• Volume 56,Issue 5,2019 Table of Contents
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    • >Insights and Perspectives
    • Building and Materializing of China Soil Microbiome Data Platform

      2019, 56(5):1023-1033. DOI: 10.11766/trxb201812240642

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      Abstract:【Objective】 Soil is one of the most diversified habitats on earth. It contains not only some large organisms, such as nematodes, ants or moles, but also a huge number of microbes, such as bacteria and fungi. Traditional methods for studying soil microbial diversity, such as laboratory culture, can be used only to isolate and identify a limited number of soil microbial species. In recent years, the rapid development of new technologies, such as high-throughput sequencing, has provided technical guarantees for large scale, rapid, accurate and comprehensive understanding of soil microbial diversity, and promoted the development of specialized and reference databases in the field of microbiology. A series of soil microbiome platforms for soil microbial data management and analysis have been established throughout the world, such as Greengenes, Unite, Silva, RDP, Ez-Taxon, eggNOG, KEGG, etc., which are commonly used in soil microbiology. However, most of these exiting platforms focus on providing basic services, such as data deposition, management, access, annotation, etc., with little attention to systematic collection and standardized integration of data of the environment, in which soil microorganisms live. So it is still difficult to provide effective models and tools for further exploration of soil microbiology data, such as impacts of environmental factors on soil microbial communities, spatial distribution pattern of soil microbial communities, etc. Beginning in 2014, the Chinese Academy of Sciences implemented the Strategic Priority Research Program(Category B)“China Soil Microbiome Initiative”, of which one of the research objectives is to build a professional data integration and analysis platform for soil microbiome research in China. 【Method】 Based on the integration of soil microbial data and soil environmental factor data at different scales, and with the help of spatial database technology and WebGIS, the China Soil Microbiome Data Platform was designed and constructed to synthesize the services of data integration of soil properties and microbial composition, data visualization, knowledge discovery and regional spatial mapping. 【Result】 In respect of architecture design, the platform adopts B/S-based extensible architecture design, which consists of five layers: infrastructure layer, data resource layer, application support layer, management business layer and user service layer, so as to facilitate the integration of massive data resources yielded by specialized researches, while taking into account sustainable development of the platform in future. In materializing the database, PostgreSQL database is used to replace the traditional "relational database + ArcSDE" model, for it has the advantages of strong scalability, perfect function, good compatibility, high access efficiency, and is more suitable for management of soil microbiome data. In terms of function construction, four functional modules, i.e. data management, data visualization, data analysis and user management, are designed and implemented, which provides the platform with supportive guarantees for continuous data services, and maintenance and updating of data resources. The core functions of the platform, such as data integration, visualization analysis and spatial mapping, are exhibited through demonstration data.【Conclusion】 At present, the platform is open for trial operation. Users can register and log in through a concise page to use the platform data resources and professional model tools. With the data resources continuously enriching and the functions steadily improving, the platform will help further promote standardization and integration of China’s soil microbiome data and support full data mining and application of the integrated data.

    • >Reviews and Comments
    • Advancement in Research on Stability of Biochar in the Environment

      2019, 56(5):1034-1047. DOI: 10.11766/trxb201808220426

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      Abstract:Biochar is a kind of carbon material derived from biomass through pyrolysis under anaerobic or anoxic conditions. Because of its merits of storing carbon, fixing soil pollutants and recycling wastes, it is more and more extensively used in agriculture and environment. Its stability in the environment determines stability of its environmental effects and hence an important index in evaluating environmental functions and significance of biochar. In this paper, emphasis was mainly laid on elaboration of potential physical, chemical and biological decomposition processes biochar might undergo in the environment and their influencing factors, and analysis of relationships between properties of the biochar per se and stability of the biochar in the environment. The paper pointed out that physical fragmentation, physical migration, chemical dissolution, chemical oxidation, biological degradation, and properties of the biochar per se were the main factors that jointly affected stability of the biochar in the environment. In the end, the paper brought forth some topics that are worth noticing for future research in this field, that is, (1) release and transport behaviors of biochar micro-particles under the action of water flow and their affecting factors; (2) relationship between redox activity and chemical oxidation of biochar in the environment; and (3) physical, chemical and microbial decompositions of biochar in plant rhizosphere. A systematic and in-depth study on roles of biochar in the environment is contributive to improvement of the knowledge about processes of biochar loss and full understanding of stability of biochar in the environment.

    • Advancement in Researches on Effect of Atmospheric Deposition on Heavy Metals Accumulation in Soils and Crops

      2019, 56(5):1048-1059. DOI: 10.11766/trxb201812130538

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      Abstract:Focusing on the farmland soil-crop-atmosphere system in China, a review is presented in this paper of sources and spatial-temporal distribution of heavy metals, impacts of heavy metals atmospheric deposition on heavy metals accumulation in soils and crops and advancement in the researches in this aspect in recent years. Once entering the atmosphere, heavy metals would start to go back to the land in the form of atmospheric deposition, in which the heavy metals display a clear feature of spatio-temporal variation as affected comprehensively by a variety of natural and anthropogenic factors and environmental protection policies. In terms of temporal variation, heavy metals concentrations in the atmosphere are higher in winter than in the other seasons, and in the heating period than in the non-heating period, while in terms of spatial variation, they are higher in well-developed industrial areas than in the other areas, in cities based mainly on coal as fuel than in the other cities and in urban areas than in suburbs. Atmospheric deposition not only increases the contents of heavy metals in the soil, but also have certain direct and indirect impacts on crops. Heavy metals in the atmosphere enter the plant cells through stomata and accumulate in cell walls and vacuoles. Once accumulating to a certain level, the heavy metals would affect normal growth of the crop and/or bring about the risk of heavy metals overproof in crops, which is a hazard to agricultural safety production. In future studies, it is advisable to integrate traditional analytic methords with modern technologies, like spatial and geostatistical analysis, multiple isotope tracing, mathematical modeling and so on, in exploring heavy metals recylcing processes in the soil-crop-atmospheric system on a reginal scale under natural field conditions so as to provide a scientific basis for regional prevention and control of heavy metal pollution of farmland soils, for environment mnagement and for decision-making in these fields.

    • >Research Articles
    • Identification of Sources of Soils Based on Vis–NIR Spectroscopy and Chemical Attributes

      2019, 56(5):1060-1071. DOI: 10.11766/trxb201809100397

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      Abstract:【Objective】As an important kind of forensic evidence with valuable information, soil plays a key role in case detection and court trials. For an unknown soil sample, how to determine its source is an issue worth studying. 【Method】 In this paper, a stochastical forest model was adopted to identify sources of soil samples based on vis–NIR spectra and soil chemical properties of the soils in Heilongjiang Anhui and Jiangsu, on a trans-provincial and a provincial scale; comparison performed of the usages of different soil datasets and combination schemes in effect of the identification; analysis conducted of relative importances of soil chemical attributes and spectral data; and evaluation made of determination accuracy based on ratio of the number of the samples correctly determined to the total number of samples.【Result】 Results show that the model combining spectral principal component (PC) and chemical data is the best one in determining sources of soil samples on the cross-provincial scale, with accuracy being 0.92. As spectral measurement does not require many soil samples, in the case the amount of soil samples is limited and soil chemical data is hard to obtain, the spectral-PC-and-absorption-peak-combining model is the highest in accuracy, reaching 0.82. On the provincial scale, the combination of spectral PC and soil chemical property data is still the best one with accuracy being 0.83. When soil chemical property data are hard to obtain, the spectral-PC-and-absorption-peak-combining model can achieve considerable accuracy (0.82), which indicates that spectra can be used to replace soil chemical property data in modeling for determination of sources of soils on the provincial scale. To evaluate importance of discriminant factors on the two scales, it is found that the contents of total potassium (TK) and total phosphorus (TP), the first PC of spectra and spectral absorption peaks at 350~600 nm and 1 800~ 2 100 nm band are the most important indices in the model for determination on the trans-provincial scale. While the content of TP and the seventh PC of spectra and spectral absorption peaks at 350~600 nm and 1 800~ 2 100 nm band were in the model for determination on the province scale.【Conclusion】All the findings indicate that source of a soil sample can be accurately identified based on vis–NIR spectroscopy and soil chemical property data. When spatial distribution of sampling sites varies in range in the model, it is advisable to consider the use of different determination factors in modeling and multiple indices in evaluating accuracy of the determination.

    • Characteristics of Nutrient Loss from Sloping Farmland in Karst Region as A Function of Rainfall Intensity

      2019, 56(5):1072-1084. DOI: 10.11766/trxb201808270236

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      Abstract:【Objective】As the multi-media environment in the karst region is so peculiar, few case-specific research methods are available, making it hard to carry out researches in this region of how soil nutrients are lost from slope farmlands. Although some have been done, outcomes vary sharply and are far from complete, adequate or systematic to exposit rules of nutrient loss from slope farmlands in the karst region, let alone mechanisms of underground soil nutrient lost. Therefore, this study was unfolded to explore characteristics and mechanisms of soil nutrient loss from slope farmlands in the karst region as a function of rainfall intensity, in an attempt to provide certain theoretical reference for control of nutrient loss and non-point source pollution from slope farmlands in the karst region. 【Method】An in-lab experiment was carried out with soil packed in a steel trough to s imulate bare slope farmland in morphological structure, 20% in bedrock outcropping rate, 20° in slope gradient, and 3% in porosity. Besides, the experiment was designed to have five levels of rainfall intensity, i.e. 15 mm∙h-1, 30 mm∙h-1, 50 mm∙h-1, 70 mm∙h-1and 90 mm∙h-1, to scour the aritificial slope farmland. Before the experiment began, the soil was made saturated in moisture with a light rainfall event, and effluent was collected for 30 minutes after the slope began to yield runoff. 【Result】(1) The rainfall intensity critical for runoff and sediment yield to transit from underground to surface varied in the range of 30 mm∙h-1~50 mm∙h-1 and runoff and sediment yield increased with rising rainfall intensity, and occurred mainly on the surface. (2) Under light rainfalls, 15 mm∙h-1 or 30 mm∙h-1 in intensity, loss of TN, TP and TK occurred mainly with underground runoff, while under heavy rainfalls, ≥ 50 mm∙h-1 in intensity, the loss of nutrients with surface runoff gained in proportion to the total loss and reached three times as much as that with underground runoff. The runoff loss of TP increased in both volume and concentration with rising rainfall intensity, but the loss of TK and TN did not change so significantly. (3) The nutrient loss with sediment occurred mainly on the surface, reaching about 5.03 times higher than that underground, and nutrients in the sediment were higher in concentration than those in the runoff. Nutrient enrichment rate of the surface sediment was on the whole higher than that of underground leaching. The totals of nutrient losses with surface and underground sediments and their moduli all increased with rising rainfall intensity. And (4) Significantly positive relationships were found of the total volume of runoff with nutrients (TP & TK) in runoff and nutrients (TN, TP & TK) in sediment (P< 0. 05), and with TN in runoff, too (P < 0. 01). 【Conclusion】The losses of TN, TP and TK occur mainly with runoff in slope farmlands in the karst region, and partly with sediment. Under rainfalls light in intensity (15 mm∙h-1 ~ 30 mm∙h-1), attention should be paid mainly to control of nutrient loss with underground runoff. The impact of rainfall intensity is significant on TP loss with runoff in volume and concentration, as well as on totals of nutrients lost with surface and underground sediments and their nutrient loss moduli. The total volume of runoff is significantly related to the losses of nutrients with runoff and sediment.

    • Relationship of Dry-Wet Climate Changes in Northern China in the Past 57 Years with Pacific Decadal Oscillation (PDO)

      2019, 56(5):1085-1097. DOI: 10.11766/trxb201808260225

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      Abstract:【Objective】Global warming has caused heterogeneous changes in precipitation intensity and distribution, which inevitably impacts dry and wet status of the climate. In order to explore changes in distribution of dry and wet climate zones occurring in recent 57 years(1960—2016) in the northern part of the China , this paper characterize the spatiotemporal variation of dry-wet climate in the northern part of China over the period, analyzed the variation for impacts of the Pacific Decadal Oscillation (PDO), and explored potential causes of the variation.【Method】The meteorological data used in this study were downloaded from the “China Surface Climate Daily Data” and “China Surface Climate Data & Daily Data V3.0” of the National Meteorological Information Center, including daily mean temperature, mean minimum temperature, mean maximum temperature, precipitation, relative humidity, mean wind velocity at 10 m height and sunshine hours. Based on the daily climate data of the 424 meteorological stations in northern part of China from 1960 to 2016, ET0 was calculated with the Penman-Monteith method, humid indices(HI) were analyzed for spatio-temporal variation of the wet-dry climate, impacts of the Pacific Decadal Oscillation (PDO) on variation of the wet-dry climate were explored with the correlation analysis method, and spatio-temporal variation of the dry and wet climate was characterized with the linear trend analysis method and the multiple linear regression spatial interpolation method.【Result】Results showed: the overall wet-dry status of the northern part of China fluctuated up and down the mean of the 57 years and did not follow any obvious linear variation trend. Spatially, it displayed as wetting in Northwest China, Qinghai-Tibetan Plateau, Inner Mongolia and Xinjiang, and drying in North China. The extremely arid region was shrinking in area, while the semi-arid, and arid regions expanding, which indicates that the climate-sensitive regions are overspreading. Apparent wetting trends were observed in the extremely arid, arid and semi-arid regions. All the findings show that the boundary between the wet and dry regions was shifting during the period of 1991—2016 to the period of 1960—1990. The northern part of the country experienced a wetting process and the northwestern and western parts of the country and the Qinghai-Tibetan Plateau did a significant one, too. The west boundaries of the extremely arid and arid regions shifted towards the east, and their south and north boundaries retreated inwardly. The trend of aridification was found in North China and parts of the Northeast China. The central section of the boundary of the semi-arid and semi-humid regions along the Yellow River in North China moved southeastward. The climate in the central part of Northeast China and western part of Northwest China was turning humid because of increasing precipitation and decreasing ET0. On the contrast, the climate in the central and western parts of North China, and eastern and northeastern parts of Inner Mongolia was turning arid because of decreasing precipitation and increasing ET0. In the eastern part of Northwest China, western part of Northwest China and eastern part of Inner Mongolia, PDO index was positively related to dry and wet climate, that is to say, when PDO is in its positive phase, precipitation in those regions would be higher and the surface climate relatively wet. When PDO is in its negative phase, precipitation in the above regions would be lower and the surface climate relatively dry. The case in North China was just opposite. Variation of the wet-dry climate was negatively related to PDO, namely when PDO is in its positive phase precipitation in North China tends to be lower and the surface climate relatively dry. When PDO is in its negative phase, precipitation in North China would be higher and the surface climate relatively wet.【Conclusion】All the findings in this paper suggest that the climate in northern part of the country was on the process of getting wet in two time period (period 1: 1960—1990; period 2: 1991—2016) and PDO is closely related to the dry-wet climate.

    • Migration and Release of Dimethyl Phthalate in Purple Soil under Dry-Wet Alternation

      2019, 56(5):1098-1107. DOI: 10.11766/trxb201808100412

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      Abstract:【Objective】This paper is to characterize dimethyl phthalate (DMP) migration and release between overlying water, pore water and soil in the water level fluctuating zone of the Three-Gorges Reservoir during the wetting-drying alternation period.【Method】For the study a flooding experimental device was designed to carry out cyclical wet-dry alternation test using the "flooding-drying" model. 【Result】DMP content was found decreasing significantly in the soil during the first days (0~2 d) of the two flooding periods, but increasing from the third day on, and fluctuating slightly in the pore water and overlying water;it displayed a rising trend to a varying extent in the soil on the first days (0~1 d) of the two drying periods, and a declining one varying in degree on the following two days (2~4 d), and then leveled off during the late period (8~20 d). Soils with initial DMP content varying in the range of 10 ~ 100 mg•kg-1, when flooded, showed a similar trend in DMP migration and release between the three phases. However, DMP content in the overlying water showed a different trend from the other three groups, and the DMP distribution fluctuated greatly in the three phases,when soil initial DMP content was 200 mg•kg-1.【Conclusion】The quasi-second-order kinetic equation can be used to well describe migration of DMP in pore water and overlying water into the soil. Correlation analysis shows a significant positive correlation (P<0.05) exists between pore water and overlying water in DMP concentration, but a mildly negative one between soil and pore water.

    • Effects of Long-term Straw Returning on Stability of Mineral-complexed Organic Matter in Shajiang Black Soil

      2019, 56(5):1108-1117. DOI: 10.11766/trxb201812130546

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      Abstract:【Objective】Organo-mineral complex is a kind of substance with soil organic colloidscomplexed with mineral colloids through surface molecular condensation, cation bridging and hydrogen bonding, which plays crucial role instabilization and accumulation of soil organic matter (SOM). Organo-mineral complexes are formed through interactions between organic matter (OM), mineral cations, metal oxides and soil clay minerals. Based on a long-term (10a) stationary experiment of straw returning to the field, this paper explores mechanism of straw returning affecting stability and accumulation of OM within organo-mineral complexes in typical Shajiang black soil, and systematically analyze distribution characteristics of OM content and mechanisms of OM complexing with metal cations and oxides typical in the soil, in an attempt to find out the key mechanism that constrains organic matter accumulation in Shajiang black soil.【Method】The long-term field experiment, which has been carried on since 2007, is designed to have five treatments, i.e. WMS+F (application of mineral NPK plusreturning of both wheat and maize straws), WS+F (application of mineral NPK plus returning of wheat straw only), MS+F (application of mineral NPK plus returning of maize stalks only), F (application of mineral NPK only) and CK (no-fertilization). 【Result】Results show that OM within the organo-mineral complexes existed mainly in the form of Fe/Al-bound organic matter (Fe/Al-OM) and tightly combined organic matter (TCOM), and both of them added up to 88.70% of the total organic matter (TOM). In terms of contents of the three forms of organic matters (Fe/Al-OM, TCOM and TOM), the five treatments followed an order of WS+F≈ WMS+F≈ MS+F>F>CK. Fe/Al-OM, TCOM and TOM was significantly and positively related to soil short-range ordered and organo-bound Fe/Al oxides, and negatively to amorphous Fe/Al oxides in content. 【Conclusion】Straw returning remarkably promotes the accumulation of SOM, which is affected by Fe/Al-OM. The slow formation of amorphous Fe/Al oxides brings about deficiency in content, thus restricting further accumulation of SOM. Although accumulation of Ca and Mg is one of the typical properties in Shajiang black soil, it has little impact on formation of OM in soil organo-mineral complexes because they are easily leached out. What’s more, the contribution of TCOM to TOM is significantly higher than that of Fe/Al-OM, of which relevant mechanism deserves further study.

    • Mineralization of Soil Organic Carbon and its Sensitivity to Temperature in Soil Aggregates, Relative to Particle Size in Red Paddy Soil

      2019, 56(5):1118-1127. DOI: 10.11766/trxb201805300285

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      Abstract:【Objective】 Soil organic carbon (C) is distributed heterogeneously in soil aggregates of all size particles. Organic C mineralization is an important biochemical process in the soil ecosystem and is greatly affected by environmental factors, such as temperature. The objective of this study is to illuminate relationship of organic C mineralization in aggregates with that in bulk soil, to evaluate sensitivity of organic C mineralization in soil aggregates to temperature relative to particle size and eventually to help understand mechanisms of the organic C mineralization in soil aggregates and its sensitivity to temperature. 【Method】The soil used in this study was collected from a paddy filed of red soil fertilized with inorganic and organic manure for 20 years in Yujiang Country, Jiangxi Province, China. Five fractions of aggregates, i.e., >2 mm, 1~2 mm, 0.25~1 mm, 0.053~0.25 mm and <0.053 mm, were isolated with the wet-sieving technique. All the aggregates and bulk soil samples were moistened or dried till they reached 60% in water holding capacity and incubated at 15 °C, 25 °C and 35 °C, separately, for 35 d. Emissions of carbon dioxide (CO2) were monitored and measured during this period. 【Result】Macroaggregates of >0.25 mm contained more organic C and total nitrogen (N) than microaggregates of <0.25 mm. C/N ratio in soil aggregates decreased with declining particle size. Mineralization rates of organic C in both bulk soil and soil aggregates decreased rapidly during the first 7 days of incubation, then gradually leveled off till a stable state in the end. In the soils incubated at 25 °C and 35 °C, the fraction of soil aggregates >1 mm was the highest while the fraction of soil aggregates 0.053~0.25 mm was the lowest in cumulative organic C mineralization. What’s more, cumulative organic C mineralization in soil aggregates was significantly or ultra-significantly and positively related to the content of organic C and total N. The fractions, >2 mm and 0.25~1 mm, contributed the most to cumulative bulk soil organic C mineralization, reaching up to 34.6% and 28.8%, respectively, in contribution rate. With rising temperature, mineralization rate, cumulative mineralization and cumulative mineralization rate of organic C in bulk soil and aggregates all increased. Sensitivity of organic C mineralization (Q10) in soil aggregates to temperature varied in the range of 1.38~2.00, and was ultra-significantly and positively related to organic C and total N contents as well as C/N ratio. 【Conclusion】Macroaggregates of >0.25 mm play a key role in organic C mineralization in bulk soil. Temperature rise promotes organic C mineralization in soil aggregates. Sensitivity of organic C mineralization to temperature in soil aggregates is closely related to quantity and quality of organic matter in the aggregates.

    • Influence of Long-term Fertilization on Fenton-like Reactions and Soil Carbon Storage in Subtropical Red Soil

      2019, 56(5):1128-1139. DOI: 10.11766/trxb201812120497

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      Abstract:【Objective】 Based on a long-term (26 years) fertilization field experiment in Qiyang, Hunan, China, investigations were made of influeces of long-term fertilization on Fenton-like reaction and soil C storage in red soil, with the aid of the techniques of high-performance liquid chromatography (HPLC), high flux sequencing, Synchrotron radiation Infrared microscopic imaging, X-ray photoelectron spectroscopy and in-situ microcosm incubation in soil pores varying in size (1 000 μm, 20 μm and 0.45 μm). 【Method】HO ? was trapped by terephthalic acid (TPA) (non-fluorescent), of which fluorescent product, i.e., 2-hydroxylterephthalic acid (HTPA), was determined with a high-performance liquid chromatographer (HPLC); Soil H2O2 quantified by a modified Fe2+-xylenol orange assay; Structure of bacterial communities and diversity analyzed with 16S ribosomal deoxyribonucleic acid (rDNA) gene sequencing, and interfacial processes identified with synchrotron radiation infrared microscopic imaging and X-ray photoelectron spectroscopy (XPS). In the microcosm incubation experiment, Polyvinylchlorid (PVC) cylinders were used and covered with a replaceable 0.45, 20, or 1 000 μm mesh fabric panel separately that allowed nothing but microorganisms and/ or roots to grow into the test cylinders. 【Results】Concentrations of H2O2, HO ? and Fe(II) were higher in Treatment M than in Treatment NPK, indicating that root excreta and microbes involved in regulating the concentrations. Meanwhile, a linear relationship between H2O2 and HO ? was found. H2O2 buffering capability was higher in Treatment M than in Treatment NPK, suggesting that the soil under long-term application of NPK degraded due to depletion of soil organic matter. Besides, the richness and diversity of soil microbes were significantly higher in Treatment M than in Treatment NPK. Furthermore, the effects of plant roots and microorganisms on soil bacterial community structure were lower in Treatment M than in Treatment NPK. In Treatment M soil bacterial communities affected the release of soil pH, DOC, soluble Fe and CO2, while in Treatment NPK they induced Fenton reactions through production of H2O2 and reduced Fe(II). On root-soil interface, distribution of clay minerals (3 619 cm-1), aliphatic C (2 914 cm-1), carboxylic C (1 725 cm-1) and hydroxyl C (1 135 cm-1) varied sharply in pattern, and the presence of roots increased the proportion of Fe(II) on the interface. 【Conclusion】These findings suggest that long-term manure inputs to soil initializes free-radical reaction by activating microbial communities and mobilizing iron, which is conducive to soil C stabilization and storage by increasing recalcitrance and interactions of SOC. In addition, microbe-mediated Fenton-like reaction may affect C storage and soil fertility.

    • Effects of Topography and Land Use on Soil Organic Carbon in Hilly Region of Loess Plateau

      2019, 56(5):1140-1150. DOI: 10.11766/trxb201901220367

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      Abstract:【Objective】As an important component of agricultural soil a major element for plant growth, soil organic carbon (SOC) plays an important role in the earth ecosystem. Huge amounts of organic carbon are stored in the soil, and even a minor change in soil carbon could significantly change the concentration of CO2 in the atmosphere, which drives global climate change. How SOC is distributed and stored is a very important factor affecting soil quality and SOC fixation.【Method】In this study, soil samples were collected from 5 soil layers in each of the 0~100cm soil profiles distributed in a 150m rectangular grid pattern in fields different in slope position (slope top, upper slope, middle slope, and down slope) and in land use (cultivated land, forest land, grassland, shrubland, terrace) in the Wangmaogou watershed of the Loess Plateau. A total of 1080 soil samples were gathered for analysis of how topographies and land use patterns infuence on content and distribution of SOC via Kriging interpolation.【Result】 Among the slope positions, the upper slopes were the highest, (4.49g•kg-1) and followed by the middle slopes (4.30g•kg-1), the down slopes (3.97 g•kg-1)and slope tops (3.34 g•kg-1) in average SOC content of the 0~100cm soil profiles, while among the land use patterns. the forest land (4.31 g•kg-1) was the highest, and followed by the terraced field (4.25 g•kg-1), grassland (4.12 g•kg-1), shrub land (3.82 g•kg-1) and cultivated land (3.47g•kg-1). Obviously the forest land, terraces, grassland and shrub land was 24.2%, 22.4%, 18.7% and 10.1%, respectively, higher than the cultivated land. SOC in the topsoil was more susceptible to environmental factors, like terracing and some other soil erosion control practices, which can obviously sequestrate SOC in the deep soil layers (>20 cm). Variance component estimation shows that interactions between land use, topography, depth, land use and topography had extremely significant influences on spatial distribution of SOC content (P <0.01). Topography contributed the most to total SOC, reaching 32.50%. And interactions between land use & topography explained 7.4% of the variability of SOC. Spatially, SOC was distributed in patch and increased with depth in the watershed, and turned to be homegeneeous in distribution. 【Conclusion】All the findings in this study may serve as theoretical foundations for water and soil conservation and evaluation of carbon sequestration effects.

    • Effects of Specialized Vinasse Organic Manure on Yield and Quality of Flue-cured Tobacco in Karst Area

      2019, 56(5):1151-1160. DOI: 10.11766/trxb201809180395

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      Abstract:【Objective】This study was trying to find out a proper application rate of specialized vinasse organic manure for flue-cured tobacco in Guizhou karst area.【Method】A field experiment was designed and laid out to have 5 treatments. i.e. CK (3 t•hm-2 of conventional vinasse organic manure), T1 (3 t•hm-2 of specialized vinasse organic manure), T2 (3.6 t•hm-2 of specialized vinasse organic manure), T3 (3.6 t•hm-2 of specialized vinasse organic manure, + 300 kg•hm-2 of potassium fertilizer, and T4 (1 t•hm-2 of specialized vinasse organic manure + 2 t•hm-2 of chemical fertilizer), and carried out for analysis and comparison of effects of the five treatments on ecology and yield of flue-cured tobacco.【Result】Results show that compared with CK, Treatments T1, T2 and T4 improved the crop in plant height, stem circumference and leaf area to a varying degree; Treatments T1, T2 and T3 did in root fresh weight, root dry weight and root volume; Treatment T4 increased rhizosphere indexes significantly;Treatment T1 and T2 reduced the incidence of black mites by 49.8%; Treatment T1, T3 and T4 lowered the incidence of climate spot disease by 62.5%, 37.5%, and 25%, respectively; and Treatment T2, T3 and T4 got free of mosaic disease. In terms of production of flue-cured tobacco, Treatment T4 was the highest in yield and followed by Treatment T1 and T2, reaching 1623 kg•hm-2 and 1434 kg•hm-2, respectively, and Treatments T1~T4 increased by 10.4%~25.0% over CK. The contents of nicotine, total nitrogen, total sugar, reducing sugar, phosphorus, potassium and chloride ions in tobacco leaves of all the tested treatments varied within the suitable range of high-quality tobacco leaves. Application of specialized vinasse organic manure reduced the content of nicotine, total nitrogen and phosphorus, and kept the potassium ion content in a proper range that made internal quality of the flue-cured tobacco gradually reasonable. 【Conclusion】In summary, the use of the specialized vinasse organic manure in addition to chemical fertilizer can improve growth and development as well as quality of the flue-cured tobacco.

    • Variation of Nitrogen Mineralization and Nitrification in Agricultural Soils in Cixi along a 1000-Year Chronosequence

      2019, 56(5):1161-1170. DOI: 10.11766/trxb201810120465

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      Abstract:【Objective】 It is still unclear how key soil nitrogen (N) transformed and how the microbes involved in the transformation evolved along a long-term chronosequences of the soil in the coastal polders in Cixi. 【Method】An indoor incubation experiment was carried out using soil samples collected from coastal polders in Cixi with cultivation age varying in the range of 0~1 000 years to determine N mineralization rate (NMR), nitrification intensity (NI) and number of nitrobacteria (NN). 【Result】Results show that soil conductivity (EC) and pH decreased with aging of the soil, while soil organic matter (SOM) and total N (TN) accumulated in the topsoil, and soil properties changed significantly, especially during the first 50 years of cultivation. NMR varied in the sequence of 220~1 000 a > 0~50 a > 60~200 a; NI displayed a general rising trend with the cultivation going on year after year , but NN increased in the first 20 years, and peaked during the years of 20~60 and then turned downwards gradually, Person correlation and aggregated boosted tree (ABT) analyses show that cultivation history of the soil, EC, and SOM concentration were the dominant affecting factors, explaining 45%, 12% and 11% of the variation of NI, respectively, while soil NH4+-N and available P contents were the ones, explaining 86% and 42% of the variation of NMR and NN, respectively. 【Conclusion】 Therefore, it could be concluded that during the course of sustainable agricultural utilization of the coastal polders nitrification intensity and nitrobacteria abundance increases to a certain extent, but they are subject to the joint impact of historical conditions and contemporary environmental factors.

    • Effects of Simulated Pudding on Structure of Paddy Soil and Organic Nitrogen Mineralization Therein

      2019, 56(5):1171-1179. DOI: 10.11766/trxb201811050484

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      Abstract:【Objective】Soil structure plays an important role in nitrogen transformation processes. Puddling, a key process of rice cultivation, generally conducted to level and prepare paddy fields for rice transplantation, greatly alters soil structure, which in turn affects soil nitrogen transformation. However, quantitative knowledge of the influence of puddling on nitrogen mineralization is still absent. 【Method】In this study, puddling practice was simulated in the lab by stirring the Hubai paddy soil in a PVC vessel and then incubated for four weeks, for investigation of effects of stirring on soil structure and organic nitrogen mineralization. The incubation experiment was designed to have three treatments in stirring intensity, i.e. no stirring (CK), a low intensity stirring (LIS) and a high intensity stirring (HIS). Soil aggregates were fractionated by particle size and their water stabilities determined with the wet-sieving method. The X-ray computed tomography and image processing technique was used to determine pore size distribution of the soil in each treatment. Mineralized nitrogen was measured with the organic nitrogen mineralization incubation method. 【Result】Compared with CK, both LIS and HIS significantly decreased the proportion of >1 mm aggregates and the mean weight diameter of water stable aggregates, but did not differ much between the two in the effect. Cumulative porosity of the soil in CK, LIS and HIS was 3.3%, 3.2% and 3.3%, respectively, showing no big difference between the treatments. However, the three treatments did show significant differences in soil pore morphology. In CK, numerous big channels high connectivity were found, while in LIS and HIS, spherical or ellipsoidal voids low connectivity were found. Organic nitrogen mineralization in LIS and HIS increased rapidly and exceeded that in CK for the first week after stirring, but declined down even below that in CK from the second week on. At the end of the incubation, CK was found to be higher than LIS and HIS in cumulative nitrogen mineralization and mineralized nitrogen potential. 【Conclusion】Results show that stirring or puddling increases nitrogen mineralization rate in the early stage, however decreases cumulative nitrogen mineralization in the end. Correlation analysis shows that soil organic nitrogen mineralization is significantly and positively related to macroaggregate content and 30~100 μm pores. However, more studies are needed to differentiate the effects of aggregate breaking down and pore restructuring on nitrogen mineralization as a result of puddling.

    • Ammonia Emission Following Basal and Tillering Fertilization in Taihu Lake Region relative to Monitoring Techniques

      2019, 56(5):1180-1189. DOI: 10.11766/trxb201811050505

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      Abstract:【Objective】 Ammonia volatilization loss is liable to occur after application of chemical nitrogen fertilizer onto paddy fields. Ammonia emitted from the fields brings about adverse effects on the air and water environment, such as smog and eutrophication. So far little has been reported about studies to compare synchronously the uses of different methods to monitor ammonia emission from paddy fields in China, which affects scientific assessment of ammonia emission from paddy fields and recommendation of rational application of nitrogen fertilizer in paddy fields. 【Method】 Ammonia emissions after basal and tillering fertilizer application were monitored simultaneously with three techniques different in monitoring principle, that is, micrometeorological mass-balance integrated horizontal flux (IHF), dynamic chamber technique and static chamber technique, during the rice growing season of 2017 in the Taihu Lake region. The IHF technique had five ammonia samplers fixed at 0.4 m, 0.8 m, 1.2 m, 1.8 m, and 2.8 m high above the floodwater surface along a pole erected in the center of circular plots (20 m in radius). The dynamic chamber technique was designed to have an air exchange rate of 17 times per minute. And the static chamber technique had the sponge in the chamber replaced daily after N fertilizer application. At the same time, NH4+-N concentration and pH in the floodwater on the surface of the paddy field was measured. 【Result】 Results show that dynamics of the daily ammonia emissions monitored with the three methods were quite consistent in feature. Ammonia emission peaked on the 3~4th day after the basal fertilization and the second day after the tillering fertilization. No significant emission was observed one week after the basal or tillering fertilizer application. In the monitoring, regardless of the methods, ammonia emission fluxes were found positively related to concentration of NH4+-N in the floodwater. The horizontal ammonia flux at 0.4 m above the surface water reached 131.0 μg·m-2·s-1the second day after the basal fertilization, and the flux at 0.8 m above the surface water reached 137.9 μg·m-2·s-1 the second day after the tillering fertilization. The horizontal ammonia flux at 2.8 m was 35.3~66.5 μg·m-2·s-1 and 20.2~39.8 μg·m-2·s-1 after the basal and the tillering fertilization respectively. Cumulative ammonia emission relative to micrometeorological technique, dynamic chamber technique and static chamber technique after the basal fertilization was measured to be 34.6 kg·hm-2, 38.2 kg·hm-2 and 12.9 kg·hm-2, accounting for 32.0%, 35.4% and 11.9% of the basal N fertilizer applied, respectively, and that after the tillering fertilization was 26.7 kg·hm-2, 16.8 kg·hm-2 and 11.8 kg·hm-2, accounting for 33.0%, 20.7% and 14.6% of the tillering N fertilizer applied, respectively. The ammonia emissions monitored with the three different methods displayed nice linear relationships between each other. The dynamic chamber method was quite approximate to the IHF method in total ammonia emission after the basal and tillering fertilizations, while the static chamber method underestimated the actual ammonia emission after the basal and tillering fertilizations, down to only 40.4% of that monitored with the IHF method, because the air exchange in the static chamber tended to be hindered. 【Conclusion】 Loss of the basal and tillering N fertilizers through ammonia emission is serious, when a large amount of nitrogen fertilizer is applied into flooded paddy fields at the time air temperature is high and nitrogen adsorption capacity of rice plant is low. The dynamic chamber method can be used to monitor ammonia emission from paddy fields after basal and tillering fertilizations. However, when the dynamic chamber method is used to monitor ammonia emission from soil-water surface after fertilization, the airflow exchange rates should be taken into account. Furthermore, after basal fertilizer is applied, the ridges of the experimental plots should be made capable of conserving water and nutrients to prevent water exchange through the ridge.

    • Changes in Nitrogen and Phosphorus in Surface Water of Paddy Field in Jianghan Plain

      2019, 56(5):1190-1200. DOI: 10.11766/trxb201811230529

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      Abstract:【Objective】Because of extensive management of water and nutrients in rice cultivation, especially artificial drainage of just fertilized paddy fields for mechanized rice transplanting and direct rice seeding, non-point source N and P pollution turned out to be very serious in Jianghan Plain, posing a great threat to the safety of agricultural water and drinking water. N and P in paddy field surface water are the direct sources of non-point source N and P pollution. It is, therefore, essential to master rules of the changes in N and P in paddy field surface water to preventing and controlling the non-point source N and P pollution from paddy fields. However, at present, it is still unclear how N and P changes in paddy fields surface water and how fertilizer application affects the changes in the Jianghan Plain. This is a topic that calls for further studies. 【Method】In this study, a field experiment, designed to have a number of treatments varying in N and P application rate along a gradient, was carried out to explore how N and P changes in paddy field surface water and how fertilizer application affects the changes. Samples of paddy field surface water were collected for 8 consecutive days after each fertilizer application for analysis of total N (TN), total soluble N (DTN), soluble organic N (DON), NH4+-N and NO3--N, total P (TP), total soluble P (DTP), and particulate P (PP). 【Result】Results show that total soluble N (DTN), soluble organic N (DON) and NH4+-N accounted for 88.0%, 44.7% and 31.6%, respectively, of the total N (TN) in surface water, after application of urea, and increased with increasing N application rate, while particulate P (PP) made up 76%~93% of the total P (TP) after application of superphosphate, but decreased with increasing P application rate. A piecewise linear correlation was observed between N concentration in surface water and N application rate. With increasing N application rate, N in surface water would increase in concentrations, and when N application rate exceeded 287.8, 289.9, 231.5 and 336.7 kg·hm-2, TN, DTN, NH4+-N and DON would jump by a large margin, respectively. All forms of P in surface water would increase linearly in concentraton with increasing P application rate. TN and DTN peaked 1 day after urea application, and then leveled off 5 days after basal and tillering fertilization and 2 days after panicle fertilization. NH4+-N reached its peak value 2 days after basal and tillering fertilization and 1 day after panicle fertilization, and then leveled off 5 days after basal and tillering fertilization and 2 days after panicle fertilization. TP, PP and total soluble P (DTP) reached their respective peak values quickly just in 1 day, and then decreased sharply by over 79.0% 3 days after superphosphate application. 【Conclusion】DTN, especially DON and NH4+-N are the main forms of N in surface water after urea applicaton. PP is the main form of P after superphosphate application. Reducing the N and P application rates can reduce the concentrations of N and P in surface water and their losses as well. So it is advisable to control N application rate within 231.5 kg·hm-2. The first 5 days after basal and tillering fertilization and 2 days after panicle fertilization were the optimal periods key to controlling N loss from paddy fields, and 3 days to controlling P loss.

    • Biological Effects of Biochar on Nitrogen Fertilizer Reduction and Nitrogen Fertilizer Utilization Effciency of Pod Pepper in Yellow Soil of Guizhou

      2019, 56(5):1201-1209. DOI: 10.11766/trxb201809260438

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      Abstract:【Objective】In recent years, biochar has extensively been used as an important fertilization amendment to improve crop quality and fertilizer use efficiency, but little is applied in the yellow soil for pod pepper cultivation in Guizhou. Therefore, this paper was oriented mainly to explore effects of application of biochar on nitrogen content in pod pepper growing in yellow soil of Guizhou.【Method】A field experiment was conducted to study effects of combined application of biochar and N fertilization on yield, quality, nutrient accumulation and nitrogen fertilizer utilization efficiency of pod pepper. The experiment was designed to have four treatments, different in combination ratio, i.e., CF100B0 (Chemical N fertilizer 100% and Biochar 0%), CF90B10 (Chemical N fertilizer 90% and Biochar 10%), CF85B15 (Chemical N fertilizer 85% and Biochar 15%) and CF80B20 (Chemical N fertilizer 80% and Biochar 20%).【Result】Results show that compared with Treatment CF100B0, Treatment CF90B10 increased the yield of pod pepper, by 7.3% in fresh weight and by 2.5% in dry weight while Treatments CF85B15 and CF80B20 decreased the yield slightly. Combined application significantly affected the contents of nitrate and Vc in the fruit of pod pepper. The content of nitrate in the fruit decreased by 4.8%~8.9% in Treatments CF90B10, CF85B15 and CF80B20, while the content of Vc increased by 9.6% only in Treatment CF90B10. But no difference was found between the treatments in content of reducing sugar and free amino acids. In addition, the treatments, especially CF90B10, increases PFPN by 2.08~2.62 kg·kg-1, but lowered AEN and REN in a trend with rising biochar ratio, so Treatment CF90B10 was the highest in AEN and REN, being 7.7 kg·kg-1 and 40.3% respectively.【Conclusion】On the whole, the application of biochar to substitute portion of nitrogen fertilizer can effectively ensure stable yield and N utilization efficiency of pod pepper in Guizhou. The use of biochar to substitute 10% of the chemical nitrogen fertilizer is the best in biological effect and hence recommended as the most suitable formula of fertilization for pod pepper production in the yellow soil of Guizhou.

    • Characterization of Soil Microbial Community Structure as Affected by Vegetation in Jinyun Mountain

      2019, 56(5):1210-1220. DOI: 10.11766/trxb201807160157

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      Abstract:【Objective】Soil microbes are key factors affecting material recycling and energy flow in the soil micro-environment. To explore impacts of vegetation, relative to forest type, on topsoil microbes in community structure and abundance, soil samples were collected from woodlots, different in type, i.e. coniferous forest, broad-leaved forest, mixed broadleaf-conifer forest and, P. pubescen forest, in the Jinyun Mountain National Nature Reserve for analysis. 【Method】 To analyze the soil samples, multiple molecular techniques, such as Clone library, qPCR and (T-RFLP (Terminal restriction fragment length polymorphism analysis), and conventional soil physical-chemical property analysis procedures were used.【Result】1) Among the soils under four types of forest vegetations, the soil coniferous forest was the lowest in microbial copy number, and bacteria were higher in copy number of 16S rRNA gene than the other two types of soil microbes (archaea and fungi) and were the most remarkably by vegetation (P<0.05). Meanwhile, Pearson correlation analysis of microbial copy number and soil physical-chemical properties shows that bacteria and archaea was significantly related to pH (r=0.607,P<0.05) and water content (r=-0.919,P<0.01), respectively, in copy number. 2) Based on the T-RFLP fingerprint, the α-diversity index of the soil bacterial community structure shows that fungi was the highest in community structure diversity, while archaea was the lowest and significantly influenced by vegetation (P<0.05). Non-metric Multidimensional scaling (NMDS) and Heatmap analysis both show significant difference in soil microbial community structure existing between the soils under different vegetation (P<0.05), with the bacteria and fungus in the coniferous forest soil being particularly unique in community structure. 3) All the soils had their own dominant groups of soil microbes which varied with vegetation, especially, the soil under P. pubescen forest being the most distinct. And 4) Redundancy analysis (RDA) shows that community structures of the three species of soils microbes were all significantly affected by pH, potassium and phosphorus (P<0.05).【Conclusion】In the Jinyun Mountains, variation of vegetation affects significantly the topsoil microbes (bacteria, fungus and archaea) significantly in community structure and abundance. The above research is better to understand the relationship between soil microorganisms and forest productivity and its development and succession, and further to provide scientific basis for the protection and sustainable management of natural forests.

    • Community Composition and Diversity of Fungi in Soils under Different Types of Pinus koraiensis Forests

      2019, 56(5):1221-1234. DOI: 10.11766/trxb201810290533

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      Abstract:【Objective】To investigate community composition and diversity of soil fungi in relation to type of Pinus koraiensis forest, a field survey was carried out in the Liangshui National Nature Reserve, where there are four types of Pinus koraiensis forest, that is, Picea koraiensis and Abies fabri-Pinus koraiensis forest, Tilia amurensis-Pinus koraiensis forest, Pinus koraiensis plantations and Pinus koraiensis secondary forest.【Method】Soil samples were collected under the four types of Pinus koraiensis forests for analysis by means of ITS (Internal Transcribed Spacer) sequence based Illumina miseq high-throughput sequencing.【Result】Results show that out of the 16 soil samples collected from the soils under the four types of Pinus koraiensis forests, a total of 505 299 high quality sequences and 534 359 effective sequences and a total of 1316 fungal OTUs were obtained. In the soils of the four types of forests, besides a huge number of unidentified fungi, Ascomycota and Basidiomycota were found to be in dominancy. Distribution of the latter varied from soil to soil (P<0.05).In the soils of the four types of forests, besides a huge number of unidentified fungi, Ascomycota and Basidiomycota were found to be in dominancy.There were significant differences in the distribution of Basidiomycota in the four forest types (P<0.05).And at the genus level, Leptodontidium, Simplicillium, Sebacina, Russula, Penicillium , and Cryptococcus were the dominant ones.The LDA scores of LEfSe analysis show that there were 19 fungi genera with significantly different abundance in four forest types, among 10 genera in the soil under Tilia amurensis-Pinus koraiensis forest and one genera in the soil under natural Pinus koraiensis secondary forest. Alpha diversity analysis shows that the soils under primitivePinus koraiensis forests (Picea koraiensis and Abies fabri-Pinus koraiensis forest and Tilia amurensis-Pinus koraiensis forest) were significantly higher than that under Pinus koraiensis secondary forest in fugal community richness index (Ace and Chao1 index). Beta diversity analysis shows that the soils differed significantly in fungi community composition (r=0.537, P=0.001), but no much difference was found between the two primitive Pinus koraiensis forests and between the Pinus koraiensis plantation and natural Pinus koraiensis secondary forest. Soil pH, moisture content, total porosity, total nitrogen and total organic carbon were the main factors influencing soil fungal community composition in the four forest soils (P<0.05).Correlation analysis of the top 20 dominant genus of fungi and soil physicochemical factors shows that 6 genera were significantly related to soil total nitrogen in relative abundance. Among the six genera, Russula, Suillus and unclassified-f-Thelephoraceae were positively related while Malassezia , Simplicillium and Penicillium were negatively.【Conclusion】There were significant differences in the composition of soil fungal community composition of four types of Pinus koraiensi forests, but there was no statistically difference in the composition of between the two primitive Pinus koraiensis forests and between the Pinus koraiensis plantation and natural Pinus koraiensis secondary forest. Soil total nitrogen may be the main factor affecting the composition of soil fungal communities of four forest types, followed by total organic carbon. All the findings in this study may serve as a theoretical basis for protection of primitive Pinus koraiensis forests, artificial rehabilitation of vegetation and exploitation of the fungal resources in the soil.

    • Genetic 16S rRNA Diversity of Soil Microbes in Rhizosphere of Chinese Yam and its Influencing Factors

      2019, 56(5):1235-1246. DOI: 10.11766/trxb201810290494

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      Abstract:【Objective】Chinese yam (Dioscorea opposita) is a parannial herbal liane popular as vegetable in this country. Its tuber is consumed as both food and medicinal herb for its functions of anti-oxidation, anti-aging, immunity regulation, blood sugar reduction, etc.. Soil ecoenvironmental factors and soil nutrient status are major factors affecting growth and quality of the plant. Soil microbes, in particular, participate in recycling of carbon, nitrogen and some other nutrient elements in the soil, flowing of energy, formation of soil humus, shaping and amelioration of soil structure. This study aims to explore relationships of the soil bacterial community in the rhizosphere of yam with soil nutrients and contents of saccharides in the tuber, and to elucidate major soil ecological factors affecting nutrient accumulation in yam tuber, in an attempt to provide certain reference for development of yam-specfic bio-manure and assessment of soil environment for cultivation of the plant.【Method】Seven samples of rhizosphere soil and rhizomes of 2-year old Chinese yam plants were collected for analysis of composition, abundance, Alpha diversity, Beta diversity and bacteria diversity of soil microbes with the aid of the high-throughput sequencing technology, and for analysis of relationships dominant soil bacterial groups and soil microbial community in rhizosphere with soil chemical factors and saccharides in root with the canonical correlation analysis method.【Result】Results show that Shannon and Chaol indices were significantly and negatively related to soil phosphatese activity; proteobacteria, chloroflexi, acidobacteria and actinobacteria were the dominant bacterial groups in the rhizosphere of Chinese yam; soil pH was an important factor affecting structure and distribution of the soil bacterial community; acidobacteria and nitrifying spirulina was related to sucrase and urease activities in soil; archaea and chloroflexi was positively related to soil organic carbon and nitrogen; soil carbon, nitrogen nutrient was positively related to soluble sugar, crude polysaccharides and starch in the root of yam. Chloroflexi and Thaumarchaeota, dominant soil bacterial groups were positively related to total organic carbon, total nitrogen, AK, AP and phosphatase activity in rhizosphere soil, and to content of starch and crude polysaccharide (spearman correlation index is 0.54, P<0.01 ) in tuber, too, which indicate that the above-mentioned chemical properties plays important roles in growth of the plant; Acidobacteria was negatively related to soil pH, AP and catalase and positively to total organic carbon, AK and invertase activity in soil, and negatively related to crude polysaccharide in tuber, too; Nitrospirae and Actinobacteria was positively related to activity of urease and catalase, and negatively to phosphatase and sucrase; Proteobacteria and Nitrospirae was positively related to soluble sugar and negatively related to crude polysaccharide.【Conclusion】All the findings demonstrate that the dominant bacterial groups in the rhizosphere of Chinese yam are proteobacteria, chlorobacteria, acidobacteria and actinomycetes; Soil pH is an important factor affecting structure of the soil bacterial community.Acidobacteri and nitrospira may improve carbon and nitrogen levels in the soil through stimulating the activity of sucrase and urease in soil; archaea and chlorobacteria promotes TOC and AN recycling in rhizosphere soil and increase TOC and AN nutrient supply in the soil, which in turn promotes accumulation of soluble sugar, crude polysaccharides and starch in rhizome of yam.

    • Influence of Electrode Contact and Distance on Soil Resistivity Measurement

      2019, 56(5):1247-1258. DOI: 10.11766/trxb201810160413

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      Abstract:【Objective】The use of resistivity method in soil test has a number of shortcomings in accuracy and electrode is an important factor affecting accuracy of the test. In most tests, efforts are made to minimize contact and select appropriate electrode distance on the simple operational level. So accuracy of the test results is hard to correct and unify. Therefore, systematic analysis and quantification of these problems are required. If it is feasible to determine influences of contact and distance of the electrodes on test results, interference of the electrode can be avoided to the maximum extent, especially in pole-pole method. It is expected that this study may provide certain reasonable suggestions for electrode placement to minimize deviation of the test results in using the resistivity test device.【Method】In this paper, the soil-box resistivity test model was used to measure soil resistivity in zinc-contaminated sand used as simulated soil in the test. The test was designed to have three variables, i.e. soil water content, diameter of the electrode and distance between two electrodes for measurement of its AC resistance and resistivity (simply referred to as resistance and resistivity in the forthcoming paragraphs).Through the test with the indoor system and simulation of COMSOL physical field, influences of electrode contact degree and distance between electrodes on resistivity and its measurement were explored, a corresponding resistivity accuracy analysis model established, influences of contact and distance of electrodes on the test results discussed, and comparative analysis of errors and deviations of the test performed. 【Result】Results show that the experimental research and numerical simulation could verify and supplement each other, which indicates that the electric conductivity test model derived in this paper is correct. The electric conduction model could be divided into a normal section and transition sections at each end, connected in tandem. By means of the simulation, radial current density is used to reflect lengths of the transition sections and figured out the degree of current deviation. The change of current flow network produced shrinkage resistance in transition sections. Both shrinkage resistance and lengths of the transition sections decrease with the increase of contact degree, but are not affected by the distance between electrodes. After the length of the transition section was worked out, deviations of the resistivity of the transition and normal sections could be calculated numerically and accurately in line with the equation for calculation. Error analysis shows that the measured value of comprehensive resistivity gradually approaches that of normal resistivity with the expanding contact area and the extending distance of the electrodes. 【Conclusion】In summary, to keep electrodes in contact and properly apart is an effective way to reduce relative errors of the test to measure resistivity. In this study through numerical analysis, it is leant that deviation of the measurement of resistivity is caused by incomplete electrode contact and resistivity values of the normal sections can be worked out. All the findings in this study may serve as theoretical guidance and technical support for perfect electrodes arrangement and higher accuracy of the measurement of resistivity.

    • >Research Notes
    • Emission of Acidified Gas from Intercropped Wheat Field Based on LCA Analysis

      2019, 56(5):1259-1268. DOI: 10.11766/trxb201809120312

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      Abstract:This study was to comprehensively analyze effects of wheat and faba bean intercropping in wheat fields on environmental acidification and yield of the crops. Two two-year field experiments, (A and B), were carried out and analysis of the results of the experiments done for effects of wheat and faba bean intercropping on crop yield, energy consumption and environmental acidification based on LCA(life cycle assessment) by comparison. Results showed that in the two experimental fields, intercropped wheat was significantly of 22.04% higher than mono-cropped one in yield on average with land equivalent ratio (LER) being higher than 1, showing obvious intercropping advantage. Compared with monocropped wheat, intercropped wheat decreased by 18.59% and 17.45% in energy consumption and environmental acidification index, respectively, and by 17.42%, 17.68% and 17.82% in emission of SOx, NH3 and NOx, respectively, and hence was 18.96% and17.45% higher in potential of mitigating the environmental impact of energy consumption and environmental acidification of wheat cultivation. In conclusion, wheat and faba bean intercropping can significantly increase yield of the wheat and reduce emission of acidified gases, which are obvious intercropping advantages.

    • Modification of Alpha Approximation Model for Retrieving Soil Moisture Data Based on Multi-temporal Sentinel-1 SAR

      2019, 56(5):1269-1278. DOI: 10.11766/trxb201807270361

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      Abstract:The applicability of the Alpha approximation model for retrieving soil moisture data from multi-temporal SAR data will be affected when incidence angles change. Aiming at this problem, the Alpha model is modified based on the theory of Small Perturbation model, and verified it with the time series Sentinel-1 SAR data of Heihe and Winnipeg, the two experimental areas coupled with the ground observation network therein. A correlation analysis was done of the inversion with the observation data. It was found that the correlation coefficient increased from 0.473 and 0.601 to 0.851 and 0.821 respectively, while the root mean square error (m3• m-3) decreased from 0.053 and 0.152 to 0.023 and 0.065 respectively. In order to further evaluate quality of the model, the NSE coefficient which is commonly used in hydrology for evaluation of model was introduced for use. The NSE before and after the modification were -0.532 and -1.243, 0.713 and 0.588, respectively. The results show that though a certain relationship was found between the inversion using the original model and the measurement in data, a quite big error was too. However, once the model is modified as above mentioned, the impact of changes in incidence angle can be well corrected, making the inversion more reliable, which extends the application of the Alpha model.

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