长期施肥对黄土旱塬农田土壤微生物丰度的影响

以长武黄土高原农业生态试验站的长期定位试验为平台,通过荧光实时定量PCR (real-time PCR) 技术,研究不同施肥制度下的黄土旱塬农田土壤微生物群落丰度,揭示长期不同施肥制度对土壤微生物群落的影响规律.结果表明: 单施化肥处理细菌数量较CK裸地增加21％,古菌增加32％;化肥配施有机肥处理细菌数量增加37％,古菌数量增加36％.化肥配施有机肥处理显著增加了土壤细菌和古菌的丰度.30年长期施氮肥处理导致氨氧化细菌(AOB)的增幅达7.13倍,而氨氧化古菌(AOA)的增幅仅为0.2倍.AOB对施肥的响应程度较高,尤其是对氮肥具有较高的敏感性.与单施氮肥和氮肥混施有机肥处理相比,施磷肥处理显著增加了固氮酶铁蛋白和甲烷氧化菌含量,撂荒地的固氮酶铁蛋白、亚硝酸还原酶和甲烷氧化菌含量显著高于耕作土壤.结合土壤基本理化性质的相关性分析结果,pH、全氮和有机碳含量是影响土壤微生物群落丰度的重要因子.总之,长期施肥显著改变了黄土旱塬农田土壤各微生物丰度,不同施肥模式、耕作方式对微生物群落丰度具有显著影响.     

不同施肥制度土壤微生物量碳氮变化及细菌群落16S rDNA V3 片段PCR产物的DGGE分析

应用化学分析和变性梯度凝胶电泳（DGGE）技术分离PCR扩增的16S rDNA的方法,研究了不同施肥制度对土壤微生物量碳、氮变化及微生物多样性的影响。结果表明,连续15a长期试验下,土壤微生物量碳（SMB-C）和微生物量氮（SMB-N）的含量大小均为长期撂荒（CK0）土壤高于农田土壤,而在农田土壤中,长期施肥的处理（NPK、NPKM、NPKSt和NPKF）高于长期不施肥处理（CK）,不同的种植制度中,长期复种轮作（NPKF）高于长期复种连作（NPK）;各处理的SMB-C/SOC（土壤有机碳）和SMB-N/TN（全氮）的比值的变化趋势与SMB-C和SMB-N变化一致;从PCR-DGGE分析,长期氮磷钾化肥配施有机肥（NPKM）处理的微生物量碳、氮的含量最高,微生物丰度最高,细菌物种最多,其次为长期撂荒（CK0）,CK处理细菌物种最少。UPGMC聚类分析表明NPK和NPKF处理细菌的群落结构相似,CK和CK0处理细菌的群落结构相似,而NPKM和NPKSt处理细菌的群落结构相似。     

长期不同施肥制度对潮棕壤微生物生物量碳、氮及细菌群落结构的影响

以沈阳生态站长期定位试验为研究平台,采用传统氯仿熏蒸方法和现代PCR-DGGE技术探讨了长期不同施肥制度对土壤微生物生物量碳和氮及细菌群落结构的影响.结果表明:在整个试验期,土壤微生物生物量碳和氮的动态变化趋势基本相同;长期施用有机肥可显著提高土壤有机碳和土壤微生物生物量碳和氮含量,而长期施用化肥明显降低土壤pH,土壤微生物生物量碳和氮含量也显著降低.DGGE图谱表明:不同施肥处理的细菌16S rDNA多数条带分布相同,28条带中有18条为共有条带,说明潮棕壤中细菌类群较稳定,但其数量受到施肥的影响;长期施用有机肥促进潮棕壤细菌群落结构的多样性,而施用化肥处理则降低了其多样性.     

土地利用驱动的土壤性状变化影响微生物群落结构和功能

微生物在调节陆地生态系统地球化学循环过程中具有重要作用。土地利用方式改变显著影响土壤微生物群落结构和功能,但对土地利用驱动的土壤性状变化与微生物群落结构和功能关系的研究相对匮乏。依托长期定位监测试验（始于1984年）,通过16S rRNA基因片段和ITS高通量测序,研究了土地利用方式（裸地、农田、草地）驱动的土壤碳氮变化对微生物群落结构和功能的影响。结果表明：对于细菌群落而言,裸地中α-多样性最高、其次是草地、农田中最低,农田和草地中细菌优势菌群变形菌（Proteobacteria）和放线菌门（Actinobacteria）相对丰度较裸地低4.5%、3.9%和5.5%、3.8%;对于真菌群落而言,裸地子囊菌门（Ascomycota）相对丰度最高、农田次之、草地最低;化能异养型、好氧化能异养型细菌相对丰度裸地显著高于农田和草地（P<0.05）,而硝化型和好氧氨氧化型细菌裸地显著低于农田和草地（P<0.05）;腐生型真菌相对丰度大小排序为：裸地>农田>草地。细菌群落变化主要与土壤容重、全氮、矿质氮、C ： N比和微生物量碳有关,而真菌群落与土壤矿质氮有关。细菌和真菌功能菌群主要受土壤容重、土壤有机碳、土壤全氮、C ： N比和微生物量碳影响。因此,土壤容重、土壤全氮、土壤有机碳、C ： N比、微生物量碳、矿质氮差异可能是影响不同土地利用方式中微生物群落和功能变化的主要因素。     

不同种植方式对绿洲农田土壤酶活性与微生物多样性的影响

研究了玉米连作10年、小麦连作8年 棉花连作10年、棉花连作15年和棉花6年 6年小麦/油葵轮作4种种植方式对土壤过氧化氢酶、蔗糖酶、芳基硫酸酯酶、脱氢酶和蛋白酶活性的影响,并分析了土壤细菌、真菌、氨氧化古菌与氨氧化细菌对北疆绿洲农田不同种植方式的响应.结果表明： 不同种植方式对土壤过氧化氢酶、芳基硫酸酯酶、脱氢酶和蛋白酶活性影响明显,但对蔗糖酶无显著影响;对氨氧化古菌多样性指数有显著影响,对土壤细菌、真菌和氨氧化细菌多样性指数无明显影响.土壤真菌和氨氧化细菌群落结构对不同种植方式的响应较细菌和氨氧化古菌敏感.长期棉花连作使绿洲农田土壤酶活性下降,微生物群落多样性降低,而轮作可提高土壤酶活性和微生物群落结构多样性.
     

改变碳输入对亚热带人工林土壤微生物生物量和群落组成的影响

通过在亚热带杉木(Cunninghamia lanceolata)和米老排(Mytilaria laosensis)人工林中设置互换凋落物、去除凋落物、去除凋落物+去除根系和对照处理来分析改变地上、地下碳输入对人工林土壤微生物生物量和群落组成的影响。结果显示,改变地上、地下碳输入对土壤微生物生物量碳、氮的影响因树种而异。在米老排林中,土壤微生物生物量不受碳源的限制。而在杉木林中,加入米老排凋落物、去除凋落物和去除凋落物+去除根系3种处理中土壤微生物生物量碳、氮具有明显增加的趋势。磷脂脂肪酸分析结果显示,杉木林中,添加高质量的米老排凋落物后,革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了24%、24%、53%、25%、28%,革兰氏阴性细菌和丛枝菌根真菌的相对丰度均有显著增加。与对照相比,杉木林中去除凋落物后革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了22%、29%、44%、25%、52%,真菌与细菌比值显著增加了21%。但是,去除凋落物+去除根系处理对两个树种人工林土壤微生物群落组成均无显著影响。米老排和杉木林土壤微生物生物量碳、氮的季节变化格局不同,土壤养分有效性可能是驱动土壤微生物生物量季节变化的主要因子。未来研究需要关注凋落物和根系在不同树种人工林中对土壤微生物群落的相对贡献。     

长期施肥对新疆灰漠土土壤微生物群落结构与功能多样性的影响

以20a新疆国家灰漠土土壤肥力与肥料效益长期定位试验为平台,采用常规培养法,结合Biolog技术对可培养微生物、生理菌群数量和碳源利用进行测定分析,研究撂荒(CK0)、耕作不施肥(CK)、不同化肥(N、NK、NP、PK、NPK)、化肥配施低量高量有机肥(NPKM1和NPKM2)和秸秆还田(NPKS)等10种处理土壤微生物特征,揭示长期施肥对土壤微生物群落结构与功能多样性的影响。结果表明:(1)可培养微生物:与CK处理相比,CK0处理显著提高了细菌、放线菌和真菌的数量(P0.05),NPKS处理微生物数量则显著降低(P0.05);不同化肥处理的细菌(除PK处理外)、放线菌(除PK和N处理外)数量也有所增加,增幅在8.14%—135.70%和15.30%—44.78%之间;真菌数量(除NK处理外)则有一定幅度的降低;NPKM1和NPKM2处理,微生物数量最高,细菌分别增加了162.20%和173.75%,放线菌增加了34.39%和39.37%,真菌增加了63.33%和488.33%;(2)生理菌群:与CK0相比,CK处理显著提高了自生固氮菌和亚硝化细菌数量(P0.05),显著降低了氨化细菌和纤维素分解菌数量(P0.05);与CK相比,NPKM1和NPKM2处理显著提高土壤中与氮素转化有关的生理菌群数量(P0.05),不同化肥处理和NPKS处理的影响不相同,NPK处理显著高于其余处理(P0.05);(3)微生物碳源利用:微生物活性表现为NK、NPKM1、NPKM2N、NPK、CKPK、NPKSCK0、NP;CK0处理3个多样性指数以及NPKM1、NPKM2和NK处理Shannon(H)指数最高,其余施肥处理差异不显著;糖类、氨基酸类、羧酸类和胺类是微生物利用的主要碳源。(4)聚类分析表明,除NP处理外,施氮处理土壤有较为相似的碳源利用,细菌和真菌与养分之间有较好的相关性,可培养微生物和生理菌群与微生物碳源利用的相关性较差。因此,长期不同施肥对新疆灰漠土土壤微生物群落结构和功能多样性产生了显著的影响,长期耕作不施肥降低了土壤微生物群落结构和功能多样性,不同化肥配合施用对微生物群落的影响不同,NPK及NPK配施有机肥可提高土壤微生物多样性。     

长期不同施肥制度对潮棕壤肥力及微生物活性的影响

利用长期定位试验研究了不同施肥制度对潮棕壤肥力及微生物活性的影响。结果表明:长期施用有机肥、无机肥显著降低土壤pH;长期施用化肥并不能增加土壤全碳、氮含量,而有机肥的长期施用却能显著提高土壤有机质含量;土壤长期无P、K肥料施入则会出现P、K的亏损。有机肥处理(M,N+M和NPK+M)的微生物量均显著高于不施肥处理(CK),且这些处理间无显著差异;NPK处理与CK处理间无显著差异,而长期施用N肥显著降低土壤微生物量;均衡施肥处理(M,N+M,NPK和NPK+M)均能显著增强土壤微生物呼吸(P0.05),而单施N处理对土壤微生物呼吸无显著影响;与CK相比,施肥处理均能显著提高土壤氨化作用(P0.05),其中以NPK+M处理最高;除N处理外,其他施肥处理均显著提高土壤硝化作用(P0.05)。相关性分析显示,土壤微生物量碳、氮,微生物呼吸,氨化和硝化作用均与土壤全碳、全氮极显著相关(P0.01),均能够较好地反映土壤肥力变化情况;而土壤微生物活性与其他理化因子相关性不一致,表明它们对土壤理化因子变化的响应程度不同。     

不同施肥对农田黑土微生物群落的影响

以未施肥(CK)和休闲(Fallow)处理为对照,研究黑土肥料定位站NP、NPK、MCK(有机肥)、MNP(有机肥 氮磷)、MNPK(有机肥 氮磷钾)等长期有机、无机肥施用对土壤基本理化性质、磷脂脂肪酸(PLFA)、酸(碱)性磷酸酶、微生物量碳或氮(SMBC或SMBN)等影响.结果表明,有机肥施用有效地提高了土壤有机质、总氮及速效氮、磷、钾等养分含量,显著地增加了SMBC(SMBN)和真菌、细菌的PLFA含量以及磷酸酶活力,极大地提高了土壤真菌/细菌比值;而长期NP或NPK处理不但未明显改善土壤养分状况,甚至抑制了磷酸酶活性及大多数菌群生长.总细菌PLFA与饱和脂肪酸或单烯脂肪酸与环化脂肪酸之间呈极显著正相关(p<0.01).PLFA主成分分析表明,有机肥与化肥处理微生物群落结构显著不同;个别PLFA载荷值分析表明,真菌脂肪酸易受无机肥施用影响,而G-菌或G 菌脂肪酸更易受有机肥影响.休闲处理高水平微生物活性与生物量的主要贡献者是黑土细菌群落而不是真菌.     

海拔对辽东栎林地土壤微生物群落的影响

以北京东灵山辽东栎林地土壤为对象,运用氯仿熏蒸-浸提法及磷脂脂肪酸分析(PLFA)法,研究林木生长季节土壤微生物群落随海拔梯度的变化特征.结果表明:随着海拔升高,辽东栎林土壤微生物生物量碳、氮,以及微生物各类群含量均有差异但不显著;土壤细菌/真菌升高,而革兰氏阳性菌(G+)/革兰氏阴性菌(G-)降低.土壤微生物生物量碳、氮以及细菌、真菌、G+细菌、G-细菌的含量与土壤含水量、有机碳、全氮呈显著正相关,土壤真菌含量与土壤碳氮比值呈正相关.土壤微生物群落组成结构(细菌/真菌和G+细菌/G-细菌)的变化主要受土壤温度和土壤含水量的显著影响,说明土壤微生物群落结构对环境条件的变化敏感.随着全球变暖的加剧,暖温带辽东栎林地土壤真菌和G+细菌的比例有升高的趋势.     

长期不同施肥制度下几种土壤微生物学特征变化

 为阐明土壤微生物对土壤健康的生物指示功能, 以国家褐潮土肥力与肥料效益监测基地的长期肥料试验为平台, 应用BIOLOG ECO微平板培养法与常规分析法研究了长期施肥15年后不同施肥制度对土壤微生物生物量、活性、群落代谢功能多样性及土壤肥力的影响。研究结果表明, 与对照(CK)相比, 长期化肥与有机肥配施土壤中土壤有机质(SOM)、全氮(STN)、全磷(STP)含量升高, 土壤C/N与pH值降低, 土壤微生物量碳(Soil microbial biomass carbon, SMBC)、生物微生物量氮(Soil microbial biomass nitrogen, SMBN)、微生物商(qMB)及脲酶(Urease)活性升高, BIOLOG ECO微平板平均颜色变化率(Average well color development, AWCD)、土壤微生物代谢功能多样性指数变化不明显。和长期单施化肥处理(NPK)相比, 长期化肥与有机肥配施处理中上述几种微生物学特征(SMBC、SMBN、qMB、Urease及AWCD、代谢功能多样性指数)均呈极显著增加。NPK处理与CK相比虽然SOM、STN、STP含量稍有升高, 土壤C/N与pH值降低, SMBC、SMBN、qMB及Urease活性增高, 但是AWCD、土壤微生物代谢功能多样性指数却显著下降。过氧化氢酶活性(Catalase)在各处理土壤中的差异不显著。土壤微生物碳源利用的主成分分析表明, 长期不同施肥各处理在土壤微生物利用碳源的种类和能力上有差异。此试验说明, 土壤微生物受农业管理措施和多种环境因素的影响, 土壤微生物学特征可作为土壤质量的敏感指标, 为提高作物产量、增强肥力提供理论参考。     

长期施肥对稻田土壤有机氮、微生物生物量及功能多样性的影响

以位于湖南省新化和宁乡县两个稻田肥力长期定位试验点的土样为材料,研究了不同施肥处理对稻田土壤有机氮组分、微生物生物量及功能多样性的影响.结果表明：与不施肥处理（CK）相比,化肥配施有机肥处理提高了稻田土壤酸解总氮（TAHN）及其组分中氨基糖氮（ASN）、氨基酸氮（AAN）和酸解氨态氮（AN）的含量,不同施肥处理对组分中酸解未知氮（HUN）的影响不尽相同.与CK相比,单施化肥处理对土壤微生物生物量碳、氮（MBC、MBN）含量的影响较小,化肥配施有机肥处理则显著提高了土壤MBC和MBN的含量.采用BIOLOG法对土壤微生物群落功能多样性进行测定,结果表明：中、高量有机肥处理提高了稻田土壤微生物的碳源利用率和微生物群落功能多样性;土壤微生物碳源利用的类型因长期不同施肥处理而产生差异.     

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.     

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.     

The effects of mineral fertilizer and organic manure on soil microbial community and diversity

The effects of mineral fertilizer (NPK) and organic manure on phospholipid fatty acid profiles and microbial functional diversity were investigated in a long-term (21-year) fertilizer experiment. The experiment included nine treatments: organic manure (OM), organic manure plus fertilizer NPK (OM + NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer N (N), fertilizer P (P), fertilizer K (K), and the control (CK, without fertilization). The original soil was extremely eroded, characterized by low pH and deficiencies of nutrients, particularly N and P. The application of OM and OM + NPK greatly increased crop yields, soil pH, organic C, total N, P and K, available N, P and K content. Crop yields, soil pH, organic C, total N and available N were also clearly increased by the application of mineral NPK fertilizer. The amounts of total PLFAs, bacterial, Gram-negative and actinobacterial PLFAs were highest in the OM + NPK treatment, followed by the OM treatment, whilst least in the N treatment. The amounts of Gram-positive and anaerobic PLFAs were highest in the OM treatment whilst least in the P treatment and the control, respectively. The amounts of aerobic and fungal PLFAs were highest in the NPK treatment whilst least in the N and P treatment, respectively. The average well color development (AWCD) was significantly increased by the application of OM and OM + NPK, and the functional diversity indices including Shannon index (H ^′ ), Simpson index (D) and McIntosh index (U) were also significantly increased by the application of OM and OM + NPK. Principal component analysis (PCA) of PLFA profiles and C source utilization patterns were used to describe changes in microbial biomass and metabolic fingerprints from nine fertilizer treatments. The PLFA profiles from OM, OM + NPK, NP and NPK were significantly different from that of CK, N, P, K and NK, and C source utilization patterns from OM and OM + NPK were clearly different from organic manure deficient treatments (CK, N, P, K, NP, NK 6 and NPK). Stepwise multiple regression analysis showed that total N, available P and soil pH significantly affected PLFA profiles and microbial functional diversity. Our results could provide a better understanding of the importance of organic manure plus balanced fertilization with N, P and K in promoting the soil microbial biomass, activity and diversity and thus enhancing crop growth and production.     

长期施用有机无机肥对潮土微生物群落的影响

微生物群落结构是土壤生态系统变化的预警及敏感指标,可用于表征土壤质量及其生态功能变化。本文用磷脂脂肪酸法研究了有机肥和NPK肥料长期施用对华北平原潮土微生物群落结构的影响及其变化特征。结果表明：长期施用有机和无机肥不仅提高了土壤有机碳、全氮、速效磷和速效钾等含量,改善了土壤酸碱度,而且显著增加了土壤微生物生物量,其中以有机肥的效果最为明显,增幅达到15.4%。长期施用肥料有机肥也改变了土壤微生物的群落结构,提高了细菌数量,降低了放线菌含量,而对真菌数量没有明显影响,导致真菌与细菌的比值下降。主成分分析表明,长期施用有机肥的土壤,细菌以含a19:0、br14:0、16:1w5c和17:1w9而真菌以含18:1w10c的微生物为优势种群,NPK处理土壤中细菌以含18:1w7、i19:0、br18:0、16:1w7t和a15:0的微生物为优势种群,CK处理中没有明显的优势种群。     

Effects of fertilization on bacterial community structure and function in a black soil of Dehui region estimated by Biolog and PCR-DGGE methods

Soil microbial community structure and function are commonly used as indicators for soil quality and fertility. In this paper, the bacterial community structure and function in a black soil of Dehui region influenced by fertilization were investigated by Biolog and PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) methods. Biolog examination showed that substrate richness and catabolic diversities of bacterial communities were the highest in the treatment of farm yard manure, and the lowest in the chemical fertilizer treatment. DGGE fingerprint showed that the majority of bands were similar among all treatments, suggesting that microbial communities with those bands were stable, and not influenced by fertilization. In general, chemical fertilizer decreased the diversity of soil bacterial communities. The PCA (principal component analysis) plots of Biolog and DGGE revealed that the structure and function of bacterial communities were similar in the non-fertilized control and the treatment of farm yard manure alone, which inferred that the application of farm yard manure increased the quantity of soil microbes but had less effect on the changes of community structure. The catabolic function was similar, but the composition structure differed between the treatments of chemical fertilizer alone and combined application of farm yard manure with chemical fertilizer. These results suggest that the use of chemical fertilizer mainly decreased the catabolic activity of the fast growth bacteria or eutrophic bacteria.     

Responses of Bacterial Communities in Arable Soils in a Rice-Wheat Cropping System to Different Fertilizer Regimes and Sampling Times

Soil physicochemical properties, soil microbial biomass and bacterial community structures in a rice-wheat cropping system subjected to different fertilizer regimes were investigated in two seasons (June and October). All fertilizer regimes increased the soil microbial biomass carbon and nitrogen. Both fertilizer regime and time had a significant effect on soil physicochemical properties and bacterial community structure. The combined application of inorganic fertilizer and manure organic-inorganic fertilizer significantly enhanced the bacterial diversity in both seasons. The bacterial communities across all samples were dominated by Proteobacteria, Acidobacteria and Chloroflexi at the phylum level. Permutational multivariate analysis confirmed that both fertilizer treatment and season were significant factors in the variation of the composition of the bacterial community. Hierarchical cluster analysis based on Bray-Curtis distances further revealed that bacterial communities were separated primarily by season. The effect of fertilizer treatment is significant (P = 0.005) and accounts for 7.43% of the total variation in bacterial community. Soil nutrients (e.g., available K, total N, total P and organic matter) rather than pH showed significant correlation with the majority of abundant taxa. In conclusion, both fertilizer treatment and seasonal changes affect soil properties, microbial biomass and bacterial community structure. The application of NPK plus manure organic-inorganic fertilizer may be a sound fertilizer practice for sustainable food production.     

Effects of Different Organic Manures on the Biochemical and Microbial Characteristics of Albic Paddy Soil in a Short-Term Experiment

This study aimed to evaluate the effects of chemical fertilizer (NPK), NPK with livestock manure (NPK+M), NPK with straw (NPK+S), and NPK with green manure (NPK+G) on soil enzyme activities and microbial characteristics of albic paddy soil, which is a typical soil with low productivity in China. The responses of extracellular enzyme activities and the microbial community diversity (determined by phospholipid fatty acid analysis [PLFA] and denaturing gradient gel electrophoresis [DGGE]) were measured. The results showed that NPK+M and NPK+S significantly increased rice yield, with NPK+M being approximately 24% greater than NPK. The NPK+M significantly increased soil organic carbon (SOC) and available phosphate (P) and enhanced phosphatase, β-cellobiosidase, L-leucine aminopeptidase and urease activities. The NPK+S significantly increased SOC and available potassium (K) and significantly enhanced N-acetyl-glucosamidase, β-xylosidase, urease, and phenol oxidase activities. The NPK+G significantly improved total nitrogen (N), ammonium N, available P, and N-acetyl-glucosamidase activity. The PLFA biomass was highest under NPK+S, followed by NPK+M and NPK+G treatments. Principal component analysis (PCA) of the PLFA indicated that soils with NPK+M and NPK+S contained higher proportions of unsaturated and cyclopropane fatty acids (biomarkers of fungi and gram-negative bacteria) and soil under NPK+G contained more straight chain saturated fatty acids (representing gram-positive bacteria). PCA of the DGGE patterns showed that organic amendments had a greater influence on fungal community. Cluster analysis of fungal DGGE patterns revealed that NPK+G was clearly separated. Meanwhile, the bacterial community of NPK+M treatment was the most distinct. RDA analysis revealed changes of microbial community composition mostly depended on β-xylosidase, β-cellobiosidase activities, total N and available K contents. The abundances of gram-negative bacterial and fungal PLFAs probably effective in improving fertility of low-yield albic paddy soil because of their significant influence on DGGE profile.