ALBERT

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Julius Diel, Uwe Franko〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The dynamics of Soil Organic Matter (SOM) and its relation to the carbon and nitrogen cycle affect many environmental problems (e.g. climate change, food security and water quality). The development of adaptation strategies requires model predictions, but for the necessary large-scale SOM dynamic studies, the quality of the input data is often limiting the reliability of the results.〈/p〉 〈p〉So we performed a uncertainty and sensitivity analysis at different sites of the federal state of Saxony, Germany, and assessed the importance of aggregated agricultural data, namely organic amendments, crop yields, area share of by-product incorporation, area share of conservation tillage and initial soil organic carbon (SOC) concentration (p_oram, p_yield, p_bp, p_cons and p_soc respectively) on the result uncertainty by assuming an uniform error of ±10%. The agricultural data was regionalized from 717 long-term observation fields throughout the study region.〈/p〉 〈p〉We assessed the uncertainties of relative SOC stock change (ΔC〈sub〉rel〈/sub〉) and total nitrogen mineralisation from the organic matter (OM-N〈sub〉min〈/sub〉) and explored the changing sensitivities over the model period (1998–2014).〈/p〉 〈p〉Our results show that p_soc was the most important source of uncertainty for all sites of this study. For ΔC〈sub〉rel〈/sub〉, it is over the whole time constantly the by far most sensitive input parameter, with p_bp being the only factor of agricultural practice with some substantial influence on almost all sites. In the mountainous regions, p_cons ranks equal to p_bp, while for the sandy heathlands, none of them mark a substantial influence besides p_soc.〈/p〉 〈p〉For OM-N〈sub〉min〈/sub〉, p_soc loses its importance over time, being outranked by p_oram in the heathlands after 8 years and in the mountainous regions after 13 years. p_oram furthermore places second for all others but one other region, where p_cons is slightly more important. We therefore see the initial carbon content, the share of by-product removal, and the amount of organic amendments as those factors, where improved data quality would bring the highest effect to reduce the uncertainty in regional SOM modelling.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Weimin Song, Shiping Chen, Yadan Zhou, Guanghui Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate models predict greater rainfall will occur in the arid and semiarid regions of Northwest China, where nitrogen (N) cycling is particularly sensitive to changes in rainfall regimes. Yet, how increasing rainfall regulates soil N transformation processes in these water-limited regions is still not well understood. We conducted a manipulative experiment in a desert ecosystem in Northwest China, whereby we simulated five different scenarios of future rain regimes (natural rains plus 0%, 25%, 50%, 75% and 100% of the local mean annual precipitation) each month from May to September in 2009. We examined 〈em〉in situ〈/em〉 net N mineralization and soil N availability in both vegetated and bare soils, as well as leaf litter N release for the dominant shrub species 〈em〉Nitraria tangutorum〈/em〉 monthly after each rain addition. We found that increased water availability via the simulated rain addition significantly decreased total net N mineralization rates over the growing season in both vegetated and bare soils. A larger amount of litter N was released after rain addition in vegetated soils, which could contribute to the higher concentrations of inorganic N in vegetated soils compared to bare soils. Furthermore, we found that the responses of soil N transformation processes to rain additions showed great seasonality, and thus both rainfall amount and timing jointly regulate the responses of soil N transformation processes to rainfall increase under future rainfall scenarios in this arid desert ecosystem. Over the growing season, rainfall addition reduced soil inorganic N concentrations but favored plant N uptake and microbial N immobilization. We suggest that the cycling of N will be greatly changed under future rainfall regimes, which may have consequences for ecosystem stability and functioning in this “N-conserving” desert ecosystem.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Xiaojie Li, Jinsheng Xie, Qiufang Zhang, Maokui Lyu, Xiaoling Xiong, Xiaofei Liu, Tengchiu Lin, Yusheng Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Subtropical forest soil exerts a large, but uncertain effect on terrestrial carbon (C) cycling. Global warming is anticipated to alter subtropical soil C cycling but currently, there is no consensus on how warming will affect soil C at different elevations. We conducted a short-term laboratory soil warming incubation experiment (ambient temperature +4 °C) along an elevational gradient in Wuyi Mountains of southeastern China to examine the response of soil organic carbon (SOC) mineralization to rising temperatures. Soil samples were collected from three elevations (630 m, 1450 m and 2130 m), and microbial community composition was determined using phospholipid fatty acids (PLFAs). The SOC mineralization increased with rising mean annual temperature (i.e., with decreasing elevation) and with experimental warming. Unlike most other similar experimental studies, we found that the temperature sensitivity (〈em〉Q〈/em〉〈sub〉10〈/sub〉) of SOC mineralization to short-term experimental warming significantly decreased with increasing elevation. We also found that temperature sensitivity of SOC mineralization in response to warming depends on substrate availability, as indicated by the significant relationship between dissolved organic carbon (DOC) and 〈em〉Q〈/em〉〈sub〉10〈/sub〉 values. In addition, soil microbial biomass increased significantly with increasing elevations, but was not significantly affected by short-term experimental warming. Experimental warming reduced the abundance of total PLFAs, bacteria, fungi, and actinomycetes in the low-elevation soil. Experimental warming significantly changed soil microbial community composition at low elevation, with increases in the ratios of cyclopropyl to monoenoic precursor fatty acids (cy:pre), saturated to monounsaturated fatty acids (sat:mono), and isomers to trans-isomers fatty acids (i:a), all of which are stress indicators, indicating that warming treatment increased microbial respiration rather than microbial growth, because the microbial respiration per biomass increases under environmental stress. Microorganisms likely altered their membrane fatty acid components and mass in response to changes in available C. The differences in 〈em〉Q〈/em〉〈sub〉10〈/sub〉 associated with short-term warming and among elevations with long-term temperature differences indicate that the effect of warming on SOC mineralization may change through time and this should be taken into account when predicting SOC mineralization in response to continual rising temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Lanfang Han, Ke Sun, Yan Yang, Xinghui Xia, Fangbai Li, Zhifeng Yang, Baoshan Xing〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Extensive application of biochar to soil exerts a profound effect on organic carbon (OC) in soils. However, the impact of biochar on the content and composition of OC has not been comprehensively summarized. This review provided a detailed examination on the stability of biochar and its effect on the amount, composition and turnover of soil OC, with key limitations and issues recognized. The direct input of labile and stable OC of biochar to soil OC pool, and indirect effects of biochar on soil OC by affecting soil physicochemical and biological properties were discussed. Both low stability of biochar and biochar-induced strong positive priming effect on OC mineralization were commonly observed in sandy soil added with biochar produced from manure at low temperature. The stable OC of biochar was composed of both aromatic OC and the OC fractions stabilized by soil minerals. Biochar mainly increased the formation of macro-aggregates, and this promotion was more intense for clayey soil added with manure-based low temperature-biochar. Additionally, potential influential mechanisms were proposed to explain the effect of biochar addition on amount and composition of humic substances in soils. This review will shed lights on the effect of biochar application on the amount, composition and turnover of native soil OC, and improve the understanding of the ecological effect of biochar on the soil functions.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119321755-ga1.jpg" width="348" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Yuping Zhang, Kai Gu, Jinwen Li, Chaosheng Tang, Zhengtao Shen, Bin Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biochar is a promising material for soil remediation. However, the influence of biochar on soil cracking has not been clearly understood to date. Soil cracking can significantly change the mobility of contaminants in soil and consequently the remediation performance of biochar. This study investigates the effect of a wood biochar on the desiccation shrinkage characteristics of two clayey soils (PKE and XS). The biochar dosages selected are 0%, 0.5%, 2%, 4%, 6%, and 10% (w/w). The results indicate that biochar affects the desiccation cracking characteristics of clayey soils by changing the evaporation process. For PKE, the evaporation rate decreased by 6.56% and 5.59% with 0.5% and 2% biochar addition, respectively, and increased by 2.11% and 17.20% with 4% and 6% biochar addition. Similarly, with the biochar dosage ranges from 0.5% to 10% for XS soil, the evaporation rate decreased by 8.57%, 8.73%, 4.56%, and increased by 0.96% and 41.06%, respectively. Image processing analysis on the cracks indicates that the addition of biochar decreases the quantitative parameters such as the crack ratio, the number of soil mass and the fractal dimension for both treated soils. The crack ratio, the number of cracks and the number of soil mass were reduced by 16.85%, 32.26% and 39.22% for 4% biochar addition in PKE. The value of XS soil with 6% biochar addition decreased by 30.80%, 8.28%, and 11.61%, respectively. Furthermore, biochar can effectively reduce the width of cracks. The role of biochar in the development of desiccation cracking may include (1) occupying the shrinkage space of soil particles; (2) weakening the bonding between soil particles and (3) providing hydrophobic channels. In general, the application of 4% and 6% biochar in PKE and XS respectively has the best performance in inhibiting soil cracking.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Benshuai Yan, Lipeng Sun, Jingjing Li, Caiqun Liang, Furong Wei, Sha Xue, Guoliang Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vegetation succession is one of the most important factors driving changes in microorganisms. It is unclear, however, how the microbial composition and the potential function of C and N cycling change with forest secondary succession. Using soil metagenomic sequencing methods, we studied these changes in bacterial and fungal communities with secondary succession from cropland to a 〈em〉Quercus liaotungensis〈/em〉 forest over approximately 120 years on the Loess Plateau of China. The results revealed the following. (1) Soil microbial biomass C, N, and P increased significantly in topsoil (0–20 cm) with vegetation succession. (2) The abundances of bacteria increased initially and then decreased slightly, whereas an increase in fungal abundances and the ratio of fungi to bacteria was detected along a successional gradient. Microbial communities tended to shift from r- to K-strategists, both at the phylum and genus levels. (3) With vegetation succession, the abundances of C and N cycle-related potential functional genes first significantly increased and then stabilized. Among them, the relative abundances of recalcitrant C degradation-, N fixation-, and ammonification-related genes increased, whereas labile C degradation-, N reduction-, and denitrification-related genes tended to decrease. (4) Redundancy analysis indicated that bacterial communities were influenced by available phosphorus contents and soil C: N ratios, and that fungal communities were mainly affected by ammonium N contents and root biomass. (5) Predicted microbial functional genes were affected by ammonium N and activated C contents. Our study showed that with vegetation succession, microbe communities tended to shift from r- to K-strategists both at the phylum and genus levels, which increased the abundance of organisms expressing C- and N-cycle related genes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Xiaodong Zhang, Zhaoliang Song, Qian Hao, Changxun Yu, Hongyan Liu, Chunmei Chen, Karin Müller, Hailong Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climatic factors including mean annual precipitation (MAP) significantly influence the carbon (C) cycle in terrestrial ecosystems and Earth overall. Phytolith-occluded carbon (PhytOC) is an important C sequestration mechanism and as such plays a vital role in global long-term C sequestration. Understanding the spatial variability in the storage of soil phytoliths and PhytOC and its relationship with climate is critical for evaluating the impact of global climate change on terrestrial ecosystem functions. However, little is known about the responses of soil phytoliths and PhytOC to MAP in grassland ecosystems. This study sampled soil from 24 natural, semi-arid steppe sites along a 2,500 km transect with a precipitation gradient of 243–481 mm yr〈sup〉−1〈/sup〉 in northern China. We investigated the influence of precipitation on the spatial distributions of soil phytoliths and PhytOC storage. Storage of soil phytoliths in bulk soil (0–100 cm depth) ranged from 21.3 ± 0.4 to 88.4 ± 20.3 t ha〈sup〉−1〈/sup〉 along the precipitation gradient. Amounts of soil phytoliths and PhytOC storage were significantly and positively correlated with MAP. Multiple regression analysis revealed that phytolith storage in bulk soil was best predicted by MAP (〈em〉R〈/em〉 = 0.5) and soil organic carbon (SOC, 〈em〉R〈/em〉 = 0.4), with these two variables accounting for about 58% of the total variation observed. Considering the forecasted increase in MAP in the Inner Mongolian steppe due to climate change, and the strong influence of MAP on the annual net primary productivity (ANPP) and related soil PhytOC input from litter decomposition in this region, we expect that ecosystem primary productivity will increase from deserts to meadow steppe and thereby promote soil PhytOC storage. These findings have important implications for understanding the dynamics of soil phytoliths, and predicting the impacts of global climate change on ecosystem functions and management practices in the East Asian steppe ecosystems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): A. Landré, S. Cornu, J.-D. Meunier, A. Guerin, D. Arrouays, M. Caubet, C. Ratié, N.P.A. Saby〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Silicon (Si) is the second most abundant element in the Earth’s crust after O. Its concentration in soils is highly variable from 〈1% to greater than 45%. Parent material is well known to be a major parameter for explaining this variability. In this study, we proposed to analyze the impact of climate and land use on the total Si concentration in soils and to explore the link between total Si and plant available Si (PAS). To do so, we based our analysis on the French soil monitoring network considering the upper soil horizon that was thought to be the most impacted by both the effect of land use and climate and was also the most important horizon in terms of plant availability. In order to extract the impact of climate and land use and for digital mapping purposes, we stratified the database by parent material and soil-types. This stratification was based on the classification used in the 1:100,000 French soil map and 1:100,000 French soil parent material map. For non carbonated soils, we showed that Si concentrations was decreasing with annual rainfall, evidencing a climatic effect on the total Si concentration of French topsoils. No significant effect of the land used could be identified. At last, we showed that PAS (by the CaCl〈sub〉2〈/sub〉 method) is negatively weakly correlated to total Si concentration. This relationship is however variable among soil classes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Craig Smeaton, Natasha L.M. Barlow, William E.N. Austin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S001670611931938X-ga1.jpg" width="294" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Ram Swaroop Meena, Rattan Lal, Gulab Singh Yadav〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil hydrological properties and aggregate stability are strongly impacted by erosion and management practices. However, magnitudes of the erosion-induced changes in topsoil depth and the attendant alterations in soil properties are not well understood. Therefore, the present study was conducted on a long term (20 years) simulated study of topsoil depth and use of soil amendments to monitor changes in soil hydrological properties, and aggregate stability of an Alfisol at the Waterman Farm of The Ohio State University, Columbus, Ohio. The aim of the study was to compare long-term effects of soil amendments (synthetic fertilizer and organic compost) on soil physical and hydrological properties at varying soil depth. The experimental plots, comprising of five treatments, were laid out in Randomized Block Design and replicated thrice. Treatments were: (1) topsoil removed (20 cm deep), (2) undisturbed topsoil (intact topsoil); with two soil amendments: (a) synthetic fertilizer 150 kg nitrogen (N) ha〈sup〉−1〈/sup〉 yr〈sup〉−1〈/sup〉, (b) organic compost at 20 Mg ha〈sup〉−1〈/sup〉 yr〈sup〉−1〈/sup〉, and (3) a permanent grass field (as a benchmark plot). Soil properties, measured for 0–10 cm and 10–20 cm depth, were: texture, aggregate stability, geometric mean diameter (GMD) of aggregates, water retention properties, hydraulic conductivity (〈em〉Ks〈/em〉), pore size distribution, and plant available water capacity (PAWC). Aggregate stability was the highest (87.9 and 84.7%) in the permanent grass at 0–10 cm and 10–20 cm depths, respectively. Among the cultivated treatments, compost- amended undisturbed plots (87.6 and86.9%) had the highest proportion of water stable aggregates (WSA) at 0–10 cm and 10–20 cm depths, respectively. However, the GMD of aggregates was the highest 4.1 mm (0–10 cm) and 3.5 mm (10–20 cm) for the topsoil removed and compost-amended treatment. Soil texture was silty clay loam in topsoil removed treatments, clay loam in the undisturbed treatment, and loam in permanent grass treatment, probably due to artificial removal of topsoil. Plant available water content was more in the disturbed and undisturbed compost-amended plots for both the 0–10 and 10–20 cm depths, respectively. The highest soil water volumetric content ranged from 0.37 to 0.25 m〈sup〉3〈/sup〉 m〈sup〉−3〈/sup〉 in the topsoil removed fertilizer added compared with 0.34 to 0.24 m〈sup〉3〈/sup〉 m〈sup〉−3〈/sup〉 in undisturbed compost added plots, respectively. However, the pore size distribution was not affected by treatments at the 0–10 cm depth. For the10-20 cm depth, an overall greater pore size distribution range of 0.04 to 0.33 m〈sup〉3〈/sup〉 m〈sup〉−3〈/sup〉 was observed in the permanent grass, and undisturbed compost amended treatments. Soil 〈em〉Ks〈/em〉 (cm day〈sup〉−1〈/sup〉) for 0–10 cm depth did not differ significantly across treatments. The data obtained enhances the understanding of the impacts of long-term use of amendments on soil water retention and aggregate stability of simulated topsoil removed and undisturbed field under no-till (NT) in corn (〈em〉Zea mays〈/em〉)–soybean (〈em〉Glycine〈/em〉 max L. Merr.) rotation in the Eastern Corn Belt of the U.S.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Johannes L. Jensen, Per Schjønning, Christopher W. Watts, Bent T. Christensen, Peter B. Obour, Lars J. Munkholm〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The combination of concurrent soil degradation and restoration scenarios in a long-term experiment with contrasting treatments under steady-state conditions, similar soil texture and climate make the Highfield land-use change experiment at Rothamsted Research unique. We used soil from this experiment to quantify rates of change in organic matter (OM) fractions and soil structural stability (SSS) six years after the management changed. Soil degradation included the conversion of grassland to arable and bare fallow management, while soil restoration comprised introduction of grassland in arable and bare fallow soil. Soils were tested for clay dispersibility measured on two macro-aggregate sizes (DispClay 1–2 mm and DispClay 8–16 mm) and clay-SOM disintegration (DI, the ratio between clay particles retrieved without and with SOM removal). The SSS tests were related to soil organic carbon (SOC), permanganate oxidizable C (POXC) and hot water-extractable C (HWC). The decrease in SOC after termination of grassland was greater than the increase in SOC when introducing grassland. In contrast, it was faster to restore degraded soil than to degrade grassland soil with respect to SSS at macro-aggregate scale. The effect of management changes was more pronounced for 8–16 mm than 1–2 mm aggregates indicating a larger sensitivity towards tillage-induced breakdown of binding agents in larger aggregates. At microscale, SSS depended on SOC content regardless of management. Soil management affected macroscale structural stability beyond what is revealed from measuring changes in OM fractions, underlining the need to include both bonding and binding mechanisms in the interpretation of changes in SSS induced by management.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Jielin Ge, Wenting Xu, Qing Liu, Zhiyao Tang, Zongqiang Xie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The soils of shrublands are important for organic carbon storage in terrestrial ecosystems, but geographical patterns and environmental controls of soil organic carbon (SOC) remain largely understudied compared to other terrestrial ecosystems, leaving a significant gap in our understanding of terrestrial ecosystem carbon budgets. Here, we quantified SOC density (SOCD) and its potential determinants based on a comprehensive dataset with a consistent stratified random sampling of extensive soil profiles down to the parent material or to one meter depth across 1211 sites across China. Our up-to-date estimate of SOCD in Chinese shrublands is an average of 8.36 kg m〈sup〉−2〈/sup〉, and ca. 43% of SOC is stored in the upper 20 cm relative to the one meter top soil, which is higher than estimates for shrublands globally. We also observed that SOCD was positively related to shrubland biomass and more so with belowground biomass. Furthermore, SOCD was positively related to mean annual precipitation (MAP), soil total nitrogen (N), phosphorus (P), clay and silt percent, but decreased with increasing mean annual temperature (MAT). Dark felty soils stored the highest SOCD and frigid desert soils stored the lowest. Soil total nitrogen (N), MAP, soil type, MAT, and belowground biomass, soil clay, and pH were the best predictors of total SOCD in Chinese shrublands. We concluded that Chinese shrubland soils store the lowest density of organic carbon so far recorded compared to forests and grasslands, and that the vertical distribution of SOC in Chinese shrublands was much shallower. While both climate (in particular MAP) and soil total N exerted dominant control over geographical patterns of SOCD across Chinese shrublands, soil type also played a significant role. Our study also emphasizes this key role of edaphic variables in determining the SOCD of shrublands and that they should be better incorporated into large-scale assessments of SOC dynamics. Our study extends existing work conducted in forest and grasslands and provides the most up-to-date knowledge on benchmark values for SOCD in Chinese shrublands, with important implications for predicting the fate of C stored in shrubland soils in response to climate change.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Kangying Guo, Yingzhi Zhao, Yang Liu, Junhui Chen, Qifeng Wu, Yifei Ruan, Songhao Li, Jiang Shi, Lin Zhao, Xuan Sun, Chenfei Liang, Qiufang Xu, Hua Qin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A microcosm study was performed to investigate changes in soil enzyme activities and microbial C- and N-use efficiencies (CUE and NUE) with amendment of biochars prepared at three pyrolysis temperatures (350, 500 and 700 °C) in an acid bamboo (〈em〉Phyllostachys praecox〈/em〉) forest soil. The results showed that, compared to the non-amended control, biochars produced at 500 and 700 °C significantly (〈em〉P〈/em〉 〈 0.05) increased soil pH, total N, and dissolved N (DN) concentrations, whereas significantly decreased dissolved organic C (DOC) and exchangeable acidity concentrations after three months. The microbial biomass C (MBC) and N (MBN) and the ratio of fungi: bacteria (F:B) were only significantly increased under 350 °C biochar. The ratios of both soil C:N and DOC:DN to MBC:MBN were reduced under 500 and 700 °C biochars, suggesting a lower C:N imbalance between resources and microorganism. The ratio of C- to N-acquiring enzyme activities increased gradually under biochars with increasing temperature. Moreover, microbial CUE increased whereas NUE declined under biochars at 500 and 700 °C, and the threshold elemental ratio (TER) revealed that the microbial nutrient metabolisms were limited by N in soils amended with residue, but were limited by C under biochars at 500 and 700 °C. Structural equation modeling indicated that the C:N imbalance had a great impact on microbial CUE, while changes in F:B ratio and soil pH were closely associated with NUE. This study suggests that changes in microbial nutrient-use efficiency and ecoenzymatic stoichiometry reveals a clear C-limitation, but a N-availability under short-term amendment of biochar produced at a high pyrolysis temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Yi Peng, Yannik E. Roell, Anders Bjørn Møller, Kabindra Adhikari, Amélie Beucher, Mette B. Greve, Mogens H. Greve〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spatial assessment of terroir is creating a new possibility for enhancement of high quality agro-food product and to minimize negative environmental effects such as soil degradation and associated risks. The classification and mapping of particular terroir units could be a competitive marketing tool with a major impact on farmers’ incomes. For this purpose, Carré and McBratney (2005) proposed the terron concept to establish combined soil and landscape entities as the first investigative step to identify terroirs. The main objective of the present work was to assemble various environmental factors (i.e. soil, terrain and climate), to identify and then to map terrons in Denmark. First, for representing soil factors, a national soil spectral library was utilized to measure taxonomic distances between 34 Danish reference soil profiles and the Danish national soil profile database (586 soil profiles). Second, the terrain and climate factors for each soil profile location were then compiled as represented by relative slope position, valley depth, valley bottom flatness, vertical distance to the channel network, number of frost days, annual number of growing days, global solar radiation, and precipitation. Third, nine Danish terron classes were established by fuzzy c-means clustering based on an integrated matrix including all soil, terrain and climate factors whereby each terron class is characterized by soil, terrain and climate as a whole entity. Finally, the spatial distribution of Danish terrons was mapped using Cubist regression rules. The results were compared with a soil map derived from the same profile database. We concluded that the map of terrons described natural environment quantitatively and formally in terms of soil, landscape and climatic information better than just a soil class or soil attribute map. Further investigations are needed to discover whether the terron classes give better predictions of landscape-dynamic processes and allow better management options than soil alone. This study also demonstrated several advantages of using soil spectral data and ancillary data to identify and map terrons. The next step will be to validate the terron map by incorporating crop yield data and social factors to delineate natural Danish terroir units.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Konrad Metzger, Chaosheng Zhang, Mark Ward, Karen Daly〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lime is a crucial soil conditioner to bring agricultural soils to optimum pH values for nutrient availability. Lime recommendations are typically determined in laboratory extractions, the most common being the “Shoemaker-McLean and Pratt” (SMP) buffer method, that requires carcinogenic reagents soon to be abolished under the EU legislation. As an alternative to wet chemistry, mid-infrared (MIR) spectroscopy has shown to be a cost-and time effective method at predicting soil properties. The capability and feasibility of diffuse reflectance infrared spectroscopy (DRIFTS) to predict lime requirement (LR) in tillage fields is examined. Samples from 41 cereal tillage fields (n = 655) are used to build a calibration for DRIFTS using partial least squares regression (PLSR). The samples were split into calibration set (31 fields, n = 495) and validation set (10 fields, n = 160). After pre-processing with trim, smoothing and standard normal variate, a calibration model using 6 latent variables, provided R〈sup〉2〈/sup〉 of 0.89 and root mean square error of cross-validation (RMSECV) of 1.56 t/ha. Prediction of all fields from the validation set resulted in R〈sup〉2〈/sup〉 of 0.76 and root mean square error of prediction (RMSEP) of 1.68 t/ha. The predictions of the single fields ranged from R〈sup〉2〈/sup〉 values of 0.41 to 0.72, RMSEP of 0.48 to 4.2 t/ha and ratios of performance to inter-quartile distance (RPIQ) of 0.45 to 3.56. It was shown that the signals of soil constituents having an influence on the LR were picked up in the spectra and were identified in the loading weights of the PLSR. While the error is too high to predict the variability of LR within the field, MIR prediction using field averages provided a viable alternative to current laboratory methods for blanket spreading of lime on tillage fields.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Selma Beatriz Pena, Maria Manuela Abreu, Manuela Raposo Magalhães, Nuno Cortez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The soil erosion by water is a land degradation process identified the Land Degradation Neutrality (LDN) conceptual framework and a soil threat recognized in the Soil Thematic Strategy. It is also a very significant problem in the Mediterranean area. The common cause of land degradation is incorrect land use and management practices, which enhance the importance of planning the future of the landscape. When solving a soil erosion problem, not only land degradation is being reversed, but soil safety is provided: water conservation, biodiversity improvement, ecosystem services provision and better landscape equilibrium.〈/p〉 〈p〉The Land Degradation Neutrality (LDN) target, referred in the United Nations Sustainable Development Goals for 2030, is defined as a state whereby the amount and quality of land resources necessary to support ecosystem functions and services and enhance food security remain stable or increase within specified temporal and spatial scales and ecosystems. Despite some initiatives and recent projects about the achievement of LDN target, the link to landscape planning tools is still lacking.〈/p〉 〈p〉The approach followed in this study incorporates the centric and holistic perspective of soil, and aims to contribute to a definition of a mapping methodology of the areas that should be submitted to land degradation neutrality plans providing ecosystem restoration planning and the co-benefits of restoring soil functions. This goal will be supported by the assessment of the soil conservation 〈em〉status〈/em〉 at a national scale (Portugal), using an integrated approach between soil maintenance/improvement and soil degradation, with the current soil cover protection. The evaluation of soil cover protection was established with the interpretation of land use classes and its cover-management factor (C-factor) from the Universal Soil Loss Equation and was tested in three different scenarios: (S1) the higher C-values collected in the research studies (S2) the more recent C-value collected in the research studies and (S3) an adapted scenario with assumptions considered by the authors.〈/p〉 〈p〉The study applied to mainland Portugal showed that Scenario S3 was more equilibrated regarding the distribution of the results (conservation 〈em〉vs〈/em〉. restoration) but was dependent of a set of defined assumptions especially regarding the different forest trees characteristics and management practices performed in Portugal. In this scenario, it was identified that 45.6% of Portugal needs LDN planning towards ecosystem restoration. The proposed methodology also identifies different priority classes of intervention, where the public or private investments could be targeted. Those LDN planning areas are easily framed in the responses to achieve LDN: avoid, reduce or reverse.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Ahmed Abed Gatea Al-Shammary, Abbas Kouzani, Yeboah Gyasi-Agyei, Will Gates, Jesús Rodrigo-Comino〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solarisation technology allows for improving soil quality as well as crop productivity. The influence of the properties and method of use of plastic materials used to cover soils, such as the number and thickness of layers, and colour of the material, significantly alters soil thermal-physical properties. These effects can be managed and modified to increase solarisation efficiency by achieving a decrease in vapour movement between the soil surface and the atmosphere. Also, soil solarisation establishes microclimates that increase the effectiveness of fertilisers, thus modifying the soil thermal-physical properties. However, there is a lack of complete and general overview of this widely used technology. This paper presents a comprehensive review of soil solarisation technology and describes the impacts it has on soil thermal-physical properties when combined with different soil treatments. It is well-known that the efficiency of solarisation technology increases with temperature. However, we describe that the heat transfer effectivity depends on several different soil thermal-physical properties such as the soil thermal flux, conductivity, diffusivity, soil volumetric heat capacity, and soil temperature. Other soil physical properties such as soil texture, soil bulk density, soil porosity, and soil volumetric moisture content have contributions to make. Moreover, there are several external factors which significantly modify the effectiveness of heat transfer under different solarisation conditions, particularly the weather conditions, the type of tillage management, properties of plastics used and moisture content. We conclude that more research needs to be done: (i) to quantify the degree to which soil thermal-physical properties affect soil solarisation technology, and (ii) to assess the impact of soil technology on crop productivity and quality.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Yunqi Zhang, Yi Long, Xinbao Zhang, Zengli Pei, Xue Lu, Zhehong Wu, Mingyang Xu, Haiquan Yang, Peng Cheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Assessment of long-term human impact on sediment yields from karst settings can improve our understanding of the pattern of soil erosion causing rocky desertification in the historical context of environmental change influenced by human activity. Few previous investigations have estimated this impact over time-scales longer than 50 years. This study used dated depression deposits to reconstruct human impact on sediment yields from a small karst catchment in the Three Gorges Reservoir Region, China, over the past 600 years. 〈sup〉137〈/sup〉Cs, 〈sup〉210〈/sup〉Pb〈sub〉ex〈/sub〉, and 〈sup〉14〈/sup〉C techniques were used to determine short-term (~50 yr), medium-term (~100 yr), and long-term (~600 yr) sedimentation in the karst depression, respectively. Sedimentation rates and specific sediment yields in the catchment during six distinct stages (1351–1462, 1463–1701, 1702–1809, 1810–1916, 1917–1962, and 1963–2017) were determined from core samples. The results indicate that soil loss during the period 1351–1962 was more intensive than that since 1963, which reveals changing sediment yields impacted by human activity over the past 600 years. The high values during the three stages before 1810 can be attributed to the impacts of large-scale migration of people from Huguang to Sichuan during the Ming and Qing dynasties; the higher values during 1810–1916 might reflect increasing disturbance related to rapid population expansion; the highest values (1917–1962) were caused by large-scale deforestation in 1958 and a consistently increasing population; and low values since 1963 reflect constraints on the supply of sediment source materials. These results suggest that rocky desertification might be a long-term land-surface process induced by human activity over timescales of 〉100 years rather than a short-term modern process occurring over a number of decades. This is the first attempt to examine the long-term history of human impact on sediment yields from a karst catchment using depression deposits. This work improves our understanding of the influence of human activities on soil loss at a depression-catchment scale, and of the evolution and dynamics of rocky desertification in karst areas.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Carme Estruch, Petr Macek, Cristina Armas, Nuria Pistón, Francisco I. Pugnaire〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil respiration accounts for ca. three quarters of total ecosystem respiration and is sensitive to temperature and moisture. Plants can influence soil CO〈sub〉2〈/sub〉 emissions through specific effects on soil humidity, soil temperature and soil microbial communities. These plant-soil effects mostly come via litter production and root exudates, enhancing soil autotrophic and heterotrophic respiration. We explored how plant species affected soil CO〈sub〉2〈/sub〉 emissions in an arid environment. We altered soil temperature in bare soil and under the canopy of four plant species differing in functional type, and measured monthly fluxes to establish seasonal patterns of CO〈sub〉2〈/sub〉 release along a 20-month period. We found that soil temperature explained 69% of the annual soil respiration (SR) variance, while soil water content explained 71% of SR variance. When we included plant species identity in the model, soil temperature and soil water content explained 76% and 81% of SR variance, respectively, exemplifying how plant species modulate SR responses as a function of temperature and water availability. Our results demonstrate that plant species influence soil carbon balance and emphasize that species identity matters in dry ecosystems. SR dynamics in dry ecosystems can be accurately modelled with soil water and temperature as predictors, but models are more efficient if plant species identity is considered.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): M. Redmile-Gordon, A.S. Gregory, R.P. White, C.W. Watts〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉While soil microbial ecology, soil organic carbon (SOC) and soil physical quality are widely understood to be interrelated — the underlying drivers of emergent properties, from land management to biochemistry, are hotly debated. Biological binding agents, microbial exudates, or ‘extracellular polymeric substances’ (EPS) in soil are now receiving increased attention due to several of the existing methodological challenges having been overcome. We applied a recently developed approach to quantify soil EPS, as extracellular protein and extracellular polysaccharide, on the well-characterised soils of the Highfield Experiment, Rothamsted Research, UK. Our aim was to investigate the links between agricultural land use, SOC, transient binding agents known as EPS, and their impacts on soil physical quality (given by mean weight diameter of water stable aggregates; MWD). We compared the legacy effects from long-term previous land-uses (unfertilised grassland, fertilised arable, and fallow) which were established 〉 50 years prior to investigation, crossed with the same current land-uses established for a duration of only 2.5 years prior to sampling. Continuously fallow and grassland soils represented the poorest and greatest states of structural integrity, respectively. Total SOC and N were found to be affected by both previous and current land-uses, while extractable EPS and MWD were driven primarily by the current land-use. Land-use change between these two extremes (fallow → grass; grass → fallow) resulted in smaller SOC differences (64% increase or 37% loss) compared to MWD (125% increase or 78% loss). SOC concentration correlated well to MWD (adjusted 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.72) but the greater SOC content from previous grassland was not found to contribute directly to the current stability (p 〈 0.05). Our work thus supports the view that certain distinct components of SOC, rather than the total pool, have disproportionately important effects on a soil’s structural stability. EPS-protein was more closely related to aggregate stability than EPS-polysaccharide (〈em〉p〈/em〉 values of 0.002 and 0.027, respectively), and ranking soils with the 5 greatest concentrations of EPS-protein to their corresponding orders of stability (MWD) resulted in a perfect match. We confirmed that both EPS-protein and EPS-polysaccharide were transient fractions: supporting the founding models for aggregate formation. We suggest that management of transient binding agents such as EPS —as opposed to simply increasing the total SOC content— may be a more feasible strategy to improve soil structural integrity and help achieve environmental objectives.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Alan Carlos Batistão, Dörthe Holthusen, José Miguel Reichert, Luís Antônio Coutrim dos Santos, Milton César Costa Campos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Archaeological Dark Earths (ADE) are anthropogenic soils with high fertility and excellent physical conditions due to high soil organic carbon (SOC) content. However, climate change, land use and soil management can increase SOC mineralization, resulting in microstructure damage of these soils. To verify the effect of SOC loss, we collected deformed samples from the surface horizon and simulated the reduction of C with the application of 0.2, 0.4 and 0.6 ml of hydrogen peroxide 35% per gram of soil, resulting in three treatments of different oxidation levels and untreated soil. Both original and oxidized soil were submitted to an amplitude sweep test with controlled strain and a thixotropy test, in a compact modular rheometer. To characterize the effect of soil properties on rheology and resilience of ADEs, we performed a correlation analysis with physico-chemical properties from untreated soil. Higher clay and organic matter contents increased the microstructure elasticity of ADEs. The increase in base saturation, mainly due to the high Ca〈sup〉+2〈/sup〉 content, also favors elasticity. The soil’s resilience is a result of the joint effect of particle size distribution, base saturation and SOC content. The microstructure recovers fast, regardless of the disturbance intensity. The SOC loss affected the microstructure differently in each ADE. These differences are not dependent on the amount of SOC lost and mostly labile SOC (as removed by low oxidation intensity) was responsible for soil strength.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Yong-Sheng Wu, Xin-Rong Li, Hasi-Eerdun, Rui-Ping Yin, Tie-Jun Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Surface roughness plays an important regulatory role in the interactions and feedback between the soil surface and atmospheric systems. However, information regarding the response of surface roughness to trampling disturbances caused by sheep grazing is limited, especially in sandy soils covered by biocrust. This study investigated the covariations in the roughness, coverage and shear strength of cyanobacterial crust (CC), algae-lichen mixed crust (LC) and moss crust (MC) on both the semi-fixed and fixed dunes at the southern edge of the Mu Us Sandy Land, northern China, under various trampling intensities using field studies and mimicked sheep trampling disturbances. The results showed that the surface roughness of semi-fixed and fixed dunes decreased after an initial increase with increasing trampling intensity, and the surface roughness of the fixed dunes was higher than that of the semi-fixed dunes. In addition, with the increasing trampling intensity, the maximum surface roughness (〈em〉R〈/em〉〈sub〉max〈/sub〉) and its corresponding trampling intensity of the biocrust-covered soils at different development stages followed the order of CC, LC, and MC. The grazing intensity (〈em〉G〈/em〉) corresponding to 〈em〉R〈/em〉〈sub〉max〈/sub〉 values in both the semi-fixed and fixed dunes at different development stages of biocrust was 9.6 to 14.4 and 11.1 to 14.4 animal unit day/ha, respectively. The biocrust coverage and shear strength decreased exponentially with increasing trampling intensity and significantly affected the sensitivity of surface roughness to changes in trampling strength. Moderate grazing (grazing intensity less than 〈em〉G〈/em〉) was beneficial for increasing the surface roughness of biocrust-covered sandy land. Increased surface roughness has positive and negative impacts on the ecological and hydrological functions of biocrust-covered soil. To minimize the negative effects of moderate grazing on surface soil, the dune fixation degree, biocrust development level, trampling time and interannual precipitation variability should be considered. This study highlighted the role of grazing management in enhancing the surface roughness and associated ecosystem functions of semiarid regions similar to the Mu Us Sandy Land.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Changhua Fan, Pengpeng Duan, Xi Zhang, Haojie Shen, Miao Chen, Zhengqin Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The mechanisms associated with N〈sub〉2〈/sub〉O and NO processes following biochar application remain unclear in an Anthrosol under intensively vegetable production. An incubation experiment with 〈sup〉15〈/sup〉N tracing technique and quantitative polymerase chain reaction (qPCR) was performed to investigate the responses of pathways and the microbial mechanisms of N〈sub〉2〈/sub〉O and NO production to the application of wheat biochar (Bw) and swine manure biochar (Bm) field aged for one year in an Anthrosol under 60% water holding capacity. The application of both types of biochar decreased the cumulative N〈sub〉2〈/sub〉O emissions by 12.9–20.0%, with an obvious mitigation effect observed after Bw application. The reduction in N〈sub〉2〈/sub〉O emissions derived from autotrophic nitrification and denitrification induced by biochar were coupled with a decrease in ammonia-oxidizing bacteria (AOB) 〈em〉amoA〈/em〉 abundance and the ratio of 〈em〉(nirK〈/em〉 + 〈em〉nirS〈/em〉)/〈em〉nosZ〈/em〉, respectively. Biochar increased the relative contribution of heterotrophic nitrification by 54.2–58.3%, with stronger stimulating effects from the Bm amendment than from the Bw amendment. Moreover, cumulative NO emissions were strongly reduced by an average of 35.5% by biochar, with no differences between Bw and Bm. Furthermore, covariation in NO flux and NO〈sub〉2〈/sub〉〈sup〉−〈/sup〉–N content, together with the alternations in the abundance of AOB 〈em〉amoA〈/em〉, indicated that nitrifier denitrification might play a vital role in NO emissions. The present study highlights biochar’s promising effects on mitigating N〈sub〉2〈/sub〉O and NO emissions by weakening autotrophic nitrification and denitrification processes. Meantime, heterotrophic nitrification should be taken into consideration when comprehensively assessing the mitigation potential of biochar.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119323845-ga1.jpg" width="425" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Aleš Vaněk, Andreas Voegelin, Martin Mihaljevič, Vojtěch Ettler, Jakub Trubač, Petr Drahota, Maria Vaňková, Vendula Oborná, Kateřina Vejvodová, Vít Penížek, Lenka Pavlů, Ondřej Drábek, Petra Vokurková, Tereza Zádorová, Ondřej Holubík〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soils on the Erzmatt (Switzerland) formed on hydrothermally mineralized dolomite rock and are naturally Tl-rich. In this study, we investigated if variations in the stable Tl isotope ratios in soil samples from different profiles can be linked to data on the extractability and speciation of soil Tl and whether the isotopic data allow drawing conclusions on the geochemical processes that affected Tl over the course of soil formation. In two soil profiles, we observed a marked accumulation of the heavy 〈sup〉205〈/sup〉Tl isotope in the B horizons, with ε〈sup〉205〈/sup〉Tl values that were up to 7 higher than in the underlying bedrock. This 〈sup〉205〈/sup〉Tl enrichment, however, was neither reflected in the speciation of Tl nor its chemical fractionation. Furthermore, exchangeable soil Tl in the B horizons was found to be much isotopically lighter than the bulk soil Tl. These findings suggest that the observed isotopic shift may be linked to cyclic Tl mobilization and immobilization processes over the period of rock weathering and soil formation. Oxidative Tl uptake by Mn-oxides associated with a 〈sup〉205〈/sup〉Tl enrichment, continuous weathering of the Tl(III)-containing phases, followed by a Tl(I) remobilization (leading to enrichment in 〈sup〉205〈/sup〉Tl) are suggested to be responsible for the binding of the heavy Tl isotope fraction into other phases, mainly illite (a dominant Tl host), which is not normally expected. Hence, our results show that the Tl isotopic fractionation data measured in a dynamic multi-phase (soil) system can potentially serve as a proxy for tracing redox-controlled processes, but their use for phase or the sorption process identification is much more complicated.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119327387-ga1.jpg" width="272" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Songchao Chen, Dominique Arrouays〈/p〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): S.S. Paul, N.C. Coops, M.S. Johnson, M. Krzic, A. Chandna, S.M. Smukler〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate change is presenting sizeable challenges for agricultural production around the world. In some regions, shifting precipitation patterns in the spring and fall are negatively impacting farm operation by reducing the number of “workable days” or the days fields can be worked with heavy equipment without damaging soil structure. This can be particularly problematic for farms on clay soils and/or poor drainage. Approximating a water content threshold at which a soil is not workable due to soil structure destruction can be helpful for planning effective farm operations. In this study, we applied advanced remote sensing and machine learning tools to produce digital maps of soil organic carbon (SOC) and clay (CL) content and used them in existing pedotransfer functions (PTFs) to predict a workability threshold (WT) across a study area in Delta, British Columbia, Canada. We combined field data, soil and vegetation indices derived from multiple Landsat satellite images, topographic indices, and soil survey information to digitally map SOC and CL of the agricultural lands in Delta using random forest (RF) and generalized boosted regression model (GBM). When validated against an independent field dataset, the RF model outperformed GBM for all accuracy measures (coefficient of determination – R〈sup〉2〈/sup〉, concordance correlation coefficient – CCC, and normalized root mean square error – nRMSE). We then spatially applied several PTFs using our digital maps to estimate the plasticity limits of the soil and produce WT map. The WT map was then tested against independent field samples of the soil water content at −10 kPa and we achieved R〈sup〉2〈/sup〉 of 0.59, CCC of 0.70, and nRMSE of 0.15. Our analysis showed that 40% of the fields in the study area had WT 〈 30%, a threshold that is already being impacted by reduced workable days. This WT map could be used to improve spatial prioritizations of investments for climate change adaptation at farm to regional scales.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): María Blanca Pascual, Miguel A. Sánchez-Monedero, Francisco J. Chacón, María Sánchez-García, María L. Cayuela〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aerobic soils are the largest biotic sink for atmospheric methane (CH〈sub〉4〈/sub〉). Although agricultural intensification is known to adversely impact soil CH〈sub〉4〈/sub〉 uptake, the application of organic amendments (e.g. composts, green residues) in agricultural soils has been found to stimulate the activity of CH〈sub〉4〈/sub〉 oxidizers. However, little is known about the influence of biochar (a carbonaceous by-product of biomass pyrolysis) on the soil CH〈sub〉4〈/sub〉 sink function. This study analyzes, through a series of laboratory incubation assays, how ten well-characterized biochars with contrasting properties influence CH〈sub〉4〈/sub〉 oxidation rate constants (k) in an aerobic high-pH agricultural soil. Through the use of 〈sup〉13〈/sup〉C-CH〈sub〉4〈/sub〉, we demonstrated that both CH〈sub〉4〈/sub〉 soil oxidation and CH〈sub〉4〈/sub〉 assimilation were responsible for the decrease in CH〈sub〉4〈/sub〉 concentration. A principal component regression (PCR) of the results suggested that the physico chemical properties of biochars were directly linked to their ability to enhance or inhibit the oxidation of CH〈sub〉4〈/sub〉. Biochars from wood feedstocks and pyrolysed at 600 °C, characterized by a high pore area, led to the highest CH〈sub〉4〈/sub〉 oxidation rates whereas biochars with high ash concentrations and electrical conductivity significantly diminished CH〈sub〉4〈/sub〉 oxidation rates. Biochar redox properties were not found to be relevant for CH〈sub〉4〈/sub〉 oxidation in soil.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Elham Farahani, Hojat Emami, Amir Fotovat, Reza Khorassani, Thomas Keller〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of K:Na ratio on plant available water (PAW), least limiting water range (LLWR), integral water capacity (IWC), penetration resistance and plant growth was assessed in this study. Treatment solutions including different K:Na ratios at two electrical conductivity levels (EC = 3 and 6 dS m〈sup〉−1〈/sup〉) were applied into an agricultural loamy soil in pots using capillary rise from the bottom, and the soil in the pots were kept at a water content close to field capacity for one month. In addition, maize was planted into the treated soils in three replicates. PAW, LLWR and IWC were calculated by soil available water calculator (SAWCal) software based on measurements of soil water retention and penetration resistance. In our study, LLWR was limited by PAW. The results showed that PAW of the treated soils increased significantly with increasing K:Na ratio in comparison with the control soil at both EC levels, due to increasing clay dispersion with increasing K:Na ratio. A reduction in the soil pore size due to migration of dispersed clay particles into soil pores could be a possible reason for the increase in PAW. Positive relations were found between PAW and meso-porosity and micro-porosity at both EC. Maize growth significantly increased with increasing PAW at EC = 6 dS m〈sup〉−1〈/sup〉. It can be concluded that the application of different K:Na ratios induced different degrees of dispersion of clay particles, which presumably migrated into soil pores, changing the soil pore size distribution towards smaller pores. This increased PAW in our studied soil, with positive effects on plant growth.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Michelle L. Haddix, Edward G. Gregorich, Bobbi L. Helgason, Henry Janzen, Benjamin H. Ellert, M. Francesca Cotrufo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding the mechanisms controlling the formation and persistence of soil organic matter (SOM) is important for managing soil health and sustainable food production. The formation of SOM and the degree to which it is protected from decomposition are important for determining the long-term persistence of SOM. We used soils collected in a 〈sup〉13〈/sup〉C-labelled litter decomposition study established at agricultural sites in Canada to understand the formation and persistence of newly-formed SOM. The ten agricultural sites spanned a wide range of soil carbon contents, texture, and climatic conditions. We fractionated the soil to isolate water extractable organic matter (WEOM), free light POM (fPOM), sand-sized and occluded particulate organic matter (oPOM), and silt and clay sized particles, referred to as mineral-associated organic matter (MAOM). Quantitative isotope tracing was used to determine the litter-derived C in all fractions. We performed these analyses early (six months after incubation) and later (five years after incubation) in the decomposition process to evaluate factors that control the formation and persistence of POM and MAOM. After six months litter-derived C was found in all fractions, but after five years it had declined in all fractions except the MAOM. Formation of MAOM was related to high mean annual precipitation and low sand content, whereas occluded POM formation was related to high soil C content. Persistence of MAOM and POM during the incubation were associated with low soil temperature and high soil C content. There was no consistent indication that formation of MAOM occurred from the decomposition of POM, suggesting that MAOM and POM are formed by two separate pathways. This has important implications for SOC models, which assume that plant-derived C passes through a sequence of pools, becoming more stable along the way.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Joshua Steckley〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Anecic earthworms such as 〈em〉Lumbricus terrestris〈/em〉 are ecosystem engineers whose impacts on soil fertility and remediation have been extensively researched. The majority of 〈em〉L. terrestris〈/em〉 used for such research and practical remediation applications are procured through the largely unknown bait worm market that serves freshwater recreational fishermen across North America and Europe. Some earthworm researchers have questioned the use of these bait worms for research and soil inoculations because of their untraceable origins, unknown environmental exposures and growing conditions, as well as the sustainability of harvesting practices. However, there has been no recent study of this unique industry and how it hand-picks hundreds of millions of 〈em〉L. terrestris〈/em〉 worms annually from a single region in southwestern Ontario. This paper provides a detailed description of how land and labour are currently organized to supply the world market for the valuable 〈em〉L. terrestris〈/em〉, commonly known as the “Canadian Nightcrawler” bait worm. Based on 59 semi-structured depth interviews, the findings show there are an estimated 500 to 700 million worms picked annually from farmer fields that stretch between Toronto and Windsor, Ontario. Dairy farms in particular have emerged as 〈em〉de facto L. terrestris〈/em〉 production sites because of their perennial alfalfa crops, heavy manure application, and reduced tillage practices. This has made 〈em〉L. terrestris〈/em〉 the most lucrative crop in the region with many farmers leasing land to worm-picking operations for over $1000 CND per year ($750 USD/ €685) — approximately four times the regional rental rates. Worm-pickers have historically been recent immigrants to Ontario with the majority of current pickers coming from Vietnam. Worm pickers make $20CND ($15 USD, €13.50) per thousand worms, and can pick over 20,000 worms per night in optimal field conditions (moisture, temperature, wind, moonlight). The piece-rate wages tend to reward speed and efficacy with some pickers capable of making over $600 in a single night. This peculiar arrangement between dairy farmers, soils, and worm pickers opens avenues for socio-economical, agronomical and ecological studies of commercial 〈em〉L. terrestris〈/em〉 harvesting.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Mansonia Pulido-Moncada, Sheela Katuwal, Lidong Ren, Wim Cornelis, Lars Munkholm〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Subsoil compaction is a major threat to soil quality. The use of bio-subsoilers has been proposed as a mitigation practice. There is, however, a paucity of knowledge on the effects of potential bio-subsoiling crops in alleviating severely compacted subsoil. X-ray Computed Tomography (CT) was used to assess the changes caused by different crops in the pore network of a severely compacted subsoil. The potential bio-subsoilers, chicory, lucerne, radish and tall fescue, with spring barley as reference, were grown for one year in undisturbed soil columns (Ø = 0.20 m, h = 0.50 m) with soil originating from a heavily compacted soil after mechanical impact. Soil columns were X-ray CT-scanned before and after the experiment. CT-pore soil characteristics were quantified by image analysis. Crop treatments affected the soil porosity differently on the studied soil. Radish and tall fescue did not show a significant impact on CT-derived pore characteristics at any depth. In the compacted layer, the macropore density, the branches number, and the number of pores (for volume sizes of 〈 100 mm〈sup〉3〈/sup〉 and diameter ≤ 1.5 mm) were larger for chicory and lucerne compared to barley (P 〈 0.05). Chicory and Lucerne appear to contribute to the development of a large number of complex-shaped pores. Differences in the CT-derived pore network indicate that chicory and lucerne are likely to perform better than the other crops when used as bio-subsoilers by creating a larger, more connected and complex pore network. Longer-term growth is needed to obtain a marked loosening effect in the compacted layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): M.G. Veloso, D.A. Angers, M.H. Chantigny, C. Bayer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉No-tillage (NT) and legume cover crops generally improve the quality of tropical and subtropical soils, but the mechanisms underlying these effects are not well known. We performed a study to investigate the influence of NT and legume cover cropping on microbial cell-wall constituents [glucosamine (GlcN), taken as indicator of fungal cell-wall; muramic acid (MurN), taken as indicator of bacterial cell-wall], and on their relationships with soil aggregation and soil organic carbon (SOC) accumulation in different fractions (light fraction, and sand-, silt- and clay-sized fractions) of a subtropical Acrisol in Southern Brazil. The GlcN concentration ranged from 450.5 mg kg〈sup〉−1〈/sup〉 in the 0–5 cm soil layer to 20.5 in the 75–100 cm soil layer, approximately 10 times greater than MurN concentrations (53.1–2.7 mg kg〈sup〉−1〈/sup〉 for the same soil layers). No-tillage and legume cover crops favoured the accumulation of fungal and bacterial cell-wall constituents in whole soil, especially in the top 5 cm, with a preferential enrichment in GlcN. Legume cover cropping and NT resulted in greater accumulation of C in the light fraction in surface soil, which favoured the fungal community that, in turn, mediated an improvement in soil aggregation. Fungal-derived glucosamine also preferentially accumulated down to 100 cm depth, and more specifically in the clay-sized fraction of soil, suggesting a specific role of fungi in SOC accumulation at depth. Overall, our study provides field-based evidence that the accrual of fungal cell-wall constituents under NT and legume cover cropping is a key process leading to aggregation and SOC accumulation in subtropical soil profiles.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119320336-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Haofeng Lv, Yiming Zhao, Yafang Wang, Li Wan, Jingguo Wang, Klaus Butterbach-Bahl, Shan Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Conventional flooding irrigation combined with over-fertilization in intensively used solar greenhouse vegetable production systems are jeopardizing soil productivity and groundwater quality due to soil acidification and nitrogen (N) leaching. While it has been shown that excessive application of N fertilizer in greenhouse production systems significantly reduces topsoil pH values, it remains unknown if also subsoil pH values do change too and if surplus N fertilization and hydrological N losses lead to nutrient imbalances. In this study, soil samples from six soil layers from 0 to 300 cm were taken from 45 greenhouse fields with three representative cultivation years (2, 5, and 10 years). Soil samples from 5 adjacent corn fields served as comparison. Results show that (1) compared to soils from adjacent corn fields, the pH in the 0–30 cm soil layer was slightly elevated two years and five years after greenhouse establishment, but was lowered by 0.52 ± 0.06 units after ten years. Moreover, also the pH in deeper soil layers (30–300 cm) significantly decreased with cultivation years. (2) A significant imbalance of N:P:K ratios in greenhouse top soils was found, as P and K accumulates while N is leached to subsoils. (3) Structural equation modeling indicated that changes in the mineral N concentration in the 0–30 cm soil layer was driving soil pH changes. Our results demonstrate that N accumulation in top soils and N leaching to deep soil caused by excessive irrigation explains observed declines in surface and deep soil pH values of conventional greenhouse vegetable production systems. Consequently, for avoiding groundwater contamination with N and for ensuring sustainable soil productivity, current schemes of irrigation and fertilization management need to be adapted to avoid N leaching, soil acidification, nutrient accumulation and imbalances.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Xu Zhang, Jisong Qu, Hong Li, Shikai La, Yongqiang Tian, Lihong Gao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Crop land degradation is a common phenomenon in most regions of the world, especially in arid and semi-arid regions. To mitigate cropland degradation and further enhance crop productivity, it is crucial to restore soil quality by utilizing efficient soil management practices. Although biochar has been widely used to improve soil conditions, the efficiency of biochar in enhancing crop productivity is often limited by inappropriate agricultural practices (e.g. irrigation and fertilization). Moreover, little information is available regarding the link among availability of water, biochar and productivity. In this study, we measured the effects of biochar addition, daily fertigation and their combination on overall soil quality, crop yield and water-fertilizer productivity in alkaline soils of a semi-arid region, over two years. To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties were measured and integrated into a soil quality index (SQI). The treatments evaluated were (i) untreated soils managed with traditional irrigation and fertilization (control), (ii) soils treated with biochar and managed with traditional irrigation and fertilization (B), (iii) untreated soils managed with daily fertigation (DF), and (iv) soils treated with biochar and managed with daily fertigation (B + DF). In general, biochar addition enhanced soil quality (expressed by SQI) mainly through increasing soil water content (SWC), available phosphorus (AP), the capacity of soil microbes to utilize miscellaneous (CSM-MI) and microbial biomass carbon (Cmic), and decreasing soil pH and plant-parasitic nematode abundance. Daily fertigation improved soil quality primarily by enhancing SWC, AP, CSM-MI and Cmic. The SQI exhibited strong positive correlations with both plant biomass and fruit yield. In addition, the treatment B + DF showed not only the highest SQI and fruit yield, but also the highest irrigation water-productivity (326.3 and 557.9 kg mm〈sup〉−1〈/sup〉 in 2017 and 2018, respectively) and partial factor productivity for fertilizer in both years 2017 and 2018. Our results show that biochar addition combined with daily fertigation can improve overall soil quality, and further enhance cucumber yield and water-fertilizer productivity in alkaline soils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Ning Liu, Cai Shao, Hai Sun, Zhengbo Liu, Yiming Guan, Lianju Wu, Linlin Zhang, Xiaoxi Pan, Zhenghai Zhang, Yayu Zhang, Bing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Continuous cropping of American ginseng (〈em〉Panax quinquefolius〈/em〉 L.) is often associated with the scarcity or unavailability of soil nutrients and an imbalance of rhizosphere microbiota, resulting in low yield and poor plant quality. Inoculation with arbuscular mycorrhizal fungi (AMF) improves plant growth and production by facilitating nutrient acquisition and by modifying the abundance and diversity of rhizosphere microorganisms. In the present study, we investigated the mechanisms by which continuous cropping of American ginseng caused growth inhibition and how AMF biofertilizer application relieved these cropping obstacles. The results showed that: 1) continuous cropping of American ginseng significantly decreased the emergence rate, shoot and root dry weight, rhizosphere soil pH, the contents of ammonium, available phosphorus (P), and available potassium (K) in the rhizosphere, while increasing the root rot disease index and the soil content of nitrate; 2) continuous cropping of American ginseng decreased the diversity of bacteria, while increasing the diversity of fungi, and increased the relative abundances of Acidobacteria and Ascomycota, while decreasing the relative abundances of Actinobacteria, Firmicutes and Zygomycota; 3) in contrast, the application of AMF biofertilizer relieved the negative effects of continuous cropping American ginseng; 4) significant positive correlations were found between 〈em〉Pseudarthrobacter〈/em〉, 〈em〉Streptomyces〈/em〉 and the content of ammonium, between 〈em〉Bacillus〈/em〉 and the content of available K, and between 〈em〉Mortierella elongata〈/em〉 and the content of available P, suggesting that the increase of rhizosphere plant-beneficial bacteria and fungi promoted the contents of available nutrients in the rhizosphere; 5) application of AMF biofertilizer significantly decreased the abundances of soil-borne pathogenic fungi 〈em〉Fusarium oxysporum〈/em〉, 〈em〉F. solani〈/em〉 and the deleterious bacteria 〈em〉Candidatus Solibacter〈/em〉. In summary, our results suggest that AMF biofertilizer application improved the continuous cropping of American ginseng growth by increasing the AMF inoculation rate, by recruiting rhizosphere beneficial bacteria and fungi that promote plant-uptake of nitrogen (N) and P, and by suppressing soil-borne pathogens. Therefore, AMF biofertilizer is a probiotic agent that prevents microbial imbalances and nutrient deficiencies during continuous cropping of American ginseng.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Mengxue Wan, Wenyou Hu, Mingkai Qu, Weidong Li, Chuanrong Zhang, Junfeng Kang, Yongsheng Hong, Yong Chen, Biao Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil cation exchange capacity (CEC) is a critical property of soil fertility. Conventionally, it is measured using laboratory chemical methods, which involve complex sample preparation and are time-consuming and expensive. Previous studies have investigated nondestructive and rapid methods for determining soil CEC using proximal soil sensors individually, including portable X-ray fluorescence (PXRF) spectrometry and visible near-infrared reflectance (Vis-NIR) spectroscopy. In this study, we examined the potential of the fusing data from PXRF and Vis-NIR to predict soil CEC for 572 soil samples from Yunnan Province, China. The CEC of the samples ranged from 5.42 to 50.25 cmol kg〈sup〉−1〈/sup〉. Both partial least-squares regression (PLSR) and support vector machine regression (SVMR) were applied to predict soil CEC with individual sensor datasets and a fused sensor dataset for comparison. The root mean squared error (RMSE), coefficients of determination (R〈sup〉2〈/sup〉), and ratios of performance to interquartile range (RPIQ) were used to evaluate the performance of the models. Results showed that: (1) SVMR performed better than PLSR on single sensor datasets and the fused sensor dataset, in terms of RMSE, R〈sup〉2〈/sup〉, and RPIQ; and (2) both PLSR and SVMR based on the fused sensor dataset had better predictive power (RMSE = 4.02, R〈sup〉2〈/sup〉 = 0.72, and RPIQ = 2.23 in PLSR model; RMSE = 3.02, R〈sup〉2〈/sup〉 = 0.82, and RPIQ = 2.31 in SVMR model) than those based on any single sensor dataset. In summary, the fused sensor data and SVMR showed great potential for estimating soil CEC efficiently.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Min-oh Park, Moon-Hyun Kim, Yongseok Hong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Equilibrium vapor-phase Hg concentrations and vaporization kinetics at temperatures from 100 to 400 °C were evaluated in field soil naturally contaminated with Hg〈sup〉0〈/sup〉, as well as sand artificially contaminated with HgCl〈sub〉2〈/sub〉, HgO, and HgS. The calculated change in the standard enthalpy of Hg vaporization (ΔH〈sup〉0〈/sup〉) was 4.73 (±1.52), 2.11 (±0.17), 5.59 (±0.25), and 4.87 (±0.46) kcal mol〈sup〉−1〈/sup〉 for naturally Hg〈sup〉0〈/sup〉-contaminated field soil and sand artificially contaminated with HgCl〈sub〉2〈/sub〉, HgO, and HgS, respectively. The measured ΔH〈sup〉0〈/sup〉 was 30% of the theoretical ΔH〈sup〉0〈/sup〉, which suggests that higher temperatures are required to remove Hg from contaminated soil when compared to pure chemical states. Thermal vaporization and desorption kinetics tended to increase upon increasing the temperature; however, the rates at 300 and 400 °C were similar to each other due to kinetic limitations. Our theoretical calculations showed that 90% Hg removal from field contaminated soil at 100, 300, and 400 °C would require 204 days, 3.5 h, and 2.7 h, respectively. At low temperature (i.e., approximately 100 °C), an unrealistically long time was required for Hg removal from soil; however, increasing the temperature up to 400 °C did not necessarily decrease the remediation time. Thus, optimal remediation temperature needs to be evaluated based on Hg thermal desorption and volatilization kinetics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Andrew Cudzo Amenuvor, Guowei Li, Jiantao Wu, Yuzhou Hou, Wei Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a new method for determining the shrinkage curve. In this method, a 10 mm high, 80 mm diameter cylindrical dish with smooth interior is filled completely with soil slurry and placed on an electronic balance and then subjected to drying. Images of the soil surface are taken periodically from a fixed location, from which the surface area of the shrinking soil mass is determined by converting the images to binary images. The decreasing bulk volume of the soil is determined from the surface area and the varying thickness of the soil, which is determined from the known initial and measured final thickness (measured with calipers) and assuming that the change in specimen thickness is proportional to the change in its radius at any stage of drying. This method compares favorably with results of the balloon method using the same slurry sample material. Data from this method also fits very well to an existing shrinkage curve equation. This method is effortless, less time consuming than existing methods, and data acquisition can be automated. In addition, the shrinkage curve can be obtained in a relatively short period of 48 h as compared to existing methods that take days or even weeks. The limitation of measuring the shrinkage curve on soil slurry as presented in this work is that it does not represent the structural shrinkage zone.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Daniel Moraetis, Sumaya Salim Al Kindi, Sara Kalifah Al Saadi, Ahmed Abdul Raoof Ali Al Shaibani, Kosmas Pavlopoulos, Andreas Scharf, Frank Mattern, Michael J. Harrower, Bernhard Pracejus〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the Sultanate of Oman remnants of deteriorating terrace agricultural systems offer important insights into long-term human adaptation in the arid tropics. Irrigation and terrace agriculture in the mountainous Jabal Akhdar region reveal historic agricultural practices in a rugged, high elevation context. The present study examines soil quality and regolith provenance in abandoned agricultural soil terraces. Three soil profiles in each of the Villages of Hadash and Wijma were excavated and analyzed. Physical, chemical and mineralogical analyses were conducted for all soil horizons. In addition, six other soils, 3 possible soil parent rocks (regolith) and soil’s bedrock were collected. Soil ages were constrained by 〈sup〉14〈/sup〉C assays and stable isotope, (〈sup〉13〈/sup〉C and 〈sup〉18〈/sup〉O) on the bulk carbonates in the calcrete (caliche). The results demonstrate that both sites display poor soil quality with very low average total organic carbon (TOC) (6.2–5.0 g kg〈sup〉−1〈/sup〉) and mean weight diameter (MWD; 0.27–0.48 mm), with low water stable aggregate content (〈42%). All the geochemical, mineralogical and the thin section analyses show that the soils exhibit unique characteristics that differ from those of other sediments (possible parent regolith) and soils in the vicinity. The finding of ostracod shells in the soil terraces in both areas and 〈sup〉14〈/sup〉C dating of calcrete (10.193 ± 30–13.887 ± 40 a BP) indicate that regolith was human-transported to terraces to create soil. The 〈sup〉14〈/sup〉C ages of the bulk carbonates match well with a dry period of high calcite precipitation contemporaneous to the Younger Dryas. The Hadash and Wijma soil terraces are located ~45 km away from each other, but still display significant similarities in terms of regolith provenance and soil development and were likely filled with regolith from the same source. These results offer new perspective on agricultural terrace development and oasis agriculture in a rugged, high-elevation, arid environment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Zeyong Gao, Zhanju Lin, Fujun Niu, Jing Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The mechanisms of hydrological processes, biochemical cycles, and permafrost revolution, and the potential impacts of climate change on these, are still poorly quantified in alpine regions, partly due to a lack of understanding of soil water dynamics in the permafrost active layer. In this study, soil water in the active layer was monitored 〈em〉in-situ〈/em〉 at nine sites, including wet meadow (WM), alpine meadow (AM), alpine steppe (AS), transitional area-steppe (TA-S), transitional area-meadow (TA-M), bare land (BL), extremely degraded wet meadow (EDWM), alpine steppe on south-facing slope (ASSF), and alpine meadow on north-facing slope (AMNF) regions. These sites are located in the hinterland of the Qinghai–Tibet Plateau (QTP). Ground-ice distributions and isotope variations under different alpine ecosystems were also examined. The results demonstrate that soil water content was low at 0.5-m depth and high at the surface and at 1.0-m depth in the soil profiles from the TA-S, BL, EDWM, ASSF, and AMNF sites. However, denser vegetation coverage masked the effects of the freeze–thaw processes, which leading soil water content increased gradually with soil depth. Moreover, rainfall infiltration for recharging soil water in the lower layers was hampered due to the buffering action of mattic epipedons and the existence of clayed layers. Additionally, preferential flow often occurred in the degraded alpine meadows, which supplied deeper soil water. The Pearson correlation coefficients between soil water in the deeper layers and ground-ice were above 0.67 (significance 〈0.05), suggesting that deep soil water had a stronger effect on the formation of ground-ice near the permafrost table than soil water at the surface and middle root layers. Furthermore, results from the analysis of isotopic tracers suggest that precipitation directly recharged more ground-ice near permafrost table at the EDWM, ASSF, and AWNF sites, but less so at the WM, AM, AS, and BL sites, due to greater evapotranspiration and land cover. These results provide insights into the effect future climate warming can have on ecological succession and regional hydrological processes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Shucheng Li, Junhu Xu, Shiming Tang, Qiuwen Zhan, Qinghai Gao, Lantian Ren, Qingqin Shao, Lei Chen, Junli Du, Bing Hao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The conversion of grassland to agricultural land is an important land use change that affects soil stocks and concentrations of C, N and P, as well as their stoichiometric ratios. However, the response mechanism of soil C, N and P change to grassland conversion remains unclear. Here, we conducted a 〈em〉meta〈/em〉-analysis of 92 studies and showed that the C and N stocks mainly depended on soil depth, conversion duration and precipitation, while the P response was insensitive to these factors. Moreover, C, N and P losses were also correlated with soil physical–chemical properties (pH, sand, silt, clay). Changes in the response ratios of C:N, C:P and N:P indicated that soil C and N were more sensitive than P to grassland conversion. These results suggest that land use management policies should protect natural grasslands, especially in the arid and semi-arid regions, to minimize soil C, N and P loss.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Wuxia Bi, Baisha Weng, Denghua Yan, Mengke Wang, Hao Wang, Jinjie Wang, Huiling Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phosphorus (P) is well known as a vital nutrient required for plant growth and a critical factor often causing eutrophication in water bodies. However, few studies have focused on the effects of drought-flood abrupt alternation (DFAA), a new type of extreme climate event, on the transformation of P in farmland systems. In this study, we, therefore, focused on DFAA effects on available P (AP) in topsoil, soluble P (SP) and total P (TP) in surface runoff, as well as plant P contents and P uptake in summer maize farmland systems. Field control experiments (sheltered under a ventilated shed with an artificial rainfall device) were conducted to simulate two levels of DFAA (i.e., light drought-light flood and moderate drought-light flood) during parts of two summer maize growing seasons (i.e., seeding-jointing stage and tasseling-grain filling stage). Results showed that DFAA increased AP concentration in topsoil, which was probably induced by the accumulation of the phyla Proteobacteria and Actinobacteria under moderate drought and by an increase in phosphate-solubilizing bacteria (PSB), especially the genera 〈em〉Bacillus〈/em〉 and 〈em〉Bradyrhizobium〈/em〉. In addition, broken soil aggregates and increasing soil porosity caused by DFAA could also cause an increase of AP in topsoil. Soluble P and TP in surface runoff showed a decreasing trend with moderate drought in DFAA. The higher AP increased the root P uptake, while P in stems and leaves could be transported to fruits under DFAA with moderate drought. The results could provide some references for the study of the effects and adaptation-strategies related to extreme climate events and their effects on P in farmland systems.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119326187-ga1.jpg" width="285" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Jan Willem van Groenigen, Cristine Morgan, Ingrid Kögel-Knabner, Budiman Minasny, Jaap de Gruijter, Johan Bouma〈/p〉

Description: 〈p〉Publication date: 1 June 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 368〈/p〉 〈p〉Author(s): Wencan Zhang, Weida Gao, Tusheng Ren, W. Richard Whalley〈/p〉

Description: 〈p〉Publication date: 1 June 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 368〈/p〉 〈p〉Author(s): Scott M. Devine, Anthony T. O'Geen, Han Liu, Yufang Jin, Helen E. Dahlke, Royce E. Larsen, Randy A. Dahlgren〈/p〉

Description: 〈p〉Publication date: 1 June 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 368〈/p〉 〈p〉Author(s): Casper du Plessis, George van Zijl, Johan Van Tol, Alen Manyevere〈/p〉

Description: 〈p〉Publication date: 15 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 367〈/p〉 〈p〉Author(s): Luiz Eduardo Zancanaro de Oliveira, Rafael de Souza Nunes, Djalma Martinhão Gomes de Sousa, Cícero Célio de Figueiredo〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Jordon Wade, Gabriel Maltais-Landry, Dawn E. Lucas, Giulia Bongiorno, Timothy M. Bowles, Francisco J. Calderón, Steve W. Culman, Rachel Daughtridge, Jessica G. Ernakovich, Steven J. Fonte, Dinh Giang, Bethany L. Herman, Lindsey Guan, Julie D. Jastrow, Bryan H.H. Loh, Courtland Kelly, Meredith E. Mann, Roser Matamala, Elizabeth A. Miernicki, Brandon Peterson〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Yi Zhang, Shenyan Dai, Xinqi Huang, Ying Zhao, Jun Zhao, Yi Cheng, Zucong Cai, Jinbo Zhang〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Hong Gao, Xinyue Zhang, Liangjie Wang, Xianglin He, Feixue Shen, Lin Yang〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Jinquan Li, Ming Nie, Elise Pendall〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Marie Spohn, Isabell Zeißig, Emanuel Brucker, Meike Widdig, Ulrike Lacher, Felipe Aburto〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Xiaobing Zhou, Ye Tao, Benfeng Yin, Colin Tucker, Yuanming Zhang〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Xinmu Zhang, Jingheng Guo, Rolf David Vogt, Jan Mulder, Yajing Wang, Cheng Qian, Jingguo Wang, Xiaoshan Zhang〈/p〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Minjie Hu, Josep Peñuelas, Jordi Sardans, Chuan Tong, Chang Tang Chang, Wenzhi Cao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Estuarine tidal marshes play a key role in phosphorus (P) retention and cycling; however, they are suffering from small but significant increases in tidal saltwater intrusion. The likely impacts of these low-level saltwater intrusions on P availability and microbial activity are unclear. Here, we investigated soil P speciation, alkaline phosphatase (ALP) activity, and the 〈em〉phoD〈/em〉 phosphatase gene community along a freshwater-oligohaline gradient in the Min River estuary, southeast China. The results indicated that with the transition from freshwater to oligohaline water, the levels of soil-water salinity, pH and sulfate content were greater, and ALP activity was lower, which were associated with higher concentrations of organic P, available P, aluminum-bound P, calcium-bound P, and occluded P and lower levels of iron-bound P. There was a strong shift in the 〈em〉phoD〈/em〉 phosphatase community composition in response to the freshwater-oligohaline gradient. Our findings showed that with the transition from freshwater to an oligohaline environment, in addition to the associated increases in salinity and soil pH and decreases in general microbial and biological activity and soil organic carbon, there is a shift in soil P toward more recalcitrant and immediately available fractions with less labile forms.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Ziqiang Liu, Dengfeng Li, Jiaen Zhang, Muhammad Saleem, Yan Zhang, Rui Ma, Yanan He, Jiayue Yang, Huimin Xiang, Hui Wei〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): J. Koestel, M. Larsbo, N. Jarvis〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Songchao Chen, Vera Leatitia Mulder, Gerard B.M. Heuvelink, Laura Poggio, Manon Caubet, Mercedes Román Dobarco, Christian Walter, Dominique Arrouays〈/p〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Xiang Wang, Erik L.H. Cammeraat, Karsten Kalbitz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil erosion strongly influences the transport and fate of carbon (C) and nitrogen (N) in hillslope soils. However, in dynamic landscapes, erosional effects on soil N cycling and primary controls on N bioavailability are not well understood: particularly with respect to differences between topsoil and subsoil. Here we aim to explore the influence of erosion on (i) spatial distributions of soil N fractions and (ii) controls on N bioavailability in eroding vs. depositional sites within the Belgian Loess Belt. Soil samples were fractionated by aggregate size and density. In addition, intact soil samples were incubated to determine the influence of oxygen status (0, 5, and 20%) and labile organic matter on mineralization and nitrification of N in the context of erosion. The results showed that the deposition of eroded upslope soil materials led to N enrichment throughout entire soil profiles. Across both eroding and depositional sites, more than 93% of the total N was associated with minerals. Increased macro-aggregate- and mineral-associated N at the depositional site indicated that aggregation and N stabilized by minerals contribute to N enrichment in the depositional soils. Inorganic N, mostly NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N, was also larger at the depositional site. Oxygen concentrations were positively related to net N nitrification and mineralization rates regardless of geomorphic position. Glucose addition significantly reduced net N mineralization and nitrification rates. In conclusion, our results indicate that soil erosion might not only lead to spatial variations of N pools but also potentially affect the transformation and bioavailability of N along eroding hillslopes. Future research should consider the fate of different N species in eroding landscapes and consequences for both carbon sequestration and N leaching.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Deyvid Diego Carvalho Maranhão, Marcos Gervasio Pereira, Leonardo Santos Collier, Lúcia Helena Cunha dos Anjos, Antonio Carlos Azevedo, Rafael de Souza Cavassani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Karst terrains in tropical regions are object of few studies on soil properties and pedogenesis. In this study, soils pedogenesis was evaluated in a karst environment in the Cerrado biome, northern region of Brazil. The assumption is that even in the Cerrado conditions the characteristics of the soils are similar to other limestone soils in arid and semi-arid climates. Six soil profiles along a toposequence were sampled in trenches located at the summit (P1), shoulder (P2), backslope (P3), footslope (P4) and toeslope (P5 and P6) positions. The profiles were described, and their morphological (macromorphology and micromorphology), physical, chemical, mineralogical and organic matter attributes analyzed. The soils were classified as Calcic Luvisol (P1), Calcaric Eutric Cambisol (P2), Haplic Kastanozem (P3), Calcic Pellic Vertisol (P4), Orthofluvic Gleyic Calcaric Eutric Fluvisol (P5), Orthofluvic Calcaric Eutric Fluvisol (P6). Melanization and calcification are the main pedogenic processes, and they are controlled by the nature of parent material and the landscape position of the soil profile. The profiles P1, P2 and P3, at footslope and toeslope, show higher values of weathering ratios, which indicates the presence of clay minerals with a higher SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ratio. They also have the highest amounts of CaCO〈sub〉3〈/sub〉 which are associated with precipitation and neoformation of calcite. Although soils in the Cerrado biome are mostly highly weathered and with low natural fertility, the soils in the study area show accumulation of carbonates, high levels of exchangeable calcium and magnesium, pH values and base saturation that are associated with specific pedo-environments. The combination of the soil forming factors parent material and karst terrain controlled the dynamics of carbonates, leading to their accumulation in soils, regardless of the regional climatic conditions of the Cerrado biome.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119315447-ga1.jpg" width="440" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Yongsheng Hong, Long Guo, Songchao Chen, Marc Linderman, Abdul M. Mouazen, Lei Yu, Yiyun Chen, Yaolin Liu, Yanfang Liu, Hang Cheng, Yi Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Estimating soil organic carbon (SOC) in topsoil can help improve soil quality and food production. This study aimed to explore the potential of airborne hyperspectral image to estimate the SOC of bare topsoil at an agricultural site located in the southeast part of Iowa State, United States. To magnify the subtle spectral signals concerning SOC, and accelerate calibration and improve predictive ability, we developed a framework to combine two advanced spectral algorithms, namely, fractional-order derivative (FOD) and optimal band combination algorithm for SOC predicting. Our case was based on 49 soil samples and a scattered airborne hyperspectral image. Random forest (RF) was utilized to establish SOC estimation models by incorporating the optimal spectral indices processed by different FOD transformations on the basis of the optimal band combination algorithm. Results indicated that when the fractional order increased, overlapping peaks and baseline drifts were gradually removed. However, the magnitude of spectral strength decreased concurrently. More detailed and abundant spectral variability was captured by FOD as compared with those by original reflectance and first and second derivatives. The estimation accuracies developed from the optimal band combination algorithm (cross-validation 〈em〉R〈/em〉〈sup〉2〈/sup〉, 0.36–0.66) were generally better than those from full-spectrum data (cross-validation 〈em〉R〈/em〉〈sup〉2〈/sup〉, 0.32–0.54). The RF model based on the combination of 0.75-order reflectance and optimal band combination algorithm obtained the highest estimation accuracy for SOC with cross-validation 〈em〉R〈/em〉〈sup〉2〈/sup〉 of 0.66. This research provides guidance for future studies in selecting the most appropriate FOD transformation to preprocess spectral data and in using the optimal band combination algorithm to determine the spectral index. Airborne hyperspectral image-based modeling can be further used to map agricultural topsoil SOC to support local-scale agricultural planning.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Zohre Ebrahimi Khusfi, Mohammad Khosroshahi, Fatemeh Roustaei, Maryam Mirakbari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Atmospheric conditions and physical characteristics of the earth surface have an important effect on the spatiotemporal variations of sand-dust events. The main objective of the present study was to investigate the effect of these variables on the seasonal variation of these events in semi-arid regions of Central Iran Zone (CIZ). The Ridge Regression (RR) method was used to analyze the relationship between seasonal variations of precipitation, surface winds speed, air temperature, and Enhanced Vegetation Index (EVI) with Dust Storm Index (DSI) for two different periods (2001–2008 and 2009–2016). The dusty winds direction around the study area was also determined using the dust roses. The results showed that the annual DSI changes in the study area had a week incremental trend with a rate of 0.07/8 yrs in the previous period while it followed a strong increasing trend with a rate of 0.22/8 yrs in the latter period. It was also found that the activity of sand-dust storms in the second period was greater than the first period, especially in the border region of Iran and Turkmenistan. According to RR analysis, DSI had a significant positive association with the surface winds speed in the summer (β = +0.48; p-value 〈 0.05) and the winter precipitation (β = −0.3; p-value 〈 0.05) over the previous period. During this period, there was no significant relationship between the temperature and EVI with DSI in other seasons (p-value 〉 0.05). In the second period, the surface winds speed was positively correlated with the DSI in the spring (β = +2.04), summer (β = +2.6) and autumn (β = +2.08). The significant negative relationship between EVI and DSI changes was observed only in the spring season (β = −0.7; p-value 〈 0.05). Our findings also indicated that dusty winds direction in the northeast, northwest, and southeast parts of the study area were from the northwest, southeast, and west, respectively. These findings can help to mitigate the negative consequences of dust emissions and improve the wind erosion management in semi-dry lands of CIZ.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Zong Wang, Wenjiao Shi, Wei Zhou, Xiaoyan Li, Tianxiang Yue〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Digital soil mapping approaches relating to the soil particle size fractions (psf) face the challenge around how to establish the statistical or geostatistical models from large sets of environmental variables, especially in a situation with sparse soil profile data. Recently, many machine learning (ML) models have sprung up with advantages over statistical models. However, few studies focused on the comprehensive comparative analyses between ML and geostatistical models in the soil psf mapping. And the exploration of optimal combination of data transformation and model simulation was even less. Therefore, two transformed methods such as additive log-ratio (ALR) and isometric log-ratio (ILR) transformations combine with two ML models such as boosted regression tree (BRT), random forest (RF) and a classic geostatistical model of regression kriging (RK) were implemented to map soil psf in the Heihe River basin, China. A total of 640 samples and thirteen scorpan factors were collected and used for the comprehensive comparative analysis. Results showed that the scorpan factors such as temperature, precipitation, elevation, soil type, soil organic carbon, vegetation types and normalized difference vegetation index had important impacts on the soil psf mapping. ILR transformation was better than ALR transformation with advantage of improving stability of data distributions and ML models could also improve the mapping performance in comparison with RK models for better handling candidate factors. For these ML models, the RF models had better accuracy performance than the BRT models. In contrast, ILR transformation combined with RF model (ILR_RF) had the best performance, with the lowest root mean square error values (sand, 15.35%; silt, 14.20%; and clay, 6.66%), Aitchison distance value (0.86), standardized residual sum of squares value (0.60), and the highest concordance correlation coefficient value (0.73) and coefficient of determination value (56.69%) for clay content. In addition, ILR_RF had a relatively higher right ratio of soil texture type (68.44%) and better predict performance for most soil texture types. The predicted maps generated from ILR_RF presented more reasonable and smoother transitions. In the future, more ML models should be explored and more variables related to soil psf should be introduced into the models to improve the predictive performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Jiwei Li, Zhouping Shangguan, Lei Deng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Secondary succession has a major influence on vegetation and soil biogeochemical processes, however, the dynamics of microbial metabolic activity and the driving factors during grassland succession after farmland abandonment remain unclear. Therefore, we examined variations in microbial biomass carbon (Cmic), soil basal respiration (BR), microbial quotient (Cmic:Corg), and metabolic quotient (qCO〈sub〉2〈/sub〉) in sloping farmlands that had been abandoned for 0, 3, 8, 13, 18, 23 and 30 years on the Loess Plateau in China. Moreover, the plant, soil and microbial properties were determined to reveal the forces driving soil microbial metabolic activity. The results showed that compared to those of farmland, the Cmic significantly increased by 104.7% and 168.0%, while the qCO〈sub〉2〈/sub〉 significantly decreased by 54.3% and 70.5%, respectively, in the late succession stages (23 and 30 years). Long-term succession (30 years) significantly enhanced the Cmic:Corg by 51.4%. In contrast, except for a decrease at 8 years, the BR changed little during grassland succession following farmland abandonment. These changes in microbial metabolic activity indicators were associated with shifts in litter biomass, soil organic carbon, available nitrogen, and soil fungi. Litter biomass and fungi were strongly affected the changes in microbial metabolic activity. This study provided new information regarding the dynamics of microbial metabolic activity during long-term secondary succession and enhanced our understanding of the linkages among plant, soil and microorganisms in semiarid ecosystems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Xingwei Ren, Ning Hong, Linfei Li, Jianyu Kang, Jiejie Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rainstorms and floods in cities has increased largely in recent years because of both extreme climate events and city imperviousness increasing. It’s generally acknowledged that water infiltration change of soils in urban green space area has an impact on urban waterlogging problems, but the degree of the impact as well as how it affects is still not fully clear. In response, this paper theoretically explored the mechanism and extent of the effect of infiltration change on urban stormwater runoff. On the base of the storm water management model (SWMM) and the Horton model, the effect of changes in initial infiltration rates and stable infiltration rates of urban soils are discussed at different levels under three cases. The results show that the change impact is closely related to rainfall intensity and urban imperviousness. Compared to changing the initial infiltration rates of soil, changing the stable infiltration rates or the overall infiltration can mitigate urban flooding more effectively. Under low rainfall intensity and urban impermeability, there exists a critical value of the stable infiltration rate. The critical value is not a constant, but increases with rainfall intensity and urban impermeability increasing. The rainfall intensity and urban impermeability play an important role in the soil infiltration change affecting urban runoff process. Overall, this paper presents new insight to understand the effect of water infiltration change on urban flooding and waterlogging problems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Jie Wang, Xiangtao Wang, Guobin Liu, Guoliang Wang, Yang Wu, Chao Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of restoration on plant communities and soil nutrients have been extensively studied but knowledge of the metabolic requirements of microbial communities is limited, especially in fragile alpine meadow ecosystems. Here, vegetation and soil from four meadows (grazed meadow, fenced meadow, fenced + reseeded meadow, and undegraded meadow) on the Tibetan Plateau were investigated. The nutrient requirements of microbes represented by stoichiometry of extracellular enzyme activities related to soil C, N, and P acquisition (β-1,4-glucosidase, BG; β-1,4-N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP; and alkaline phosphatase, AP) and their possible environmental drivers were determined. Our results showed that enzymatic C:N:P acquisition in all the meadows deviated from 1:1:1, suggesting that soil enzymatic activity stoichiometry in Tibetan alpine meadows is not homeostatic. Microbial communities in grazed meadows were co-limited by soil N and P levels, and this limitation was closely associated with the stoichiometry of soil nutrients. Activities of BG, NAG + LAP, AP, and their stoichiometry (C:N, C:P, and N:P) in fenced meadows were 38.2%, 32.9%, 51.2%, 16.8%, 19.5% and 2.3% higher than those in grazed meadows. These results indicate that fencing can relieve the N and P limitations for microbial communities in alpine meadows. Seeding the fenced meadow did not increase the soil nutrient content, microbial biomass, or enzyme activity compared with the fenced meadow, possibly owing to the low competition of the seeded species for resources. Changes in extracellular enzyme activity and stoichiometry were better explained by dissolved organic C and microbial biomass N than by plant or other soil properties. Our results demonstrate the effectiveness of fencing on the restoration of degraded alpine meadows from the perspective of alleviating microbial nutrient limitations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 363〈/p〉 〈p〉Author(s): Xing Wu, Fangfang Wang, Ting Li, Bojie Fu, Yihe Lv, Guohua Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Freeze-thaw cycles (FTCs) and increasing nitrogen (N) availability may affect soil carbon (C) and N turnover and thus stimulate greenhouse gas (GHG) emissions in cold regions. However, the combined effects of FTCs and increased N availability on GHG fluxes remain unexplored, especially in high-altitude alpine meadows. We conducted an incubation study to investigate the effects of different forms and levels of N additions on soil trace gas fluxes during three FTCs in an alpine meadow on the Qinghai-Tibetan Plateau. Our results showed that the N〈sub〉2〈/sub〉O and CO〈sub〉2〈/sub〉 emissions as well as CH〈sub〉4〈/sub〉 uptake substantially increased during FTCs. N additions generally enhanced the freeze–thaw-related soil N〈sub〉2〈/sub〉O emissions but inhibited soil respiration and CH〈sub〉4〈/sub〉 oxidation. NO〈sub〉3〈/sub〉〈sup〉–〈/sup〉-N additions induced significantly higher cumulative N〈sub〉2〈/sub〉O emissions during FTCs than NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-N additions. The soil respiration rates were significantly reduced with increasing levels of N additions and were positively correlated with the soil DOC and MBC contents. Soil CH〈sub〉4〈/sub〉 uptake was substantially inhibited by increasing levels of NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-N additions, but was significantly reduced only by high levels of NO〈sub〉3〈/sub〉〈sup〉–〈/sup〉-N additions. Our results indicate that N addition plays an important role in affecting soil GHG fluxes during FTCs. The effects of different forms and levels of N additions on soil GHG fluxes should be considered in future estimations of GHG budget in alpine meadows under a changing climate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 June 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 368〈/p〉 〈p〉Author(s): Yuting Zhou, Sonam Sherpa, M.B. McBride〈/p〉

Description: 〈p〉Publication date: 1 June 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 368〈/p〉 〈p〉Author(s): Lauren T. Bennett, Nina Hinko-Najera, Cristina Aponte, Craig R. Nitschke, Thomas A. Fairman, Melissa Fedrigo, Sabine Kasel〈/p〉

Description: 〈p〉Publication date: 15 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 367〈/p〉 〈p〉Author(s): Miaoping Xu, Dexin Gao, Shuyue Fu, Xuqiao Lu, Shaojun Wu, Xinhui Han, Gaihe Yang, Yongzhong Feng〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Anna Schneider, Florian Hirsch, Alexander Bonhage, Alexandra Raab, Thomas Raab〈/p〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): I.G. Torre, Juan J. Martín-Sotoca, J.C. Losada, Pilar López, A.M. Tarquis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Characterization of the complex soil structure is one the cornerstones of soil science and pore space detection is a crucial step in this process. Synthetic soil image construction has been proved to be an efficient resource for validating different binarization methods given that, unlike in real world, ground truth information is known. In this work, we introduce an improved Truncated Multifractal Method (TMM), to better simulate synthetic computed tomography (CT) soil images and then we generate 150 synthetic images with three different porosities (7%, 12% and 17%), both in greyscale and in binary scale (pore spaces). Synthetic images are then compared with two sets of 260 slides of real CT soil images, in order to validate the goodness of the method. All images are subjected to multifractal analysis where we show a detailed comparative analysis of parameters such as lacunarity, characteristic length and multifractal spectrum, that are calculated both for the whole set of synthetic (greyscale and binary) and for the sets of real CT soil images. With respect to lacunarity, a not previously reported inverse relationship between binary and grey lacunarity is found for this range of porosities. Moreover, we have also reported a new relationship between lacunarity and characteristic length. Similar multifractal results, that we obtain for real CT and synthetic soil images, prove that TMM is a reasonable solution to create simulated CT soil images. Finally, a segmentation test was carried out, using TMM synthetic greyscale soil images and its binary counterpart as ground-truth information, evaluating global (Otsu) and local (Combining Singularity-CA) binarization methods, where we report better performance for the last.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Yakun Zhang, Wenjun Ji, Daniel D. Saurette, Tahmid Huq Easher, Hongyi Li, Zhou Shi, Viacheslav I. Adamchuk, Asim Biswas〈/p〉

Description: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 366〈/p〉 〈p〉Author(s): Farzad Parsadoust, Mehran Shirvani, Hossein Shariatmadari, Mohammad Dinari〈/p〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Daniel Puppe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biogenic silicon (BSi) has been found to play a fundamental role in the link between global Si and carbon cycles, because it represents a key factor in the control of Si fluxes from terrestrial to aquatic ecosystems. Furthermore, various beneficial effects of Si accumulation in plants have been revealed, i.e., increased plant growth and resistance against abiotic and biotic stresses. Due to intensified land use humans directly influence Si cycling on a global scale. For example, Si exports through harvested crops and increased erosion rates generally lead to a Si loss in agricultural systems with implications for Si bioavailability in agricultural soils, which is controlled by BSi to a great extent. However, while corresponding research on phytogenic BSi (i.e., BSi synthesized by plants) has been established for decades now, studies dealing with protozoic BSi (i.e., BSi synthesized by testate amoebae) have been conducted just recently and in the current review I summarized the findings of these field and laboratory studies. My review clearly highlights the potential of testate amoebae for Si cycling in terrestrial ecosystems and identifies knowledge gaps that have to be filled by future studies. In this context, especially the importance of single idiosomes (i.e., the building blocks of testate amoeba shells) is emphasized as there are no data on total protozoic Si pool quantities (represented by intact shells and single idiosomes) available yet. The filling of these knowledge gaps will be crucial for a detailed understanding of the role of testate amoebae in the biogeochemistry of terrestrial ecosystems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 365〈/p〉 〈p〉Author(s): Cheng Ji, Shuqing Li, Yajun Geng, Yiming Yuan, Junzhang Zhi, Kai Yu, Zhaoqiang Han, Shuang Wu, Shuwei Liu, Jianwen Zou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Acidic soils are hotspots of nitrous oxide (N〈sub〉2〈/sub〉O) and nitric oxide (NO) and biochar is documented to have the potential for mitigating N〈sub〉2〈/sub〉O and NO. The N〈sub〉2〈/sub〉O and NO emissions associated with soil functional genes and physicochemical properties under biochar amendment remains unclear in acidic soils. Here, we carried out a two-year field study to examine the responses of soil N〈sub〉2〈/sub〉O and NO emissions to biochar amendment in a subtropical tea plantation in China. Measurements of N〈sub〉2〈/sub〉O and NO fluxes were taken from inter-row soils using the static chamber method. We also measured the seasonal changes in soil key nitrogen (N)-cycling functional genes and physicochemical properties. Annual N〈sub〉2〈/sub〉O and NO emissions averaged 27.31 kg N〈sub〉2〈/sub〉O-N ha〈sup〉−1〈/sup〉 yr〈sup〉−1〈/sup〉 and 8.75 kg NO-N ha〈sup〉−1〈/sup〉 yr〈sup〉−1〈/sup〉 for the N fertilizer applied plots, which were decreased by 24% and 16% due to biochar application, respectively. In addition, both potential nitrification (PNR) and denitrification (PDR) rates were stimulated by biochar amendment, which significantly increased the abundances of bacterial 〈em〉amoA〈/em〉 (AOB), 〈em〉nirK〈/em〉 and 〈em〉nosZ〈/em〉 genes. Changes in the composition of the N〈sub〉2〈/sub〉O-related microbial functional community were closely associated with soil PNR, pH, DOC, and NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N contents. The ratios of NO/N〈sub〉2〈/sub〉O were mainly lower than 1, suggesting that N〈sub〉2〈/sub〉O was produced mostly through denitrification rather than nitrification. There were negative correlations between soil N〈sub〉2〈/sub〉O and NO emissions and soil PDR and pH, and soil N〈sub〉2〈/sub〉O emissions were negatively correlated with 〈em〉nosZ〈/em〉 gene abundances. Together, the decrease in N〈sub〉2〈/sub〉O and NO emissions following biochar application could be largely attributed to the enhanced denitrification process, in which biochar enriched the 〈em〉nirK〈/em〉 and 〈em〉nosZ〈/em〉 genes abundance, resulting from the enhancement of soil DOC and pH in acidic soils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 364〈/p〉 〈p〉Author(s): Wietse Wiersma, Martine J. van der Ploeg, Ian J.M.H. Sauren, Cathelijne R. Stoof〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biochar has been lauded as a cure-all for improving water availability in soils. Yet the effect of pyrolysis temperature and feedstock type on biochar hydraulic properties and its subsequent effects on soils are not well known. We therefore systematically studied water retention, saturated hydraulic conductivity (K〈sub〉sat〈/sub〉) and hydrophobicity of 12 standard biochars (six feedstocks and two pyrolysis temperatures) developed by the UK Biochar Research Centre. The hydraulic properties were determined for pure crushed biochar, as well as for a sandy soil amended with 10 t ha〈sup〉−1〈/sup〉 biochar (assessed three times over a period of 15 months). For pure biochar, the effect of feedstock-temperature treatments on the water retention curve was negligible. Rice husk at a pyrolysis temperature of 700 °C had a significantly lower saturated water content, plant available water content and K〈sub〉sat〈/sub〉 than all other biochar treatments. This can be attributed to its severe hydrophobicity: while all other treatments were non-hydrophobic and rice husk at 550 °C and 〈em〉Miscanthus〈/em〉 straw at 550 °C were both strongly hydrophobic, rice husk at 700 °C was severely hydrophobic. Incorporation of the biochar into a sandy soil did not significantly influence soil water retention, saturated hydraulic conductivity and hydrophobicity. There were also no significant differences between the biochar treatments. These results indicate that except for rice husk at 700 °C the different biochar feedstock types and pyrolysis temperatures yield surprisingly similar material in terms of hydraulic characteristics. Improved soil hydrology should not be a main reason to apply biochar on sandy soils, but if biochar is applied differences in hydrophobicity should be considered.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118323565-ga1.jpg" width="489" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉