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Yong-guan Zhu - One of the best experts on this subject based on the ideXlab platform.
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identification of potential electrotrophic microbial community in Paddy Soils by enrichment of microbial electrolysis cell biocathodes
Journal of Environmental Sciences-china, 2020Co-Authors: Longjun Ding, Haiyan Yuan, Yong-guan ZhuAbstract:Abstract Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in Paddy Soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five Paddy Soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%–45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all Soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different Soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in Paddy Soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.
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changes in archaeal ether lipid composition in response to agriculture alternation in ancient and modern Paddy Soils
Organic Geochemistry, 2019Co-Authors: Yong-guan Zhu, Fengfeng Zheng, Yufei Chen, Xiaotong Tang, Chuanlun ZhangAbstract:Abstract Paddy soil is the consequence of human activity, which has exerted significant anthropogenic impacts on the global carbon cycle in recent earth history, particularly through the production of microbial methane from Paddy Soils. However, the anthropogenic impact of rice fields on the distribution of methanogenic archaea and methane emission during human history is poorly documented. Isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) are unique biomarkers for archaea, which can be used to examine changes in climate and environment during human evolution. This study aimed to reconstruct archaeal communities and evaluate how they might have been impacted by human activities during the development of two Paddy soil profiles that recorded a cultivation history of over 6300 years in Zhejiang Province, southeastern China. Variations in archaeol, GDGT-0 and crenarchaeol strongly suggest that archaeal ether lipids deeply buried in the ancient Paddy soil profiles are mainly fossil records rather than contemporary signals. Cluster analysis based on GDGT compositions revealed two major groups of GDGTs corresponding to different soil types, reflecting the shift of archaeal communities from Thaumarchaeota to methanogens. The archaeal ether lipid-based proxies (MI, archaeol/crenarchaeol and GDGT-0/crenarchaeol) related to methane-producing archaea varied remarkably in different soil types associated with the anthropogenic management. These proxies had significantly higher values in the buried Paddy Soils than currently cultivated Paddy Soils, implying that the earlier anthropogenic flooding may have resulted in considerable methane emission from Paddy Soils in southeastern China.
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molecular chemodiversity of dissolved organic matter in Paddy Soils
Environmental Science & Technology, 2018Co-Authors: Guoxin Sun, Quan Shi, Songcan Chen, Zhi Fang, Haiyan Yuan, Yong-guan ZhuAbstract:Organic matter (OM), and dissolved organic matter (DOM), have a major influence upon biogeochemical processes; most significantly, the carbon cycle. To date, very few studies have examined the spatial heterogeneity of DOM in Paddy Soils. Thus, very little is known about the DOM molecular profiles and the key environmental factors that underpin DOM molecular chemodiversity in Paddy Soils. Here, Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry was applied to unambiguously resolve 11 361 molecular formulas in 16 Paddy Soils; thereby elucidating the molecular characteristics of Paddy soil DOM. Soil pH, iron complexing index (Fep/FeR) and C/N ratio were established to be key factors controlling DOM profiles. Polycyclic aromatics (derived from combustion) and polyphenols (derived from plants) increased with increasing pH, while polyphenols molecules, pyrogenic aromatics, and carboxylic compounds decreased with increasing iron complexing index. Patterns in molecular profiles indicated DOM in Paddy soi...
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metagenomic analysis revealed highly diverse microbial arsenic metabolism genes in Paddy Soils with low arsenic contents
Environmental Pollution, 2016Co-Authors: Keqing Xiao, Si-yu Zhang, Peng Bao, Tong Zhang, Yong-guan ZhuAbstract:Microbe-mediated arsenic (As) metabolism plays a critical role in global As cycle, and As metabolism involves different types of genes encoding proteins facilitating its biotransformation and transportation processes. Here, we used metagenomic analysis based on high-throughput sequencing and constructed As metabolism protein databases to analyze As metabolism genes in five Paddy Soils with low-As contents. The results showed that highly diverse As metabolism genes were present in these Paddy Soils, with varied abundances and distribution for different types and subtypes of these genes. Arsenate reduction genes (ars) dominated in all soil samples, and significant correlation existed between the abundance of arr (arsenate respiration), aio (arsenite oxidation), and arsM (arsenite methylation) genes, indicating the co-existence and close-relation of different As resistance systems of microbes in wetland environments similar to these Paddy Soils after long-term evolution. Among all soil parameters, pH was an important factor controlling the distribution of As metabolism gene in five Paddy Soils (p = 0.018). To the best of our knowledge, this is the first study using high-throughput sequencing and metagenomics approach in characterizing As metabolism genes in the five Paddy soil, showing their great potential in As biotransformation, and therefore in mitigating arsenic risk to humans.
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diversity and abundance of arsenic biotransformation genes in Paddy Soils from southern china
Environmental Science & Technology, 2015Co-Authors: Si-yu Zhang, Xiao-ru Yang, Guoxin Sun, Fangjie Zhao, Yong-guan ZhuAbstract:Microbe-mediated arsenic (As) biotransformation in Paddy Soils determines the fate of As in Soils and its availability to rice plants, yet little is known about the microbial communities involved in As biotransformation. Here, we revealed wide distribution, high diversity, and abundance of arsenite (As(III)) oxidase genes (aioA), respiratory arsenate (As(V)) reductase genes (arrA), As(V) reductase genes (arsC), and As(III) S-adenosylmethionine methyltransferase genes (arsM) in 13 Paddy Soils collected across Southern China. Sequences grouped with As biotransformation genes are mainly from rice rhizosphere bacteria, such as some Proteobacteria, Gemmatimonadales, and Firmicutes. A significant correlation of gene abundance between arsC and arsM suggests that the two genes coexist well in the microbial As resistance system. Redundancy analysis (RDA) indicated that soil pH, EC, total C, N, As, and Fe, C/N ratio, SO4(2-)-S, NO3(-)-N, and NH4(+)-N were the key factors driving diverse microbial community compositions. This study for the first time provides an overall picture of microbial communities involved in As biotransformation in Paddy Soils, and considering the wide distribution of Paddy fields in the world, it also provides insights into the critical role of Paddy fields in the As biogeochemical cycle.
Jizheng He - One of the best experts on this subject based on the ideXlab platform.
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contrasting euryarchaeota communities between upland and Paddy Soils exhibited similar ph impacted biogeographic patterns
Soil Biology & Biochemistry, 2013Co-Authors: Hangwei Hu, Chaolei Yuan, Jizheng He, Limei ZhangAbstract:Euryarchaeota, as an important and ubiquitous Archaea phylum, contributes substantially to global energy cycling. However, there is a considerable lack of knowledge regarding their biogeographic patterns in terrestrial ecosystems. Here barcoded pyrosequencing was employed to compare the relative abundance, diversity and community composition of Euryarchaeota in 92 soil samples, collected from a variety of ecosystem types. A total of 96,534 euryarchaeal sequences were classified from pyrosequencing of the archaeal 16S rRNA gene, comprising 22.5% of the total archaeal sequences detected. Paddy Soils harbored contrasting Euryarchaeota communities from upland Soils (including cropland, grassland, forest, and tea orchard soil), at all taxonomic resolutions from phylum to genus level. Within upland Soils, the relative abundance of Euryarchaeota in Archaea, and Euryarchaeota operational taxonomic unit (OTU) richness are significantly influenced by soil pH and H2O%. Similar observations held true for the beta diversity patterns, with soil pH and H2O% best explaining the variance of the pairwise Bray–Curtis dissimilarity. By comparison, within Paddy Soils, the Euryarchaeota abundance in Archaea, and the alpha and beta diversity patterns, could be best predicted along the gradients of soil pH and NH4+-N. These findings were further corroborated by the evident pH-, H2O%- or NH4+-N-associated distributions of several major Euryarchaeota orders. Taken together, our results emphasized the significant importance of soil pH as the prevailing environmental factor in shaping the terrestrial Euryarchaeota.
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contrasting euryarchaeota communities between upland and Paddy Soils exhibited similar ph impacted biogeographic patterns
Soil Biology & Biochemistry, 2013Co-Authors: Hangwei Hu, Chaolei Yuan, Jizheng He, Limei ZhangAbstract:Euryarchaeota, as an important and ubiquitous Archaea phylum, contributes substantially to global energy cycling. However, there is a considerable lack of knowledge regarding their biogeographic patterns in terrestrial ecosystems. Here barcoded pyrosequencing was employed to compare the relative abundance, diversity and community composition of Euryarchaeota in 92 soil samples, collected from a variety of ecosystem types. A total of 96,534 euryarchaeal sequences were classified from pyrosequencing of the archaeal 16S rRNA gene, comprising 22.5% of the total archaeal sequences detected. Paddy Soils harbored contrasting Euryarchaeota communities from upland Soils (including cropland, grassland, forest, and tea orchard soil), at all taxonomic resolutions from phylum to genus level. Within upland Soils, the relative abundance of Euryarchaeota in Archaea, and Euryarchaeota operational taxonomic unit (OTU) richness are significantly influenced by soil pH and H2O%. Similar observations held true for the beta diversity patterns, with soil pH and H2O% best explaining the variance of the pairwise Bray–Curtis dissimilarity. By comparison, within Paddy Soils, the Euryarchaeota abundance in Archaea, and the alpha and beta diversity patterns, could be best predicted along the gradients of soil pH and NH4+-N. These findings were further corroborated by the evident pH-, H2O%- or NH4+-N-associated distributions of several major Euryarchaeota orders. Taken together, our results emphasized the significant importance of soil pH as the prevailing environmental factor in shaping the terrestrial Euryarchaeota.
Xinhua Peng - One of the best experts on this subject based on the ideXlab platform.
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macropores generated during shrinkage in two Paddy Soils using x ray micro computed tomography
Geoderma, 2016Co-Authors: Nicolas Bottinelli, Hu Zhou, Z. B. Zhang, P Boivin, Pascal Jouquet, Christian Hartmann, Xinhua PengAbstract:Soil shrinkage curve represents a decrease of total porosity or an increase of bulk density with water loss. However, our knowledge of the dynamics of pores and their geometry during soil shrinkage is scarce, partially due to lack of reliable methods for determining soil pores in relation to change in soil water. This study aimed to investigate the dynamics of macropores (>30 mu m) of Paddy Soils during shrinkage. Two, Paddy Soils, which were sampled from one Paddy field cultivated for 20 years (YPF) and the other one for over 100 years (OPF), represented difference in crack geometry in the field. Macropore parameters (volume, connectivity, and orientation of pores) and soil shrinkage parameters were determined on the same undisturbed soil cores by X-ray microtomography and shrinkage curve, respectively. Macroporosity was on average four times larger in the YPF than in the OPF whereas the shrinkage capacity was lower in the YPF as compared to the OPF (0.09 vs. 0.15 COLE). Soil shrinkage increased the volume of pores by 3.7% in the YPF and by 1.6% in the OPF as well as their connectivity. The formation of macropores occurred mostly in the proportional shrinkage phase. As a result, the slope of the proportional shrinkage phase was smaller in the YPF (0.65) than in the OPF (0.89). New macropores were cracks and extended pre-existing pores in the range of 225-1215 pm size without any preferential orientation. This work provides image evidences that in Paddy Soils with high shrinkage capacity more macropores are generated in the soil presenting a smaller proportional shrinkage slope. (C) 2015 Elsevier B.V. All rights reserved.
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puddling intensity sesquioxides and soil organic carbon impacts on crack patterns of two Paddy Soils
Geoderma, 2016Co-Authors: Z. B. Zhang, H Zhou, Hangsheng Lin, Xinhua PengAbstract:Abstract Paddy Soils subjected to puddling are easily cracked under wetting and drying cycles. This phenomenon has implications for water loss and chemical leaching in Paddy fields. We hypothesized that crack patterns in such Paddy Soils result from aggregate size distribution created by puddling under submerged condition. Soil organic carbon (SOC) and sesquioxides are main binding agents of aggregation while puddling is a disruptive force of aggregates. In this study, our aim was to investigate the effects of puddling intensity, SOC, and sesquioxides on cracking in two Paddy Soils — one cultivated for 20 years (YPF soil) and the other cultivated for over 100 years (OPF soil). The puddling intensity was simulated by ultrasonic dispersion at applied energy of 0–800 J ml− 1. The Soils were treated chemically by water as a control as well as by oxalate, dithionite-citrate-bicarbonate (DCB), or by H2O2. The aggregate size distribution and crack patterns were determined after the simulated puddling and the chemical treatments. The results showed that the simulated puddling and the chemical treatments increased clay- (
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characterizing preferential flow in cracked Paddy Soils using computed tomography and breakthrough curve
Soil & Tillage Research, 2015Co-Authors: Z. B. Zhang, Xinhua Peng, Hu ZhouAbstract:Abstract Soil cracks generated in Paddy fields may change soil structure and provide pathways for preferential flow. However, the quantitative relationship between soil cracks and preferential flow remain unclear in Paddy Soils. The objectives of this study were to (1) reveal the effect of soil cracking on soil structure and preferential flow, (2) find a quantitative relationship between characteristics of soil structure and preferential flow in two Paddy fields. Two Paddy fields, one cultivated for 20 years (YPF) and the other cultivated for more than 100 years (OPF), were subjected to either alternate flooding and drying (AFD) or continuous flooding (CF) (as a control) during rice growing season. Undisturbed soil columns (10 cm in diameter and 20 cm in height) were sampled in the four plots. Macropores (including cracks) were quantified using computed tomography (CT), and preferential flow was assessed by breakthrough curve (BTC). The results showed that the presence of soil cracks under the AFD increased average macropore length but decreased the number of macropores significantly ( P λ and λ eff ) were poor ( P > 0.05). Both the shape of BTCs and fitting parameters demonstrated that soil cracks (5.31–11.9 cm depth) did not increase preferential flow because they did not perforate through the dense plow pan. Soil columns in the CF plots displayed a bit more preferential flow due to a deeper macropore distribution as compared with the AFD plots. While macropore features were different at the two Paddy Soils, the difference in preferential flow was reduced due to the presence of plow pan. This study demonstrates that soil cracks significantly affect macropore structure but their impact on preferential flow may be poor when they do not penetrate through the plow pan.
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temporal changes in shrinkage behavior of two Paddy Soils under alternative flooding and drying cycles and its consequence on percolation
Geoderma, 2013Co-Authors: Zhongbin Zhang, Xinhua Peng, Liang Wang, Qingqing Zhao, Henry LinAbstract:Paddy field is generally subjected to many cycles of alternative flooding and drying (AFD) during rice growing. The AFD cycles can create a large variation in soil structure that subsequently affects soil water and nutrient retention and migration. This study aimed to investigate the temporal change in soil shrinkage behaviour and to evaluate its consequences on water percolation in two Paddy fields under AFD. One Paddy field cultivated for 20 years (YPF) and the other one for over 100 years (OPF) were subjected to either AFD or continuous flooding (CF) as a control. During every AFD cycle, soil cores were sampled to determine soil shrinkage curve in the laboratory while cracks and water percolation were determined in the field. Our results showed that both Paddy Soils presented a temporal change in soil bulk density, soil shrinkage and cracks with cycles of AFD. The two Paddy Soils showed a high shrinkage capacity (COLE > 0.06), in which the OPF was significantly greater than the YPF (P < 0.001). The cracks area density, however, was lower in the OPF (3.66%) than in the YPF (5.13%). This discrepancy can be explained by more swelling clay content and higher soil organic matter in the OPF but greater AFD intensity in the YPF. As a result, the YPF showed higher water percolation as compared with the OPF. Our work demonstrates that the temporal changes in soil structure in Paddy Soils depend not only on intrinsic soil properties but also on external hydraulic stress.
Georg Guggenberger - One of the best experts on this subject based on the ideXlab platform.
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rice Paddy Soils are a quantitatively important carbon store according to a global synthesis
Communications Earth & Environment, 2021Co-Authors: Zhenke Zhu, Yalong Liu, Ping Wang, Jingkuan Wang, Kees Jan Van Groenigen, Yuanhe Yang, Kun Cheng, Georg GuggenbergerAbstract:Rice paddies account for ~9% or the world’s cropland area and are characterized by environmental conditions promoting soil organic carbon storage, methane emissions and to a lesser extent nitrous oxide emissions. Here, we synthesize data from 612 sites across 51 countries to estimate global carbon stocks in Paddy Soils and determine the main factors affecting Paddy soil carbon storage. Paddy Soils (0–100 cm) contain 18 Pg carbon worldwide. Paddy soil carbon stocks decrease with increasing mean annual temperature and soil pH, whereas mean annual precipitation and clay content had minor impacts. Meta-analysis shows that Paddy soil carbon stocks can be increased through several management practices. However, greenhouse gas mitigation through Paddy soil carbon storage is generally outweighed by increases in methane and nitrous oxide emissions. Our results emphasize the key role of paddies in the global carbon cycle, and the importance of Paddy management in minimizing anthropogenic greenhouse gas emissions. Rice paddies represent approximately 1.2% of the global soil organic carbon pool and contain 20% more soil organic carbon per hectare than croplands on average, according to a global synthesis.
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carbon input and allocation by rice into Paddy Soils a review
Soil Biology & Biochemistry, 2019Co-Authors: Shoulong Liu, Georg Guggenberger, Zhenke Zhu, Yalong Liu, Yu Luo, Ping Wang, Olga Gavrichkova, Jingkuan WangAbstract:Abstract Knowledge of belowground C input by rice plants and its fate is essential for managing C cycling and sequestration in Paddy Soils. Previous reviews have summarized C input and the pathways of root-derived C in upland Soils by labeling with 14C or 13C (13/14C), while rice rhizodeposition and C input in Paddy Soils have not been comprehensively evaluated. Here, we analyzed the results of 13/14C pulse and continuous labeling studies using 112 datasets from 13 articles on the allocation and pathways of photosynthesized C by rice plants to assess C input, budget, and amount stabilized in Paddy Soils. Overall, 13/14C partitioning estimated by continuous labeling was 72% to the shoots, 17% to the roots, 10% to the soil, and 1.3% was recovered in microbial biomass. Pulse-labeling studies showed a similar C partitioning: 79%, 13%, 5.5%, and 2.1%, respectively. The total belowground C input estimated based on continuous labeling was 1.6 Mg ha−1 after one rice season, of which rhizodeposition accounted for 0.4 Mg C ha−1. Carbon input assessed by pulse labeling was slightly lower (total belowground C input, 1.4 Mg ha−1; rhizodeposition, 0.3 Mg C ha−1; 14 days after labeling). Rice C input after one cropping season was lower than that by upland plants (cereals and grasses, 1.5–2.2 Mg ha−1). In contrast to upland crops, most Paddy systems are located in the subtropics and tropics and have two or three cropping seasons per year. We conclude that (1) pulse labeling underestimates the total belowground C input by 15%, compared with that by continuous labeling, and (2) rhizodeposition of rice accounts for approximately 26% of the total belowground C input, regardless of the labeling method used. Based on allocation ratios, we suggest a simple and practical approach for assessment of the gross C input by rice into the soil, for partitioning among pools and for long-term C stabilization in paddies.
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crop residue management effects on organic matter in Paddy Soils the lignin component
Geoderma, 2008Co-Authors: Andreas Bierke, Klaus Kaiser, Georg GuggenbergerAbstract:Abstract Intensified rice cropping is not only increasing rice yields but also the amount of crop residue. In particular the lignin component of the residues may accumulate in submerged systems such as Paddy Soils due to incomplete decomposition under oxygen-limited conditions. Here, we examined the short and long-term effects of crop residue management on soil organic matter (SOM) in Paddy Soils of two experimental sites in China (Nanjing, Changsha) and one in the Philippines (Los Banos, Laguna). We determined organic C and total N, characterized the composition of alkaline-extractable SOM by 13C NMR spectroscopy, and the lignin component by CuO oxidation. The results revealed no significant changes in organic C, total N and total lignin-derived phenols upon incorporation of crop residue at the recently established experiments at Nanjing and Los Banos. In contrast, all tested variables increased at the long-term experiment at Changsha. Within 16 years (1990 to 2005), the organic C increased by 41% in the ‘residue incorporated’ plots while at the ‘residue removed’ plots the increase was 16%. Similar trends were found for total N. Lignin-derived phenols in ‘residue incorporation’ plots increased about 45% (12% for ‘residue removed’ plots). Parameters addressing alteration of lignin changed at the initial stages of the experiments. These changes are comparable to those observed in aerated cropping systems. No further changes in the lignin composition occurred at later stages of the experiments. The 13C NMR spectra revealed a largely unchanged SOM composition, thus supporting the results of the CuO oxidation. In summary, the additional input of crop residue in Paddy Soils seems to result in the mere accumulation of OM; the larger proportion of lignin-derived phenols reflects the input of crop residue. The comparable degree in oxidative alteration of lignin between ‘residue removed’ and ‘residue incorporated’ treatments indicates that the soil systems can cope with the increased residue-derived lignin input.
Z. B. Zhang - One of the best experts on this subject based on the ideXlab platform.
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macropores generated during shrinkage in two Paddy Soils using x ray micro computed tomography
Geoderma, 2016Co-Authors: Nicolas Bottinelli, Hu Zhou, Z. B. Zhang, P Boivin, Pascal Jouquet, Christian Hartmann, Xinhua PengAbstract:Soil shrinkage curve represents a decrease of total porosity or an increase of bulk density with water loss. However, our knowledge of the dynamics of pores and their geometry during soil shrinkage is scarce, partially due to lack of reliable methods for determining soil pores in relation to change in soil water. This study aimed to investigate the dynamics of macropores (>30 mu m) of Paddy Soils during shrinkage. Two, Paddy Soils, which were sampled from one Paddy field cultivated for 20 years (YPF) and the other one for over 100 years (OPF), represented difference in crack geometry in the field. Macropore parameters (volume, connectivity, and orientation of pores) and soil shrinkage parameters were determined on the same undisturbed soil cores by X-ray microtomography and shrinkage curve, respectively. Macroporosity was on average four times larger in the YPF than in the OPF whereas the shrinkage capacity was lower in the YPF as compared to the OPF (0.09 vs. 0.15 COLE). Soil shrinkage increased the volume of pores by 3.7% in the YPF and by 1.6% in the OPF as well as their connectivity. The formation of macropores occurred mostly in the proportional shrinkage phase. As a result, the slope of the proportional shrinkage phase was smaller in the YPF (0.65) than in the OPF (0.89). New macropores were cracks and extended pre-existing pores in the range of 225-1215 pm size without any preferential orientation. This work provides image evidences that in Paddy Soils with high shrinkage capacity more macropores are generated in the soil presenting a smaller proportional shrinkage slope. (C) 2015 Elsevier B.V. All rights reserved.
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puddling intensity sesquioxides and soil organic carbon impacts on crack patterns of two Paddy Soils
Geoderma, 2016Co-Authors: Z. B. Zhang, H Zhou, Hangsheng Lin, Xinhua PengAbstract:Abstract Paddy Soils subjected to puddling are easily cracked under wetting and drying cycles. This phenomenon has implications for water loss and chemical leaching in Paddy fields. We hypothesized that crack patterns in such Paddy Soils result from aggregate size distribution created by puddling under submerged condition. Soil organic carbon (SOC) and sesquioxides are main binding agents of aggregation while puddling is a disruptive force of aggregates. In this study, our aim was to investigate the effects of puddling intensity, SOC, and sesquioxides on cracking in two Paddy Soils — one cultivated for 20 years (YPF soil) and the other cultivated for over 100 years (OPF soil). The puddling intensity was simulated by ultrasonic dispersion at applied energy of 0–800 J ml− 1. The Soils were treated chemically by water as a control as well as by oxalate, dithionite-citrate-bicarbonate (DCB), or by H2O2. The aggregate size distribution and crack patterns were determined after the simulated puddling and the chemical treatments. The results showed that the simulated puddling and the chemical treatments increased clay- (
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characterizing preferential flow in cracked Paddy Soils using computed tomography and breakthrough curve
Soil & Tillage Research, 2015Co-Authors: Z. B. Zhang, Xinhua Peng, Hu ZhouAbstract:Abstract Soil cracks generated in Paddy fields may change soil structure and provide pathways for preferential flow. However, the quantitative relationship between soil cracks and preferential flow remain unclear in Paddy Soils. The objectives of this study were to (1) reveal the effect of soil cracking on soil structure and preferential flow, (2) find a quantitative relationship between characteristics of soil structure and preferential flow in two Paddy fields. Two Paddy fields, one cultivated for 20 years (YPF) and the other cultivated for more than 100 years (OPF), were subjected to either alternate flooding and drying (AFD) or continuous flooding (CF) (as a control) during rice growing season. Undisturbed soil columns (10 cm in diameter and 20 cm in height) were sampled in the four plots. Macropores (including cracks) were quantified using computed tomography (CT), and preferential flow was assessed by breakthrough curve (BTC). The results showed that the presence of soil cracks under the AFD increased average macropore length but decreased the number of macropores significantly ( P λ and λ eff ) were poor ( P > 0.05). Both the shape of BTCs and fitting parameters demonstrated that soil cracks (5.31–11.9 cm depth) did not increase preferential flow because they did not perforate through the dense plow pan. Soil columns in the CF plots displayed a bit more preferential flow due to a deeper macropore distribution as compared with the AFD plots. While macropore features were different at the two Paddy Soils, the difference in preferential flow was reduced due to the presence of plow pan. This study demonstrates that soil cracks significantly affect macropore structure but their impact on preferential flow may be poor when they do not penetrate through the plow pan.
