滁菊原产地域保护区土壤有机质与土壤养分的关系研究

[目的]研究滁菊原产地域保护区土壤有机质和土壤养分的相关性,为滁菊原产地域保护区土壤精准化管理提供依据.[方法]采集滁菊原产地域保护区108个样品,对土壤有机质、全氮、全磷、全钾和速效氮、速效磷、速效钾含量进行了测定,并分析有机质与土壤养分的相关性.[结果]滁菊土壤中有机质含量与全氮、全磷、全钾、速效氮、速效磷含量表现为0.01水平显著正相关,与速效钾含量不存在相关性.[结论]滁菊原产地域保护区土壤有机质可以作为土壤营养状况的主要判断指标.     

北运河下游不同土地利用方式下土壤剖面养分研究

[目的]研究土地利用方式对土壤养分剖面分布的影响.[方法]对北运河下游武清区土壤取样,测定土壤养分(pH、碱解氮、有效磷、速效钾、有机质)和土壤机械组成,结合武清区土地利用方式进行分析.[结果]不同土地利用方式对土壤机械组成有一定的影响,土壤剖面养分含量变化趋势为:有机质、碱解氮含量基本上呈抛"S"形分布,速效钾呈"U"形分布,而有效磷含量呈直线下降趋势.不同土地利用方式下耕层养分差异较明显.[结论]有效磷、有机质、碱解氮、速效钾含量具有一定的表聚性,以有效磷含量最有代表性.     

不同配比有机肥和改良剂对土壤理化性质及酶活性的影响

[目的]为快速修复退化土壤提供依据.[方法]以除草剂污染土壤和荒地心土作为材料,利用温室培养试验,研究了不同配比有机肥和改良剂在短期时间内对土壤理化性质及酶活性的影响.[结果]与空白相比,污染土壤的养分和有机质含量经单施改良剂处理后效果不显著,以不同配比的有机肥和改良剂施用于土壤中效果显著提高,土壤的pH值和酶活性经单施改良剂和添加不同配比有机肥+改良剂处理后效果显著提高;而荒地心土养分、有机质含量和酶活性经单施改良剂、混施不同配比的有机肥+改良剂处理后效果均显著提高,土壤的pH值以添加20%有机肥+改良剂处理的效果最为显著.2种土壤的容重均以添加10%和20%有机肥+改良剂处理的效果最为显著.[结论]添加不同配比的有机肥+改良剂可以有效提高土壤的理化性质和酶活性.     

苹果园化肥投入及土壤养分状况研究

[目的]获得苹果园化肥投入和土壤碱解氮、速效磷和速效钾的含量状况.[方法]对25个农户苹果园化肥投入进行调查,采集土壤样品进行测定分析.[结果]氮磷钾养分平均投入量为839.6、520.4、899.7 kg/hm<.2>,氮磷钾养分的投入比为1.00:0.62:1.07.0～60cm土壤碱解氮、速效磷、速效钾平均含量分别为53.49、70.73、180.10 mg/kg,土壤中碱解氮、速效磷、速效钾的比例为1.00:1.32:3.37.[结论]苹果园化肥投入总体水平比较高.土壤碱解氮的含量总体偏低,土壤速效磷的含量偏高,土壤速效钾的含量较高.     

基于Meta-analysis的中国干旱半干旱区土地利用变化的土壤碳氮效应研究

通过整合分析方法.对中国干旱、半干旱区农田、林地、灌丛和草地4种土地利用方式下地表土壤有机碳、氮含量进行了定量分析.结果表明,不同土地利用方式对表土碳、氮含量影响显著;草地转化为农田将降低土壤有机碳、全氮含量(-60.9%和-54.3%),草地转化为林地将导致土壤有机碳、全氮含量的降低(-21.5%和-31.3%);草地转化为灌木林地将增加土壤有机碳含量(+33.6%)和降低土壤全氮含量(-5.9%).可见,受人类活动干扰最为强烈的农田的土壤有机碳、全氮含量最低,而草地、灌木林地具有较好的土壤肥力和土壤质量保持功能.因此,开展灌草植被恢复和农田弃耕(自然恢复)可有效改善土壤肥力和增加土壤碳、氯存贮.     

昌黎县葡萄沟土壤肥力综合评价与对策研究

[目的]研究昌黎县葡萄沟葡萄园的土壤肥力现状,为合理施肥,提高葡萄的产量和品质提供科学依据.[方法]对昌黎县葡萄沟有代表性的葡萄园土壤样品进行理化性状测定和分析,运用修订的内梅罗综合指数法对该地区土壤肥力进行综合评价.[结果]昌黎县葡萄沟土壤pH值偏酸性,容重偏大,有机质含量贫乏,碱解氮含量偏低,速效磷含量丰富,部分葡萄园土壤存在钾素含量偏低,土壤供钾潜力不高的问题,绝大部分土壤处于无盐害的安全区.综合评价结果表明:昌黎县葡萄沟土壤综合肥力系数平均值为1.15,与土壤肥力等级划分指标相比,属三级,土壤肥力一般,其限制因子有有机质、碱解氮、容重、pH值和速效钾.[结论]可通过适量施用石灰,改良土壤酸性;增施有机肥;开展配方施肥,提高化肥利用率等措施提高昌黎县葡萄沟葡萄园土壤肥力.     

土壤有机废渣的生物降解研究

[目的]探讨土壤微生物降解化工废渣的影响因素及有效措施.[方法]在试验区用四分法在地表20cm内取土壤样品,分别测出单位质量的燃烧失重,再向每块试验区施入不同的废渣,每隔5d取样后,测定其燃烧失重,获得各块土壤有机废渣随时间的降解数据.[结果]土壤有机废渣的生物降解受废渣性质、废渣表面积、土壤含氧量、土壤pH、含湿量和土壤温度的影响.有机物的好氧降解比厌氧降解快的多,完全的多.土壤pH影响生物的活动.应维持在7-9.土壤含湿量控制50%-60%是微生物活动的最佳条件.土壤温度在零度以下,生物降解基本停止.[结论]在实际应用于工业化处理有机废渣时,还需对某种土质和某种废渣作进一步研究,控制生物降解速率和程度及其管理措施.     

柘皋河流域农田土壤氮磷迁移过程的模拟研究

[目的]研究土壤表层氮、磷迁移变化机理.[方法]选取柘皋河流域为试验区,以流域3种主要土地利用类型为研究对象,采用人工模拟降雨方法,在不同施肥量、降雨强度条件下研究了氮、磷在壤中流、渗漏液的迁移规律.[结果]氨氮在土壤中具有很强的吸附和转化能力,迁移深度较小,主要集中在表面;硝氮在土壤中迁移转化的过程与土壤特性及水力条件有着密切的关系.菜地土壤中流中总磷含量平均为0.52 mg/L,远远超出相邻水体(巢湖)中磷含量的控制要求.壤中流、渗漏液中氨氮、硝氮、总氮、有效磷及总磷含量同降雨强度、施肥量密切相关.[结论]除了控制地表径流传输,如何有效抑制壤中流中的氮磷迁移对该区域水环境污染的治理十分关键.     

石河子市城市垃圾对城市土壤理化性质的影响

为了分析干旱区绿洲城市垃圾是否对城市土壤理化性状产生影响,采集石河子市垃圾填埋场周边与远离填埋场周边的地区7种不同土地利用类型 16个土壤样品进行理化性质测定.结果表明:在这7种土壤类型中,垃圾填埋场的土壤理化性质变化最大,土壤污染最为严重;其次是工业区的土壤理化性质变化最为显著,交通道路和商业区再次之;人为干扰较小的绿化带土壤理化性质变化最小,说明垃圾填埋场、工业区对城市土壤的干扰最为强烈.垃圾填埋场周边表层有机质含量(大量剖面统计平均量)0.977%,全氮0.072%,碱解氮13.5μg/g,速磷5.2μg/g.而远离垃圾场经过改良形成的灌溉规模土表层有机质含量1.314%,全氮0.090%,碱解氮29.4μg/g,速磷5.45μg/g,土壤肥力水平显著提高.     

不同土壤调理剂对盐碱地土壤理化性质及水稻产量的影响

[目的]探讨不同土壤调理剂对盐碱地的改良效果及水稻产量的影响.[方法]在宁夏盐碱地施用8种土壤调理剂,研究不同调理剂对盐碱地土壤的理化性质、pH、盐分离子以及水稻生长发育和产量的影响.[结果]施用土壤调理剂后,不仅降低了土壤容重、pH并对土壤盐分离子产生不同影响,而且加快了水稻生育进程,增加了水稻的总茎数和穗数,提高了水稻产量.[结论]施用不同土壤调理剂均对土壤及水稻生长有一定的积极效果,ORYKTA、丹路菌剂、丹路菌肥的增产效果较为显著.     

Interaction of Soil Air Permeability and Soil Vapor Extraction

A new theoretical model to analyze the measurements obtained from a typical soil column venting experiment is proposed. The principles of mass transfer, Darcy's law, and air compressibility in the form of pressure-volume relationships were coupled to calculate the contaminant concentration in the gas phase (air), and the rate of contaminant removal. The proposed model relates soil air permeability with the contaminant removal and is capable of calculating the variation of soil air permeability with time during the venting process. The contaminated sand sample was idealized as a system of straight capillary tubes in the direction of flow, lined by the liquid contaminant. A closed-form solution for radial diffusion of the contaminants in a cylinder, coupled with axial advection of air, was used to model contaminant removal. The results from the mass transfer model were then used to trace the change of soil air permeability with time. The model also uses, as an alternative approach, a modified form of Darcy's law for compressible flow.     

Mars Soil Mechanical Properties and Suitability of Mars Soil Simulants

Determination of Mars soil mechanical properties will improve future lander mission success and provide narrower constraints for geomorphological modeling. A soil mechanics investigation was conducted wherein soil mechanical properties were determined by computer reconstruction of mass wasting features observed in photographs of Mars Exploration Rover landing sites and analysis of natural slope stability. Mars soil mechanical properties were compared with thermal inertia measurements and a correlation is presented. Tests with rovers and equipment for Mars surface exploration and various past laboratory experiments have incorporated a number of different Mars soil simulants. Standard laboratory measurements were conducted to characterize the shear strength, grain size distribution, and densities of various Mars soil simulants. From these measurements, the ability of a given simulant to appropriately represent the mechanical properties of in situ Mars soils was judged. Specific simulants are recommended for certain regions of Mars.     

Minimum Depth of Soil Cover above Soil–Steel Bridges

Soil–steel bridges are built of flexible corrugated steel panels buried in well-compacted granular soil. Their design is based on the composite interaction between the soil pressures and the displacements of the conduit wall. The structure failure could be initiated by shear or tension failure in the soil cover above the steel conduit. The provisions for design given in different codes, such as the Canadian Highway Bridge Design Code, managed to avoid some of the problems associated with the failure of soil above soil–steel bridges by requiring a minimum depth of soil cover over the crown of the conduit taking into consideration the geometric shape of the conduit. However, the present code requirements for a minimum depth of cover were developed for a maximum span of 7.62 m and using nonstiffened panels of 51 mm depth of corrugation. The effect of having larger spans or using more rigid corrugated panels has not been examined before and is the subject of this paper. The present study uses the finite-element analysis to re-examine the possible soil failures due to centric live loads (i.e., loads acting symmetrically about the mid span of conduit) or eccentric live loads. The study deals with spans up to 15.24 m of circular conduits and 21.3 m of arches with deep corrugations. It has been found that, in addition to the conduit geometry, the actual dimension of the span should be considered to determine the required depth of soil cover.     

Effects of Soil Water Salinity on Field Soil Hydraulic Functions

Unsaturated soil hydraulic parameters and functions used in numerical models to simulate water flow and solute transport in the unsaturated zone are generally considered invariant of soil water salinity levels. This study uses 5 years of field soil water salinity levels at three observation sites from the Land Retirement Demonstration Project (LRDP) (20069) located in western Fresno County, California, to test the hypothesis that field unsaturated soil hydraulic properties are also a function of soil water salinity level. The HYDRUS-1D software package for simulating one-dimensional (1D) movement of water, heat, and multiple solutes in variably saturated media, and Parameter Estimation (PEST), a model-independent parameter optimizer, is used to optimize the soil hydraulic parameters and downward bottom flux corresponding to three different average soil salinity levels at each site. The results show that at the same pressure head, soil water content is less with higher soil water salinity as compared with lower soil water salinity. It is thus concluded that the use of soil water salinity invariant soil water hydraulic parameters in numerical modeling can seriously compromise predictions, especially for a variable soil water salinity environment.     

Impact of Soil Type and Compaction Conditions on Soil Water Characteristic

Tests were conducted to determine the variation of water content and pore water suction for compacted clayey soils. The soils had varying amounts of clay fraction with plasticities ranging from low to high plasticity. The unsaturated soil behavior was investigated for six conditions, covering a range of compactive efforts and water contents. The experimental data were fit to four commonly used models for the water content-pore water suction relationship. Each model provided a satisfactory fit to the experimental data. However, the individual parameters obtained from the curve fits varied significantly between models. The soil water characteristic curves (SWCCs) were more sensitive to changes in compaction effort than changes in compaction water content. At similar water contents, the pore water suction increased with increasing compaction effort for each compaction condition and soil type. For all compaction conditions, the lowest plasticity soils retained the smallest water content and the highest plasticity soils retained the highest water content at a specified suction. In addition, SWCCs for soils compacted in the laboratory and in the field were similar.     

Estimating Evaporation from Bare Soil Using Soil Moisture Data

A method is presented that uses continuous soil moisture measurements and hourly reference evapotranspiration data to estimate a soil hydraulic factor (β) for modeling soil evaporation. The β factor is used to assess the end of the energy limited soil evaporation phase (Stage 1) and the evaporation rate during the soil hydraulic limited phase (Stage 2) of a two-stage soil evaporation model. A previously developed and tested method to determine β uses an energy balance approach with sensible heat flux density estimated using the surface renewal method to obtain the continuous soil evaporation. A new method is presented, which uses a hydroprobe soil moisture measuring device to estimate the continuous soil evaporation. The estimation of evaporation with soil moisture sensors was simpler and less expensive when compared to the energy balance technique. The methods, evaluated in two field experiments, showed good agreement with evaporation data. Using the evaporation model and β derived from either method provided a good estimate of measured soil evaporation. Modeled daily soil evaporation, using either energy balance or soil measurements to obtain β, gave a root-mean-square error of 0.6 mm?day?1 when compared with soil evaporation measured using the energy balance method. When daily soil evaporation from soil moisture measurements was compared with soil evaporation estimated from energy balance measurements, the root-mean-square error was 1.3 mm?day?1. Direct soil monitoring method had bigger error, but the method is less costly.     

Experimental Investigation of the Interaction of Soil Air Permeability and Soil Vapor Extraction

Soil vapor extraction column experiments were performed to investigate contaminant removal and its interaction with soil air permeability. Water, TCE, and PCE, and a mixture of TCE and PCE were used as contaminants. Three gradations of Ottawa sand were used at relative densities of 0.60 and 1.0:?medium, fine, and uniform. Soil air permeability was found to increase linearly with time by 25–150?% to a maximum value when the contaminant was completely removed. The largest increase in soil air permeability was found for fine and/or dense samples. The experimental data were used in a previously developed model by Farhan in 1998 and Farhan et al. in 2001 to predict column behavior. In general, the model predictions were in good agreement with the experimental results. They revealed that the assumption of local equilibrium between the pore air and contaminants is valid for a wide range of pore velocities (2.0–9.2 cm/s).     

Influence of Exogenous Lanthanum on Fertility Parameters of Red Soil and Paddy Soil

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Plate Load Tests on Cemented Soil Layers Overlaying Weaker Soil

This paper addresses the interpretation of plate load tests bearing on double-layered systems formed by an artificially cemented compacted top soil layer (three different top layers have been studied) overlaying a compressible residual soil stratum. Applied pressure-settlement behavior is observed for tests carried out using circular steel plates ranging from 0.30 to 0.60 m diameter on top of 0.15 to 0.60-m-thick artificially cemented layers. The paper also stresses the need to express test results in terms of normalized pressure and settlement—i.e., as pressure normalized by pressure at 3% settlement (p/p3%) versus settlement-to-diameter (δ/D) ratio. In the range of H/D (where H = thickness of the treated layer and D = diameter of the foundation) studied, up to 2.0, the final failure modes observed in the field tests always involved punching through the top layer. In addition, the progressive failure processes in the compacted top layer always initiated by tensile fissures in the bottom of the layer. However, depending on the H/D ratio, the tensile cracking started in different positions. The footing bearing capacity analytical solution for layered cohesive-frictional soils appears to be quite adequate up to a H/D value of about 1.0. Finally, for a given project, combining Vésic’s solution with results from one plate-loading test, it is possible (knowing of the demonstrated normalization of p/p3%-δ/D, where the pressure-relative settlement curves for different H/D ratios produce a single curve for all values of H/D) to estimate the pressure-settlement curves for footings of different sizes on different thicknesses of a cemented upper layer.