Abstract:Geochemical characteristics of Rare Earth Elements (REEs) in basalt-derived soil profiles in Leizhou Peninsula were studied. Results show that REE distribution in the soil profiles is not only controlled by their parent basalts, but also affected by weathering and soil forming processes. ∑REE and δEu demonstrate clear inheritance of basalts, while the weathering and soil forming processes result in REEs enrichment in the upper horizons of the profiles and obvious Ce positive anomaly. However, no remarkable REE fractionation is observed during the soil forming process. ∑REE shows an extremely significant negative correlation with Fe2O3 content, which may be attributed to enhanced Fe-oxides crystallization and decrease in content of REE-rich amorphous iron, while an extremely significant positive one with the contents of P2O5 and MnO, which should be caused by the existence of REEs-containing phosphate and Mn-oxides minerals, and with the content of clay (especially the fraction <1μm) as well, demonstrating that the adsorption of REEs by clay minerals that are increasing during the weathering and soil forming processes is an important factor for the enrichment of REEs. Furthermore, the adsorption of light rare earth elements (LREEs) by clay minerals is more obvious.

Abstract:According to comprehensive analysis of out-door investigation findings and indoor test data of physical and chemical properties, as were as “Chinese soil taxonomy systerm, The diagnostic horizons, diagnostic characteristics were identified, and their attribution in soil taxonomy systerm were definited for twenty six soil profiles. The results showed that there were belong to six Orders, eleven Suborders, seventeen Groups ,eighteen Subgroups. Generally speaking, there were in the order of Ferrosols、Argosols、Spodosols、Cambosols、Primosols and Gleyosols with the rising of elevation, and classification and the international soil classification based on reference of the reference

Abstract:Effects of PAMs different in molecular weight (MW) (12×10⁶, 15×10⁶ and 18×10⁶ Da) and hydrolysis degree (7%, 20% and 35%) on soil infiltration and soil erosion were investigated. Results show that all the PAMs, regardless of MW, demonstrated pronounced effect on infiltration and increased steady infiltration rate by 58.9%，92.2% and 83.3%, separately, over the control. The effect of PAM medium or high in molecular weight was more significant than that of PAM low in molecular weight, but no big difference was observed between the former two. All the three PAMs decreased soil erosion by 26.3%，52.6% and 26.3% separately as compared with the control. PAM medium in molecular weight was more effective than the other two. PAMs, though different in degree of hydrolysis, all increased steady infiltration rate by 1.9, 2.4 and 2.3 times, separate over the control. The PAM 20% in hydrolysis was more effective than the other two in increasing initial infiltration rate, but they did not show much difference in affecting soil erosion. PAMs low in molecular weight have short chains and hence are unable to form bridges between two adjoining soil particles, thus weakening their function of cohesion, while PAMs high in molecular weight are long in chain and hence unable to penetrate into the space between soil aggregates. However, PAM moderate in molecular weight have chains moderate in length, and can easily go into soil pores and bridge soil particles, thus enhancing their function of cohesion. PAMs low in hydrolysis are low in charge density and in adsorption, too, while PAMs high in hydrolysis are high in charge density, thus forming high repulsion between molecular chains, which in turn leads to reduced adsorption. Therefore, PAMs, 20% in hydrolysis, are the most suitable sort for field application.

Abstract:Adsorption patterns of Pb2+ on the surface of birnessites different in Mn oxidation were studied with an X-ray absorption fine structure (XAFS) spectroscopy and mechanism of the adsorption explored by comparing the patterns. Results show that birnessites high in Mn oxidation were high in Pb2+ adsorption capacity. Nearby a Pb2+ ion adsorbed on the surface of birnessite existed one Pb-O and two Pb-Mn shells. In birnessites the same in Mn oxidation, when Pb2+ adsorption was low (600 mmol/kg), the coordination number of oxygen atom and Pb2+ in the Pb-O shell was 3.1 and they were 0.227 nm apart, and the coordination number of Mn atom and Pb2+ in the two Pb-Mn shells was 2.8 and 6.1 and they were 0.357 and 0.377 nm apart, separately. When Pb2+ adsorption rose up to 2344 mmol/kg, the coordination environment distorted. According to the fitting, in the Pb-O shell, the coordination number of oxygen atom and Pb2+ decreased to 1.2, and the distance between the two was 0.226 nm, and in the two Pb-Mn shells, the coordination number of Mn and Pb2+ decreased to 1.0 and 2.8, separately, and the distances between the two was 0.356 and 0.375 nm, separately. In birnessites different in Mn oxidation, Pb2+ adsorption patterns were basically the same. The three adsorption patterns commonly found were single-corner-sharing complex formed on side surfaces of layers along u axis, double-corner-sharing complex formed on side surfaces of layers along a or b axis, and triple-corner-sharing complex formed with the octahedral vacant sites. The amount of Pb2+ adsorbed increased with increasing AOS in birnessite, which led to decrease in Pb2+ coordination number between Pb and O in Pb-O shell and Pb-Mn shells due to the distortion of the Pb2+ coordination environment.

Abstract:Denitrification and its products (N2, N2O and NO) in four forest soils collected from Changbai Mountain were investigated by acetylene inhibition method applied to a laboratory incubation under flooded condition with N2 gas in the headspace. The tested four forest soils are all acid, soil pH varied from 4.5 to 5.0 and the organic carbon changed in 24.6-83.0g kg-1. The results showed denitrification potential and composition of denitrification products varied greatly among the investigated soils with a decreasing order of denitrification potential: Pinus koraiensis > Betula platyphylla Suk.> Pinus koraiensis - Picea asperata (Mast.) - Akjes fabri (Mast.) > Larix gmelini（Rupr.）. Denitrification potential was positively correlated with soil organic carbon and nitrogen content significantly (p<0.01), not significantly with soil pH. Compared the Treatments with acetylene inhibition and no acetylene inhibition, we found that during the period of incubation, N2O was always the dominant product of denitrification, accounting for 50% ~ 85% of total N gas production. The ratio of N2O to total N gas production was weakly correlated with soil pH (p = 0.12). NO was a minor product of denitrification, accounted for only 0.2% ~ 2.4% of total N gas production. A significant logarithm correlation between the ratio of NO to total N gas production and the soil organic carbon content was observed to be significant (p<0.05). These results implied that denitrification process would not transform reactive nitrogen into inert nitrogen (N2) effectively in Changbai Mountain forest soils and the significance of the denitrification removing reactive nitrogen should be re-assessed.

Abstract:Humic acid (HA) was extracted from surface soil under evergreen broadleaf forest in Jingyun Mountains of China. Effects of acidity, ion strength and temperature on stability and thermodynamics of the complex reaction between the humic acid and Mn2+ ion were studied using the ion-exchange equilibrium method. Results showed that its stability constant increased with increasing pH when ion strength and temperature remained unchanged, and with increasing ion strength,as well. Ligancy of the complex reaction increased with pH rising from 3.0 to 5.0, but decreased with pH rising further up from 5.0 and 7.0, and increased as well with ion strength rising from 0.00 to 0.10 mol L^-1, but decreased, too, with ion strength rising further from 0.10 to 0.15 mol L^-1. The thermodynamic parameters of the complex reaction, including standard free energy change ΔGmθ, standard enthalpy change ΔHmθ, and entropy change ΔSmθ, were all negative when the temperature fell within the range from 298.2 to 308.2K, suggesting that the complex reaction is a kind of exothermic one processing spontaneously and keeping it lower in temperature favors process of the reaction.

Abstract:Simulated bioslurry remediation of PAHs contaminated soil was carried out. Three strains of fungi isolated from petroleum-contaminated soils were inoculated into paddy soils different in application rate of phenanthrene and phthalic acid, to investigate their effects of co-metabolic degradation of B[a]P therein. Results show that in natural soils, some native microorganisms were able to degrade B[a]P and addition of low molecular weight PAHs-phenanthrene increased, degradation rate of B[a]P in the soil. The effect was greater when the application rate of phenanthrene was 100 mg kg-1 than when it was 200 mg kg-1. But the addition of phthalic acid did not show much effect. In sterilized soils, degradation of B[a]P in soils was hardly observed. However, inoculation of Penicillium stimulated degradation of B[a]P in all the three treatments, i.e. phenanthrene at 100 mg kg-1, phenanthrene at 200 mg kg- and phthalic acid, but only in the treatment of phenanthrene at 100 mg kg-1 the effect was significant. Inoculation of Aspergillus niger also showed similar effect, which, however, was inhibited by the presence of phenanthrene and phthalic acid in the soil. White-rot fungus could effectively degrade B[a]P, but high concentration of phenanthrene inhibited its effect in the soils, and phthalic acid was neither an optimal co- substrates of white-rot fungus in degrading B[a]P in paddy soils.

Abstract:Enhancement effect of earthworm (Pheretima sp.) inoculation on the remediation efficiency of soil phenanthrene (Phe) and pyrene (Pye) pollution by Pogonatherum paniceum was studied by pot experiments in a green house. Results showed that earthworm activity promoted the growth of Pogonatherum paniceum in soils with initial concentrations of Phe and Pye ranging from 20.05 to 322.06 mg•kg-1, and apparently increased the biomass ratios of root to shoot of the grass. After a 70-day earthworm inoculation, averagely 76.7% of Phe and 70.6% of Pye were removed from the soils planted grass, which were 8.31% and 9.45% higher than those without earthworm inoculation, respectively. Earthworm activity showed higher enhancement effect for the remediation of Pye than for Phe at the same pollution level. Among all possible pathways, the plant-microbial interaction was proved to be the primary means of PAHs degradation, either with or without earthworm activity, and its contribution to the removal of Phe and Pyr in planted soils accounted for up to 46.59% and 42.78% of the total removal, which were 5.03% and 6.14% higher than those in corresponding soils without earthworm (with 41.56% degradation for Phe and 36.64% for Pyr). Results suggested a feasible way for the establishment of high efficiency phytoremediation of soil PAHs pollution by inoculating earthworms, especially for those PAHs with more benzene rings in their molecular structures.

Abstract:Indian mustard (Brassica juncea L.) is a plant species used to investigate accumulation of heavy metals. In this study, a hydroponics experiment was conducted to investigate the accumulation of Cu by Indian mustard with application of EDDS, a biodegradable chelator for phytoremediation. The activity of P-type ATPase, a heavy metal ATPase (HMA) responsible for the Cu export, and its transcriptional expression in roots was analyzed. The results showed that increased accumulation of Cu with elevated Cu concentration in medium was only occurred in roots, but not in stems or leaves. The accumulation of Cu in roots, stems and leaves was decreased with elevated EDDS concentration. The results indicated that the uptake of Cu was controlled by plasma membrane of roots and Cu ions rather than Cu-EDDS chelator complexes were taken up by roots. The activity of P-type ATPase in roots was increased with elevated Cu concentration, but decreased with elevated EDDS concentration. The expression pattern of P-type ATPase gene (BjHMA) was in according to the change of its activity. Our results indicated that P-type ATPase might regulate Cu uptake in Indian mustard by actively exporting Cu outside root cells amongst a certain range of ambient Cu concentration.

Abstract:In order to explore correlations between biosorption and extraction of phenanthrene in soil with different extractants (acetone, dichloromethane, butanol, ethyl acetate and 2-Hydroxypropyl-beta cyclodextrin, HPCD), phenanthrene in soils different in aging were extracted with mild solvent extraction methods. A significant relationship was observed between the amount of phenanthrene extracted with mild organic extractants (dichloromethane and butanol) and with mild HPCD and phenanthrene accumulation in earthworms (p < 0.05). The mild butanol extractant can be used to better predict bioavailability of phenanthrene in both aged and unaged soils as compared to the other mild extractants in the present study.

Abstract:Based on determinations of organochlorine pesticide (OCPs) residuals in surface soils around the Guanting Reservoir, Beijing in 2003, 2007 and 2009, the Cardinal-spline interpolation method was used to make up the data of the missing years for prediction of data on OCP residual in 2010. On such a basis, analysis was done for temporal variation of OCPs concentrations at the sampling points and its causes and affecting factors of the degradation of OCPs. By referencing the National Standard for Soil Environment Quality, surface soils in the region were evaluated for OCPs pollution. Results show that 1) OCPs concentrations at some sample sites have rebounded, which suggests existence of exogenous inputs; 2) soil texture is a major factor affecting OCPs degradation rate while vegetation on-site is not; 3) ∑HCH was found below the bottom limit of Grade I criteria of the national standard at all sample sites from 2003 to 2009, and ∑DDT was declining and fell within Grade I criteria of the national standard in 2009; and 4) it is predicted that in 2010, ∑HCH will basically remain stable and ∑DDT go on declining.

Abstract:The DIFS (DGT induced fluxes in sediments and soils) model was used to simulate desorption kinetics of Cu from solid to liquid after depletion of DGT (diffusive gradients in thin films). Results show that the three samples used in the simulation were all in the same category of partial supply with R < 1, as the supply of Cu in solid form was not adequate to maintain the initial level of Cu concentration in the pore water at the interface of DGT. In Sample M1 (R=0.74), the distribution coefficient, Kd and desorption coefficient, k-1 were relatively high, and when DGT was in place for a given period of time, T, adsorbed Cu was rapidly desorbed to make Cu depleted, thus keeping the Cu concentration in the pore water at a constant value, which, however, was still lower than its initial value. In Samples M2 and M3, R, Kd and k-1 were all lower than in Sample M1, and its Cu supply in solid was also small, thus leading to decreasing Cu concentration of the pore water at the interface of DGT with the time of its placement, and a broader range of depletion of adsorbed Cu. The findings indicate that release of Cu from sediments is influenced jointly by the pool of bioavailable Cu and the kinetic parameters of the release. Sample M1, with steady partial supply is characterized by higher Kd and moderate k-1; whereas Samples M2 and M3 unsteady in partial supply by lower Kd and moderate or higher k-1.

Abstract:A long-term stationary field experiment consisting of 5 fertilization treatments was carried out in the Red Soil Ecological Experiment Station of CAS to study effects of fertilization on pH and exchangeable H+ and Al3+ in soil and analyze relationships of organic matter (OM) content with soil pH, and contents of exchangeable H+ and Al3+. Results show that fertilization in all treatments increased soil pH and decreased contents of exchangeable H+ and Al3+. Treatment M (organic manure), Treatment BM (organic manure + microbial agent) and Treatment BMT (organic manure + microbial agent + microelement fertilizer ) were significantly superior to Treatment F (chemical fertilizer) and Treatment TF (chemical fertilizer + microelement fertilizer) in reducing soil acidity. Addition of microelements and microbial agent increased the contents of exchangeable H+ and Al3+ slightly. Soil OM content was significantly correlated positively with soil pH value, and negatively with exchangeable Al3+ content, but not significantly related with exchangeable H+ content. With rising soil OM content, the proportion of exchangeable H+ increased in exchangeable acidity of soil. Long-term application of organic manure to increase soil OM content is a good agronomic practice to reduce acidity and aluminum toxicity in red soil.

Abstract:Two rice cultivars Wuyunjing 7 (Al-tolerant) and Yangdao 6 (Al-sensitive), differing sharply in aluminum tolerance, were selected as subjects in a hydroponic experiment to investigate effects of P on growth of the rice seedling under Al stress and relationship between Al tolerance and P efficiency of the rice through alternation of Al and P treatments for two weeks. Results show that in the aspect of biomass and root parameters, P application alleviated toxic effects of Al on both cultivars. The concentration of P was obviously higher in Cultivar Wuyunjing 7 than in Cultivar Yangdao 6, while the concentration of Al in root was lower in the former than in the latter, and as a result, the P/Al ratio was significantly higher in the former than in the latter. However, though the two cultivars did not differ in Al concentration in the root surface and inter-root free space, Cultivar Wuyunjing 7 was significantly higher than Cultivar Yangdao 6 in P concentration therein, demonstrating that the rice cultivar, high in Al tolerance, is higher in capability of its apoplast of detoxifying Al, which may be related to the higher P uptake efficiency of Wuyunjing 7. In addition, compared with Wuyunjing 7, Yangdao 6 was though lower in P uptake efficiency, it was higher in P utilization efficiency, which suggests that the Al tolerances of the two cultivars do not consist with their P uptake efficiencies and P utilization efficiencies, which may serve as a theoretical basis for selecting and breeding rice seeds for paddy fields of acid soil, that is to say, to select and breed rice of genotypes suitable to acid paddy soils, it is essential to focus on Al tolerance and P utilization efficiency as well.

Abstract:Tetramethylammonium hydroxide (TMAH) thermochemolysis-gas chromatography/mass spectrometry (GC/MS) was employed to investigate the supramolecular structure of particulate organic carbon (POC) sampled from a Tai Lake paddy soil under a long-term field experiment with different fertilization systems. The chromatograms revealed peaks related to compounds derived from lignin and aliphatic compounds. The dominant lignin-derived compounds were mainly derivatives of guaiacyl (G) and p-hydroxyphenyl (P) structures, suggesting the contribution of a non-woody (grass) lignin type (mainly crop residues from rice and rape). The most abundant aliphatic compounds were C8-C30 fatty acid methyl esters (FAMEs) dominated by even-numbered carbon species, in which short chain FAMEs of microbial origin were prevalent. Soil fertilizations induced differences of the distribution of each thermochemolysis compound both in bulk soil and water-stable aggregations, and thereby the relative contribution of each compound to the stability of POC. Generally, the lignin compounds and aliphatic compounds of microbial origin contributed to the accumulation and stabilization of POC under the treatment of chemical fertilizer plus pig manure. Nevertheless, the enhanced POC under chemical fertilizer plus crop straw was attributed preferentially to aliphatic compounds of higher plant origin, followed by those of microbe origin. The higher POC content in water-stable aggregates under organic-inorganic fertilization treatments was supposed to be predominantly due to the decomposition of higher plants. The C stabilization by molecular recalcitrance is supposed to contribute to the C sequestration and stabilization in paddy soils under good managements, the relative distribution of which can indicate the different source of newly-accumulated soil organic C.

Abstract:Labile and recalcitrant organic carbon fractions of red paddy soils under different fertilization practices for 22a were analyzed by two acid hydrolysis methods with H2SO4 and HCl, respectively. The fertilization treatments include: (1) CK，(2) N，(3) P，(4) K，(5) NP，(6) NK，(7) NPK，(8) 2NPK，(9) NPK+OM. Results showed that the two acid hydrolyzed methods agreed with each other very well. Compared to the CK without anything amendments, fertilization generally increased total organic carbon contents of paddy soil. Except the treatment K with only potassium fertilizer, labile organic carbon contents increased in other fertilization treatments. However, only N and NPK+OM treatments promoted Labile index (LIC) of organic carbon significantly (P<0.05), and especially the LIC in NPK+OM increased to a great extent. Also compared to the CK, fertilization, but not N treatment, consistently increased the recalcitrant carbon contents with the effects of NPK+OM being more significant (P<0.05). In terms of Recalcitrance index (RIC), significantly higher RIC was found in K treatment but the lower values found in N and NPK+OM treatments (P<0.05), indicating the contribution of N fertilizer and organic manure to total organic contents being mainly attributed to the labile organic carbon. Therefore, our results imply that we can manipulate red paddy soil organic carbon contents and stability by optimizing fertilization practices, possibly through selecting appropriate organic amendments, reducing N fertilization and enhancing K fertilization.

Abstract:In rice the period of grain filling is characterized by transition of all vegetative organs from sink to source. A pot experiment was conducted to monitor variation of N and protein concentrations, N translocation and enzyme activities representative of nitrogen metabolism after the heading stage in different leaves and stem sections of two rice cultivars different in N use efficiency (NUE), high and low, treated with two levels of N fertilization. Compared with CK or Treatment N0, N application increased N concentration, soluble protein concentration and N translocation in leaves and stems. Nitrogen concentration in functional leaves decreased by 60-67% from heading to maturity, regardless of N rates, which indicates that N in grains comes mainly from leaves. However, N contribution rate from stems to grain depends on environmental N supply. N and soluble protein concentration and N translocation in leaves and stems was lower in Nanguang than in Elio at the maturity stage. Compared with CK, N application increased the activities of four N enzymes. And the activities decreased with the plant growth. The NR and GS activities were higher in Nanguang than in Elio, while NR activity depends more on N rate and growth stage. The GOGAT and GDH activities were lower in Nanguang than in Elio. NR and GS activities were significantly correlated to N and soluble protein concentrations at the heading stage and 2 weeks after the heading. All these indicate that higher NR and GS activities especially the latter, may predict the N status of rice, high N translocation and high NUE in rice.

Abstract:305 groundwater samples from wells in Miyun Reservoir watershed were collected from November to December, 2008, and nitrate nitrogen (NO3--N) concentrations in groundwater were tested. Average NO3--N concentration for all wells sampled was 6.81mg/L, and 16.07% of all wells exceeded 10mg/L, the WHO limit for NO3--N in drinking water. Among them, 35 wells from villages and 13 wells from vegetable lands show high NO3--N concentrations with averages of 9.52 mg/L and 9.55mg/L respectively, near the WHO limit. 28.57% of village wells and 23.07% of vegetable land wells respectively exceeded the WHO limit. 219 wells from croplands (corn and soybean) presented the middle NO3--N concentrations with average of 6.59mg/L and of which 16.08% were above the WHO limit. 10 wells from woodlands demonstrated low NO3--N concentrations with average of 2.66mg/L and none of them were beyond the WHO limit. Nitrate pollution of groundwater in Chaohe River basin was more severe than that in Baihe River basin. Average NO3--N concentration in groundwater from farmlands in Chaohe River basin reached 8.42mg/L, which was higher than that (5.03mg/L) in Baihe River basin. 25% of 124 wells from farmlands exceeded the WHO limit in Chaohe River basin while only 6.56% of 122 wells did in Baihe River basin. High nitrate concentrations in groundwater resulted from more intensive agriculture in Chaohe River basin. NO3--N concentrations in groundwater from farmlands along the rivers increased from upstream to downstream. NO3--N concentrations in groundwater from corn fields decreased toward the rivers, related negatively with groundwater tables and positively with nitrogen fertilizer applications. There might be potential risks for NO3--N concentrations exceeding the WHO limit as groundwater tables are lower than 7 meters or annual fertilizer applications are more than 200kgN /hm2 in corn fields.

Abstract:Tobacco black shank is one of the most serious soil-borne diseases in tobacco production. Biological control has been proved effective and environment-friendly, but screening of antagonists against pathogens is the basic work in bio-controlling. Twelve strains of bacteria antagonist against Phytophthora parasitica var．nicotianae were isolated by using the plate-confrontation method from rhizosphere soils under healthy tobacco plants in tobacco fields seriously infected with the pathogen. The averaged inhabiting rates of the antagonists ranged from 59.4% to 71.1%. The best performer Strain C-5, which was identified as Paenibacillus polymyxa (C-5) based on biochemical tests and 16S rRNA sequence similarity, was then selected for further experiments. Results from antibiotic spectrum experiments show that Strain C-5 was also effective in inhibiting other plant pathogen such as Fusarium osyporunm f. sp melonis , Fusarium osyporum f. sp cucumerinum and P. capsici. Pot experiments show that application of bio-organic fertilizer supplemented with Strain C-5 suppressed the incidence of tobacco black shank by 80% as compared with the control. To our knowledge, this is the first report on the microbiological antagonism of Strain Paenibacillus against Phytophthora parasitica var. nicotianae.

Abstract:To investigate characteristics of the root systems of the plants that constitute the vegetation in the water-level-fluctuation-zone of the Three Gorges reservoir region and their relationship with anti-erodibility of the soil, 6 flooding-tolerant plants, i.e. Cynodon dactylon(L) Pers., Alternanthera philoxeroides (Mart) Griseb, Triarrhena sacchariflora Nakai, Hemarthria compressa(L.f.) R. Br., Cyperus rotundus L., and Arundinella anomala Steud, were selected as subjects for the study. Root-soil core samplers (Eijkelkamp Agrisearch Equipment Model 15.01) were used to take samples from the fields for analysis, a modified hydraulic flume device to analyze the soil samples for water erosion rate and for calculation of anti-erodibility enhancement coefficients of root systems of the 6 plants and the Root Analysis System (WinRHIZO Pro. 2004c) to characterize the root systems. It was found that Alternanthera philoxeroides (Mart) Griseb, Triarrhena sacchariflora (Maxim.) Nakai, Cyperus rotundus L., and Cynodon dactylon (L.) Pers. were relatively higher in mean root/shoot ratio, while Arundinella anomala Steud. and T sacchariflora were in root length density (RLD) and root surface area density (RSAD), and that soils containing roots was obviously lower in soil erosion rate. A. philoxeroides, T. sacchariflora and A. anomala were significantly higher than the other three in anti-erodibility enhancement coefficient (Ec), which was in significant linear regression relationship with RLD and RSAD. Among the root system, particularly roots with D ≤ 2 mm was closely related with soil anti-erodibility, and their RLD and RSAD were in significant linear regression relationship with Ec with correlation coefficient declining with increasing root diameter. It was also found that all the six plants significantly enhanced soil anti-erodibility and A. philoxeroides, T. sacchariflora and A. anomala were the most effective. RLD and RSAD are good indexes to characterize soil anti-erodibility, especially RLD and RSAD of roots with D ≤ 2 mm or D ≤ 0.5 mm and hence the most important parameters in characterizing soil anti-erodibility.

Abstract:Abstract: Aggregates status of soil was one of important physical characteristics of soil , amount of aggregates was important index weighing and estimating soil fertility. Aggregates status of greenhouse soils and uncovered soil was studied by dry-sieved, wet-sieved and water-oscillated. According to evaluation of different diameter scale aggregate content determined by Dry-sieved and mean weight diameter (MWD), the machine stability was worse in greenhouse soils than uncovered soil. The water stability was better in greenhouse soils than uncovered soil according to evaluation of ＞0.25mm water stability aggregate content, MWD of water stability aggregate, destruction rate of aggregate, original stability coefficient and disintegration rate of aggregate. It was related to high organic matter content in greenhouse soils. Increasing organic matter content rose content and water stability of 0.25～10mm aggregate.

Abstract:Soil available nutrients, soil enzyme activity, soil microbial diversity and cucumber yield in a field under crop rotations of cucumber with wheat and hairy vetch with conventional methods and PCR-DGGE to study effect of the rotation on soil micro-ecological environment and yield of cucumber. Results indicate that the rotations significantly increased cucumber yield and effectively improved the soil micro-ecological environment. The rotation of wheat-cucumber increased the yield of cucumber the most significantly (p<0.01), by 28.04%, and improved the overall activity of polyphenol oxidase, catalase and urease. The rotation of hairy vetch-cucumber increased the yield of cucumber by 16.78% and improved the content of soil available nutrients, and the invertase activity significantly over CK (p<0.01) DGGE analysis shows that the rotation helped increase the diversity of bacterial species in the rhizosphere, while decreasing that of fungi at the late fruit-bearing stage. The effect of the rotation of hairy vetch-cucumber was more significant. The rotation of wheat-cucumber showed certain effect on rhizospheric soil fungi as well as the bacterial community structure 30 days after transplanting of cucumber. To sum up, the rotations of cucumber with wheat and with hairy vetch help mitigate the hazard of consecutive cropping of cucumber, improve the soil microbial eco-environment and raise the yield of cucumber.

Abstract:Morphological analysis of phosphorus in biosolids and soils is essential to waste management, improvement of phosphorus use efficiency and control of P leaching risk. Since the early 20th century, various methods have been put forward to analyze forms of phosphorus in biosolids and soils, including chemical fractionation, enzymatic hydrolysis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), 31P nuclear magnetic resonance (31P NMR) and X-ray absorption near-edge structure (XANES). In the paper, various methods of characterizing phosphorus forms in biosolids and soils are systematically summarized and compared. Integrated application of various methods is recommended to better identify forms of phosphorus in bisolids and soils rather than only using a single method so as to provide useful information for choosing appropriate methods for the analysis and also to lay down a foundation for further developing novel techniques for analysis of forms of phosphorus in biosolids and soils.

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