基于水分特性的采煤沉陷地充填复垦黄河泥沙容重优选

为探究黄河泥沙容重与水分运动特征参数的关系,优选黄河泥沙充填复垦的最佳容重设计,运用土壤的概念和性质进行类比研究。根据不同容重条件下饱和含水率与饱和导水率的实测值、van Genuchten模型中进气吸力相关参数?和经验参数m的模拟值,分别建立经验模型,相关系数0.992~0.995(P0.01),决定系数0.938~0.990,理论值与实测值相对误差均控制在10.77%以内。研究结果:1)饱和含水率与饱和导水率均随黄河泥沙容重的增大而减小;2)黄河泥沙中非毛管孔隙度占比高,渗透初期非饱和导水率大,在低吸力段迅速失水;3)黄河泥沙容重为1.5 g/cm3毛管孔隙度最大,更有利于土壤有效水分的保持。在黄河泥沙充填复垦采煤沉陷地的实践过程中对黄河泥沙充填层进行合理的机械压实,使容重控制为1.5 g/cm3,能够在一定程度上提高黄河泥沙的持水性,实现黄河泥沙充填复垦耕地生产力水平的提高。     

Corn Residue Removal Effects on Hydraulically Effective Macropores

Enhanced understanding of biomass removal effects on soil quality could be achieved with greater knowledge of how corn residue removal and cover crops interact to affect surface pore structure. This study was conducted to evaluate the effects of corn (Zea mays L.) residue removal on soil macropore characteristics and to assess the effectiveness of cover crops in mitigating the potential negative impacts of corn biomass removal on surface pore structure. Three different corn residue removal rates and the presence or absence of cover crops were evaluated in a no-till corn/soybean (Glycine max L.) rotation near Brookings, SD. Following eight years of residue removal high (HRR) and medium (MRR) rates of residue removal reduced water inflow into the soil surface compared to the low (LRR) residue removal treatment. The representative mean pore radius (λ_Δψ) for both rotation phases of LRR approached the same value (≈ 235 µm). However, nine months after corn residue removal the λ_Δψ for HRR in the soybean phase of the rotation was significantly lower than LRR at 161 µm. There was no significant difference in λ_Δψ between HRR (214 µm) and LRR (236 µm) 21 months after residue removal during the corn phase of the rotation. The initial reduction in λ_Δψ following corn residue removal in HRR followed by soil surface recovery the following year suggests that inclusion of decaying corn residue is critical in the maintenance of hydraulically functional macropores in this fine textured soil. Cover crops were not observed to mitigate these impacts of crop residue removal on surface soil structure within the time period of the study.     

CT扫描技术研究有机物料还田深度对黑土孔隙结构影响

为了探明有机物料还田深度对土壤孔隙结构的影响,2019年玉米播种前在黑龙江海伦市的黑土上开展了田间定位试验,设置了秸秆浅混还田(0～15 cm)(T1)、秸秆深混还田(0～35 cm)(T2)和秸秆配合有机肥深混还田(0～35 cm)(T3)3个有机物料还田处理,以无秸秆还田常规耕作为对照(CK),4次重复,随机排列....     

河西走廊荒漠区土壤物理性质沿降水梯度的变化

土壤质量、土壤蓄水保肥能力和土壤养分吸收利用与土壤物理性质有密切联系。在甘肃省河西走廊民乐县至高台县自东向西的天然降水梯度上,选择荒漠区的7个研究点对土壤表层(0—20cm)和亚表层(20—40cm)分别采集42个土壤样品,在野外采用张力入渗仪测定饱和导水率,室内采用常规方法对土壤容重、孔隙度、颗粒组成等项目进行了测定。结果表明,在360～100mm的降水梯度上,荒漠土壤粉粒和黏粒含量降低,砂粒含量增加;伴随着土壤的粗粒化,引起土体的风散和结构的破坏,使土壤容重增加、孔隙度降低、持水性能下降等一系列物理性质的恶化。土壤表层、亚表层饱和导水率Ksat和变异系数Cv分别为70.0%和86.3%,均是土壤表层和亚表层各物理性质中变异系数最高的。     

不同形成时间鼢鼠鼠丘土壤水力学性质的对比

为探寻高原鼢鼠活动对若尔盖草原土壤持水性能的影响,通过田间原位张力入渗和室内沙箱+压力膜仪试验,探索不同形成时间鼠丘土壤水力学参数以及土壤大孔隙度的差异。结果表明:与草地对照相比,鼠丘土壤中易于流失的结构性孔隙水(θstr)含量增加,而能被植物有效利用的基质性孔隙水(θtxt)含量下降(由对照组(0.14±0.02)cm~3/cm~3降低至(0.10±0.02)cm~3/cm~3)。新鼠丘和1年鼢鼠鼠丘中半径250μm中大孔隙的有效孔隙度较草地对照组分别平均增加30%和11%,饱和导水率分别平均增加38%和21%。高原鼢鼠活动改变了土壤水力学特征,降低了土壤有效水的持水量,提高了土壤饱和导水率,使草地保水能力下降,易出现水分亏缺,增加草地退化和逐步沙化的风险。     

Soil physical properties of afforested and arable land

Abstract. The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides , and silver birch, Betula pendula , and the ley crops were one to five years old.
The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops.
Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.     

Soil Physical Properties and Bromide Movement in Relation to Tillage System

Abstract

Conventional (CT) and no‐tillage (NT) effects on soil physical properties and bromide (Br) movement were studied at two locations in North Carolina. The soils were a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Paleudult) at a North American eastern Coastal Plain location and a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) at a Piedmont location. Bulk density (Db), macroporosity (Mp), and saturated hydraulic conductivity (Ks) were measured in the plant row (R) and trafficked (T) or untrafficked (N) interrow positions. Simulated rain was applied at two intensities to 1?m² plots after KBr was surface applied. The first simulated rain (30 min) consisted of a low (1.27 cm h^?1) or a high (5.08 cm h^?1) intensity applied 24 h after Br application. One week later, the high rainfall rate was repeated on all plots. Soil samples for Br determinations were taken 2 days after each rain simulation event to a depth of 40 cm and at the end of the growing season to 120 cm. Soil physical properties were affected by both tillage and position. Bulk density was greater for NT than for CT and in the T compared with R and N row positions. Mp was significantly greater in NT than CT at Coastal Plain location, but the results were opposite at the Piedmont location. Saturated hydraulic conductivity was highly variable ranging from 0.36 cm h^?1 to 14.4 cm h^?1 at the Coastal Plain location and from 0.06 cm h^?1 to 7.12 cm h^?1 at the Piedmont location. Saturated hydraulic conductivity at T position was about 100% lower than Ks at N and R positions, but the effect of tillage system was not significant on Ks. The surface 10 cm of soil contained the greatest Br concentration for both tillage systems. For the first and second sampling dates, greater Br movement occurred under NT vs. CT. However, no significant differences were observed in Br movement in the end of season sampling. Because of the coarser soil texture, greater Ks and Mp at the Coastal Plain location, Br moved, to a greater depth at this site than at the Piedmont site.     

华北土石山区森林土壤中石砾分布特征对土壤大孔隙及导水性质的影响

为了探究土壤中石砾对大孔隙形成的作用及对饱和导水率的影响,研究京郊密云水库水源涵养林内土壤石砾分布特征、大孔隙分布特征以及与饱和导水率之间的关系。结果表明:(1)林区0—30cm土壤层内石砾体积含量范围为7.10%~22.05%,质量含量范围为10.76%~38.20%,且石砾多集中分布于5~10mm粒径范围内;石砾含量随坡向呈现阳坡阴坡半阴半阳坡的规律;(2)石砾含量与当量孔径1.5mm的孔隙密度呈现极显著相关关系(p0.01),粒径5mm的石砾体积含量与大孔隙密度具有显著相关性(p0.05),说明砾石主要影响较大孔隙,特别是粒径5mm的石砾对大孔隙的形成影响较大;(3)当量孔径1.5mm的孔隙数量仅占总孔隙数量的1.41%,但对导水速率的贡献率为54.44%;饱和导水率与其呈线性关系。     

稻田—田埂过渡区土壤水分运动与保持特征

为揭示田埂对稻田水分渗漏的影响,以江汉平原典型稻田—田埂过渡区为研究对象,采用室内土壤理化性质分析、水力学参数测定和田间染色示踪等方法量化了过渡区各位点(田内、田埂和灌溉沟)土壤剖面导水与持水性能差异,并揭示了该区域的水流特征。结果表明:(1)不同位点的土壤饱和导水率(Ks)均随土层深度的增加而减小,上层(-20—35cm)高于中、下层(35—65cm),剖面导水性能表现为田埂灌溉沟田内,田埂平均Ks分别是灌溉沟和田内的1.6倍和16.0倍;(2)同一吸力值下不同位点土壤含水量差异较大,田内含水量最高,灌溉沟其次,田埂最低,在持水性能上表现为田内灌溉沟田埂;(3)田埂土壤受动物活动和根系生长影响剧烈,导致其大孔隙(当量孔径0.3mm)含量整体上高于田内,在染色特征上表现为田埂中、下层土壤染色面积显著高于田内。由于稻田-田埂过渡区不同位点土壤的导水和持水能力差异显著,稻田水分不仅可以在田内发生垂直渗漏,还可以通过田埂区域垂直入渗和跨田埂侧流两种方式快速流失,进而加速了稻田水分的散失。     

黄土高原不同退耕还林地森林植被改良土壤特性研究

对比研究了青海省大通县不同类型退耕还林地、草地、农田的土壤性质,包括土壤容重、土壤孔隙度、土壤水稳性团粒结构、土壤饱和导水率。结果表明:华北落叶松容重最小,为农田容重的62%,青杨青海云杉混交林是农田土壤容重的83%;0~15 cm土层青海云杉混交林>0.25 mm的团粒结构含量为45.21%,草坡、耕地分别为32.18%、20.81%;北落叶松纯林的最小饱和导水率是1.22 mm/min,林地中饱和导水率最小的是落叶松青海云杉混交林,为0.17 mm/min,草地和农田分别为0.11 mm/min0、.09 mm/min。退耕还林后,与农田相比,林地土壤物理性质得到明显改善,针阔混交林改良土壤特性作用较好,除了华北落叶松纯林和华北落叶松青海云杉混交林外,针阔混交林的土壤物理性质好于阔叶纯林和针叶纯林,草坡和农田较差,草坡略好于农田。     

Mualem模型中的饱和导水率修正研究

[目的]提高Mualem模型计算非饱和导水率的准确性。[方法]采用理论推导结合数据统计的方法研究该模型中的饱和导水率ks修正问题。基于Brooks—Corey土壤水分特征曲线模型,建立修正导水率ko与土壤水分特征曲线之间的理论关系式;通过回归分析得到ko与土壤水分特征曲线之间的理论关系式中相关参数。[结果]利用原状黄土的非饱和渗透试验数据,对考虑修正导水率ko的Mualem模型的准确性进行了验证,得到了比较满意的结果。[结论]研究成果可用于依据土壤水分特征曲线直接确定非饱和土导水率,对非饱和导水率预测研究具有一定参考价值。     

不同水耕年限稻田土壤水分渗漏与保持特征

以江汉平原连续水耕年限大于100年(老稻田)和由旱耕改为水耕17年(新稻田)的稻田为研究对象,通过测定土壤剖面基本理化性质和水力学参数,揭示了2种稻田土壤水分渗漏和保持特征差异。结果表明:(1)新稻田土壤的平均饱和导水率(Ks)为32.05cm/d,显著高于老稻田(17.91cm/d)。新、老稻田土壤Ks均表现为耕作层底土层犁底层,新稻田耕作层Ks分别为犁底层和底土层的6.3倍和5.7倍,老稻田耕作层Ks分别是犁底层和底土层的6.9倍和4.0倍。(2)老稻田土壤持水能力高于新稻田,同一剖面不同土层持水能力表现为耕犁底层底土层耕作层。0.03mm当量孔径的孔隙比例随土壤剖面深度的增加而降低,新稻田各层土壤比例大于老稻田。(3)新、老稻田最大有效水含量随土壤深度的增加而降低,老稻田各土层(32.25%~46.59%)均高于新稻田(26.99%~36.74%)。老稻田平均总库容(135.8mm)大于新稻田(124.4mm),新稻田滞洪库容(11.21~38.74mm)大于老稻田(8.1~60.74mm)。旱耕改水耕加重了水资源的消耗,增加了浅层地下水污染风险。     

沂蒙山区不同母岩发育土壤物理性质

以沂蒙山区小圣堂小流域为研究区,对比分析了酸性岩石和钙质岩石发育土壤的物理性质及其影响因素。结果表明:(1)酸性岩石发育土壤石砾及砂粒含量较高,土壤质地由砂壤质到壤砂质,且随土层深度增加,石砾含量增加。钙质岩石发育土壤粉粒及黏粒含量较高,上下两层的土壤颗粒组成相差不大。受成土母岩影响两种土壤分形维数都很低,且酸性岩石发育土壤的分形维数更低。两种土壤石砾含量均大于10%,为粗骨土。(2)酸性岩石发育土壤的容重较大,总孔隙度和毛管孔隙度较小。两种土壤的容重和毛管孔隙度随土层深度的增加而变大,总孔隙度和非毛管孔隙度则反之。毛管孔隙度大小主要受土壤分形维数的影响。(3)酸性岩石发育土壤的饱和导水率大于钙质岩石发育土壤,酸性岩石发育土壤10—20cm土层的饱和导水率较0—10cm土层大,而钙质岩石发育土壤饱和导水率在不同土层深度呈现不规律的变化。土壤质地是影响沂蒙山区土壤饱和导水率的主导因素,其中,砂粒和粉粒含量的影响尤为明显。     

Hydraulic conductivity and porosity under conventional and no-tillage and the effect of three species of cover crop in northern France

We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no‐till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's‐foot‐trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (?0.6, ?0.2 and ?0.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0–10 cm layer and in the 10–20 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0–10 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous‐root type) and the leguminous ones (tap‐root type). However, we recorded larger functional pores and more tubules in the no‐till treatments with a cover crop, compared with the no‐till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time.     

莱芜市红石公园土壤结构特征及其与饱和导水率的关系

[目的]分析土壤水分运移过程,探究莱芜市红石公园土壤结构特征及其对饱和导水率的影响,为促进该区生态恢复和建设提供理论参考。[方法]采用环刀分层取样对研究区6块样地进行土壤物理结构特征测定,进行水分穿透试验,测量土壤饱和导水率。[结果]试验区土壤密度及石砾含量大小均表现为:纯草本灌木—草本乔木—草本;土壤R0.25(0.25mm水稳性团聚体含量)、含水率、总孔隙度及饱和导水率大小均表现为:乔木—草本灌木—草本纯草本;表层土壤具有更优的土壤结构及更大的饱和导水率;土壤饱和导水率与土壤密度、石砾含量呈现显著负相关关系,与土壤总孔隙度及R0.25呈现显著正相关关系。[结论]土壤总孔隙度是土壤饱和导水率的最主要影响因子,土壤R0.25含量、土壤密度及石砾含量次之。