氮素富集对青藏高原高寒草甸土壤有机碳迁移和累积过程的影响

为深入揭示陆地生态系统碳固定对大气氮沉降增加的响应机理,基于海北高寒草甸多形态(NH4Cl、(NH4)2SO4、KNO3)、低剂量(N 0、10、20、40 kg hm-2a-1)的增氮控制试验平台,采集各处理水平下不同深度土壤样品,利用颗粒分组法分离测定总土壤有机碳(SOC)以及各粒径组分的碳含量和δ13C值。研究结果表明:低氮显著增加了土壤粗颗粒态有机碳(Macro POC)和矿质结合态有机碳(MAOC)的含量,而高氮处理正好相反。施氮一致降低土壤细颗粒态有机碳(Micro POC)含量。此外,添加硝态氮肥对SOC各组分含量和δ13C值的影响显著高于铵态氮肥。总体而言,低氮导致地表30 cm层SOC储量增加了4.5%,而中氮和高氮导致SOC储量分别下降了5.4%和8.8%。低氮处理时新增的碳以Macro POC为主,而高氮处理时损失的碳主要是Micro POC。连续5 a施氮促进了颗粒态有机碳(POC)组分的分解,进而导致SOC稳定组分的比例增加。可以认为,大气氮沉降或低剂量施氮(10 kg hm-2a-1)短期内有利于青藏高原高寒草甸土壤碳截留,硝态氮较铵态氮输入对土壤碳储量增加更为有益。     

有机肥与无机肥氮素平行施用对土壤硝态氮积累与玉米产量的影响

通过有机肥与无机肥对比定位试验,揭示氮肥肥效与硝态氮在土壤储存的一些规律。结果表明,有机氮肥能够实现作物高产,有机氮肥最高产量13092 kg hm-2、无机氮肥最高产量12773 kg hm-2。玉米作物产投比1.0时的最佳推荐施氮量有机氮为:252.72 kg hm-2、无机氮为:381.84 kg hm-2。施氮量在120～300 kg hm-2范围内,有机肥处理的土壤硝态氮储量高于无机氮处理。有机氮用量在80 kg hm-2以下,不会引起土壤硝态氮储量增加;无机氮用量在160 kg hm-2以下,不引起土壤硝态氮储量增加。     

温带针阔叶林土壤有机碳动态和微生物群落结构对有机氮添加的响应特征

森林生态系统土壤有机碳(soil organic carbon,SOC)转化和碳储量动态对大气氮沉降增加的响应是具有特异性的,取决于土壤初始氮状态、施氮类型、剂量与持续时间。过去相关研究主要集中在无机氮沉降效应方面,对有机氮沉降如何影响温带针阔混交林SOC及其组分含量尚不清楚,鲜有研究关注氮素富集条件下SOC变化的微生物学机制。以长白山温带针阔混交林为研究对象,设置4个尿素添加水平(0、40、80、120 kg·hm~(–2)·a~(–1),以N计,下同)的原位控制试验。施肥三年后,采集0～10 cm矿质层土壤样品,测定土壤不同形态氮含量、土壤团聚体比例和不同粒径SOC含量;利用磷脂脂肪酸(PLFA)技术测定土壤微生物不同种群相对丰度与群落结构,探讨SOC含量变化与微生物群落变化之间的相关关系。结果表明,施氮三年显著增加了土壤NO_3~--N、DON和TN含量,土壤酸化明显。施氮虽然未显著增加表层土壤总SOC含量,但是显著增加活性SOC组分(颗粒态有机碳和团聚体结合态有机碳)含量,增幅介于27.5%～96.3%,导致SOC组分发生累积的大气氮沉降临界负荷为80kg·hm~(–2)·a~(–1)以N计下同。SOC含量的变化(ΔSOC)与团聚体结合态有机碳、颗粒态有机碳含量的变化正相关。除好氧细菌丰度外,施氮总体上未改变微生物种群丰度,但是显著改变了微生物的群落结构,革兰氏阳性细菌/革兰氏阴性细菌(G+/G–)丰度比例增加而好氧/厌氧细菌(A/AN)丰度比例下降。有机氮富集倾向于促进温带针阔混交林土壤团聚体的形成,局域产生厌氧微环境,好氧/厌氧细菌(A/AN)丰度比例下降。活性SOC组分含量、土壤团聚体百分比和微生物PLFA丰度之间显著相关,暗示微生物群落结构与SOC积累和稳定之间关系密切。上述研究结果表明,氮素富集会改变温带针阔混交林土壤微生物群落结构,进而导致土壤碳积累。     

草甸草原土壤不同组分有机碳含量及化学结构对长期氮输入的响应

为探究长期氮输入对草甸草原土壤不同组分有机碳含量及化学结构影响，以内蒙古东北草甸草原为研究对象，于2010年设置0(CK)、30(N30)、50(N50)、100(N100)、150(N150)、200(N200)kg/(hm~2·a) 6个不同施氮水平处理，测定土壤不同组分有机碳含量及红外光谱特征。结果表明：(1)相比CK，长期氮输入条件下可提高土壤总有机碳(SOC)含量(增幅0.3%～13.6%)，且主要表现为颗粒有机碳(POC)含量的增加(9.22%～16.39%)，但降低土壤轻组有机碳(LOC)含量。(2)红外光谱主成分分析(PCA)结果表明，土壤LOC主要来源于脂肪碳、芳香碳、酚醇化合物，POC主要来源于芳香碳和酚醇化合物，矿物结合有机碳(MOC)主要来源于烷基碳和多糖。(3)相比CK，施氮处理凋落物和LOC官能团中烷氧碳(单糖+多糖)的相对强度降低，烷基碳、芳香碳相对强度增加；土壤POC和MOC官能团中烷氧碳、烷基碳及芳香碳相对强度增加，酚醇化合物相对强度降低；且施氮处理下凋落物及其不同土壤碳组分有机碳结构稳定性(芳香碳/脂肪碳)均高于CK。(4)结构方程模型(SEM)结果...     

深松施肥对黑土活性有机碳氮组分及酶活性的影响

探究不同深松深度下施肥后对黑土碳排放与活性碳氮组分的影响,在黑龙江省绥化市试验点开展为期两年的大田试验, 共设5个处理：免耕+单施化肥（T1）、深松25cm+单施化肥（T2）、深松25cm+化肥有机肥配施（T3）、深松35cm+单施化肥（T4）和深松35 cm +化肥有机肥配施（T5）处理,主要分析了各处理的土壤呼吸动态、有机碳（Soil organic carbon, SOC）与全氮（Total nitrogen, TN）、活性碳氮组分包括溶解性有机碳（Dissolved organic carbon, DOC）、微生物量碳（Microbial biomass carbon, MBC）、易氧化有机碳（Readily organic carbon, ROC）、颗粒有机碳（Particulate organic carbon, POC）和微生物量氮（Microbial biomass nitrogen , MBN）、颗粒有机氮（Particulate organic nitrogen, PON）与酶活性包括乙酰基β-葡萄糖胺酶（N-acetylglucosaminnidase, NAG）、纤维素酶（Cellobiohydrolase, CBH）、β-葡萄糖苷酶（β-glucosidase, BG）和木聚糖酶（β-xylosidase, BXYL）变化。结果表明：春玉米生育后期土壤呼吸速率逐渐下降,深松35cm（T4）显著提高碳排放36.82%,土壤温度与土壤呼吸呈极显著指数相关,免耕处理（T1）下土壤呼吸对土壤温度和水分变化最为敏感。深松、施肥及其交互作用均显著影响土壤活性碳氮组分,相对免耕（T1）处理,深松25cm（T2）显著降低MBC、POC、DOC 和PON含量20.49%、40.56%、7.94%和33.43%（P<0.05）,深松35cm（T4）显著降低SOC、MBC、POC、DOC、TN和PON含量9.44%、33.29%、77.62%、18.14%、14.60%和41.80%（P<0.05）;增施有机肥显著增加土壤碳氮组分含量,深松25cm时,有机无机配施（T3）相对单施化肥（T2）显著增加SOC、POC、ROC和PON含量8.37%、46.64%、35.10%和42.39%（P<0.05）;深松35cm时,有机无机配施（T5）相对单施化肥（T4）显著增加SOC、POC和PON含量8.45%、57.36%和44.83%（P<0.05）。深松25cm和深松35cm均显著降低土壤MBC/SOC、POC/SOC比例（P<0.05）,深松35CM显著降低PON/TN比例（P<0.05）,说明深松可以提高土壤碳氮稳定性。相对免耕处理（T1）,深松后（T2和T4处理）土壤NAG、CBH、BG和BXYL 酶活均没有显著差异,而增施有机肥（T3相对T2处理）显著提高了土壤CBH酶活性。综合来看,深松25cm下化肥有机肥配施处理（T3）的土壤碳氮库组分含量较高,且土壤呼吸碳排放量低于同等施肥下的深松35cm处理（T5）,T3处理更适宜在试验地区推广。     

内蒙农牧交错带地区土地利用方式和施肥对土壤碳库的影响

内蒙武川是我国典型的内蒙农牧交错带地区,土地利用方式转变和施肥是影响该地区农业生产和土壤碳储量的重要人类活动。选取内蒙武川地区,针对不同土地利用方式(耕地、退耕还林/还草)和施肥措施(化肥、有机肥)的长期定位试验土壤,分析土壤有机碳(SOC)、土壤无机碳(SIC)和全氮(TN)含量和储量,结合13C和15N稳定同位素方法,研究土地利用方式和施肥措施对于该地区土壤碳氮转化的影响规律。研究表明,退耕还灌/还草后,SOC储量较耕地均有显著提高(提高幅度0.60~0.98 Mg hm-2 a-1),SIC储量也增加或保持相同水平(柠条地除外)。相比不施肥处理,施用有机肥能显著增加SOC(1.08~1.19 Mg hm-2 a-1),施化肥处理则会降低SIC(0.06~0.16 Mg hm-2 a-1),且主要影响次生碳酸盐。施肥SIC中原生碳酸盐比例(0~23%)低于自然土壤(3%~29%)。施肥措施对于土壤碳氮的转化强度远大于土地利用方式的改变。对于内蒙等干旱半干旱地区土壤,土地利用和施肥措施对于土壤有机和无机碳的影响应该在区域固碳管理中给予全面考虑。     

施肥对设施菜地土壤硝态氮累积及pH的影响

在甘肃武威市设施栽培条件下,通过田间小区试验研究了不同施肥量及肥料种类（化肥、有机肥、有机＋无机）对设施土壤硝态氮累积、硝态氮在土壤剖面运移及土壤pH值变化的影响。结果表明：施氮量和肥料种类对土壤硝态氮的累积和淋溶均有较大的影响,随施氮量的增加,土壤剖面硝态氮累积量增加,其中对0～20cm土层硝态氮累积量的影响最为显著;在同等施氮量时,单施无机肥处理（NPK）、有机无机肥减半配施处理（1/2MNPK）、单施有机肥处理（M）,在40～150cm土层硝态氮的累积量分别为267.33、211.94、125.72kg.hm-2,表明只施用化肥较有机肥、有机肥与化肥配施更易造成土壤硝态氮淋溶并在深层累积。将农户习惯施肥量（MNPK）减半后施用（1/2MNPK）对蔬菜产量没有影响,并且显著减少了硝态氮在土壤中的累积,表明当地农户设施栽培肥料施用量过高,不仅造成肥料利用率低,栽培成本高,还可能给地下水位较浅的地区带来环境污染的风险。此外,土壤硝态氮含量与pH值呈极显著负相关关系,表明硝态氮在土壤中大量累积会造成土壤pH值的下降。     

长期不同施肥处理对土壤活性氮库的影响

通过长期肥料定位试验,对不同施肥处理下草甸黑土活性氮库中几种重要组分含量变化及其相互之间的比例关系进行研究.结果表明,氮肥施用能够增加土壤中无机氮含量,以土壤剖面中硝态氮含量变化为例,除NPK配施处理外,其它施氮处理在180-200 cm土层硝态氮含量均显著增加,N,.P,K配施减少了土壤剖面中硝态氮累积.土壤表层微生物态氮和固定态铵含量的变化不仅取决于氮素的投入量,还与其它因素有关,长期单纯施用氮肥土壤微生物氮含量并没有增高.而N,P配施的处理,土壤微生物氮含量较高.施用氮肥抑制了土壤中可矿化氮的含量,促进氮的矿化释放,增加了活性氮库中其它组分的含量;不同施肥处理表层土壤氮素矿化速率从高到低的顺序是:CKPKPKNPNPKNKN,不同施肥处理对硝化速率的影响大小按PCKKPKNPNPKNNK顺序排列.     

长期不同施肥模式对大麦-双季稻田根际土壤有机氮组分的影响

根际土壤有机氮组分在土壤养分和作物氮素营养中具有重要作用。本研究依托长期（37年）定位施肥试验田,设置4个施肥处理：不施肥对照（CK）、单独施用化肥（CF）、秸秆还田+化肥（RF）和30%有机肥+70%化肥（OM）,于晚稻成熟期测定大麦-双季稻田根际土壤基础理化性质、微生物量氮和有机氮组分（氨基酸态氮、氨基糖态氮、酸解氨态氮、酸解未知态氮、非酸解性氮）含量。研究表明：相对CK处理,RF和OM处理显著增加了稻田根际土壤有机碳、全氮、铵态氮和硝态氮的含量。RF和OM处理土壤微生物量氮含量分别比CK处理增加了19.8%和30.7%。酸解性氮作为根际土壤全氮的主体部分,占全氮的59.6%~72.1%;各处理根际土壤酸解性氮含量大小顺序表现为OM>RF>CF>CK。各施肥处理中,酸解有机氮中的氨基糖态氮、氨基酸态氮和酸解未知态氮含量均以OM处理最大,分别比CK处理增加139.3%、47.9%和110.0%;酸解氨态氮以RF处理最大,比CK处理增加69.9%。土壤有机碳、全氮、铵态氮、硝态氮与土壤氨基酸态氮、氨基糖态氮、酸解未知态氮以及微生物量氮均呈极显著（p<0.01）正相关。因此,秸秆、有机肥配施化肥均能有效提高大麦-双季稻田根际土壤的供氮能力,是改善稻田土壤肥力的有效手段。     

冻融对青藏高原高寒草甸土壤碳氮磷有效性的影响

以青藏高原高寒草甸土壤为研究对象,通过室内模拟冻融循环过程,研究不同土壤含水量条件下冻融频次和冻结温度对土壤碳氮磷有效性的影响。结果表明:(1)土壤可溶性氮(DTN)、硝态氮(NO-3-N)和有效磷(PO3-4-P)含量随冻融频次增加呈下降趋势,但铵态氮(NH+4-N)和可溶性磷(DTP)含量呈现上升趋势;(2)在冻融频次相同情况下,高含水量土壤在-15℃/5℃冻融循环处理下的可溶性有机碳(DOC)、DTN和NH+4-N含量显著高于-5℃/5℃冻融循环处理下的含量;(3)含水量高的土壤在冻融处理后,DOC、DTN、NH+4-N、DTP和有效磷(PO3-4-P)的含量通常高于含水量低的土壤,但NO-3-N则相反。由此可见,冻融频次、冻结温度和土壤含水量都是影响高寒草甸土壤冻融效应的关键因子,在评价冻融作用对高寒草甸土壤碳氮磷有效性影响时,还应充分考虑这些因子间交互效应。     

东北黑土活性有机碳、氮分布研究

通过对东北黑土区不同地点、不同层次的土壤样品的分析,探索活性有机碳(轻组有机C,N、颗粒有机C,N和易氧化有机C,N)在东北地区的分布情况。结果表明,随着纬度的增加,土壤活性有机C、N含量增加;随着深度的增加,土壤活性有机C、N含量减少。说明纬度低的地区,活性有机碳库转化较快,库容较小,而耕作措施相近的情况下,植物残体和根残体在有机C积累方面应予以重视。     

土壤团聚体的形成与分散及其在农业生产上的应用

土壤团聚体是保持土壤水分和土壤透性的基本单元.本综述的目的是通过围绕团聚体理论的讨论,明确影响团聚体形成的因素,为农田维护提出可靠的理论依据.首先总结了团聚体形成的主要理论,即Emerson的粘团理论、Edwards和Bremner的微团聚体理论和Oades 及Waters的团聚体分级构建理论,然后讨论了土壤有机质、可溶性阳离子和氧化铁、铝3个影响团聚体形成的主要因素,最后分析了团聚体破坏的机理和评价团聚体稳定性的主要方法,指出保持土壤颗粒的凝聚状态、增加各种形态的土壤有机质是增加土壤团聚性的主要措施.     

The quality of exogenous organic matter: short-term effects on soil physical properties and soil organic matter fractions

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased ( P  <   0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 × 10⁻³ m/s for the plots receiving organic amendments, compared with 0.34–0.43, and 0.42–0.64 × 10⁻³ m/s, respectively, for the unamended plots. There were significant differences between the organic amendments (P <  0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased ( P  <   0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98–1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092–0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased ( P  <   0.05), but there were no significant differences ( P  <   0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred.     

耕作对土壤有机物和土壤团聚体稳定性的影响

Agricultural sustainability relates directly to maintaining or enhancing soil quality. Soil quality studies in Canada during the 1980‘s showed that loss of soil organic matter (SOM) and soil aggregate stability was standard features of non-sustainable land management in agroecosystems. In this study total soil organic carbon (SOC), particulate organic matter (POM), POM-C as a percentage of total SOC, and aggregate stability were determined for three cultivated fields and three adjacent grassland fields to assess the impact of conventional agricultural management on soil quality. POM was investigated using solid-state ^13C nuclear magnetic resonance (NMR) to determine any qualitative differences that may be attributed to cultivation. Results show a highly significant loss in total SOC, POM and aggregate stability in the cultivated fields as compared to the grassland fields and a significant loss of POM-C as a percentage of total SOC.Integrated results of the NMR spectra of the POM show a loss in carbohydrate-C and an increase in aromatic-C in the cultivated fields, which translates to a loss of biological lability in the organic matter. Conventional cultivation decreased the quantity and quality of SOM and caused a loss in aggregate stability resulting in an overall decline in soil quality.     

Effects of hydrophobic and hydrophilic organic matter on the water repellency of model sandy soils

Soil water repellency affects the hydrological functions of soil systems. Water repellency is associated with the content and the composition of soil organic matter. In the present study, we examined the effects of hydrophobic and hydrophilic organic matter contents, the hydrophobic/hydrophilic organic matter ratio and the total organic matter content on water repellency using model sandy soils. Stearic acid and guar gum were used as the hydrophobic and hydrophilic organic compounds, respectively. Water repellency was estimated using the sessile drop method. Hydrophobic organic matter content was found to be the dominant factor affecting soil water repellency. Hydrophilic organic matter was found to increase the contact angle to some extent without the presence of hydrophobic organic matter. With the presence of both hydrophobic and hydrophilic organic matter, the effects of the hydrophilic organic matter content on contact angle were found to be dependent on the hydrophobic organic matter content of the soil. This relationship was explained by the differences in the surface free energies of different organic matter and mineral surfaces. The contact angle increased with increasing hydrophobic/hydrophilic organic matter ratio when the hydrophilic organic matter content was constant. When the hydrophobic organic matter content was constant, contact angles were roughly comparable, irrespective of the hydrophobic/hydrophilic organic matter ratio. The contact angles were not comparable at each total organic matter content. Accordingly, the hydrophobic/hydrophilic organic matter ratio and the total organic matter content in soil may not provide satisfactory information about soil water repellency.     

Long-term effects of straw and farmyard manure on crop yields and soil properties

The effect of cereal straw with added mineral N fertilization on crop yields, N uptake, total organic C content and hot water soluble C content in topsoil and on the relationships between organic C content in topsoil and organic matter balance was evaluated in a long-term field experiment established in 1966. The effect of straw plus mineral N fertilization was similar to the effect of farmyard manure (FYM) in the dry matter yields and also in the N uptake by plants. The effect of straw and mineral N fertilization on the organic C accumulation in soil was inferior to the effect of farmyard manure. Relationships between organic matter balance and total organic C content in the topsoil was positive and statistically significant. A favourable effect of mineral NPK fertilization on the C sequestration to soil was related to the effect of FYM fertilization.     

土壤中溶解性有机物及其影响因素研究进展

溶解性有机物(DOM)是陆地生态系统中极为活跃的有机组分,是土壤圈层与相关圈层(如生物圈、大气圈、水圈和岩石圈等)发生物质交换的重要形式。它不但是土壤微生物最重要的能量与物质来源,影响微生物的新陈代谢,而且对土壤营养元素(如C,N,P)和污染物的化学活性与生物活性也有直接影响。因此,土壤中溶解性有机物的消长动态已成为当前农业生态学领域的研究焦点问题之一。本文综述了土壤中溶解性有机物的迁移转化规律和主要影响因素,并指出未来的研究重点应在以下几个方面:(1)土壤有机质性质对DOM释放的影响。(2)有机质对DOM数量和质量的影响(3)生物和物理化学因素对土壤中DOM吸附和解吸的影响(4)DOC、DON和DOP迁移转化的差异。     

不同耕作制度对紫色水稻土活性有机质及碳库管理指数的影响

以长期定位试验点的紫色水稻土为研究对象，研究了耕作制度对紫色水稻土活性有机质和碳库管理指数的影响。结果表明：稻田长期垄作免耕0～10cm土层有机质含量比常规平作高，10～60cm土层有机质含量则比常规平作低；表明稻田长期垄作免耕土壤有机质具有表层富集现象；水旱轮作各土层有机质含量均比常规平作低。垄作免耕各土层活性有机质含量普遍增加，水旱轮作表层（0～10cm）活性有机质含量减少，其余土层变化不大。对活性有机质组分含量的研究表明：与常规平作相比，垄作免耕增加了土壤表层活性有机质各个组分的含量，在其余土层增加了低活性有机质含量，而减少了高活性有机质含量；水旱轮作增加了各土层低活性有机质含量而减少了中活性和高活性有机质含量。垄作免耕所有土层的碳库管理指数都在100以上，水旱轮作除表层（0～10cm）小于100以外，其余土层都在100以上。由此可见，农业管理措施对土壤有机质、活性有机质及碳库管理指数有较大影响。     

Labile and stable pools of organic matter in soil amended with sewage sludge biochar

One of the main advantages of using biochar for agricultural purposes is its ability to store carbon (C) in soil for a long-term. Studies of labile and stable fractions of soil organic matter (SOM) may be a good indicator of the dynamics of biochar in soils. This study evaluated the effects of applying sewage sludge biochar (SSB) in combination with mineral fertilizer on fractions of SOM. To conduct this evaluation, 15 Mg ha^?1 of SSB combined or not with mineral fertilizer (NPK) was applied to the soil in two cropping seasons. Apart from total organic C (TOC), the labile and stable fractions of SOM were also determined. The combined use of SSB and NPK resulted in higher TOC, a 22% to 40% increase compared to the control and to the NPK treatments, respectively. The SSB produced at a lower temperature increased the labile fractions of SOM, especially the microbial biomass C, showing its capacity to supply nutrients in the short-term. The stable pools of SOM are increased after adding SSB produced at a higher temperature. It was concluded that pyrolysis temperature is a key-factor that determines the potential of SSB to accumulate C in labile and stable fractions of SOM.     

Molecular composition and structure of organic matter in density fractions of soils amended with corn straw for five years

Corn straw is an important source of carbon (C),and when applied to soil,it alters the accumulation and distribution of organic C.However,the mechanistic pathways by which newly added C is stored and stabilized in soil remain a subject of interest and debate among scholars.In this study,we investigated the chemistry of organic matter in different density fractions of Haplic Cambisol (sandy clay loam) in a field experiment with corn straw at8 900 kg ha^-1year^-1under no tillag...