability after the application of different amendments to a horticultural soil

The effects of usual or recommended rates of application of five organic amendments (24 t/ha yr of MSW compost, sewage sludge, and ovine manure, 2.4 t/ha yr of commercial vermicompost, and 100 l/ha yr of a commercial humic acids solution) on the soil contents of organic matter, total humified substances, humic acids, carbohydrates and microbial gums, and the structural stability of aggregates were investigated. Four and five years after the beginning of the experiment, significant increments in most of the parameters studied were found after the application of organic residues, whereas the two commercial amendments did not produce any significant change, suggesting that rates recommended by the producers and imposed by their high prices are too low to be useful. MSW compost yielded the highest increases, even if the amount of organic matter applied as ovine manure was very similar. Organic matter and carbohydrates appeared to be the parameters most closely related to soil aggregate stability.     

The effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cycling

Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surface soil (0-5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Long-term Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function.     

Fertilization alters the abundance but not the diversity of soil fauna: A meta-analysis

Aim

Soil fauna, a functionally important group of soil organisms, are greatly affected by fertilization. However, it is still debated whether and how fertilization affects the soil faunal community. Here, we aimed to synthesize the global patterns of soil fauna communities in response to fertilization in terrestrial ecosystems.

Location

Global.

Time period

1997–2021.

Major taxa studied

Soil fauna.

Methods

We examined the effects of fertilization on the abundance, number of groups and Shannon diversity of soil fauna by synthesizing 1218 observations based on 39 published studies. We also explored the associations between fertilization-induced changes in the soil faunal community and changes in soil and microbial properties.

Results

Fertilization increased the abundance of soil fauna by 56.3%, without significantly affecting the number of groups and the Shannon index. The type of fertilizer affected the responses of soil faunal abundance, and the effects of fertilizer type were altered by climate zones, ecosystem types and soil depths. Both organic and organic–mineral fertilizer treatments significantly increased the abundance of soil fauna in most climate zones, ecosystem types and soil depths, whereas mineral fertilizer treatment had no such effect. Additionally, we found inconsistent responses of soil fauna to fertilization among different taxonomic groups, not only at the order level but also at the class level, providing evidence for the idiosyncratic nature of the effects of fertilization on soil fauna. Furthermore, our regression analysis showed that changes in food resources, including soil nutrients and microbes, were crucial controls for the response of soil faunal abundance to fertilization.

Main conclusions

Fertilization generally increased soil faunal abundance at the global scale by affecting food resources, and the effects of fertilization were dependent on the specific soil fauna and type of fertilizer. We suggest the use of organic or organic–mineral fertilizers, rather than mineral fertilizers, to increase the benefits on specific soil fauna.     

长期施肥对土壤氨氧化微生物的影响

长期施肥可改变土壤碳氮等养分供应,进而影响微生物数量与群落组成。本研究基于棕壤长期定位实验站,分析不同施肥方式下(不施肥,CK;低量无机氮肥,N₂;高量无机氮肥,N₄;有机无机氮肥配施,M₂N₂)土壤氨氧化古菌(AOA)和细菌(AOB)的变化,为土壤氮素转化的微生物学机制和培肥土壤提供依据。结果表明:不同施肥方式下,土壤AOA与AOB的数量比值为2.28～61.95。与CK相比,施肥后土壤AOA数量降低了1.6%～13.6%。N₄处理AOB数量随土壤深度增加呈先降低后升高的趋势,其他处理则相反。土壤AOB群落Shannon多样性指数、均匀度指数和Simpson指数均高于AOA。M₂N₂处理0～20 cm土层土壤AOB多样性增加,但AOA多样性降低。土壤AOB主要因土壤深度发生聚类,AOB和AOA均未因施肥方式发生聚类。综上,长期施肥改变了土壤AOA和AOB的构成状况,AOA对环境变化较为敏感,AOB较为丰富和稳定。     

免耕覆盖及有机肥施用对土壤真菌群落组成及多样性的影响

为揭示土壤真菌群落对免耕、覆盖及有机肥施用的响应机制,在宁夏南部山区冬小麦农田连续3年采用免耕覆盖+施有机肥(NF)、免耕覆盖+不施有机肥(NC)、传统耕作不覆盖+施有机肥(TF)和传统耕作不覆盖+不施有机肥(TC)4个处理,依托Illumina MiSeq 高通量测序平台,研究了土壤真菌群落组成、多样性及其与土壤环境因子间的关系。结果表明: 4个处理共获得3490个可操作分类单元(OTUs),其中含有一些未知真菌。在已知的真菌群落中,子囊菌门和担子菌门为优势菌门,其相对丰度占总丰度的82.1%～94.2%,且TF处理下子囊菌门座囊菌纲的相对丰度最高,NF处理下担子菌门银耳菌纲的相对丰度最高。4个处理真菌群落多样性指数(Shannon和Simpson指数)依次为NC>TC>NF>TF。多元分析结果表明,微生物生物量碳是影响担子菌门和接合菌门相对丰度的主要因素,而土壤全磷、速效钾和速效磷含量高低是驱动子囊菌门真菌相对丰度变化的关键因素。在宁夏南部山区推广以免耕覆盖并施用有机肥的保护性耕作措施有利于提高土壤真菌群落多样性。     

不同有机废弃物改良新复垦耕地的综合效果评价

由废弃地整理复垦形成的耕地存在土壤有机质和有效养分低、土壤板结、微生物活性弱和土壤耕作性状不良等问题,快速、有效地提高土壤肥力质量是全面提升该类耕地质量和生产性能的重要组成部分.本文通过田间小区试验研究了城郊有机废弃物对新复垦耕地土壤培肥的综合效果,并比较了不同类型城郊有机废弃物在培育耕地质量方面的差异.试验设置了施用等量猪粪、鸡粪、水稻秸秆、蔬菜收获残留物、城市污泥、沼渣、猪粪/水稻秸秆堆肥、生活垃圾堆肥和对照（不施有机肥）9个处理（年用量30 t·hm^-2）,连续进行3年的定点试验.结果表明： 施用任何有机物对改善土壤肥力均有明显的作用.其中,提升土壤碳库管理指数以施用猪粪、鸡粪、猪粪/水稻秸秆堆肥、水稻秸秆和沼渣的效果最为显著;增加土壤水稳定性团聚体和降低土壤容重以施用猪粪/水稻秸秆堆肥和沼渣的效果最佳;施用污泥、猪粪/水稻秸秆堆肥和生活垃圾堆肥可增强土壤保蓄能力;施用猪粪、鸡粪和猪粪/水稻秸秆堆肥对增加土壤有效态养分的效果最为明显;各类有机物均显著提高了土壤微生物数量和酶活性.长期施用污泥、生活垃圾堆肥及畜禽粪存在着土壤重金属污染的风险,但短期施用对土壤环境质量影响不明显.总体上,对土壤肥力的改善效果由大至小依次为：猪粪/水稻秸秆堆肥>鸡粪>猪粪>沼渣>生活垃圾堆肥>水稻秸秆>城市污泥>蔬菜收获残留物;对土壤的相对污染程度由大至小为：城市污泥>生活垃圾堆肥>猪粪>鸡粪>沼渣>猪粪/水稻秸秆堆肥>蔬菜收获残留物>水稻秸秆.     

长期不同施肥措施下岩溶水稻土可培养细菌群落变化及其主要影响因素

【背景】施肥是目前提高作物产量的较优策略,不同的施肥措施在不同程度上影响土壤肥力和微生物群落结构。【目的】探究岩溶水稻土理化性质变化与细菌群落变化的对应关系,进而反映不同施肥措施对土壤可培养细菌群落的影响。最后选出最优施肥方案,为后续的合理施肥工作提供依据。【方法】对岩溶水稻土进行不施肥、常规施肥、常规施肥加绿肥3种施肥处理,通过对土壤理化性质、可培养细菌群落丰度及多样性变化的研究,探究在不同施肥措施下对岩溶水稻土壤细菌群落的影响。【结果】对比不施肥处理,常规施肥处理下土壤pH值和有机碳含量下降,结合大量研究结果证明,无机肥或氮肥的长期过量施加使土壤pH值下降,常规施肥加绿肥有利于有机碳的积累。分离纯化共得到164株菌,分别来自Actinobacteria、Bacteroidetes、Firmicutes和Proteobacteria。属水平上常规施肥配施绿肥较常规施肥组优势菌属Sphingomonas、Lysobacter的相对丰度增加。细菌群落多样性增加,出现Paenibacillus、Streptomyces和Pseudomonas等特有功能菌属。优势菌属Sphingopyxis、Lysobacter、Paenibacillus、Bosea、Streptomyces、Pseudomonas和Bacillus与TN存在显著正相关,在常规施肥加绿肥处理土壤中增加。【结论】常规施肥加绿肥处理下,固氮、溶磷等功能菌丰度增加,增加土壤肥力,保持土壤养分的可利用性,对作物的增产起重要作用。岩溶水稻土常规施肥配施绿肥处理的效果优于不施肥和常规施肥处理。     

长期施肥对水稻土有机碳分布及化学结合形态的影响

采用湖南省4个23年连续施肥的稻田长期定位试验,研究了施肥对湖南省水稻土有机碳分布及化学键合形态的影响。试验设不施肥(CK)、化肥(NPK)、中量有机肥(MOM)和高量有机肥(HOM)4个处理。结果表明:在所有施肥处理中,水稳性团聚体均以0.25～1mm和2～5mm粒径含量最高,分别达全土总量的18%～43%和13%～48%。中、高量有机肥处理显著增加了>1mm大团聚体含量以及有机碳在大团聚体中的分配,其中0.25～1mm和1～2mm粒径团聚体中有机碳含量均略高于其余粒径组。与不施肥比较,钙结合态有机碳(Ca-SOC)占总有机碳的比例在2%～4%左右且随有机肥施用呈下降趋势,而铁铝结合态有机碳Fe(Al)-SOC占总有机碳的18%～33%呈上升趋势。有机肥施用条件下,有机碳在大团聚体中的分布的增加、Fe(Al)-SOC的提升以及Ca-SOC的降低意味着土壤有机碳物理和化学保护作用的增强,有利于稻田土壤有机碳的积累,是有机肥施用条件下保持稻田土壤较高固碳速率的重要原因。     

Microbial activity and soil respiration under nitrogen addition in Alaskan boreal forest

Climate warming could increase rates of soil organic matter turnover and nutrient mineralization, particularly in northern high‐latitude ecosystems. However, the effects of increasing nutrient availability on microbial processes in these ecosystems are poorly understood. To determine how soil microbes respond to nutrient enrichment, we measured microbial biomass, extracellular enzyme activities, soil respiration, and the community composition of active fungi in nitrogen (N) fertilized soils of a boreal forest in central Alaska. We predicted that N addition would suppress fungal activity relative to bacteria, but stimulate carbon (C)‐degrading enzyme activities and soil respiration. Instead, we found no evidence for a suppression of fungal activity, although fungal sporocarp production declined significantly, and the relative abundance of two fungal taxa changed dramatically with N fertilization. Microbial biomass as measured by chloroform fumigation did not respond to fertilization, nor did the ratio of fungi : bacteria as measured by quantitative polymerase chain reaction. However, microbial biomass C : N ratios narrowed significantly from 16.0 ± 1.4 to 5.2 ± 0.3 with fertilization. N fertilization significantly increased the activity of a cellulose‐degrading enzyme and suppressed the activities of protein‐ and chitin‐degrading enzymes but had no effect on soil respiration rates or ¹⁴C signatures. These results indicate that N fertilization alters microbial community composition and allocation to extracellular enzyme production without affecting soil respiration. Thus, our results do not provide evidence for strong microbial feedbacks to the boreal C cycle under climate warming or N addition. However, organic N cycling may decline due to a reduction in the activity of enzymes that target nitrogenous compounds.     

Impacts of organic and inorganic fertilizers on nitrification in a cold climate soil are linked to the bacterial ammonia oxidizer community

The microbiology underpinning soil nitrogen cycling in northeast China remains poorly understood. These agricultural systems are typified by widely contrasting temperature, ranging from −40 to 38°C. In a long-term site in this region, the impacts of mineral and organic fertilizer amendments on potential nitrification rate (PNR) were determined. PNR was found to be suppressed by long-term mineral fertilizer treatment but enhanced by manure treatment. The abundance and structure of ammonia-oxidizing bacterial (AOB) and archaeal (AOA) communities were assessed using quantitative polymerase chain reaction and denaturing gradient gel electrophoresis techniques. The abundance of AOA was reduced by all fertilizer treatments, while the opposite response was measured for AOB, leading to a six- to 60-fold reduction in AOA/AOB ratio. The community structure of AOA exhibited little variation across fertilization treatments, whereas the structure of the AOB community was highly responsive. PNR was correlated with community structure of AOB rather than that of AOA. Variation in the community structure of AOB was linked to soil pH, total carbon, and nitrogen contents induced by different long-term fertilization regimes. The results suggest that manure amendment establishes conditions which select for an AOB community type which recovers mineral fertilizer-suppressed soil nitrification.     

Changes in Bacterial and Fungal Communities across Compost Recipes,Preparation Methods,and Composting Times

Compost production is a critical component of organic waste handling, and compost applications to soil are increasingly important to crop production. However, we know surprisingly little about the microbial communities involved in the composting process and the factors shaping compost microbial dynamics. Here, we used high-throughput sequencing approaches to assess the diversity and composition of both bacterial and fungal communities in compost produced at a commercial-scale. Bacterial and fungal communities responded to both compost recipe and composting method. Specifically, bacterial communities in manure and hay recipes contained greater relative abundances of Firmicutes than hardwood recipes with hay recipes containing relatively more Actinobacteria and Gemmatimonadetes. In contrast, hardwood recipes contained a large relative abundance of Acidobacteria and Chloroflexi. Fungal communities of compost from a mixture of dairy manure and silage-based bedding were distinguished by a greater relative abundance of Pezizomycetes and Microascales. Hay recipes uniquely contained abundant Epicoccum, Thermomyces, Eurotium, Arthrobotrys, and Myriococcum. Hardwood recipes contained relatively abundant Sordariomycetes. Holding recipe constant, there were significantly different bacterial and fungal communities when the composting process was managed by windrow, aerated static pile, or vermicompost. Temporal dynamics of the composting process followed known patterns of degradative succession in herbivore manure. The initial community was dominated by Phycomycetes, followed by Ascomycota and finally Basidiomycota. Zygomycota were associated more with manure-silage and hay than hardwood composts. Most commercial composters focus on the thermophilic phase as an economic means to insure sanitation of compost from pathogens. However, the community succeeding the thermophilic phase begs further investigation to determine how the microbial dynamics observed here can be best managed to generate compost with the desired properties.