• Volume 55,Issue 6,2018 Table of Contents
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    • >Reviews and Comments
    • Research Progress on Benggang Erosion and Its Prevention Measure in Red Soil Region of Southern China

      2018, 55(6):1297-1312. DOI: 10.11766/trxb201807030219

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      Abstract:The benggang is a typical type of severe erosional morphology with a very high intensity of sediment transfer. This erosional morphology is widely distributed in the granitic red clay soil regions in the seven provinces of southern China. Benggang erosion seriously threatens regional ecological security and has been a key and hot spot in the soil erosion community. This paper aims to review the existing benggang research progresses and provide some insight for strategies of the benggang restoration. The paper first reviewed the research process of Benggang erosion and made an introduction of the constituent elements of Benggang. Then, the research status and progresses of Benggang erosion and control technologies were summarized from five aspects: erosion types, zonal distribution characteristics, developmental stage and morphological characteristics, driving factors, and control techniques. The weakness of the current research was also discussed. Finally, the paper put forwards some scientific issues that should receive more attention, including the coupling mechanism of Benggang hydraulic erosion and gravity erosion, the relationship between Benggang development and regional geomorphic development, the establishment of index for Benggang formation and development, the mechanism of Benggang prevention and control.

    • Direct Interspecies Electron Transfer of Microbes: Mechanism and Application

      2018, 55(6):1313-1324. DOI: 10.11766/trxb201805240172

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      Abstract:Microbial interspecies electron transfer (IET) refers to the electron exchange between electron-donating microorganisms and electron-accepting microorganisms that forms a syntrophic growth relationship between the two thus enabling the two to jointly accomplish a certain metabolic process that no single microorganism can do. Moreover, it also plays a significant role in biogeochemical processes, such as degradation of organic matter, production of bioenergy and reduction of greenhouse gas emission. IET could be sorted into direct IET (DIET) and indirect or mediated IET (MIET). DIET occurs when there is a biological electrical connection and a difference in voltage potential, whereas MIET relies on diffusion of redox carriers driven by concentration gradients. Generally MIET needs hydrogen, formate or flavin as electron carrier, while DIET is found done directly through nanowire (e-pili), redox protein or conductive particles. Interspecies hydrogen/formate transfer, one type of MIET, occurs commonly in methanogenic microbial community, such as S organism and Methanobacterium ruminantium, Desulfovibrio vulgaris and Methanosarcina barkeri. In addition, sulfide, L-cysteine and AQDS can act as electron shuttles mediating electron transfer between microorganisms, such as Desulfuromonas acatoxidans and Prosthecochloris aestuarii. However, electron transfer between Geobacter species so far has only been documented to be direct: by way of e-pili and c-type cytochromes. Either of these Geobacter cells short of biological connections, such as e-pili and (or) cytochromes, can not get syntrophically related. Nevertheless, with the mediation of conductive materials, such as activated carbon and biochar, e-pili would become less functional during the process of DIET since syntrophic partners could exchange electrons via these conductive carbon materials. Moreover, conductive mineral magnetite can substitute for outer-membrane c-type cytochrome in its role. Mutant strain of G. sulfurreducens that is deficient in OmcS cannot co-culture with G. metallireducens, but with the addition of magnetites they can exchange electrons successfully. The discovery of DIET has changed the tradition gnosia that microbial syntrophic metabolism would not occur without energy carriers, such as hydrogen and formate, and has opened up a new scientific perspective for understanding biogeochemical processes, such as circulation of C/N/S, emissions of greenhouse and degradation of pollutants. The core of microbial IET is electron transfer between microbes. Further studies should be done on mechanism of IET and new effective IET microorganisms in order to put IET into practical engineering application. However, the researches on tmechanism of IET between microbes, at present, are still in their preliminary stage and so have a number of problems to be solved, for example, how exactly electron transfer occurs between microorganisms, whether there is any microorganism more IET efficient, and if there is any method that can more economically and efficiently accelerate IET, etc. In this review, the mechanisms of MIET is summarized, meanwhile, the three mediating mechanisms for DIET are expounded emphatically. Representative microbes participating in IET are introduced. Potential applications of IET to environment processes such as methane-producing anaerobic digestion, anaerobic methane oxidation and dechlorination are proposed and directions of future researches on IET discussed.

    • >Soil Changes under Anthropogenic Influences
    • Study of Chronology of the Meadow Soil in the Qinghai Lake Basin by Means of Optically Stimulated Luminescence

      2018, 55(6):1325-1335. DOI: 10.11766/trxb201801090021

      Abstract (1859) HTML (745) PDF 2.55 M (2330) Comment (0) Favorites

      Abstract:【Objective】Soil chronology is of great pedogenetic significance, for it is closely related to the forming and developing processes of a soil. In this paper, the Optically Stimulated Luminescence (OSL) dating method was employed to determine age of the alpine meadow soil in the Qinghai Lake Basin on the northeast fringe of the Qingzang Plateau. Four alpine meadow soil profiles (XPSD1, XPSD2, RYS1 and RYS2) were prepared for dating. Adaptability and reliability of the OSL dating method for alpine meadow soils in the Qinghai Lake Basin was evaluated. Pedogenic process and its climatic background were also discussed. 【Method】The silt-sized (38~63 µm) quartz OSL single-aliquot regenerative (SAR) dose protocol was used to acquire equivalent dose (De). OSL signals of all the samples decayed very quickly, displaying characteristics of the signals of the typical fast quartz fraction. The preheating test set 240 ℃ as preheating temperature. All De distributed quite concentratively, showing a Gaussian distribution curve, which demonstrates that the quartz particles in the profile of Xiangpishan were well bleached before deposition. Environmental dose rates were determined using the inductively coupled plasma mass spectrometry (ICP-MS). Eventually age of the meadow soil of the profile was determined. In addition, development of the soil was characterized through analysis of particle size and organic matter content of the soil.【Result】According to the theory of pedogenesis, the genetic horizon of the meadow soil could be divided into grass felty layer (Afe), humus layer (Ah), parent material layer overlapped with a humus layer (CAhb) and parent rock layer (C). The bottom of XPSD1, XPSD2, RYS1 and RYS2 dated back 0.9±0.1 ka, 16.2±1.8 ka, 3.2±0.2 ka and 3.7±0.2 ka, respectively. The parent materials of the alpine meadow soil in the Qinghai Lake Basin was mainly of aeolian loess deposit, with 50%~75% of silt, 10%~40% of sand and 10%~20% of clay, so the soil is sorted as sandy silt. The aeolian dust plays an important role in the pedogenetic process of the alpine meadow soil in the Qinghai Lake Basin. Considering the alpine meadow soil features strong grass and humus accumulation, the OSL of the bottom of the Ah layer or the interface between the Ah and CAhb layers is used as indicator for dating of the alpine meadow soil. The OSL dating results demonstrate that the meadow soil in the Qinghai Lake Basin developed mainly during late Holocene (4~0 ka). The phenomenon of an inverted chronosequence of old upper layer (2.6±0.1 ka) and new bottom layer (70 cm depth, 0.6±0.1 ka) was discovered at Profile XPSD2, which could probably be attributed to the effect of freezing and thawing erosion.【Conclusion】The OSL dating method is validated to be adaptable and reliable for dating alpine meadow soils. The alpine meadow soil in the Qinghai Lake Basin is derived from aeolian deposits, and follows the mode of aeolian dust aggradation in soil development. The alpine meadow soil in the Qinghai Lake Basin formed mainly during the late Holocene (4~0 ka) and is deemed to be a product of dry and cold climate, taking into account the environmental records of the region. In profile XPSD2, the bottom loess parent material layer goes in parallel unconformable contact with the upper soil layer, showing a deposition hiatus of ~14 ka.

    • Hyperspectral Estimation of Soil Moisture Content in Rammed Soil of Qi-Dynasty Great Wall Based on MSC and SVM

      2018, 55(6):1336-1344. DOI: 10.11766/trxb201803070044

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      Abstract:【Objective】The Qi-Dynasty Great Wall is made up of rammed soil, in which soil moisture plays an important role. Excessive moisture in the soil will lead to partial collapse of the wall. Therefore, it is of great significance to estimate soil water content in the rammed earth of the Great Wall so as to protect the relics of Great Wall. Although the traditional soil moisture measuring method is quite high in precision, it is rather labor- and time-consuming and rigorous in measuring environment. The use of hyperspectral technology has the characteristics of rich data/information, high-efficiency and non-destructiveness, which makes up for the shortages of the traditional measuring methods. In recent years, scholars at home and abroad have found that the multiple scattering correction method can eliminate the scattering effect caused by particle size variation of the samples, and then the difference in physical scattering information between different spectra. However, so far little has been reported about researches on whether the spectra corrected with the MSC method can make wavelength optimization more accurate. 【Method】 In this paper, the Qi-Dynasty Great Wall in Huangdao District of Qingdao City was cited as object of the study, and samples were collected vertically along the Wall. Initial soil moisture content of the samples were determined with the oven-drying method, and soil hyperspectral data was obtained using the US ASD FieldSpec4 portable spectrometer. In order to study effect of soil moisture content on soil spectral characteristics, soil samples 6.16%, 8.94%, 10.27%, 14.10%, 18.03%, and 24.29% in moisture content were selected for acquisition of hyperspectral reflectivity curves. In order to verify the effect of MSC on the preferred sensitive wavelengths, the primary spectral reflectance of the soil was pretreated with Lg(R)' and MSC+Lg(R)', separately, and then correlation analysis was done between primary spectral reflectance and soil water content for screening sensitive wavelengths; based on the spectral data that had been pre-processed separately with Lg(R)' and MSC+Lg(R)', support vector machines (SVM)-based soil moisture content hyperspectral estimation models were constructed.【Results】Results show that spectral curves of the soil samples, regardless of soil moisture content, varied on the whole quite similarly, declining gradually with rising soil moisture content. For a specific band, the response of spectra to soil water content varied in characteristic with band region; when the soil moisture content was low, with rising soil moisture content, the reflectivity in the shortwave and infrared bands varied sharply. The sensitive bands of the spectral reflectance of the rammed Wall soils pre-treated with Lg(R)' and MSC+Lg(R)' were mainly concentrated in the range of 1 450~1 500nm, 1 850~1 900nm and 2 050~2100nm. After the logarithmic first order differential treatment of the original spectral data, only four wavelengths relatively high in correlativity were obtained, whereas after the pretreatment with MSC+Lg (R)' seven were, that is, 1 861nm, 1 866nm, 1 549nm, 1 885nm, 1 871nm, 1 895nm and 2 095nm, with significantly higher correlation coefficients, i.e. -0.72, -0.71, 0.7, -0.7, 0.69, 0.69 and 0.69, which indicates that the multi-dimensional scattering correction method can enhance the correlative absorption information between spectra and soil moisture content, thus increasing the correlation between soil spectral reflectance and soil moisture content; The model based on the spectral data pre-treated with Lg(R)' was verified with determination coefficient, Rv2 = 0.679, RE = 0.143, RMSEP = 0.431, and RPD = 1.765, while the model based on the data pre-treated with MSC+Lg(R)′ was found to have Rv2= 0.764,RE = 0.062, RMSEP = 0.159, and RPD = 2.671. Obviously, the former is better than the latter in prediction. All demonstrate that SVM regression models based on the sensitive bands screened out through pretreatment vary somewhat in prediction effect with pretreatment method. 【Conclusion】 All the findings in this study demonstrate that the use of the MSC method to preprocess spectral data can enhance the absorption information related to spectrum and soil moisture content, screen sensitive wavelengths more accurately and have the established SVM estimation model more accurate in prediction.

    • Effects of Biochar on Soil Fertility Quality in Intensive Vegetable Field

      2018, 55(6):1345-1357. DOI: 10.11766/trxb201802250031

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      Abstract:【Objective】This study was carried out to investigate effects of application of nitrogen (N) fertilizer plus biochar varying in rate on soil physico-chemical properties for 30 months (9 consecutive vegetable crops) in an intensive vegetable production system. 【Method】 During the observation period from April, 2012 to October, 2014, nine crops of vegetable were successfully planted, including Amaranth (Amaranthus mangostanus L.), Water spinach ( Ipomoea aquatic Forssk.), Cilantro ( Coriandrum sativum L.), Baby bok choy ( Brassica chinensis L.) and Spinach ( Spinacia oleracea L.). The experiment was designed to have three biochar amendment rates, namely, B0 (without biochar), B1 (20 t hm-2) and B2 (40 t hm-2) and two N application rates, namely, N0 (No N applied) and Nc (1 233 kg hm-2 a-1, the same as in conventional vegetable fields and a typical case of N overdose), thus forming six treatments. In the experiment, compound fertilizer of (N):(P2O5):(K2O) being 15:15:15 in ratio was applied at 313 kg hm-2 to Amaranth and Cilantro, 600 kg hm-2 to Water spinach and 250 kg hm-2 to Baby bok choy and Spinach as the local farmers usually do. Soil samples were collected from the 0~20 cm, 20~40 cm, 40~60 cm, 60~80 cm and 80~100 cm soil layers of every treatment for in-lab analysis at the end of the experiment or right after the harvest of the last vegetable crop on October 30, 2014. 【Result】 Comparisons between the treatments with and without N show that N application significantly increased soil total nitrogen (TN), soil electronic conductivity (EC), bulk density and cation exchange capacity (CEC) by 9.4%~18.1%, 172.4%~241.1%, 5.6%~7.6% and 10.4%~15.0%, respectively, while significantly decreased soil pH by 0.68~1.10; Although two-way ANOVA shows that N application significantly increased the content of soil organic carbon (SOC) by 9.8%~23.4% in all the Nc treatments, except treatment NcB0 where the content the content of SOC decreased by 17.3%, which indicates that biochar helps SOC accumulation in the soil. Besides, amendment of biochar significantly increased soil TN, SOC and CEC by 1.7%~10.0%, 3.6%~48.3% and 8.1%~37.1%, respectively, while significantly decreasing soil EC and bulk density. Meanwhile, biochar significantly increased soil pH in the three N0 treatments by 0.11~0.23, while decreasing soil pH by 0.19~0.23 in the Nc treatments. In addition, interactive effects between N application and biochar amendment on soil TN, SOC and EC were significant according to the two-way ANOVA analysis. Soil NH4+-N and NO3--N content in the experiment varied in the range of 6.6~59.3 mg kg-1 and 23.8~51.3 mg kg-1, respectively. N application significantly increased NH4+-N and NO3--N concentrations in all soil layers of the vegetable soil profiles. They varied with soil depth, and mineral N concentration, too, in a similar trend, that is, declining first and then rising with soil depth in the soil profile; Meanwhile, application of biochar significantly decreased NH4+-N concentration in the 20~40 cm、60~80 cm and 80~100 cm soil layers by 4.9%~47.9 %, while increasing NH4+-N concentration in the 0~20 cm soil layer; Meanwhile, it also significantly increased NO3--N concentration in the top soil layer by 2.4%~29.8% while did reversely in all the deeper soil layers. Moreover, biochar amendment significantly increased the vegetable yield and PFPN (N partial factor productivity) by 7.7%~43.8% and 21.8%~43.8% (p<0.01), respectively, and a significant and positive relationship of crop yield was observed with soil TN and SOC during the experimental period (p<0.01). 【Conclusion】As biochar amendment combined with N application can improve soil fertility and reduce the NO3--N concentration in vegetable soil, the practice may serve to guarantee healthy development of the intensive vegetable production system, and the treatment of amending 40 t hm-2 biochar to application of N at the conventional rate is recommended to be an optimal treatment in this study.

    • Prediction of Variation of Soil Nutrient Status in Reclaimed Subsidence-damaged Farmlands by Filling with Yellow River Sediment Different in Reclamation History in Jining City

      2018, 55(6):1358-1366. DOI: 10.11766/trxb201802250023

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      Abstract:【Objective】Jining is an important energy base in China, thanks to its rich natural resources, like coal. However, decades of mining has caused land subsidence, which has become a protruding environmental problem, destructing large areas of farmlands in the region. Filling with Yellow River sediment has come up as a new method to solve the problem in recent years. The new method can not only help alleviate the hazard of sediment blocking the river course of the Yellow river, but also make full use of the endless filling materials for subsidence reclamation in the eastern plain mining area without any concern about the possibility of secondary pollution. At present, the study on subsidence reclamation using Yellow River sediment as filling is mainly focused on feasibility and cost of the technology. So far no comprehensive and systematic research has been done on reclaiming subsided farmlands with sediment diverted from the Yellow River. 【Method】 In this study, a typical tract of farmland reclaimed by filling with sediment diverted from the Yellow River in Liangshan County, Jining was selected as research object , and another tract of unaffected farmland was cited as CK, both following the same tillage procedure. For years observatory data were collected and analyzed for construction of a regression equation for relationships of various soil nutrient indices and reclamation history, or number of years the reclaimed farmland had been cultivated, and further for variation of soil fertility with reclamation history. On such a basis, this study attempted to predict how long soil fertility of the reclaimed farmland will recover. 【Result】 Results show that with cultivation of the reclaimed farmland going on, soil organic matter, alkalyzable nitrogen, available phosphorus and readily available potassium all exhibited rising trends. The first three indices reached also as high as their corresponding ones in CK in the fifth year, but the last one, though on a rising trend, was only 60% of that in CK. Obviously, it takes only 5 or 6 years for the reclaimed farmland to build up as much as soil organic matter, alkalyzable nitrogen, and readily available potassium as CK has, whereas it may take as long as 15 years for the farmland to accumulate the same amount of effective phosphorus as CK has. The reclaimed farmland is relatively low in available phosphorus, and productivity, and has to be cultivated for quite a long time before it gets recovered in soil fertility. The problem can be solved through modification of the irrigation pattern, rationalization of the cropping system and adoption of split application of P fertilizer, that is, “More frequent application, each at a limited rate” to ensure crop growth and build-up of soil fertility. With cultivation of the reclaimed farmland going on and on, soil organic matter, alkalyzable nitrogen and available potassium in the soil will build up to the same level as in CK. So they are not the limiting factors of the agricultural production in the reclaimed land. But great attention should be paid to building up of soil nutrients in the process of reclamation. 【Conclusion】Therefore, the paper recommends building up and regulating soil nutrients, and reducing nutrient loss, through increasing application of organic manure, planting green manure crops, returning straw to soil, and regulating hydrothermal conditions, etc. to improve soil quality and ensure crop quality. Once the problem of diverting Yellow River water with sediment through a long distance is successfully solved, the technology of reclaiming of subsided farmlands by filling with Yellow River sediment can be popularized for application in coal mining areas alongside the Yellow River in the future.

    • Processes of Leonardite Altering Cation and Anion Composition of Soil Solution in Salt-affected Soil in the Yellow River Delta

      2018, 55(6):1367-1376. DOI: 10.11766/trxb201801110032

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      Abstract:【Objective】To ameliorate salt-affected soil in the Yellow River Delta for productive use is of great social and economic significance to the region. Trials have been conducted to use leonardite as a soil amendment for the purpose, but failed to get consistent results and probe in-depth into the causes. This research aimed to assess changes in salt composition of the soil solution in the salt-affected soil applied with leonardite, and reveal processes and mechanisms of the changes. 【Method】Three topsoil samples (S1, S2 and S3), different in salt contents (1.0, 7.5, and 35.3 mg•g-1, respectively), were collected from a farmland in the Yellow River Delta. After being air dried and gently ground to pass a 100-mesh sieve, the samples were mixed, separately, with leonardite at 0%, 1%, 3%, and 5% in dosage and each treatment had two replicates. Then the mixtures were prepared separately into suspensions (solid: water = 1g: 5ml), which were shaken at 300 r•min-1 for 7 d and then centrifuged at 3 000 r•min-1 for 10 min. The obtained supernatants (or soil extracts) went through a 0.45-μm filter and got ready for analysis of Ca2+, Mg2+, K+, Na+, Cl-, NO3-, and SO42- with ion chromatography. The leonardite used in the experiment was digested by HNO3-HClO4-HF for analysis of Ca2+, Mg2+, K+, and Na+, and its carboxyl and phenolic hydroxyl groups were determined with the titration method of the International Humic Substances Society. 【Result】The leonardite was found to contain Na+ (1.66 mg•g-1), K+ (1.07 mg•g-1), Ca2+ (19.97 mg•g-1), Mg2+(1.60 mg•g-1), carboxyl group (2.74 mol•kg-1) and phenolic hydroxyl group (1.63 mol•kg-1). In the soil solution, sodium adsorption ratio (SAR) decreased with leonardite increasing in spiking dosage, which was attributed to Ca2+ release from and Na+ adsorption to leonardite. In the treatment of adding 5% leonardite to soil S2 SAR reduced from 7.81 to 6.61. In analogy to SAR, Cl-/SO42- molar ratio was proposed as a new indicator to reflect changes in anion compositions. It decreased from 10.20 to 8.25 in the treatment, which was a result of SO42- release from and/or Cl- retention by leonardite. The reduction of SAR and Cl-/SO42- ratio suggests that leonardite could lessen the toxic effects of Na+ and Cl- on plants. 【Conclusion】With Ca2+ and abundant carboxyl groups it contains, leonardite could alter ion compositions in soil solution via: 1) ion exchange between Ca2+ in leonardite and Na+ in soil solution, reducing Na+ concentration in the solution and its harmful effect; 2) replacement of Na+ adsorbed on soil colloids by Ca2+ released from leonardite, favoring formation of soil aggregates and leaching of Na+;and 3)formation of complexes of Na+ in solution with organic substances dissolved from leonardite, reducing Na+ activity and toxicity. It is, therefore, proposed that SAR and Cl-/SO42- ratio be tested as indicators for fast laboratory assessment of suitability of soil amendments for use in salt-affected soils, which would help land managers choose proper soil amendments for use and avoid input of Na-rich organic materials, such as sodium humate, in salt affected soils.

    • >Research Articles
    • Impacts of Forest Typical of the Southern Piedmont of the Himalaya Mountains on Soil Physicochemical Properties and Erodibility K

      2018, 55(6):1377-1388. DOI: DOI:10.11766/trxb201802030436

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      Abstract:【Objective】This paper was oriented to investigate soil physic-chemical properties and erodibility K and their distributions in the southern piedmont of the Himalaya Mountains south,in an attempt to provide certain scientific theories and data base for developing a project of soil and water conservation and ecological construction.【Method】Three different stands of forest typical of the region, i.e., mixed evergreen and deciduous forest(MT-1), mixed broadleaf-conifer forest(MT-4), and evergreen broad-leaf forest in four forest lands(MT-2 and MT-3) on the southern piedmont of the Himalayan Mountains were selected as sample lots and soil samples were collected in the 0~20 cm soil layers for analysis of soil bulk density, porosity, aggregate status, aggregate destruction rate, soil particles size composition and organic carbon content. Besides, soil erodibility K of the lands was calculated using the EPIC model.【Result】(1) The forest stands in the four forest lands exhibited significant impacts on aggregate status,soil particles size composition, organic matter content, and soil erodibility K (P<0.05) of the soil. In the soils, mechanically stable and water-stable aggregates were dominated mainly with aggregates >0.25 mm in particle size, with the former accounting for more than 75% and the latter for more than 60%. on the whole the soil aggregates were quite stable in destruction rate, varying between 10.16%~24.74%. In terms of soil particle size, the soils in the four forest lands were composed mainly of silt, with clay accounting only for 0.51% ~ 3.02%. Organic matter content in the soils of the four lands varied in the range between 92.53 g·kg-1 and 133.8 g·kg-1,and was significantly higher in MT-3 than in the other three (P<0.05), Generally speaking the soils were all quite high in soil fertility; (2) Soil erodibility K in the soils of the four forest lands, though different in soil type varied in the range between 0.1862 and 0.3430 and averaged 0.2635, indicating that they were all moderate on the high side in soil erodibility, but in an order of MT-3 (evergreen broad-leaf forest) > MT-2 (evergreen broad-leaf forest) >MT-4 (mixed broadleaf-conifer forest) > MT-1 (evergreen and deciduous mixed forest);(3) Correlation analysis shows that soil erodibility K was positively related to clay content(r=0.709, P=0.291),silt content (r=0.996, P=0.004), organic matter content (r=0.779, P=0.221)and aggregate destruction rate (r= 0.536, P= 0.464),but significantly and negatively related to sand content (r= -0.997, P = 0.003), however, it did have much to do with soil bulk density and total porosity (r=-0.380, P=0.616; r=0.164, P=0.836).Soil organic matter and silt content were the two main factors affecting soil erodibility K and to a certain extent, soil erodibility could be evaluated by aggregate destruction rate.【Conclusion】The soil erodibility of the study area is relatively high on the whole. As affected by landforms and soil-forming conditions, mixed evergreen and deciduous forest and mixed needle-confierous tree stands are relatively low in soil erodibility K. In the economic production, it is essential to improve the awareness of protection of forest in the regional, prevention of exposure of bare land surface, and implementation of effective soil and water conservation measures,especially in broad-leaf forest land, so as to guarantee successful regional ecological environmental construction and economic development in the study area and even the Zangnan Region.

    • Runoff and sediment yielding characteristics of riparian slope of the lower Yellow River and its relationship with hydrological connectivity

      2018, 55(6):1389-1400. DOI: 10.11766/trxb201803200612

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      Abstract:【Objective】Vegetation and topography are two important factors determining runoff and sediment yielding in slope soil erosion process. Studies reported in the past were mostly focused on effects of single control factors, e.g., slope gradient or vegetation cover, on runoff and sediment yielding, and few were found in the literature on coupling effects of vegetation and topography on runoff and sediment yielding and converging process. The Yellow River Basin in China is one of the most severely eroded regions in the world, and the lower reaches of the River is world-famous for its silt-carrying load. Under the impact of a long history of human activities, its riparian zones have been suffering serious soil erosion. However, little has been reported quantitatively on soil erosion in the riparian zones of the River. What is more, restoration and preservation of the ecological functions of the riparian zones are closely related to the interactive effects of vegetation and topography on soil erosion and hydrological connectivity on the riparian slopes. 【Method】In this study, a field experiment simulating rainfall on riparian slopes along the lower reaches of the Yellow River to investigate runoff and sediment yielding characteristics as affected by rainfall intensity (54 and 90 mm h-1), slope gradient (5°, 10°, 15°, and 20°), and vegetation coverage (0%, 15%, and 30%), as well as effects of slope gradient and vegetation coverage on soil erosion and relationships of runoff and sediment yielding characteristics with flowlength with the aid of a hydrological connectivity model. 【Result】Results show that vegetation cover, regardless coverage, helped reduce runoff velocity under rainfall, no matter how heavy, either 54 or 90 mm h-1 in rainfall intensity, and the effect was the most significant on a slope 30% in vegetation coverage under artificial rainfall, 90 mm h-1 in intensity. Runoff on slopes varied in volume and depth consistently, gradually declining with rising slope gradient and vegetation coverage, and the effect of slope gradient increased gradually with intensifying rainfall. On slopes, < 15°, erosion sediment yield under rainfall 54 mm h-1 in intensity increased slowly with rising slope gradient, however, the effect of slope gradient was not very obvious, whereas on slopes > 15°, the increment became bigger in magnitude. On slopes, < 15°, erosion sediment yield under rainfall 90 mm h -1 in intensity, erosion sediment yield increased with rising slope gradient, whereas on slopes > 15°, it went reversely. Correlation analysis shows that slope gradient was the major factor affecting sediment yield, runoff volume and runoff depth at a significance level of p<0.001, p<0.01 and p<0.01, respectively, while vegetation coverage had a significant effect only on average runoff velocity (p<0.05), but an extra-significant one on flowlength (p<0.001). Runoff had a much longer flowlength on bare slopes than on vegetated slopes, while flowlength on vegetated slopes did not vary much with vegetation coverage. Vegetation cover on slopes was the main reason for difference in hydrological connectivity between slopes. In exploration of hydrological connectivity and runoff-sediment yielding, it was found that they were closely correlated, and runoff and sediment yielding exhibited a rising trend with increasing flowlength. 【Conclusion】Under the interaction of vegetation cover and slope gradient, soil erosion caused by runoff yielding was obviously affected by slope gradient, but not as much as by vegetation coverage. All the findings in this study may serve as references for assessment of soil and water conservation functions of and ecological restoration of degraded riparian zones along the lower reaches of the Yellow River.

    • Effects of Three Kinds of Soil Amendments on Shear Strength of Aeolian Soil

      2018, 55(6):1401-1410. DOI: 10.11766/trxb201802120564

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      Abstract:【Objective】Application of soil amendments to assist desert governance has recently been considered as a promising strategy to improve sand fixing efficiency. However, researches in the past were focused mainly on effects of soil amendments on physicochemical and biological properties of the soil, while this study aimed to reveal those on shear strength of aeolian soils varying in soil water content, in an attempt to provide certain theoretical references for fixing aeolian sands, preventing wind erosion and restoring ecosystems in desert areas. 【Method】In order to explore factors affecting soil mechanics of aeolian soil, soil samples were collected at the edge of the Kumtag Desert for a pot experiment, designed to investigate changes in soil cohesion and internal friction angle via direct shear test. Three kinds of soil amendments were applied, separately into the pots, at set rates, that is, 0.5, 2.0 and 3.5 g•kg-1 for carboxymethylcellulose sodium (CMC); 5, 15 and 25 g•kg-1 for phosphogypsum (PG); and 15, 30 and 45 g•kg-1 for biochar (BC). For each group of treatments, two subgroups different in water content, i.e; 10% and 20%, were also designed. Cotton was planted in each pot and managed in line with the common practice for the crop in the field . At the end of the growth season, soil samples were collected from each pot dried for analysis of cohesion and internal friction angle. Fast shear tests were carried out with a EDJ-1 type direct shear-meter. Four vertical pressures,100, 200, 300 and 400 kPa were applied in the shearing tests, separately. 【Result】Results showed:(1)being the same in soil moisture content, the soil cohesions in the three amended groups were greater than those in the CK group in coherence. Compared with that in CK, cohesion increased by 156.15%~246.18% in Treatments CMC, by 81.06%~229.3% in Treatments PG, and by 71.91%~145.87% in Treatments BC in the subgroup of low water content, and by 126.3%~231.8%, 75.52%~209.9% and 57.79%~124.8%, respectively, in the subgroup of high water content. However, application of soil amendment did not have much effect on soil internal friction angle in aeolian soil.(2)with increasing application rate of soil amendments, soil cohesion significantly increased, showing a positive relationship and good regression between cohesion and soil amendment application rate. (3) being the same in amendment application rate, the soils low in soil water content were higher than their corresponding ones high in soil water content in both cohesion and internal friction angle, but the difference was not significant(P>0.05), and the former was 21.02%, 24.69% and 11.57% higher in Treatments CMC, 10.3%, 19.05% and 13.59% higher in Treatments PG and 16.49%, 9.48% and 16.93% higher in Treatments BC. 【Conclusion】In summary, application of soil amendments can significantly improve soil cohesion, but does not have much effect on soil internal friction angle. In terms of soil coherence enhancing efficiency, the three kinds of soil amendments exhibit an order of carboxymethylcellulose sodium> phosphogypsum> biochar. All the findings in this study demonstrate that low soil water content is more conducive to improvement of shear strength of aeolian soil, by enhancing soil cohesion, together with application of soil amendments, thus stabilizing aeolian soil and improving ecological environment of the desert area. Among the three kinds of soil amendments, CMC is the most effective one.

    • PLSR-Based Prediction of Soil Color and Its Comparison with Color Space Conversion Method

      2018, 55(6):1411-1421. DOI: 10.11766/trxb201803300469

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      Abstract:The color of a soil may, to a certain extent, reflect degree in development, type and fertility of the soil. Traditionally, soil color is measured with the Munsell colorimetry, which, though quite high in accuracy is time-consuming and low in efficiency. It is, therefore, essential to explore for a quick and accurate method to measure soil colors. Nowadays remote sensing and proximal sensing methods can be used to obtain soil information, and numerous attempts have been made to extract soil color information from soil spectra. For that end, color space conversion (CSC) method is a commonly used one. It uses mathematical formulas to match colors between different coordinates, so as to realize prediction of soil colors. The first step of this method is to extract average reflectance values of the RGB bands from spectral reflectance and then converts them into XYZ values in the CIE XYZ coordinate, and further into HV/C values in the munsell coordinate. In this paper, a novel method was introduced to predict soil colors using partial least squares regression (PLSR) of hyperspectral reflectance of soils, and then comparison was made between PLSR and CSC in prediction accuracy. 【Method】A total of 76 soil samples different in colors were collected in the bordering area of Anhui, Jiangxi and Hubei Province for the study, covering soil types e.g. red soil (Argi-Udic Ferrosols), paddy soil (Fe-accumuli-Stagnic Anthrosols), yellow-brown soil (Ferri-Udic Argosols), fluvo-aquic soil (Ochri-Aquic Cambosols), purple soil (Dystric Purpli-Udic Cambosols) and yellow soil (Ali-Perudic Argosols) in the study area. After being air-dried, the soil samples were determined in color through color matching with the Munsell color system, and their spectral reflectance was acquired simultaneously with the aid of the ASD spectrometer. Then PLSR and CSC was applied separately to predict colors of the soil samples. 【Result】Results show that the PLSR model can be well used to predict soil Hue (H), Value (V), and Chroma (C) with cross validation coefficient Rcv2) being 0.62, 0.61 and 0.75 respectively, and RPD being 1.94, 1.67 and 2.15 respectively, which suggests that it is feasible to use the PLSR method to predict soil colors and that the mean square root error (RMSE) of H, V and C predicted with PLSR was only 1.32, 0.55 and 0.97 units, respectively, and 0.94, 1.24 and 0.95 lower than their respective ones predicted with the CSC method. The former, being 1.91, was 5.16 lower than the latter in mean ∆E, the mean HV/C comprehensive index. Analysis of reasons for that reveals that PLSR uses the spectral reflectance information of all the bands, while CSC makes use of mean reflectance of Red, Green and Blue bands only. Furthermore, certain errors inevitably occur in every step of the conversion of CSC.【Conclusion】Therefore, it could be concluded that the PLSR method is superior to the CSC method in predicting Munsell color of a soil. And compared the conventional soil color measuring methods, this one saves time and labor by a large mirgin. So this method opens up a new way for quick soil color acquisition via soil spectrum.

    • Effect of a Salt-tolerant Type of Water-retaining Polymer on Growth Characteristics of Maize in the Sand

      2018, 55(6):1422-1430. DOI: 10.11766/trxb201802120008

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      Abstract:【Objective】 Water and nutrients are essential elements plants need for growth. So it is very important to improve soil moisture regime and crop fertilizer utilization efficiency in agricultural production. The purpose of this study is to investigate effects of a home-made salt-tolerant water retaining polymer on leaching loss of potassium and growth of maize, and determine roles of the polymer in water retention and soil nutrient conservation in sand, in an attempt to provide certain technical support for application of the polymer in the arid area. 【Method】 In this study, a pot experiment was carried out using sand instead of soil to explore effects of the polymer on leaching of potassium fertilizer and growth of maize of two consecutive seasons. The part for leaching of potassium was designed to have four treatments, in terms of application rate of the polymer, i.e. 0 g·kg-1 (blank), 0.5 g·kg-1, 1.0 g·kg-1 and 2.0 g·kg-1, and the part for maize growth also had four treatments in terms of application rate of the polymer, too, i.e. 0 g·kg-1 (blank), 0.5 g·kg-1, 1.0 g·kg-1 and 1.5 g·kg-1. At the same time, all the treatments were subjected two levels of soil water content separately, that is normal and drought. The second crop of maize was planted after the harvest of the first in the normal group. Content of potassium in leachate from each pot was determined and plant height, stem diameter, dry weight, fresh weight, maximum leaf area and absorptive amount of N, P and K of the maize were measured. 【Result】 All the findings of the experiment demonstrate that the polymer helps reduce leaching loss of potassium fertilizer in sandy soil. Comparing with the control, the treatment amended with 0.5 g·kg-1 or 1.0 g·kg-1 polymer was 12.96% or 47.85%, respectively, lower in potassium leaching loss. In the treatment amended with 0.5 g·kg-1, 1.0 g·kg-1 and 1.5 g·kg-1, the crop survived 12 days, 19 days and 30 days longer, respectively, in the drought group, and the crop of the first harvest was 8.83%, 19.63% and 22.39%, respectively, higher in N absorptive amount, 29.31%, 30.19% and 52.38% higher in P absorptive amount and 11.61%, 18.12% and 20.72% in K absorptive amount, and the crop of the second harvest was 55.50%, 117.1% and 143.7%, higher in N absorptive amount, 77.12%, 161.3% and 156.5% higher in P absorptive amount and 55.42%, 74.13% and 84.33% higher in K absorptive amount, respectively. 【Conclusion】 All the findings in this experiment demonstrate that application of the home-made salt-tolerant water detaining polymers in arid and even desert areas could significantly reduce nutrient loss and improve soil water regime.

    • Livestock and Poultry Carrying Capacity of Land Based on Soil Nutrient Balance

      2018, 55(6):1431-1440. DOI: 10.11766/trxb201804090575

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      Abstract:【Objective】As livestock and poultry droppings are rich in nutrients, such as nitrogen, phosphorus, potassium, etc., they are often used as organic manure in farmland fertilization. However, excessive application of the organic manure may lead to accumulation of nitrogen and phosphorus in the soil and consequently leaching of N and P from the soil with rainfall into water bodies, causing serious pollution of surface water and groundwater. In order to rationalize the scale of livestock feeding, effectively reduce pollution from the livestock and poultry feeding industry in Xinhui District, Jiangmen City and ensure healthy and sustainable development of the industryc, it is necessary to study current status of soil N and P in the farmlands and figure out how much livestock and poultry manure the farmlands demand 【Method】 A total of 35 soil samples were collected from paddy fields, vegetable plots, orchards and forest lands, separately, for analysis of N, P, Cu, Zn and As contents with the standard methods. By referring to the “Standard for Grading of Soil Fertility” and “Standard of Soil Environment Quality for Farmlands”, evaluation was done of soil nutrients and heavy metals in the soil relative to soil type in Xinhui Region, Based on the data cited from the “Statistic Yearbook of Xinhui” concerning types, yields and planting areas of the major crops in the region, crop nutrient demand was calculated. Based on the soil test for N and P contents in combination with crop planting areas, soil nutrient supplying capacity was worked out. In the end, Study was performed of rational livestock and poultry feeding scales, using a nutrient balance model. 【Result】All the findings in this study indicate that the soils in Xinhui are quite high in fertility. Among the 35 sampling points, 29 or 82.9% exceeded 1.2 g•kg-1 in TN. The paddy soils were the highest in TN, reaching up to 2.92 g•kg-1, and the orchard soils were in TP, reaching up to 3.51 g•kg-1 in Gujing Town, where all towns, except for Daze Town, had soil N or P surplus, and some farmlands even did both. In addition, As pollution was found in some orchards, which might be attributed to the use of organic-arsenic pesticides in the past. Based on the nutrient balance model, livestock and poultry carrying capacity of Xinhui District was worked out to be 270 985 heads of pig equivalent. However, the current load of livestock and poultry has already reached as high as 1 257 295 heads of pig equivalent. Shuangshui and Siqian are the top two towns in, livestock and poultry carrying capacity, reaching 80 145 and 70 843 heads, respectively, the sum of which accounts for 55.7% of the total of the whole district. On the other hand, the following towns, Huicheng, Sanjiang and Daao, do not have any livestock and poultry carrying capacity. 【Conclusion】 Xinhui District is quite high in soil fertility. For the sake of environmental protection, it is essential to have the whole district adopt the practice of soil-test-based fertilization. Besides, to prevent and control of pollution from the livestock and poultry feeding industry in Xinhui, it is of paramount importance to limit the scale of livestock and poultry breeding and moreover to pay special attention to the risk of potential As pollution of the farmlands, while enlarging the proportion of organic manure in fertilization.

    • Effect of Microtopography on the Acidification Characteristics of Soils Developed from Purple Parent Rock

      2018, 55(6):1441-1449. DOI: 10.11766/trxb201804110614

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      Abstract:【Objective】 Purple soil is extensively distributed in Southwest China. To study acidification characteristics of the purple soil and its parent purple rock in the hilly areas of that region as affected by micro-topography, this study was launched. 【Method】In this study samples of two kinds of purple rocks and four types of purple soils were collected from the hilly area of Southwestern China for analysis of physicochemical properties in the lab. Samples of the two kinds of purple rocks, mudstone and sandstone, were collected at the top of hills and of the four types of purple soils, stony sub-soil, half sand half mud, bigeye mud and purple yellow mud, distributed in sequence along hill slopes from the top to the bottom, were done, respectively, too, 14 samples each. 【Result】 Acidification, to a varying extent, was found in the purple soils of that region. Consequently, in these soils the content of exchangeable acidity increased, and the content of total exchangeable base cation and the base saturation decreased. Purple soil development gradually increased in degree along hill slopes from the top to the bottom. The carbonate in the soils that helped keep soil pH in the range of 8 to 12 was subjected to leaching and the impact increased too along the slope from the top to the bottom. As a result, soil acidification was gradually extending in range along the slope. In terms of acidification degree, the four soils followed an order of purple yellow mud > bigeye mud > half sand half mud > tony sub-soil. In acidified purple soils, pH was controlled by cation exchange reaction, and affected by the degree of base cation (K+ , Na+ , Ca2+ and Mg2+ ) subjection to leaching and recovery, which varied with micro-topography. The stony sub-soils on the top of hills were exposed to leaching of base cations only, while the bigeye muds and half sand half muds on the mid slope were subjected to supplementation of base cations leached from the stony sub-soils on the top of the slope, besides leaching loss of base cations. The purple yellow muds, at the bottom of the hill or slope, highly weathered, were low in effective cation exchange capacity and hence the colloids in the soil adsorbed less H+ and Al3+ on the surface. Generally speaking, in terms of overall acidification degree, the four types of purple soils followed an order of stony sub-soil > half sand-half mud > bigeye mud > purple yellow mud. 【Conclusion】It can be concluded that as affected by micro-topography, acidification of the four types of soils increases gradually in range from the top to the bottom of the hill, but does not in degree. Therefore, it is essential to pay attention to the acidification characteristics of the purple soils of Southwest China in exploiting the soils.

    • Hofmeister Effect in Ion Adsorption Kinetics on Surface of Yellow Earth Particles

      2018, 55(6):1450-1459. DOI: 10.11766/trxb201802010577

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      Abstract:【Objective】A number of studies have reported that specific ion effects possibly exist universally in cation adsorption processes. In this study, based on the ion adsorption kinetics model that takes into account non-classical polarization of ions, adsorption kinetics of alkali metal ions on the surface of yellow earth particles (a surface with variable charges) was characterized. In addition, origins of the Hofmeister effects in the ion adsorption kinetics on surface of yellow earth particles were investigated. 【Method】 Kinetics of Li+, Na+ and Cs+ adsorptions in the K+ -saturated yellow soil was studied with the miscible displacement technique under a steady flow condition. In the flowing liquid Li+, Na+ and Cs+ was spiked at 1×10-2 mol?L-1, 1×10-3 mol?L-1 and 1×10-4 mol?L-1 respectively and pH adjusted to 4. 【Result】(1) Li+、Na+ and Cs+ varied sharply in adsorption rate and equilibrium adsorption capacity, when they were the same in concentration, which shows apparent ion specificity in the ions exchange process. The three metals exhibited an order of Cs+ > Na+ > Li+, in adsorption rate and equilibrium adsorption capacity, when in solutions low in electrolyte concentration (1×10-4 mol?L-1), and an order of Cs+ > Na+ ≈ Li+ when in solutions high in electrolyte concentration (1×10-2 mol?L-1 and 1×10-3 mol?L-1), which suggests that volume is a major factor affecting equilibrium adsorption capacity in solutions high in electrolyte concentration. (2) It was also found that d (thickness of the Stern layer) decreased with increasing electrolyte concentration in the same electrolyte system, exhibiting an order of dNa >dLi > dCs in solutions high in electrolyte concentration (1×10-2 mol?L-1 and 1×10-3 mol?L-1), and a different order ofdLi >dNa > dCs in solutions low in electrolyte concentration (1×10-4 mol?L-1). The Stern layer of Cs+ was the lowest in d, regardless of electrolyte concentration, and too thin for the more softer electric cloud of Cs+, thus possessing relatively stronger non-classical polarization than Na+ and Li+, but for Na+ and Li+, volume might play a dominant role affecting ion adsorption processes in solutions high in electrolyte concentration, and consequently dNa was found higher than dLi; otherwise the non-classical polarization would play a dominant role in solutions low in electrolyte concentration, weakening the volume effect, and reversing the order as dLi > dNa. Therefore diffusion distance and then equilibrium adsorption capacity is determined by volume effect and non-classical polarization. (3) The order of KdiffCs/H > KdiffNa/H > KdiffLi/H≈1 means that the sequence of Li+,Na+ and Cs+ in electric adsorption in the K+-saturated yellow soil is Cs+ > Na+ > Li+≈H+, and also demonstrates that volume does not have much effect on ion adsorption in the double diffusion layer. And in terms of surface potential (absolute value), the three metals follows an order Li+ > Na+ > Cs+ in solutions the same in concentration, indicating that the surface potential is only affected by non-classical polarization.【Conclusion】The interaction of ion-surface is determined by ion non-classical polarization and ion volume effect.

    • Structure and Cu(II) Adsorption of Soil Humin

      2018, 55(6):1460-1471. DOI: 10.11766/trxb201802010532

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      Abstract:【Objective】The knowledge about chemical composition and interactions of humic substances with metal ions in the soil is of paramount importance to elucidating behaviors and fates of trace metals in the environments. Adsorption is one of the most important interactions between humic substances and metal ions. Among the three fractions of humic substances, i.e., humic acid, fulvic acid and humin, the last is the least studied because of its hard-to-dissolve nature. So far, it is still unclear how humin adsorbs metal ions and its mechanism. 【Method】In this study, humin was extracted from two zonal soils of East China, i.e., brown soil (Argosol) and lateritic red soil (Ferrosol), with 0.1 mol•L-1 NaOH+0.1 mol•L-1 Na4P2O7 extraction, treated with 10% (v/v) HF-HCl and then prepared into samples for analysis. Structure of the humin was characterized with elemental analysis, solid-state carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques. On such a basis, the batch equilibrium method was used to study adsorption of Cu(II) on humin as a function of exposure duration, adsorbate concentration and reaction temperatures. Local chemical structure of the Cu(II) adsorbed onto the humin was explored with the synchrotron-based X-ray absorption near edge structure (XANES) spectrum and the extended X-ray absorption fine structure (EXAFS) spectrum. Furthermore, comparison was also made between humin and humic acid in chemical compositions and Cu(II) adsorption feature. 【Result】Compared with humic acid, humin is relatively higher in content of C, H, alkyl C, carbohydrate C, di-O-alkyl C, polysaccharides and fatty acids, but lower in content of N, S, O, methoxyl C, aryl C, phenol C, carbonyl C, lignin, phenols and nitrogen-containing compounds. With rising duration of exposure, Cu(II) concentration, and reaction temperature, Cu(II) adsorption on humin increased, too. Kinetics of the adsorption could be best described by pseudo-second order equation with equilibrium achieved in approximately 120 min, and isotherm of the adsorption well fitted the Freundlich and Langmuir equations. The adsorption activation parameters, i.e., activation free energy (ΔG#), activation enthalpy (ΔH#) and activation entropy (ΔS#), indicate that the process of adsorption is an association reaction that requires energy and absorbs heat. Moreover, the low activation energy (Ea) (less than 26 kJ•mol-1) implies that the adsorption reaction is controlled by boundary layer diffusion and Cu(II) was physically adsorbed onto the surface of humin. The adsorption thermodynamic parameters, i.e., standard Gibbs energy (ΔGº), standard enthalpy change (ΔHº) and standard entropy change (ΔSº), indicate that the adsorption reaction is a spontaneous, endothermic process with increasing freedom of motion. Similar to humic acid, humin has Cu(II) adsorbed on the surface in the form of a twisted octahedron, with the first coordination sphere consisting of 4 O atoms 1.91~1.97 Å apart and the second coordination sphere consisting of 2 C atoms 2.80~2.83 Å apart, which demonstrates that Cu(II) is preferentially adsorbed onto the organic functional groups on the surface of humin in the form of inner-sphere compound.【Conclusion】 All the findings demonstrate that humin differs from humic acid in chemical composition. Humin is relatively higher in aliphaticity and polarity. However, the Cu(II)s adsorbed on the surface of the two fractions of humic substances have similar local chemical structure.

    • Effects of Application of Coated Diammonium Phosphate in Combination with Fulvic Acid Improving Wheat Yield and Soil Nutrient Supply Intensity

      2018, 55(6):1472-1484. DOI: 10.11766/trxb201803200089

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      Abstract:【Objective】 Phosphorus is one of the most important nutrients for plant growth, and increasing application of P fertilizer has been an effective way to improve crop yield. However, plant available phosphorus is always relatively low in soil, because more often than not a large portion of phosphorus is bound to or reacted with iron and aluminum oxides/hydroxides. To solve the problem, one option is to insulate phosphate from soil by coating phosphorus fertilizer with polymer material. Fulvic acid (FA) is considered to be an effective conditioner for better phosphorus use efficiency, because owing to its specific physicochemical properties, it is ready to get complexed with metal ion, which in turn releases desorbed phosphorus in soil. However, so far little has been reported on coating diammonium phosphate and applying FA as its amendment. This paper addresses effects of coated diammonium phosphate (CP) in combination with lignin-based FA on wheat (Triticum aestivum L.) yield and soil nutrient supply intensity, in an attempt to provide a scientific basis for proper usage of P fertilizer. 【Method】 A pot experiment was carried out to explore effects of combined application of CP and FA on wheat yield, yield composition, chlorophyll content, plant height, SPAD, soil pH, and phosphorus use efficiency. The experiment was designed to have eight treatments, i.e. Treatment P (application of diammonium phosphate (DP) at 150 kg hm-2 P2O5), Treatment P80% (application of DP at 120 kg hm-2 P2O5, 80% of the rate of Treatment P), Treatment CP (application of coated DP at 150 kg hm-2 P2O5), Treatment CP80% (application of coated DP at 120 kg hm-2 P2O5, 80% of the rate of Treatment CP), Treatment P+FA (application of DP at 150 kg hm-2 P2O5 plus FA) , Treatment P80%+FA (application of DP at 120 kg hm-2 P2O5 plus FA), Treatment CP+FA (application of coated DP at 150 kg hm-2 P2O5 plus FA), and Treatment CP80%+FA (application of coated DP at 120 kg hm-2 P2O5 plus FA), of which the first two were set as control. 【Result】 Results show that wheat yields in treatments P+FA, CP and CP+FA increased significantly by 7.7%, 5.1% and 24.0%, phosphorus use efficiency by 9.14%, 9.74% and 17.00%, respectively, and economic benefit by 6.3%,1.1% and 22.5%, respectively, as compared Treatment P, whereas wheat yield in P80%+FA, CP80% and CP80%+FA increased by 10.6%, 7.2% and 4.8%, and phosphorus use efficiency by 19.88%, 18.53% and 11.54% as compared with Treatment P80%. However, economic benefit increased by 8.9% and 10.5% in Treatment P80%+ FA and Treatment CP, but decreased by 1.10% in Treatment CP+FA. Both of CP and FA improved soil available phosphorus during the whole wheat growth period. At the seedling stage when phosphorus was critical to wheat, soil available phosphorus increased by 16.9%~24.0% and 21.6%~40.1% in Treatments of P+FA and CP+FA and by 15.0% in Treatment CP as compared with Treatment P, whereas it increased by 8.7%, 26.1% and 23.7%, respectively, in Treatments P80%+FA. CP80% and CP80%+FA as compared with Treatment P80%. 【Conclusion】All the findings in this experiment demonstrate that application of CP in combination with FA as basal could significantly raise soil available phosphorus supply intensity at the critical period of wheat, and consequently improve wheat yield, phosphorus use efficiency and economic benefit as a result of their synergistic interaction. This practice has a great potential for large-scale extension to satisfy the increasing demand for controlled-release fertilizers because it is cost-effective and environmentally friendly. However, due to certain limitation of the pot experiment, a long-term field experiment and further studies should be done to explore synergistic interaction and mechanism of the application of CP and FA increasing yield and phosphorus use efficiency.

    • Effects of Change in Forest Type on Soil Organic Carbon in Soil Particles Relative to Size in Subtropical China

      2018, 55(6):1485-1493. DOI: 10.11766/trxb201803140028

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      Abstract:【Objective】Any changes, even minor ones, in forest soil carbon pool would have profound effects on atmospheric CO2 concentration and global climate change. Particulate organic carbon is mainly of semi-decomposed plant residues and very high in biological activity and short in turnover cycle, so it can be used as an indicator of changes in soil organic carbon. Change in forest type or forest conversion is an important pattern of changes in land use, and affects storage and transformation of soil organic carbon through increasing or reducing biomass of the plants and litter on the ground. So, it is an important driving force of soil organic carbon (SOC) dynamics. This paper focused on conversion of natural broad-leaved forest to mixed coniferous-broad-leaved forest or Chinese fir plantations (Cunninghamia lanceolata [Lamb.] Hook) in subtropical China to explore effects of the conversion on content of SOC and its distribution in the forestland. Therefore, three tracts of forests were selected as subjects of the study, i.e. a 28-year-old natural broad-leaved forest, a Chinese fir plantation and an artificial mixed coniferous broad-leaved forest converted from natural broad-leaved forest in November 2016. 【Method】Soil samples were collected from different soil layers (0~20 cm, 20~40 cm, and 40~60 cm) in the forestlands for analysis of effects of the conversion on contents of soil coarse particulate organic carbon (CPOC), soil fine particulate organic carbon (FPOC), and mineral-associated organic carbon (MOC) and their ratio.【Result】Results show that once natural forest was converted into artificial ones, (1) content of soil organic carbon in various soil layers and stock of litter on the surface decreased significantly; (2) CPOC decreased in content by 60.0% and 54.6% in the mixed coniferous broad-leaved forest and Chinese fir plantation, respectively and in proportion, too in the 0~20 cm soil layer, while FPOC did reversely in both content and proportion; however, MOC declined in content, but rose in proportion, by 8.6% and 20.1%, respectively; and (3) The soil POC/MOC and MOC/SOC ratios in all the soil layers exhibited decreasing trends. In the 0~20 cm soil layer, soil CPOC was the most closely related to SOC, whereas in the 40~60 cm soil layer, MOC was.【Conclusion】Therefore, the conversion of subtropical natural broad-leaved forests into coniferous-broad-leaved mixed forests and Chinese fir plantations reduces soil total organic carbon (SOC) as the latters produce less litter and fine root biomass, thus leaving the soils more susceptible to soil erosion caused by rainfall, which in turn enhances reduction of total SOC, and POC/SOC and POC/MOC in all soil layers to a varying extent, However, it improves stability of SOC. Soil CPOC is a better indicator reflecting the effect of forest conversion on topsoil organic carbon, while MOC is, reflecting the impact of forest conversion on deep soil organic carbon.

    • Characteristics of the Fraction of Organic Nitrogen in Fluvo-aquic Soil Aggregates under Long-term Application of Chemical Fertilizer and Organic Manure

      2018, 55(6):1494-1501. DOI: 10.11766/trxb201803010605

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      Abstract:【Objective】 The objective of this research was to investigate effects of long-term fertilization on formation of soil aggregates and the fraction of soil organic nitrogen therein in fluvo-aquic soil in the North China Plain, and consequently nitrogen supplying capacity of the soil and its mechanism.【Method】 Undisturbed soil samples were collected from the four treatments, i.e. CK (no fertilization), NPK (Application of chemical fertilizers only), 1/2OM (Application of half the rate of chemical fertilizer in Treatment NPK and half of the rate of organic manure in Treatment OM) and OM (Application of organic manure only) of the long-term (27 years) fertilization experiment at the State Agro-Ecological Experimental Station in Fengqiu, for analysis of contents of mechanically-stable soil aggregates and organic nitrogen therein, with the dry-sieving method and the Bremner method, separately. 【Result】 Results show that application of organic compost increased the proportion of > 2 mm aggregates in the topsoil, significantly or by 33% and 17% as compared with CK and NPK, whereas it decreased the content of <0.25 mm aggregates. Long-term fertilization significantly increased the content of organic nitrogen in aggregates in the fluvo-aquic soil, especially Treatment OM. The content of organic nitrogen in aggregates >2 mm, 2~0.25 mm and <0.25 mm was 776.4 mg·kg-1, 837.7 mg·kg-1 and 625.3 mg·kg-1, respectively. The organic nitrogen in soil aggregates was dominated with acidolyzable ammonium N, which was followed by amino acid nitrogen and unknown-acidolyzable nitrogen, aminosaccharide nitrogen, the least. Treatment NPK increased the proportion of acidolyzable nitrogen in > 2mm aggregates, while Treatment OM did the content and proportion of amino acid nitrogen and unknown acidolyzable nitrogen. 【Conclusion】 long-term application of organic manure can improve the soil structure of fluvo-aquic soil significantly, and stimulate accumulation of total nitrogen and all fractions of organic nitrogen, with amino acid nitrogen, amico sugar nitrogen and non-acidolyzable organic nitrogen accumulated mainly in 2~0.25 mm, and acidolyzable and unknown acidolyzable nitrogen in >2 mm aggregates, thus significantly increasing nitrogen supplying capacity of the soil.

    • Spatial and Temporal Distribution of Bioavailable Phosphorus in the Subalpine Soil on the Eastern Slope of Gongga Mountain

      2018, 55(6):1502-1512. DOI: 10.11766/trxb201803290567

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      Abstract:【Objective】 Phosphorus (P) is an important nutrient for plants. Enough supply of bioavailable P is essential for maintaining the stability of montane ecosystems. Many previous studies have focused on distribution and main driving factors of soil bioavailable P. However, there still are disputes about the synergistic effects of soil parent material, soil age, climate, biological activity, and soil properties on the bioavailable P distribution. The large altitudinal difference of high mountains provides an opportunity for determining the dominant factors and their interactions on the bioavailable P distribution in natural ecosystems. Therefore, the objectives of this study were to investigate the distribution of bioavailable P in profiles along the altitudinal gradient and to clarify the factors impacting the spatial and temporal distribution of bioavailable P in subalpine soils. 【Method】 Four altitudes (2 628 m, 2 781 m, 3 044 m and 3 210 m a.s.l.) were selected for sampling in May 2016. Six soil profiles were randomly set up for each site with a distance larger than 10 m between them. Soil profiles were divided into the four horizons O, A, B and C. One- to two-kilogram soil samples were collected hierarchically from the C to the O horizon. After soil samples were collected, mixed-bed ion-exchange resins bags were inserted into the four horizons (profiles 1~4) at each site. Soil samples were assayed to estimate the content of bioavailable P (Bio-PL). Bio-PL was defined as the inorganic P extracted using 0.5 mol•L-1 NaHCO3 (pH = 8.5) followed by colorimetric analysis with a UV2450 (Shimadzu, Japan). Resin bags were recovered to analyze the soil supply of bioavailable P (Bio-PS). Bio-PS was estimated by PO43--P concentrations using an Autoanalyzer 3 (Seal Analytical, Germany). 【Result】 The concentrations and stocks of Bio-PL as well as Bio-PS increased with altitude. The leaching process was more intensified in lower altitudes. This altitudinal pattern of bioavailable P was likely related to a lager loss of bioavailable P in lower altitudes (especially at the 2 781 m site) as shown by increasing soil moisture downward. The concentrations and stocks of Bio-PL decreased with soil depth. The stock of Bio-PL in the O horizon accounted for the largest proportion of the total Bio-PL stock, with an average of 75%. The Bio-PS in the O horizon was larger than 0 mg•kg-1•d-1 in the whole year. Thus, most soil bioavailable P was stored in the O horizon. The higher organic P content and phosphatase activity in the O horizon were the most important factors for this vertical distribution of bioavailable P in soil profiles. Bio-PS in the O horizon at the 2 781 m site was higher in September. For both of the 3 044 m and 3 210 m site, Bio-PS in the O horizon were higher in June and September. Bio-PS in the mineral horizons at the four sites was smaller than 0 mg•kg-1•d-1 in most months. The minimum Bio-PS for both A and B horizon were in August at the 2 781 m site, which were -1.143 and -0.943 mg•kg-1•d-1, respectively. Biological assimilation and loss with runoff were the main factors controlling the seasonal changes of soil bioavailable P. 【Conclusion】 Bioavailable P in the subalpine soil on the eastern slope of Gongga Mountain showed obvious spatial and temporal variations. The content of bioavailable P increased with altitude, and this altitudinal pattern was likely caused by a larger amount of loss in lower altitudes. Soil P bioavailability was highest in September for the O horizon and lowest in August for the mineral horizons. The seasonal change of soil bioavailable P was mainly controlled by the biological assimilation and loss with runoff.

    • Movement and Leaching of Magnesium Fertilizers in Three Types of Magnesium-deficient Soils in South China Relative to Fertilizer Type

      2018, 55(6):1513-1524. DOI: 10.11766/trxb201802130616

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      Abstract:【Objective】Magnesium (Mg) is a mineral nutrient essential to plant growth. It is the central atom of chlorophyll, and also an activator of various enzymes, involved in various metabolic reactions in plants. Magnesium deficiency can affect normal growth and yield quality of the crops involved. Nevertheless it has become more and more a common problem in the soil-crop systems in South China, in the last decades, where though large volumes of chemical fertilizers are applied, little magnesium fertilizers are, and the removal of magnesium by crop and soil Mg leaching is high. Mg leaching in the soil is one of the primary factors leading to Mg deficiency in the soil and crops in the tropical and subtropical regions of China with high temperature and plentiful rainfall. To solve the problem, application of magnesium fertilizer has become an important strategy. Therefore, it is of great importance to explore characteristics of Mg movement and leaching in Mg deficient soils as affected by Mg fertilizer application for rationalizing application of Mg fertilizers.【Method】An indoor soil column simulation experiment was conducted to study movement and leaching of Mg in the three types of acid Mg-deficient soils (red soil, yellow soil and purple soil common in South China), applied with magnesium oxide (MgO), improved magnesium sulfate (Improved MgSO4, pH>8), calcium magnesium phosphate fertilizer (CaMgP) and potassium sulphate magnesium (KMgS), separately, and consequently efficiency of the fertilizers. This study is expected to be able to provide certain technical support for rationalization of the application of Mg fertilizers in the soils typical of South China. 【Result】Results show that soil exchangeable Mg increased by 2~15 folds in all the three types of soils (0~15 cm) after application of the Mg fertilizers at a rate of MgO 100 mg·kg-1 . Among the four types of Mg fertilizers, Improved MgSO4 was the highest in the effect and followed by CaMgP, MgO and KMgS, sequently. After 60-days of leaching with simulated rainfall amounting to 1000 mm, strong downwards movements of soil Mg in the soils applied with MgO, improved MgSO4 or KMgS fertilizer were observed. Compared with the soils with no Mg applied (CKs), the soils applied with Mg fertilizer had soil exchangeable Mg increased in concentration significantly or by a range of 17.9~105.4 mg·kg-1 in the 15~50 cm soil layer as a result of leaching of Mg from the top layer (0~15 cm). The effect was significant in the yellow soil and red soil applied with CaMgP, but not in the purple soil. In general, Mg concentration in leachate displayed a trend, increasing first and then decreasing, which could be well described with a quadratic equation. Accordingly, the amount of leached Mg from the soils under different Mg treatments could be well matched by exponential equations. The accumulated Mg leaching from the yellow soil varied in the range of 104.9~243.8 kg·hm-2 , which was close to that from the purple soil, and 2~3 times higher than that from the red soil. Compared with CKs, application of MgO, improved MgSO4 or KMgS fertilizer significantly increased the amount of Mg leaching in the yellow soil and purple soil, while application of CaMgP fertilizer did reversely. After the leaching experiment, the leaching rates of the MgO, improved MgSO4 and KMgS fertilizers applied in the yellow soil and purple soil were all higher than one-third, whereas lower than 7% in the red soil. On the other side, application of CaMgP enhanced retention of Mg in the soils, and slowed down the downwards movement of Mg, thus reducing Mg leaching during the leaching experiment period as compared with CK. 【Conclusion】By considering integratedly the effects of the four types of magnesium fertilizers on availability, retention and leaching of Mg in the soil and retardation of soil acidification, CaMgP fertilizer is preferred for all the three types of acid soils typical of South China, although its biological availability needs to be studied further.

    • Effect of Soil Amelioration on Soil Nutrients at Mining Dumps in the Shanxi-Shaanxi-Inner Mongolia Region

      2018, 55(6):1525-1533. DOI: 10.11766/trxb201802000037

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      Abstract:【Objective】The Shanxi-Shaanxi-Inner Mongolia region is an energy base in China, massive opencast mining activities in the region bring about a series of environmental and ecological problems. In this case, reconstruction of disturbed surface ecosystems and reclamation of dumps have become the upmost urgent tasks in eco-environment rehabilitation of the region. The soil in the region is dominated with sandy loess soil, and some feldspathic sandstone and weathered coal. Studies have shown that feldspathic sandstone can be used to improve soil properties of sandy loess, and weathered coal, too, as soil amendment. However, effects of using feldspathic sandstone and weathered coal as soil amendment to improve soil properties and fertility of reconstructed soil are rarely reported. To reconstruct the soil of the dump of the Yongli Coal Mine, this study was oriented to explore effects of different soil amelioration modes on soil nutrients in the soil of the dump so as to accumulate certain theoretical and practical experience in reclaiming deserted dumps and restoration of the ecosystems therein 【Method】In this study, three types of reconstructed and artificially aged soils, different in structure and nutrient state, i.e. FS (Feldspathic sandstone mixed with sandy loess soil), WC (Weathered coal mixed with sandy loess soil), and SL (Sandy loess soil), were selected for comparison with the soil under original landform grown mainly with Stipa bungeana (OL, Original landform soil) and a new dump (CK, Blank control). So there were 5 treatments and 3 replicates for each treatment. After three years of artificially aging through fertilization and plant cultivation, soil samples were collected from the five treatments for analysis of soil organic carbon, total nitrogen, nitrate nitrogen, ammonium nitrogen and available phosphorus in the 0~20 cm surface soil. Comparison was made for differences in nutrient status and the weighted synthesis method was used to evaluate the nutrient quality of several soil types.【Result】 Results show that: 1) SOC in the reconstructed soils (FS, WC and SL) and the original landform soil (OL) was 12.2, 10.0, 5.1 and 4.9 times respectively as high as that in the new dump in the 10~20 cm layer soil. Soil total nitrogen in OL was the highest among the five treatments. TN in the 0~10 cm layer in the three reconstructed soils was about 5 times as high as that in the new dump, while TN in the 10~20 cm soil layer, about 3 times as high. Nitrate nitrogen in the 0~10 cm soil layer soil was the highest in SL, reaching up to 3.61 mg·kg-1. Ammonium nitrogen in the 0~20 cm soil layer varied randomly, showing no consistent tendency among the treatments. Available phosphorus in the 0~10 cm and 10~20 cm soil layers was 0.36 mg·kg-1 and 0.9 mg·kg-1, respectively, lower in OL than in CK. 2) Soils under three different amelioration modes were obviously higher than OL in content of soil organic carbon, available phosphorus and nitrate nitrogen, and almost as high as OL in content of soil ammonium nitrogen, but still lower than OL in content of soil total nitrogen. 3) The soil quality index in 0~10 cm soil layer was 0.16~0.79 while range from 0.16 to 0.55 in 10~20 cm soil layer, and the soil quality index among five soil types shows WC>FS>SL>OL>CK.【Conclusion】All the findings in the experiment demonstrate that the soil amelioration mode of mixing weathered coal has the highest soil nutrient quality, followed by the mode of mixing fieldspathic sandstone, and the soil nutrient quality of sandy loess soil is higher than the original landform soil, while the quality of the blank control is the worst, showing three amelioration modes all have some positive effects on soil nutrients. The findings may serve as indices for evaluating soil fertility and as theoretical basis for constructing high-efficient artificial soils, and also provide reasonable suggestions for land reclamation and ecological restoration in mine dumps.

    • Impacts of Nitrogen Deposition on Soil Microbial Community Structure in Subtropical Natural Evergreen Broad-leaved Forest Relative to Season

      2018, 55(6):1534-1544. DOI: 10.11766/trxb201804210081

      Abstract (2061) HTML (807) PDF 1.69 M (2513) Comment (0) Favorites

      Abstract:【Objective】Soil microbes are the drivers of material circulation and energy flow in ecosystems, and their community structures may be used to characterize responses of soil ecological processes to environmental changes. This study was conducted in a natural Altingia gracilipes forest in the subtropical area and lasted for two consecutive years. This study was oriented to explore impacts of nitrogen (N) deposition on the dynamics of soil microbes, 【Method】 An in-situ N deposition simulation experiment was designed to have three treatments, i.e. CK (0 kg·hm-2·a-1), LN (50 kg·hm-2·a-1) and HN (100 kg· hm-2·a-1) in N deposition level, was carried out in 2010—2011, and the technique of phospholipid fatty acids (PLFAs) was used to explore diversity and composition of the soil microbial community.【Result】Results show that the soil microbial community in the forest consisted mainly of bacteria, gram-positive bacteria, gram-negative bacteria, fungi and actinomycetes. Among them, bacteria were the dominant fraction, contributing 78.3% to the total microbial PLFAs content. Significant differences were found between treatments and seasons in soil microbial community structure. Treatment LN had its soil microbial community structure altered significantly only in summer, when increased abundances were observed of bacterial, Gram-positive, Gram-negative and fungal residual PLFA markers but not i17:0, a17:0, 18:1ω7c, and 18:1ω7t markers. Treatment HN varied with the season, too, in soil microbial community structure. Decreased abundances of 16:1ω7c, 16:1ω7t, 18:1ω7t, and cy17:0 markers were found in spring, and of 18:1ω9 and 18:2ω6,9c markers in winter. In addition, no significant change was found in ratio of fungi to bacteria and of Gram-positive bacteria to Gram-negative bacteria in either Treatment LN or HN, but a significant one was in content of special fatty acids, such as cyclopropane fatty acid or isomeric fatty acid. Treatment LN increased the ratio of cyclopropane fatty acids to Precursor fatty acids all the year around, and also the ratio of isomeric fatty acids to anti-isomeric fatty acids in winter and spring, while Treatment HN increased the ratio of isomeric fatty acids to anti isomeric fatty acids in summer and autumn, but did not affect much the ratio of cyclopropane fatty acids to Precursor fatty acids throughout the entire experimental period. So the effects of N deposition on soil microorganisms do vary with seasons. Therefore, it is necessary to take season into consideration when the impacts of N deposition on soil microbial community structure in the subtropical forest ecosystem are studied. 【Conclusion】All the findings in this experiment demonstrate that short-term N deposition changes the soil microbial community structure, but not the ability of the soil microorganisms responding to environmental changes. Soil microbes respond to short-term N deposition through changing the content of special fatty acids, however, the response varies with the season. Comprehensive analysis shows that the change in soil microbial community structure is not only affected by soil substrate availability, but also soil temperature, moisture and other environmental factors that varies with the season. So they may serve as important factors affecting changes in soil microbial community structure in the subtropical evergreen broad-leaved forest. All the findings in this study may serve as reference for exploration of the mechanism of soil microbes affecting soil nutrient cycling in the subtropical natural forest as affected by nitrogen deposition in future. As the experiment was quite short in time, it is quite possible for soil microorganisms to get adapted to long-term nitrogen deposition. Therefore, in the context of steady increase of nitrogen deposition in the future, a long-term field experiment on nitrogen deposition should be carried out using high-resolution molecular biology methods, for better understanding of the mechanisms of soil microorganisms responding and adapting to nitrogen deposition in subtropical forest ecosystems.

    • >Research Notes
    • Characteristics of Soil pH Variation in Typical Red Soil Region of South China in the Past 25 Years —A Case Study of Yujiang County, Jiangxi Province

      2018, 55(6):1545-1553. DOI: 10.11766/trxb201804230159

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      Abstract:Recent years have witnessed less attention paid on soil acidification in the red soil region of Southern China, though it remains to be one of the main problems in the red soil ecosystem. So it is of great significance to explore temporal-spatial variability of soil pH in designing reasonable measures for agriculture and environmental management in the region. Analysis was done of the data of soil sampling in Yujiang in 1982 and 2007 for spatio-temporal distribution and variation of soil pH in the region during the two sampling periods and trend of the variation in the past 25 years. Results showed that the soil pH in Yujiang County has been obviously declining since the 2nd National Soil Survey. It declined from 5.66 in 1982 to 4.74 in 2007. Among the main types of soils that Yujiang has, fluvo-aquic soil dropped the most or by 1.02 in soil pH, and was followed quite closely by paddy soil and red soil, which did by 0.89 and 0.88 respectively. Among the main land use patterns, paddy field and upland field declined by 1.00, 0.92 and 0.82, respectively. Among the regions of the county, most declined sharply, especially parts in the central-northern and southwestern regions, which accounted for 68.13% and 84.54% of the total land area of Yujiang County, respectively. Compared with 1982, 2007 saw soil pH in the two parts dropping by 0.4~0.8 and 0.8~1.2, separately. Furthermore, the county was dominated by weakly-acid soil in 1982, while about 13.0% of the county’s soil turned to be strongly-acid in 2007, with the remaining being nearly the same, that is, strongly-acid. All the findings in this study indicate that the soil in Yujiang county, regardless of soil types and land use patterns, declined in pH by a large margin in the 25 years from 1982 to 2007. So the situation of soil acidification is very serious in the county, calling urgently for effective remediation measures.

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