Abstract:This paper describes an experimental pursuit of a mechanistic model for interpreting and quantitat ively describing nonlinear, slow, and hysteretic sorption phenomena associated with heterogeneous soils and sediment in subsurface systems.The soil/sediment organic matter was characterized using carbons types derived from ¹³C CPMAS NMR spectroscopy.All sets of equilibrium sorption data were fitted using three different sorpt ion model: the linear model, the Freundlich model or its linearized form, and the dual reactive domain model (DRDM).The linear model was not appropriate for describing any of the experimental sorption data, while the Freundlich model and the dual reactive domain model was found to be adequate for all samples.From DRDM it was observed that sorption mechanism changes with soil organic matter and with increasing contaminant concentration.The apparent sorption-desorpt ion hystersis was quantified for each sample.Sorption-desorption hystersis each varie from sample to sample, and they also appear to correlate with the chemical characteristics of soil organic matter.On the other hand, the pore structure of soils may be a critical factor in sorption-desorption hystersis of hydrophobic organic contaminants.

Abstract:This paper studied degradation of benzo[a] pyrene (B[a] P) in soils with and without alfalfa (Medicago sativa L.) and with and without the inoculat ion of arbuscular mycorrhizal (AM) fungi (Glomus caledonium L.).After a 90 day incu-bation period this pot experiment showed that: a higher concentrat ion (100 mg kg^-1) of B[a] P decreased the frequency (%) of arbuscular mycorrhizal roots on alfalfa.It also revealed that alfalfa and AM fungi enhanced degradation of B[a] P in the soils.With AM fungi and alfalfa, B[a] P having initial concentrat ions of 1 mg kg^-1, 10 mg kg^-1, and 100 mg kg^-1 experienced degradation rates of 86.2%, 86.6%, and 57.0%, respectively.However, with AM fungi and no alfalfa, the degradation rates of B[a] P having the same initial concentrations were 53 5%, 53.0%, and 33.0%, respectively.The results also showed that the degradation rate of B[a] P in soils without inoculated fungi was lower than that of soils with the inoculation of AM fungi.Without AM fungi inoculation on alfalfa B[a] P having initial concentrations of 1 mg kg^-1, 10 mg kg^-1, and 100 mg kg^-1 had degradation rates of 75.9%, 77.7%, and 53.4%, respectively.Meanwhile, without AM fungi inoculation and without alfalfa, the degradation rates for B[a] P having the same initial concentrations were 54.9%, 52.6%, and 34.1%, respectively.In ad-dition, the degradation rates for the low and middle concentration B[a] P treatments (1 mg kg^-1 and 10 mg kg^-1) were significantly higher than that of the high concentration B[a] P treatment (100 mg kg^-1) (p < 0.05).B[a] P added to the soil also significantly affected the activities of polyphenol oxidase.The enzyme activities in soils with higher concentrations of B[a] P were significantly lower than those of the other three treatments.Thus, the inoculated AM fungi could enhance the soil enzyme activities, thereby enhancing degradation of B[a] P in soils.

Abstract:Total community DNA was extracted and purified from soils contaminated with different levels of mixed heavy metals by FastPrep ®system, and then amplified by using eubacterial 16S rDNAs primers.Their PCR products were analysed by DGGE to obtain bacterial community patterns.The results showed that the FastPrep ®120 instrument with the FastDNA SPIN Kit for soil can be used to rapidly, effectively extract and purify DNA from polluted soils.The electrophoresis lanes obtained by PCR-DGGE were legible and distinguishable.The profiles of PCR-DGGE indicated that heavy metals accumulat ion at different levels markedly caused damage to farmland soils DNA, affecting the soil microbial richness and structure of dominating bacterial populations in the farmland ecological systems, and changing the structural diversity of microbial community.The FastPrep ®system is also suitable for rapid efficient extraction and purification of soil total community DNA from farmland soils polluted with mixed heavy metals and in turn the DNA can be used directly for PCR-DGGE analysis.

Abstract:Dynamics in Benzo[a] pyrene (B[a] P) concentrat ions in soil as influenced by ryegrass plants (Lolium multiflorum Lam) were studied in a greenhouse experiment.During the 120 days of plant growth, the extractable B[a] P concentrations in the soils decreased with time and were much less in soil grown with ryegrass plants.In the planted soil with application rate of B[a] P 1, 10, 100 mg kg^-1 soil, B[a] P biodegradability amounted to 82.3%, 74.0% and 55.9%, respectively.The planted soil had higher activity of polyphenoloxidase as compared with the unplanted soil.B[a] P concentrations in the plants ranged from 0.06 to 3.60 mg kg^-1 and declined with the increasing number of days of plant growth.Ryegrass enhanced rhizo-degradation of B[a] P in the contaminated soil.Increase in ryegrass growth and polyphenoloxidase activity in the rhizosphere soil can improve the bioremediation capability of of B[a] P-contaminated soil by ryegrass plants.

Abstract:Soil samples were taken from 0~30 cm layer from selected plots with various fertilization treatments from a 10 years fixed site field trial in the National Purple Soil Fertility and Fertilizer Efficiency Monitored Base.Kinetics of K adsorption and native K desorption of the soil samples were studied.Results showed that K⁺ adsorption and desorption equilibrated in 24~32 min and 46~64 min, respectively, and the capacity of K⁺ equilibrium adsorption and desorption were 14.1~19.2 cmol kg^-1 and 11.6~17.5 cmol kg^-1, respectively.Correlation analysis indicated that soil cation exchange capacity (CEC) and clay content were important factors that affected the time and the capacity of K⁺ equilibrium adsorption; soil CEC and exchangeable K content were important factors that affected the time and capacity of K⁺ equilibrium desorption.As mentioned above the effects of long-term different fertilizer application on soil CEC, clay content and exchangeable K content affected the time and capacity of K⁺ equilibrium adsorption and desorption in purple soil.

Abstract:Natural loess in the northwest of the Loess Plateau was sampled, measured and studied for aggregate amount, relationship between the aggregates and CaCO₃ dissolution, composition of the aggregates, and CaCO₃ distribution on the surface and in the interior of the aggregates with aid of Scanning Election Micrograph (SEM).The results show that: CaCO₃ takes part in the formation of almost all aggregates; the bigger the aggregates are, the higher the CaCO₃ amount is.whereas the number of aggregates is inversely proportional to CaCO₃ dissolution amount.With decrease in CaCO₃ distribution on aggregate surface, the amounts of microaggregates, silts and clay attaching to the aggregate surface reduce.Inside the aggregate, there are three types of cementation between CaCO₃ and mineral particles: CaCO₃ is adsorbed to mineral particle surface, CaCO₃ distributes among mineral particles and mineral particles attach to CaCO₃ surface.The experimental results testify that the main cement of loess aggregates is CaCO₃.

Abstract:Geostat istics was used in studying spatial variation of soil organic carbon, total nitrogen, pH and electrical conductivity in a degraded sandy grassland ecosystem under two different grazing patterns, heavy grazing (HGR) and moderate grazing (MGR) to examine effect of grazing intensity on spatial heterogeneity of the properties.One hundred soil samples were taken from the soil layer 0~15 cm in depth of a grid of 10 m×10 m under each grazing pattern.The results showed that soil organic carbon and total nitrogen contents were significant lower and their coefficients of variation significant higher under HGR than under MGR.Geostatist ical analysis of soil heterogeneity revealed that organic carbon and total nitrogen show strong spatial dependence with exponential or spherical semivariograms on the studied scale.87.2%~88.2% of the variation in soil organic carbon was found within the distance from 22.2~29.4 m, and 65.5%~85.9% of the variation in total nitrogen was found within the distance from 25.5~39 m.The distance of spatial autocorrelation in soil organic carbon and total nitrogen was greater under HGR than under MGR, suggesting that overgrazing resulted in an increase in soil heterogeneity.Soil pH and electrical conductivity did not show spatial autocorrelation within the studied scale, and they were probably controlled by a bigger scale and process.The distribution of vegetation patchs and the bare sand ones resulting from grazing was the main cause of the increase in soil heterogeneity and indicated extent of desertification of the grassland.The changes in heterogeneity in the distribution of soil properties may in turn influence restoration process and distribution pattern of the vegetation.

Abstract:Particle-size distribution is a fundamental soil physical property, which may be used as the basis to determine other soil properties such as water retention characteristics.Describing soil particle-size distribution by parametric models has various advantages.In the present study, suitability of five parametric models is evaluated based on the data of particle-size analysis of 300 samples of three different type soils collected at Fengqiu Experimental Station, Chinese Academy of Sciences.Results indicate that the four-parameter Fred4P model shows the best representation of particle-size distributions of the three types of soils.The three-parameter Fred3P model and MLog model produce comparative results for silty clay loam and silt loam soils, but results not as good for sandy loam soils.Gomp model is even worse than Fred3P and MLog models in calculation error.The two-parameter MVG model yields the largest errors among the five models, and therefore is not suitable for describing soil particle-size distributions in Fengqiu area.

Abstract:Soil water retention curves play an essential role in determination of soil hydraulic characteristics.Among the developed mathematical models, van-Genuchten model historically has been the most widely adopted.Its four parameters are the key to application of this model.With the same set of experimental data (namely soil water suctions and corresponding soil water contents in cinnamon soil in northeast China), this paper introduced in detail the applicat ion of nonlinear curve fitting and nonlinear regression function, two useful functions of Matlab software, in obtaining values of the four parameters, based on which van Genuchten models were established respectively.By taking advantage of the powerful plotting function of matlab, visual comparison of them was easily made, showing differences between them were very small.Finally, using the methods of variance analysis and residual analysis, the calculated values by the models and measured values were analyzed.Results showed that in both nonlinear curve fitting and nonlinear regression good significant levels were achieved both to p < 0.000 1 and the sums of residual squares were both lower than 0.000 5.Especially the results from the nonlinear regression function were better than those from the nonlinear curve fitting.Therefore, it is practical and feasible to obtain values of the parameters of van Genuchten model for soil water retention curves using Matlab software, which may serve as a new promising approach to application of numerical methods for the soil scientists.

Abstract:The soil cannot be totally covered by plastic mulch in the field.And normally in the mulch holes should be preset for plants to emerge after sowing, and irrigation holes added for irrigation.The term of aperture ratio is often used to represent the above issue.So far very few national or international papers about evaporation from soil under perforated plastic mulch have been reported.In order to study characteristics of evaporation from the soil with initial homogeneous soil water content, a laboratory system of evaporation has been set up.Based on the dynamic observations of soil water and soil temperature, their variation regularities during evaporation and at the end of the evaporation were described, and calculations and analyses of soil temperature variation and soil water content distribution, functions of cumulative evaporation, relatively evaporation and cumulat ive evaporation per unit area of the film holes to aperture ratios performed.The results showed that under the influence of evaporation, the cumulative evaporation varied linearly with the square of the evaporation time, which corresponded to the bare soil evaporation theory presented by Gardner.These results have extended Gardner equation and expanded its application ranges, thus being very useful for further study on water and heat transport in plastic mulched field.

Abstract:Soil vapor extraction (SVE) as an emerging in-situ remediation technology has been applied to remove subsurface pollut ion of petroleum chemicals all over the world.Although the technology has found more and more application, theoretical invest igations to improve its designs and practices should continue systematically.For contaminants and fluid mediums in SVE, there exist different types of transfers, conversions and physicochemical behaviors because of the complicated multiphase system of gas-water-oil(NAPL)-solid.To make certain these processes, interdisciplinary approaches should be employed.In this paper, a basic mathematical model of SVE is presented according to the dynamic theory of fluids in porous media and the transition theory in chemical engineering with some applied assumptions.Some momentum equations, mass conservation equations and NAPL depletion equations aimed at describing SVE processes have been derived.

Abstract:The turnover of the microbial biomass plays key roles in the cycling of organic matter and nutrients in soil.Although the microbial biomass-C is generally accounted for only 1%~4% of total soil organic, the balance between the rate of microbial processes determines the turnover and consequently the accumulation of soil organic matter and nutrients (e g.N, P and S).In this study, the procedure for measuring the turnover time of soil microbial biomass-C has been developed.¹⁴C-labelled glucose was used to label the biomass-C by incubating soils at 25 and 100% humidity.The labelled biomass-C, total biomass-C, and extractable-C were measured by every 20 days during a 100-day incubation period, using the fumigation-extraction method.Data obtained were then used to calculate the turnover rate constant of biomass-C, and hence its turnover time Under the incubation condit ions, the turnover t ime of biomass-C, calculated from the gross turnover rate constant of labelled biomass-C, varied between 93 and 400 days.This is equivalent, by extrapolation, to 1.0~4.1 years under the field conditions where soils were from.It was demonstrated that the turnover time of soil biomass- C was largely affected by soil texture but little by management.Measuring the turnover times of soil biomass-C provides a good indication of microbial activities in relating to the turnover and accumulation of soil organic matter.

Abstract:Purpose of the present work is to show evidence supporting the hypothesis that nitrate reduction products pro-duced by one type of partial denitrifiers could be used as electron acceptor by other type of part ial denitrifiers.This mechanism of soil denitrificat ion, here referred to as successive denitrification, differed from the commonly accepted mechanism in that the former was conducted by different types of partial denitrifers while the later was done by complete denitrifiers.Soils sampled from the Changshu Agroecosystem Experimental Station, Institute of Soil Science, Chinese Academy of Sciences were enriched with soil extract plus N₂O as the sole electron acceptor.Bacteria in the enriched materials were isolated using 1/10 diluted nutrient broth under anaerobic condit ion.The isolates were characterized by reduction of nitrogen oxides.Partial denitrifying strains were obtained.The strain coded as 21-6-9-2 was able to reduce NO₃^- to NO₂^- only, the strain coded as 1-9-5-3 able to reduce NO₂^- to N₂O only and the strain coded as 21-6-3-6 able to reduce NO₂^- to N₂ only.When strain 21-6-9-2 and strain 1-9-5-3 were mixed with proper ratio into sterile soil, without adding any additional carbon substrate, NO₃^- was reduced to N₂O, demonstrating that the partial denitrifiers could cooperate in use of the substrate and play a similar role to that typical denitrifiers do.

Abstract:Residues and distribution of organochlorine pesticides in the soils of the vegetable garden in the southern Jiangsu were analyzed.The effects of soil utilization, cropping system, vegetable species and history of vegetable cultivation on residues of the pest icides were also discussed.A county with long history of vegetable plantat ion, developed in urbanization and industry, was selected as case study.89 samples were collected throughout the whole county with GPS value for each location.The results showed that organochlorine pesticides were found widely in the soils, with an occurrence of 100%.The mean of the total concentrations(∑-OCP) was 174.4 μg kg^-1 with a range of 23.2μg kg^-1~1126.7μg kg^-1.p, p'-DDE and p, p'-DDT are the main components and took over 82% of the total.The kailyard soil had the highest residues of ∑-DDT, while the paddy soils had the lowest levels.The residues varied significantly with vegetable species in kailyard soils.The residues in soils growing leaf vegetable were much higher than others.The rotation of vegetable and rice could decrease the risk of organochlorine pollution.

Abstract:Twelve cultivars of Chinese cabbages were hydroponically grown with three different NO₃^--N/NH₄⁺-N rat ios, i.e., 100:0, 50:50 and 0:100.The result showed that different NO₃^--N/NH₄⁺-N rat ios had a great effect on the fresh matter weight, chlorophyll content (SPAD readings) and nitrate content of the 12 cultivars of Chinese cabbages.In the same nitrogen source the difference was also significant among the different cultivars.The chlorophyll content of the cabbages increased with the increasing NH₄⁺-N/NO₃^--N ratio.Except Liangbaiye 1 and Wuyueman both of which had a higher fresh matter weight in a pure nitrate solution than the other solutions with 0:100 or 50:50 NO₃^--N/NH₄⁺-N ratios, the other 10 cultivars of the cabbages grew best in the solutions with 50:50 NO₃^--N/NH₄⁺-N.In most of the cabbages the nitrate content decreased significantly with the increasing of NH₄⁺-N/NO₃^--N ratio.In conclusion, a proper NO₃^--N/NH₄⁺-N ratio could not only increase the biomass weight and chlorophyll content but decrease the nitrate content of Chinese cabbages as well.

Abstract:The effects of AMF (Glomus mosseae) on growth and salt tolerance of pot wild jujube seedlings (Zizyphus spinosus Hu) at different levels of NaCl added into soil (0, 1.5, 3.0, 4.5 g kg^-1 of dry weight soil) were studied.The results showed that the height, fresh weight, dry matter weight of roots, leaves and shoots of AMF inoculated and uninoculated plants decreased while the Na concentrat ions of roots, leaves, shoots and whole plant increased with the increasing doses of NaCl added into the soil.The height, fresh weight, dry matter weight in different parts of plant and the leaf chlorophyll concentrations were significantly higher for AMF inoculated plants than for uninoculated plants grown under the same levels of NaCl.The Na concentrations of shoot and leaf were lower while the Na concentrat ions of root and the Na content of whole plant were significantly higher for inoculated plants than for uninoculated plants.The growth and leaf chlorophyll concentrations were higher for AMF inoculated plants grown under highest leve of NaCl (4.5 g kg^-1) than for uninoculated plant grown under no NaCl added into the soil.No significant differences in growth and root colonization were found between plants with salt treatment just after sowing and plants with salt treatment 40 days after sowing.The gross dry weight of AMF plants with salt treatment just after sowing increased 164%, 149%, 48%, 35%, re-spectively, at the 0, 1.5, 3.0, 4.5 g kg^-1 NaCl of the dry weight soil, compared with that of uninoculated plants, and that with salt treatment 40 days after sowing increased 194%, 127%, 72%, 46%, respectively.The results indicated that wild jujube seedlings were salt tolerant plant, the growth of the plant heavily relied on AM, and the AMF inoculated plants had greater tolerance to salt stress than uninoculated plants.

Abstract:Estimat ing spatial variability of saline soil electrical conductivity (EC) which was intensely correlative with salinity content is an important issue in costal region.In this study, semivariogram was firstly used to explore the spatial correlation of EC for four depths of 0~20 cm layer, 20~40 cm layer, 40~60 cm layer and 60~100 cm layer on a 20 m by 20 m sampling grid, EC distribution at the four layers were then est imated using ordinary kriging, and then cross-semivariogram was analysed to explore coregionalized relationship between top layer and deeper layers.Finally cokriging was used to improve saline soil EC estimation at deeper layers by treating the samples of 0~20 cm depth as auxiliary variable and the original and reduced samples of the other three layers as primary variable.Compared with the ordinary kriging, the root-mean-square error produced by cokriging decreased by 9% to 25.1%, the average standard error decreased by 9.4% to 21.9%, correlation coefficient between the predicted value and the observed value increased by 46% to 85%.The analysis results indicated the reduction of the original sampling density of 40% would have resulted in no evident loss of spatial information.Cokriging was shown to be a more accurate and economic method, and it allowed easily obtained variables to be used to estimate the difficultly obtained variable based on the correlation on between two variables, and not only can greatly improve prediction accuracy, but also can save the sampling cost.

Abstract:Studies on isolation and characteristics of nitrogenase activity, phosphate solubilizing power and auxin (IAA) producing of associat ive symbiotic nitrogen bacteria (ASNB) from wheat rhizosphere in saline soil were carried out in Lanzhou area, Northwest China.The results show there are 12 ASNB strains obtained; Nitrogenase activities of the strains vary distinctly (C₂H₄, 124.6~651.6 nmol h^-1 ml^-1); Among the strains, two show phosphate solubilizing power with capacity reaching 16.30 g ml^-1 and 9.82 g ml^-1, respectively; nine show ability to produce auxin (IAA) although the ability varies with the strains (IAA concentration 1.40~15.13 g ml^-1).In the view of nitrogenase activity, phosphoru-s solubilizing power and IAA producing, Pseudomonas sp.ChW1, Azotobacter sp.ChW5, Zoogloea sp.ChW6 Azotobacter chroococcum ChW11 and Azospirillus sp.ChW15 show higher potential as biofertilizer inoculums for wheat in the area.

Abstract:Based on the development of agro-information technology in foreign countries, the development and application of agro-information technology and major aspects of integrat ion and industrialization of agro-information techniques are elaborated.And besides, the direction for development of modern agriculture in China is brought onto the table.

Abstract:In order to understand the role of microbial communities in different environments it is essential to have knowledge of functions and functional diversity of microbial communities.However, the quant itative description of microbial communities is one of the most difficult tasks facing microbial ecologists.Now the BIOLOG redox technique proposes a simple and quick method for studying soil microbial community function diversity, based on the community-level carbon source utilization patterns.But BIOLOG is also a culture-based method, and the presentation of metabolic diversity patterns doesn't necessarily reflect the functional diversity of the soil microbial communities.Consequently, there are many problems as well as benefits using the approach, and a series of skills are needed for the application.The application of BIOLOG to the study on soil microbial community functional diversity is summarized in this paper, including theories, procedures, problems, and countermeasures during the application.The problems worthy of further research are also put forward.The objective of the study is to accelerate understanding how to apply BIOLOG properly to the study on soil microbial community functional diversity and provide a scientific foundation and theoretical guide for further research of the subject correctly.

Abstract:五氯酚(Pentachlorophenol,PCP)作为农药和木材防腐剂曾在世界范围内大量应用,因其对生物体的广谱毒性和诱突变性被认为是环境中主要的持久性有机污染物(POPs)之一,对PCP在土壤、沉积物和微生物生长介质中的生态毒性和降解的研究一直是国际关注的热点。PCP是包括我国在内的许多国家的环境优先监测污染物之一,目前在农业上虽已基本停止使用,但是在化工行业仍在使用,而且以往使用的PCP对环境造成的影响还会持续相当长的一段时间。

Abstract:土壤水分状况是影响钾离子在土壤固液相分配转化和作物吸收利用的重要因子^[1～3]。对于植物所必须的钾素来说,土壤水溶性钾和交换性钾是土壤钾库中最活跃的组分^[4～7]。钾在土壤固、液相间的转化速率与数量分配关系取决于土壤水分的存在形态以及K⁺与土壤固液相表面的作用方式,并反映了土壤固钾能力^[8～11]。在以往的研究中,通常采用田间持水量或饱和含水量情况下土壤提取液(即土壤溶液)作为平衡溶液^[9～11]。

Abstract:对土壤性质空间变异的充分了解,是土壤养分管理和合理施肥的基础。90年代以来,随着发达国家精确农业技术的开展,土壤特性的空间变异和空间插值技术研究得到众多农学家和土壤科学工作者的关注和重视^[1,2]。由法国学者Matheron于20世纪60年代建立起来的地统计学(Geostatistics)方法,已被广泛用于土壤养分空间变异研究的定量分析;它是以区域化变量、随机函数和平稳性假设等概念为基础,以变异函数为核心,以克里格插值为手段,来分析研究自然现象的空间变异问题^[3,4]。

Abstract:在利用多波段、多时相、高光谱的遥感数据来提高遥感对地物的识别能力的同时^[1],人们注意到角度信息在遥感图像识别和分类中起到的影响和贡献^[2],即地物在2π空间上的三维光谱特征。在早期的遥感,主要采取垂直收集对地观测数据。根据不同的地物具有不同的吸收、反射和发射电磁波的能力,来分辨地球表层的地物分布。这里基于一个假定:假定目标地物的反射光谱在2π空间内分布是一致的(朗伯体)。随着遥感的深入,这种假定引发的结论与实际相差较大。而且在单一角度下常出现不同地物对应相同的光谱反射率,上述方法存在误判。

Abstract:NH₄⁺的矿物固定与释放是土壤氮素内循环中的重要环节,它在一定程度上影响着施入土壤中NH₄⁺-N的转化途径^[1,2]。对土壤矿物固定态铵的研究在国外主要是对温带地区旱地土壤和自然土壤的研究,国内则主要限于华北和西北地区旱地土壤及不同气候区的代表性地带性土壤的研究,但对某一地区范围内的代表性农业土壤固定态铵的研究则少见报道。湖南省地处中亚热带湿润气候区,是我国的农业大省,据全省第二次土壤普查,旱地土壤面积为75.68×10⁴hm²,占总耕地面积的21.55%^[3]。

Abstract:利用石膏改良苏打盐碱化土壤,早在19世纪后期,Hilgad^[1,2]就开始指导农民改造黑碱了。当时他将含有NaCl、Na₂SO₄的土壤称为白碱,而将含有Na₂CO₃、NaHCO₃的土壤称为黑碱,即苏打盐土或碱化盐土,并为石膏改良黑碱建立了两个化学方程式,即Na₂CO₃+CaSO₄=CaCO₃+Na₂SO₄(1)2NaHCO₃+CaSO₄=Ca(HCO₃)₂+Na₂SO₄(2)1912年以后,盖得罗依兹^[3]将土壤胶体与溶液的交换反应引入土壤学。确认碱化土壤不良的物理化学性质来源于交换性钠,并将交换性钠称为“碱”,同时将Na₂CO₃、NaHCO₃称为碱性盐。

Abstract:土壤温度影响植物根系的生长和分布,影响土壤化学过程的速度和成土母质中原生矿物的风化,所以在美国土壤系统分类中,把在土表下50cm深度处的年均土壤温度作为分异特性,用于不同分类级别的区分^[1],在我国的土壤系统分类中也采用了此办法,把土壤温度状况作为土壤分类的重要依据之一^[2]。然而如何取得土表下50cm处年平均土壤温度是个难题,若在每个要测验的单个土体处建立土壤温度观测点当然可靠,但需要大量人力、物力和时间^[3],很难做到。有的是用大气温度来推算,例如在美国大部分地区土壤温度比气温高2(11℃),以此来推算土壤温度^[4],但仅用大气温度来推算土壤温度有局限性。