南亚热带不同母质发育土壤团聚体特征及其稳定性

团聚体是土壤的基本结构单位,其稳定性是评价土壤质量的重要指标。以南亚热带地区不同母质(石灰岩、第四纪红黏土、砂页岩)发育的土壤作为研究对象,采用湿筛法和LB法测定不同母质发育土壤团聚体稳定性特征。结果表明:(1)随着土层深度的增加,土壤容重呈上升趋势,而孔隙度、有机质和游离氧化铁含量呈下降趋势。砂页岩母质发育的土壤有机质含量最高,为22.44～42.97 g/kg。石灰岩和第四纪红黏土母质发育的土壤以黏粒(40.93%,42.51%)和粉粒(41.69%,42.31%)为主,砂页岩母质发育的土壤黏粒含量最低,为33.79%。(2)经湿筛法处理后,石灰岩母质发育土壤水稳性团聚体含量为91.58%～92.31%,第四纪红黏土母质发育土壤水稳性团聚体含量为76.45%～90.80%,砂页岩母质发育土壤水稳性团聚体含量为79.18%～86.67%,3种土壤团聚体的稳定性都随着土层深度增加而降低。(3)LB法处理后土壤团聚体MWD值均表现为慢速湿润处理预湿润振荡处理快速湿润处理,砂页岩母质发育的40—60 cm土层对消散和机械破碎作用最为敏感,其相对消散指数RSI和相对机械破碎指数RMI分别为0.78和0.42。不同母质土壤团聚体稳定性均与黏粒、有机质、游离态铁含量呈正相关。     

多功能调理剂对甘肃河西内陆盐渍土理化性质和甜高粱产草量的影响

在甘肃河西内陆的盐渍土上,采用田间试验方法,研究了多功能调理剂对盐渍土理化性质和甜高粱产草量的影响。结果表明:多功能调理剂最佳配方组合为:A2B2C1(即营养因子1.80 t/hm~2、有机生态肥72 t/hm~2、盐渍土改良材料1.20 t/hm~2)。不同种类盐渍土改良剂对盐渍土体积质量、pH、EC和全盐由大到小的变化顺序依次为:盐渍土荒滩(CK)抗盐丰盐碱土改良剂禾康盐碱土改良剂盐碱土改良剂多功能调理剂;总孔隙度、团聚体、饱和持水量、有机质、速效氮磷钾、甜高粱产草量由大到小的变化顺序依次为:多功能调理剂盐碱土改良剂禾康盐碱土改良剂抗盐丰盐碱土改良剂盐渍土荒滩(CK)。多功能调理剂与盐渍土荒滩(CK)比较,盐渍土体积质量、pH和全盐分别降低28.05%、3.63%和62.16%;总孔隙度、团聚体和饱和持水量分别增加45.55%、45.55%和32.91%;有机质、碱解氮、速效磷和速效钾分别增加11.74%、145.01%、206.56%和13.35%;甜高粱产草量出苗率、株高、茎粗、单株鲜重和产草量分别增加123.69%、120.00%、105.29%、133.33%和181.13%。多功能调理剂施用量与盐渍土孔隙度、团聚体、持水量、有机质、速效氮磷钾、微生物数量、甜高粱产草量之间呈正相关关系,与体积质量、pH和全盐之间呈负相关关系。多功能调理剂施用量与甜高粱产草量间的回归方程为:y=32.64+0.5561x–0.0003x2,最佳施用量为75.00 t/hm~2,甜高粱产草量为72.66 t/hm~2。在盐渍土上施用多功能调理剂,有效地改良了盐渍土理化和生物学性质,降低了体积质量、pH、EC和全盐,增加了总孔隙度、团聚体、饱和持水量,提高了有机质及速效氮磷钾和甜高粱产草量。     

长期不同施肥对塿土团聚体胶结剂的影响

【目的】土壤团聚体是土壤结构的基本单元,其形成和稳定与土壤中各种胶结剂的胶结作用有关,而团聚体胶结剂受土壤管理措施的影响,其中不同的施肥量及施肥措施影响作物生长进而影响土壤团聚体的胶结剂。本研究利用冬小麦一夏玉米轮作体系中不同施肥模式的(?)土长期定位试验,通过研究不同施肥模式对团聚体胶结剂的影响探讨(?)土团聚体的形成和分布的机理。【方法】试验设不施肥(CK)、单施氮(N)、氮磷(NP)、氮钾(NK)、磷钾(PK)、氮磷钾(NPK)、秸秆还田与氮磷钾(SNPK)、有机肥与氮磷钾(M1NPK和M2NPK)配施共9个处理。于2011年冬小麦收获前和2013年冬小麦收获后测定土壤团聚体胶结剂包括真菌菌丝密度、五碳糖、六碳糖、碳酸钙、粘粒以及游离氧化铁铝。【结果】不同施肥处理显著影响土壤表层(0-10 cm)和亚表层(10-20 cm)土壤团聚体胶结剂的含量。在0-10 cm土层,长期秸秆还田、有机肥与化肥配施处理与CK相比均显著降低了土壤菌丝密度也降低了碳酸钙含量但显著提高了土壤五碳糖和六碳糖含量而对粘粒(M2NPK除外)、游离氧化铁以及游离氧化铝含量没有显著影响。长期施用氮磷化肥(NP、NPK)也显著提高了土壤五碳糖含量显著降低了碳酸钙含量,提高了粘粒含量,降低了土壤菌丝密度对六碳糖、游离氧化铁和游离氧化铝含量没有影响。N、NK、PK处理的土壤五碳糖含量显著提高粘粒和游离氧化铁含量也有所提高,但对菌丝(PK除外)、六碳糖、碳酸钙以及游离氧化铝含量没有影响。10-20 cm土层,长期秸秆还田、有机肥与化肥配施与CK相比也提高了五碳糖和六碳糖含量显著降低了土壤菌丝密度和游离氧化铝含量而碳酸钙、粘粒、游离氧化铁差异不显著。长期施用氮磷化肥显著提高了土壤五碳糖含量,降低了土壤菌丝密度以及游离氧化铝含量但是六碳糖、碳酸钙、粘粒、游离氧化铁含量与CK没有差异。长期不施氮或不施磷处理与CK相比土壤五碳糖、六碳糖、碳酸钙以及游离氧化铁的含量显著提高但游离氧化铝含量显著降低而对菌丝和粘粒含量没有影响。不同团聚体胶结剂与团聚体平均重量直径的线性相关分析表明机械稳定性团聚体平均重量直径与碳酸钙含量呈极显著正相关、与游离氧化铁显著正相关与五碳糖和六碳糖极显著负相关。水稳性团聚体平均重量直径分别与菌丝密度、碳酸钙极显著正相关,与游离氧化铁显著正相关与五碳糖达显著负相关。【结论】团聚体胶结剂与平均重量直径的多元逐步回归分析表明,碳酸钙是影响(?)土团聚体稳定性唯一显著的胶结剂。     

EDTA对污染土壤水稳团聚体Cu Zn Pb的解吸作用

采用湿筛-离心法将采集自谷里铜矿矿区周边的重金属污染土壤筛分成不同粒径的团聚体,并用EDTA对原土和各粒径组分进行淋洗,旨在为进一步对矿区周边环境修复及风险评价提供参考依据。结果显示,粘粒级（〈0.002mm）团聚体颗粒具有相对较高的有机质（OM）含量、阳离子交换量（CEC）、游离氧化铝含量（Ald）和游离氧化铁含量（Fed）。Cu和Zn在粘粒级团聚体颗粒含量最高,而Pb在砂粒级〉0.2mm团聚体颗粒含量最高。Cu、Zn和Pb3种重金属在不同粒径团聚体的解吸规律相似,均表现出在粘粒级和细粉沙级团聚体解吸率最高,而在砂粒级团聚体的解吸率最低,但砂粒级团聚体颗粒对解吸总量的贡献最大。3种金属中,Cu的解吸率（〉15%）和解吸速率最大,原土及不同粒径颗粒团聚体组分的Cu、Pb和Zn的EDTA解吸过程均出现快速增长再趋于平缓的两个阶段,动力学模拟以Elovich方程描述最优。     

再生水灌溉模式对潮土结构性质及导水性能的影响

为揭示再生水不同灌溉模式下土壤结构性质及导水性能的差异。通过室内模拟土柱入渗试验,以清水灌溉为对照(CK),研究了再生水持续灌溉(RW)、再生水—清水混合灌溉(RW-2)及再生水—清水交替灌溉(ARW)3种灌溉模式对土壤容重、总孔隙度、团聚体稳定性、入渗率及饱和导水率的影响。结果表明:相比CK,各处理容重呈降低趋势,总孔隙度增加,但差异均不显著;再生水灌溉促进潮土>1mm粒级团聚体向<1mm粒级团聚体转化,相比CK,各处理<1mm粒级团聚体含量分别增长11.51%~31.22%;潮土团聚体水稳定性降低;各处理>0.25mm粒级团聚体含量分别降低2.92%~9.75%,平均质量直径分别降低11.30%~38.38%,几何平均直径分别降低3.93%~12.78%,其中RW最为显著;相关性分析表明,>1mm粒级水稳性团聚体含量对潮土结构稳定性贡献最大;再生水3种灌溉模式下潮土入渗率分别显著增长80.00%~260.00%;ARW处理潮土有效导水率上升22.68%,而RW和RW-2处理土壤有效导水率分别下降14.47%和42.36%。保持潮土结构性质方面以RW-2处理最好,改善潮土导水能力方面则以ARW处理最为显著。     

黄土丘陵区典型草地土壤有机碳及微生物量碳的分布特征

对黄土丘陵区植被恢复中柳枝稷、长芒草和白羊草这3种典型草地土壤有机碳、微生物量碳以及团聚体中有机碳的含量变化和分布特征进行了研究。结果表明,土壤中有机碳、微生物量碳以及不同粒级团聚体中有机碳均集中分布在土壤的表层;不同草地类型下有机碳的含量大小顺序为:柳枝稷草地>长芒草草地>白羊草草地;相同土层深度土壤各粒级团聚体中有机碳的分布表现为2～1mm粒级团聚体中有机碳含量明显高于其它粒级中有机碳的含量;在3种典型草地中,柳枝稷草地土壤中有机碳含量和团聚体中有机碳含量高于长芒草和白羊草草地的含量,柳枝稷草地土壤微生物量碳的含量仅低于长芒草中的含量。     

Wet aggregate stability as affected by excess carbonate and other soil properties

Aggregate stability is a fundamental property influencing soil erodibility and hydraulic characteristics. Knowledge of soil components controlling aggregate stability is very important to soil structure conservation. The objective of this study, which was carried out in surface soils from central Greece, was to relate wet aggregate stability to selected soil properties, with emphasis on excessive free carbonate content. The wet‐sieving technique of air‐dried aggregates was used for structural stability evaluation, according to a test that calculates an instability index. The soils studied were developed on Tertiary marly parent material and ranged in calcium carbonate content from 5 to 641 g kg⁻¹. From the texture analysis before and after removal of carbonates, it was concluded that carbonates mainly contributed to total silt and sand fractions, that is to the mechanical fractions which, as a rule, negatively affect aggregate stability. The results of the correlation analysis showed that aggregate stability was positively affected by aluminosilicate clay content, cation exchange capacity (CEC) and Al‐containing sesquioxides. Clay fraction from carbonates and total sand and silt negatively affected aggregate stability. CEC has been proved a very significant determinant of aggregate stability, which in a hyperbolic form relationship with instability index explained 78·9 per cent of aggregate stability variation. Copyright © 2011 John Wiley & Sons, Ltd.     

Changes in the physical properties of soils in the Kamennaya Steppe under the impact of shelterbelts

The physical properties of ordinary chernozems and meadow-chernozemic soils under different land management practices (maple, larch, birch, and pine sections of the shelterbelts; continuous (since 1959) fallow; and arable field (since 1952)) were studied in the Kamennaya Steppe. The soils had favorable physicochemical properties, light clayey texture, and high microaggregation independently from the type of land management. The long-term impact of the shelterbelts improved the soil structure in the upper part of the humus horizon: the content of agronomically valuable aggregates increased, the content of coarse aggregates (>10 mm) decreased, the aggregation coefficient increased by 3.7–4.3 times, and the water stability of the aggregates became by 8–12% higher. The soils under the shelterbelts were characterized by minimum values of the bulk density and solid phase density and by maximum values of the total, active, and air porosities. At the same time, no considerable differences between water reserves in the studied range of soils were detected. The ratio of the optimum productive water range to the active (productive) water range (OPWR/AWR) within the upper soil meter varied from 0.42–0.44 to 0.45–0.54. This points to changes in the character of perched water: the content of intra-aggregate capillary-perched water decreases, and content of film perched water increases down the soil profile.     

Effects of grazing on soil physical properties and soil erodibility in semiarid grassland of the Northern Loess Plateau (China)

Grazing animals provide a livelihood for farmers, but they may also produce adverse environmental effects. We investigated whether grazing leads to deterioration of soil physical properties that subsequently increases topsoil erodibility. We sampled three sites (an ungrazed grassland, a continuously grazed grassland, and a track trampled by stock) on the northern Loess Plateau of China. The bulk density, water content, proportion of stable aggregates, infiltration rate, and resistance to scouring were determined for each soil sample. The results showed that the track had the highest soil bulk density and the lowest soil water content, proportion of stable aggregates, infiltration rate, and ability to resist scouring. The ungrazed plots had the best results for these parameters, in terms of reduced erosion. Soil bulk density and the proportion of stable aggregates differed significantly with depth beneath the track. However, the effect of depth on water content, infiltration rate, and the soil resistance to scouring was not significant at any sampling site. The ability of the soil to resist scouring was negatively correlated with the soil's bulk density and positively correlated with the soil's water content, infiltration rate, and proportion of stable aggregates. Thus, soil physical properties played an important role in determining soil erodibility. Grazing and trampling by livestock therefore appear to cause deterioration of soil physical properties and to increase soil erodibility.     

Influence of calcium carbonate on mean weight diameter of soil

Lime influences on soil structure and water stability of aggregates are vague and inconsistent. An understanding of the mechanism involved is needed for better management of soil structure. Calcium carbonate was added to soil samples from the BC horizon of two Mollisols to bring the calcium carbonate content to 0, 2, 4, 8, 16 and 32% on a dry weight basis. Increasing calcium carbonate content from 0 to 4% decreased the specific absorption rate of water but increased the mean weight diamter (MWD) of aggregates. Further increase in calcium carbonate content increased specific absorption rate and decreased MWD. Addition of calcium carbonate influenced porosity and pore size distribution of both subsoil samples. The rate of water absorption, and consequently the rate and extent of air-pressure build-up within aggregates, varied according to the variation in soil porosity and pore sizes. Variation in pressure build-up characteristics within aggregates influenced the disruption of aggregates in water to change the MWD. At any specific absorption rate, evacuation of air from aggregates prior to their immersion in water caused the MWD to be about 10 fold greater than their values when the aggregates were wetted in the presence of air.     

耕作与覆盖措施对黄土塬区春玉米田土壤水气传输的影响

  【目的】  良好的土壤物理和水力学性质是土壤肥力可持续的基础。研究黄土高原旱作农业区长期不同耕作、覆盖措施对土壤水气传输性质的影响,为黄土塬区可持续的农田管理提供参考。  【方法】  基于设在渭北旱塬始于2002年的田间定位试验,选取传统耕作 (CT)、传统耕作+秸秆覆盖 (TS)、传统耕作+地膜覆盖 (TP)、传统耕作+全膜覆盖 (TWP)、免耕 (NT)、免耕+秸秆覆盖 (NS)、免耕+地膜覆盖 (NP)、免耕+生草覆盖 (NG) 共8个处理。于2019年春玉米收获期采集剖面土样,对0—10、10—20、20—30和30—40 cm土层土壤质量含水量、容重、导气率、相对气体扩散率和饱和导水率进行测定与分析。  【结果】  与CT处理相比,TS处理显著增加了0—40 cm土壤平均质量含水量,降低了0—40 cm各层土壤导气率,增加了各层土壤相对气体扩散率,表层 (0—10 cm) 土壤饱和导水率显著降低了75.9%;TP处理收获期耕层 (0—20 cm) 土壤容重增加,土壤总孔隙度显著降低,在0—10 cm土层,土壤导气率显著提高了54.1%;TWP处理耕层土壤容重显著增加,土壤总孔隙度显著降低,剖面0—40 cm土壤导气率和饱和导水率分别平均增加了64.8%和111.2%,尤其是表层土壤导气率显著提高了99.5%。与NT处理相比,NS处理耕层土壤容重降低,总孔隙度增加,表层土壤质量含水量、相对气体扩散率和饱和导水率分别显著提高了14.8%、25.3%和446.4%;NP处理耕层土壤容重增加,总孔隙度降低,表层土壤质量含水量和饱和导水率分别显著增加3.5%和145.2%,土壤导气率显著降低33.7%;NG处理耕层土壤容重降低,总孔隙度增加,表层土壤质量含水量显著提高了11.3%,土壤相对气体扩散率显著降低了42.1%。相同覆盖条件下与传统耕作比较,免耕处理能够降低下层20—40 cm土壤容重,增加土壤总孔隙度,提高土壤持水性,虽然降低了表层0—10 cm土壤导气率,但提高了土壤相对气体扩散率和饱和导水率。  【结论】  免耕秸秆覆盖可降低耕层土壤容重,增加总孔隙度,并且显著提高耕层土壤相对气体扩散率和饱和导水率,增加下层土壤导气率,是免耕处理组中最佳处理。传统耕作全膜覆盖可提高耕层土壤导气率、相对气体扩散率和饱和导水率,是传统耕作组中最佳处理,可有效保持渭北旱塬良好的土壤水气传输能力。     

耕作方式对东北黑土坡耕地土壤物理性状及根系垂直分布的影响

为了明确耕作方式对东北薄层黑土坡耕地土壤物理性状以及玉米根系垂直分布的影响,该研究以东北薄层黑土坡耕地土壤为研究对象,设置免耕和翻耕2种耕作方式,研究耕作方式对不同坡位土壤水稳性团聚体粒径分布与稳定性、土壤容重、土壤孔隙度、土壤贯入阻力以及玉米根系在垂直方向主要分布深度的影响,并进一步探究各指标间的相互关系.结果表明,...     

麦茬复种饲料油菜对耕层土壤团聚体的影响

通过田间小区试验，研究了不同油菜种植密度与施氮肥对麦茬复种饲料油菜耕层（0～20cm）土壤颗粒组成、水稳性团聚体、微团聚体、粘粒分散率和团聚度的影响。试验结果表明，麦茬复种油菜能提高耕层土壤水稳性团聚体，改善土壤颗粒组成状况；与对照（CK）相比，耕层土壤粘粒分散率呈显著或极显著性降低，〈0．001mm的土壤团聚体破坏率和特征微团聚体比例（〈0．01mm／〉0．01mm）显著降低，而土壤团聚度在油菜苗期为降低趋势，收获期呈显著或极显著性增加，〉0．25mm的土壤团聚体百分含量除收获期的水稳性团聚体外均呈不显著性降低。复种油菜对土壤水稳性团聚体改善贡献高于土壤微团聚体。种植密度和施肥处理均能不同程度地影响和改变耕层土壤水稳性团聚体、微团聚体和粘粒分散率的含量，处理间规律性不强，差异性并不十分显著。说明麦茬复种饲料油菜对农田土壤肥力的改善和提高具有积极作用。     

不同利用方式和开垦年限下红壤水稳性团聚体及养分变化研究

本文就不同开垦年限下旱地、水田、菜园和荒地土壤水稳性团聚体、有机C和各养分的变化规律及其相互关系进行了研究.结果表明,荒地开垦为旱地、水田和菜园后,>5 mm的水稳性团聚体含量迅速下降,但随着利用年限的延长,>0.25 mm的水稳性团聚体总量呈增加趋势.旱地和菜园土壤有机C的积累速度高于全N,而水田土壤中全N和有机C含量同时迅速上升.土壤全P含量随开垦年限增加快速升高,但土壤K素淋失严重,随着熟化程度的提高而降低.红壤各粒级水稳性团聚体含量与有机C和全N含量之间均达到了显著相关关系,而与全P和全K间相关性不显著.可见,土壤团聚体稳定性程度保持在何种水平,主要取决于农田有机C库及N的平衡状况.     

大兴安岭重度火烧迹地不同林龄落叶松人工林土壤团聚体养分特征

[目的]为探寻大兴安岭重度火烧迹地植被恢复后不同林龄落叶松人工林下土壤团聚体养分含量与分布的变化。[方法]以大兴安岭1987年发生特大森林火灾形成的重度火烧迹地上分别在1989年、2000年、2010年种植的落叶松人工林(11,21,32年)作为研究对象,通过测定土壤团聚体各粒级有机碳、全氮、全磷、碱解氮、速效磷和速效钾的含量,开展土壤团聚体养分分布特征研究。[结果](1)在重度火烧迹地上不同林龄的落叶松人工林中,土壤各粒级团聚体有机碳、全氮、全磷、碱解氮和速效钾的含量均随着粒径的减小逐渐上升,<0.5 mm粒级含量最大。(2)随着落叶松人工林林龄的增长,土壤各粒级团聚体有机碳、全氮、全磷、碱解氮和速效磷含量均逐渐上升。32年落叶松人工林土壤团聚体有机碳、全氮、全磷、碱解氮和速效磷含量相较于11年落叶松人工林分别显著增加77.35%～130.24%,77.61%～143.36%,105.84%～147.98%,94.58%～155.96%,206.98%～537.09%(p<0.05)。21年落叶松人工林土壤各粒级团聚体有机碳含量高于11年落叶松人工林,但二者无明显差异。(...     

The capacity of soil particles for spontaneous formation of macroaggregates after a wetting-drying cycle

The capacity of soil particles for spontaneous formation of aggregates >0.25 mm was studied in a laboratory experiment. The particles from soil aggregates (3-1 mm) (initially aggregated particles, APs) and initially free particles (FPs) of <0.25 mm in size were isolated from the soddy-podzolic and chernozemic soils under fallow and from the arable soddy-podzolic soil. The aggregates of 3-1 mm were ground and passed through a 0.25-mm sieve. Then, the aggregates and free particles were poured with water and dried, and the content of the formed aggregates and their water stability were determined; in the samples from the arable soddy-podzolic soil, the organic carbon content was also determined in the newly formed aggregates. The FPs from the untilled soils formed almost no aggregates. At the same time, the APs from these soils manifested the ability for the spontaneous formation of aggregates, including water-stable aggregates. In the arable soddy-podzolic soil, on the contrary, both FPs and APs demonstrated the capacity for spontaneous self-organization into aggregates. The water stability of the self-organized aggregates from the arable soil was similar regardless of their source (APs or FPs). It was supposed that the ability of the FPs from the arable soil to form macroaggregates reflects the mechanical degradation of the aggregates in the soil: tillage results in the degradation of the aggregates, and the particles capable of spontaneously aggregation temporarily fall in the fraction of <0.25 mm. The water-stable aggregates produced from the APs or FPs of the arable soil contained more organic carbon (1.89%) in comparison with the water-stable aggregates separated from the initial 3- to 1-mm aggregates of this soil (1.31%).     

川西低山丘陵区植茶土壤团聚体矿质氮分布特征

研究植茶对土壤团聚体全氮和矿质氮的影响可为茶园土壤合理施用氮肥提供理论依据.通过野外调查和室内分析,研究不同茶树品种(福鼎大白、川茶3号、川农黄芽早和川沐217)对土壤团聚体中全氮和矿质氮含量的影响.结果 表明:(1)各植茶品种土壤团聚体含量随粒径减小呈先减小后增大的变化趋势,＞2 mm粒径团聚体含量显著高于其他粒径团...     

苎麻对红壤旱地土壤团聚体及其特性的影响

采用干、湿筛法研究了种植苎麻和花生对红壤旱地土壤团聚体及其特性的影响,并比较分析了土壤团聚体及土壤理化性质与地表径流和土壤侵蚀量的关系。结果表明:(1)与花生地相比,苎麻地有机质、田间持水量、总孔隙度、沙粒分别升高了28.44%,10.06%,5.65%和53.13%,土壤容重、粉粒和黏粒则分别降低了7.20%,14.85%和34.95%,均达显著性差异水平(p0.05)。(2)团聚体平均重量直径(MWD)、稳定性指数(ASI)显著升高(p0.01),苎麻地土壤团聚体稳定性优于花生地;(3)两处理均以0.25~1mm粒径团聚体保存几率最大,抗水蚀能力最强。(4)地表径流量和土壤侵蚀量与土壤有机质、沙粒含量、1mm的干团聚体、0.5mm的水稳性团聚体、MWD以及ASI呈极显著负相关关系(p0.01),而与粉粒、黏粒、0.25mm干团聚体、0.053mm的水稳性团聚体、呈极显著正相关关系(p0.01)。     

Aggregate Stability and Its Relationship with Some ChemicalProperties of Red Soils in Subtropical China

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and A1 oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates,especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm.In addition, aggregate stability was positively and often significantly correlated with Fed, Ald, Feo and clay content, but significantly and negatively correlated to SOC.     

改良剂对复垦土壤团聚体组成及有机碳含量的影响

为探究改良剂对复垦土壤团聚体组成及有机碳含量的影响,采用田间微区的方法按表层0—20 cm土壤重量占比1%,3%,5%的比例添加泥炭、腐殖酸和蛭石,研究3种改良剂对复垦土壤团聚体组成、总有机碳、各粒级团聚体有机碳含量、土壤红外光谱特征的影响。结果表明:施用3种改良剂后各处理土壤机械稳定性团聚体均以>5 mm的最多,施用泥炭和腐殖酸后>5 mm团聚体含量随着改良剂施用比例的升高而增大,且MWD(平均质量直径)值均高于CK。其中,5%腐殖酸对调控>5 mm团聚体含量效果最佳,在6个月时>5 mm机械稳定性团聚体占比达到60.03%。而施用蛭石后>5 mm机械稳定性团聚体的占比与CK相比有所下降。施用3种改良剂后土壤水稳性团聚体以<0.053 mm团聚体含量最高,但其含量均随改良剂施用比例的升高而降低。泥炭和腐殖酸能够提高复垦土壤总有机碳的含量,增强抗侵蚀能力和团聚体的稳定性,而施用蛭石后有机碳含量减少。泥碳、腐殖酸和蛭石各处理下各粒级机械稳定性团聚体有机碳含量均以>5 mm最高,0.053~0.25 mm次之,<0.053 mm最少,有机碳含量贡献率也以>5 mm团聚体的最大,泥炭和腐殖酸处理下>5 mm团聚体有机碳含量贡献率均高于50%,<0.053 mm团聚体有机碳贡献率仅有0.63%~2.82%。从土壤的红外光谱特征峰可以看出,施用腐殖酸能够增加土壤中的多糖类物质,而多糖类物质有大量的—OH,能与黏粒矿物晶面上的氧原子形成氢键而把土粒团聚起来。