Most view articles
2014, 51(2):216-225.
DOI: 10.11766/trxb201312110588
Abstract:
Apparent recovery efficiency (ARE) of applied fertilizers has been commonly calculated as fertilizer use efficiency in China and reported low in a number of literatures. In this paper, a new method is proposed to calculate real nutrient use efficiency (RNUE), which refers to ratio of the nutrients absorbed by plants to the nutrients depleted from the soil. The depleted nutrients may come from the nutrients originally in the soil or from the applied fertilizer. The equation for RNUE calculation could be shown as: Nutrients absorbed by plants / (nutrients from fertilization – negative balance of the soil nutrient pool). RNUE could also be calculated as the difference between 100% and nutrients loss rate. The nutrients not used by plants but depleted from the topsoil are considered lost, while the nutrients remaining in the topsoil are not. Since both the nutrients remaining in soil nutrient pool and the nutrients used by plants come mainly from fertilization, the RNUE can be suggested as the real fertilizer use efficiency (RFUE). Based on the proposed method, the RFUE will be much higher than the ARE reported in China. The loss rate of fertilizer could also be calculated if RFUE is known since their sum is 100%. Thus calculation of RFUE could help us understand real contribution and real loss of the fertilizer in agriculture production and work out proper fertilization strategies, as well, in light of fertilizer loss rate and soil nutrient holding capacity. A proper right fertilization technique should aim to reduce loss rate of the fertilizer, instead of achieving high ARE since the meaning of high ARE is not so clear even though it has been widely used in China. Fertilizer recommendation for main field crops will not depend so much on soil testing, but rather on the knowledge of the consumption and loss rate of nutrients of the soil-crop systems in future.
Apparent recovery efficiency (ARE) of applied fertilizers has been commonly calculated as fertilizer use efficiency in China and reported low in a number of literatures. In this paper, a new method is proposed to calculate real nutrient use efficiency (RNUE), which refers to ratio of the nutrients absorbed by plants to the nutrients depleted from the soil. The depleted nutrients may come from the nutrients originally in the soil or from the applied fertilizer. The equation for RNUE calculation could be shown as: Nutrients absorbed by plants / (nutrients from fertilization – negative balance of the soil nutrient pool). RNUE could also be calculated as the difference between 100% and nutrients loss rate. The nutrients not used by plants but depleted from the topsoil are considered lost, while the nutrients remaining in the topsoil are not. Since both the nutrients remaining in soil nutrient pool and the nutrients used by plants come mainly from fertilization, the RNUE can be suggested as the real fertilizer use efficiency (RFUE). Based on the proposed method, the RFUE will be much higher than the ARE reported in China. The loss rate of fertilizer could also be calculated if RFUE is known since their sum is 100%. Thus calculation of RFUE could help us understand real contribution and real loss of the fertilizer in agriculture production and work out proper fertilization strategies, as well, in light of fertilizer loss rate and soil nutrient holding capacity. A proper right fertilization technique should aim to reduce loss rate of the fertilizer, instead of achieving high ARE since the meaning of high ARE is not so clear even though it has been widely used in China. Fertilizer recommendation for main field crops will not depend so much on soil testing, but rather on the knowledge of the consumption and loss rate of nutrients of the soil-crop systems in future.
Zeng Xibai
,
Xu Jianming
,
Huang Qiaoyun
,
Tang Shirong
,
Li Yongtao
,
Li Fangbai
,
Zhou Dongmei
,
Wu Zhijie
2013, 50(1):186-194.
DOI: 10.11766/trxb201206300263
Abstract:
On the basis of the site-specific survey and data analyses, we got a viewpoint that the heavy metal contents in the main agricultural regions of China were acceptable and safe, except some specific regions with high risk of heavy metal pollution. Although the heavy metal contents in most farmlands are just “overproof” rather than “polluted”, there is a significant tendency towards the accumulation of heavy metals in farmlands. Meanwhile, based on the summary of publications on soil heavy metals in China such as immobilization and mobilization, plant uptake and barrier, and microbial transformation and utilization of soil heavy metals, some suggestions were proposed on safe utilization of farmlands with high content of heavy metals, establishment of heavy metal thresholds, control and remediation of heavy metal pollution, safely controlling strategies for producing fields, and so on.
On the basis of the site-specific survey and data analyses, we got a viewpoint that the heavy metal contents in the main agricultural regions of China were acceptable and safe, except some specific regions with high risk of heavy metal pollution. Although the heavy metal contents in most farmlands are just “overproof” rather than “polluted”, there is a significant tendency towards the accumulation of heavy metals in farmlands. Meanwhile, based on the summary of publications on soil heavy metals in China such as immobilization and mobilization, plant uptake and barrier, and microbial transformation and utilization of soil heavy metals, some suggestions were proposed on safe utilization of farmlands with high content of heavy metals, establishment of heavy metal thresholds, control and remediation of heavy metal pollution, safely controlling strategies for producing fields, and so on.
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.
2015, 52(1):220-227.
DOI: 10.11766/trxb201402180069
Abstract:
Soil thickness generally refers to thickness of a solum or thickness of the effective soil layer, so it can intuitively express soil properties. On the basis of the work the predecessors have done in light of the definition of solum thickness and relevant criteria for partitioning solum thickness, the authors clarify the concept of solum from the perspective of pedogenesis and put forward some concrete soil thickness partitioning methods specific to soils different in soil type and in land use, while taking into account their own long-term field survey experience. Based on the newly proposed criteria for soil thickness partitioning, 16 soil profiles collected recently in the fields in Anhui, Hubei, Shandong, Qinghai, Gansu, Inner Mongolia and some other provinces were used as cases for soil thickness partitioning. The work may serve as reference for future researches on soil thickness in China.
Soil thickness generally refers to thickness of a solum or thickness of the effective soil layer, so it can intuitively express soil properties. On the basis of the work the predecessors have done in light of the definition of solum thickness and relevant criteria for partitioning solum thickness, the authors clarify the concept of solum from the perspective of pedogenesis and put forward some concrete soil thickness partitioning methods specific to soils different in soil type and in land use, while taking into account their own long-term field survey experience. Based on the newly proposed criteria for soil thickness partitioning, 16 soil profiles collected recently in the fields in Anhui, Hubei, Shandong, Qinghai, Gansu, Inner Mongolia and some other provinces were used as cases for soil thickness partitioning. The work may serve as reference for future researches on soil thickness in China.
2014, 51(5):921-933.
DOI: 10.11766/trxb201405130230
Abstract:
Since the invention and application of nitrogen (N) fertilizer, people always wanted to measure the effects of N fertilizer application by nitrogen use efficiency (NUE). The traditional NUE is the percentage of fertilizer N uptake by crop to N fertilizer rate, which didn’t consider the replenishing effect of fertilizer N to soil N consumption. Due to the defects of the concept and calculation, and the poor interpretations and understands of the results, there are a lot of misunderstands in the literature and daily communication. Therefore, many improved method for calculating NUE were proposed by researchers. However, although these methods had been involved the residual effects of N fertilizer on succeeding crops, they didn’t touch the core issue of the replenishing effect of fertilizer N to soil N consumption. Based on the main N flows in the soil-crop system and the relationships between the fertilizer N, soil N and crop N uptake (called three N), I proposed the concept and calculation of nitrogen fertilizer availability ratio (NFAR) in this study. The core item for NFAR is that the residual fertilizer N is regard as the replenishing to soil N consumption. I recognize that the NFAR is 50%~60% and the loss rate of N fertilizer is 40%~50% under current N management practices in China based on the analysis the data from the 15N tracer field trial, which reflects the high loss of fertilizer N in practices. It is possible to increase NFAR to 70%~90% by improved fertilizer N and agronomic managements. The NFAR expand the idea for the effects of N fertilizer application. It would be important for demonstrating the real effects of crop N uptake and soil N fertility maintain by N fertilizer, and would reflect real loss to environments of N fertilizer application.
Since the invention and application of nitrogen (N) fertilizer, people always wanted to measure the effects of N fertilizer application by nitrogen use efficiency (NUE). The traditional NUE is the percentage of fertilizer N uptake by crop to N fertilizer rate, which didn’t consider the replenishing effect of fertilizer N to soil N consumption. Due to the defects of the concept and calculation, and the poor interpretations and understands of the results, there are a lot of misunderstands in the literature and daily communication. Therefore, many improved method for calculating NUE were proposed by researchers. However, although these methods had been involved the residual effects of N fertilizer on succeeding crops, they didn’t touch the core issue of the replenishing effect of fertilizer N to soil N consumption. Based on the main N flows in the soil-crop system and the relationships between the fertilizer N, soil N and crop N uptake (called three N), I proposed the concept and calculation of nitrogen fertilizer availability ratio (NFAR) in this study. The core item for NFAR is that the residual fertilizer N is regard as the replenishing to soil N consumption. I recognize that the NFAR is 50%~60% and the loss rate of N fertilizer is 40%~50% under current N management practices in China based on the analysis the data from the 15N tracer field trial, which reflects the high loss of fertilizer N in practices. It is possible to increase NFAR to 70%~90% by improved fertilizer N and agronomic managements. The NFAR expand the idea for the effects of N fertilizer application. It would be important for demonstrating the real effects of crop N uptake and soil N fertility maintain by N fertilizer, and would reflect real loss to environments of N fertilizer application.
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.
Meng Hongqi
,
Liu Jing
,
Xu Minggang
,
Lü Jialong
,
Zhou Baoku
,
Peng Chang
,
Shi Xiaojun
,
Huang Qinghai
2013, 50(6):1109-1116.
DOI: 10.11766/trxb201211070459
Abstract:
The aims of this study were to explore the evolution of pH in topsoils under long-term different fertilization regimes, and further to understand the mechanisms and methods against soil acidification in croplands. We collected historical data on six 18–30 years long-term fertilization experiments in typical Chinese croplands of red soil in Qiyang and Jinxian, purple soil in Chongqing, black soil in Gongzhuling and Harbin with conventional and high fertilization rates, and then analyzed the differences in soil pH and acidification rate among experimental stages (six years each) and treatments, i.e., no-fertilizer control (CK), sole chemical nitrogen fertilizer (N), chemical nitrogen plus phosphorous and potassium fertilizers (NPK) and NPK fertilizers amended with manure (NPKM). Results show that under control, topsoil pHs declined somewhat and acidification rates averaged 0.013 pH a -1. Under the N treatment, topsoil pHs of the experiments in Qiyang, Gongzhuling and Harbin with conventional fertilization rate were lowered by 0.32–0.55 units at the initial 6 years and all the experiments by 0.64–1.46 units at the recent 6 years as compared with those under control. Topsoil pHs under the NPK treatment were obviously lower than those under the N treatment over the 1–12 years experimental period. However, topsoil pHs under the NPKM treatment were 0.30–0.53 units higher than those under the NPK treatment, and the two had a similar pH evolution curve. Paired T test between the treatments shows that in terms of soil acidification rate, the treatments followed the order of N > NPK > NPKM ≈ CK. The mean soil acidification rate under the N and NPK treatments was 4.6 and 3.2 times, respectively as high as that under control. Taking well-drained upland or upland-paddy rotation croplands in the humid or semi-humid zone as examples, the processes of soil acidification in the croplands were analyzed. The evolution of pH in topsoils of croplands was characterized as a common response to fertilization, regardless of certain regional differences.
The aims of this study were to explore the evolution of pH in topsoils under long-term different fertilization regimes, and further to understand the mechanisms and methods against soil acidification in croplands. We collected historical data on six 18–30 years long-term fertilization experiments in typical Chinese croplands of red soil in Qiyang and Jinxian, purple soil in Chongqing, black soil in Gongzhuling and Harbin with conventional and high fertilization rates, and then analyzed the differences in soil pH and acidification rate among experimental stages (six years each) and treatments, i.e., no-fertilizer control (CK), sole chemical nitrogen fertilizer (N), chemical nitrogen plus phosphorous and potassium fertilizers (NPK) and NPK fertilizers amended with manure (NPKM). Results show that under control, topsoil pHs declined somewhat and acidification rates averaged 0.013 pH a -1. Under the N treatment, topsoil pHs of the experiments in Qiyang, Gongzhuling and Harbin with conventional fertilization rate were lowered by 0.32–0.55 units at the initial 6 years and all the experiments by 0.64–1.46 units at the recent 6 years as compared with those under control. Topsoil pHs under the NPK treatment were obviously lower than those under the N treatment over the 1–12 years experimental period. However, topsoil pHs under the NPKM treatment were 0.30–0.53 units higher than those under the NPK treatment, and the two had a similar pH evolution curve. Paired T test between the treatments shows that in terms of soil acidification rate, the treatments followed the order of N > NPK > NPKM ≈ CK. The mean soil acidification rate under the N and NPK treatments was 4.6 and 3.2 times, respectively as high as that under control. Taking well-drained upland or upland-paddy rotation croplands in the humid or semi-humid zone as examples, the processes of soil acidification in the croplands were analyzed. The evolution of pH in topsoils of croplands was characterized as a common response to fertilization, regardless of certain regional differences.
2014, 51(4):683-698.
DOI: 10.11766/trxb201309160418
Abstract:
Microbe drives biogeochemical cycling of elements on Earth. Being the fourth most abundant element on earth and the most frequently utilized transition metal in the biosphere, iron (Fe) naturally undergoes active reactions between ferrous and ferric states in circumneutral-pH or acid environment. Due to instability of dissolved Fe(Ⅱ) and adsorptive capability of insoluble Fe(Ⅲ) compounds, active Fe cycling exerts a strong influence on soil geochemistry. Advances in geo-microbiology have transformed our understanding of the edaphic iron cycling from mere physico-chemical reaction to biogeochemical process over the past three decades. Fe ion, undergoing active oxidation-reduction reactions in all life forms, is required asan integral component in cellular processes. And it has been demonstrated that phylogenetically diverse groups of microbes can grow either aerobically or anaerobically using Fe as electron donor or electron acceptor to generate energy from Fe reduction and Fe oxidation in vitro or in vivo. In recent years, significant progresses have been made toward understanding the biochemical mechanisms of microorganisms catalyzing anaerobic reduction of Fe(Ⅲ) in the circumneutral pH environment. Shewanella and Geobacter are the two model organisms commonly used in studyingmechanisms of Fe-reduction, and the use of insoluble ferric oxyhydroxide minerals as terminal electron acceptors in anaerobic respiration through extracellular electron transfer (dissimilatory Fe(Ⅲ) reduction). Comparatively little information is available on mechanisms of Fe(Ⅱ) oxidation at neutral pH conditions. Microaerobic Fe(Ⅱ)-oxidizers, such as Gallionella andLeptothrix, active at circumneutral pH, could compete with O2 in abiotic oxidation of Fe(Ⅱ), forming Fe(Ⅲ) oxide encrustation specific to the oxic-anoxic interface of soil. Fe-oxidizing microbes are not limited to aerobic habitats, but can also oxidize iron under anaerobicconditions using NO3−[nitrate-dependent Fe(Ⅱ)oxidation], or CO2[phototrophic Fe(Ⅱ)oxidation] as the terminal electron acceptor. The microbial Fe(Ⅱ)-Fe(Ⅲ) wheel promotesvarious environmental or ecosystem processes, such as nutrient cycling and contaminant transformation, at the water-soil interphase. It is worthwhile to note that in anaerobic environments, microbial Fe(Ⅲ) reduction is an important pathwayof anaerobic degradation of organic matter. Besides, dissimilatory Fe(Ⅲ) reduction is a key process governing reduction of humic substances, reductive dechlorination and metals reduction. Furthermore, Fe(Ⅲ)-reducing bacteria successfully outcompetemethanogenenic bacteria for H2 as an energy source, which results in dropping of methane production in soil of high organic matter content. Fe(Ⅱ)-oxidizing microbes have been demonstrated to oxidize both soluble and insoluble Fe(Ⅱ), producing a variety of insoluble Fe(Ⅲ) mineral products. Owing to their high affinity on surface, bacteriogenic iron oxides are ameliorating agents and geochemical barriers for fixing heavy elements, thus generating a major influence on release, transport, immobilization and bioavailability of heavy metals in soil. As a whole, it is apparent that iron biogeochemical cyclingistightly linked to organic matter degradation, denitrification, methane production and metal immobilization, which is one of the most important issues in environmental science.The processes driving iron cycling are not instantaneous, and Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation occur simultaneously in adjacent (micro-scale) locations. Dissimilatory iron-reducing bacteria are found capable of excreting Fe(Ⅲ), resulting in anaerobic reduction of iron oxides in soil. Fe(Ⅱ) species in soils is usually soluble and highly mobile, and able to act as an electron donor for iron oxidizing bacteria. Thus, it is re-oxidized to Fe(Ⅲ), forming secondary iron minerals. So far, it is less understood that the key factors which control Fe-cyclingatcircumneutral pH include local gradients of oxygen, light, nitrate and ferrous iron. And recent researches have demonstrated that environmental organic matter, such as lactate, plays an important role in the transition of Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation. To sum up, in the paper, the authors highlight the process, mechanism and environmental significance of microbe-mediated iron biogeochemical cycling, particularly in circumneutral pH environment that prevailsin soil, and also demonstrate the coupling relationship between iron and other related elements in biogeochemical cycling. Furthermore, the authors discussed key factors controlling shift between Fe(Ⅱ) oxidation and Fe(Ⅲ) reduction. In the end, the authors present their outlook about priority direction of the research on biogeochemical cycling of Fe in soil environment.This review is believed to be conducive to understanding of iron biogeochemical processes in the environment and formation of new strategies for sustainable rational utilization of the soil resources in China.
Microbe drives biogeochemical cycling of elements on Earth. Being the fourth most abundant element on earth and the most frequently utilized transition metal in the biosphere, iron (Fe) naturally undergoes active reactions between ferrous and ferric states in circumneutral-pH or acid environment. Due to instability of dissolved Fe(Ⅱ) and adsorptive capability of insoluble Fe(Ⅲ) compounds, active Fe cycling exerts a strong influence on soil geochemistry. Advances in geo-microbiology have transformed our understanding of the edaphic iron cycling from mere physico-chemical reaction to biogeochemical process over the past three decades. Fe ion, undergoing active oxidation-reduction reactions in all life forms, is required asan integral component in cellular processes. And it has been demonstrated that phylogenetically diverse groups of microbes can grow either aerobically or anaerobically using Fe as electron donor or electron acceptor to generate energy from Fe reduction and Fe oxidation in vitro or in vivo. In recent years, significant progresses have been made toward understanding the biochemical mechanisms of microorganisms catalyzing anaerobic reduction of Fe(Ⅲ) in the circumneutral pH environment. Shewanella and Geobacter are the two model organisms commonly used in studyingmechanisms of Fe-reduction, and the use of insoluble ferric oxyhydroxide minerals as terminal electron acceptors in anaerobic respiration through extracellular electron transfer (dissimilatory Fe(Ⅲ) reduction). Comparatively little information is available on mechanisms of Fe(Ⅱ) oxidation at neutral pH conditions. Microaerobic Fe(Ⅱ)-oxidizers, such as Gallionella andLeptothrix, active at circumneutral pH, could compete with O2 in abiotic oxidation of Fe(Ⅱ), forming Fe(Ⅲ) oxide encrustation specific to the oxic-anoxic interface of soil. Fe-oxidizing microbes are not limited to aerobic habitats, but can also oxidize iron under anaerobicconditions using NO3−[nitrate-dependent Fe(Ⅱ)oxidation], or CO2[phototrophic Fe(Ⅱ)oxidation] as the terminal electron acceptor. The microbial Fe(Ⅱ)-Fe(Ⅲ) wheel promotesvarious environmental or ecosystem processes, such as nutrient cycling and contaminant transformation, at the water-soil interphase. It is worthwhile to note that in anaerobic environments, microbial Fe(Ⅲ) reduction is an important pathwayof anaerobic degradation of organic matter. Besides, dissimilatory Fe(Ⅲ) reduction is a key process governing reduction of humic substances, reductive dechlorination and metals reduction. Furthermore, Fe(Ⅲ)-reducing bacteria successfully outcompetemethanogenenic bacteria for H2 as an energy source, which results in dropping of methane production in soil of high organic matter content. Fe(Ⅱ)-oxidizing microbes have been demonstrated to oxidize both soluble and insoluble Fe(Ⅱ), producing a variety of insoluble Fe(Ⅲ) mineral products. Owing to their high affinity on surface, bacteriogenic iron oxides are ameliorating agents and geochemical barriers for fixing heavy elements, thus generating a major influence on release, transport, immobilization and bioavailability of heavy metals in soil. As a whole, it is apparent that iron biogeochemical cyclingistightly linked to organic matter degradation, denitrification, methane production and metal immobilization, which is one of the most important issues in environmental science.The processes driving iron cycling are not instantaneous, and Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation occur simultaneously in adjacent (micro-scale) locations. Dissimilatory iron-reducing bacteria are found capable of excreting Fe(Ⅲ), resulting in anaerobic reduction of iron oxides in soil. Fe(Ⅱ) species in soils is usually soluble and highly mobile, and able to act as an electron donor for iron oxidizing bacteria. Thus, it is re-oxidized to Fe(Ⅲ), forming secondary iron minerals. So far, it is less understood that the key factors which control Fe-cyclingatcircumneutral pH include local gradients of oxygen, light, nitrate and ferrous iron. And recent researches have demonstrated that environmental organic matter, such as lactate, plays an important role in the transition of Fe(Ⅲ) reduction and Fe(Ⅱ) oxidation. To sum up, in the paper, the authors highlight the process, mechanism and environmental significance of microbe-mediated iron biogeochemical cycling, particularly in circumneutral pH environment that prevailsin soil, and also demonstrate the coupling relationship between iron and other related elements in biogeochemical cycling. Furthermore, the authors discussed key factors controlling shift between Fe(Ⅱ) oxidation and Fe(Ⅲ) reduction. In the end, the authors present their outlook about priority direction of the research on biogeochemical cycling of Fe in soil environment.This review is believed to be conducive to understanding of iron biogeochemical processes in the environment and formation of new strategies for sustainable rational utilization of the soil resources in China.
1989, 26(3):280-286.
Abstract:
1. The content range of total soil nutrients of China are as follows:N: 0.04-0.38% P: 0.02-0.11% K: 0.05-2.5%. 2. Generally, the NPK content of soils under natural vegetative cover is higher than that under cultivation, and the nutrients content of paddy soils greater than that of dryland soils of the same origin. 3. Total and available nutrient levels of soils are mainly influentd by parent material,degree of weathering and histrry of cultivation.4.Almost all the soils of arable lands of China need nitrogen application,while about 1/3-1/2 of arable land area is deficient in phosphorus, and 1/4-1/3 deficient in potassium.5. The phosphorus level of soils deficient now in phosphorus is increasing gradually because of phosphorus fertilizer application, while that of soils not deficient now in phosphorus is ratting decreased because of phosphorus unbalance.6. The area of soils deficient in potassium has a tendency to increase.7. Based on the results now available, the sketch. maps of soil nitrogen, pbosphorw sad potassium status of China were compiled.
1. The content range of total soil nutrients of China are as follows:N: 0.04-0.38% P: 0.02-0.11% K: 0.05-2.5%. 2. Generally, the NPK content of soils under natural vegetative cover is higher than that under cultivation, and the nutrients content of paddy soils greater than that of dryland soils of the same origin. 3. Total and available nutrient levels of soils are mainly influentd by parent material,degree of weathering and histrry of cultivation.4.Almost all the soils of arable lands of China need nitrogen application,while about 1/3-1/2 of arable land area is deficient in phosphorus, and 1/4-1/3 deficient in potassium.5. The phosphorus level of soils deficient now in phosphorus is increasing gradually because of phosphorus fertilizer application, while that of soils not deficient now in phosphorus is ratting decreased because of phosphorus unbalance.6. The area of soils deficient in potassium has a tendency to increase.7. Based on the results now available, the sketch. maps of soil nitrogen, pbosphorw sad potassium status of China were compiled.
2010, 47(1):26-32.
DOI: 10.11766/trxb200805270105
Abstract:
Spatial variation and influencing factors of CEC of the soil in the Dagu River Basin were studied with geostatistical and multiple regression analysis methods. Results show that CEC of the soil in the upper and under layers displayed significant positive correlations with organic matter, clay and silt, and significant negative correlation with sand. The correlation coefficient was the biggest between CEC and clay, and the smallest between CEC and silt. In terms of contribution of the factors to CEC, they were in the order of clay > organic matter > sand, and the mean contribution of clay was 1.5~2.5 times as much as that of organic matter. The cokriging method, which used clay as instrumental variable, produced more accurate results than the ordinary kriging method, and reduced RMSE of the soils in the upper and under layers by 18.94% and 41.05%, respectively. Furthermore, the relationship between the secondary and the primary variables governed accuracy of the estimation. Soil CECs were higher in the middle east, northwest and middle southwest of the Dagu River Basin, but much lower in the north and southwest tip. Hence the two regions are critical ones for soil amelioration. The soil fertility therein can be improved by increasing application of organic manure and adopting other soil building practices.
Spatial variation and influencing factors of CEC of the soil in the Dagu River Basin were studied with geostatistical and multiple regression analysis methods. Results show that CEC of the soil in the upper and under layers displayed significant positive correlations with organic matter, clay and silt, and significant negative correlation with sand. The correlation coefficient was the biggest between CEC and clay, and the smallest between CEC and silt. In terms of contribution of the factors to CEC, they were in the order of clay > organic matter > sand, and the mean contribution of clay was 1.5~2.5 times as much as that of organic matter. The cokriging method, which used clay as instrumental variable, produced more accurate results than the ordinary kriging method, and reduced RMSE of the soils in the upper and under layers by 18.94% and 41.05%, respectively. Furthermore, the relationship between the secondary and the primary variables governed accuracy of the estimation. Soil CECs were higher in the middle east, northwest and middle southwest of the Dagu River Basin, but much lower in the north and southwest tip. Hence the two regions are critical ones for soil amelioration. The soil fertility therein can be improved by increasing application of organic manure and adopting other soil building practices.
2002, 39(1):29-36.
DOI: 10.11766/trxb200004040105
Abstract:
The process of cadmium adsorption and desorption on lndicotic Black(IB,Cambisols),Yellow Brown(YB,Luvisols)and Red(R,Ferrisols)soils as well as the influence of media's pH were investigated in detail.The presence of organic chemicals obviously influenced the processes of cadmium adsorption and desorption.Adsorption of Cd in YB and IB soils decreased in the presence of citric acid and EDTA,meanwhile,its desorption rate was lower than that obtained in the absence of organic chemicals,which suggests that the relatively unsaturated adsorption sites for Cd increased in the present of organic chemicals.For Red soil,Cd adsorption in the presence of citric acid and ED-TA increased with pH in low pH media but decreased in high pH one,which was very different from YB and IB soils.Further studies indicated that adsorbed Cd in red soil existed significantly as unex-changeable one,and desorption rate by 0.1 mol L-1 NaNO3 gave a peak-shape curve.
The process of cadmium adsorption and desorption on lndicotic Black(IB,Cambisols),Yellow Brown(YB,Luvisols)and Red(R,Ferrisols)soils as well as the influence of media's pH were investigated in detail.The presence of organic chemicals obviously influenced the processes of cadmium adsorption and desorption.Adsorption of Cd in YB and IB soils decreased in the presence of citric acid and EDTA,meanwhile,its desorption rate was lower than that obtained in the absence of organic chemicals,which suggests that the relatively unsaturated adsorption sites for Cd increased in the present of organic chemicals.For Red soil,Cd adsorption in the presence of citric acid and ED-TA increased with pH in low pH media but decreased in high pH one,which was very different from YB and IB soils.Further studies indicated that adsorbed Cd in red soil existed significantly as unex-changeable one,and desorption rate by 0.1 mol L-1 NaNO3 gave a peak-shape curve.
2012, 49(1):155-164.
DOI: 10.11766/trxb201103180094
Abstract:
Soil microorganisms are a driving force in material recycling and nutrient transformation in soil. However, for a long time, soil has been treated as a “black box” system, wherein microbial diversity and biochemical processes they participate in soil remain to be explored. Since most of the soil microorganisms are still quite hard to be isolated for culture, traditional culture methods are quite limited in helping reveal compositions and functions of soil microbial communities. The metagenomic method is able to explore the structures and functions (sequence-driven approach) of soil microbial community and to screen bioactive materials and new genes (function-driven approach) through extracting all microbial DNAs direct from environment samples and then sequencing or constructing clone library, thus breaking through the bottleneck of the traditional methods and greatly enriching the knowledge about soil microbial biodiversity and functions. While reviewing main procedures of the metagenomic technique, the paper focuses on the introduction to application of the next-generation sequencing (NGS) technologies in metagenomic research and processing of the huge volume of data it may produce. The new processes on soil microbial ecology with the metagenomic technique is then discussed. And in the end, the authors propose that research projects on soil metagenomics projects should be launched at the national level to explore soil microorganism communities and their variation, so as to contribute to the causes of bioresource exploitation, agricultural production and environment protection.
Soil microorganisms are a driving force in material recycling and nutrient transformation in soil. However, for a long time, soil has been treated as a “black box” system, wherein microbial diversity and biochemical processes they participate in soil remain to be explored. Since most of the soil microorganisms are still quite hard to be isolated for culture, traditional culture methods are quite limited in helping reveal compositions and functions of soil microbial communities. The metagenomic method is able to explore the structures and functions (sequence-driven approach) of soil microbial community and to screen bioactive materials and new genes (function-driven approach) through extracting all microbial DNAs direct from environment samples and then sequencing or constructing clone library, thus breaking through the bottleneck of the traditional methods and greatly enriching the knowledge about soil microbial biodiversity and functions. While reviewing main procedures of the metagenomic technique, the paper focuses on the introduction to application of the next-generation sequencing (NGS) technologies in metagenomic research and processing of the huge volume of data it may produce. The new processes on soil microbial ecology with the metagenomic technique is then discussed. And in the end, the authors propose that research projects on soil metagenomics projects should be launched at the national level to explore soil microorganism communities and their variation, so as to contribute to the causes of bioresource exploitation, agricultural production and environment protection.
2020, 57(5):1051-1059.
DOI: 10.11766/trxb202006240330
Abstract:
Soil science plays an important strategic role in ensuring sustainable development of the agriculture and the construction of ecological civilization in China. This paper briefly reviews the status quo and development trend of soil science research at home and abroad, analyzes national strategic needs and key scientific issues of the research on soil science in the future, and collates priority aspects and key strategic directions of the soil science of China over the next 5-10 years, such as earth’s critical zone process and evolution of soil functions, theories and technologies for improvement of farmland soil health and quality, regional soil mixed pollution processes and green remediation, soil biological process and function, in an attempt to further promote leaping development of the soil science in China.
Soil science plays an important strategic role in ensuring sustainable development of the agriculture and the construction of ecological civilization in China. This paper briefly reviews the status quo and development trend of soil science research at home and abroad, analyzes national strategic needs and key scientific issues of the research on soil science in the future, and collates priority aspects and key strategic directions of the soil science of China over the next 5-10 years, such as earth’s critical zone process and evolution of soil functions, theories and technologies for improvement of farmland soil health and quality, regional soil mixed pollution processes and green remediation, soil biological process and function, in an attempt to further promote leaping development of the soil science in China.
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.
2015, 52(6):1311-1324.
DOI: 10.11766/trxb201501270058
Abstract:
Application of nitrogen fertilizer is an important approach to ensurance of food security in China. In recent years a large volume of nitrogen fertilizer applied has, though, increased crop yields significantly, it has also at the same time brought about a series of serious environmental problems. So, it is of great importance to get to know well the current situation of nitrogen use efficiency in China, to how to coordinate agricultural benefit with environmental impacts of the use of nitrogen fertilizer in formulating a reasonable fertilization strategy. Therefore, on the basis of the researches accomplished in the 1980s and 2001—2005, nitrogen use efficiencies in the resent 10 years of major grain crops in China were analyzed in this research. The literature research method was used to retrieve all the papers (in Chinese) related to the subject of crop response to nitrogen fertilizer application from the CNKI and VIP databases published after 2004. Results show that currently the basic yields of the three major grain crops without nitrogen fertilization could reach up to 67.9%~75.9% of the maximum yields of the crops with nitrogen fertilization. Yield response of rice, wheat and maize to nitrogen fertilizer application might reach up to 43.0%, 28.2% and 25.8%, respectively. Based on the regression equation of nitrogen application rates and relative yields, the nitrogen application rate for maximum yield of rice, wheat and maize was 246, 250 and 274 kghm-2, respectively. In the recent 10 years, both the apparent recovery rate (REN) and agronomic efficiency of applied nitrogen(AEN) somewhat increased, reaching up to 39.0%, 34.8% and 29.1%, and 12.7, 9.2 and 11.1 kgkg-1, respectively, for rice, wheat and maize. Compared with the statistics of the period (2001—2005), REN increased by 6.8%, almost reaching 35% of the level in the 1980s. The relationship between nitrogen application rate and partial factor productivity (PFPN) of nitrogen fertilizer could be well described with the power exponent equation for all the three major crops, with R2 for rice, wheat and maize being 0.8489, 0.6575 and 0.7917, respectively. Currently, PFPN is an appropriate index for use in evaluating nitrogen fertilizer utilization efficiency. Taking into overall account target yieldsand nitrogen use efficiencies of the three major grain crops, it is held that 180~240 kghm-2is the proper N application rate for all the three crops in China today, and quite in consistence with the recommendation in the “Fertilizer Formulas and Fertilization Recommendations for Wheat, Maize and Rice in their Major Production Regions” promulgatedand distributed by the Ministry of Agriculture of China.
Application of nitrogen fertilizer is an important approach to ensurance of food security in China. In recent years a large volume of nitrogen fertilizer applied has, though, increased crop yields significantly, it has also at the same time brought about a series of serious environmental problems. So, it is of great importance to get to know well the current situation of nitrogen use efficiency in China, to how to coordinate agricultural benefit with environmental impacts of the use of nitrogen fertilizer in formulating a reasonable fertilization strategy. Therefore, on the basis of the researches accomplished in the 1980s and 2001—2005, nitrogen use efficiencies in the resent 10 years of major grain crops in China were analyzed in this research. The literature research method was used to retrieve all the papers (in Chinese) related to the subject of crop response to nitrogen fertilizer application from the CNKI and VIP databases published after 2004. Results show that currently the basic yields of the three major grain crops without nitrogen fertilization could reach up to 67.9%~75.9% of the maximum yields of the crops with nitrogen fertilization. Yield response of rice, wheat and maize to nitrogen fertilizer application might reach up to 43.0%, 28.2% and 25.8%, respectively. Based on the regression equation of nitrogen application rates and relative yields, the nitrogen application rate for maximum yield of rice, wheat and maize was 246, 250 and 274 kghm-2, respectively. In the recent 10 years, both the apparent recovery rate (REN) and agronomic efficiency of applied nitrogen(AEN) somewhat increased, reaching up to 39.0%, 34.8% and 29.1%, and 12.7, 9.2 and 11.1 kgkg-1, respectively, for rice, wheat and maize. Compared with the statistics of the period (2001—2005), REN increased by 6.8%, almost reaching 35% of the level in the 1980s. The relationship between nitrogen application rate and partial factor productivity (PFPN) of nitrogen fertilizer could be well described with the power exponent equation for all the three major crops, with R2 for rice, wheat and maize being 0.8489, 0.6575 and 0.7917, respectively. Currently, PFPN is an appropriate index for use in evaluating nitrogen fertilizer utilization efficiency. Taking into overall account target yieldsand nitrogen use efficiencies of the three major grain crops, it is held that 180~240 kghm-2is the proper N application rate for all the three crops in China today, and quite in consistence with the recommendation in the “Fertilizer Formulas and Fertilization Recommendations for Wheat, Maize and Rice in their Major Production Regions” promulgatedand distributed by the Ministry of Agriculture of China.
2017, 54(4):819-826.
DOI: 10.11766/trxb201703310602
Abstract:
For a long time, quite a number of people one-sidedly believe that soil science is merely an applied science, and its research tools are merely experimental, while its research methodology should be holistic and integrative. In this paper, systems analysis was done of the perniciousness of this one-sided presumption to development of the soil science, and it was proposed that development of the soil science in future should stress the use of analytical methods and a natural systematic integration should be realized on the basis of such in-depth analyses. Three basic viewpoints were then put forward and elaborated: 1) it is essential to be fully aware that the peculiarities of the soil systems root in their fundamental impacts on subatomic structures. For example, in common aqueous solutions, Li , K and Cs will definitely not exceed 1.00 in effective charge and instead should fall below 1.00 due to cationic volumes and hydration effects; however, their effective charges burgeon respectively to 1.05, 1.94 and 2.40 when these ions are placed at the interface of clays in aqueous solutions, as a result of the profound impact of clay on the energetic and quantum states of these cation electrons. In other words, cations (as well as atoms and molecules) at clay interfaces are essentially different from those in aqueous solutions. 2) Considering peculiarities of the soil systems, methodologically the soils should be hierarchized by scale i.e. macroscopic, mesoscopic, molecular, atomic and subatomic scales, and eventually analyzed by means of the principles and methodology of quantum mechanics at the subatomic scale. And 3) Through researches based on the quantum effect unique to the soil, direct correlations between subatomic structures, soil microscopic mechanisms and macroeffect could be established, hence to realize, an natural conversion of scientific principles between different scales of soil. And in the end an independent and self-consistent pedological knowledge system will be constituted. Here it is a must to emphasize that this paper is intended to provide some ideas about methodology of the research on basic soil science. Although it may be too much of a generalization for our arguments to be just supported by several special examples, the particularities of the soil systems those samples reflect sufficiently express the necessity to establish an independent and self-consistent knowledge system for soil science, and the importance of analytical methods in the establishment.
For a long time, quite a number of people one-sidedly believe that soil science is merely an applied science, and its research tools are merely experimental, while its research methodology should be holistic and integrative. In this paper, systems analysis was done of the perniciousness of this one-sided presumption to development of the soil science, and it was proposed that development of the soil science in future should stress the use of analytical methods and a natural systematic integration should be realized on the basis of such in-depth analyses. Three basic viewpoints were then put forward and elaborated: 1) it is essential to be fully aware that the peculiarities of the soil systems root in their fundamental impacts on subatomic structures. For example, in common aqueous solutions, Li , K and Cs will definitely not exceed 1.00 in effective charge and instead should fall below 1.00 due to cationic volumes and hydration effects; however, their effective charges burgeon respectively to 1.05, 1.94 and 2.40 when these ions are placed at the interface of clays in aqueous solutions, as a result of the profound impact of clay on the energetic and quantum states of these cation electrons. In other words, cations (as well as atoms and molecules) at clay interfaces are essentially different from those in aqueous solutions. 2) Considering peculiarities of the soil systems, methodologically the soils should be hierarchized by scale i.e. macroscopic, mesoscopic, molecular, atomic and subatomic scales, and eventually analyzed by means of the principles and methodology of quantum mechanics at the subatomic scale. And 3) Through researches based on the quantum effect unique to the soil, direct correlations between subatomic structures, soil microscopic mechanisms and macroeffect could be established, hence to realize, an natural conversion of scientific principles between different scales of soil. And in the end an independent and self-consistent pedological knowledge system will be constituted. Here it is a must to emphasize that this paper is intended to provide some ideas about methodology of the research on basic soil science. Although it may be too much of a generalization for our arguments to be just supported by several special examples, the particularities of the soil systems those samples reflect sufficiently express the necessity to establish an independent and self-consistent knowledge system for soil science, and the importance of analytical methods in the establishment.
2013, 50(1):1-11.
DOI: 10.11766/trxb201111220461
Abstract:
In an agricultural ecosystem, soil organic matter (SOM) is an index key to estimating soil C sequestration, soil fertility and quality, etc. Estimation of these soil properties at an acceptable level of accuracy is very important. In this research, a square area (116°45′32″~117°2′14″E，34°31′12″~34°45′6″N), about 580 km2, was chosen as an example in the northwest of the Xu-Huai alluvial plain (Xuzhou and Huaiyin). A total of 168 soil samples were collected according to nested scenario’s, for analysis of SOM content and soil texture. And furthermore, spatial variability of SOM in the surface layer of this region was analyzed using the geostatistics and GIS method, and its dominating factors, too, by means of variance analysis and regression analysis. Descriptive statistics of the results shows that the SOM content of the region varying in the range of 21.80 ± 7.43 g kg-1 with a variation coefficient being 34.08%, both belonging to a moderate level. Geostatistical analysis suggests that the study area was very strong in spatial autocorrelation and structural factors played a dominating role in spatial variability of SOM, which was significant in anisotropy. The variation at 45° in direction was the most severe. SOM in the area was distributed in a band, decreasing from northeast to southwest. Variance analysis and stepwise regression analysis indicates that mechanical composition of the soil was the dominating factor, which alone could explain 64.9% of the SOM spatial variability of the region, and land use, parent material and soil type followed in role. The four factors together could explain 74.6% of the variability of SOM in the study area.
In an agricultural ecosystem, soil organic matter (SOM) is an index key to estimating soil C sequestration, soil fertility and quality, etc. Estimation of these soil properties at an acceptable level of accuracy is very important. In this research, a square area (116°45′32″~117°2′14″E，34°31′12″~34°45′6″N), about 580 km2, was chosen as an example in the northwest of the Xu-Huai alluvial plain (Xuzhou and Huaiyin). A total of 168 soil samples were collected according to nested scenario’s, for analysis of SOM content and soil texture. And furthermore, spatial variability of SOM in the surface layer of this region was analyzed using the geostatistics and GIS method, and its dominating factors, too, by means of variance analysis and regression analysis. Descriptive statistics of the results shows that the SOM content of the region varying in the range of 21.80 ± 7.43 g kg-1 with a variation coefficient being 34.08%, both belonging to a moderate level. Geostatistical analysis suggests that the study area was very strong in spatial autocorrelation and structural factors played a dominating role in spatial variability of SOM, which was significant in anisotropy. The variation at 45° in direction was the most severe. SOM in the area was distributed in a band, decreasing from northeast to southwest. Variance analysis and stepwise regression analysis indicates that mechanical composition of the soil was the dominating factor, which alone could explain 64.9% of the SOM spatial variability of the region, and land use, parent material and soil type followed in role. The four factors together could explain 74.6% of the variability of SOM in the study area.
2015, 52(3):469-476.
DOI: 10.11766/trxb201411040554
Abstract:
With farming cultivation increasing steadily in intensiveness, obstacles to successive cropping, such as soil-borne pathogens, soil acidification, secondary salinization and unbalanced nutrient supply, occur more frequently, and seriously sabotage sustainability of the intensive agriculture. The threat is even more serious in China due to excessive application of N fertilizers and farmers’ poor knowledge about intensive agriculture. Firstly developed in Japan and the Netherlands in the early 2000’s as an alternative of chemical soil disinfestationand named as biological soil disinfestation (BSD) or reductive soil disinfestation (RSD) in Japan or anaerobic soil disinfestation (ASD) in the Netherlands and the USA, the method is now being widely applied in these countries. RSD refers to the pre-planting soil treatment method, i.e. applying decomposable organic materials at a very high rate to the soils infested with soil-borne pathogens, flooding or irrigating the field to water saturation, and mulching the field with plastic film to limit gas exchange between the soil and the atmosphere and create the soil in a very intensively reductive state for a short period of time (a few days). The method can be conducted in the fallow season between two crops when temperature is higher than 25℃ and the treatment usually lasts 2~4 weeks mainly depending on temperature, amount of the organic material applied, and population of pathogens. The researches have demonstrated that the method controls a broad-spectrum of pests and is an alternative to chemical fumigation with gaseous pesticides, such as methyl bromide, effective to eliminate or reduce the populations of fungal and bacterial pathogens and root-knot nematodes. The mechanisms of RSD for disinfestation include: 1) creating an anaerobic condition that kills aerobic soil-borne pathogens; 2) producing substances harmful and toxic to the pathogens during the treatment period; and 3) altering structure of the soil microbial community and inhibiting the activity ofsoil-borne pathogens. Besides, the RSD method has some effects of increasing soil pH and alleviating soil secondary salinization, and its application is universal and environment-friendly. An introduction is presented in the paper to the development, mechanisms for suppressing soil-borne pathogens and remediation of acidified or secondarily salinized soils, and factors influencing the effectiveness of the RSD method and prospects of the application of the method as well.
With farming cultivation increasing steadily in intensiveness, obstacles to successive cropping, such as soil-borne pathogens, soil acidification, secondary salinization and unbalanced nutrient supply, occur more frequently, and seriously sabotage sustainability of the intensive agriculture. The threat is even more serious in China due to excessive application of N fertilizers and farmers’ poor knowledge about intensive agriculture. Firstly developed in Japan and the Netherlands in the early 2000’s as an alternative of chemical soil disinfestationand named as biological soil disinfestation (BSD) or reductive soil disinfestation (RSD) in Japan or anaerobic soil disinfestation (ASD) in the Netherlands and the USA, the method is now being widely applied in these countries. RSD refers to the pre-planting soil treatment method, i.e. applying decomposable organic materials at a very high rate to the soils infested with soil-borne pathogens, flooding or irrigating the field to water saturation, and mulching the field with plastic film to limit gas exchange between the soil and the atmosphere and create the soil in a very intensively reductive state for a short period of time (a few days). The method can be conducted in the fallow season between two crops when temperature is higher than 25℃ and the treatment usually lasts 2~4 weeks mainly depending on temperature, amount of the organic material applied, and population of pathogens. The researches have demonstrated that the method controls a broad-spectrum of pests and is an alternative to chemical fumigation with gaseous pesticides, such as methyl bromide, effective to eliminate or reduce the populations of fungal and bacterial pathogens and root-knot nematodes. The mechanisms of RSD for disinfestation include: 1) creating an anaerobic condition that kills aerobic soil-borne pathogens; 2) producing substances harmful and toxic to the pathogens during the treatment period; and 3) altering structure of the soil microbial community and inhibiting the activity ofsoil-borne pathogens. Besides, the RSD method has some effects of increasing soil pH and alleviating soil secondary salinization, and its application is universal and environment-friendly. An introduction is presented in the paper to the development, mechanisms for suppressing soil-borne pathogens and remediation of acidified or secondarily salinized soils, and factors influencing the effectiveness of the RSD method and prospects of the application of the method as well.
2017, 54(4):805-818.
DOI: 10.11766/trxb201611040406
Abstract:
Soil is the largest terrestrial organic carbon sink, and soil organic matter is the main form of the carbon stored in the sink. In view of the fact that soil organic matter plays an important role in the ecological system and carbon storage, the topic of soil minerals adsorbing organic matter and its mechanism is getting more and more attention from scientists the world over. This paper presents a review of the papers published in the past years about the mechanisms of soil minerals adsorbing organic matter and its major affecting factors. It is reported that among a huge number of soil minerals, hydrated iron, aluminum oxides and clay minerals are quite high in organic matter adsorbing capacity, ligand exchange, complexation, hydrogen bond, cationic bridge, condensation and Van der Waals force, the main mechanisms, and soil pH, the key factor that influences surface charge and adsorption sites of the mineral and hence adsorption of organic matter. Amount of the soil organic matter already adsorbed on the surface of the minerals also affects somewhat capacity of the minerals keeping on adsorbing organic matter, because the already adsorbed organic matter forms a layer covering part of the surface of the minerals and adsorbing sites thereon, and the closer the layer to the surface of the minerals, the tighter it adsorbed onto the minerals. Stability of the soil organic matter is affected significantly by the interaction between the organic matter and the minerals. Generally speaking, the adsorption of organic matter via chemical bond is the most stable and followed by that via Electronic “Donor-Acceptor” mechanism (which shows inner-sphere complex between functional groups on the surface of the minerals and the organic matter), and that via Van der Waals force and electrostatic force, in the end. In recent years, with the development of analytic equipment and technologies, some new characterizing and probing methods, such as TG, DSC, FTIR, SEM, TEM, AFM, STXM/NEXAFS, Neutron Scattering, have been invented and used in the studies on mechanisms of mineral-organic matter associations (MOAs). These instrument developments will undoubtedly bring important new insights into mechanisms of MOAs. However, relatively little has been reported about effects of microorganisms on mineral adsorption of organic matter, formation and evolution of MOA, though it is quite obvious that their effects are crucial.
Soil is the largest terrestrial organic carbon sink, and soil organic matter is the main form of the carbon stored in the sink. In view of the fact that soil organic matter plays an important role in the ecological system and carbon storage, the topic of soil minerals adsorbing organic matter and its mechanism is getting more and more attention from scientists the world over. This paper presents a review of the papers published in the past years about the mechanisms of soil minerals adsorbing organic matter and its major affecting factors. It is reported that among a huge number of soil minerals, hydrated iron, aluminum oxides and clay minerals are quite high in organic matter adsorbing capacity, ligand exchange, complexation, hydrogen bond, cationic bridge, condensation and Van der Waals force, the main mechanisms, and soil pH, the key factor that influences surface charge and adsorption sites of the mineral and hence adsorption of organic matter. Amount of the soil organic matter already adsorbed on the surface of the minerals also affects somewhat capacity of the minerals keeping on adsorbing organic matter, because the already adsorbed organic matter forms a layer covering part of the surface of the minerals and adsorbing sites thereon, and the closer the layer to the surface of the minerals, the tighter it adsorbed onto the minerals. Stability of the soil organic matter is affected significantly by the interaction between the organic matter and the minerals. Generally speaking, the adsorption of organic matter via chemical bond is the most stable and followed by that via Electronic “Donor-Acceptor” mechanism (which shows inner-sphere complex between functional groups on the surface of the minerals and the organic matter), and that via Van der Waals force and electrostatic force, in the end. In recent years, with the development of analytic equipment and technologies, some new characterizing and probing methods, such as TG, DSC, FTIR, SEM, TEM, AFM, STXM/NEXAFS, Neutron Scattering, have been invented and used in the studies on mechanisms of mineral-organic matter associations (MOAs). These instrument developments will undoubtedly bring important new insights into mechanisms of MOAs. However, relatively little has been reported about effects of microorganisms on mineral adsorption of organic matter, formation and evolution of MOA, though it is quite obvious that their effects are crucial.
