浅地下水埋深微域尺度苏打盐渍土的积盐机理探讨

通过野外定位观测和室内化验,探讨了浅埋地下水环境下苏打盐渍土的积盐机理。结果表明:在35×35m2大小的区域内,相对高差仅60cm,包括盐化草甸土、浅位柱状碱土、白盖苏打碱土和中位柱状碱土4种土壤类型。盐化草甸土分布在相对较低的洼地,几乎没有碱化层;白盖苏打碱土和中位柱状碱土分布在微坡地和高平地。高平地土壤的碱化层出现在15～30cm,碱化度(ESP)70%,微坡地土壤的ESP表层最大达75%。地下水位(初见水位)表现为洼地凸出的三维空间格局,洼地和高平地之间的地下水初见水位差达1m以上,24h后的水位基本保持在同一水平。地下水位在冻结期的变化与冻土的形成和发展有一定相关性。冻结期,部分浅埋地下水进入冻层,导致冻层含水率增加,同期地下水开始缓慢下降。盐化草甸土表层的含水率从冻结前的20%增加到50%(过饱和状态),其增量达到显著性水平(p<0·05);苏打碱土冻结层含水率有一定的变化,但变化程度不显著。冻融期间,苏打碱土表层含盐量迅速增加,其中白盖苏打碱土表层含盐量增量幅度达80%,而盐化草甸土表层的盐分含量变化不显著。     

长期施用有机肥对草甸碱土水稳性团聚体及其碳氮分配的影响

试验依托东北农业大学盐碱土长期定位试验站(始建于1995年),研究不同施肥年限下草甸碱土水稳性团聚体含量及其碳、氮分配规律。结果表明,长期施用有机肥可以显著增加0.25 mm水稳性团聚体的含量52.3%~60.8%,0.5~0.25 mm粒级的水稳性团聚体随着种植和有机肥施用年限的提高显著增加。施肥5年后,草甸碱土土壤团聚体中有机碳和全氮含量开始呈现稳中有升的趋势。大团聚体对有机碳和全氮的贡献率分别为47.9%~89.3%和52.9%~82.1%。5 mm和5~2 mm粒级的团聚体中有机碳和全氮含量与该粒级团聚体数量均呈显著性正相关。连续5年高量有机肥的投入,已经对草甸碱土培肥改良起到了显著效果,此后维持正常的施入量即可。     

长期施用有机肥对草甸碱土土壤酶活性及养分特征的影响

依托东北农业大学盐碱土改良长期定位试验站,以松嫩平原草甸碱土为研究对象,探讨不同年限有机培肥措施下草甸碱土酶活性变化趋势、有机质和养分提升状况及其相互关系。结果表明:长期施用有机肥,草甸碱土脲酶、蔗糖酶、磷酸酶活性含量均显著提高,长期施用有机肥对过氧化氢酶活性影响较小。草甸碱土有机质、全氮、全磷及碱解氮、有效磷含量均显著提高,土壤pH值显著降低。施用有机肥5年后,草甸碱土的改良效果显著。经相关分析,土壤脲酶、蔗糖酶、磷酸酶与土壤有机质和养分间呈显著或极显著正相关,过氧化氢酶则无显著相关性。     

苏打盐渍土的微域特征及土壤表层积盐机理探讨——以吉林省大安地区嫩江古河道碱滩地为例

通过野外定位观测和室内分析,探讨了苏打盐渍土微域尺度(32 m长的横截面)的土壤结构以及冻融期土壤表层积盐的机理。结果表明:高平地的地层剖面为粉砂质亚粘土-粘土-粉砂-砂砾质地结构;洼地以粉砂质为主,缺少粘土层。盐化草甸土表层的水分以毛管水为主,粗毛管孔隙占总孔隙度的70%以上;苏打碱土的水分主要为束缚水,含水率低且变化微弱。苏打碱土和盐化草甸土镶嵌的微域格局对土壤水分和盐分的迁移规律有明显的影响。冻融季节,盐化草甸土成为水分迁移的汇集区,其表层含水率达50%以上(达到过饱和状态);苏打碱土冻层的水分变化十分微弱,但是盐分含量显著增加并在消融期表聚,导致土壤的盐渍化程度不断加重。     

不同碱性条件对苏打盐碱土无机磷组分的影响

为了阐明不同碱性条件下苏打盐碱土无机磷各组分的含量及转化情况,通过室内模拟试验结合室内分析方法,以吉林省西部地区苏打草甸碱土为研究对象,对不同pH条件下土壤不同形态无机磷组分含量的动态变化进行了研究。结果表明,在一定范围内降低碱土pH值有利于增加土壤中Ca2-P、Fe-P、AlP及Ca8-P等形态磷的含量,其中pH值8.3处理比pH值9.2处理分别提高了44.8%,4.1%,45.9%,42.0%;比pH值10.2处理分别提高了81.5%,19.6%,39.3%,103.7%;O-P含量受土壤pH值的影响相对较小,改变土壤pH值短时期内不会导致其含量发生变化;Ca10-P的含量随着土壤中pH值的升高而增加,pH 10.2处理比pH 9.2处理和pH 8.3处理的Ca10-P含量分别提高15.6%和51.4%。研究表明,不同碱性条件可以影响土壤无机磷各组分之间的转化,碱土pH值降低有利于提高土壤中有效态磷组分的含量,但减少了潜在磷源的含量。     

施加脱硫石膏对盐碱土固碳的影响

增加陆地生态系统碳固定能力能有效缓解大气CO 2升高引起的温室效应。以干旱区典型盐土和碱土为研究对象,通过室内土柱模拟试验,研究不同施用量脱硫石膏(0,10,20,21.78,30,40 t/hm²)对盐土和碱土生态系统碳储量(包括土壤碳储量和生物量碳储量)的影响。结果表明:与对照相比,施加脱硫石膏盐土总碳储量(C)降低8.78%~15.72%,其中以土壤有机碳储量降低为主;碱土总碳储量(C)增加5.00%~23.94%,其中以土壤无机碳增加为主。脱硫石膏施加后盐土总生物量碳储量(C)较对照平均降低23.14%,碱土总生物量碳储量(C)较对照平均增加30.44%。施用脱硫石膏碱土生态系统碳储量(C)较对照增加0.09~0.42 kg/m²,而盐土生态系统碳储量(C)较对照降低0.33~0.56 kg/m²。相关分析结果表明,脱硫石膏施加量、土壤电导率以及由脱硫石膏施加引起的土壤含水量变化是影响盐碱土生态系统固碳的主要因素。总体上,施加脱硫石膏后,盐土生态系统碳储量显著降低,碱土生态系统碳储量显著增加,其中施加量30,40 t/hm²处理对盐碱土生态系统碳储量影响效果最大。研究结果可为增加干旱区生态系统碳固定提供科学参考。     

长期施用有机肥对草甸碱土碳库管理指数的影响

基于1995年在黑龙江省大庆市肇州县进行的长期定位试验,研究了长期施用有机肥对草甸碱土活性有机质和碳库管理指数的影响。采用3种浓度的KMnO₄(33,167,333mmol/L)氧化法测定了土壤高活性有机质、中活性有机质和活性有机质3部分含量。结果表明,长期施用有机肥能增加草甸碱土活性有机质各组分含量和碳库管理指数。活性有机质各组分含量和碳库管理指数在施用有机肥1~5a的处理间均呈上升的变化趋势,并与玉米产量趋势相一致,在施用有机肥第5a时,均达到最高值,施用有机肥5~16a的处理间,均呈现逐渐下降趋势,最终趋于稳定。中活性有机质和活性有机质与总有机质均达到极显著性正相关,而高活性有机质与总有机质无显著性相关,活性有机质各组分与碳库管理指数也均达到极显著性正相关。研究表明,总有机质不能很好地评价草甸碱土的土壤肥力,而中活性有机质、活性有机质和碳库管理指数能更为客观地反映草甸碱土的土壤肥力,可作为草甸碱土改良的良好评价指标。     

季节性冻融对扎龙湿地演化的影响

通过野外定位观测和室内分析,探讨了冻融季节扎龙湿地的物质迁移和转变规律.结果表明:季节性冻融对扎龙湿地的演化有有明显的影响.扎龙湿地在小尺度内常常表现为盐化沼泽土-碱化草甸土-浅位柱状碱土-白盖苏打碱土-风沙土的微域格局.不同土壤类型的温度特征和冻融过程都存在一定差异.芦苇沼泽的冻融时间长达9个多月,羊草草甸草原的冻融时间仅8个月左右,且芦苇沼泽的冻融深度比羊草草甸草原深24 cm.消融期间芦苇沼泽土的含水率变化不明显,而其它土壤类型的含水率都迅速减少.消融期间部分芦苇沼泽土表层的残积根层逐渐分解,使得表层的有机质增加幅度达55%,0-70 cm土层的总氮增加幅度达52.8%.     

黑龙江省西部草地土壤无机磷的形态

本文通过牧场试验，探讨了黑龙江省西部草地土壤无机磷形态，结果表明，四种草地土壤均以Ｃａ－Ｐ为主，约占无机磷总量的６０％左右，Ｏ－Ｐ含量少于Ｆｅ－Ｐ和Ａｌ－Ｐ．草甸黑钙土无机磷总量最高，Ｃａ２－Ｐ、Ｃａ８－Ｐ和Ａｌ－Ｐ都是草甸黑钙土重要的贮磷库；草甸风沙土无机磷总量最低，但Ｃａ８－Ｐ含量相对较高；草甸碱土无机磷总量、Ｃａ２－Ｐ和Ａｌ－Ｐ含量显著高于碱化草甸土．向草甸碱土和碱化草甸土施磷酸二铵能显著增加土壤无机磷的总量，尤其显著提高土壤中Ｃａ８－Ｐ和Ａｌ－Ｐ含量．     

科尔沁沙地农牧交错带土地利用方式对土壤特性的影响

以彰武县北部为样区，研究了科尔沁沙地农牧交错带不同土地利用方式对于土壤特性的影响。研究结果表明：草甸碱土草地开垦为早作农田后，土壤次生盐渍化加重；草甸草地开垦成为水田，则有利于对土壤次生盐渍化的防止和抑制；固沙林地或草地开垦成为农田，在一定的程度和范围会导致土壤养分含量特别是速效养分N含量显著降低，土壤颗粒的粗化（沙化），且这种趋势随着开垦年限的增加而加重。     

Bodengefüge gegen Verdichtungen schützen – Lösungsansätze für den Schutz landwirtschaftlich genutzter Böden

Protecting soil structure against compaction—proposed solutions to safeguard agricultural soils To safeguard the ecological soil functions and the functions linked to human activities, measures against harmful changes to the soil are required, in line with the precautionary principle. The German Federal Soil Protection Act sets obligations for precaution in agricultural land use and, if harmful changes to the soil are foreseeable, measures for averting a danger. The results of a research project of the Federal Environmental Agency show that it is possible to describe an impairment of the soil structure, using methods of soil analysis. But this as a sole information would not qualify for the identification of harmful changes to the soil in the context of the Soil Protection Act, which requires an assessment of the severity of disruption of soil functions and the respective subject of protection. This would make additional soil investigations on site mandatory. Approaches in agricultural engineering and soil physics have introduced procedures to preserve the soil structure, in accordance with the precautionary principle. But these procedures have different goals and different ranges of application and hence offer partial solutions to safeguard against soil compaction. The assessment model of “trafficability by measuring the rut depth” provides information about the compaction status of the soil under applied conditions for farming gear, without providing detailed information about affected soil layers. The soil‐physical model of classifying soils into “risk classes for harmful soil compaction” focuses on the relationship between topsoil compaction and crop yields. The soil‐physical models “precompression stress” and “loading ratio” provide information for the assessment of subsoil compaction and a prognosis of a possible impairment of the soil structure at the water content of field capacity. It is necessary to validate the individual models with additional regional data about soil structure before a final assessment of the prognoses is made.     

Soil Erodibility and Physicochemical Properties of Collapsing Gully Alluvial Fans in Southern China

In southern China, collapsing gully erosion produces massive deposits of sediment on the plough layer of alluvial fan farmland, leading to reduced nutrients, increased erodibility, and even desertification. The aim of this study was to investigate soil erodibility (the factor K in the universal Soil Loss Equation, USLE) and physicochemical properties of the alluvial fans of the most severe collapsing gully erosion areas (Hubei, Jiangxi, Fujian, and Guangdong provinces) in southern China. The soils of the collapsing gully alluvial fans had a higher bulk density, but a lower total porosity, saturated water content, and silt and clay fractions than the control (CK) soils from the farmland without desertification. Soil quality gradually decreased from fan edge to fanhead. Significant decreases were found in soil pH, organic matter, cation exchange capacity, and total potassium, nitrogen, and phosphorus, as well as available nitrogen, phosphorus, and potassium, resulting in a gradual decrease in soil nutrients from the fanedge to the fanhead. Soil erodibility was greatest in the fanhead, and soil erodibility K values of the alluvial fans were 53.71%, 66.28%, 67.53%, and 71.68 % greater than that in those of the CK soils of Hubei, Jiangxi, Fujian, and Guangdong, respectively, indicating a significant correlation between the soil erodibility K values and physicochemical properties, particularly sand fraction and organic matter content. The results provide new insights into the relationship between soil physicochemical properties and erodibility of alluvial fans, and suggest that improving soil structure might increase soil fertility in the collapsing gully alluvial fan farmland.     

Soil health – What should the doctor order?

The concept of soil health has been extensively reviewed in the scientific literature, but there is only patchy and inconsistent information available to farmers and growers who are concerned about the declining condition of their soils and are looking for appropriate test methods and management interventions to help reverse it. Although there are well‐established laboratory methods for soil chemical analysis, and a range of laboratory and field methods for measuring soil physical properties, only now are methods starting to emerge for soil biological analysis. This study provides an overview of the methods that are currently available commercially (or are close to commercialization) for farmers and growers in the UK. We examine the science underpinning the methods, the value of the information provided and how farmers and advisors can use results from such assessments for informed decision‐making in relation to soil management.     

土壤孔隙结构与土壤微环境和有机碳周转关系的研究进展

土壤结构是土壤功能的基础,不仅影响土壤养分的供应、水分的保持及渗透、气体的交换等过程,还为土壤微生物提供了物理生境,并调控土壤有机碳的周转这一关键过程。土壤的孔隙特征能够直接、真实地反映土壤结构的好坏;用土壤的孔隙特征作为试验指标能更好地反映土壤结构对这些过程的调节作用。在此基础上,将高度异质性的土壤孔隙结构同土壤微环境的变化和土壤有机碳的周转过程进行定量分析,对深入了解土壤结构在土壤生态系统中的功能至关重要。因此,着重从土壤孔隙结构对土壤微环境的影响及其与有机碳的关系两方面展开,剖析土壤孔隙结构调控作用下的土壤微环境响应过程,阐述土壤孔隙结构对土壤有机碳周转产生的直接、间接影响,强调土壤孔隙结构在调节土壤有机碳周转进程中的重要作用,并对土壤孔隙结构在调节土壤有机碳周转、植物残体分解及其与微生物协调作用机制等方面研究提出展望。     

土壤因子研究综述

介绍了国内外土壤因子的研究方法及研究成果,指出我国目前土壤因子研究中存在的问题,并结合我国土壤因子研究现状,认为继续土壤水蚀机理的研究是今后土壤因子研究的内容之一,同时,随着GIS和RS技术发展,应用GIS和RS技术研究区域土壤因子也将成为潮流。     

土壤润湿性受土壤特性及土地使用的影响

Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.     

设施栽培下原状土与扰动土水分特性的试验研究

以四川省双流县设施栽培土壤为研究对象,对其原状土与扰动土的土壤水分特征曲线、水分物理性质和比水容量等项目进行了研究。结果表明,扰动土水分特征曲线总体变化趋势与原状土较为一致。在低吸力阶段,相同吸力条件下扰动土含水量高于原状土,在高吸力阶段两者差异较小。扰动土毛管孔隙度、总孔度和凋萎含水量在剖面上的总体变化趋势与原状土较为一致。扰动土不同土层田间持水量和有效水含量差异较小,原状土的田间持水量和有效水含量均随土层加深而减少。在低吸力阶段,相同吸力条件下扰动土比水容量远高于原状土,但随土壤水吸力增加,扰动土比水容量变化趋势逐渐与原状土一致。     

植物苗期根系抗侵蚀特性试验研究——以构树和顶坛花椒为例

植物的固土抗蚀作用大小与其根系密切相关,而根系特征决定了根的固土抗蚀作用的发挥,本文以相同基质下构树和顶坛花椒不同特征的根系为研究对象.通过研究根系特征与土壤抗冲性、抗蚀性、抗拉性、紧实度的关系,结果表明,苗期根系能强化土壤抗冲性,构树苗、顶坛花椒苗根系强化值大小分别为78.01>77.71;根系可提高土壤抗蚀性,其抗蚀性强弱为.构树苗>顶坛花椒苗>对照,构树、顶坛花椒、对照试验的土壤水稳性指数分别为4.36,3.16,1.67;不同树种根系对土壤的固结能力不同,构树苗生长下的土壤抗拉能力为214.92 N,明显大于顶坛花椒苗生长下的土壤154.87 N;土壤紧实度大小为构树苗>顶坛花椒苗.并采用加权综合指数法综合评价了苗期不同特征植物根系的固土能力强弱,得出构树苗综合指数为1.058.而顶坛花椒苗为0.902.即构树苗的固土能力强于顶坛花椒,以期为今后的水土保持工作提供一定的理论依据.     

长期化肥有机替代对黑土颜色及腐殖物质的影响

基于30年长期定位试验,通过测定黑土光谱反射率和不同腐殖质组分含量,探究了不同施肥对黑土土壤腐殖质含量、土壤颜色及二者之间的关系。试验设置5个处理:(1)休耕(Fallow);(2)不施肥处理(CK);(3)单施化肥(NPK);(4)有机肥部分替代化肥(NPKM);(5)秸秆部分替代化肥处理(NPKS)。结果表明:与NPK处理相比,Fallow、NPKS、NPKM分别显著提高49.7%,74.3%,27.0%的土壤有机碳含量(p<0.05)。NPKM处理中胡敏酸(HA)含量最高为3.9 g/kg,随后依次为CK、NPKS、NPK、Fallow。NPKM、NPKS和Fallow处理中土壤富里酸(FA)含量为2.2~2.3 g/kg,显著高于NPK和CK。NPKM处理中胡敏素(HM)含量为18.6 g/kg,显著高于其他处理(p<0.05)。不同处理间土壤光谱反射率由高到低依次为NPK>Fallow、CK>NPKS>NPKM,与CK处理相比,NPK土壤光谱反射率在平均提高6.5%,NPKS和NPKM则分别降低11.1%和15.1%。根据线性相关分析结果,黑土土壤光谱反射率与土壤HAHM均呈显著负相关关系(p<0.01),相关系数(r)分别为-0.858,-0.681。综合上述结果,长期有机物料投入可以显著提高黑土腐殖物质含量,降低黑土光谱反射率,使黑土颜色加深,而长期化肥施入则使黑土光谱反射率提高,出现"褪色"现象,有机粪肥在黑土中对土壤有机质和腐殖质含量的提升效果优于秸秆。