Effect of slow-release urea on soil nematode community structure in a Chinese soybean field

The effect of slow-release urea on soil nematode community structure was investigated in a soybean field in northeast China.Three treatments,no urea (CK),conventional urea (U) and slow-release urea (SRU),were arranged in a completely random design.The results show that the abundance of total nematodes was significantly higher in SRU than in CK and U.Significant differences in the abundance of bacterivores with colonizer-persister (cp) values 2-3,fungivores with cp 2 and herbivores with cp 3 were found among different treatments.Forty-one genera were identified,of which Acrobeloides,Aphelenchus and Heterodera were dominant.Soil nematode guilds and genera exhibited different responses to slow-release urea.The most trophic groups and genera had greater abundances in SRU than in CK and U.Slow-release urea had a positive effect on soil nematode community structure.     

Effects of slow-release urea fertilizers on urease activity,microbial biomass, and nematode communities in an aquic brown soil

A field experiment was carried out at the Shenyang Experimental Station of Ecology (CAS) in order to study the effects of slow-release urea fertilizers high polymer-coated urea (SRU1), SRU1 mixed with dicyandiamide DCD (SRU2), and SRU1 mixed with calcium carbide CaC2 (SRU3) on urease activity, microbial biomass C and N, and nematode communities in an aquic brown soil during the maize growth period. The results demonstrated that the application of slow-release urea fertilizers inhibits soil urease activity and increases the soil NH4+-N content. Soil available N increment could promote its immobilization by microorganisms. Determination of soil microbial biomass N indicated that a combined application of coated urea and nitrification inhibitors increased the soil active N pool. The population of predators/omnivores indicated that treatment with SRU2 could provide enough soil NH4+-N to promote maize growth and increased the food resource for the soil fauna compared with the other treatments.     

Effects of slow-release urea fertilizers on urease activity,microbial biomass, and nematode communities in an aquic brown soil

A field experiment was carried out at the Shenyang Experimental Station of Ecology (CAS) in order to study the effects of slow-release urea fertilizers high polymer-coated urea (SRU1), SRU1 mixed with dicyandiamide DCD (SRU2), and SRU1 mixed with calcium carbide CaC2 (SRU3) on urease activity, microbial biomass C and N, and nematode communities in an aquic brown soil during the maize growth period. The results demonstrated that the application of slow-release urea fertilizers inhibits soil urease activity and increases the soil NH4+-N content.Soil available N increment could promote its immobilization by microorganisms. Determination of soil microbial biomass N indicated that a combined application of coated urea and nitrification inhibitors increased the soil active N pool. The population of predators/omnivores indicated that treatment with SRU2 could provide enough soil NH4+-N to promote maize growth and increased the food resource for the soil fauna compared with the other treatments.     

Effects of slow-release urea fertilizers on urease activity,microbial biomass,and nematode communities in an aquic brown soil

A field experiment was carried out at the Shenyang Experimental Station of Ecology (CAS) in order to study the effects of slow-release urea fertilizers high polymer-coated urea (SRU1), SRU1 mixed with dicyandiamide DCD (SRU2), and SRU1 mixed with calcium carbide CaC₂ (SRU3) on urease activity, microbial biomass C and N, and nematode communities in an aquic brown soil during the maize growth period. The results demonstrated that the application of slow-release urea fertilizers inhibits soil urease activity and increases the soil NH₄ ⁺-N content. Soil available N increment could promote its immobilization by microorganisms. Determination of soil microbial biomass N indicated that a combined application of coated urea and nitrification inhibitors increased the soil active N pool. The population of predators/omnivores indicated that treatment with SRU2 could provide enough soil NH₄ ⁺-N to promote maize growth and increased the food resource for the soil fauna compared with the other treatments.     

高通量测序分析冻融期碳源输入方式对土壤线虫群落的影响

植物碳源输入途径变化对土壤生物群落的影响研究是目前学术界关注的热点问题。为探究温带森林生态系统碳源输入方式对土壤线虫群落的影响,通过Illumina MiSeq技术分析了不同碳源输入方式下土壤线虫群落组成和多样性的变化。研究结果显示:所有处理(凋落物和根系同时输入;仅根系输入;仅凋落物输入;无碳源输入)中共发现土壤线虫68属,其中食细菌线虫的相对丰度最大;各碳源输入方式中仅凋落物输入处理对线虫群落组成的影响最为明显,表现为:与凋落物和根系同时输入处理相比,仅凋落物输入处理中食细菌线虫的相对丰度明显增加,食真菌线虫的相对丰度显著降低以及捕食杂食线虫的相对丰度显著增加。从线虫群落的多样性指数角度看,无碳源输入处理中土壤线虫群落的多样性指数(H'')下降,优势度指数(Dom)增高;仅凋落物输入处理中均匀度指数(J)最高。从线虫群落的生态指数角度看,仅凋落物输入处理的线虫群落成熟度指数(MI)最高;各碳源输入处理的分解过程均以细菌分解通道为主。研究表明,土壤线虫群落受到碳源输入变化的调节,仅凋落物输入处理比仅根系输入处理对土壤线虫群落的影响更大。无碳源输入处理的物种多样性明显下降,仅凋落物输入处理的土壤食物网更加稳定。研究结果丰富了森林土壤线虫多样性的研究内容,并为高通量测序技术在土壤线虫方面的研究提供方法和数据的支持。     

Effects of slow-release urea fertilizers on urease activity,microbial biomass,and nematode communities in an aquic brown soil

A field experiment was carried out at the Shenyang Experimental Station of Ecology (CAS) in order to study the effects of slow-release urea fertilizers high polymer-coated urea (SRU1), SRU1 mixed with dicyandiamide DCD (SRU2), and SRU1 mixed with calcium carbide CaC₂ (SRU3) on urease activity, microbial biomass C and N, and nematode communities in an aquic brown soil during the maize growth period. The results demonstrated that the application of slow-release urea fertilizers inhibits soil urease activity and increases the soil NH₄ ⁺-N content. Soil available N increment could promote its immobilization by microorganisms. Determination of soil microbial biomass N indicated that a combined application of coated urea and nitrification inhibitors increased the soil active N pool. The population of predators/omnivores indicated that treatment with SRU2 could provide enough soil NH₄ ⁺-N to promote maize growth and increased the food resource for the soil fauna compared with the other treatments.

     

麦田土壤真菌多样性对麦玉轮作长期秸秆还田和配施有机肥的响应

【背景】土壤真菌主导田间秸秆腐解的过程,秸秆还田配施有机肥可为真菌提供良好的营养物质。【目的】研究麦玉轮作模式下长期秸秆还田配施有机肥对麦田土壤真菌多样性的影响。【方法】依托山西南部麦玉轮作区长达14年的秸秆还田和施有机肥长期定位试验,采用高通量测序开展土壤真菌群落结构和多样性对不施肥+秸秆清茬(CK)、氮磷化肥+秸秆清茬(NP)、氮磷化肥+秸秆还田(SNP)、氮磷化肥+有机肥+秸秆清茬(NPM)及氮磷化肥+秸秆还田+有机肥(SNPM)的响应差异研究。【结果】秸秆还田和施有机肥处理组的物种丰富度指数、Chao1指数和ACE指数均高于CK。5个处理共产生953个分类操作单元(operational taxonomic units, OTU),CK、NP、NPM、SNP和SNPM分别具有398、451、472、462和440个OTU。在门水平上共检测出9个菌门,其中子囊菌门(Ascomycota)、毛霉门(Mucoromycota)和担子菌门(Basidiomycota)为3个主要菌门,各处理中所占丰度差异显著;在属水平上共检测出262个真菌属,其中CK丰度较高的3个属为柄孢壳菌属(Podospora) 18.85%、被孢霉属(Mortierella) 16.67%和镰刀菌属(Fusarium) 7.77%;NP、NPM、SNP和SNPM丰度较高的前3个相同属均为Dendrostilbella、毛葡孢属(Botryotrichum)和被孢霉属(Mortierella),但相对丰度值存在差异。由聚类分析可知,NPM和SNPM群落组成相似度高,归为一类,而CK、NP、SNP各独立为一类。与环境因子间冗余分析发现,TN含量是影响土壤真菌群落结构的关键因子,也受速效磷、pH、速效钾、碱解氮和全磷等环境指标影响。【结论】长期秸秆还田和施有机肥改变了小麦土壤真菌种群结构和多样性。     

Response of soil nematode community structure and diversity to long-term land use in the black soil region in China

Soil nematodes are sensitive to environmental changes and are used widely as indicators of soil conditions. The community structure and diversity of soil nematodes were studied in different long-term land use regimes in the black soil area in Northeast China. The land use regimes were maintained for 22?years, and included crop land (CL), grass land (GL) and bare land (BL). Soil samples were taken throughout the growing season, and nematodes were extracted and identified. A total of 39 nematode genera with relative abundance over 0.1?% were identified. Heterodera was the dominant genus in CL; Boleodorus was the dominant genus in GL, and Boleodorus, Eucephalobus and Filenchus were the dominant genera in BL. Land use had a significant effect on abundance of all soil nematode tropic groups and ecological indices. Sampling time had an effect on soil nematode abundance, but only on three of the eight nematode ecological indices MI (maturity index of free-living nematode), CI (channel index) and EI (enrichment index). SR (species richness index) was highest in GL where plant species diversity was also high. The CI was the highest in BL among three land uses, which means the soil food web dominated, with fungal decomposition channels in BL. Soil nematode community structure and diversity was shown to be an effective and informative tool for analyzing ecological aspects of land use in black soil regions. The data are inconclusive as to whether the effect of land use on soil nematode parameters is direct, or indirect via inducing changes in soil physicochemical properties.     

宁夏枸杞根际土壤线虫群落特征

宁夏枸杞具有很高的药用价值和营养价值,在宁夏大面积种植,带来了巨大的经济效益.研究不同条件下宁夏枸杞根际土壤线虫群落特征,对防止枸杞园土壤退化具有重要意义.以宁夏枸杞之乡——中宁为研究区,系统分析了季节、树龄和土层对枸杞根际土壤线虫数量和生态指数的影响.结果表明: 夏季宁夏枸杞根际土壤线虫数量最多,小杆属和拟丽突属为优势属;春季线虫数量最少,小杆属、针属和盘旋属为优势属;从春季到秋季,线虫稀有属种类和个体密度逐渐减少.随着树龄的增加,夏季根际土壤线虫总数逐渐减少;春季和秋季枸杞根际线虫总数先增加后减少,其中9年树龄根际土壤线虫总数最多.各树龄根际均为食细菌线虫所占比例最大,食真菌线虫和捕食-杂食类线虫比例很小,树龄<3年和>9年时植物寄生线虫比例相对较大.夏季枸杞根际20～40 cm比0～20 cm土壤线虫数量增加49.4%.随着树龄的增加,枸杞根际土壤线虫多样性指数、均匀度指数和丰富度指数均呈减小-增大-减小的趋势,而优势度指数先减小后增大.土壤pH值与土壤线虫优势度指数呈显著正相关;土壤有机质和速效磷与植物寄生线虫分别呈显著正相关和负相关;土壤碱解氮与线虫总数呈显著正相关;速效钾与线虫多个生态指数均呈显著负相关.整体上,随着树龄的增加,春季和秋季土壤线虫数量先增加后减少,夏季土壤线虫数量呈逐渐减少的趋势;线虫多样性下降,土壤逐渐退化.此外,在幼林和树龄>9年后需要抑制土壤植物寄生线虫的繁殖,以减少后期因线虫引起的病害.     

Influence of different fertilizer types of zucchini (Cucurbita pepo) on the structure of nematode communities

Increasing efficiency of production of vegetable crops is directly related to search for appropriate solution to increase their productivity. Organic amendments have been used for centuries to improve soil fertility and crop yield. Our study suggests that organic amendments can also be used as nematicidal agents. The survey was conducted on Experimental field of Department Horticulture at Agricultural University of Plovdiv, Bulgaria in 2009 on nematode infested sites. Combination with two types of fertilizers was used to investigate their effects on the community of soil nematodes. Characterization and comparative analysis among treatments of soil nematode community structure based on different ecological measures such as total nematode abundance, number of genera, trophic diversity and etc., was made. Changes in the composition and structure of nematode community as result of different fertilizer types were assessed.     

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.     

紫色土线虫对长期不同施肥措施的响应

土壤线虫在农田生态系统中数量丰富且对土壤环境变化敏感, 可用于评估不同田间管理条件下的土壤健康。本文探究了紫色土区长期不同施肥措施及土壤团聚体粒径对线虫群落的分布及其生态功能多样性的影响。试验设置了5个施肥处理: 不施肥(对照, CK)、单施化肥(NPK)、生物炭 + 化肥(BCNPK)、商品猪粪 + 化肥(OMNPK)和秸秆 + 化肥(RSDNPK)。团聚体粒径分为: 原状土(BS)、大团聚体(> 2 mm; LA)和小团聚体(0.25-2 mm; SA)。结果表明, 与对照相比, 施肥可促进线虫数量增长, 其中单施化肥处理下增幅最小(66%); 有机物料与化肥配施对线虫数量的提升更为显著, 秸秆 + 化肥处理下增幅达206%。不同施肥处理间线虫类群相对丰度差异显著, 大小均表现为: 食细菌线虫(BA) > 杂食/捕食线虫(OP) > 植食线虫(PP) > 食真菌线虫(FU)。小团聚体较其他土壤团聚体的杂食/捕食线虫丰度更低, 食细菌线虫丰度较高。秸秆与化肥配施处理下线虫群落结构指数和富集指数显著增加, 且各施肥处理下线虫功能足迹呈现明显差异。有机肥与化肥配施(尤其是秸秆 + 化肥)可提高土壤养分供应且有利于形成稳定健康的土壤生态系统, 助推区域农业的可持续发展。     

目标树经营初期对柏木人工林土壤线虫群落的影响

为研究目标树经营初期对柏木人工林土壤线虫群落的影响,对遂宁市安居区处于竞争生长阶段的柏木林进行3种不同密度目标树经营,共计样地12个(目标树密度为6株/667 m~2、9株/667 m~2、12株/667 m~2以及对照各3个)。在目标树经营1年后,采集春、夏、秋、冬4个季节样品共252个,采用改进的Baermann湿漏斗法分离土壤线虫,共鉴定出土壤线虫59科143属。其中Prionchulus为优势属,食细菌性线虫38属,食真菌性线虫12属,植食性线虫36属,杂食/捕食性线虫57属。土壤线虫生活史策略以c-p 4类群为主,占总数的44.33%,其中目标树密度为9株/667 m~2整个样地(9N)的c-p 4占比最大。目标树经营增加了土壤线虫的数量,目标树密度为9株/667 m~2的目标树单株(9C)线虫密度达到最大;目标树经营处理中均以杂食/捕食性线虫数量最多,其中9C杂食/捕食性线虫数量均高于其他处理;目标树经营提高了多样性指数(H′)、均匀度指数(J)、线虫营养多样性指数(TD)、线虫成熟度指数(MI),目标树经营改善了土壤线虫群落结构,其中目标树密度为9株/667 m~2样地的土壤线虫群落结构最优。研究结果表明,采用目标树经营有利于提升土壤线虫群落多样性,使柏木人工林生态系统向更稳定的方向发展,其中目标树密度为9株/667 m~2的效果最为显著。     

根际效应对大豆田土壤线虫群落组成及多样性的影响

根际作为重要的环境界面是植物与环境之间物质能量交换的场所,关于根际效应的研究已成为土壤生态学的新兴热点领域,然而有关大豆根际效应对土壤动物多样性影响的研究报道并不多见。在三江平原选择连续耕作15a的大豆田,对大豆根际区与非根际区土壤线虫群落结构组成进行了对比分析。结果表明:大豆根际区土壤线虫总数、辛普森多样性指数(Dom)显著高于非根际区,根际区的物种数(S)、物种丰富度指数(SR)显著低于非根际区。说明大豆根际效应增加土壤线虫的丰度,但降低了线虫群落结构的复杂性。大豆根际区植物寄生线虫(PP)、食真菌线虫(FF)和食细菌线虫(BF)数量显著高于非根际区,而PP类群的比例在根际区却显著低于非根际区。这一研究结果表明食微线虫(FF和BF)类群在大豆根际区的比例增加更显著。食真菌与食细菌线虫数量比值(F/B)指示大豆根际区细菌生物量相对高于真菌生物量。研究结果丰富了农田土壤线虫多样性的研究内容,并为我国东北大豆田线虫病害的防治及定制相应的农业管理措施提供参考。     

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.     

基于高通量测序分析西藏北部高寒草甸不同深度土壤线虫群落分布特征

为了研究藏北高寒草甸土壤线虫多样性,于2017年8月,采用Illumina MiSeq测序技术,研究了西藏北部高寒草甸0—25 cm范围内不同深度土层的土壤线虫群落组成与结构特征。结果表明:5个不同深度共获得OTU 990个,隶属于3个纲,7个目,25个科,30个属,刺嘴纲Enoplea为共有优势土壤线虫群落;对样品进行Alpha多样性评价,计算Chao 1指数、Shannon指数和Ace指数,发现5—10 cm的土壤样品群落有较高的丰富度;属水平Heatmap图分析可知20—25、15—20、0—5、5—10、10—15 cm土壤线虫群落的组成相似性有一个递增的趋势。与不同深度藏北高山嵩草(盛长期)线虫群落结构相关性较大的土壤化学指标是K~+、含水率、有机质和Zn~(2+)。研究发现不同深度土壤线虫种类及丰度存在一定的差异,可为研究藏北高寒草地土壤线虫群落特点提供依据。     

江苏省不同种植年限的西/甜瓜农田土壤线虫群落特征

在江苏省主要西/甜瓜产区,采集不同种植年限的西/甜瓜农田土壤,采用线虫形态学的鉴定方法,分析了不同种植年限西/甜瓜农田土壤线虫的数量、群落结构及相关生态指数的变化。结果表明:所有调查样点中,共发现土壤线虫54属,平均682条·100 g^-1干土,其中原杆属线虫、拟丽突属线虫和矮化属线虫在不同种植年限的西/甜瓜农田土壤中均为优势属;随着种植年限的增加,土壤线虫的总数量虽无显著变化,但其中食细菌类线虫和杂食-捕食类线虫数量显著减少,而植物寄生类线虫数量显著增加;植物寄生类线虫中的矮化属、根结属线虫数量不断增加;随着种植年限的增加,土壤线虫的多样性指数(H)、瓦斯乐斯卡指数(WI)、自由生活线虫成熟度指数(MI)显著降低,线虫通道指数(NCR)、植物寄生线虫成熟度指数(PPI)、PPI/MI显著升高,其他指数无显著变化;相关性分析结果显示,土壤线虫数量与土壤pH、速效磷、有效锌和有效硼均呈显著正相关;土壤p H、有机质、全氮、速效钾、有效硼和有效锌对土壤优势属线虫的影响较大;连续种植西/甜瓜会增加土壤植物寄生类线虫数量,进而可能造成西/甜瓜连作障碍的发生;连续种植6~10年,土壤线虫的多样性最低、稳定性最差,土壤环境已趋于恶化。     

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。     

施肥方式对干旱半干旱地区土壤氨氧化微生物数量和群落的影响

氨氧化是硝化作用的限速步骤,也是评估土壤氮循环和提高氮肥利用效率的重要指标。以内蒙古农牧业科学院旱作实验站长期定位实验为基础,通过实时荧光定量PCR和末端限制性片段长度多态性分析,研究了5种施肥方式（单施氮肥、单施有机肥、氮磷钾配施、有机无机配施和不施肥）对土壤氨氧化古菌（AOA）和氨氧化细菌（AOB）群落丰度、结构和活性的影响。结果表明：单施氮肥、氮磷钾肥配施以及有机无机肥配施均能显著提高AOB的丰度以及土壤硝化潜势。Nitrosospiria cluster 3a.1是不施肥土壤中主要的AOB种群,而施用氮肥后优势种群转变为Nitrosospiria cluster 3a.2。Nitrosospiria cluster 3b的比例在施用有机肥处理土壤中显著升高。在干旱半干旱地区,土壤pH和含水量是解释AOB群落结构变化的关键环境因子。AOA的丰度在单独施用氮肥处理中显著升高,但不同施肥方式对AOA的群落结构没有显著影响。     

Influence of cover crops and tillage systems on nematode populations in a maize-cover crop intercrop

Cropping systems affect the distribution/diversity of soil microorganisms, including soilborne pathogens. In order to examine the effect of the cropping systems on soil nematodes, maize (Zea mays) was intercropped with different cover crops [Glycine max (GM), Macrotyloma uniflorum (MU), Centrosema pascuorum (CP), Cucurbita maxima (CM) and a control experiment with no cover crop (NC)] under different tillage systems [no till, reduced tillage and conventional tillage] to evaluate the effect of the various treatments on nematode population. The treatments were arranged in a split-plot design with three replications each. Tillage was the main treatment while cover crops were applied to subtreatment. In all, nematodes belonging to twenty-two (22) plant parasitic nematode genera were identified. While most of the genera were identified on all the treatments, the interaction of tillage systems and cover crops had significant effect on the population of Xiphinema and Trichodorus only, showing the nullifying effect of some tillage practices on the other nematodes which were significant under crops as only treatments inter alia. This information could be used in nematode management when integrated management systems are being considered for such intercrop mixtures.