Abstract:In order to explore in depth intrinsic mechanism of using nuclide tracer technique to study soil erosion deeply, spatial heterogeneity and distribution of ¹³⁷Cs & ²¹⁰Pb_ex in a slope in Ningzhen region were studied with the geostatistics method based on the module of Arcgis Geostatistics. Results shows that the unique physicochemical properties of ¹³⁷Cs & ²¹⁰Pb_ex make them distinct from others in spatial heterogeneity and distribution characteristics in slope. The biggish Nugget of ¹³⁷Cs & ²¹⁰Pb_ex indicates that their spatial distribution is definitively influenced by random factors such as soil erosion, farming practices, etc. And it is why they can be used to trace soil erosion. The medium degree of spatial autocorrelation and distribution patterns of ¹³⁷Cs on slope reflect preferably that landform as a structural factor can influence its spatial distribution. Results of the tracing of soil erosion using ¹³⁷Cs should be more comprehensive, more reasonable, and more macroscopical. The very week spatial autocorrelation of ²¹⁰Pb_ex explain that its spatial distribution is more sensitive to the influence of random factors. And it is better at exposing details of soil erosion.. The distribution patterns on a slope differ quite much between ¹³⁷Cs & ²¹⁰Pb_ex, which, on the one hand, indicates that they differ from each other quite sharply in their initial sedimentation layout, partial physicochemical properties, and responses to various affecting factors for variation, etc. and on the other hand, it also hints that the courses of soil erosion traced with ¹³⁷Cs and ²¹⁰Pb_ex can hardly reach an agreement even through adjustment of their calculation models.

Abstract:Based on meteorological data and the data in the Geographic Information System (GIS) database of Nanjing area during the period from 2001 to 2008, soil and water losses in various districts, counties and small watersheds of Nanjing were quantitatively analyzed, with a new method for “quantitative monitoring of soil and water loss”. Results show that: (1) during the period, the area of lands subjected to soil erosion light or over was averaged 858.5 km², losing a total of 206.4×10⁴ t of soil; and the soil erosion occurred mainly in hilly areas; (2) the soil erosion was characterized by annual and inter-annual variations; which show that soil erosion occurred mostly from Apr. to Aug.; and it was the most serious in 2003, the least in 2001, and the closest to the average of the 8 years; (3) spatial variation of the average soil erosion existed among the districts, towns, and small watersheds; in terms of total amount of soil loss, and areas of lands subjected to light and serious soil erosion, Jiangning District ranked first and was followed by Liuhe District; and Baijia Lake and Shangba River were the most serious in soil erosion among the small watersheds; (4) the effect of the efforts of Nanjing to control soil and water loss was very significant; The erosion modulus declined from moderate to light, and the total amount of soil loss; the area of the lands subjected to soil loss and the area of the lands in urgent need for control areas all significantly decreased; and the area of the lands where soil erosion control measures had been implemented and the area of the land covered by vegetation increased, thus significantly improving the eco-environment of Nanjing; (5) the analysis of the effect of the control of soil erosion indicated that the increase in vegetation coverage and the implementation soil erosion control measures are effective in controlling soil erosion.

Abstract:Abstract Soil bio-crust exists widely in semiarid and arid regions throughout the world, specially in desert area. An experiment on effects of simulated falling dust, litter and bio-inoculation on formation of soil crust in desert was carried out in 2006 in Horqin Sand Land to understand mechanism of soil crust formation in desert. Results show that (1) the falling dust obviously promoted development of soil crust, but no linear relationship was observed between the coverage and thickness of soil crust and amount of falling dust; (2) when little (100 g m^-2) in amount, litter enhanced the effect of falling dust on development of soil crust, but reversely inhibited the effect, when it was more; (3) bio-inoculation significantly enhanced the effect, particularly the inoculation of lichen in arid environment, and of moss in relatively humid environment; (4) crust coverage was sensitive to input of extragenous substances, while crust thickness did not vary much with change in kind and amount of the input and (5) compared with illuminated and arid environment, shaded and wet environment was more conducive to development of soil crust and enhancement of the effects of inputs on crust formation.

Abstract:The dumping site for copper mining tailings at Yangshanchong at Tongling city (Anhui Province) has been deserted for 20-years. The area is characterized by extremely high concentrations of heavy metals, poverty of nutrients, easy acidification and severe desertification. Biological soil crusts (BSCs), extensively existing on tailings is a major early stage of the ecological succession of the tailing ecosystem. The method of in situ acetylene reduction was applied to explore characteristics of biological nitrogen-fixation of algae, algae-moss and moss crusts on tailings. It was found that biological crusts significantly increased total nitrogen and lower Cu content in the tailings, and the nitrogen-fixing capability of the crusts varied sharply from type to type. Among the three types, the algae-moss type of crust was the highest in N₂ fixation rates, ranging between 1.32~8.78 kg hm^-2 a^-1, and followed by the algae type and the moss type, ranging between 4.36~30.39 kg hm^-2 a^-1 and between 0~16.34 kg hm^-2 a^-1, respectively, and followed a decreasing order of algae-moss, moss, and algae BSCs. N₂ fixation capacity of the BSCs varied with the season, too showing a decrease order of summer, spring, fall and winter. Besides, a negative line relationship was observed of the capacity with soil bulk density, NO₃^--N, and total Cu concentration and a positive one with pH, NH₄⁺-N, and water soluble organic carbon. On the whole, BSCs significantly enhanced total nitrogen content, and decrease total Cu concentration in tailings. The anomalous wet conditions experienced during the year of the study may have increased the temporal availability of soil mineral N and decreased N fixation rates. However, the presence of N fixation activity in all crusts analyzed their ability to survive at high Cu concentration, which may contribute to ecosystem resilience and recovery in areas under severe heavy metal stress.

Abstract:Soil salinization has become more and more severe in arid regions. Make an appropriate irrigation regimes to leaching soil salinity is a key scientific issue under drip irrigation in the silt loam soil in arid region. A 3-year field experiment was carried out to investigate the effects of different drip irrigation regimes on soil salinity distribution and cotton yield at Akesu agricultural ecosystem national scientific research station, Chinese Academy of Sciences. Throughout cotton growing season, the peak cure of soil salt under mulch moved downward with the increases of DIA (drip irrigation amount). The quantity of drip irrigation increased from 3 000 m³ hm^-2 to 4 800 m³⁺ hm^-2, peak value of soil salt moved downward from 35cm to 65cm. The results showed that the peak cure of soil salt under mulch decreased in the order 1.6 DIA>1.4 DIA>1.2 DIA>DIA after irrigation. At the same time, the peak cure of soil salt under mulch also moved downward with the increases of drip irrigation discharge rates for all treatments except 3.2 L h^-1 treatments because of the capability of infiltration of porosity of soil less than the drip irrigation discharge rate. The peak cure of soil salt under mulch decreased in the order 2.6 L h^-1>2.2 L h^-1>1.8 L h^-1>3.2 L h^-1 after irrigation. The soil salinity moved gradually from deep soil to surface soil and moved slowly from under mulch to inter-mulch simultaneously with elapse time. With the increasing of quantity of drip irrigation or drip irrigation discharge rates, seed yield presenting increased except 1.6 DIA and 3.2 L h^-1 treatment. Both water deficit and heavy irrigation will decrease the cotton yield, as well as the high and law drip irrigation discharge rate. Therefore, quantity of drip irrigation of 1.4 DIA and appropriate drip irrigation discharge rate of 2.6 L h^-1 was the best drip irrigation regimes for the higher cotton yield in the silt loam soil in arid region.

Abstract:In the red-soil hilly region, South China, severe soil erosion has made the region one of the zones of degraded ecosystem in China. To explore relationships between vegetation restoration models and amelioration of soil physical and chemical properties, and rational utilization of the land resources in the hilly region, effects of vegetation restoration models using different vegetations, such as grasses, orchard, fruit treess + grasses, fruit treess + grasses & crops and fruit treess + crops, on soil physical and chemical properties were analyzed with the gray incidence analysis method. Results show that the effects on soil properties varied from vegetation to vegetation and from model to model. The model that had Paspalum notatum flugge covering the whole plot was the optimal in integrated effect, and followed by the models that had fruit trees + crops, fruit treess + grasses & crops and fruit trees + grasses. And the models with vegetation interplanted horizontally were better than those vertically, and overall coverage than ribbon coverage. In restoring vegetation in severely eroded hilly areas, South China, it is advisable to take the model of overall coverage of Paspalum notatum flugge and the model of horizontal interplantation of fruit trees and crops into priority consideration for extension in the hilly regions, South China.

Abstract:Based on a long-term stationary experiment on problems in continuous monocropping of peanut from 1996 to 2008 in the Ecological Experimental Station of Red Soil, Chinese Academy of Sciences, effects of fertilization on plant growth, yield and incidence of soil-borne diseases of peanut were studied. Soil-borne disease occurred in all the fields under continuous monocropping in 2008, while the incidence was lower in Treatments M (organic manure), BM (organic manure + effective microorganisms) and BMT (organic manure + effective microorganisms + trace materials) than in Treatments F (chemical fertilizer) and TF (chemical fertilizer + trace materials) in the same year. No matter what fertilizer was applied, continuous monocropping decreased height, weight and yield of peanut, and the effect became more severe over time. Peanuts were obviously better in growth and yield in Treatments M, BM and BMT than in Treatments F and TF. Application of organic manure and effective microorganisms decreased the incidence of soil-borne diseases, deferred the declining trend of pod yield and improved plant growth, while the application of microelements did not have such effects. A significant negative correlation between pod yields and disease incidence indicated that soil-borne diseases is one of the main obstacles to continuous monocropping of peanut.

Abstract:Abstract: Samples of a variety of environmental media, such as soil (n=151), groundwater (n=9), air (solid PM₁₀ and gaseous PCBs, n=4), vegetable (n=38) and rice (n=95) were collected in a typical area for analysis of concentrations of PCBs and Cd. The carcinogenic exposure dose and risk of PCBs and Cd to people living in that environment and being exposed to the multi-media through multi-pathway were assessed, using the carcinogenic risk assessment model of USEPA. Contribution rate of the pollutants to the carcinogenic risk was analyzed. And main carcinogenic contaminants, exposure pathways and the greatest contributor among the environmental media to the carcinogenic risk were screened out. Results show that all the investigated media were heavily polluted by PCBs and Cd. The concentration of Cd in the vegetable and rice reached 130 and 17 times the threshold value for the pollutants in the food of China, respectively. Both PCBs and Cd in the groundwater were high in over-limit ratio. The gaseous PCBs and the PM10-borned PCBs and Cd were all higher in this area than in other areas in and out of the country. The assessment of carcinogenic exposure dose indicates that the total carcinogenic exposure dose of PCBs and Cd is 6.8 and 6.1 times as high as the acceptable daily intake, respectively. The total carcinogenic risk was 1.1*10_-3, much higher than the acceptable carcinogenic risks stipulated by other countries and regions. The analysis of carcinogenic contribution rate suggests that oral ingestion was the main pathway of exposure to the carcinogenic risk. Vegetable, rice and groundwater were the main sources of carcinogenic PCBs and Cd in this area.

Abstract:Ten sampling sites were set in the various districts of Kaifeng City. Surface soil samples (0～15 cm) were collected from these sites in 1994 and 2006, separately. The samples were analyzed with a GF-AAS (graphite furnace atomic absorption spectrophotometer) for concentrations of Pb and Cd, CAAS (cold atomic absorption spectrophotometer) for Hg, and SDS (silver diethyldithiocarbamate spectrophotometer) for As. Heavy metal pollution of the soil was evaluated using geoaccumulation indexes. It was found that Cd and Hg accumulated significantly in the soil, becoming the main pollutants, and the former came mainly from the refuses discharged from Zinc Mill of Kaifeng and some other chemical factories, and the latter from coal combustion. Heavy metal pollution of the soil tended to be more severe in degree after the soil was turned from farmland into the urban lands, and could be effectively mitigated when land use of the urban soils was reduced in intensity and managed better. Change of the servitude of the same piece of land might also lead to variation of the heavy metal pollution of the soil in degree. Along with the rapid economic growth characterized by increasing GDP per capita, population density, coal wastage, quantity of civil automobiles, and tourist quantity, etc. from 1994 to 2006, soil pollution with heavy metals in Kaifeng City become heavier with the geoaccumulation index increased from 0.98 to 1.13.

Abstract:A total of 413 soil samples and crops thereupon were collected from fields under four typical types of land use, i.e. vegetable field, paddy field, dry land and orchards, for analysis to explore characteristics of As accumulation in the soils and crops in the four different types of fields and its risk to human health. Results show that in the paddy soil arsenic concentration was in the range of 5.69～148.5 mg kg^-1, indicating the soil was the highest in As accumulation degree, whereas, in the orchards soil, it was in the range of 3.29～24.7 mg kg^-1, indicating the soil was the lowest in As accumulation degree. However, soil As variation coefficients in all the soils were beyond 0.5, being moderate in variability, regardless land use type Soil arsenic concentrations varied sharply between sampling sites. As concentrations in crops also varied greatly as affected by land use. On average, it reached as high as 2.15 mg kg^-1 in oil crops, and was the lowest, being 0.032 mg kg^-1 in both dry land crops and fruits. Cluster analysis of the crop arsenic enrichment coefficients show that the crops in the study area could be divided into four groups. Oil crops were in Group I, the highest in crop arsenic enrichment coefficient, rice in Group II, leaf vegetables in Group III and fruits, gourd, bean and root vegetables, and grain crops in Group IV, being the lowest in crop arsenic enrichment coefficient. Based on JECFA-recommended ADI value and dietary structure of the residents in the study area, hazard quotients of soil arsenic to human health were analyzed, showing an order of paddy > vegetable field > dry land > orchard. Health risk posed by As in paddy soil was quite great, as the diet of rice led to ADI of As as high as to 0.0043 mg body^-1 day^-1 and the people living in the study area were faced with high health risk. Active measures should be taken to readjust the cropping structure in the study area and to manage and remedy As-polluted soils.

Abstract:Organo-mineral complexes play an important role in soil. Clay mineral-polysaccharide complex is a precursor, contributing to the formation of clay Organo-mineral complexes, but its specific functions remain unclear. Montmorillonite-xanthan complex was prepared and analyzed for its structure with X-diffraction and spectra at various depths with a Fourier transform infrared photoacoustic spectroscop (FTIR-PAS) that has the function of in-situ step-scanning. Results show that the interaction between montmorillonite and xanthan occurred mainly on the surface of montmorillonite, and subsequently formed an interfacial layer, which featured a distinct infrared photoacoustic spectrum; the formed complex demonstrated stronger water-holding capacity than montmorillonite, and its surface differed significantly from its subsurface in spectrum, and the interfacial layer of the montmorillonite-xanthan complex was approximately 2.05~6.47 µm thick according to the step-scanning with FTIR-PAS.

Abstract:A long-term stationary field experiment on nutrient balance for farming ecosystem in the Fengqiu National Agro-ecological Experiment Station was made use of to investigate effects of fertilization, balanced or unbalanced, on microbial biomass, enzymatic activities, and soil basal respiration as well as nutrient uptake of maize plants in a fluvo-aquic soil. The experiment was designed to have five treatments: fertilizer NPK, NP, PK, NK, and CK (without fertilization). The root biomass, straw biomass, grain yield, and total uptakes of N, P, K of maize plants were all greatly increased in Treatment NPK, and were also significantly increased in Treatment NP, but were not significantly affected in Treatment PK or NK. In the same treatment, straws and roots were similar in nutrient content, while grains were relatively higher in total N and total P contents of, but lower in total K. Compared to Treatment NPK (balanced fertilization), the other treatments, lacking one or other nutrient, showed significant decrease in the nutrient in question and/or significant increase in the other nutrients in maize plants, and differed betweenthe treatments in nutrient distribution among roots, straws, and grains. In addition, in all the treatments that had P (NPK, NP, PK), the soils were higher in microbial biomass C, N, P, activity of dehydrogenase, invertase, urease, and alkaline phosphatase, microbial metabolic activity, and basal respiration, but significant lower in microbial metabolic quotient. However, P-deficienct treatment (NK) fertilization did not show any significant effects on these soil biological parameters, except for a significant increase in urease activity. The findings demonstrated the role of P, as well as balanced fertilization with N, P, and K in promoting soil microbial growth and metabolic activity, as well as enhancing crop growth and nutrient uptake.

Abstract:A project was carried out to study a basic EDTA method for measuring soil organic matter, and correlations of basic EDTA organic matter with Tyurin organic matter, and with plant N uptake, and application of the method in soil testing and nitrogen fertilizer recommendation. Lab analysis of 50 soil samples each for red soil, fluvo-aquic soil and black soil, typical of the soils in China revealed that basic EDTA organic matter was highly correlated with Tyurin organic matter, being 0.9345 (p>0.01) in correlation coefficient and forming a linear regression equation, i.e. Tyurin organic matter （g kg^-1） = 3.3265* basic EDTA organic matter（g kg^-1）+ 6.9389. Pot experiments using 28 major types of soils on N deficiency and plant N uptake indicated that basic EDTA organic matter was significantly correlated with plant N uptake, and its the correlation coefficient （R = 0.628，p>0.01）was higher than that of the correlation of Tyurin organic matter and soil total N with plant N uptake. Although the correlation coefficient between basic EDTA organic matter and plant N uptake of plant was not as high as that between soil mineral N after 2 weeks of aerobic incubation and plant N uptake, basic EDTA organic matter is extracted soil humic matter and can be fast determined with photometry. Therefore, the EDTA method for soil organic matter is a better means for estimating soil N supplying capacity and worth recommending to the laboratory for use in the soil testing and N fertilizer recommendation.

Abstract:Fractionation of a soil sample for soil aggregates of different size grades (>2, 2～0.25, 0.25～0.053 and < 0.053 mm) was carried out using the wet screening method for the study on effects of application of corn stalks on quantity and structural characteristics of humic acid in aggregates of the soil incubated indoors at a constant temperature of 25℃. Results show that after the application and incubation, aggregates of size fractions 2～0. 0.25 mm and >2 mm turned out to be dominant in the soil accounting for 51.41% and 34.12%, respectively, on average. Their total carbon content ranged in 10.15～25.74 g kg^-1, and their absolute HA content in 4.06～5.79 g kg^-1, obviously higher than what was in the control, and the differences got bigger and bigger with the application rate of corn stalks; However, the C/H and high/medium temperature exotherm ratios were lower in all the treatments than in the control, and negatively related to application rate of corn stalk, which suggests that higher corn stalk application rate makes HA molecules less condensed and simpler in structure.

Abstract:Soil organic carbon and total nitrogen are of crucial importance to soil fertility, crop yield, agricultural sustainable development and global carbon and nitrogen cycling. To evaluate effects of tillage and rotation on storages of soil organic carbon (SOC) and total nitrogen (TN) in a black soil in Northeast China, an 8-year stationary field experiment was conducted in a black soil field in Dehui, Jilin. The experiment was designed to have three tillage treatments and two cropping treatment, i.e. no-tillage (NT), ridge tillage (RT) and moldboard plow (MP), and corn-soybean rotation (CS) and continuous corn (CC). Variation of SOC and TN in various soil layers were monitored by sampling and calculated using the method of equivalent mass for soil organic matter. Results show that under the CS system, both SOC and TN decreased somewhat in Treatment MP, but significantly increased in Treatment NT in the 0-5cm soil layer. However, the increase in SOC in NT was offset by the loss of SOC in the sub-surface layer, leaving the stock of SOC unchanged in the soil. Treatment RT significantly increased SOC and TN in the 0-5 cm and 5-10 cm layers, or by 4.9% and 10.7%, respectively, in the 0-30 cm soil layer. Under the CC system, SOC and TN stocks increased in Treatments MP and NT, and the increase in Treatment NT was 3.2 times as high as that under the CS system. C/N ratios in all the treatments declined, and particularly in Treatment RT, it dropped form 12.05 to 11.04 in the 0～5 cm soil layer, which was 3.2 and 2.8 times as great as in Treatments NT and MP, respectively, in magnitude of the drop. It is learnt from the above findings that neither MP nor NT is efficient in promoting SOC sequestration under corn-soybean rotation in black soil with a mid-layer heavy and clayey in texture and poor in drainage whereas RT promotes SOC and TN accumulation, which is not only conducive to improving soil fertility, but also effective to turn farmland soil from source to sink for CO2. Compared with the corn-soybean rotation system, continuous corn cropping is more favorable to SOC and TN sequestration.

Abstract:A study was conducted on biological nitrogen fixation and plow-down of green manure crops on rice yield and nitrogen dynamics in paddy field in the Taihu Lake Region, using the ¹⁵N natural abundance method. Results show that Chinese milk vetch and faba bean biologically fixed about N 32.8 and 66.8 kg km^-2, respectively, in their growth season. Plow-down of green manures as a nitrogen source basically satisfied N requirements of the subsequent rice crop. The application of N 120 kg km^-2 in addition to the plow-down could not only ensure higher rice grain yield, but also reduce the application of chemical fertilizer N by 45% to 55% compared to the common dosage in this region. The treatment of plow-down alone was significantly lower than the treatment of plow-down plus N fertilizer in concentrations of NH₄⁺-N, NO₃^--N and TN of the soil solution in the plowed layers during the whole growth season. The treatment of plow-down of faba bean was higher than the treatment of plow-down of Chinese milk vetch in TN concentration in the soil solution. Additional application of chemical nitrogen rendered the concentrations of NH₄⁺-N, NO₃^--N and TN in soil solution a rising tendency, but the effects were not much different between treatments of different application rates. Nitrogen leaching in paddy fields using green manures as the only nitrogen source for rice crop was much lower. With the application of chemical nitrogen, nitrogen leaching increased. The leaching of NH₄⁺-N、NO₃^--N and TN into deep soil water was especially higher in the treatment of 300 kg N km^-2 than in the treatment of N 0~240 kg km^-2.

Abstract:Members of Sphingomonas genus played a key role in the biodegradation of polycyclic aromatic hydrocarbons (PAHs). However, little was available in the literature about diversity and population structure of genus Sphingomonas in petroleum-contaminated soils, and relationships between Sphingomonas and PAHs based on direct detection Sphingomonas strains with Sphingomonas genus-specific primers. In this paper, total soil DNA from the soil in Shenfu irrigation zone were amplified with newly designed Sphingomonas genus-specific primer set 732f-982r and then these amplified DNA fragments were separated by DGGE for analysis of genetic diversity of Sphingomonas in the soil of the irrigation zone. Results indicate that the newly developed primer set 732f-982r could be used for specific detection of strains belonging to the genus Sphingomonas. When PAHs contamination of the soil is at a low level, i.e. less than 5 mg kg^-1, the diversity of Sphingomonas increased with rising PAHs concentration; but when the initial concentration of PAHs in lab incubation experiment is relatively high, the diversity of Sphingomonas decreased. Different concentrations of total petroleum hydrocarbons (TPH) lead to difference in Sphingomonas population, and soils the same in TPH contamination level are similar in Sphingomonas population.

Abstract:PGPR bacterial manure is getting more and more popular in crop and vegetable production, but it has not yet been specialized enough for use in flue-cured tobacco production. In this study, the PGPR bacterial manure used was prepared out of the antibiotic bacteria, nitrogen fixing bacteria, phosphate-dissolving bacteria, and potassium-dissolving bactera screened and isolated from flue-cured tobacco rhizosphere. The experiment was laid out in an experiment field of yellow brown soil, using Yuanyan 89, a common tobacco cultivar. The application rate of the PGPR bacterial manure was set at 30 kg hm^-2 when tobacco seedlings was transplanted to the plots randomly arranged. The experiment had four treatments, viz., Treatment I, 100% NPK + PGPR (conventional NPK application rate for tobacco + PGPR bacterial manure), Treatment II, 80% NPK + PGPR (80% the conventional NPK application rate + PGPR), Treatment III, 100% NPK (Conventional NPK application rate) and Treatment IV, 80% NPK (80% of the conventional NPK application rate). Results show that in the PGPR treatments the count of actinomyces in tobacco rhizospheres was reduced by 17% to 27% (p＜0.05), while the content of microbial biomass carbon increased by 3% to 16% during the whole growth period; the count of phosphate-dissolving bacteria at the budding stage increased by 24% (p＜0.05); and the quality of cured leaves was better, as compared to those in the non-PGPR treatments. Comparison between Treatment II and Treatment IV revealed that application of PGPR increased the availability of N, K, Cu, Zn, B, and Fe in tobacco rhizosphere at budding stage by 4.46%~28.87%, while decreased the availability of P, Ca, Mg, and Mn by 2.63%~30.19%, however, it improved yield and net production value of the flue-cured tobacco by 7.53% and 30.05%%, respectively. Compared with Treatment III, Treatment II increased yield and net production value of the flue-cured tobacco by 4.52% and 24.68%. The findings suggest that the use of PGPR bacterial manure is an effective approach to reduction of the application rate of chemical fertilizers in tobacco production and sustainable production of quality and hazard-free flue-cured tobacco leaves.

Abstract:Abstract Bioavailability and ecological effects of selenium (Se) in soil depend on its species. Samples of 15 kinds of soils were collected in China for analysis of Se species using a sequential extraction method proposed by Qu in 1997. Se in soil may be partitioned into: 1) soluble Se (SOL-Se), 2) exchangeable Se and Se bound to carbonate(EX-Se), 3) Se bound to Fe–Mn oxides(FMO-Se), 4) Se bound to organic matters(OM-Se), 5) residual Se(RES-Se). Relationship between soil physico-chemical properties and Se species were determined with path analysis on Amos 18.0. Results show that OM-Se dominated in all the soils, except for black soil from Heilongjiang and red soil (in paddy field and upland) from Jiangxi where RES-Se did. SOL-Se accounted for only 0.4%~14.6% of the total Se. EX-Se and OM-Se were in significant positive correlation with RES-Se. However, no significant correlations of SOL-Se and FMO-Se with other Se species were observed. Path analysis indicates that organic matter negatively affected FMO-Se, while positively affected all other species. Amorphous iron showed no effect on SOL-Se, but it did stronger effect on the other four Se species than organic matter did. Except for SQL-Se, organic matter and amorphous iron had the strongest impact on OM-Se and RES-Se, respectively. pH and clay influenced Se speciation via their negative or positive effect on organic matter and amorphous iron, respectively. To conclude, organic matter and amorphous iron are two decisive factors affecting Se partition in soil. Nevertheless, the effects of pH and clay are far from negligible.

Abstract:The Bayesian maximum entropy (BME) approach has emerged in recent years as a new spatio-temporal geostatistics methods. By capitalizing on various sources of information and data, BME introduces an epistemological framework which produces predictive maps that are more accurate and in many cases computationally more efficient than those derived with traditional techniques. It is a general approach that does not need to make assumptions regarding linear valuation, spatial homogeneity or normal distribution. BME can integrate a priori knowledge and soft data without losing any useful information they contain and improve accuracy of the analysis. This paper first introduces the basic theory of BME and stages of BME estimation, and then briefly describes its development and application in soil and environmental sciences. Finally the application of this method is also summarized and prospected. After years of development and practice, the BME method has been proved to be a mature outstanding approach, which has a broad prospect of application in evaluation of resources and environment.

Abstract:Cadmium contamination of soil has been a world-wide concern in decades. Cadmium activity may vary sharply in submerged soils but the mechanisms so far found underlying the variation have remained conflicting and ambiguous because of the huge variety of the submerged soils, the complexity of their properties and the diversity of the external factors they are exposed. Various factors, such as Fe and Mn oxides, carbonates, particle organic matters, sulfide, DOM, anions (mainly Cl^- and SO₄^2-), cations (such as Al³⁺, Ca²⁺, Mg²⁺, Na⁺, etc.) and so on, and their controlling mechanisms not only perplex the soil chemistry of Cd, but also hamper the control and remediation of Cd polluted soils. At the oxic-anoxic interface of flooded soils, the variation of Cd activity is largely controlled by some chemical processes, such as adsorption-desorption, precipitation-dissolution, complexation and chelation. The paper reviews in detail these processes and mechanisms controlling the variation of Cd activity in flooded soils. At the same time, some important issues and directions are set forth for further research.

Abstract:Earthworm and Arbuscular mycorrhizal fungus are both among the beneficial soil biota. They play important roles in nutrient availability in soil and to plant. This article reviewed effects of earthworms on feeding, infection and colonization of AM fungus, latest advancement in research on interaction between AM fungus and earthworms and its mechanism, and their synergic role in plant nutrition and growth and remediation of heavy metal polluted soils, in the hope that the review might serve as a basis future study in this field.progress about interaction between AM fungi and earthworms. Meanwhile, combined effects of AM fungi and earthworms on plant performance, in order to provide basis for further research and development. The aim of this paper was to discuss the effects and mechanisms of interactions between AM fungi and earthworms. Future study perspectives were also given.

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