• Volume 55,Issue 3,2018 Table of Contents
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    • >Reviews and Comments
    • Generalizaion of Technical Systems for Soil Pollution Prevention and Control in Developed Countries

      2018, 55(3):527-542. DOI: 10.11766/trxb201712130487

      Abstract (2811) HTML (2610) PDF 1.69 M (6695) Comment (0) Favorites

      Abstract:International experience shows that a complete and scientific technical system for prevention and control of soil pollution is the foundation key to comprehensive promotion of protection of soil quality and protection and control of soil pollution, particularly in China where the work to prevent and control soil pollution is still at its starting stage and confronted a series of challenges. Although the responsibility is heavy and long-lasting, it is a must for building up soil pollution management capacity. In this sense, to effectively prevent and address the problem of severe soil pollution in deserted industrial sites, and promote safety and sustainable utilization of urban lands, this paper presents a comprehensive and systematic overview of the technical systems for prevention and control of soil pollution in the USA, UK and other European countries, including their elements, composition, evolution features, laws and regulations, technical guidelines and standards, and management system. Though the technical systems of these countries are quite similar, but do differ from each other in certain aspects. The establishment of a complete effective sets of soil pollution prevention and control systems must be based on the principle of end-to-end sustainable management of risks and encompass the three interrelated and mutually affected elements, i.e. legal support, technical system and management means. Laws and rules are the core principles and key guidance in standard formulation and measure enforcement; standard guidelines further detail and specify feasibilities of the laws and rules; and management means are assorted guarantees of the laws, rules and standard guidelines at the practice level. The perfect site soil pollution prevention and control systems of the developed countries may serve as reference of great guiding significance to China in building its soil pollution prevention and control system. By referring to the successful experience of the developed countries, and proceeding from the actual needs and specific national conditions, this paper elaborated development direction and important contents of a "legislation - technology - management" integrated soil pollution prevention and control system.

    • Application of Soil Microbial Studies to Farmland Quality Evaluation

      2018, 55(3):543-556. DOI: 10.11766/trxb201710310320

      Abstract (2472) HTML (1252) PDF 1.39 M (5737) Comment (0) Favorites

      Abstract:Soil microbial flora is usually used as a biomarker of sustainability of farmland. With the research on soil microbiology gradually maturing, it becomes advisable to evaluate farmland quality from the angle of soil microbiology and to analyze whether or not the tract of farmland under study may have a bright future of sustainable development from the aspect of soil microcosmic mechanisms. However, the farmland quality evaluation systems, currently available, have not yet illustrated how to evaluate farmland quality from the angle of soil microbiota. Based on reviews of the literature concerning farmland quality and soil microbiology, this paper elaborated how to use soil microbiota as feedback of farmland quality, especially when related to farmland management, food production and soil pollution. In line with the existing international and domestic standards of the industry, the paper marked out microbial biomass , soil basal respiration, hydrolase activity and microbial diversity as, microbiological indices for the farmland quality evaluation systems. In using the common methods to evaluate soil quality, the objects studied are always kept in a stable state. Moreover, the evaluations using these methods seldom involves any soil microbial indices. They usually need the support of basic data or are more suitable for analysis of large-scale soil properties and positioning. In addition, most of the evaluation methods are more suitable for scientific research, but not so for application to farmland improvement projects. Based on the designing of ecological comparative experiments and the method of Duncan test, a new flowchart was plotted out for farmland quality environment. By comparing control with treatment in the experiment, variance rate and variation value could be obtained for analysis of effect of the treatment. Post hoc validation tests, were performed to analyze significance of difference between treatments and control. In the end, an effect-evaluation table was established, reflecting effects of treatments on farmland quality. This study indicates that the farmland quality evaluation system encompassing soil microbial indices is more sensitive and comprehensive than the traditional ones, and the combination of soil microbial properties and soil physico-chemical properties makes the environment more reliable. It is worth to note that the new system is more suitable for quantitative indices, and needs to analyze results of the evaluation by taking into account changes in soil physical and chemical properties. For the relative abundances of soil microbial communities obtained via sequencing, this method still has certain points worth pondering over. It is advisable to adopt the method of community classification in analyzing soil microbial communities. Soil microbial properties readily reveals mechanism of changes in farmland. Even though in the course of using soil microbiota to evaluate farmland quality, there are still a lot technical and analytical difficulties to overcome, it cannot be ignored that soil microorganisms play an irreplaceable role in the evaluation of farmland quality and will become an important analytical tool for defining quality of farmland in future.

    • >Insights and Perspectives
    • Thinking of Construction of Soil Pollution Prevention and Control Technology System in China

      2018, 55(3):557-568. DOI: 10.11766/trxb201711300488

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      Abstract:For long the soil resources of China have been confronted with over-exploitation, severe pollution and ever-increasing development pressures. The adverse impacts of soil pollution are subtle and escalating slowly, but already to such an extent that they have gravely affected human health, and sustainable utilization and fundamental ecological functions of the soil in modulating biogeochemical cycling of nutrients, supporting plant growth, and sustaining healthy human habitation. The promulgation of the "Action Plan for Soil Pollution Prevention and Control" in 2016 reflects great attention the Chinese government pays to the issue of soil protection. The plan laid down a systematic arrangement from the strategic point designed at the summit level to further promote development of soil pollution prevention and control project in China. To rapidly and effectively improve the soil environment, and guarantee safety of the agricultural production as well as human living habitats, centered around the general course and the core concepts of the plan, the paper has brought forth five guiding ideas and five basic principles for construction of a China-specific soil pollution prevention and control system. New modes of soil pollution prevention and control were explored through in-depth interpretation of the programmatic document and construction of land-use specific soil pollution prevention and control systems. The paper elaborated the theme, targets and support system of the conceptual framework of soil pollution prevention and control, and pointed out that the soil pollution prevention and control technology system should encompass prevention technology, monitoring technology, remediation technology and technology for safe exploitation of farmland resources, as well as the following aspects, pollution prevention and control, environment investigation, risk assessment, management and remediation, end-to-end monitoring and sustainable utilization. It could be concluded that the studies on soil pollution prevention and control system in China were centered mainly on studies of the legal system, neglecting system research on technical system and management system. Guided by the core idea of the “Action Plan for Soil Pollution Prevention and Control ", a systematic and effective soil pollution prevention and control system should: (1) unfold management, remediation and risk control of contaminated soil from the perspective of "Harnessing"; (2) prevent emerging of new pollution and migration and diffusion of existing pollution and enforce rigid supervision of pollution sources from the perspective of "prevention"; (3) form an end-to-end soil pollution prevention and control system supported by financing mechanism, public participation and other accessorial mechanisms; and (4) pay attention to uniqueness of each tract of land individually in function on the basis of the clear knowledge of status of soil pollution, e.g. soil pollution prevention and control is aimed at a healthy inhabitant environment and sustainable land use for construction land, and at ensuring quality of agricultural produce and human health for farmlands.

    • >Research Articles
    • Higher Category Partition for Purple Soils in Chongqing in Chinese Soil Taxonomy

      2018, 55(3):569-584. DOI: 10.11766/trxb201708170333

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      Abstract:【Objective】It seems that so far little has been done on classification of purple soils in Chongqing in line with the Chinese soil taxonomy. Therefore, a systematic study in this paper was conducted to attribute the purple soils in Chongqing in the Chinese Soil Taxonomy (CST) at the higher category level, and establish references between the Genetic Soil Classification of China (GSCC) and CST for the soils, in an attempt to promote development of quantitative classification for the soils, and provide certain scientific references for survey and mapping, resource evaluation, rational utilization and improvement of regional soils. 【Method】Field soil surveys were conducted to specify forty-one soil profiles of the purple soils in Chongqing, and obtain soil-forming conditions and soil morphological characteristics of the profiles. Soil samples were collected from the profiles by horizon for analysis of physical and chemical properties. According to the “Keys to Chinese Soil Taxonomy (3rd ed.)”, diagnostic horizons and diagnostic characteristics for the tested soils were determined, and the soils were attributed and named in CST level by level. The references between GSCC and CST were established for the purple soils at the subgroup level. 【Result】The forty-one purple soil profiles were sorted into 4 orders (Anthrosols, Argosols, Cambosols and Primosols), 6 suborders (Orthic Anthrosols, Perudic Argosols, Udic Argosols, Perudic Cambosols, Udic Cambosols and Orthic Primosols), 12 groups and 19 subgroups in CST. At the order level, most of the soil profiles were sorted into Cambosols, which was followed by Primosols. Cambosols or Promosols in CST corresponded to three subgroups (acid purple soil, neutral purple soil and calcareous purple soil) in GSCC, while Argosols in CST did to only one subgroup, namely, acid purple soil in GSCC. Among the 25 purple soil profiles sorted into the Udic Cambosols suborder in CST, only 5 could further be sorted into the Purpli-Udic Cambosols group, and most (or 15) into the subgroup of Red Ferri-Udic Cambosols under the Ferri-Udic Cambosols group, and into three purple soil subgroups in GSCC, separately. Topography, elevation and parent rock could obviously affect the diagnostic basis for classification of purple soils in CST at higher category levels. The first two affected mostly soil moisture regimes, while the latter did color, profile development, physical and chemical properties of purple soils. In addition, appropriate farming activities could turn purple soil into Fimi-Orthic Anthrosols. 【Conclusion】Compared with GSCC in classifying purple soils, CST is higher in capability of distinguishing the soils, identifying accurately typical individuals and providing reference information for utilization and amelioration of purple soil resource in Chongqing. Topography, elevation, parent rock, and human activities are the main factors influencing classification of purple soils in Chongqing in line with CST at higher category levels. In order to further perfect the CST, some suggestions are given for revising identification criterion of lithologic character (L. C.) of purplish sandstones and shales, and solving the problem that the subgroups set under the Ferri-Udic Cambosols group in CST fail to fully reflect the differences in soil properties between the purple soils in Chongqing.

    • Screening of Training Samples Based on Environmental Covariate Geospatial Neighborhood Analysis of Historical Soil Maps

      2018, 55(3):585-594. DOI: 10.11766/trxb201708160188

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      Abstract:【Objective】It is of great practical significance to investigate, manage and exploit soil resources based on knowledge mining and updating of historical soil maps, while screening of representative training samples out of the historical soil maps is a key step to accomplish the task. 【Method】Jingde County of Xuancheng City in Anhui Province was cited as the study area. In this paper, a new method for screening of training samples was developed, consisting of determining quantity of samples and specifying sample locations. The area segmented linear-scaling method, which builds a linear correspondence between the area and the number of samples in each area segment, was applied to determination of quantity of sample in each historical soil map polygon, and then after making geographical neighborhood analysis of elevation and slope, the two important environmental covariates, the stable cells in spatial variation of the environmental covariates were defined as sample locations. Geographical neighborhood analysis index indicates the degree of spatial variation of the environmental covariates in the neighborhood.【Result】Results show that the use of the area segmented linear-scaling method to determine quantity solved the problem that had never been pondered in past researches of how to distribute samples among units that were of the same type, but consisted of a number of polygons. When this method was used to define sample locations in polygons located in topographically flat areas, determination of spatial distribution of sample sites based on elevation or slope did not vary much, whereas in polygons located in mountainous areas, the sample sites defined based on slope were mostly located in places relatively stable in topography and more representative of the entire polygon. Compared with the environmental covariates histogram peak method used in most of the researches, this method is higher in odds ratio and standard deviation, and the samples defined with this method are bigger in volume of information.【Conclusion】The training samples defined with the geographical neighborhood analysis method based on slope are more representative of the entire polygon than those based on elevation, and contain more information than those defined with the environmental covariates histogram peak method in relevant researches.

    • Variation of Soil Organic Carbon in Farmland of Anhui and Its Influencing Factors in The 30 Years from 1980 to 2010

      2018, 55(3):595-605. DOI: 10.11766/trxb201708240323

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      Abstract:【Objective】Soil organic carbon (SOC) is a key index in estimating soil fertility and soil C sequestration. It is, therefore, important to study changes in SOC to accurate assessment of regional soil C sequestration potential and successful sustainable utilization of soil resource. This paper was oriented to characterize spatio-temporal variation of SOC, including density and storage, in the farmland of Anhui during the 30 years after the Second National Soil Survey in the 1980s and to explore relationships between agricultural management and changes in SOC, and expected to be able to provide certain data and support for decision making related to improvement of soil quality and soil C sequestration potential in the East China. 【Method】In this paper, Anhui Province in East China, was selected as a case for the study. Comparative study was done of the data obtained during the Second National Soil Survey and the data derived from the soil profiles collected from the farmland in 2010 and 2011, analyzing changes in soil organic carbon density (SOCD) in the surface layer (0 ~ 20 cm) and total layers (0 ~ 100 cm) of the farmland by means of statistics. Spatio-temporal change of soil organic carbon density and storage in the different layers during 1980 and 2010 was analyzed using the pedological professional knowledge-based (PKB) method and GIS spatial analysis technique. And then relationships between agricultural management and changes in SOC were discussed. 【Result】Results are shown as follows: (1) from 1980 to 2010, the mean of SOCD in the farmland increased by 0.28 kg m-2 in the surface layer, but decreased by 0.42 kg m-2 in the 0 ~ 100 cm layer in throughout the province. The increment of SOCD was higher in upland in paddy field. (2)Spatially, SOCD in the surface layer increased in the northern part, but decreased in the southern part of Anhui Province during the 30-year periods, and the increment declined from north to south within the province. SOCD in the 0 ~ 100 cm soil layer increased in the middle part and decreased in the southern part of the Province. About 68% of the farmland increased in SOCD, and the farmlands were distributed mainly in the Huaibei Plain and Jianghuai hilly downland. (3) The storage of SOC in the surface layer of the farmland of the province as a whole increased by 35.30 × 109 kg and that in the 0 ~ 100 cm soil layer did 18.12 × 109 kg. The storage of SOC in the farmland increased mainly in the Huaibei Plain and Jianghuai hilly downland, while it went reversely in the other geographical areas. 【Conclusion】Fertilizer application rate and straw return are the two main factors significantly influencing variation of SOC in the farmland. In this study, it was found that variation of SOC storage was significantly and positively related to organic matter content in crop roots, and that the application of large volumes of chemical fertilizers increased organic matter content in straw and roots of the crop, thus increasing the input of organic matter into the soil and contributing to accumulation of SOC in the farmland.

    • Scale Effects of Estimation of Soil Organic Carbon Storage in Fujian Province, China

      2018, 55(3):606-619. DOI: 10.11766/trxb201708150359

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      Abstract:【Objective】Soil organic carbon (SOC) is an important part of the terrestrial carbon pool. Owing to its critical role in the global carbon cycle and its heavy storage in the terrestrial ecosystem, any slight change in the SOC pool would sure create certain influence on global climate. So, in order to simulate the global carbon cycle and design agricultural management measures, it is essential to estimate soil organic carbon storage (SOCS) accurately. Because of the spatial heterogeneity of soil properties, the study on SOC estimation on a regional scale may help improve accuracy of the estimation of SOC on the global scale, and moreover provide eco-environmental protection, regional decision-making and agricultural sustainable development with data support.【Method】In this study, based on the soil database of Fujian Province, and soil maps of the province, different in scale (1:50 000, 1:200 000, 1:500 000, 1:1 000 000, 1:4 000 000 and 1:10 000 000), SOCS were estimated for analysis of spatial distribution of SOC in the surface soil layer (0~20 cm) and soil profile (0~100 cm). The PKB method, i.e, pedological knowledge based method, was used to relate soil spatial data to soil attributes. As affected by the scale of a soil map, the number of soil patches decreased from 247 969 to 46 408, 15 282, 6 343, 440 and 345, with declining mapping scale and 3 082, 3 082, 2 718, 2 547, 1 000 and 890 soil profiles were made available for collection of soil physico-chemical properties, respectively. No doubt, the change in scale of soil mapping would sure bring about uncertainties in estimation of SOCS.【Result】Results show that based on the six soil maps different in mapping scale SOC in the surface soil layer (0~20cm) was estimated at 552, 637, 573, 573, 614 and 549 Tg C and in the soil profile (0~100 cm) at 1 396, 1 502, 1 321, 1 395, 1 508 and 1 532 Tg, respectively.. Estimation of SOC in skeleton soil, among all the types of soils, was most affected by mapping scale, with relative deviation in the surface soil layer and soil profile being 88.75×104% and 81.96 ×104%, respectively. However, the estimation of SOC density in the surface soil layer of red soil, the largest in land area, was, the lowest in relative deviation, being 4.28%, based on the soil map 1:1 000 000 in scale, while the estimation of SOC density in the soil profile was the lowest in relative deviation, being only 1.53%, based on the soil map, 1:500 000 in scale. The estimation of SOCS in Xiamen and Fuzhou, in terms of administrative region, were both affected by mapping scale, with relative deviation being 26.44% for topsoils and 27.97% for soil profiles, respectively. Relative deviations of the estimations of SOC density in the surface soil layer and profile in all the cities, except Xiamen, based on the soil map 1:500 000 in scale, were the lowest.【Conclusion】In general, regarding Fujian Province as a whole, the estimation of SOC density and storage in the surface soil layer and profile based on the soil map 1:1 000 000 in scale deviated the least from the currently available most detailed large-region data, 1:50 000 in scale, being 0.67% and 0.82% respectively, while that based on the soil map 1: 200 000 in scale did more, reaching 15.57% and 15.34% respectively. Estimation of SOCS in the surface soil layer and profile of Skeleton soil, among all the types of soils, was the most affected with relative deviation, reaching up to 88.75×104 % and 81.96 ×104%, respectively. The estimation of SOC density in the surface soil layer of red soil was the lowest in relative deviation, reaching 4.28% based on the soil map 1:1 000 000 scale and that in the soil profile of the red soil was, reaching 1.53% based on the soil map 1:500 000 in scale. The influence of mapping scale is also significant for Xiamen and Fuzhou. The relative deviation of the estimation of SOCS in the surface soil layer of Xiamen was 26.44%, and in the soil profile of Fuzhou was 27.97%. The relative deviations of the estimations of SOC density in both the surface soil layer and profile in all the cities, except Xiamen based on the soil map 1:500 000 in scale, were the lowest. All the findings in the study demonstrate that mapping scales does have certain influences on estimation of SOCS in the soils of the same area. In the case that administrators of an area do not have any accurate soil databases, it is advisable for them to estimate SOCS in their region and design agricultural management measures based on the soil map 1:500 000 in mapping scale.

    • Spatial Distribution of Macro-pore Properties in Soil Profile on a Slope of Weathering Granite

      2018, 55(3):620-632. DOI: 10.11766/trxb201709070266

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      Abstract:【Objective】Strong soil erosion affects profoundly soil porosity of slope lands. On slopes the same in parent material but different in erosion intensity, soil pore properties in soil profile vary sharply. This study was oriented to explore spatial distribution pattern of macro-pore properties in soil profile relative to landform positions and soil erosion intensity, a slope of weathered granite under erosion in Shengzhou, Zhejiang Province was taken as the study area. 【Method】This study in oriented to characterize macro-pore in soil profiles at different landform positions on the slope, with the help of the Shengzhou Soil and Water Conservation Monitoring Station. Along the slope where the station sits, three typical sites, different in erosion intensity, were selected separately, at the top, middle and bottom. A soil profile or soil column, 70 cm in length, was sampled at each site using PVC pipes with known inner diameter. The columns were then CT- scanned layer by layer with high intensity and their CT images were interpreted with the ArcGIS10.1 image processing technology for analysis of macro-pore distribution and its influencing factors. The pore characteristics indices studied include macro-porosity proportion of macro-porosity to total porosity, anomaly of macro-porosity, circularity of macro-pores, proportion of different classes of macro-pores of equivalent diameter in number, and ratio of macro-pores to total pores.【Result】 The following conclusions were drawn from the analysis and calculation:(1)Macro-pores dominated all the three soil profiles, and pores between 1~ 3mm in diameter were the highest in proportion and pores e between 5~7mm were the lowest. In terms of number of macro-pores, the three typical soil profiles exhibited a decreasing order of the one at the middle > the one at the bottom > the one on the top; in the soil profiles on the top and at the middle of the slope, the proportion of macro-pores number is comparatively small.(2)The difference between macro-porosity and total porosity was very small in all the three soil profiles and decreased with soil depth. The soil layer with macro-porosity higher than the average was distributed mainly in the upper part of the profiles between 0 cm and 30 cm. The difference between soil layers was not obvious and never exceeded 10%, but the deep in the soil profile, the greater the difference.(3)Circularity of macro-pores was a factor affecting the relationship between macro-porosity and total porosity, while the higher the content of clay and silt, the higher the circularity. (4) The proportion of coarse sand was the highest in all the three profiles, amounting to 50% or more,while the proportion of clay the lowest, being no more than 12%. Correlation of macro- porosity with soil particle size was analyzed with SPSS 20.0, revealing that soil macro-porosity was significantly and positively related to content of coarse sand, but negatively to content of clay and silt. The finer the soil particles, the greater the total porosity and the smaller the proportion of macro-pores.【Conclusion】In a word, severe soil erosion alters the characteristics of soil structure, being porous in the upper and layer and compact in the lower layer. Affected by erosion,the soil profiles are dominated with macro-pores, poor in pore structure. The distribution of macro-pores in the soil profiles is obviously affected by the intensity of erosion. The more serious the erosion, the higher the proportion of macro-pores and the more serious the phenomenon of soil water and nutrient loss. All the findings in this study provide a train of thought for evaluation of soil evolution under erosion and contents of the research on soil evolution.

    • Effects of Earthworm Cast Mulch on Soil Evaporation

      2018, 55(3):633-640. DOI: 10.11766/trxb201711030431

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      Abstract:【Objective】It is well known to all that earthworm cast helps soil aggregation and hence affects significantly physic-chemical properties of the soil. The cast earthworms produce on surface of the soil makes it rougher, thus affecting water infiltration. However, little attention has been given to impact of the earthworm cast on soil surface on soil water evaporation processes. In this paper, a simulated evaporation experiment was carried out to explore effects of earthworm cast mulch on soil evaporation. 【Method】The experiment was designed to have two variables, thickness and coverage of the cast mulch, i.e. 1 cm, 2.5 cm and 4 cm for the former and 30%, 60% and 90% for the latter, and a control, i.e. a plot of bare soil. All the treatments, including the control, in the experiment, were monitored for 15 days in a row for daily evaporation and 12-hour or diurnal change in evaporation. Daily evaporations were recorded and accumulation of the 15 days calculated for analysis of differences between the treatments. In addition, samples of the soils and earthworm cast were collected before and after the experiment for analysis of organic matter content.【Result】Results show that the ratio of soil evaporation to atmospheric evaporation was lower in the treatments than in the control and declined with increasing thickness of the mulch (4 cm < 2.5 cm < 1 cm < bare soil). The cumulative evaporations from the soil mulched with 1 cm, 2.5 cm or 4 cm of cast were 10.66%, 14.19% or 33.38% lower than that from the control, respectively. The daily monitoring shows that soil evaporation varied with temperature; the thicker the mulch and the lower the soil evaporation. In the bare soil, evaporation peaked in the first five days of the experiment and then declined down to a level lower than that in all the other treatments in the days to follow, which might be attributed to the rapid loss of soil water in the early days, making the surface soil compacted. And the compacted soil surface hindered soil evaporation. The cumulative evaporation in the soil mulched up to 30% and 60% was 0.17 and 0.07 time respectively, higher than that in the soil mulched up to 90%, indicating that soil evaporation decreases with rising mulching coverage. In terms of daily variation of the evaporation, the treatments exhibited an order of 30% > 60% > 0% (bare soil) > 90% in mulching coverage. The mean cumulative evaporation of the soil mulched up to 90% was 89 percent of that of the bare soil, indicating that the mulch of cast inhibits soil evaporation. The earthworm cast was 3.53 times as high as the soil in organic manure content before the evaporation. Along with the progress of the experiment, organic matter content decreased in both earthworm casts and soils in all treatments. But the soils mulched with earthworm cast were significantly higher than the control in organic matter content after experiment, showing that the higher the thickness and coverage of the mulch, the less the decrement in soil organic matter content.【Conclusion】It can be concluded that mulching earthworm cast on soil surface helps reduce soil water evaporation. For a given mulching coverage, water evaporation decreases with increasing mulching thickness. The effect of mulching coverage on evaporation is not significant due to compaction of the surface soil. Both evaporation and its variation, however, decreases with increasing mulching coverage, indicating that the higher the mulching coverage, the higher the effect on evaporation. Earthworm cast is quite high in organic matter content, and hence higher in soil water retention capacity. That is to say, cast mulching is able not only to increase soil organic matter content, but also to retain soil water. Besides, the mulch can also reduce influences of the external factors, such as climate, thus making soil evaporation and its variation lower.

    • Variation of Hydraulic Parameters of Shallow Flow on Steep Loess Slope

      2018, 55(3):641-649. DOI: 10.11766/trxb201710310307

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      Abstract:【Objective】Hydraulic characteristics of shallow flow are essential to elucidating mechanisms of soil erosion and sediment yield on the slope. However, most of the studies in this aspect have been reported on slopes less than 25° in gradient. This paper is oriented to study hydraulic characteristics of steep loess slopes (25°~50°), in an attempt to lay down a foundation for elucidating in-depth relationships of the hydraulic characteristics of shallow water flow on slopes with slope soil erosion. 【Method】An indoor experiment was carried out simulating rainfalls on steep loess slopes. The experiment was designed to have only one soil type (loessal soil), three rainfall intensity (1.0mm min-1, 1.5 mm min-1 and 2.0 mm min-1) and six slope gradient (25°, 30°, 35°, 40°, 45° and 50°) with the aid of perforated metal flumes (3 m in length, 1 m in width and 0.30 m in depth). Runoff, sediment and flow velocity on the slopes were observed, relative to rainfall intensity and slope gradient. 【Result】Results show: (1) Flow velocity increased with rising rainfall intensity on slopes the same in gradient, and under the same rainfall intensity, the effect of slope gradient on flow velocity exhibited a critical point in gradient, that is, between 40° and 45° under the same rainfall intensity. On slopes with gradient lower than the critical point, flow velocity increased with rising slope gradient, whereas on slopes with gradient higher than the point, flow velocity decreased with rising slope gradient. (2) Mean runoff depth increased steadily with rising rainfall intensity on all slopes regardless of gradient; but decreased with rising slope gradient under rainfalls the same in intensity. (3) Reynolds numbers of steep loess slopes were on the whole relatively small, often far below 580. In this study shallow flows on slopes were of laminar flow in destabilized layers, while shallow flows with Froude number beyond 0.8 were of rush. And (4) Darcy-Weisbach resistance coefficient (f) was positively related to rainfall intensity and negatively to slope gradient. 【Conclusion】Rainfall intensity, slope gradient and interactions between these two factors all have significant effects on hydrodynamic parameters (p<0.01) of shallow flow on steep slopes, but flow velocity, Froude number and Darcy-Weisbach resistance of the shallow flow varied mainly with slope gradient, while runoff depth and Reynolds number did mainly with rainfall intensity.

    • Hydrological Characteristics and Soil Reconstruction of Different Landform Units as Affected by Urbanization Process in Purple Hilly Area

      2018, 55(3):650-663. DOI: 10.11766/trxb201712060504

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      Abstract:【Objective】Urbanization absolutely needs activities like excavating, land-filling and road paving during its process, thus generating a variety of disturbed landform units, among which the dumping of waste soil is the main soil source supplying the construction of urban greenbelts with alien soil. Consequently, the distubered landform units join together with native landform units forming a complex underlying in the area of a urbanization construction project. 【Method】 In this paper, by means of field investigation and laboratory tests, a system comparison was made of the various landform units in material composition, water infiltration and water holding capacity, and then discussions were carried out on three types of reconstructed urban soil and their potential roles in mitigating the risk of urban water logging. 【Result】 Results show: (1) Soil bulk density differed significantly (p <0.05) between the landform units and varied in the order of Construction makeshift road (1.74 g cm-3) > 2-year piles of dumped waste soil (1.58 g cm-3) > 2-month piles of dumped waste soil (1.52 g cm-3) > Waste grassland (1.47 g cm-3)> Cultivated slopeing land (1.34 g cm-3) > Artificial forest land (1.32 g cm-3). In the piles of dumped waste soil, soil bulk density was higher on their flat tops than on their side slopes; (2) Soil infiltration rate varied in the order of side slopes of the piles of dumped waste soil > native landform > flat tops of the piles of dumped waste soil; stable infiltration rate on flat tops of the piles varied too with compactness of its surface layer, thus exposing it to the risk of forming of an aquitard; (3) Water storage capacity differed sharply from lanfform unit to landform unit (p<0.05), and was generally lower in reconstructed landform units (378.7 t hm-2) than native ones (472.6 t hm-2); it varied in the order of: 2-year piles > 2-month piles > Construction makeshift road, for disturbed landform units and in the order of Artificial forest land > Cultivated slopeland > Waste grassland for native landform units; and (4) For urban green land, soil reconstruction was usually done in three types, that is, tree-suitable, shrub-suitable and herb-suitable, and thickness bulk density, gravel content (<2 cm) and organic matter content were the main factors determining soil quality of the reconstructed soils. Soils reconstructed in line with the three types (herb-suitable, shrub-suitable and tree-suitable) may ensure the revegetation successful and capable of playing its potential role in regulating surface runoff and mitigating the risk of urban waterlogging, 2 months after plantation for herbs and 4~5 months for trees and shrubs. 【Conclusion】 All the findings in this study may provide certain scientific support for soil reconstruction for urban green belts and land and management of urban waterlogging during the process of urbanization in the Three-Gorge Reservoir Area.

    • Effect of Ion-strength on Desorption of Copper Ions Adsorbed on Surface of Variable Charge: Kaolinite

      2018, 55(3):664-672. DOI: 10.11766/trxb201711050260

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      Abstract:【Objective】To investigate effect of ionic strength on desorption of Cu(II) pre-adsorbed on the surface of a variable charge, kaolinite was put into in de-ionized water or 0.1 mol L-1 NaNO3 solution to adsorbed copper ions first and then into NaNO3 solution varying in concentration from low to high for sequential desorption. 【Method】In this study, kaolinite was pretreated with electrodialysis and then underwent a series of adsorption and desorption tests with varying pH to explore characteristics of copper ions (Cu(II)) desorption from the clay mineral.【Result】Similar to the findings of previous studies, the fraction of Cu(II) adsorbed by kaolinite increased rapidly from 0.05 to nearly 1 in solutions with pH varying within the set range (pH 3.0~6.3). Regardless of concentrations of the electrolyte used, all the adsorption fraction curves could be fitted with Fischer equation with the degree of fitting being over 0.999. Also noteworthy, when Cu(II) adsorption was carried out separately in de-ionized water and in 0.1 mol L-1 NaNO3 solution, the same in pH, the fraction of Cu(II) adsorbed was always higher in de-ionized water than in 0.1 mol L-1 NaNO3 solution, which was attributed to the effect of the electrolyte of high concentration in the solution inhibiting Cu(II) adsorption. Results of this experiment demonstrate that firstly, the adsorbed copper ions can be desorbed in de-ionized water, and the fraction of desorbed Cu ion declines with the desorption going on round by round in de-ionized waters the same in pH; secondly, in most cases, when the fraction of desorbed Cu ions approaches near zero, the equilibrium solutions are basically the same in pH (about pH 5.0); this phenomenon is underatandable when the fraction of readsorbed Cu ions is taken into account; and the last, after the first round of desorption in de-ionized water, the phenomenon of readsorption will begin to appear only when the pH in the solution gets higher than a certain pH value, which means that copper ions is adsorbed rather than desorbed when the equilibrium solution goes above a certain value in pH. Results of the experiment to desorb Cu(II) that was pre-adsorbed either in de-ionized water or 0.1 mol L-1 NaNO3 solution with de-ionized water for three rounds and then with NaNO3 solutions varying in concentration from low to high demonstrate that firstly, Cu(II) that could not obviously be desorbed by de-ionized water could be desorbed by NaNO3solution, and with rising pH, the pH-desorption fraction exhibited a curve of ascending first and descending, which has nothing to do with concentration of the solution and rounds of the desorption; secondly, the fraction of desorption did not vary much in 0.01 mol L-1NaNO3 or in 0.1 mol L-1 NaNO3, which is fully understandable when the fraction of re-adsorbed in de-ionized water is taken into account; and the last, regardless of the concentration of NaNO3, the rising trend of the fraction of adsorption had a relatively gental start.In most cases the desorption fraction curve had an apparent turning point where the desorption fraction abruptly turned upwards, regardless of concentration of NaNO3 and rounds of the desorption. Although the pH of the desorption equilibrium solution at the turning point of the desorption fraction curve was not consistent, while the pH(pHch) of the adsorption equilibrium solution at the turning points of the adsorption fraction curve was quite consistent, being around pH 3.6, which means that with the system rising in pH, a similar desorption trend was observed around the turning point of the pH-adsorption curve in the desorption tests, i.e. Cu ion desorption begins with rise and then fall regardless of adsorption condition.The findings also demonstrate that pH (pHch) at the turning point of the desorption curve is related to the zero point of zero salt effect (PZSE) of kaolinite.【Conclusion】 All the above described can be attributed to changes in potential of the variable-charge surface caused by ion strength as well as hydrolysis of the edges of the kaolinite induced by increasing pH.

    • Specific Ion Effect of Aggregating Montmorillonite Nanoparticles

      2018, 55(3):673-682. DOI: 10.11766/trxb201709150066

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      Abstract:【Objective】The phenomenon of aggregation of colloid particles varying from ion to ion the same in valence in solutions the same in electrolyte concentration is referred to as specific ion effect or Hofmeister effect. In this study, aggregation of montmorillonite colloid particles were observed under an atomic force microscope (AFM) and their adhesion force measured, in an attempt to analyze specific ion effect of the particles in aggregation and hence to provide experimental support to theoretical studies on interactions between ions and particles, and references for further studies on specific ion effects of aggregating particles in strong electric fields.【Method】The montmorillonite particles that had gone through a 200 mesh sieve were added into LiCl, KCl, NaCl, RbCl and CsCl solutions 10, 30 and 50 mmol L-1 in concentration, separately, and prepared into montmorillonite suspensions, which were then dripped onto mica sheets, separately, air dried, and scanned with AFM. 【Result】 (1) With rising concentration of electrolyte in the system, aggregation of montmorillonite particles occurred horizontally first and then vertically. (2) In solutions varying in electrolyte, but the same in concentration, the montmorillonite particles aggregation degree exhibited obvious specific ion effects. The montmorillonite particles in all the electrolyte solutions 10 mmol L-1 in concentration were all around 1 nm in height; in the Cs+ system, montmorillonite particles were about 300 nm in diameter, and aggregated horizontally, while those in the other ionic systems were merely 100 nm, and did not aggregate horizontally. In the electrolyte solutions 30 mmol L-1 in concentration, Montmorillonite particles in the Rb+ system, they reached 400 nm in diameter and about 4 nm in maximum height, which indicates that the particles aggregated horizontally, and vertically, too, though not much, and in the Cs+ system, Montmorillonite particles did aggregate horizontally and vertically. And in the solutions 50 mmol L-1 in concentration, Montmorillonite particles in the Li +, Na +, K+, Rb +and Cs+ systems were approximate 0.7 、0.8、2、2~14 and 60, respectively, which indicates that Montmorillonite particles exhibited weak superposition in the K+ system, strong aggregation process in the Rb+ system with the particles vertically stacked up to 10 layers, and more significant aggregation in the Cs+ system. (3) In solutions with a given ionic concentration, the maximum adhesion force between Montmorillonite particles and the probe varied in the order of Li+ < Na + < K+ < Rb+ < Cs+, showing significant specific ion effects. The variation was slight when the electrolyte concentration of the solution was low, but great when it was high.【Conclusion】 Through direct AFM observation, it was found that strong specific ion effects existed in the aggregation of montmorillonite particles and varied in the sequence of Li+ < Na+ < K+ < Rb+ < Cs+. The colloid particles aggregated mainly horizontally in solutions low in ionic concentration, and then began to do vertically with increasing ionic concentration. The higher the aggregation degree, the higher the adhesion force.

    • Different Models and Mechanisms of BS-12+DAS Modified Bentonite Adsorbing Phenol and Phenanthrene

      2018, 55(3):683-694. DOI: 10.11766/trxb201711270313

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      Abstract:【Objective】Bentonite is a cheap and efficient adsorbent that reduces the mobility of organic and inorganic pollutants in soil.Once chemically modified, the bentonite can increase its organic pollutantsadsorption capacity. As organic pollutants are different in hydrophobicity, they are adsorbed by different mechanisms, such as distribution, surface, charge attraction,even on the same surface. However, the current researchesare focusing mainly on single surface modification of bentonite adsorbing a single organic pollutant, with little attention to complex amphoteric anionic compound modified bentonite adsorbing organic pollutants different in hydrophobicity on its surface via different mechanisms and its causes.In this paper, Dodecyl dimethyl betaine(BS) modified bentonite was remodified with anionic surfactant Sodium 1-decanesulfonate (DAS). Analysis was done of effects of modification rates on adsorption capacity of the modified bentonite and its apparent thermodynamic parameters of phenol and phenanthrene, and further of differences in adsorption of organic pollutants different in hydrophobicity and its causes.【Method】Sodium bentonite was purchased from the Xinyang Tongchuang Bentonite Company and further purified . BS is an amphoteric surface modifier and DAS an anionic surface modifier. BS modified bentonite and BS+DAS combined modified bentonite were prepared with the wet method. 50BS means that the modification ratio of BSis 50% CEC, whereas 100BS+100DAS means indicates that the modification ratio of both BSand DAS was 100% CEC. Phenol and phenanthrene had 9 levels of concentration forming a gradient. A batch adsorption experiment was done, placing 0.2000g of soil sample into each 50mlcentrifuge tube (plastic or glass), adding 20.00mlof phenol or phenanthrene solution (25% v/v, Dimethyl sulfoxide as solvent), separately into plastic tube or glass tube, covering each tube with a lid andsealing the lid with glue to prevent volatilation of phenol and phenanthrene,putting the tubes on an oscillator with constant temperature for 24 hours of oscillation and then on a centrifugeforcentrifugation, determining equilibrium concentration of phenol or phenanthrene in the supernatant, and in the end calculating adsorption of phenol or phenanthrene in the solution using the subtraction method.【Result】Results show that adsorption of phenol and phenanthrene on BS+DAS bentonite decreased with increasing anionic modification ratio, the effect of the BS+DAS bentonite inhibiting phenol adsorption was more significant; the sorption of phenol on the bentonite were of the mode of “unsaturated” partitioning, while the sorption of phenanthrene of the mode of “saturated” partitioning; and both were physisorption. rising temperatureinhibited the sorption of both, but rising pH promoted the adsorption of phenol while inhibiting the adsorption of phenanthrene; Ionic strength, in the solution varying in the range of 0.001 molL-1~0.1 molL-1 KNO3in concentration, enhanced phenol and phenanthrene adsorption; the analysis of thermodynamic parameter shows that the adsorptions of phenol and phenanthrene on BS+DAS bentonite were spontaneous process, while the adsorptions triggered by improvement of the logarithmic n-octanol/water partition coefficient (log P) by DAS on the surface of BS+DAS bentonite were different in mechanism.【Conclusion】To improve the soil sample’s capacity of adsorbing organic pollutants different in hydrophobicity by modifying the soil sample chemically to increase its organic carbon content, it is essential not only to take into consideration the effect of organic carbon content, but also to take into account variation of the intermiscibilitybetween organic phase of the soil surface and pollutions.

    • Effect of Saw Dust Ash Ameliorating Degraded Vegetable Garden Purple Soil

      2018, 55(3):695-706. DOI: 10.11766/trxb201710210350

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      Abstract:【Objective】The objective of this study is to explore effects of saw dust ash ameliorating acid purple soil relative to dosage of the ash used, in an attempt to work out a scientific basis and reasonable measures to remedy degraded and acidified purple soil and hence to realize sustainable development and circular agriculture. 【Method】In this study, saw dust ash used was residue after combustion at 800~900 °C. A one-year field experiment was designed to have seven treatments different in saw dust ash application rate, i.e. 0, 3 000, 6 000, 9 000, 12 000, 15 000, 18 000 kg hm-2, and carried out in the Baishiyi Vegetable Base of Jiulongpo District, Chongqing, China, to explore effects of application of the saw dust ash on amelioration of acid purple soil, and on soil microbiota, soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN). 【Result】Results show: 1) application of saw dust ash increased yields of the vegetables significantly, showing a trend of the yield increasing with rising application rate; and the treatment applied with 18 000 kg hm-2 of saw dust ash was 76.1%~121.9% higher than CK (0 kg hm-2 applied) in vegetable yield; 2) Application of saw dust ash increased the content of organic matter and pH in the surface and subsurface layers of the degraded purple soil, and the effect was particularly significant in the treatment applied with 18 000 kg hm-2 of the ash. However, overuse of the ash (over 18 000 kg hm-2) had a negative effect on the content of exchangeable H+ and Al3+, while in the treatments applied with 12 000~15 000 kg hm-2 of the ash no such effect was observed, and the content of exchangeable H+and Al3+ was 0.19~0.20 and 0.63~0.67 cmol kg-1, respectively; 3) In the treatments applied with 12 000~15 000 kg hm-2 of the ash, soil alkalytic N and readily available K increased significantly and in the treatment applied with 18 000 kg hm-2 of the ash soil available P was the highest or 55.3 mg kg-1 higher than in CK; And 4) The population of bacteria was the highest in the surface and subsurface layers and followed by that of fungi and actinomyces, and they peaked in the treatment applied with 12 000, 9 000 and 6 000 kg hm-2 of the ash respectively. Compared with CK (A0), the treatments applied with 12 000~15 000 kg hm-2 of the ash was significantly increased or by 70.4%~78.7% in SMBC content, and the treatment applied with 18 000 kg hm-2 of the ash was the highest in SMBN content, reaching up to 40.54 mg kg-1 and followed by the treatment applied with 9 000 kg hm-2 of the ash, which was 34.32 mg kg-1. 【Conclusion】Results show that application of saw dust ash can increase soil available nutrient contents, remedy soil acidification and improve soil microbial communities, SMBC and SMBN. In the study, the application rate of 12 000~15 000 kg hm-2 is the most suitable one that can improve soil fertility and increase soil microorganic population in degraded purple soil.

    • Bibliometric Analysis of Studies on Remediation of Heavy Metals Contaminated Soils Based on Web of Science

      2018, 55(3):707-720. DOI: 10.11766/trxb201708130263

      Abstract (2518) HTML (1367) PDF 5.24 M (2871) Comment (0) Favorites

      Abstract:【Objective】In order to get a deep understanding of progress, highlights and trend of the researches on technologies for remediation of heavy metals contaminated soils in the world, a study was carried out on bibliometric analysis of the researches in these aspects. 【Method】In this study, based on the Web of ScienceTM core collection database bibliometric analysis was performed of the articles, published during the period of 2000—2016, on remediation of heavy metals contaminated soils from the aspects of countries or regions listed as TOP10 in volume of publications of related topics, high-yield authors, source journals, important research institutions and research direction or hot spots, etc. using the analysis tools self-provided by the Web of Science (abbreviated as WOS), Hist Cite citation analysis software, VOS viewer software and Origin 9.1 software. The Hist Cite citation analysis software is a literature citation analysis tool, capable of quickly mapping out development of a research area through data analysis and enabling you to find important literature and academic bull; the VOS viewer software, a software tool for constructing and visualizing bibliometric networks and the Origin 9.1 software, one of the professional cartographic software and data analysis software and a brainchild of the Origin Lab Company. 【Result】 Results show that in this research field, China ranks first in volume of publications, but quite low in frequency of citation per paper; the USA and China are homes to most of the high-yield authors, among whom the top three authors are Dr. Ma L Qin the USA, Dr. Vangronsveld J in Belgium and Dr. Zhou, Q X in China; and the Chinese Academy of Sciences, the Zhejiang University and the University of Florida are the top 3 of the most important contribution institutions; the Environmental Science & Technology, the Journal of Hazardous Materials, the Chemosphere and Environmental Pollution, etc. are the most important publishers of the papers in ths field; technologies of phytoremediation, bioremediation and Stabilization/Immobilization are the hotspots in the researches; soil heavy metal pollutants, such as cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn) and arsenic (As), etc. are the main objects of the researches; and environmental science, ecology, engineering science, agricultural science, water resource science, etc. are the major relevant disciplines of science involved. 【Conclusion】 This study will help beginners in this field to understand directions, trend and hotspots of the researches in this field of remediation of heavy metals contaminated soils.

    • Effect of Straw Return on Diffusion, Translocation and Transformation of Zinc in Calcareous Soil

      2018, 55(3):721-733. DOI: 10.11766/trxb201710090326

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      Abstract:【Objective】 Zinc (Zn) deficiency in humans caused by inadequate dietary intake is a nutritional problem, which affects approximately two billion people all over the world. It is well known that low zinc (Zn) availability in soil is an important reason for low Zn content of cereal grain, consequently resulting in Zn malnutrition in humans who rely mainly on cereals as staple food. Organic carbon in soil, especially its labile fraction, plays a decisive role in Zn translocation and transformation through changing soil chemical properties (i.e. pH and carbonate) and complexing and chelating Zn, of which the latter is one of the most important factors controlling solubility and mobility of Zn in the plant-soil system. Nowadays in China, the major approach to improvement of quantity and quality of soil organic carbon in cereal cropland is to incorporate crop straw, instead of the traditional organic manure and compost. When straw is incorporated, changing soil labile organic fractions, soil Zn responds correspondingly in diffusive translocation and transformation, of which the mechanism is still unclear in calcareous soils. 【Method】 In view of the above-mentioned scientific issue, an incubation experiment was carried out in greenhouse, using the half-cell device to evaluate effect of crop straw return on Zn availability (diethylenetriamine penta–acetic extractable Zn, i.e. DTPA-Zn) Zn diffusion and Zn transformation in calcareous soil. The soil treated with ground maize straw (0, 15 g kg-1 soil) and/or ZnSO4?7H2O (0, 20 mg Zn kg-1 soil) was placed in the 10-mm central compartment of the device, leaving the lateral compartments packed with untreated soil. After 45 days of incubation, the soils in the central cell and lateral compartments were collected with a frozen microtome for analysis of soil DTPA-Zn, total Zn, Zn fractions, soil organic carbon and its fractions (i.e. dissolved organic carbon and its SUVA254, humic substances, and fulvic and humic acids). 【Result】 Straw return alone significantly increased the concentrations of soil organic carbon and fractions of labile organic carbon (i.e. dissolved organic carbon and fluvic acids), but didn’t have much impact on diffusion of DTPA-Zn due to the weak response of soil DTPA-Zn in concentration in both central cell and lateral compartments. Additionally, straw return alone did not change proportions of Zn fractions in total Zn and it is because most Zn in the soil was strongly fixed in the fraction of residue (Res-Zn) that the response of Zn in transformation to the increased labile organic carbon was weakened in the soil. Zn addition alone significantly increased the fraction of Zn loosely bound to organic matter (Lom-Zn) and its distribution in total Zn; and greatly increased concentration of soil DTPA-Zn and its diffusive translocation in the central cell. However, diffusion of DTPA-Zn was only detected within the radius of 15 mm of the fertilized point after 45 days of incubation, which was attributed to immobilization of the added Zn. DTPA-Zn concentration in the central soil applied with straw and Zn was similar to that in the soil treated with Zn addition alone, but diffusion of DTPA-Zn was detected within the radius of 20 mm of the fertilized point after 45 days of incubation. Furthermore, the former was much higher than the latter in both cumulated diffusion and diffusion rate. The return of straw in addition to Zn application increased the fractions of labile organic carbon, such as dissolved organic carbon and fluvic acids, which inhibited transformation of added Zn into immobilized Zn (i.e. Res-Zn), thus increasing of DTPA-Zn concentration and its diffusion. 【Conclusion】 Consequently, in the case of straw return, Zn addition is a promising practice to increase concertation and diffusion of DTPA-Zn simultaneously in the calcareous soil.

    • Effects of Chemical Nitrogen Fertilizer and Green Manure on Diversity and Functions of Soil Bacteria in Wheat Field

      2018, 55(3):734-743. DOI: 10.11766/trxb201710270425

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      Abstract:【Objective】Application of chemical nitrogen fertilizer and green manure is one of the important measures to improve crop yield and soil quality, but it also affects the soil bacterial community and its function, and thereby alters soil nutrient circulation. At present, there are few reports on whether long-term application of fertilizer nitrogen and green manure can improve diversity and functions of the soil microbia in the dryland soils. It is, therefore, of great significance to explore effects of application of chemical nitrogen fertilizer and green manure on the soil bacterial communityand its functions.【Method】An eight-year-oldwinter wheat field experiment, designed to have three treatments: i.e. Treatment CK (control applied, with P2O5105 kg hm-2a-1), Treatment FP (applied with P2O5105 kg hm-2a-1,N150 kg hm-2a-1) and Treatment FGM (applied with P2O5 105 kg hm-2a-1,N 150 kg hm-2a-1, plusgreen manure), laid out in a randomized block design,was carried out in Shaanxi Province, China. Soil samples were collected in september 2016 for analysis of soil biochemical properties (pH, nitrate N, ammonium nitrogen, soil organic carbon (SOC), microbial biomass carbon(MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON)). The high throughput sequencing technique was used to determine 16S rRNA gene sequence in V4 zone of the soil bacteria, and in the end soil microbial community and its functions in the soil were analyzed. 【Result】Results show that Treatment FP was 8.0% higher in SOC than CK, while Treatment FGM was 20.0% higher in SOC, 62.2% higher in MBC, 35.9% higher in MBN, 7.27% higher in DOC and 56.3% higher in DON. The average OTUs number of the three treatmentswas 3792, and no significant difference was observed between the treatments in Chao1 index and Shannon index. In the soil bacterial communityAcidobacteria, Actinobacteria, Bacteroidetes,Gemmatimonadetes and Proteobacteriawere dominant groups, regardless of treatments. However, at the genus level, Treatment FP was significantly lower than CK in abundances of Pseudoduganella,Steroidobacter,Adhaeribacter,Nordella and Ralstonia, while Treatment FGM was lower only in abundance of Lactobacillus but higher in abundance ofSteroidobacter,Chryseolinea,Lentzea and Chitinophaga.Bacterial function prediction using FAPROTAX centered mainly on chemoheterotrophy, nitrification, ammonia oxidation, nitrite oxidation, and nitrate reduction, while the prediction using Tax4Fundid mainly on carbohydrate metabolism, amino acid metabolism, membrane transport, signal transduction and energy metabolism.The three treatments did not vary much in functional fractionation. 【Conclusion】All the findings in this experiment suggest that Treatment FP and Treatment FGM do not havemuch effects on bacterial richness, diversity and functions, whilethey do increase soil fertility, i.e. SOC, DOC and DON, by a certain degree.

    • Response of Paddy Soil Anammox Bacteria to Long-Term Fertilization in Community Structure

      2018, 55(3):744-753. DOI: 10.11766/trxb201711060470

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      Abstract:【Objective】 This study was conducted to investigate abundance and community structure of anaerobic ammonia oxidizing (anammox) bacteria in paddy soils under long-term fertilization and explore mechanism of anammox bacteria responding to different fertilizers, in an attempt to provide a scientific basis for rationalizing fertilization and understanding ammonia oxidizing processes in wetland ecosystems. 【Method】 Four treatments, i.e. control (CK), chemical fertilizer (NPK), chemical fertilizer plus cattle manure (NPKM), and chemical fertilizer plus straw (NPKS), were set in the field experiment of the study. Soil samples were collected from the treatments for analysis of abundance and community structure of soil anammox bacteria, using the fluorescent quantitative PCR assay targeting hydrazine synthase α-subunit (hzsA) gene and high-throughput sequencing technology aiming at 16S rRNA gene of anammox bacteria. 【Result】Significant differences were observed between the treatments in abundance of hzsA gene (p<0.05), exhibiting an order of NPKM>NPKS>NPK>CK. Correlation analysis (p<0.05) shows that abundance of hzsA gene was significantly and positively related to soil organic matter, total nitrogen and ammonia content. High-throughput sequencing shows Candidatus Brocadia, Candidatus Anammoxoglobus and Candidatus Scalindua were the main anammox bacteria and Candidatus Brocadia the dominant one in all the treatments. Bacteria diversity analysis shows that treatments CK and NPKS were significantly higher than treatment NPKM and NPK in Shannon index, Simpson index and Chao 1 index (p<0.05). 【Conclusion】 Long-term fertilization alters the anammox bacteria community in population and structure. The application of chemical fertilizers combined with organic manure is conducive to abundance of the anammox bacteria. However, the anammox bacteria community in the soil varies in structure with difference in fertilization. The anammox bacteria community increased in α-diversity in the soil applied with chemical fertilizer plus straw, but decreased in the soil applied with chemical fertilizer only and chemical fertilizer plus cattle manure. It can, therefore, be concluded that anammox bacteria vary in their response to different fertilizer or manure used in abundance and community structure.

    • Effects of Warming at Different Growth Stages on Rice Yield and Nitrogen and Phosphorus Contents

      2018, 55(3):754-763. DOI: 10.11766/trxb201711240476

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      Abstract:【Objective】Human activities have caused global warming. So it is essential to get to know how warming affects rice yield and contents of nitrogen (N) and phosphorus (P) in the soil, which may provide a certain basis for prediction of yield and quality of rice grains in future climate conditions.【Method】In the present study, rice cultivars of Tairuifeng 5 and Zhendao 16 were planted in pots, which were placed into a growth chamber with controlled temperature, 5℃ higher than the air temperature outside for 7 days, at their tillering stage, booting stage, heading stage, flowering stage and filling stage, separately. Then effects of warming at different growth stages on rice yield and content of N and P in the plant were analysed. 【Result】Results show that warming at different growth stages affected significantly yield compositions of rice, with the warming at the booting stage and heading stage was the highest in the effect. The plants of Tairuifeng 5 and Zhendao 16 treated with warming at the booting stage were the lowest in number of grains per ear, seed setting rate and thousand grain weight. On the whole, warming at different growth stages increased significantly nitrogen content in stem, leaf, husk and grain of Tairuifeng 5 and Zhendao 16 (p<0.05). The effect of warming on P content depended on duration of the warming and rice cultivar. Compared with the control, Tairuifeng 5 treated with warming at the tillering stage, heading stage, flowering stage or filling stage was significantly lower in nitrogen harvest index, while Zhaodao 16 treated with warming at the heading stage was. Compared with the control, Tairuifeng 5 treated with warming at the heading stage and filling stage significantly was significantly lower in phosphorus harvest index, while Zhendao 16 treated with warming at the tillering stage and heading stage was. 【Conclusion】All the findings in the present study show that the booting stage and heading stage are the critical periods when warming affects rice yield and uptake of nitrogen and phosphorus.

    • Mechanism of Plasticity of Root Vessel Structure of Ziziphus jujuba var. spinosa Adapting Ecotopes along a Natural Drought Gradient

      2018, 55(3):764-773. DOI: 10.11766/trxb201710130457

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      Abstract:【Objective】Root system of a plant plays a vital role in drought tolerance. Water and nutrients are absorbed by roots, which have to adapt themselves in structure and function to adverse environments for survival,and the structure determines their function and efficiency of water/nutrient translocation. However, little information is available about plasticity of the vessel in structure in the root system of the plant growing in different ecotopes. So, study on plasticity of the vessel is the key to understanding plant adaption to ecotopes along a gradient of drought.【Method】Therefore, this study was done to explore plasticity of rootvessels in structure of Ziziphus jujuba var. spinosa growing in different ecotopes, such as Yantai, Shijiazhuang, Yinchuan and Turpan along a natural drought gradient. Roots were sampled from the four ecotopes for analysis of characteristics of the vessels in the secondary xylem of the roots using segregation process and microscopy.【Result】The root vessels could be classified into six types and varied sharply in number and structure with the ecotope. The vessels could be sorted into three types according to their tail structure: no tail, tail on one end and tails on both ends, which demonstrate specific adaptive properties and regularity. From Yantai to Turpan with the drought aggravating, the reticulate vessel increased in thickness of the wall, but decreased in length of tails; the pitted vessel decreased in length, width and diameter, but did reversely in thickness of the wall and length of the tails; the spiral vessel decreased in length, thickness of the wall and length of the tails; the scalariform vessel decreased in length, width and diameter and evolved from tailless to multi-tailed; and the xylon declined gradually in length, width and thickness of the wall, but did reversely in length of the tails. In addition, compared with the tree in Yantai, the trees in Shijiazhuang, Yinchuan and Turpan had the pitted vessel decreased by 17.63%, 11.23% and 7.67% in length, the spiral vessel decreased by 20.2%, 11.4% and14.6% in thickness of the wall, the scalariform vessel decreased by 29.1%, 37.6%, 31.4% and 20.7%, 48.5%, 28.6% in length and width, and the xylon decreased by 0.7%, 1.5% and 2.6% in length, by 2.2%, 4.7% and 5.4% in width and by 33.2%, 29.3% and 22.1% in thickness of the wall, respectively. 【Conclusion】All the findings indicate that the root vessels of Ziziphus jujubavar. spinosa are high in plasticity and vary in structure with the ecotope to adapt to local conditions for better adsorption and transport of water nutrients. All the changes in vessel structure improve tenacity and extendability of the roots, enabling the root to go deeper into the soil to adsorb more water from deep soil layers to make up the loss through transpiration in dry environments, thus improving the plants' resistance to drought and adaption to harsh environments to ensure normal growth.

    • >Research Notes
    • Effect of Amendment of Organic Materials on Soil Biological Property in Primary Saline Alkali Soil

      2018, 55(3):774-782. DOI: 10.11766/trxb201710220479

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      Abstract:This paper is to explore effects of amendment of organic materials on soil microbial community and rice yield in newly reclaimed paddy field of primary saline-alkali soil. To that end, a 2-year field experiment, designed to have four treatments, i.e. Treatment KL (granulated straw), Treatment JG (normal straw), Treatment MC (forage) and Treatment YF (sheep manure), was carried out to explore effects of the application of the organic materials on microbial biomass, microbial biomass carbon and nitrogen, soil respiration intensity, activities of three types of soil enzymes and rice yield, and relationships of rice yield with various microbial indices. Treatment JG, MC and YF increased, to a varying extent, microbial biomass, microbial biomass carbon, microbial biomass nitrogen, activities of three types of soil enzymes in the soil, soil respiration intensity and rice yield as compared with the control group, but the differences between the treatments were not significant. However, the treatments applied with the same organic materials but in different form differed significantly in the effect. Treatment KL was higher than Treatment JG in the effect. Compared with CK), Treatment KL increased the population of soil bacteria by 39.45%, the population of soil actinomyces by 50.28% and the population of soil fungi by 89.91%, soil microbial biomass carbon by 63.21%, soil microbial biomass nitrogen by 46.02%, soil respiration intensity by 46.22%, catalase activity by 18.03%, invertase activity by 23.22%, cellulase activity by 79.32%, and rice yield by 130.58%. Populations of soil microbes (bacteria, fungi and actinomycetes) were closely related to 1 000-grain weight, seed setting rate, number of grains per ear and rice yield, soil microbial activity (soil respiration intensity, soil microbial biomass carbon and nitrogen) to 1000-grain weight, number of effective spikes, number of grains per spike and rice yield. Among the three types of soil enzymesactivity (catalase, cellulase and invertase) were closely related to ear length and 1 000-grain weight.Under the same conditions, in the initial stage of soil amelioration of farmlands of primary saline-alkali soil, the application of organic materials had similar effects regardless of type of the organic material, but significantly different effects when the organic materials were of the same type, but different form.

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