Most downloaded articles
1995, 32(2):117-125.
Abstract:
Chemical fertilizer Industry of China has already made great progress since 1949. By 1993, the total fertilizer production capacity that has been built was 27.8 Mt, including 20.9 Mt of N, 6.73 Mt of P2O5, and 200 thousand t of K2O. The accumulated ammount of fertilizer nutrients applied into soil during 1949-1993 was 380.6 Mt of which 90 Mt was imported accounting for 23.6% of the total. It is estimated that by the end of the century 42 Mt of fertilizer would be needed to meet the requirement of agricutural production in China. It's supply should mainly rely on China's own Industry. The average nutrients content of fertilizer of China is 26.5% now which is still much lower than the world average (about 40%).So China should pay even greater attention to the production of higher grade fertilizers. A few low grade fertilizers like single superphosphate and NH4HCO3 will still be important sources in Ghina in the near future. Improvement of technigue of fertilizer production in order to lower the energy comsumption and better equipment for the industry are also the main proints needed to. solve.
Chemical fertilizer Industry of China has already made great progress since 1949. By 1993, the total fertilizer production capacity that has been built was 27.8 Mt, including 20.9 Mt of N, 6.73 Mt of P2O5, and 200 thousand t of K2O. The accumulated ammount of fertilizer nutrients applied into soil during 1949-1993 was 380.6 Mt of which 90 Mt was imported accounting for 23.6% of the total. It is estimated that by the end of the century 42 Mt of fertilizer would be needed to meet the requirement of agricutural production in China. It's supply should mainly rely on China's own Industry. The average nutrients content of fertilizer of China is 26.5% now which is still much lower than the world average (about 40%).So China should pay even greater attention to the production of higher grade fertilizers. A few low grade fertilizers like single superphosphate and NH4HCO3 will still be important sources in Ghina in the near future. Improvement of technigue of fertilizer production in order to lower the energy comsumption and better equipment for the industry are also the main proints needed to. solve.
2 Effects of application rates of controlled release fertilizers on cotton growth and soil fertility
2014, 51(2):295-305.
DOI: 10.11766/trxb201305200245
Abstract:
A field experiment of controlled release fertilizers (CRFs) on cotton was carried out to study effects of application rate of CRFs on cotton (Guokang 12) growth and soil fertility with the application of common compound fertilizers (CCFs) as control for comparison. Results show that CRFs significantly increased plant height, culm diameter, leave area and the numbers of fruit spurs and bolls of the cotton. When N 75 kg hm-2 and N 150 kg hm-2 was applied, yield of the cotton in Treatment CRFs was 18.9% and 13.6% higher than that in CK (CCFs), respectively. Besides, CRFs also significantly increased the content of NO3−-N in the soil of the 0~40 cm soil layer, but didn’t affect much the content of NH NO4 -N in the soil. No significant difference was observed in content of available P and K between Treatments CRFs and CCFs.
A field experiment of controlled release fertilizers (CRFs) on cotton was carried out to study effects of application rate of CRFs on cotton (Guokang 12) growth and soil fertility with the application of common compound fertilizers (CCFs) as control for comparison. Results show that CRFs significantly increased plant height, culm diameter, leave area and the numbers of fruit spurs and bolls of the cotton. When N 75 kg hm-2 and N 150 kg hm-2 was applied, yield of the cotton in Treatment CRFs was 18.9% and 13.6% higher than that in CK (CCFs), respectively. Besides, CRFs also significantly increased the content of NO3−-N in the soil of the 0~40 cm soil layer, but didn’t affect much the content of NH NO4 -N in the soil. No significant difference was observed in content of available P and K between Treatments CRFs and CCFs.
2015, 52(2):431-439.
DOI: 10.11766/trxb201404300207
Abstract:
In plotting a 1:50 000 soil map of China, color matching of soil types is required to manifest characteristics of the distribution of soil types or soil categories, higher in soil classification level than soil type, and to demonstrate, as well, differences between soil categories, low in soil classification level, like soil genera. As in soil classification, China has a huge number of low-grade soil taxons, and a 1:50 000 national soil map of China consists of at least 20 000 rolls of sectional soil maps, the use of the conventional manual coloring method in soil mapping is not only very low in efficiency, but also finds it hard to keep all these rolls of soil maps consistent in color. To solve this technical problem, a soil type color matching model (SCO-Model) was developed, based on the designing concept of human-computer interaction and the inter-roll similar color matching method, The SCO-Model consists of three major components: i) a multi-level management color table, ii) QC table for user to define color matching unit Q of soil types and 3 similar color systems or color groups for each Q, iii) five Sub-models, including a statistical analysis model for soil types, a threshold determination model for unit Q, a color selection model for unit Q, a calculating color-code model, and a browsing map model. Results show that the SCO-Model can not only manifest the characteristics of the overall distribution of soils in a region, and the differences between soil types, but also realize rapid intellectural color matching of soil types in large scale soil mapping.
In plotting a 1:50 000 soil map of China, color matching of soil types is required to manifest characteristics of the distribution of soil types or soil categories, higher in soil classification level than soil type, and to demonstrate, as well, differences between soil categories, low in soil classification level, like soil genera. As in soil classification, China has a huge number of low-grade soil taxons, and a 1:50 000 national soil map of China consists of at least 20 000 rolls of sectional soil maps, the use of the conventional manual coloring method in soil mapping is not only very low in efficiency, but also finds it hard to keep all these rolls of soil maps consistent in color. To solve this technical problem, a soil type color matching model (SCO-Model) was developed, based on the designing concept of human-computer interaction and the inter-roll similar color matching method, The SCO-Model consists of three major components: i) a multi-level management color table, ii) QC table for user to define color matching unit Q of soil types and 3 similar color systems or color groups for each Q, iii) five Sub-models, including a statistical analysis model for soil types, a threshold determination model for unit Q, a color selection model for unit Q, a calculating color-code model, and a browsing map model. Results show that the SCO-Model can not only manifest the characteristics of the overall distribution of soils in a region, and the differences between soil types, but also realize rapid intellectural color matching of soil types in large scale soil mapping.
2004, 41(3):456-461.
DOI: 10.11766/trxb200309010320
Abstract:
In order to understand the role of microbial communities in different environments it is essential to have knowledge of functions and functional diversity of microbial communities.However, the quant itative description of microbial communities is one of the most difficult tasks facing microbial ecologists.Now the BIOLOG redox technique proposes a simple and quick method for studying soil microbial community function diversity, based on the community-level carbon source utilization patterns.But BIOLOG is also a culture-based method, and the presentation of metabolic diversity patterns doesn't necessarily reflect the functional diversity of the soil microbial communities.Consequently, there are many problems as well as benefits using the approach, and a series of skills are needed for the application.The application of BIOLOG to the study on soil microbial community functional diversity is summarized in this paper, including theories, procedures, problems, and countermeasures during the application.The problems worthy of further research are also put forward.The objective of the study is to accelerate understanding how to apply BIOLOG properly to the study on soil microbial community functional diversity and provide a scientific foundation and theoretical guide for further research of the subject correctly.
In order to understand the role of microbial communities in different environments it is essential to have knowledge of functions and functional diversity of microbial communities.However, the quant itative description of microbial communities is one of the most difficult tasks facing microbial ecologists.Now the BIOLOG redox technique proposes a simple and quick method for studying soil microbial community function diversity, based on the community-level carbon source utilization patterns.But BIOLOG is also a culture-based method, and the presentation of metabolic diversity patterns doesn't necessarily reflect the functional diversity of the soil microbial communities.Consequently, there are many problems as well as benefits using the approach, and a series of skills are needed for the application.The application of BIOLOG to the study on soil microbial community functional diversity is summarized in this paper, including theories, procedures, problems, and countermeasures during the application.The problems worthy of further research are also put forward.The objective of the study is to accelerate understanding how to apply BIOLOG properly to the study on soil microbial community functional diversity and provide a scientific foundation and theoretical guide for further research of the subject correctly.
2008, 45(5):915-924.
DOI: trxb10.11766/200805200517
Abstract:
Nutrient use efficiency is an important index not only for fertilizer recomm endation on the field scale but also for forecasting fertilizer demand on the regional and national scales,however,exact nutrient use efficiencies of the major cereal crops in China are not well known yet.In this paper,data from 1 333 field experiments were collected and used for analysis and evaluation of partial factor productivity(PFP),agronomic efficiency(AE),apparent recovery efficiency (RE)and physiological efficiency(PE)of these crops.Results show that AEN of rice,wheat and maize was 10.4 kg kg-1,7.99 kg kg-1 and 9.80 kg kg-1,respectively,and REN of rice,wheat and maize was 28.3%,28.2% and 26.1%,respectively,obviouslymuch lower than the world's average,whichis attributed to over-use of chemical fertilize,rignorance of contribution of nutrients from the environment and the soil, failure to bring crop yield potential into full play, and inability to inhibit nutrient losses effectively.
Nutrient use efficiency is an important index not only for fertilizer recomm endation on the field scale but also for forecasting fertilizer demand on the regional and national scales,however,exact nutrient use efficiencies of the major cereal crops in China are not well known yet.In this paper,data from 1 333 field experiments were collected and used for analysis and evaluation of partial factor productivity(PFP),agronomic efficiency(AE),apparent recovery efficiency (RE)and physiological efficiency(PE)of these crops.Results show that AEN of rice,wheat and maize was 10.4 kg kg-1,7.99 kg kg-1 and 9.80 kg kg-1,respectively,and REN of rice,wheat and maize was 28.3%,28.2% and 26.1%,respectively,obviouslymuch lower than the world's average,whichis attributed to over-use of chemical fertilize,rignorance of contribution of nutrients from the environment and the soil, failure to bring crop yield potential into full play, and inability to inhibit nutrient losses effectively.
2018, 55(2):261-272.
DOI: 10.11766/trxb201711240485
Abstract:
The agricultural soil in China has been widely polluted by heavy metals and the regional contamination is serious. The experience on soil remediation in developed countries is significantly instructive for farmland protection in China. The heavy metal pollution of farmlands in China faces great challenges including spatial heterogeneity of heavy metal accumulation, various enrichment characteristics depending on soil types and crop, soil acidification, loss of soil trace elements, unreasonable development patterns, significant input of heavy metal into soil, poor correlation between the heavy metal concentration in soil and crop plants, inadvisable remediation techniques, and lack of long-term risk control measures. Responses to these problems, we proposed a soil prevention and control system to promote the remediation of contaminated cropland in China, which mainly focused on pollution prevention, and take prior protection as well as risk control as basic course. Based on this system, the soil pollution prevention and control work can be implemented through systematically procedures including soil environment investigation, pollution source control, risk assessment and classification management, and the derivation of soil quality threshold.
The agricultural soil in China has been widely polluted by heavy metals and the regional contamination is serious. The experience on soil remediation in developed countries is significantly instructive for farmland protection in China. The heavy metal pollution of farmlands in China faces great challenges including spatial heterogeneity of heavy metal accumulation, various enrichment characteristics depending on soil types and crop, soil acidification, loss of soil trace elements, unreasonable development patterns, significant input of heavy metal into soil, poor correlation between the heavy metal concentration in soil and crop plants, inadvisable remediation techniques, and lack of long-term risk control measures. Responses to these problems, we proposed a soil prevention and control system to promote the remediation of contaminated cropland in China, which mainly focused on pollution prevention, and take prior protection as well as risk control as basic course. Based on this system, the soil pollution prevention and control work can be implemented through systematically procedures including soil environment investigation, pollution source control, risk assessment and classification management, and the derivation of soil quality threshold.
2003, 40(5):724-730.
DOI: 10.11766/trxb200203130513
Abstract:
Under a long-term experiment on different fertilization treatments, the contents of water-soluble organic carbon (WSOC) in the soil ranged from 32.1 to 45.5 mg kg-1, following the order of NPK+4500 kg rice straw>NPK+2250 kg rice straw>CK>NPK. The percentages of WSOC to total soil organic carbon (TOC) ranged from 0.15% to 0.19%, following the order of NPK+4500 kg rice straw≈CK>NPK+2250 kg rice straw>NPK. The contents of WSOC had significantly positive correlations with both TOC and soil microbial biomass carbon(SMBC). 13C-NMR results showed that WSOC were mainly com posed of carbohydrates carbon, carboxyl carbon and long-chain aliphatic carbon. Under different fertilization treatments, the coefficients of variation (CV) of WSOC/TOC and SMBC/TOC were lower than those of their absolute contents in soil. Furthermore, the CV of WSOC/TOC was higher than that of SMBC/TOC. The percentage of WSOC to TOC was a good indicator of the quality of soil organic matter under different fertilization treatments.
Under a long-term experiment on different fertilization treatments, the contents of water-soluble organic carbon (WSOC) in the soil ranged from 32.1 to 45.5 mg kg-1, following the order of NPK+4500 kg rice straw>NPK+2250 kg rice straw>CK>NPK. The percentages of WSOC to total soil organic carbon (TOC) ranged from 0.15% to 0.19%, following the order of NPK+4500 kg rice straw≈CK>NPK+2250 kg rice straw>NPK. The contents of WSOC had significantly positive correlations with both TOC and soil microbial biomass carbon(SMBC). 13C-NMR results showed that WSOC were mainly com posed of carbohydrates carbon, carboxyl carbon and long-chain aliphatic carbon. Under different fertilization treatments, the coefficients of variation (CV) of WSOC/TOC and SMBC/TOC were lower than those of their absolute contents in soil. Furthermore, the CV of WSOC/TOC was higher than that of SMBC/TOC. The percentage of WSOC to TOC was a good indicator of the quality of soil organic matter under different fertilization treatments.
2018, 55(6):1313-1324.
DOI: 10.11766/trxb201805240172
Abstract:
Microbial interspecies electron transfer (IET) refers to the electron exchange between electron-donating microorganisms and electron-accepting microorganisms that forms a syntrophic growth relationship between the two thus enabling the two to jointly accomplish a certain metabolic process that no single microorganism can do. Moreover, it also plays a significant role in biogeochemical processes, such as degradation of organic matter, production of bioenergy and reduction of greenhouse gas emission. IET could be sorted into direct IET (DIET) and indirect or mediated IET (MIET). DIET occurs when there is a biological electrical connection and a difference in voltage potential, whereas MIET relies on diffusion of redox carriers driven by concentration gradients. Generally MIET needs hydrogen, formate or flavin as electron carrier, while DIET is found done directly through nanowire (e-pili), redox protein or conductive particles. Interspecies hydrogen/formate transfer, one type of MIET, occurs commonly in methanogenic microbial community, such as S organism and Methanobacterium ruminantium, Desulfovibrio vulgaris and Methanosarcina barkeri. In addition, sulfide, L-cysteine and AQDS can act as electron shuttles mediating electron transfer between microorganisms, such as Desulfuromonas acatoxidans and Prosthecochloris aestuarii. However, electron transfer between Geobacter species so far has only been documented to be direct: by way of e-pili and c-type cytochromes. Either of these Geobacter cells short of biological connections, such as e-pili and (or) cytochromes, can not get syntrophically related. Nevertheless, with the mediation of conductive materials, such as activated carbon and biochar, e-pili would become less functional during the process of DIET since syntrophic partners could exchange electrons via these conductive carbon materials. Moreover, conductive mineral magnetite can substitute for outer-membrane c-type cytochrome in its role. Mutant strain of G. sulfurreducens that is deficient in OmcS cannot co-culture with G. metallireducens, but with the addition of magnetites they can exchange electrons successfully. The discovery of DIET has changed the tradition gnosia that microbial syntrophic metabolism would not occur without energy carriers, such as hydrogen and formate, and has opened up a new scientific perspective for understanding biogeochemical processes, such as circulation of C/N/S, emissions of greenhouse and degradation of pollutants. The core of microbial IET is electron transfer between microbes. Further studies should be done on mechanism of IET and new effective IET microorganisms in order to put IET into practical engineering application. However, the researches on tmechanism of IET between microbes, at present, are still in their preliminary stage and so have a number of problems to be solved, for example, how exactly electron transfer occurs between microorganisms, whether there is any microorganism more IET efficient, and if there is any method that can more economically and efficiently accelerate IET, etc. In this review, the mechanisms of MIET is summarized, meanwhile, the three mediating mechanisms for DIET are expounded emphatically. Representative microbes participating in IET are introduced. Potential applications of IET to environment processes such as methane-producing anaerobic digestion, anaerobic methane oxidation and dechlorination are proposed and directions of future researches on IET discussed.
Microbial interspecies electron transfer (IET) refers to the electron exchange between electron-donating microorganisms and electron-accepting microorganisms that forms a syntrophic growth relationship between the two thus enabling the two to jointly accomplish a certain metabolic process that no single microorganism can do. Moreover, it also plays a significant role in biogeochemical processes, such as degradation of organic matter, production of bioenergy and reduction of greenhouse gas emission. IET could be sorted into direct IET (DIET) and indirect or mediated IET (MIET). DIET occurs when there is a biological electrical connection and a difference in voltage potential, whereas MIET relies on diffusion of redox carriers driven by concentration gradients. Generally MIET needs hydrogen, formate or flavin as electron carrier, while DIET is found done directly through nanowire (e-pili), redox protein or conductive particles. Interspecies hydrogen/formate transfer, one type of MIET, occurs commonly in methanogenic microbial community, such as S organism and Methanobacterium ruminantium, Desulfovibrio vulgaris and Methanosarcina barkeri. In addition, sulfide, L-cysteine and AQDS can act as electron shuttles mediating electron transfer between microorganisms, such as Desulfuromonas acatoxidans and Prosthecochloris aestuarii. However, electron transfer between Geobacter species so far has only been documented to be direct: by way of e-pili and c-type cytochromes. Either of these Geobacter cells short of biological connections, such as e-pili and (or) cytochromes, can not get syntrophically related. Nevertheless, with the mediation of conductive materials, such as activated carbon and biochar, e-pili would become less functional during the process of DIET since syntrophic partners could exchange electrons via these conductive carbon materials. Moreover, conductive mineral magnetite can substitute for outer-membrane c-type cytochrome in its role. Mutant strain of G. sulfurreducens that is deficient in OmcS cannot co-culture with G. metallireducens, but with the addition of magnetites they can exchange electrons successfully. The discovery of DIET has changed the tradition gnosia that microbial syntrophic metabolism would not occur without energy carriers, such as hydrogen and formate, and has opened up a new scientific perspective for understanding biogeochemical processes, such as circulation of C/N/S, emissions of greenhouse and degradation of pollutants. The core of microbial IET is electron transfer between microbes. Further studies should be done on mechanism of IET and new effective IET microorganisms in order to put IET into practical engineering application. However, the researches on tmechanism of IET between microbes, at present, are still in their preliminary stage and so have a number of problems to be solved, for example, how exactly electron transfer occurs between microorganisms, whether there is any microorganism more IET efficient, and if there is any method that can more economically and efficiently accelerate IET, etc. In this review, the mechanisms of MIET is summarized, meanwhile, the three mediating mechanisms for DIET are expounded emphatically. Representative microbes participating in IET are introduced. Potential applications of IET to environment processes such as methane-producing anaerobic digestion, anaerobic methane oxidation and dechlorination are proposed and directions of future researches on IET discussed.
2008, 45(5):837-845.
DOI: trxb10.11766/200806280509
Abstract:
Salt-affected soils are extensively distributed in Northwest,North,Northeast and coastal regions in China,and large areas of arable land are salt affected as well. So they are one of the most important low-yield types of soils. Apparently under influences of human activities,their productivity is closely related to their quality. While reviewing the development of the study on salt affected soils in China,the paper analyzed the status quo of the research and recent advancement in major fields of the study,and discussed prospects of the study by referring to the frontiers and hot spots of relevant researches both at home and abroad. The paper also suggested that emphasis be laid on topics of assessment and forecast of prediction of soil salinization,soil salt-water regime and modeling,mechanism of the interaction between plant and soil salt,optimal regulation of soil salt-water regime,management and remediation of soil salinity,eco-environmental impacts of salinization,etc.
Salt-affected soils are extensively distributed in Northwest,North,Northeast and coastal regions in China,and large areas of arable land are salt affected as well. So they are one of the most important low-yield types of soils. Apparently under influences of human activities,their productivity is closely related to their quality. While reviewing the development of the study on salt affected soils in China,the paper analyzed the status quo of the research and recent advancement in major fields of the study,and discussed prospects of the study by referring to the frontiers and hot spots of relevant researches both at home and abroad. The paper also suggested that emphasis be laid on topics of assessment and forecast of prediction of soil salinization,soil salt-water regime and modeling,mechanism of the interaction between plant and soil salt,optimal regulation of soil salt-water regime,management and remediation of soil salinity,eco-environmental impacts of salinization,etc.
2007, 44(2):288-293.
DOI: 10.11766/trxb200511300214
Abstract:
A modified UV spectrophotometry is compared with the phenoldisulfonic acid colorimetry, MgO distillation and FeSO4-Zn reduction method, and copperized cadmium reduction method in determining NO3- concentration in soil extracts of nine different types of soils. In the UV spectrophotometry, the value of correction factors (f) is determined by measuring the absorbance of the soil extract solution in the absence of NO3-. The mean value of f is 2.2. Statistically, it is highly correlated between the four methods in determination value, particularly in mineral soils with low organic matter (less than 50 g kg-1). All results show no significant difference between UV spectrophotometry and phenoldisulfonic acid colorimetry. However, the f value still needs to be readjusted in soils with high organic matter (more than 50 g kg-1). In general, UV spectrophotometry is simple and rapid, and it can be applied to rapid analysis of large batches of soil samples.
A modified UV spectrophotometry is compared with the phenoldisulfonic acid colorimetry, MgO distillation and FeSO4-Zn reduction method, and copperized cadmium reduction method in determining NO3- concentration in soil extracts of nine different types of soils. In the UV spectrophotometry, the value of correction factors (f) is determined by measuring the absorbance of the soil extract solution in the absence of NO3-. The mean value of f is 2.2. Statistically, it is highly correlated between the four methods in determination value, particularly in mineral soils with low organic matter (less than 50 g kg-1). All results show no significant difference between UV spectrophotometry and phenoldisulfonic acid colorimetry. However, the f value still needs to be readjusted in soils with high organic matter (more than 50 g kg-1). In general, UV spectrophotometry is simple and rapid, and it can be applied to rapid analysis of large batches of soil samples.
2017, 54(5):1047-1056.
DOI: 10.11766/trxb201703180633
Abstract:
【Objective】Soil organic matter (SOM) is an important indicator of soil fertility, and also the basis for carrying on build-up of cropland quality and scientific fertilization. Based on the data of the project of soil test based fertilization and the Second National Soil Survey in 2005-2014, analysis was performed for variation of soil organic matter in top soils of the croplands of China. The objectives of the present study are (1) to report current status of SOM in the croplands of China; (2) to explore changes in SOM content in the croplands of China over the last three decades in nationwide; and (3) to discuss causes of the changes. 【Method】 In this paper, the data of SOM in croplands were cited from the Soil Survey Data of China and Soil Fertility of China, covering a total of 131 627 000 hm2 of croplands and the data of the national soil test based formulated fertilization project from the “Basic Nutrient Dataset of the Soils under the Project of Soil Test-Based Formulated Fertilization” covering a total of 8 467 083 data points. As a total of 2 948 agricultural counties (district or city) and farms participated in the project, covering a total of 121 716 000 hm2of croplands calculated according to the data of cropland area by the end of 2008 published by the National Statistics Bureau of China. The distribution of soil sampling sites of the project of soil test-based formulated fertilization was consistent with the data of cropland distribution at the end of 2008, covering 66 700 m2~133 400 m2(on average) in plain areas, 20 010 m2~53 360 m2 in hilly areas, and 6 670 m2~13 340 m2 of vegetable land All soil samples were collected from topsoil (mainly 0~20 cm for crop field and 0~30 cm for vegetable field) in autumn after crops were harvested. Contents of soil organic matter were measured with the oil heating and potassium dichromate-volumetric method. A total of 8 467 083 soil samples were collected nationwide. The data of the soil-test-based formulated fertilization were mathematical means of the soil samples for each province. The massive data bases acquired from the project of soil test-based formulated fertilization and the second national soil survey were analyzed for variation of soil organic matter content in cropland of the country over the last three decades. Based on the data of soil organic matter contents in the croplands of the Second National Soil Survey, the croplands could be sorted into six grades, i.e.>40 g kg-1, 30 g kg-1~40 g kg-1, 20 g kg-1~30 g kg-1,10 g kg-1~20 g kg-1, 6 g kg-1~10 g kg-1 and ≤6 g kg-1【Result】Results show that the average content of soil organic matter in plough layer of the country is found to be 24.65 g kg-1, with the highest in Heilongjiang province being 40.43 g kg-1and the lowest in the Ningxia Hui Autonomous Region being 13.61 g kg-1, and 4.85g kg-1 or 24.49% higher than the average of the second national soil survey. The content of soil organic matter in the croplands of the grade of 30 g kg-1~40 g kg-1 increased by 3.64 percentage points, in those of the grade of 20 g kg-1~30 g kg-1 by 5.68 percentage points, and in those of the grade of 10 g kg-1~20 g kg-1 by 5.36 percentage points, but in those of the grade of > 40 g kg-1 decreased by 1.38 percentage points. In most provinces or regions, soil organic matter increased or remained almost unchanged in content over the past three decades, but in Beijing and Qinghai, it was found to have been decreased slightly. The increases in content of soil organic matter in the plough layers of the country could be attributed to the farming practices of straw incorporation, zero or minimum tillage, and application of organic and green manures. Also, leaving crop stubs in the field is an important practice increasing soil organic matter content.【Conclusion】The average content of soil organic matter in the plough layers of different croplands in China is found to be 24.65 g kg-1. Most of the croplands have been varying in the range from 10 to 30 g kg-1, and exhibiting a rising trend in soil organic matter content over the past three decades, although in some regions croplands originally high in soil organic matter content have decreased somewhat. So the content of soil organic matter in the plough layers will keep on increasing with increasing organic matter input into the croplands in future.
【Objective】Soil organic matter (SOM) is an important indicator of soil fertility, and also the basis for carrying on build-up of cropland quality and scientific fertilization. Based on the data of the project of soil test based fertilization and the Second National Soil Survey in 2005-2014, analysis was performed for variation of soil organic matter in top soils of the croplands of China. The objectives of the present study are (1) to report current status of SOM in the croplands of China; (2) to explore changes in SOM content in the croplands of China over the last three decades in nationwide; and (3) to discuss causes of the changes. 【Method】 In this paper, the data of SOM in croplands were cited from the Soil Survey Data of China and Soil Fertility of China, covering a total of 131 627 000 hm2 of croplands and the data of the national soil test based formulated fertilization project from the “Basic Nutrient Dataset of the Soils under the Project of Soil Test-Based Formulated Fertilization” covering a total of 8 467 083 data points. As a total of 2 948 agricultural counties (district or city) and farms participated in the project, covering a total of 121 716 000 hm2of croplands calculated according to the data of cropland area by the end of 2008 published by the National Statistics Bureau of China. The distribution of soil sampling sites of the project of soil test-based formulated fertilization was consistent with the data of cropland distribution at the end of 2008, covering 66 700 m2~133 400 m2(on average) in plain areas, 20 010 m2~53 360 m2 in hilly areas, and 6 670 m2~13 340 m2 of vegetable land All soil samples were collected from topsoil (mainly 0~20 cm for crop field and 0~30 cm for vegetable field) in autumn after crops were harvested. Contents of soil organic matter were measured with the oil heating and potassium dichromate-volumetric method. A total of 8 467 083 soil samples were collected nationwide. The data of the soil-test-based formulated fertilization were mathematical means of the soil samples for each province. The massive data bases acquired from the project of soil test-based formulated fertilization and the second national soil survey were analyzed for variation of soil organic matter content in cropland of the country over the last three decades. Based on the data of soil organic matter contents in the croplands of the Second National Soil Survey, the croplands could be sorted into six grades, i.e.>40 g kg-1, 30 g kg-1~40 g kg-1, 20 g kg-1~30 g kg-1,10 g kg-1~20 g kg-1, 6 g kg-1~10 g kg-1 and ≤6 g kg-1【Result】Results show that the average content of soil organic matter in plough layer of the country is found to be 24.65 g kg-1, with the highest in Heilongjiang province being 40.43 g kg-1and the lowest in the Ningxia Hui Autonomous Region being 13.61 g kg-1, and 4.85g kg-1 or 24.49% higher than the average of the second national soil survey. The content of soil organic matter in the croplands of the grade of 30 g kg-1~40 g kg-1 increased by 3.64 percentage points, in those of the grade of 20 g kg-1~30 g kg-1 by 5.68 percentage points, and in those of the grade of 10 g kg-1~20 g kg-1 by 5.36 percentage points, but in those of the grade of > 40 g kg-1 decreased by 1.38 percentage points. In most provinces or regions, soil organic matter increased or remained almost unchanged in content over the past three decades, but in Beijing and Qinghai, it was found to have been decreased slightly. The increases in content of soil organic matter in the plough layers of the country could be attributed to the farming practices of straw incorporation, zero or minimum tillage, and application of organic and green manures. Also, leaving crop stubs in the field is an important practice increasing soil organic matter content.【Conclusion】The average content of soil organic matter in the plough layers of different croplands in China is found to be 24.65 g kg-1. Most of the croplands have been varying in the range from 10 to 30 g kg-1, and exhibiting a rising trend in soil organic matter content over the past three decades, although in some regions croplands originally high in soil organic matter content have decreased somewhat. So the content of soil organic matter in the plough layers will keep on increasing with increasing organic matter input into the croplands in future.
2006, 43(5):851-859.
DOI: 10.11766/trxb200510310521
Abstract:
Phospholipid fatty acids are major constituents of the membranes of all living cells,and different groups of microorganisms synthesize different varieties of PLFA through different biochemical pathways.Thus some PLFAs can be used as "bio-signatures" to analyze changes in microbial biomass and microbial community structure.Currently the PLFA method is more and more used in soil microbial analysis.An introduction was made by the authors to some PLFAs characterizing microorganisms,methods to extract PLFAs from soils and the principle of using GC-MS to analyze PLFAs.Besides,comparison of the PLFA method was conducted with some other commonly used methods.The traditional method,which analyzes soil microbial community structure,depends on culture technology and it is able to culture and separate a small number of microbial communities;the Biolog method is used to investigate physiological diversity of soil microbial communities,i.e.how the microbial communities potentially utilize a range of carbon substrates,but it is of high selectivity to the small fraction of microbial communities that grow fast or fit the Biolog experimental conditions;and the main shortcoming of nucleic acid analysis lies in that it can't make quantitative analysis of soil microbes.However,compared to those methods mentioned above,the PLFA analysis has a number of advantages.The characteristics of the PLFA analysis have been demonstrated in this article with several practical examples,and some disadvantages of the PLFA analysis have been analyzed.By using the PLFA method combined with some others,more comprehensive and integrated information about the diversity of soil microbial communities can be obtained.
Phospholipid fatty acids are major constituents of the membranes of all living cells,and different groups of microorganisms synthesize different varieties of PLFA through different biochemical pathways.Thus some PLFAs can be used as "bio-signatures" to analyze changes in microbial biomass and microbial community structure.Currently the PLFA method is more and more used in soil microbial analysis.An introduction was made by the authors to some PLFAs characterizing microorganisms,methods to extract PLFAs from soils and the principle of using GC-MS to analyze PLFAs.Besides,comparison of the PLFA method was conducted with some other commonly used methods.The traditional method,which analyzes soil microbial community structure,depends on culture technology and it is able to culture and separate a small number of microbial communities;the Biolog method is used to investigate physiological diversity of soil microbial communities,i.e.how the microbial communities potentially utilize a range of carbon substrates,but it is of high selectivity to the small fraction of microbial communities that grow fast or fit the Biolog experimental conditions;and the main shortcoming of nucleic acid analysis lies in that it can't make quantitative analysis of soil microbes.However,compared to those methods mentioned above,the PLFA analysis has a number of advantages.The characteristics of the PLFA analysis have been demonstrated in this article with several practical examples,and some disadvantages of the PLFA analysis have been analyzed.By using the PLFA method combined with some others,more comprehensive and integrated information about the diversity of soil microbial communities can be obtained.
2004, 41(1):35-43.
DOI: 10.11766/trxb200301140106
Abstract:
Soil organic C plays an essential role in carbon cycle and carbon storage in a native ecosystem reflects that ecosystem.s capacity to sequester carbon.Based on soil map of China(1:4 000 000)combined with a soil database from the second soil survey of China,soil organic carbon storage to the depths of 100 cm and 20 cm were estimated for China using geographical information system.Carbon density of different soil types ranged from 1.19 kg m-2 to 176.46 kg m-2 at depth of 100 cm,and from 0.27 kg m-2 to 53.46 kg m-2 at depth of 20 cm.In total,about 84.4 Pg was stored in 0~100 cm,and 27.4 Pg in the 0~20 cm soil layer.The amount of carbon varied significantly at different districts in China.Northeast China, the south and east of Qinghai-Tibet Plateau and southwest China had high carbon density.Tarim Basin,Caidam Basin,Junggar Basin and other desert ification districts had low carbon density.This distribution showed an important climatic influence.Soil organic carbon would diminish with decreasing precipitation and increasing temperature.On the other hand,the activities of human beings may affect the range of soil carbon.
Soil organic C plays an essential role in carbon cycle and carbon storage in a native ecosystem reflects that ecosystem.s capacity to sequester carbon.Based on soil map of China(1:4 000 000)combined with a soil database from the second soil survey of China,soil organic carbon storage to the depths of 100 cm and 20 cm were estimated for China using geographical information system.Carbon density of different soil types ranged from 1.19 kg m-2 to 176.46 kg m-2 at depth of 100 cm,and from 0.27 kg m-2 to 53.46 kg m-2 at depth of 20 cm.In total,about 84.4 Pg was stored in 0~100 cm,and 27.4 Pg in the 0~20 cm soil layer.The amount of carbon varied significantly at different districts in China.Northeast China, the south and east of Qinghai-Tibet Plateau and southwest China had high carbon density.Tarim Basin,Caidam Basin,Junggar Basin and other desert ification districts had low carbon density.This distribution showed an important climatic influence.Soil organic carbon would diminish with decreasing precipitation and increasing temperature.On the other hand,the activities of human beings may affect the range of soil carbon.
2004, 41(4):618-623.
DOI: 10.11766/trxb200308110419
Abstract:
Soil organic carbon has been regarded as one of the most important pools that retain CO2,and a binding agent influencing soil structure formation and stability.This paper reviews latest researches on soil structure hierarchy and different soil organic carbon pools contributing to soil structure formation and stability,mechanisms of soil structure hierarchy and stability being affected by the quantity and quality of soil active organic carbon pools,such as particulate organic matter and dissolved organic matter,and effects of hydrophobic organic matter on soil structure stability and soil properties.In the end,the authors pro pose researches in future to elucidate the relationship between soil organic carbon pools and soil structure stability under different land uses and soil managements;to quantify the formation processes of soil organic carbon pools and soil structure hierarchy;to investigate the relationship between soil organic carbon pools,soil structure stability and soil resiliency;to clarify effect of the quality of soil organic carbon on water infiltration and to consummate the models of soil organic carbon and water recycling.
Soil organic carbon has been regarded as one of the most important pools that retain CO2,and a binding agent influencing soil structure formation and stability.This paper reviews latest researches on soil structure hierarchy and different soil organic carbon pools contributing to soil structure formation and stability,mechanisms of soil structure hierarchy and stability being affected by the quantity and quality of soil active organic carbon pools,such as particulate organic matter and dissolved organic matter,and effects of hydrophobic organic matter on soil structure stability and soil properties.In the end,the authors pro pose researches in future to elucidate the relationship between soil organic carbon pools and soil structure stability under different land uses and soil managements;to quantify the formation processes of soil organic carbon pools and soil structure hierarchy;to investigate the relationship between soil organic carbon pools,soil structure stability and soil resiliency;to clarify effect of the quality of soil organic carbon on water infiltration and to consummate the models of soil organic carbon and water recycling.
2016, 53(5):1160-1169.
DOI: 10.11766/trxb201602220576
Abstract:
【Objective】How matter recycling matches ecosystem services is always one of the central concerns of the research on ecology, and C:N:P ecological stoichiometry has been an effective tool to link chemical processes on the molecular level with ecological processes in ecosystems. The knowledge about how carbon, N and P is distributed in wetland soils and whether there is a "Redfiled-type" C:N:P ratio in regional or global wetland soils is the basis for understanding fate of carbon, nitrogen and phosphorus and modeling matter circulation in wetland ecosystems. Objectives of this study are to examine whether there is a consistent C:N:P ratio in wetland soils of China and to find its potential influencing factors. 【Method】Based on the data of carbon, nutrient contents, soil properties, vegetation, meteorology and C:N:P ratios of wetland soils of 119 marshes or wetlands published in the “Journal of Marshes of China”, ecological stoichiometric characteristics of C:N:P ratios on a regional scale and their potential affecting factors were analyzed with the mathematical statistics. 【Result】Results show that the average C, N and P content in the wetlands of China was 22.93%, 0.76% and 0.16%, respectively; the average C:N, C:P and N:P ratio (mole ratio) was 18.22, 245.22 and 13.60, respectively, all higher than their respective ones in the soils of the country and the globe; and the average C:N:P ratio was 245:13.6:1. The C:N, C:P and N:P ratio in organic soils was higher than their respective ones in mineral soils. No significant difference was found in soil C:N:P between meadow, peat moss and forest wetlands; However, significant differences were found between inland freshwater, inland saline and tidal wetlands, with the inland freshwater wetlands being the highest and the tidal wetlands the lowest in C:P and N:P ratios, but. no difference in C:N was between the two. Overall, C:N, C:P and N:P ratios were the highest in inland freshwater wetlands and the lowest in tidal wetlands. Pearson analysis shows no significant pairwise relationship was found between the three elements, which implies that there is no “Redfield”-type ratios in the wetland soils of China. Wetland ecosystems were more affected by P than the other soil nutrients. No significant difference in C:N ratio was found between climate zones, but a decreasing order of Tropical Zone > Temperate Zone > Plateau Temperate Zone > Warm Temperate Zone >Mid-subtropical Zone > Northern Subtropical Zone was, while C:P and N:P ratios differed significantly between climate zones, which followed an order of Plateau Temperate Zone > Temperate Zone > Mid-subtropical Zone > Tropical Zone > Warm Temperate Zone > Northern Subtropical Zone in C:P ratio and an order of Plateau Temperate Zone > Mid-subtropical Zone > Temperate Zone > Warm Temperate Zone > Tropical Zone > Northern Subtropical Zone in N:P ratio. Correlation analysis shows that altitude, temperatures (annual mean temperature, mean temperatures in January and July, and active accumulated temperature) and pH are the three main factors determining C:N:P ratios in the wetlands of China. 【Conclusion】In conclusion, C:N:P in the wetland soils of China are highly affected by soil types and climate conditions, and little by plant vegetation. Taking into account the extremely significant correlations of altitude with C:P and N:P, altitude is deemed to be the decisive factor of C:N:P ecological stoichiometry of wetland soils.
【Objective】How matter recycling matches ecosystem services is always one of the central concerns of the research on ecology, and C:N:P ecological stoichiometry has been an effective tool to link chemical processes on the molecular level with ecological processes in ecosystems. The knowledge about how carbon, N and P is distributed in wetland soils and whether there is a "Redfiled-type" C:N:P ratio in regional or global wetland soils is the basis for understanding fate of carbon, nitrogen and phosphorus and modeling matter circulation in wetland ecosystems. Objectives of this study are to examine whether there is a consistent C:N:P ratio in wetland soils of China and to find its potential influencing factors. 【Method】Based on the data of carbon, nutrient contents, soil properties, vegetation, meteorology and C:N:P ratios of wetland soils of 119 marshes or wetlands published in the “Journal of Marshes of China”, ecological stoichiometric characteristics of C:N:P ratios on a regional scale and their potential affecting factors were analyzed with the mathematical statistics. 【Result】Results show that the average C, N and P content in the wetlands of China was 22.93%, 0.76% and 0.16%, respectively; the average C:N, C:P and N:P ratio (mole ratio) was 18.22, 245.22 and 13.60, respectively, all higher than their respective ones in the soils of the country and the globe; and the average C:N:P ratio was 245:13.6:1. The C:N, C:P and N:P ratio in organic soils was higher than their respective ones in mineral soils. No significant difference was found in soil C:N:P between meadow, peat moss and forest wetlands; However, significant differences were found between inland freshwater, inland saline and tidal wetlands, with the inland freshwater wetlands being the highest and the tidal wetlands the lowest in C:P and N:P ratios, but. no difference in C:N was between the two. Overall, C:N, C:P and N:P ratios were the highest in inland freshwater wetlands and the lowest in tidal wetlands. Pearson analysis shows no significant pairwise relationship was found between the three elements, which implies that there is no “Redfield”-type ratios in the wetland soils of China. Wetland ecosystems were more affected by P than the other soil nutrients. No significant difference in C:N ratio was found between climate zones, but a decreasing order of Tropical Zone > Temperate Zone > Plateau Temperate Zone > Warm Temperate Zone >Mid-subtropical Zone > Northern Subtropical Zone was, while C:P and N:P ratios differed significantly between climate zones, which followed an order of Plateau Temperate Zone > Temperate Zone > Mid-subtropical Zone > Tropical Zone > Warm Temperate Zone > Northern Subtropical Zone in C:P ratio and an order of Plateau Temperate Zone > Mid-subtropical Zone > Temperate Zone > Warm Temperate Zone > Tropical Zone > Northern Subtropical Zone in N:P ratio. Correlation analysis shows that altitude, temperatures (annual mean temperature, mean temperatures in January and July, and active accumulated temperature) and pH are the three main factors determining C:N:P ratios in the wetlands of China. 【Conclusion】In conclusion, C:N:P in the wetland soils of China are highly affected by soil types and climate conditions, and little by plant vegetation. Taking into account the extremely significant correlations of altitude with C:P and N:P, altitude is deemed to be the decisive factor of C:N:P ecological stoichiometry of wetland soils.
ZHONG Songxiong
,
HE Hongfei
,
chen zhiliang
,
YIN Guangcai
,
LIN Qintie
,
HUANG Ling
,
WANG Xin
,
Liu Deling
2018, 55(1):1-17.
DOI: 10.11766/trxb201704250028
Abstract:
Oxidation, reduction and methylation of arsenic in paddy soil are the key factors regulating transportation, transformation, and crop uptake of the element. Flooding is a common farming practice in rice cultivation, forming an anaerobic environment in the paddy soil, which not only affects the biochemical behavior of arsenic significantly, but also is often associated with enhanced uptake of arsenic by rice, thus further posing a health risk to those who consume rice as staple food. Studies in the previous focused mainly on those behaviors of soil arsenic in flooded anaerobic paddy soil and their relevant mechanisms, but a comprehensive review of the studies is yet to be prepared. In this study, the biochemical behaviors of arsenic in paddy soil is summarized, and their relevant mechanisms and influential factors, including iron oxides, organic matter, redox potential (Eh) and pH are discussed. Besides, the paper also elaborates discussed how the anaerobic condition in the flooded paddy field during the paddy rice growing season affects those biochemical behaviors. Generally speaking, the iron and arsenic reducing microbes in the soil are mainly anaerobic microbes, e.g. Geobacter, Shewanella and Myxobacter, while the iron and arsenic oxidizing microbes are predominantly aerobic microbes. Therefore, the development of an anaerobic reducing condition in flooded paddy fields favors microbial iron and arsenic reduction, and what is more, as iron oxides are the most effective scavenger of arsenic in paddy soil, the flooded anaerobic environment also favors release of arsenic. It is noteworthy that arsenic desorbed from iron oxides is more prone to bioreduction. Studies in the past indicate that adsorption of arsenic by iron oxides like ferrihydrite, goethite and hematite, especially ferrihydrite, the most abundant amorphous iron oxide in paddy soil, retards bioreduction of arsenic. Another contributor to enhanced bioreduction and release of arsenic is organic matter, which serves as nutritional substance and electron donor for microbes in metabolism. In flooded anaerobic paddy soil, the addition of extraneous organic matter facilitates formation of a reducing environment, stimulates reductive iron dissolution, arsenic reduction and arsenic release in rate and extent. Besides, flooded anaerobic paddy soil is also favorable to arsenic methylation, which uses arsenite as potenital inorganic substrate. Although flooded anaerobic paddy soil is not good to microbial arsenic oxidation, anaerobic arsenic oxidation processes mediated by microbes harboring arxA gene in paddy soil was reported in studies in the past. In terms of genes in microbes responsible for arsenic metabolism, current researches focus mainly on the following ones: arxA, arsenic respiratory reduction gene; arsC, arsenic detoxification reduction gene; arxA, arsenic oxidation gene; arxA, anaerobic arsenic oxidation gene; and arsM, arsenic methylation gene. In the past studies, gene arsC was found in close relationship with arsM, which is related to the response of the microbes harboring these genes to the stress of arsenic toxicity. By studying changes in abundance, diversity and gene expression of the microbial community in flooded paddy soil, a clearer picture can then be plotted of the biochemical behavior of soil arsenic in paddy soil as affected changes in environment. At the end, the paper describes prospects of the research and holds that the researches may serve as references for prevention of arsenic contamination in paddy soil and for alleviation of uptake and accumulation of arsenic by rice. For future researches the following aspects should be covered: (1) effects of organic matter, relative to type, on diversity of arsenic metabolising microbes that are capable of mediating dissimilatory iron reduction, arsenic reduction and methylation, direct physciochemical interaction between organic matter and arsenic, and ternary interaction of organic matter-iron mineral-arsenic as affected by chelation, competition and coupling; (2) Response of arsenic metabolism related enzymes to variation of micro-environment and its relationship with arsenic transportation and transformation, and relationship between organic matter and arsenic methyltransferase in the microbes; (3) Influence of carbon and nitrogen recycling, particularly Feammox, on biochemical behaviors of iron and arsenic, and influences of nitrogen-iron recycling and carbon-iron recycling on arsenic redox, e.g. influences of the competition between dissimilatory iron reduction and Feammox on arsenic dynamics; (4) Systems research on dynamics of the microbial community involved in arsenic metabolism in rhizospheric soil and bulk soil and biochemical behaviors of arsenic at the soil interface and soil-solution interface in paddy fields subjected flooding and draining, long term flooding or sprinkler irrigation.
Oxidation, reduction and methylation of arsenic in paddy soil are the key factors regulating transportation, transformation, and crop uptake of the element. Flooding is a common farming practice in rice cultivation, forming an anaerobic environment in the paddy soil, which not only affects the biochemical behavior of arsenic significantly, but also is often associated with enhanced uptake of arsenic by rice, thus further posing a health risk to those who consume rice as staple food. Studies in the previous focused mainly on those behaviors of soil arsenic in flooded anaerobic paddy soil and their relevant mechanisms, but a comprehensive review of the studies is yet to be prepared. In this study, the biochemical behaviors of arsenic in paddy soil is summarized, and their relevant mechanisms and influential factors, including iron oxides, organic matter, redox potential (Eh) and pH are discussed. Besides, the paper also elaborates discussed how the anaerobic condition in the flooded paddy field during the paddy rice growing season affects those biochemical behaviors. Generally speaking, the iron and arsenic reducing microbes in the soil are mainly anaerobic microbes, e.g. Geobacter, Shewanella and Myxobacter, while the iron and arsenic oxidizing microbes are predominantly aerobic microbes. Therefore, the development of an anaerobic reducing condition in flooded paddy fields favors microbial iron and arsenic reduction, and what is more, as iron oxides are the most effective scavenger of arsenic in paddy soil, the flooded anaerobic environment also favors release of arsenic. It is noteworthy that arsenic desorbed from iron oxides is more prone to bioreduction. Studies in the past indicate that adsorption of arsenic by iron oxides like ferrihydrite, goethite and hematite, especially ferrihydrite, the most abundant amorphous iron oxide in paddy soil, retards bioreduction of arsenic. Another contributor to enhanced bioreduction and release of arsenic is organic matter, which serves as nutritional substance and electron donor for microbes in metabolism. In flooded anaerobic paddy soil, the addition of extraneous organic matter facilitates formation of a reducing environment, stimulates reductive iron dissolution, arsenic reduction and arsenic release in rate and extent. Besides, flooded anaerobic paddy soil is also favorable to arsenic methylation, which uses arsenite as potenital inorganic substrate. Although flooded anaerobic paddy soil is not good to microbial arsenic oxidation, anaerobic arsenic oxidation processes mediated by microbes harboring arxA gene in paddy soil was reported in studies in the past. In terms of genes in microbes responsible for arsenic metabolism, current researches focus mainly on the following ones: arxA, arsenic respiratory reduction gene; arsC, arsenic detoxification reduction gene; arxA, arsenic oxidation gene; arxA, anaerobic arsenic oxidation gene; and arsM, arsenic methylation gene. In the past studies, gene arsC was found in close relationship with arsM, which is related to the response of the microbes harboring these genes to the stress of arsenic toxicity. By studying changes in abundance, diversity and gene expression of the microbial community in flooded paddy soil, a clearer picture can then be plotted of the biochemical behavior of soil arsenic in paddy soil as affected changes in environment. At the end, the paper describes prospects of the research and holds that the researches may serve as references for prevention of arsenic contamination in paddy soil and for alleviation of uptake and accumulation of arsenic by rice. For future researches the following aspects should be covered: (1) effects of organic matter, relative to type, on diversity of arsenic metabolising microbes that are capable of mediating dissimilatory iron reduction, arsenic reduction and methylation, direct physciochemical interaction between organic matter and arsenic, and ternary interaction of organic matter-iron mineral-arsenic as affected by chelation, competition and coupling; (2) Response of arsenic metabolism related enzymes to variation of micro-environment and its relationship with arsenic transportation and transformation, and relationship between organic matter and arsenic methyltransferase in the microbes; (3) Influence of carbon and nitrogen recycling, particularly Feammox, on biochemical behaviors of iron and arsenic, and influences of nitrogen-iron recycling and carbon-iron recycling on arsenic redox, e.g. influences of the competition between dissimilatory iron reduction and Feammox on arsenic dynamics; (4) Systems research on dynamics of the microbial community involved in arsenic metabolism in rhizospheric soil and bulk soil and biochemical behaviors of arsenic at the soil interface and soil-solution interface in paddy fields subjected flooding and draining, long term flooding or sprinkler irrigation.
2014, 51(6):1183-1191.
DOI: 10.11766/trxb201311270569
Abstract:
Soil is probably the most challenging of all natural environments for microbiologists, and the hotspot for discovering of novel biomolecules and genetic resources. Cultivation of environmental microorganisms was ignored and marginalized in the tremendous progress of “meta-omics” technologies. Nevertheless, by cultivation-based approaches, researchers can acquire novel microorganisms that are undetected by molecular methods, be allowed for the verification and testing of hypotheses of metabolic potential and function of novel genes determined by the meta-omic data and also do the microbial foundational research or industrial production. In the era of meta-omics, cultivation method is still useful in understanding the detailed metabolism and functions of those environmental organisms, and this makes the genetic manipulation, confirming certain functions, and the research of environmental function of microorganisms possible. The challenge is to bring these recalcitrant microorganisms into the laboratory for future exploration. This review summarizes the reasons why microbes are not growing in the lab such as. Then we focus on the advanced cultivation techniques. The methods of modifications to growth media include using low substrate concentrations, adding growth-limiting factors into media and changing gelling reagents. Modifications to growth conditions include extending incubation time, incubating in a optimum oxygen level, and using low-temperature strategies. The strategies of cultures in situ or cultures in simulated natural conditions include “growth chamber” and “trap for in situ cultivation”. The methods of community culture and co-culture also elevated the possibility of novel bacteria from environmental samples. Cultivation of soil microorganisms by assistance of culture-independent methods such as metagenomics and metaproteomics have been developed to improve the cultivating process. Finally, we propose the directions of isolation of soil microbes in the future.
Soil is probably the most challenging of all natural environments for microbiologists, and the hotspot for discovering of novel biomolecules and genetic resources. Cultivation of environmental microorganisms was ignored and marginalized in the tremendous progress of “meta-omics” technologies. Nevertheless, by cultivation-based approaches, researchers can acquire novel microorganisms that are undetected by molecular methods, be allowed for the verification and testing of hypotheses of metabolic potential and function of novel genes determined by the meta-omic data and also do the microbial foundational research or industrial production. In the era of meta-omics, cultivation method is still useful in understanding the detailed metabolism and functions of those environmental organisms, and this makes the genetic manipulation, confirming certain functions, and the research of environmental function of microorganisms possible. The challenge is to bring these recalcitrant microorganisms into the laboratory for future exploration. This review summarizes the reasons why microbes are not growing in the lab such as. Then we focus on the advanced cultivation techniques. The methods of modifications to growth media include using low substrate concentrations, adding growth-limiting factors into media and changing gelling reagents. Modifications to growth conditions include extending incubation time, incubating in a optimum oxygen level, and using low-temperature strategies. The strategies of cultures in situ or cultures in simulated natural conditions include “growth chamber” and “trap for in situ cultivation”. The methods of community culture and co-culture also elevated the possibility of novel bacteria from environmental samples. Cultivation of soil microorganisms by assistance of culture-independent methods such as metagenomics and metaproteomics have been developed to improve the cultivating process. Finally, we propose the directions of isolation of soil microbes in the future.
2013, 50(6):1221-1225.
DOI: 10.11766/trxb201305160235
Abstract:
2014, 51(3):429-438.
DOI: 10.11766/trxb201311010505
Abstract:
Soil pollution, in particular, soil heavy metal pollution is a severe problem in China, which has now come to the extent of threatening food security of the nation, for heavy metals accumulate in edible parts of the crops produced in some severely contaminated areas. However the currently used standard for soil environmental quality does not fit the demands of the soil environmental management today, which manifested in the index system is that the number of indices covering heavy metals pollution is limited. So far the standard of China has only eight heavy metals covered, much fewer than that of the USA, Canada, the Netherland etc., which has led to inefficient management of some soil pollution problems popped up recently with the development of economy in China. Therefore, the objective of this study is to find the gaps between China and those developed countries and regions in the establishment of soil standard for heavy metals, and to provide some proposal for the revision of China’s soil environment quality standard in the future. A worldwide investigation has been conducted on the soil environmental standard of those developed counties and regions, such as USA, Candia, the Netherland, Germany, Australia, Japan, Taiwan (China) and so on. The item counts, kinds and species of the heavy metals involved in these soil standards were mainly concerned of. Meanwhile, in depth study and systematic analysis was conducted of indices of heavy metals in the standards for soil environment of some developed countries and regions for comparisons with ours. Similarity and difference were both found based on the comparison. The similarity is that the high toxic elements such as Cd, Hg and As are contained in the soil standards of most countries and regions. The differences are mainly in relation to the speciation of the elements. The hexavalent chromium and organic mercury are contained in the soil standard of some developed countries and regions due to their high toxicities. However, standards of chromium and mercury are simply provided based on the total content in China’s Soil Environmental Quality Standard. Another difference is the usage of extractable speciation in addition to the total content of heavy metals in the standard of some developed countries such as Germany, Switzerland and Japan while not in the standard of China. This could be owing to the large diversity of soil types in China and be difficult to find a common extracting agent for all the soil types. Meanwhile, China has its own characteristics in soil heavy metal pollution, which includes beryllium, antimony, thallium and vanadium pollution as a result of high geochemical background in the calcareous rock soil or some mining areas that mainly located in the south China. These heavy metals pollution have threatened to human health of local residents. On such a basis, suggestions are put forth for revising the current standard of the country, including amendment of the criteria for valences and forms of highly toxic heavy metals, like hexavalent chromium and organic mercury; setting up of criteria for newly emerged heavy metal pollutants, like beryllium, antimony, thallium, vanadium, etc.; and exploration for establishment of a bioavailability-based index system for extractable forms of heavy metals, by taking into account soils or rocks in calcareous regions with high heavy metals background values, so as to provide some scientific basis for management of soil heavy metal pollution risks in China.
Soil pollution, in particular, soil heavy metal pollution is a severe problem in China, which has now come to the extent of threatening food security of the nation, for heavy metals accumulate in edible parts of the crops produced in some severely contaminated areas. However the currently used standard for soil environmental quality does not fit the demands of the soil environmental management today, which manifested in the index system is that the number of indices covering heavy metals pollution is limited. So far the standard of China has only eight heavy metals covered, much fewer than that of the USA, Canada, the Netherland etc., which has led to inefficient management of some soil pollution problems popped up recently with the development of economy in China. Therefore, the objective of this study is to find the gaps between China and those developed countries and regions in the establishment of soil standard for heavy metals, and to provide some proposal for the revision of China’s soil environment quality standard in the future. A worldwide investigation has been conducted on the soil environmental standard of those developed counties and regions, such as USA, Candia, the Netherland, Germany, Australia, Japan, Taiwan (China) and so on. The item counts, kinds and species of the heavy metals involved in these soil standards were mainly concerned of. Meanwhile, in depth study and systematic analysis was conducted of indices of heavy metals in the standards for soil environment of some developed countries and regions for comparisons with ours. Similarity and difference were both found based on the comparison. The similarity is that the high toxic elements such as Cd, Hg and As are contained in the soil standards of most countries and regions. The differences are mainly in relation to the speciation of the elements. The hexavalent chromium and organic mercury are contained in the soil standard of some developed countries and regions due to their high toxicities. However, standards of chromium and mercury are simply provided based on the total content in China’s Soil Environmental Quality Standard. Another difference is the usage of extractable speciation in addition to the total content of heavy metals in the standard of some developed countries such as Germany, Switzerland and Japan while not in the standard of China. This could be owing to the large diversity of soil types in China and be difficult to find a common extracting agent for all the soil types. Meanwhile, China has its own characteristics in soil heavy metal pollution, which includes beryllium, antimony, thallium and vanadium pollution as a result of high geochemical background in the calcareous rock soil or some mining areas that mainly located in the south China. These heavy metals pollution have threatened to human health of local residents. On such a basis, suggestions are put forth for revising the current standard of the country, including amendment of the criteria for valences and forms of highly toxic heavy metals, like hexavalent chromium and organic mercury; setting up of criteria for newly emerged heavy metal pollutants, like beryllium, antimony, thallium, vanadium, etc.; and exploration for establishment of a bioavailability-based index system for extractable forms of heavy metals, by taking into account soils or rocks in calcareous regions with high heavy metals background values, so as to provide some scientific basis for management of soil heavy metal pollution risks in China.
20 Classification of typical Argosols of Henan Province at soil series level of Chinese Soil Taxonomy
2015, 52(1):38-47.
DOI: 10.11766/trxb201307040313
Abstract:
With advanced categories of the Chinese Soil Taxonomy established, focus of the research has been shifted to basic categories in recent years. As one of the major soil orders in the Chinese Soil Taxonomy, Argosols in Henan Province includes some quite different soil types according to the diagnostic criteria. A total of 8 typical soil profiles were selected and their landscape features, morphogenetic descriptions, physical and chemical data were analyzed and their positions in the Chinese Soil Taxonomy defined. Results indicate that the 8 soils could be sorted into 6 soil families, which are Loam mixed calcareous mesic Typic Hapli-Ustic Argosols, Loam mixed nonacid mesic Mottlic Hapli-Udic Argosols, Clay loam mixed mesic Mottlic Calci-Ustic Argosols, Clay loam mixed mesic Typic Calci-Ustic Argosols, Loam mixed calcareous mesic Typic Hapli-Udic Argosols and Loam mixed nonacid mesic Typic Hapli-Udic Argosols. On such a basis and in the light of the rules for soil series division and diagnostic features and structural characteristics of Argosols in Henan, attempts were made to set forth a logic diagram for reference and retrieval of soil series to illustrate the logical processes involved in reference and division of soil series. Through reference, the typical soils, with the 8 soil profiles as representatives, are sorted into 7 soil series, that is, Tangyin Series, Jishui Series, Shengou Series, Shangzhuang Series, Houji Series, Zaolin Series and Shangdian Series.
With advanced categories of the Chinese Soil Taxonomy established, focus of the research has been shifted to basic categories in recent years. As one of the major soil orders in the Chinese Soil Taxonomy, Argosols in Henan Province includes some quite different soil types according to the diagnostic criteria. A total of 8 typical soil profiles were selected and their landscape features, morphogenetic descriptions, physical and chemical data were analyzed and their positions in the Chinese Soil Taxonomy defined. Results indicate that the 8 soils could be sorted into 6 soil families, which are Loam mixed calcareous mesic Typic Hapli-Ustic Argosols, Loam mixed nonacid mesic Mottlic Hapli-Udic Argosols, Clay loam mixed mesic Mottlic Calci-Ustic Argosols, Clay loam mixed mesic Typic Calci-Ustic Argosols, Loam mixed calcareous mesic Typic Hapli-Udic Argosols and Loam mixed nonacid mesic Typic Hapli-Udic Argosols. On such a basis and in the light of the rules for soil series division and diagnostic features and structural characteristics of Argosols in Henan, attempts were made to set forth a logic diagram for reference and retrieval of soil series to illustrate the logical processes involved in reference and division of soil series. Through reference, the typical soils, with the 8 soil profiles as representatives, are sorted into 7 soil series, that is, Tangyin Series, Jishui Series, Shengou Series, Shangzhuang Series, Houji Series, Zaolin Series and Shangdian Series.
