有机质含量对人造技术土水分结构性质的影响

Constructed Technosols may be an alternative for creating urban green spaces. However, the hydro-structural properties emerging from the assembly of artefacts have never been documented. The soil shrinkage curve (SSC) could provide relevant structural information about constructed Technosols, such as the water holding capacity of each pore system (macropores and micropores). The objectives of this study were (i) to evaluate the SSC and water retention curve (WRC) to describe the structure of constructed Technosols and (ii) to understand the influence of organic matter content on soil hydro-structural properties. In this study, Technosols were obtained by mixing green waste compost (GWC) with the material excavated from deep horizons of soil (EDH). The GWC was mixed with EDH in six different volumetric percentages from 0% to 50% (GWC/total). The GWC and EDH exhibited highly divergent hydro-structural properties: the SSC was hyperbolic for GWC and sigmoid for EDH. All six mixture treatments (0%, 10%, 20%, 30%, 40% and 50% GWC) exhibited the classical sigmoid shape, revealing two embedded levels of pore systems. The 20% GWC treatment was hydro-structurally similar to the 30% and 40% GWC treatments; so, a large quantity of expansive GWC is unnecessary. The relation with the GWC percentage was a second-degree equation for volumetric available water in micropores, but was linear for volumetric available water in macropores and total volumetric available water. Total volumetric available water in the 50% GWC treatment was twice as high as that in the 0% GWC treatment. By combining SSCs and WRCs, increasing the GWC percentage increased water holding capacity by decreasing the maximum equivalent size of water-saturated micropores at the shrinkage limit and increasing the maximum equivalent size of water-saturated macropores, resulting in an increased range of pore diameter able to retain available water.     

生物炭对沙质土水分蒸发和导水率的影响（英文）

Biochar,as a kind of soil amendment,has important effects on soil water retention.In this research,4 different kinds of biochars were used to investigate their influences on hydraulic properties and water evaporation in a sandy soil from Hebei Province,China.Biochar had strong absorption ability in the sandy soil.The ratio of water content in the biochar to that in the sandy soil was less than the corresponding ratio of porosity.Because of the different hydraulic properties between the sandy soil and the biochar,the saturated hydraulic conductivity of the sandy soil gradually decreased with the increasing biochar addition.The biochar with larger pore volume and average pore diameter had better water retention.More water was retained in the sandy soil when the biochar was added in a single layer,but not when the biochar was uniformly mixed with soil.Particle size of the added biochar had a significant influence on the hydraulic properties of the mixture of sand and biochar.Grinding the biochar into powder destroyed the pore structure,which simultaneously reduced the water absorption ability and hydraulic conductivity of the biochar.For this reason,adding biochar powder to the sandy soil would not decrease the water evaporation loss of the soil itself.     

使用自由软件和便携式光学显微镜研究土壤孔隙特征

Total porosity (TP), determined by image analysis, pore type and pore size distribution were evaluated on impregnated soil blocks from an undisturbed Brazilian sandy loam soil using a digital portable optical microscope. The free software Image J (version 1.40g) was used for image analysis. Procedures for soil image collection and analysis were presented. The image analysis allowed the evaluation of pore sizes with diameters ranging from 20 to >1 000 μm. The following types of pores were also obtained: rounded, elongated and intermediate. The results allowed the characterization of the soil as moderately porous (TP=21.6%). Rounded, intermediate and elongated pores were responsible for 11.6%, 31.7% and 56.7% of TP. In relation to pore size 51.1% of TP was in the 100-500 μm size class and a third of TP came from the pores larger than 500 μm.     

粘土土壤孔隙大小分布及其与土壤有机质的相关性

Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and processes.In this study,PSD of three clayey soils collected from the topsoil(0-20 cm) of Vertisols in Northern China was analyzed using the N_2 adsorption(NA) and mercury intrusion porosimetry(MIP) methods.The effect of soil organic matter(SOM) on the PSD of clayey soils was also evaluated.The differential curves of pore volume of clayey soils by the NA method exhibited that the pores with diameter 0.01 μm accounted for more than 50%in the pore size range of 0.001 to 0.1 μm.The differential pore curves of clayey soils by the MIP method exhibited three distinct peaks in pore size range of 60 to 100,0.3 to 0.4 and 0.009 to 0.012 μm,respectively.In the three clayey soils,the ultramicropores(5-0.1μm) were determined to be the main pore class(on average 35.5%),followed by macropores( 75 μm,31.4%),cryptopores(0.1-0.007μm,16.0%),micropores(30-5 μm,9.7%) and mesopores(75-30 μm,7.3%).The SOM greatly affected the pore structure and PSD of aggregates in clayey soils.In particular,SOM removal reduced the volume and porosity of 5-100 μm pores while increased those of 5 μm pores in the 5-2 and 2-0.25 mm aggregates of clayey soils.The increase in the volume and porosity of 5 μm pores may be attributed to the disaggregation and partial emptying of small pores caused by the destruction of SOM.     

再氧化对土壤的通气性变异的影响

The interplay between soil physical parameters during the recovery from anoxic stresses (reoxidation) is largely unrecognized. This study was conducted to characterise the soil aeration status and derive correlations between variable aeration factors during reoxidation. Surface layers (0-30 cm) of three soil types, Haplic Phaeozem, Mollic Gleysol, and Eutric Cambisol (FAO soil group), were selected for analysis. The moisture content was determined for a range of pF values (0, 1.5, 2.2, 2.7, and 3.2), corresponding to the available water for microorganisms and plant roots. The variability of a number of soil aeration parameters, such as water potential (pF), air-filled porosity (Eg), oxygen diffusion rate (ODR), and redox potential (Eh), were investigated. These parameters were found to be interrelated in most cases. There were significant (P < 0.001) negative correlations of pF, Eg, and ODR with Eh. A decrease in water content as a consequence of soil reoxidation was manifested by an increase in the values of aeration factors in the soil environment. These results contributed to understanding of soil redox processes during recovery from flooding and might be useful for development of agricultural techniques aiming at soil reoxidation and soil fertility optimisation.     

生物炭引起的土体回弹变化：土壤质地和生物炭用量的影响

Biochars are,amongst other available amendment materials,considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions.The latter is widely discussed as a consequence of improved physical quality of the amended soil.However,the mechanisms for this improvement are still poorly understood.This study investigated the effect of woodchip biochar amendment on micro-structural development,micro-and macro-structural stability,and resilience of two differently textured soils,fine sand (FS) and sandy loam (SL).Test substrates were prepared by adding 50 or 100 g kg-1 biochar to FS or SL.Total porosity and plant available water were significantly increased in both soils.Moreover,compressive strength of the aggregates was significantly decreased when biochar amount was doubled.Mechanical resilience of the aggregates at both micro-and macro-scale was improved in the biochar-amended soils,impacting the cohesion and compressive behavior.A combination of these effects will result in an improved pore structure and aeration.Consequently,the physicochemical environment for plants and microbes is improved.Furthermore,the improved stability properties will result in better capacity of the biochar-amended soil to recover from the myriad of mechanical stresses imposed under arable systems,including vehicle traffic,to the weight of overburden soil.However,it was noted that doubling the amendment rate did not in any case offer any remarkable additional improvement in these properties,suggesting a further need to investigate the optimal amendment rate.     

生物炭碳固定于稳定性土壤团聚体中：土壤黏土矿物及其它土壤性质的作用

Aggregation and structure play key roles in water-holding capacity and stability of soils.In this study,the incorporation of carbon(C) from switchgrass biochar into stable aggregate size fractions was assessed in an Aridisol(from Colorado,USA) dominated by 2:1 clays and an Alfisol(from Virginia,USA) containing weathered mixed 1:1 and 2:1 mineralogy,to evaluate the effect of biochar addition on soil characteristics.The biochar was applied at 4 levels,0,25,50,and 100 g kg~(-1),to the soils grown with wheat in a growth chamber experiment.The changes in soil strength and water-holding capacity using water release curves were measured.In the Colorado soil,the proportion of soil occurring in large aggregates decreased,with concomitant increases in small size fractions.No changes in aggregate size fractions occurred in the Virginia soil.In the Colorado soil,C content increased from 3.3 to 16.8 g kg~(-1),whereas in the53 μm fraction C content increased from 5.7 to 22.6 g kg~(-1) with 100 g kg~(-1)biochar addition.In the Virginia soil,C content within aggregate size fractions increased for each size fraction,except the2 000 μm fraction.The greatest increase(from 6.2 to 22.0 g kg~(-1)) occurred in the 53–250 μm fraction.The results indicated that C was incorporated into larger aggregates in the Virginia soil,but remained largely unassociated to soil particles in the Colorado soil.Biochar addition had no significant effect on water-holding capacity or strength measurements.Adding biochar to more weathered soils with high native soil organic content may result in greater stabilization of incorporated C and result in less loss because of erosion and transport,compared with the soils dominated by 2:1 clays and low native soil organic content.     

生物炭和PAM混施影响煤矸石基质水分的入渗和蒸发

探究生物炭和聚丙烯酰胺(PAM)混施对煤矸石基质水分入渗和蒸发的影响,可为矿区矸石山土壤水分的调节提供依据。采用模拟土柱方法,研究不同矸土比(1∶2,1∶1和2∶1)的煤矸石基质,在混施生物炭(1%,2%和4%)和PAM(0.5‰和1‰)条件下,基质水分的吸持性能、入渗及蒸发特征。结果表明:(1)对煤矸石基质入渗性能的影响程度为生物炭PAM矸土比;随生物炭施用量的增加,基质的饱和含水量以及入渗速率均呈增加趋势,而PAM施用量的增加则减弱了煤矸石基质的饱和含水量和入渗速率。(2)添加1‰PAM处理的基质累积蒸发量均低于添加0.5‰PAM的处理;矸土比对煤矸石基质水分蒸发影响程度较生物炭和PAM大。(3)聚类分析表明,4%生物炭和0.5‰PAM混施时煤矸石基质的水分吸持性能及入渗速率较高;而矸土比为2∶1时,2%的生物炭和1‰的PAM混施可减弱基质水分的蒸发。总之,增加生物炭施用量有利于基质水分入渗,而PAM用量的增加,可抑制煤矸石基质水分的蒸发。     

耕作方式对双季稻田土壤有机碳储量的影响

Tillage practices can potentially afect soil organic carbon (SOC) accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice (Oryza sativa L.) field in Hunan Province of China. Three tillage treatments, no-till (NT), conventional plow tillage(PT), and rotary tillage(RT), were laid in a randomized complete block design. Concentrations of SOC and bulk density(BD) of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass(ESM) basis and fixed depth (FD) basis.Soil carbon budget(SCB) under diferent tillage systems were assessed on the basis of emissions of methane(CH4) and CO2 and the amount of carbon (C) removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT (on an ESM basis) was as high as 129.32 Mg C ha 1,significantly higher than those under PT and RT (P < 0.05). The order of SOC stocks in the 0-80 cm soil layer was NT > PT > RT,and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced efects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage efects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.     

生物炭和PAM共施对黄绵土水分入渗和蒸发的影响

采用二因素三水平(生物炭用量分别为干土重的0,2%和4%,聚丙烯酰胺用量分别为干土重的0,0.02‰和0.04‰)完全试验方案设计,研究了两种土壤结构调理剂生物炭和聚丙烯酰胺(PAM)共施对黄绵土水分入渗和土壤蒸发的影响。结果表明:(1)生物炭施用后对Philip模型的稳渗率(A)和Horton模型的衰减指数(β)有显著影响,2%生物炭添加对A和β影响不大,但4%生物炭添加显著降低A,显著增加了β;施用PAM对Kostiakov模型的参数K,Philip模型的吸渗率(S)和Horton模型中的稳定入渗率(if)与初始入渗率(i0)有显著影响,0.02‰PAM添加对这些参数无显著影响,但0.04‰PAM添加显著降低K,S,if和i0。生物炭和PAM共施对3种入渗模型的大多数参数存在显著交互作用。所有处理中,以2%生物炭+0.02‰PAM增加入渗的效果为最好;(2)生物炭、PAM及二者交互作用对蒸发速率和累积蒸发量影响均不显著,表明生物炭和PAM单施或共施对黄绵土蒸发影响不大。     

砒砂岩风化物对土壤水分特征曲线及蒸发的影响

运用高速离心机法和室内模拟蒸发的方法,对比研究了红色(RS)、灰色(GS)和白色(WS)三种颜色砒砂岩风化物在不同添加比例条件下对沙黄土和风沙土水分特征曲线、供水能力和干旱过程中失水过程的影响。研究表明:砒砂岩风化物的添加对沙黄土和风沙土水分特征曲线有较明显的影响。砒砂岩风化物的持水能力均高于沙黄土和风沙土,砒砂岩风化物添加提高了风沙土和沙黄土的持水能力,降低了沙黄土和风沙土失水速率;较低比例的砒砂岩风化物提高了沙黄土和风沙土的比水容量,但对风沙土和沙黄土低吸力段供水能力的提高作用并不明显。整个蒸发期间,砒砂岩风化物降低了沙黄土的标准蒸发量,而对于风沙土,其作用是蒸发前期降低,中后期增加。红色、灰色、白色三种砒砂岩风化物分别使风沙土的蒸发失水比提高了11.59%、10.14%和0.01%,添加三种砒砂岩风化物后的处理的最终平均含水量分别是风沙土的4倍、2.33倍、1.33倍,使沙黄土的蒸发失水比降低了13.33%、13.33%、29.52%,最终含水量降低了45.83%、54.17%、66.67%。因此,从提高土壤持水能力方面考虑,砒砂岩可以用于当地矿区和排土场区土壤改良,以促进生态修复。     

施用生物炭对紫色土坡耕地耕层土壤水力学性质的影响

该研究通过野外坡耕地小区施用1%秸秆生物炭1年后的对比试验,揭示生物炭对川中丘陵区紫色土耕作层土壤水力学参数、大孔隙度及其对饱和导水率的贡献率所产生的影响。试验设对照区与施用生物炭区2个处理,各处理有3个平行小区,耕作层土壤分为表层和亚表层(2~7和7~12 cm)。比较2个处理小区试验结果,可以发现:1)施用生物炭导致植物难以利用的土壤滞留水和易流失的结构性孔隙水的含量(θstr)下降,而基质性孔隙中植物有效水含量显著提高(P0.05),由(0.058±0.003)cm3/cm3增加至(0.085±0.002)cm3/cm3;2)表层和亚表层土壤中对产流起主要贡献的半径125μm的总有效孔隙度分别平均增加54%和8%,其中孔径500μm的孔隙增加最为明显,高达110%和355%;3)表层和亚表层土壤的饱和导水率分别平均增加45%和35%。研究证明,施用生物炭,一方面,能增加土壤有效水的持水量,有利于植物抗旱;另一方面,提高土壤导水率,有利于水分入渗,从而减少地表径流及土壤侵蚀的发生。     

生物炭及炭基肥对棕壤持水能力的影响

通过连续6年微区定位试验,以传统的土壤培肥方式作为对照,探究较长时间施用生物炭和炭基肥对土壤保水作用的影响,为生物炭农用提供理论参考。定位试验于2009年开始,连续6年进行了花生微区田间试验（2 m²）。试验设4个处理,分别为秸秆还田+NPK（CS）、施用猪厩肥+NPK（PMC）、生物炭+NPK（BIO）和炭基肥（BF）处理,在2014年花生的生育期间测定了表层土壤含水量、水分累积蒸发量和土壤理化性质。研究表明:土壤水分含量充足时,BIO和BF处理含水量与PMC处理接近,都高于CS处理;土壤含水量较低时,BIO和BF处理含水量低于CS和PMC处理。与秸秆还田和施用猪厩肥相比,生物炭处理可提高土壤供水数量但降低土壤保水能力。炭基肥处理降低了土壤供水数量和保水能力。     

以水面蒸发量为参考推求土壤实际蒸发量的数学模型

为了准确估算土壤在实际条件下的蒸发量,该文以水面蒸发量为参考,结合能量平衡方程及微气象学方法,推导计算土壤实际蒸发量的数学模型.结果表明所建模型所需参数为水面及蒸发土壤表面的日最高温度和日平均温度、水面日蒸发量、风速等.模型的验证结果表明计算的土壤蒸发量与实测蒸发量比较吻合(R2=0.90).模型所引入的参考蒸发面使其避开了土壤蒸发复杂的物理本质,从而使得对土壤蒸发的计算变得简单易行.     

模拟降雨条件下保水剂对沙质土壤水分的影响

为了探究保水剂对沙质土壤水分的影响,采用室内重建土柱,在人工模拟降雨条件下研究不同用量保水剂对沙质土壤(0~30 cm)含水率的影响。结果表明:土壤含水率随着保水剂用量的增加而增加,保水剂用量为0.2%时不但省时省力,而且0~10 cm、10~20 cm、20~30 cm 3个土层土壤含水率分别为45.42%、48.48%、46.16%,既能满足植物的生长需要,又能节省经济成本,可为干旱、半干旱区节水造林及保水剂的合理使用提供理论依据。     

Water retention properties of a sandy soil with superabsorbent polymers as affected by aging and water quality

Hydraulic properties, specifically the water holding capacity of soils, play a key role in the ability of soils to sustain plant growth. Additions of hydrophilic polymers (superabsorbents) can improve the water holding capacity of sandy soils. This has led to practical applications of these materials particularly in arid regions and countries, where water is the limiting factor for plant production. The objectives of this study are to investigate how effective hydraulic properties of polymer‐soil mixtures are affected by addition of absorbents in different concentrations. Novel aspects are the investigation of aging under repeated wetting–drying‐cycles over an appreciable time in the field and a systematic investigation of the salt influence on the water uptake of polymers. We added the polymer Super AB, A‐200 (Iran Polymer Institute), to dune sand in ratios of 0.3%, 0.6%, and 1% w/w. We found that the effective water retention characteristics of the soil–absorbent mixtures were improved with respect to plant‐available water compared to the pure sand, and the improvement was related to the respective amount of absorbent in the mixture. The plant available water content (PAW) increased from 0.005 for the untreated sand to 0.06, 0.20, and 0.28 g g^?1, respectively, for the sand with the three polymer additions. Due to aging of the polymers, PAW decreased after 6 months of cyclic drying and wetting to about half of the value immediately after the initial treatment. We attribute this to the effect of salts. This is corroborated by the results from water uptake experiments by the pure polymers. Repeated cycles of water uptake showed that salts in the water greatly reduced the uptake capacity of the polymers after few cycles. The effect was strong for bivalent cations and less pronounced for monovalent cations.     

生物质炭对旱作农田土壤持水特性的影响

为确定添加生物质炭对旱作农田土壤持水特性的影响,在隆中黄土高原典型旱作农田区设置相关定位试验,对不同生物质炭输入水平的土壤容重、土壤孔隙度、土壤水分常数及土壤水分特征曲线进行测定。结果表明,生物质炭的添加能够减小土壤容重,增加土壤孔隙度。随着生物质炭输入水平的增加,土壤容重的减小及土壤孔隙度的增加幅度加大。生物质炭达到50t/hm~2时土壤结构变化最为明显,0—5,5—10,10—30cm土层中土壤容重相比对照分别减小7.01%,9.91%,16.60%,土壤毛管孔隙度分别增加19.47%,21.02%,29.94%;并且生物质炭的施入可以增加土壤饱和含水量、土壤田间持水量、土壤有效水分含量。随着生物质炭输入水平的不断加大,各水分常数呈现出上升趋势,但当生物质炭输入水平达到40t/hm~2后涨幅空间开始减小。说明生物质炭的添加能够提高旱作农田的持水性能,但输入水平达到40t/hm~2后,土壤持水性能趋于稳定。     

秸秆不同还田方式对土壤低吸力段持水能力及蒸发特性的影响

利用张力计测定蒸发过程中低吸力段土壤水分特征曲线,对比研究了秸秆在经过粉碎、氨化及与无机土壤改良剂混合三种措施处理后对土壤饱和含水量、低吸力段土壤持水及供水能力和早期干旱过程中土壤脱水速度的影响。结果显示:粉碎秸秆施入土壤后提高了土壤饱和含水量、持水及供水能力,而长秸秆对土壤饱和含水量、持水及供水能力的影响较小;粉碎并氨化的秸秆对土壤饱和含水量、持水及供水能力的提高作用更为显著。粉碎秸秆及长秸秆处理均易造成早期干旱过程中脱水速度过快,氨化后或当秸秆与无机土壤改良剂混合施入土壤时,土壤低吸力段脱水速度明显减慢,利于土壤有效水的保存。该结果为提出新的能最大效率发挥秸秆改良土壤作用的秸秆还田方式提供了一定的理论基础。