渣油在加氢处理中的氮分布和氮类型变化

采用氮分布和酸电位滴定分析技术对渣油在加氢处理中试装置上的氮含量及氮类型变化进行定量研究,结果表明:氮的总脱除率为42.36%,在上流式和固定床两个阶段的脱除率分别为26.76%和15.60%。焦化蜡油和减压渣油混合成的原料渣油的氮含量呈"U"型分布。随着加氢深度增加,芳香分中的氮含量降低,而胶质和沥青质中的氮含量增加。氮在渣油四组分中的分布规律是芳香分组分>胶质组分>沥青质组分。在加氢处理过程中,总氮、碱性氮和非碱性氮含量逐渐降低,但非碱性氮占总氮的质量分数呈降低趋势,而碱性氮占总氮质量分数呈增加趋势。

不同类型氮输入对三峡库区消落带紫色潮土氮赋存形态的影响

陆源氮输入是三峡水体富营养化的主要原因之一,外源氮在消落带土壤中的赋存形态是决定其进一步向三峡水体释放的关键.为此,以三峡典型土壤-紫色潮土为研究对象,进行4种氮输入〔分别添加NaNO_(3)、NH_(4)NO_(3)、(NH_(4))_(2)SO_(4)、CO(NH_(2))_(2)〕和淹水-落干两个水文条件处理,利用连续分级提取法测定土壤氮赋存形态含量,分析氮添加类型及水文条件对消落带紫色潮土氮赋存形态的影响.结果表明:NaNO_(3)、NH_(4)NO_(3)、(NH_(4))_(2)SO_(4)和CO(NH_(2))_(2)添加下,土壤培养结束后,离子交换态氮(IEF-N)含量在落干期分别为93.88、79.42、59.02和46.80 mg kg,在淹水期分别为65.60、56.95、42.46和32.94 mg kg;有机及硫化物结合态氮(OSF-N)含量在落干期分别为122.18、126.21、137.53和148.19 mg kg,在淹水期分别为142.22、149.09、156.43和161.76 mg kg;IEF-N含量变化占比在落干期分别为45.20%、35.56%、21.96%和13.82%,在淹水期分别为36.57%、30.80%、16.21%和7.26%;OSF-N含量变化占比在落干期分别为12.33%、15.02%、22.57%和29.68%,在淹水期分别为16.76%、21.84%、26.73%和30.29%.落干期和淹水期,IEF-N含量及其变化在氮添加总量中的占比均表现为NaNO_(3)添加下最高、CO(NH_(2))_(2)添加下最低,且落干期大于淹水期;OSF-N含量及其变化占比则与IEF-N表现相反.落干期和淹水期,外源氮主要表现为向OSF-N转化,此外,外源氮在落干期还存在向铁锰氧化物结合态氮转化的过程.研究显示,控制落干期消落带土壤氮输入(特别是硝态氮)是预防三峡水库富营养化的有效途径.

甘薯苗期耐低氮基因型筛选及不同氮效率类型综合评价

【目的】建立甘薯品种(系)耐低氮能力评价体系,筛选耐低氮基因型甘薯材料和评价不同氮效率类型,为研究耐低氮甘薯生理机制和挖掘氮高效基因奠定基础。【方法】采用水培试验,以来自国内外不同薯区的126份甘薯品种(系)为材料,低氮胁迫(0 mmol·L^(-1)纯氮)和正常施氮(14 mmol·L^(-1)纯氮)处理下,收集126个品种(系)地上干重、地上干物质增加量、地下干物质增加量、总干物质增加率、根冠比、蔓长、根长、叶数、叶绿素相对含量(CCI)、氮积累量和氮素生理利用效率11个性状表征值,计算各指标耐低氮胁迫指数。利用综合隶属函数法,进行主成分分析、回归分析和聚类分析,综合评价各甘薯品种耐低氮能力和氮效率类型。【结果】1)低氮水平条件下,不同供试甘薯品种(系)的地上干重、地上部干物质增加量、地下部干物质增加量、总干物质增加率、根长、蔓长、叶数、CCI、氮素积累量的均值低于正常氮处理,根冠比和氮素生理利用效率的均值高于正常氮处理;2)不同品种(系)的地上干重、地上部干物质增加量、地下部干物质增加量、总干物质增加率、根冠比、根长、蔓长、叶数、氮素积累量和氮素生理利用效率的变异系数高于正常氮处理,且其增幅排序为地上干物质增加量>总干物质增加率>地下干物质增加量>叶数>地上干重>氮素生理利用效率>氮积累量>根长>根冠比>蔓长;3)对11个指标的耐低氮胁迫指数进行主成分分析,3个主成分的累计方差贡献率达到72.67%,计算综合评价值Y;4)地上干重、地上部干物质增加量、地下部干物质增加量、总干物质增加率、叶数、蔓长、根长、根冠比、氮积累量、氮素生理利用效率的耐低氮胁迫指数与Y值的相关性达到极显著水平(P<0.01),其中,地上部干物质增加量、地下部干物质增加量、总干物质增加率、氮积累量和地上干重5项耐低氮胁迫指数的相关性较高,相关系数分别为0.85、0.86、0.81、0.79和0.73;5)建立Y值回归方程,选定耐低氮能力评价的8个指标,并进行系统聚类,划分甘薯基因型为耐低氮型、中间型、不耐低氮型3类;并对3种耐低氮甘薯类型的农艺性状和氮效率性状进行方差分析。【结论】地上干重、地上部干物质增加量,地下部干物质增加量、根长、蔓长、叶数、氮素积累量和氮素生理利用效率作为甘薯耐低氮能力评价的指标;13104-2/紫薯1号、宜宾红心薯、浙紫薯2号、渝紫3号、渝紫6号、漯紫1号和渝紫香10号7个为耐低氮型甘薯品种;耐低氮型品种的各性状表现好于中间型和不耐低氮型,其中,地上干重、地上部干物质增加量、地下部干物质增加量、蔓长和氮积累量差异显著。

新疆春小麦品种氮效率类型的鉴定

为给新疆氮高效春小麦品种筛选和合理施用氮肥提供理论依据,本研究以7个新疆主栽春小麦品种为材料,在田间试验条件下,采用4个氮水平处理(即不施氮N0:0 kg/hm^(2)的纯N;低氮LN:100 kg/hm^(2)的纯N;中氮MN:200 kg/hm^(2)的纯N;高氮HN:300 kg/hm^(2)的纯N),用主成分分析法比较了不同施氮水平处理下小麦9项性状指标(株高,穗长,叶面积指数,穗粒数,穗粒重,单位面积穗数, SPAD值,千粒重和产量)的差异,以此为依据划分各品种的氮效率类型。结果表明,不同性状的变异系数呈现出较大的差异,其中,叶面积指数(X3)、穗粒重(X5)、SPAD值(X7)和产量(X9)这4项指标在各性状指标均值方面达到显著水平。X4 (穗粒数)、X7 (SPAD值)和X9 (产量)这3项指标与新疆春小麦氮效率利用显著相关,可作为鉴定新疆春小麦品种氮效率类型的关键指标。依据各品种在不同施氮处理下氮效率利用的差异,可将7个新疆主栽春小麦品种分为氮高效型、低氮高效型、高氮高效型和氮低效型4种氮效率类型。其中,‘新春37’为氮高效型;‘新春43’和‘新春47’为氮低效型;‘核春614’和‘新春48’为低氮高效型;‘核春137’和‘核春615’为高氮高效型。本研究对新疆春小麦氮高效品种的选育和推广应用具有一定的参考价值。

几种豆科植物茶园间作的氮素协调性研究

以白三叶的铺地、考拉和紫花苜蓿的金达品种为材料,采用硝、铵氮素比为1∶1的水培液测定其喜氮类型,并测定不同生育时期的硝酸还原酶(NR)和谷氨酰胺合成酶(GS)活性。结果表明,三种豆科植物均有较强的喜硝特性,与喜铵的茶树间作具有氮素种类上的协调性。其中,以金达的总NR活性最高,GS活性最低,GS/NR值和吸氮量最小,最适宜茶园间作。

喀斯特地区野生枇杷种质对铵态氮的吸收及利用效率差异与评价

以贵州喀斯特地区22个野生枇杷(Eriobotrya japonica Lindl.)种质的实生幼苗为材料,采用土培和营养液培养方法,对不同铵态氮水平下各材料的株高、植株干重、氮含量、铵态氮吸收量及吸收效率、氮效率以及对NH+4的最大吸收速率(Imax)、表观米氏常数(Km)和NH+4流入根系的速率(α)进行测定,分析以上指标在种质间的差异及其相互作用和相关性,并划分不同野生枇杷种质的氮效率类型。结果表明:(1)实生幼苗的干重、铵态氮吸收量及氮效率在种质间和铵态氮水平间均存在显著差异,22个野生枇杷种质植株干重、氮含量、铵态氮吸收量、铵态氮吸收效率、氮效率变异系数(CV)在高氮和低氮水平下分别为21.09%和16.87%、17.06%和20.00%、36.67%和40.21%、36.71%和40.24%、21.05%和19.21%;不同野生枇杷种质对NH+4吸收动力学参数的差异也极为显著,Imax、Km、α值的CV在高氮和低氮水平下分别达到44.64%和60.00%、73.53%和81.48%、89.58%和109.18%。(2)上述所有指标在种质间和铵态氮水平间的差异及其交互作用均达到极显著水平(P<0.01),22个野生枇杷种质实生苗的干重、氮含量、铵态氮吸收量及吸收效率、氮效率、NH+4的Imax和α值之间都表现出极显著正相关关系,Km与上述指标呈极显著负相关关系;在高氮和低氮水平下,铵态氮吸收效率对氮效率的直接通径系数最大(1.805和1.523),铵态氮的吸收效率对氮效率的直接贡献均大于氮含量和铵态氮吸收量。(3)22个野生枇杷种质可划分为双高效型、高氮高效型、低氮高效型和双低效型4种氮效率类型,分别包括7个、4个、2个和9个种质。研究发现,贵州喀斯特地区野生枇杷种质对铵态氮的吸收和利用效率存在显著差异,实生苗的干重、铵态氮吸收量、铵态氮吸收效率和氮效率均可作为枇杷氮高效种质评价和筛选指标。

新疆粳稻审定品种氮效率类型的鉴定

在田间试验条件下,对3个施氮水平下的6个新疆粳稻审定品种8项性状指标进行考查和分析,划分各品种的不同氮效率类型,为氮高效水稻品种的筛选和指标鉴定提供依据。在不同施氮水平下,对粳稻品种各性状的相对值进行描述性统计分析表明,不同性状的变异系数呈现出较大的差异;就各性状的平均值而言,叶面积指数和SPAD值在不同施氮水平间的差异达极显著水平;就氮效率综合值而言,不同施氮水平间因品种不同而表现出较大差异。依据品种在不同施氮水平下的氮效率综合值,将各品种划分为氮高效型、低氮高效型、高氮高效型和氮低效型4种氮效率类型。新稻41号为氮高效型;新稻36号和新稻45号为低氮高效型;新稻11号为高氮高效型;新稻44号和新稻47号为氮低效型。相关性分析表明,有效穗数、叶面积指数和SPAD值可作为新疆粳稻品种成熟期氮高效评价的关键鉴定指标。

Characteristics of Nitrogen and Phosphorus Losses in Different Crop Rotation Systems in the North of Erhai Lake Basin

[Objective] Nitrogen and phosphorus losses of surface runoff in various crop rotation systems in the north of Erhai Lake basin were studied with the objective to provide references for risk evaluation of environmental pollution and formulating countermeasures to control the nonpoint source pollution from agriculture.[Method] Water samples collected in four typical crop rotation systems distributed in seven towns（townships） in the north of Erhai Lake basin were investigated,as well as the fertilizer input,to explore the dynamic change of nitrogen and phosphorus content in surface water of farmland and ditch water,and the correlation between fertilizer input and the concentrations of nitrogen and phosphorus in the surface water of farmland and in the ditch water.[Result] The results showed that nitrogen loss in surface water of farmland in different crop rotation systems differed greatly,and the risk of nitrogen loss was 38% lower in broad bean-rice crop rotation than that in garlic-rice crop rotation.The water soluble nitrogen was the primary form of nitrogen loss.The content of water soluble nitrogen was significantly higher in garlic-rice crop rotation than that in the other rotation systems,and the concentrations of nitrogen in the surface water of farmland in different crop rotation systems followed the sequence below：garlic-rice crop rotationryegrass-rice crop rotationbroad bean-rice crop rotationrape-rice crop rotation.The loss of phosphorus in the surface water of farmland was relatively low and phosphorus combined with silt was the primary form for phosphorus loss.There was no significant difference of the loss of various forms of phosphorus in different crop rotation systems.The contents of total nitrogen and total phosphorus in the surface water of farmland were higher than that in ditch water,with increasing rates of total nitrogen and total phosphorus in ditch water of 72% and 82%,respectively.Topdressing was the critical reason for the high concentrations of nitrogen and phosphorus in the surface water,which also caused the increasing load to the ditch water.[Conclusion] Both the nitrogen and phosphorus loss were the highest in garlic-rice crop rotation.Reasonable crop rotation systems should be established based on both the environmental and economic benefits.This study provided references for controlling the nonpoint source pollution of farmland and improving the water quality of Erhai Lake.

Nitrogen removal by three types of bioretention columns under wetting and drying regimes

The behaviors of inorganic nitrogen species in three types of bioretention columns under an intermittently wetting regime were investigated. The mean NH+4—N, NO-3—N and total N(TN) removal efficiencies for the conventional bioretention column(Col. T1) are 71%, 1% and 41%, for layered bioretention column with less permeable soil layer(Col. T2) the efficiencies are 83%, 84% and 82%, and for the bioretention column with submerged zone(Col. T3) the values are 63%, 31% and 53%, respectively. The best nitrogen removal is obtained using Col. T2 with relatively low infiltration rate. Adsorption during runoff dosing and nitrification during the drying period are the primary NH+4—N removal pathways. Less permeable soil and the elevated outlet promote the formation of anoxic conditions. 30%–70% of NO-3—N applied to columns in a single repetition is denitrified during the draining period, suggesting that the draining period is an important timeframe for the removal of NO-3—N. Infiltration rate controls the contact time with media during the draining periods, greatly influencing the NO-3—N removal effects. Bioretention systems with infiltration rate ranging from 3 to 7 cm/h have a great potential to remove NO-3—N.

Ammonia Volatilization from Soils Fertilized with Different Nitrogen Type and Application Method in Germination and Early Seedling Stages from the Radish Field

Ammonia volatilization(AV) from basal fertilizer with different nitrogen(N) types and application methods was investigated by the ventilation method in germination and early seedling stages during radish growth seasons in 2014. Four N fertilizer types, urea(U), ammonium bicarbonate(AB), ammonia sulfate(AS), and controlled urea formaldehyde(CUF) were applied through 5 cm depth placement(I) and 10 cm depth placement(II). The results showed that the N fertilizer type was the main factor that caused AV loss in germination and early seedling stages from the radish field. The highest and the lowest cumulative AV losses in germination and early seedling stages from the radish fields were 33.23 and 11.21 N kg/hm^2 for the treatments of AB+I and CUF+II, respectively, accounting for 60.40 and 26.40% of the N application for each treatment. The 10 cm deep placement of N reduced AV rates and lagged the AV process, and CUF significantly reduced ammonia volatilization. The data showed that the suitable N fertilizer type and application method for basal fertilizer were CUF and deep placement, respectively.Therefore, fertilizing with proper N fertilizer types and methods should be the efficient measures to mitigate AV losses from the radish field and will alleviate environment problems.

Effect of Simulated N Deposition on Soil Exchangeable Cations in Three Forest Types of Subtropical China

The effects of simulated nitrogen(N)deposition on soil exchangeable cations were studied in three forest types of subtropical China.Four N treatments with three replications were designed for the monsoon evergreen broadleaf forest (mature forest):control(0 kg N ha-1 year-1),low N(50 kg N ha-1 year-1),medium N(100 kg N ha-1 year-1)and high N(150 kg N ha-1 year-1),and only three treatments(i.e.,control,low N,medium N)were established for the pine and mixed forests.Nitrogen had been applied continuously for 26 months before the measurement.The mature forest responded more rapidly and intensively to N additions than the pine and mixed forests,and exhibited some significant negative symptoms,e.g.,soil acidification,Al mobilization and leaching of base cations from soil.The pine and mixed forests responded slowly to N additions and exhibited no significant response of soil cations.Response of soil exchangeable cations to N deposition varied in the forests of subtropical China,depending on soil N status and land-use history.

水热条件与天然草地地上初级净生物量及营养动态关系研究

天然羊草草地是内蒙古呼伦贝尔草原、科尔沁草原和东北松嫩草原的主要建群草地。10年定位观察表明，天然羊草草地地上初级净生物量受气象条件的制约，水分条件是主要限制因子。牧草属碳氮营养类型，适宜发展毛肉兼用型细毛绵羊和乳、皮、肉兼用的家畜。7月下旬至8月上旬，青草营养丰富、草质优良，是打草贮存的最佳时间。

Difficultly Extractable Fixed Ammonium in Some Soilsof China

Ninety-three soil samples and 19 sedimentary rock samples collected from 21 provinces of China wereanalyzed for their contents of fixed ammonium and total N by Kjeldahl-HF method. Results showed thatamount of difficultly extractable fixed ammonium (the fixed ammonium that is not determinable by Kjeldahlprocedures commonly used for soils) in soils ranged from 0 to 202 mg kg--1. It was generally more than50 mg kg--1 in soils in Chanaii and Thrpan districts, Xinjiang, accounting for 3.2%~36.8% with an averageof 13.9% of the total N. For some Orthents derived from purple shale and purple sandstone in Sichuan andHunan provinces and Chao soils derived from secondary loess in Henan Province and Ningxia AutonomousRegion it was generally around 30 mg kg--1 , accounting for 4%~7% of the total soil N, and for most of therest of soils studied, with the exception of some subsoils, no or trace difficultly extractable fixed ammoniumcould be detected. It was suggested that the difficultly extractable fixed ammonium was originated fromParent rock, and for slightly weathered soils derived from parent materials rich in this form of N the Kjeldahlmethod might give underestimation of total soil N.

Simulation Study on Purification Efficiency for Nitrogen in Different Types of Wetlands in Sanjiang Plain, China

The purification law of nitrogen in Deyeuxia angustifolia, Carex lasiocarpa and Deyeuxia angustifolia-Carex lasiocarpa combined wetland systems in the Sanjiang Plain, China was studied by field simulation experiment. The results indicate that the removal rates of TN, NH4^＋-N and NO3^--N in above three types of wetlands present an obvious logarithm growth trend along with the time. There are evident removal effects for NH4＋-N and NOa--N in water bodies of wetlands after the 30th day of experiment, with the removal rates over 80.0%, but the removal rate of TN is slightly low, being 63.1%-74.3%. NO3 -N is most quickly removed by the combined wetland, and NH4^＋-N by Deyeuxia angustifolia wetland. The removal speeds of TN by the three wetland systems are comparatively slow, of which the Deyeuxia angustifolia wetland is the fastest. In consideration of plant growth season, Deyeuxia angustifolia wetland has much more practical application value in purifying nitrogen. These results can provide references for the study on the purification function of wetlands and the control of non-point source pollution in Northeast China.

Actions of NO and INOS on Endotoxin Induced rat Acute Lung Injury and Effect of Rhubarb on Them

This study is to explore the actions of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) on endotoxin (lipopolysaccharide, LPS) induced rat acute lung injury (ALI) and effect of Rhubarb on them. LPS was injected into the sublingual vein of male Wistar rats to prepare ALI animal models. The rats were divided into 4 groups: LPS, control, Rhubarb, and dexamethasone. Macroscopic and histopathological examinations of the lung specimens were performed and the biological indexes of lung, including wet weight/dry weight, the rate of neutrophils and protein content in the pulmonary alveolar lavage fluid, pulmonary vascular permeability and pulmonary alveolar permeability were observed. In the mean time, the contents of serum NO and the activities of lung tissue homogenate iNOS were measured. The results showed that in the LPS group, the injury and celluar infiltration in the pulmonary stroma and alveoli were more prominent than that in the control group. Lung wet weight/dry weight, the rate of neutrophils, protein content, pulmonary alveolar permeability, pulmonary vascular permeability were significantly increased (P<0.01); NO and iNOS were also markedly elevated (P<0.01). In the groups of dexamethasone and Rhubarb, the histopathological changes were significantly milder, and all the above biological indexes of lung injury and the contents of NO and the activities of iNOS were correspondingly decreased (P<0.05). The above data demonstrate that NO and the activities of iNOS play an important role in the onset of ALI; dexamethasone and Rhubarb interfering treatment can ameliorate lung injury and decrease the concentrations of NO and iNOS, showing that through inhibiting the levels of NO and the activities of iNOS, these 2 agents exert protective effect on ALI induced LPS.

Soil organic carbon pool along different altitudinal level in the Sygera Mountains, Tibetan Plateau

Labile organic carbon（LOC） is one of the most important indicators of soil organic matter quality and dynamics elevation and plays important function in the Tibetan Plateau climate. However, it is unknown what the sources and causes of LOC contamination are. In this study, soil organic carbon（SOC）, total nitrogen（TN）, microbial biomass carbon（MBC）, microbial biomass nitrogen（MBN） and LOC were analyzed based on different soil horizons and elevations using turnover time in an experimental site（3700 m to 4300 m area） in Sygera. SOC and LOC in higher-elevation vegetation types were higher than that of in lower-elevation vegetation types. Our results presented that the soil microbial biomass carbon（SMBC） and soil microbial biomass nitrogen（SMBN）were positively correlated with SOC. The content of easily oxidized carbon（EOC）, particulate organic carbon（POC） and light fraction organic carbon（LFOC） decreased with depth increasing and the content were the lowest in the 60 cm to 100 cm depth.The total SOC, ROC and POC contents decreased with increasing soil horizons. The SOC, TN, MBC and MBN contents increased with increasing altitude in the Sygera Mountains. The MBC and MBN contents weredifferent with the changes of SOC（p＆lt;0.05）,meanwhile, both LFOC and POC were related to total SOC（p＆lt;0.05）. The physical and chemical properties of soil, including temperature, humidity, and altitude,were involved in the regulation of SOC, TN, MBC,MBN and LFOC contents in the Sygera Mountains,Tibetan Plateau.

Pore characterization of different types of coal from coal and gas outburst disaster sites using low temperature nitrogen adsorption approach

To characterize the pore features of outburst coal samples and investigate whether outburst coal has some unique features or not, one of the authors, working as the member of the State Coal Mine Safety Committee of China, sampled nine outburst coal samples(coal powder and block) from outburst disaster sites in underground coal mines in China, and then analyzed the pore and surface features of these samples using low temperature nitrogen adsorption tests. Test data show that outburst powder and block coal samples have similar properties in both pore size distribution and surface area. With increasing coal rank, the proportion of micropores increases, which results in a higher surface area. The Jiulishan samples are rich in micropores, and other tested samples contain mainly mesopores, macropores and fewer micropores. Both the unclosed hysteresis loop and force closed desorption phenomena are observed in all tested samples. The former can be attributed to the instability of the meniscus condensation in pores,interconnected pore features of coal and the potential existence of ink-bottle pores, and the latter can be attributed to the non-rigid structure of coal and the gas affinity of coal.

Effect of Nutrient Type on Chemical Composition and Dry Matter Partitioning of Cassava （Manihot esculenta Crantz）

The objective of our study was to determine the effects of four types of fertilisers enrichments （manure potassic （K）, phosphatic （P）, phosphatic and potassic （PK） and nitrogenized, phosphated and potassic （NPK）） on chemical composition and dry matter in cassava （Manihot esculenta） organs （clone 1171） during harvest period. The pots experiment was laid out in randomised complete bloc design with five treatments and four replications. Water, nitrogen, potassium, phosphorus, sodium, total proteins and total lipids contents of the leaves, shoots and tubers were determined. After 9 months growing period, results showed that fertilizer types enriched with K, PK and NPK significantly increased the organic compounds contents of the leaves （P〈0.05）. Furthermore, fertilizers with high phosphorus content significantly increased the lipid contents of the leaves （25%）. Fertilizers enriched with NPK positively influenced the biomass partitioning in Manihot esculenta. Application of fertilizers enriched with NPK led to higher levels of total proteins in the leaves and tubers （70 mg g DM^-1 and 30 mg g DM^-1 respectively） compared to control （17 mg g DM^-1 and 9 mg g DM^-1 respectively）. These results help to demonstrate the value of these fertilizers enrichment to improve the chemical composition and dry matter partitioning of cassava.

黄淮海中南部玉米氮高效品种筛选及产量性状分析

以40个玉米品种为研究对象,采用田间试验方法,对10个重要性状在2个供氮水平(高氮水平270kg/hm;低氮水平,不施氮)进行调查、计算和分析,对玉米氮效率类型进行划分和评价。结果表明,除穗行数外,其他9个性状在2个供氮水平上均存在极显著差异。相关分析表明,在2个供氮水平下,子粒产量与干物质积累量、穗长、行粒数、穗粒数、百粒重和单穗粒重均呈显著正相关。通径分析表明,在低氮水平下,对子粒产量直接作用较大的性状依次为穗粒数>百粒重>单穗粒重>行粒数;在高氮水平下,依次为单穗粒重>穗粒数>行粒数>百粒重。根据2个供氮水平下的子粒产量,将供试玉米品种分为4种类型,即双高效型、低氮高效型、高氮高效型和双低效型,分别占比30%、15%、27.5%和27.5%。

A Meta-analysis of the Effects of Organic and Inorganic Fertilizers on the Soil Microbial Community

In order to investigate the general tendency of soil microbial community responses to fertilizers, a meta-analysis approach was used to synthesise observations on the effects of inorganic and organic fertilizer addition(N: nitrogen;P: phosphorus;NP: nitrogen and phosphorus;PK: phosphorus and potassium;NPK: nitrogen, phosphorus and potassium;OF: organic fertilizer;OF+NPK: organic fertilizer plus NPK) on soil microbial communities. Among the various studies, PK, NPK, OF and OF+NPK addition increased total phospholipid fatty acid(PLFA) by 52.0%, 19.5%, 334.3% and 58.3%, respectively;while NP, OF and OF+NPK addition increased fungi by 5.6%, 21.0% and 8.2%, respectively. NP, NPK and OF addition increased bacteria by 6.4%, 9.8% and 13.3%, respectively;while NP and NPK addition increased actinomycetes by 7.0% and 14.8%, respectively. Addition of ammonium nitrate rather than urea decreased gram-negative bacteria(G–). N addition increased total PLFA、bacteria and actinomycetes in croplands, but decreased fungi and bacteria in forests, and the F/B ratio in grasslands. NPK addition increased total PLFA in forests but not in croplands. The N addition rate was positively correlated with the effects of N addition on gram-positive bacteria(G+) and G–. Therefore, different fertilizers appear to have different effects on the soil microbial community. Organic fertilizers can have a greater positive effect on the soil microbial community than inorganic fertilizers. The effects of fertilizers on the soil microbial community varied with ecosystem types. The effect of N addition on the soil microbial community was related to both the forms of nitrogen that were added and the nitrogen addition rate.