• Volume 50,Issue 2,2013 Table of Contents
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    • Mechanisms of Bacterial Pathogens Adsorption on Red Soil Colloids

      2013, 50(2):221-229. DOI: 10.11766/trxb201206210246

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      Abstract:Effects of soil pH and ionic strength (KCl) on adsorption of Streptococcus suis and Escherichia coli on Red soil colloids were studied, and mechanisms of their interactions analyzed from the aspects of surface physicochemical properties of the bacteria and soil colloids and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Results show that the adsorption isotherms of bacteria on Red soil colloids fitted well to the Freundlich equation (R2> 0.97). The partition coefficients (Kf) of S. suis adsorption on soil colloids were 4.5~6.1 times as high as those of E. coli. The Kf values of organic-matter-depleted colloids were 2.4~3.2 times as high as those of organic-matter-containing colloids. The bigger the specific surface areas or the lower the absolute zeta potential values, the higher the bacteria adsorption capacity, and the adsorbed bacteria were found at the secondary minimum, 90~100 nm apart from the colloids surface. With decreasing solution pH (9.0~4.0) or increasing IS (1~10 mmol L-1), the interaction energy barrier between the Red soil colloids and the bacteria decreased and as a result more and more bacteria got adsorbed. This trend was in full agreement with the DLVO theory. The adsorption of S. suis on colloids decreased by 3.4%~5.6% under high IS (50~100 mmol L-1), which, besides the DLVO effect, was also ascribed to some non-DLVO effects, like steric repulsion and hydrophobic interaction.

    • Effect of dissolvable fulvic acid on transport of polycyclic aromatic hydrocarbons in soil

      2013, 50(2):230-236. DOI: 10.11766/trxb201205200184

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      Abstract:Batch experiment was performed to study effects of different aquatic factors (pH and iron intensity) on dispersibility of dissolved organic matter (DOM) extracted from Fulvic acid. It was found that the DOM extracted from fulvic acid (FDOM) remained high in dispersibility and did not precipate in solutions with pH between 2.0~7.0 and CaCl2 concentration between 0~1 500 mmol L-1 without precipitation. Column leaching experiments were conducted to investigate effect of FDOM on transport of polycyclic aromatic hydrocarbons (PAHs) in the soil. With continuous irrigation of FDOM, the concentrations of Phenanthrene (Phe), Pyrene (Pyr), and Benzo[a]pyrene (B[a]P) in leachate were significantly increased, and even a limited amount of Dibenzo (a, h) acenaphthene (DBA) was also detected in the leachate. After leaching, the leaching lost rate of Phe, Pyr, B[a]P and DBA in the surface soil was 92.06%, 92.07%, 84.52% and 23.27%, respectively. These findings indicated that FDOM could act as carrier facilitating PAHs transport in the soil, thus enhancing the possibility of PAHs moving deeper into the soil and ground water.

    • Adsorption and transformaton of cyanogen in soil

      2013, 50(2):237-243. DOI: 10.11766/trxb201207190289

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      Abstract:Cyanogen (C2N2) is a new type of fumigant that has the potential to replace methyl bromide. So it is of important significance to ascertain the behaviour of C2N2 in adsorption and transformation in soil for its safety application. Adsorption and transformation of C2N2 in soil was investigated using the static method under controlled conditions. C2N2 adsorption rates in soil was related with physicochemical properties of the soil, and slightly related with the ambient temperature, the soil water content and soil organisms, but not related with the application rate of the fumigant. C2N2 adsorption rate and its possible transformation products (HCN, NH4+, NO3-and NO2-) were determined using the gas chromatography (GC) coupled with a nitrogen-phosphorus detector (NPD) and the flow injection analyzer (FIA) with a Photometric detector. Results show that the soil had a very high C2N2 adsorption capacity with a rate being over 75% within 2 h of fumigation and over 98% within 24 h. The absorbed C2N2 could be quickly transformed, about 13% into HCN, and 20% into NH4+ and NO3-. No NO2-was detected within 48 h. HCN in soil was not stable and could be further transformed into other nitrogenous compounds.

    • Relationship between soil-developing indicators and climate factors and reconstruction of paleoclimate in the Western area, Liaoning Province

      2013, 50(2):244-252. DOI: 10.11766/trxb201204160135

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      Abstract:Through analysis of the soil development indices of 22 soil profiles developed under the modern climatic conditions of China and then correlation analysis, transfer functions were established between soil development indices and climate factors and used in reconstructuring paleoclimatic parameters of the paleosol profiles in the Fenghuang Mountain of Chaoyang, Liaoning Province. The following paleoclimatic parameters of the past 71 ~ 423 ka BP were obtained, including the mean annual precipitation being 523.92~574.42mm and the mean annual temperature being 10.6~11.0℃in 403 ~ 423 ka BP; 1184.6~1277.2mm and 15.6~16.6℃ in 311 ~ 403 ka BP; 517.24~669.08mm and 9.18~12.2℃ in 243 ~ 311ka BP; 1302.7mm and 16.5℃in 225 ~ 243 ka BP; 642.54~731.42mm and 10.1~11.6℃in 208 ~ 225 ka BP; 1231.4mm and 16.0℃in 176 ~ 208ka BP; 640.49~682.09mm and 8.49~9.13℃in 148 ~ 176ka BP; and 1128.2~1294.0mm and 16.1~16.6℃in 71 ~ 148ka BP. Now the mean annual temperature is 9℃ and the mean annual precipitation 450~500mm in Chaoyang, Liaoning, which indicates that although the climate of this area fluctuated greatly several times in the past 420,000 years, a general tendency is clear that the climate in that region is evolving from warm and humid to cold and arid.

    • Rock weathering and soil formation rates of a forested watershed in the typical subtropical granite area

      2013, 50(2):253-259. DOI: 10.11766/trxb201204120128

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      Abstract:Rock weathering and soil formation are important links of element cycling in the earth surface. The knowledge of rock weathering and soil formation rates is important for sustainable utilization of soil resources and watershed management. A typical forest watershed, located in South Anhui, subtropical China, was chosen as a case for study. Input and output of main mineral elements were monitored. Rock weathering and soil formation rates were estimated using the principles of geochemical mass balance of the elements in the watershed. Results show that with the current rainfall and acid precipitation, the average granite weathering rate is 0.696 t hm-2 a-1 and the soil formation rate is 0.598 t hm-2 a-1. That is to say, it takes more than 20 000 years to form 1 meter of soil in this area. It was found that a large amount of H+ was sunk into the ecosystem, but did not make stream water acidic because it was exhausted by soil mineral weathering and cation exchange. However, in the long run, it will acidify the soil. The research also found that it is necessary to re-set criteria of soil loss tolerance on the basis of the current soil formation rate.

    • Referencing between CSGC and CST and CST soil mapping in Zhejiang Province

      2013, 50(2):260-267. DOI: 10.11766/trxb201205240199

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      Abstract:Based on the newly established 1:50 000 soil database of Zhejiang Province, attempts were made to set up associations between soil species in the Genetic Soil Classification of China (GSCC) and soil subgroups in the Chinese Soil Taxonomy (CST) by referencing, and develop a CST soil subgroup distribution map. Results show that at the basic taxon level of GSCC, the referencing relationship was relatively clear, but at higher levels, the relationship got complicated. There were a total of 99 soil genus and 277 soil species in GSCC, among which, 62 genus and 252 species can be uniquely associated with soil subgroup in CST. So it is feasible to transform the large-scaled soil data yielded through the Second National Soil Survey using GSCC into CST, which can meet the requirements for plotting a 1:100 000 scale CST soil subgroup distribution map in theory. Through referencing the soils of Zhejiang could be sorted into 8 soil orders, of which Cambosols was in dominance, accounting for 31.3%, Anthrosols for 23.4%, and Histosols for the least percentage in area. At the order level in CST, soil distribution presented a clear pattern. These findings are of a certain value to directing soil classification using CST, and provide examples for CST soil mapping of Zhejiang Province.

    • Simulated-rainfall experimental study on runoff of sheet flow on loess hillslope

      2013, 50(2):268-274. DOI: 10.11766/trxb201203310102

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      Abstract:Sheet flow runoff on loess hillslope was studied through simulated rainfall experiments, under the conditions of rainfall intensities of 1.00,1.33,1.67,2.00,2.33 mm min-1 and slopes of 9°,12°,15°,18°,21°.Results show that 1) regardless of rain intensity and slope degree, the runoffs displayed a general trend in rate, that is, increasing first and leveling off late, however, the turning point came 5 min earlier in treatments of rain intensity than in treatments of slope degree, and the variation could be described with a logarithm equationy=aLn(x)+b; 2) depth of the sheet flow runoff varied with rainfall intensity and slope gradient as well, which could be described with a power function equation H=aIband H=aSbrespectively; 3)the integrated response of the runoffs in depth to rainfall intensity and slope gradient could be described with a dual power function equation H=3.83I1.01S0.490, and the response to rainfall intensity was greater than to slope gradient; and 4)the effect of sheet flow runoffs on sheet erosion was significant, and varied with rainfall intensity and slope gradient, which could be described with a power function equation M= 0.0378 H1.21and a linear equation M = 0.235 H -3.48 respectively.

    • Characteristics and hydrodynamic mechanism of sediment yield in different topographical units of different spatial scales in Loess hilly-gully region

      2013, 50(2):275-280. DOI: 10.11766/trxb201205070172

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      Abstract:Characteristics and hydrodynamic mechanism of sediment yield in different topographical units of different scales in Loess hilly-gully region were studied using Qiaogou Watershed in that region as prototype for observation and making use of the observation facilities therein including three hydrological stations and three large-scaled field runoff plots , which located in different topographical units. Results show that the soil erosion modulus displayed a trend of “rising-peaking-declining” with the escalation in spatial scale. At the slope scale, sediment yield was mainly related to depth of runoff. The relationship could be well described by runoff shear stress, with which sediment delivery rate increased. At the watershed scale, sediment yield was related not only to runoff depth but also to peak flood flow. Sediment delivery rate was a power function of the runoff erosion power at the watershed scale.

    • Rill erosion on different soil slopes and their affecting factors

      2013, 50(2):281-288. DOI: 10.11766/trxb201204150134

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      Abstract:Indoor simulation of rainfall, 1.5 mm min-1 in intensity was conducted using deionized water on slopes of Lou soil and Cultivated loessial soil, 10°, 15°, 20° and 25° in slope degree, and 5 m and 10 m in shope length,separately. Changes in the slopes caused by each rainfall event were monitored with a 3D laser scanner and analyzed for impact of slope degree on rill erosion, differences between slopes of different soils in rill erosion and their affecting factors. Results show that as the Lou soil is dominated with silt and clay in texture with silt content being 64.12% and clay content 18.42, and the Cultivated loessial soil composed mainly with silt (67.95%) and some clay (14.52%) and sand (17.53%), under the same conditions, rian water infiltration rate was lower, runoff generation earlier and runoff velocity higher in the former than in the latter, and as a result, erosion holes occurred earlier and rills formed more easily in the former. During the rainfall event, higher in volume, the runoff stabilized earlier in the former than in the latter. As the erosion rate was higher in the former, silt yield tended to increase, while it remained almost unchanged in the latter. Comparison between the slopes of two different soils in rill development shows that the rills on the Lou soil slopes were distributed in parallel, while those on of the Cultivated loessial soil slopes looked like wide tree branches.

    • Soil salinity characteristics of Manas River valley in Xinjiang

      2013, 50(2):289-295. DOI: 10.11766/trxb201206150236

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      Abstract:Characteristics of the soil salinity of the Manas River Valley in Xinjiang was studied using correlation analysis and principal component analysis methods, in combination with regional investigation of soil properties. Results show that the soils in this region are of the type of soils salinized mainly with sulfate, and of the grades of severely and moderately salinized soils. Profile distribution of soil salinity of the soils is characterized by bottom accumulation. Soil salt content (St) is in significant positive correlation with content of SO42- and Ca2+. SO42-is the dominant anion while Ca2+ the dominant cation of the salts distributed in all layers of the soil profile. SO42-, Ca2+, Mg2+ and St are the eigenfactors to characterize soil salinization of the Manas River Valley. This study will provide an important theoretical basis for sustainable utilization of the soil resources in the Manas River valley of Xinjiang.

    • Effect of scale of model on prediction of soil organic matter in complex landscape region

      2013, 50(2):296-305. DOI: 10.11766/trxb201203300100

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      Abstract:Taking DengfengCounty as a case for study, effects of scale of the model on prediction of soil organic matter in complex landscape region were studied and at the same time the issue of how to comprehensively utilize spatial data of various scales explored. Soil organic matter of Dengfeng was predicted using the Regression Kriging method for analysis of roles and effects of spatial data of various scales on modeling. It was found that the soil organic matter was macroscopically related to elevation factor and large scale spatial data were the most optimal for use in fitting the trend value, while small scale spatial data were not proper for use in fitting. However, they revealed details of the spatial variability of small scale residual value and enhanced the spatial structure of large scale residual value, which effectively improved precision of the prediction. Therefore, in predicting soil organic matter in complex landscape, it is necessary to use large scale data in combination with small scale data to fit spatial variogram of residual value based on simulated trend value of large scale data and hence to predict residual value. Then by adding the trend value onto the residual value, soil organic matter predicted value is thus obtained.

    • Characteristic evolution of soil organic carbon pool with the process of natural restoration of Karst forest vegetation

      2013, 50(2):306-314. DOI: 10.11766/trxb201204040106

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      Abstract:To study evolution of the characteristics of the soil organic carbon pool in the Karst region of Maolan with the process of natural restoration of karst forest vegetation, the concept of space as a substitute for time was adopted. Results show that soil bulk density (0.94~1.15 g cm-3 in 0~10 cm soil layer and 0.98~1.19 g cm-3 in >30 cm soil layer) and rock fragment content (19.93~26.61% in 0~10 cm soil layer and 20.36~32.11% in >30 cm soil layer) increased with soil depth and decreased along with the process of the restoration; soil volume (20.13~22.02 m3 in 0~10 cm soil layer and 4.16~6.87 m3 in >30 cm soil layer), soil organic carbon content (21.14~52.67 g kg-1 in 0~10 cm soil layer and 11.15~25.93 g kg-1 in >30 cm soil layer), soil organic carbon density (1.91~4.03 kg m-2 in 0~10 cm soil layer and 0.39~1.96 kg m-2 in >30 cm soil layer), soil organic carbon storage (0.538~0. 883 t in 0~10 cm soil layer and 0.039~0.137 t in >30 cm soil layer in a sample lot 900 m2 in area) and readily oxidizable carbon (5.28~33.25 g kg-1 in 0~10 cm soil layer and 5.98~14.13 g kg-1 in >30 cm soil layer) increased with the process of the restoration and decreased with soil depth; soil organic carbon became more stable and less active with the process of the natural restoration in the 0~20 cm soil layer, but went reversely in the >20 cm soil layer and it increased in stability and decreased in activity with soil depth. The variation of soil organic carbon with the process of the natural restoration generally demonstrates that soil plays a role as a sink of atmospheric carbon dioxide. At the early restoration stages, soil organic carbon in the soil was low in quantity, poor in quality, and high in surface accumulation tendency, showing that the sink effect of the soil was not significant and that the soil was high in carbon sequestration potential, however, at the late stages, all went reversely. It is, therefore, essential to take strong measures to preserve karst forests and let them restore naturally, which helps improve soil quality and accumulate organic carbon.

    • Changes in major fractions of active soil organic carbon in alpine steppes different in states

      2013, 50(2):315-323. DOI: 10.11766/trxb201205290209

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      Abstract:Changes in major fractions of active soil organic carbon (ASOC) and effects of soil microbes on ASOC in the surface layer (0~10 cm) and the subsurface layer (10~20 cm) of alpine steppes different in state (normal, lightly and severely degenerated) in the north Tibetan Plateau. Results show that significant differences were found between readily oxidation carbon (ROC), microbial biomass carbon (MBC), light fraction of organic carbon (LFOC) and water soluble organic carbon (WSOC) in response to changes in soil environment. Their respective mean distribution ratio was11.10%, 0.57%, 0.04% and 0.03%. The cold dry environment of the plateau was not favorable to formation and accumulation of WSOC and LFOC. Regardless of state of the steppes, contents of the various fractions of organic carbon were higher in the surface layer than in the subsurface layer. Compared with the contents of the various fractions of organic carbon in normal steppes, those in degraded steppes were slightly higher in the surface layer, but significantly lower in the subsurface layer, and the changes were greater in mildly degraded steppes, showing a decreasing order of normal steppes > severely degraded steppes > lightly degraded steppes in terms of content of organic carbon in the 0~20 cm soil layer. In steppes of all states, cellulolytic enzymes played a significant promotive role in formation of the fractions of ASOC ( R2: 0.731~0.960), whereas activity of the cellulolytic enzymes was much affected by soil actinomycetes and fungi. In seriously degraded steppes, soil microbes may have completed their succession into microbial populations that were much higher in stress resistance and cellulolytic enzyme secretion ability. And the relatively higher SOC and ASOC contents in the steppes characterized greater consumption of organic residues in the soil.

    • Nitrogen mineralization potential of yellow soil, a major tobacco planting soil in Guizhou

      2013, 50(2):324-330. DOI: 10.11766/trxb201204110123

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      Abstract:A total of 943 yellow earth samples were collected from 9 major flu-cured tobacco production regions in Guizhou for analysis of nitrogen (N0) using the Stanford intermittent leaching-aerobic incubation method, and of the soil samples, 93 typical ones were picked for determination of mineralization rate constant. Results show that of the soils the nitrogen mineralization rate constants averaged 0.031 mg kg-1 d-1, and the nitrogen mineralization potential averaged 92.8 mg kg-1, and varied sharply from region to region in the range of 10.2~280.5 mg kg-1. The potential was 103.5, 90.6, 71.0, 116.2, 91.1, 89.0, 79.6, 84.6 and 99.6 mg kg-1 for for the soil of Anshun, Bijie, Guiyang, Liupanshui, Southeast Guizhou, South Guizhou, Southwest Guizhou, Tongren, Zunyi, respectively. Of the 9 tobacco growing regions of Guizhou, the potential N supply capacity was relatively low in the center of the province, and increased gradually towards all directions geographically, and turned out to be a bit too high in some regions in Liupanshui and Southeast. The potential N supply capacity of yellow earth was found to be positively related to the content of organic matter. It is, therefore, feasible to make primary assessment of nitrogen mineralization potential of tobacco-growing yellow earths using the exponential function model. The macroscopic knowledge of the potential nitrogen supply capacity of the tobacco-growing yellow earths in Guizhou will help provide a sound basis for rational arrangement of flu-cured tobacco cultivation in the Province.

    • Effect of sweet corn as a catch crop on residual and leaching loss of soil nitrate in protected vegetable soil in Taihu Lake region

      2013, 50(2):331-339. DOI: 10.11766/trxb201206040214

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      Abstract:To explore ways to control nitrogen leaching loss from protected vegetable production systems during the summer fallow season and hence to mitigate the risk of N pollution of groundwater in the Taihu Lake region, a field experiment was conducted to evaluate effects of planting sweet corn as catch crop on NO3--N content, soil electrical conductivity and pH in soils different in N application rate and further to observe its effects on nitrogon leaching using lysimeters and on yield of the following crop, lettuce. It was found that relative to fallow, planting sweet corn as catch crop reduced soil NO3--N concentration from 251.4 mg kg-1 to 143.5 mg kg-1 in the surface soil layer (0~10 cm) and by 4.2%~30.7% in the top soil (0~50 cm). Besides, it reduced soil conductivity significantly, or by over 30% in the surface soil layer, but did not affect pH much. Although planting sweet corn didn’t affect volume of leachate, it did reduce the total N concetration from 102.6 mg kg-1 to 53.7 mg kg-1 in leachate from plots receiving a high rate of N fertilizer under the conventional management practice. Compared with the fallow treatment, the sweet corn treatment reduced the total N leaching by 30.4% , which, however, did not have any effect, either positive or negative, on yield of the succeeding crop, lettuce. The findings indicate that in summer, the protected vegetable land in South China can be used to plant sweet corn as catch crop, instead of being left in fallow, which can be extrapolated as an efficient approach to reducing the risk of nitrogen leaching.

    • Comparison between different instruments in potassium determination performance

      2013, 50(2):340-348. DOI: 10.11766/trxb201203080066

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      Abstract:To determine potassium, there is a variety of instruments available for use, but they are quite different in working principles, performance, advantage and shortcoming. In this study, comparison was made between Inductively Coupled Plasma Spectrometer (ICP), Atomic Absorption Spectrometer (AAS), M410 Flame Photometer (FP-M410) and HG-5 Flame Photometer (FP-HG-5) in detection limit, linear range, stability and interference resistance of potassium determination. Results show that the detection limit was 0.16 mg L-1 for ICP, 0.002 mg L-1 for AAS, 0.005 mg L-1 for FP-M410 and 0.007 mg L-1 for FP-HG-5, and the maximum linear range 1 000, 3, 100 and 60 mg L-1, respectively. Their acid interference resistance followed an order of FP-HG-5 > ICP > FP-M410 > AAS, while their salt interference resistance did an order of FP(HG-5)> FP(M410)> ICP > AAS, which was subject to some variation with the type and concentration of the salt. The comprehensive comparison reveals that ICP is suitable for determination of K relatively high in concentration and a variety of other elements simultaneously, but the cost of its operation for potassium measurement alone is relatively high; AAS is suitable for determination of K relatively low in concentration with a narrow linear range, but the addition of Sr and dilution of high K solution may reduce its efficiency, and moreover its operation cost is also quite high; FP-M410 is easy to operate and low in cost, but susceptible to interference and hence low in stability; and FP-HG-5, with Li internal standard is low in detection limit, good in stability, proper in linear range and high in resistance to the interference of acids or salts, which suggests that FP-HG-5 is the first choice for accurate determination of potassium.

    • Allelopathic effects of wheat straw extract and decomposition liquid on rice

      2013, 50(2):349-356. DOI: 10.11766/trxb201206150234

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      Abstract:An experiment was carried out to investigate effects of wheat straw extract and wheat straw decomposition liquid on seed germination and seedling growth of rice, and to define allelopathic effect of wheat straw on rice. The straw used in the test came from mature wheat crop. Wheat straw extract was prepared by putting wheat straw in 30 ℃ pure water for extraction for 48 h, and wheat straw decomposition liquid was prepared by immersing wheat straw in 30 ℃ water for incubation for 7 or 15 days. The rice seed germination test was carried out using the plate culture method and the rice growth test using the sand culture method. Results show that compared with the control, the extract and the liquid both decreased seed germination index, plant biomass, chlorophyll content and root activity of the rice, significantly (p<0.05), while increasing malondialdehyde content in the plant, significantly (p<0.05). The liquid demonstrated stronger allelopathic effect than the extract, wheat leaf extract than stem extract, and the 15 day liquid than the 7 day liquid. Once diluted five folds, the extracts and liquids became less in their effect on rice germination and plant growth. The extracts and liquids were all quite high in total phenolic content, ranging from 90.80~222 mg L-1. Total phenolic acid content was significantly and negatively related to rice plant fresh weight, root activity, chlorophyll and rice germination index, while malondialdehyde content in the plant was positively related. The allelopathic effects of the extracts and liquids varied in strength, which was related with straw decomposition method, different parts of straw and length of decomposition time, and to the total phenolic acid content in the extracts or liquids, as well.

    • Bioavailability and effect of pyrene on antioxidases in earthworms

      2013, 50(2):357-363. DOI: 10.11766/trxb201205030159

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      Abstract:Aging behavior in soil, bioaccumulation and effect on antioxidases in earthworms of pyrene were investigated in the lab. Results indicate that its aging rate was rather high at the initial stage, and then slowed down with the time passing by. Its effect inhibiting earthworms growth was rather significant in the first 60 d, but turned to be insignificant on the 150th day in all the pyrene treatments (p<0.05). The higher the pyrene concentration in the soil, the higher its concentration in the earthworm. However, pyrene concentration was higher in earthworms’ intestines than in the epidermis throughout the entire experiment, suggesting that earthworms accumulate pyrene mainly by ingesting it with soil particles rather than by pyrene penetrating through their epidermis. The concentration of pyrene in earthworms’ epidermis and intestines decreased as the incubation went on, showing a significant difference between the determinations on the 60th day and the 150th day (p<0.05). The effect of pyrene promoting SOD activity in earthworm gradually weakened with pyrene aging on, and turned to be inhibiting SOD activity on the 150th day (p<0.05). Compared with CK, Treatment Pyrene (100 mg kg-1) was significantly higher in CAT activity in earthworm in the first 60 days (p<0.05), and was found almost the same on the 150th day, while MDA content decreased with pyrene aging on and was found to be much lower on the 150th day in both Treatments Pyrene (50 and 100 mg kg-1) (p<0.05).

    • Genetic diversities of soil ammonia-oxidizing bacteria at various vegetation restoration stages in Southwest Guangxi, China

      2013, 50(2):364-371. DOI: 10.11766/trxb201206100226

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      Abstract:Soil samples were collected from soils under different vegetations, i.e. T (tussock), S (shrub), SF (secondary forest) and PF (primary forest), representing different vegetation restoration stages in the Karst region in Southwest Guangxi, China, for analysis of genetic diversity of ammonia-oxidizing bacteria (AOB) and their relationships with urease activity and physico-chemical properties of the soil. Results show that with the advancement in vegetation restoration, genetic diversity and Shannon and Evenness indices of AOB in the soil increased except for under tussock, and moreover, AOB community structure altered, with changes embodied in inconsistent distribution of Nitrosospira clusters 3a and 3b populations as a result of variation of the sensitivity of Nitrosospira cluster 3 population to ammonium concentration. Correlation analysis reveals that soil urease activity in the soil was positively related to ammonium content. Hence, soil urease may alter AOB diversity by affecting ammonium content. However, at the late stage of vegetation restoration, the lower ammonium content did not lead to any reduction in AOB diversity. LIBSHUFF and RDA analysis exposed that AOB community structure was closely related to vegetation type, soil urease activity and soil pH, indicating that vegetation, soil N availability and pH may possibly be the main factors affecting soil AOB diversity. These findings may serve as certain scientific basis for further understanding of soil N cycling in Karst region.

    • Effect of long-term fertilization on soil microbial communities in farmland of black soil

      2013, 50(2):372-380. DOI: 10.11766/trxb201202290053

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      Abstract:Using real-time PCR and denaturing gradient gel electrophoresis (DGGE), effects of long-term fertilization on densities and structures of the soil microbial communities in corn fields of black soil were determined. The corn fields were located at the Hailun Experimental Station of Agricultural Ecology in Northeast China and had been under a long-term fertilization experiment designed to have 3 treatments, i.e. NF (no fertilizer), NP (chemical fertilizers nitrogen and phosphorus), and NPM (chemical nitrogen and phosphorus combined with pig manure). In real-time PCR analyses, the total genomic DNA of the microbial community in treatments NF, NP and NPM was found to be 381, 1351 and 1773 ng per gram of soil, and of the fungal community, 113.3, 127.3 and 20.6 ng respectively. Fungi to bacteria ratio in the 3 treatments was 0.31, 0.09 and 0.01, separately. Obviously Treatment NPM is lower than Treatments NF and NP in this aspect (p<0.05). Analysis of the DGGE indices shows that Treatments NP and NPM did not improve the soil microbial communities in diversity, uniformity and dominance of dominant microbes. However, according to principal component analysis, these two treatments altered the structures of the soil bacterial and fungi communities, especially the latter. Meanwhile, the tree clustering analysis indicates that the bacterial community structures in Treatments NP and NPM were quite similar, being 0.89 in similarity coefficient. But for the fungal community, its structure in Treatment NP is more similar to that in Treatment NF, with similarity coefficient being 0.63, which is higher than 0.51 between Treatments NP and NPM. All above findings indicate that the long-term fertilization using organic fertilizer (pig manure) could significantly decrease the fungal to bacterial ratio and alter the soil bacterial and fungal community structure in the filed.

    • Effect of bio-organic fertilizer on pathogenic and functional bacteria composition in rhizospheric soil of field vegetables

      2013, 50(2):381-387. DOI: 10.11766/trxb201203020057

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      Abstract:Populations of pathogenic Ralstonia solanacearum and functional bacteria groups in the rhizospheric soils of continuous cropping tomato and pepper applied with a kind of bio-organic fertilizer (BOF) and with conventional fertilizer (CK) were studied using the real-time quantitative PCR techniques. As compared with CK, BOF increased the yields of tomato and pepper by 26.0% and 19.9%, respectively, and decreased the incidence of bacterial wilt on tomato and pepper by 41.5% and 44.7%, respectively. BOF increased the population of Azotobacter and Pseudomonas flurosecens by 23.5% and 29.5%, and by 25.8% and 20.2%, and decreased the population of R. solanacearum by 73.2% and by 90.1%, respectively, in the rhizospheric soil of healthy tomato and pepper. In conclusion, the bio-organic fertilizer is capable of regulating the composition of microflora in rhizosphere soil of crops, reducing the incidence of soil-borne plant disease, and promoting plant growth. Real time PCR techniques are quick and accurate in determination of the population of functional microbes in soil.

    • Relationship of magnesium deficiency of tomato with salt composition and ion activities in greenhouse soil

      2013, 50(2):388-395. DOI: 10.11766/trxb201203290099

      Abstract (2904) HTML (0) PDF 1.54 M (2281) Comment (0) Favorites

      Abstract:Ion composition and proportion of soluble soil salts and activities of Mg2+, Ca2+ and K+ ions were determined in soils different in greenhouse cultivation history and in degree of magnesium deficiency reflected in tomato growing therein, and their relationships with Mg deficiency of tomato were analyzed. Results show that among the soluble soil salts Ca2+, K+ and NO3-in the soil increased in concentration linearly with the history of greenhouse cultivation going on. Ca2+ ion was the dominate cation in the soluble salt and NO3-ion became the dominate anion after 5 years of greenhouse cultivation. significant relationships were found of Ca2+ and NO3-ions with total salts and NO3-ions in the soil, indicating that NO3-ion was the major factor contributing to soil salinization. Mg deficiency symptom became more obvious, when contents of Ca2+, K+ and NO3-ions, total salts, and mole ratios of Ca2+/ Mg2+ and K+/ Mg2+ rose in the soil. In soils where tomato displayed Mg deficiency, salt content reached the level of soil salinization. With the content of soil salt rising, Ca2+ and Mg2+ activities decreased exponentially. Activities of Ca2+ and Mg2+ were significantly lower in soils where tomato displayed Mg deficiency than in soils where tomato grew normally, while activity ratios of (K+)/( Mg2+) and (Ca2+)/( Mg2+) were the other way round, and the activity ratio of (K+)/( Mg2+) increased significantly with the extent of Mg deficiency, reaching higher than 1. The decrease in Mg2+ activity due to salt accumulation in soil and the antagonistic effect of K+ enrichment on plant Mg2+ absorption were the two major causes inducing appearance of the symptom of magnesium deficiency on tomato growing in calcareous soil.

    • Effect of vegetation restoration on soil shear strength of roadside slopes of unpaved roads in the Three-Gorges Reservoir Area

      2013, 50(2):396-404. DOI: 10.11766/trxb201204300153

      Abstract (2531) HTML (0) PDF 4.27 M (2466) Comment (0) Favorites

      Abstract:To study effects of roadside slope vegetation restoration on shear strength (τ) of and surface soil loss from the slopes, seven vegetation restoration models were adopted in in-situ shearing tests. It was found that vegetation root systems decreased in density with increasing soil depth, the root length density (RLD) in the 0~10 cm soil layer accounted for 34%~78% of the total RLDAnd the vegetation root magnitude was positively related to soil water content (SWC) showing a exponential function correlation. Shear strength of the surface soil layer (0~10 cm) was mainly affected by vegetation root systems and vegetation coverage and increased as a exponential function of RLD, root weight density (RWD) and vegetation cover (VC ). The controlling factors on τ varied with soil depth, and regression analysis showed RLD, RWD and VC had statistically significant effects on τ in the 10 cm soil depth. However, none of the predominant factors on τ were founded in the 30 cm soil depth, which was so defined as a transition layer and was the lowest shear strength τ as compared with the 10 cm and 50 cm soil depths. The influence of soil bulk density (ρ) andSWC got bigger on τ with soil depth, showing a positive linear relationship and a negative exponential function relationship, respectively in 50 cm soil depth.

    • >Reviews and Comments
    • Fate of virus in different environmental media: A review

      2013, 50(2):405-412. DOI: 10.11766/trxb201206250251

      Abstract (2924) HTML (0) PDF 934.41 K (2500) Comment (0) Favorites

      Abstract:Viruses from sewage and wastewater may enter the water and soil environments, posing health risks to humans and animals. The knowledge of fates of viruses in various water and soil environments is the basis for developing safe effective methods for virus pollution control. A review is presented here of the researches so far accomplished on fates of viruses in waterbodies and soils, and materials that are capable of removing viruses from the systems and their efficiencies and mechanisms as well. The review also elaborates effects of air-water interface, autochthonous microbes and content and composition of soil organic matter on fate of viruses, and compares active carbon with materials rich in Fe- and Al-oxides in virus removing efficiency. The former is high in adsorbency, while the latter is lethal to viruses. At the end, the review discusses choices of media for virus removal and potential applications of the virus removing materials, and puts forth some suggestions for further study in this aspect based on the effects of composition of native soil microbes on fate of virus.

    • >Research Notes
    • Effects of changes in land use on soil macro-arthropod communities in Horqin sand land

      2013, 50(2):413-418. DOI: 10.11766/trxb201206060220

      Abstract (2734) HTML (0) PDF 664.28 K (2617) Comment (0) Favorites

      Abstract:community structure and diversity of soil macro-fauna under six types of land use / cover was studied in Horqin Sand Land to understand effects of changes in land use / cover on soil macro-fauna in north agro-pastoral ecotone, the results showed that 1) the richness, density and diversity of soil macro-fauna was the highest in natural grassland, second was in fixed sand-land and plantation. Though the richness, density and diversity of soil macro-fauna was lower in dry and irrigation farmlands, they was significant higher than that in moving sand-land.; 2) dominant group was Anthicidae in natural grassland, fixed sand-land, plantation and irrigation farmland, was Tenebrionidae in dry farmland, and dominant group was not signification in moving sand land; 3) species similarity was the highest among natural grassland, fixed sand-land and plantation, species similarity was the lowest between moving sand-land and other five types of land use/covers, and was in the middle in farmlands; 4) the diversity and density of soil macro-fauna was increased significantly after moving sand-land turn to fixed sand-land or dry farmland turn to irrigation farmland, the diversity and density of soil macro-fauna was decreased significantly after natural grassland was reclaimed to farmland or fixed sand-land was turned to plantation; 5) the proportion of phytophagous and omnivorous fauna in the community increased after moving sand-land turned to fixed sand-land, the position of predatism fauna in the community increased after dry farmland turned to irrigation farmland.

    • >Communications and Comments
    • Suggested revisions of diagnostic criteria for Halosols and relevant soils in Chinese Soil Taxonomy

      2013, 50(2):419-422. DOI: 10.11766/trxb201204250151

      Abstract (3308) HTML (0) PDF 504.24 K (2806) Comment (0) Favorites

      Abstract:The criteria for classifying soil as saline taxon are different in different soil classification systems. Soils are named as saline soil in Chinese Soil Taxonomy, World Reference Base for the Soil Resources and US Soil Taxonomy, respectively, when soil has a salic horizon starting within 30 cm, within 50 cm and within 100 cm from the soil surface. This paper describes some soil profiles that were classified into saline taxon in CST, WRB and ST before they are reclaimed, to see if these soils after a long history of irrigation are still classified into saline taxon in the three soil classification systems. The results show that the salts were leached into certain depth, the salic horizons were observed at different depth from the surface, many profiles could not be classified as Orthic Halosols as identified earlier, some of them could not be classified as Solonchaks, few of them even could not be classified as Salids. The depth of salic horizon is related to the amount of irrigation water and irrigation models. According to the present study, we suggest that the criteria of ST should be taken for keeping reclaimed saline soils in the saline taxon, i.e. Soil classification should not be changed by irrigation.

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