Pub Date : 2024-06-04DOI: 10.5194/soil-10-349-2024
Claude Raoul Müller, Johan Six, Liesa Brosens, Philipp Baumann, Jean Paolo Gomes Minella, Gerard Govers, Marijn Van de Broek
Abstract. Predicting the quantity of soil organic carbon (SOC) requires understanding how different factors control the amount of SOC. Land use has a major influence on the function of the soil as a carbon sink, as shown by substantial organic carbon (OC) losses from the soil upon deforestation. However, predicting the degree to which land use change affects the OC content in soils and the depth down to which this occurs requires context-specific information related to, for example, climate, geochemistry, and land use history. In this study, 266 samples from forests and agricultural fields were collected from 94 soil profiles down to 300 cm depth in a subtropical region (Arvorezinha, southern Brazil) to study the impact of land use on the amount of stabilized OC along the soil profile. We found that the stabilized OC content was not affected by land use below a depth of 90 cm. Along the soil profile, the amount of stabilized OC was predominantly controlled by land use and depth in addition to the silt and clay content and aluminium ion concentrations. Below 100 cm, none of the soil profiles reached a concentration of stabilized OC above 50 % of the stabilized OC saturation point (i.e. the maximum OC concentration that can physically be stabilized in these soils). Based on these results, we argue that it is unlikely that deeper soil layers can serve as an OC sink over a timescale relevant to global climate change due to the limited OC input in these deeper layers. Furthermore, we found that the soil weathering degree was not a relevant control on the amount of stabilized OC in our profiles because of the high weathering degree of the studied soils. It is therefore suggested that, while the soil weathering degree might be an effective controlling factor of OC stabilization over a large spatial scale, it is not an informative measure for this process at regional and local scales (with similar climate, bedrock, and weathering history) in highly weathered soils.
{"title":"The limited effect of deforestation on stabilized subsoil organic carbon in a subtropical catchment","authors":"Claude Raoul Müller, Johan Six, Liesa Brosens, Philipp Baumann, Jean Paolo Gomes Minella, Gerard Govers, Marijn Van de Broek","doi":"10.5194/soil-10-349-2024","DOIUrl":"https://doi.org/10.5194/soil-10-349-2024","url":null,"abstract":"Abstract. Predicting the quantity of soil organic carbon (SOC) requires understanding how different factors control the amount of SOC. Land use has a major influence on the function of the soil as a carbon sink, as shown by substantial organic carbon (OC) losses from the soil upon deforestation. However, predicting the degree to which land use change affects the OC content in soils and the depth down to which this occurs requires context-specific information related to, for example, climate, geochemistry, and land use history. In this study, 266 samples from forests and agricultural fields were collected from 94 soil profiles down to 300 cm depth in a subtropical region (Arvorezinha, southern Brazil) to study the impact of land use on the amount of stabilized OC along the soil profile. We found that the stabilized OC content was not affected by land use below a depth of 90 cm. Along the soil profile, the amount of stabilized OC was predominantly controlled by land use and depth in addition to the silt and clay content and aluminium ion concentrations. Below 100 cm, none of the soil profiles reached a concentration of stabilized OC above 50 % of the stabilized OC saturation point (i.e. the maximum OC concentration that can physically be stabilized in these soils). Based on these results, we argue that it is unlikely that deeper soil layers can serve as an OC sink over a timescale relevant to global climate change due to the limited OC input in these deeper layers. Furthermore, we found that the soil weathering degree was not a relevant control on the amount of stabilized OC in our profiles because of the high weathering degree of the studied soils. It is therefore suggested that, while the soil weathering degree might be an effective controlling factor of OC stabilization over a large spatial scale, it is not an informative measure for this process at regional and local scales (with similar climate, bedrock, and weathering history) in highly weathered soils.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"25 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141246588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. A new soil nitrate monitoring system that was installed in a cultivated field enabled us, for the first time, to control the nitrate concentration across the soil profile. The monitoring system was installed in a full-scale agricultural greenhouse setup that was used for growing a bell pepper crop. Continuous measurements of soil nitrate concentrations were performed across the soil profile of two plots: (a) an adjusted fertigation plot, in which the fertigation regime was frequently adjusted according to the dynamic variations in soil nitrate concentration, and (b) a control plot, in which the fertigation was managed according to a predetermined fertigation schedule that is standard practice for the area. The results enabled an hourly resolution in tracking the dynamic soil nitrate concentration variations in response to daily fertigation and crop demand. Nitrate–nitrogen (N–NO3) concentrations in and below the root zone, under the control plot, reached very high levels of ∼ 180 ppm throughout the entire season. Obviously, this concentration reflects excessive fertigation, which is far beyond the plant demand, entailing severe groundwater pollution potential. On the other hand, frequent adjustments of the fertigation regime, which were carried out under the adjusted fertigation plot, enabled control of the soil nitrate concentration around the desired concentration threshold. This enabled a substantial reduction of 38 % in fertilizer application while maintaining maximum crop yield and quality. Throughout this experiment, decision-making on the fertigation adjustments was done manually based on visual inspections of the soil's reactions to changes in the fertigation regime. Nevertheless, it is obvious that an algorithm that continuously processes the soil nitrate concentration across the soil profile and provides direct fertigation commands could act as a “fertistat” that sets the soil nutrients at a desired optimal level. Consequently, it is concluded that fertigation that is based on continuous monitoring of the soil nitrate concentration may ensure nutrient application that accounts for plant demand, improves agricultural profitability, minimizes nitrate down-leaching and significantly reduces water resource pollution.
{"title":"Optimized fertilization using online soil nitrate data","authors":"Yonatan Yekutiel, Yuval Rotem, Shlomi Arnon, Ofer Dahan","doi":"10.5194/soil-10-335-2024","DOIUrl":"https://doi.org/10.5194/soil-10-335-2024","url":null,"abstract":"Abstract. A new soil nitrate monitoring system that was installed in a cultivated field enabled us, for the first time, to control the nitrate concentration across the soil profile. The monitoring system was installed in a full-scale agricultural greenhouse setup that was used for growing a bell pepper crop. Continuous measurements of soil nitrate concentrations were performed across the soil profile of two plots: (a) an adjusted fertigation plot, in which the fertigation regime was frequently adjusted according to the dynamic variations in soil nitrate concentration, and (b) a control plot, in which the fertigation was managed according to a predetermined fertigation schedule that is standard practice for the area. The results enabled an hourly resolution in tracking the dynamic soil nitrate concentration variations in response to daily fertigation and crop demand. Nitrate–nitrogen (N–NO3) concentrations in and below the root zone, under the control plot, reached very high levels of ∼ 180 ppm throughout the entire season. Obviously, this concentration reflects excessive fertigation, which is far beyond the plant demand, entailing severe groundwater pollution potential. On the other hand, frequent adjustments of the fertigation regime, which were carried out under the adjusted fertigation plot, enabled control of the soil nitrate concentration around the desired concentration threshold. This enabled a substantial reduction of 38 % in fertilizer application while maintaining maximum crop yield and quality. Throughout this experiment, decision-making on the fertigation adjustments was done manually based on visual inspections of the soil's reactions to changes in the fertigation regime. Nevertheless, it is obvious that an algorithm that continuously processes the soil nitrate concentration across the soil profile and provides direct fertigation commands could act as a “fertistat” that sets the soil nutrients at a desired optimal level. Consequently, it is concluded that fertigation that is based on continuous monitoring of the soil nitrate concentration may ensure nutrient application that accounts for plant demand, improves agricultural profitability, minimizes nitrate down-leaching and significantly reduces water resource pollution.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"27 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141159692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Land planning projects aiming to maximise soil organic carbon (SOC) stocks are increasing in number and scope. In response, a rising number of studies assess SOC additional storage capacities over regional to global spatial scales. In order to provide realistic values transferrable beyond the scientific community, SOC storage capacity assessments should consider the timescales over which this capacity might be reached, considering the effects of C inputs, soil type and depth on soil C dynamics. This research was conducted in a 320 km2 territory in North-eastern France where eight contrasted soil types have been identified, characterized and mapped thanks to a high density of fully-described soil profiles. Continuous profiles of SOC stocks were interpolated for each soil type and land use (cropland, grassland or forest). Depth-dependent estimates of maximum SOC additional storage capacity using the Hassink equation and a data-driven approach were compared. We used a novel method that uses the data-driven approach to constrain C inputs in a simple model of depth-dependent C dynamics to simulate SOC accrual over 25 years, and mapped the SOC stocks, maximum additional storage capacity and stock evolution. SOC stocks and maximum additional storage capacities are highly heterogenous over the region of study. Median SOC stocks range from 78–333 tC ha-1. Data-driven maximum SOC additional storage capacities vary from 19 tC ha-1 in forested Leptosols to 197 tC ha-1 in grassland Gleysols. Estimations of SOC maximum additional storage capacities based on the Hassink approach led to unrealistic vertical distributions of SOC stock, with particular overestimation in the deeper layers. Crucially, the simulated SOC accrual over 25 years was five times lower than the maximum SOC additional storage capacity (0.57 and 2.5 MgC respectively). Further consideration of depth-dependent SOC dynamics in different soil types is therefore needed to provide targets of SOC storage over timescales relevant to public policies aiming to approach carbon neutrality by 2050.
{"title":"Depth-dependence of soil organic carbon additional storage capacity in different soil types by the 2050 target for carbon neutrality","authors":"Clémentine Chirol, Geoffroy Séré, Paul-Olivier Redon, Claire Chenu, Delphine Derrien","doi":"10.5194/egusphere-2024-1284","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1284","url":null,"abstract":"<strong>Abstract.</strong> Land planning projects aiming to maximise soil organic carbon (SOC) stocks are increasing in number and scope. In response, a rising number of studies assess SOC additional storage capacities over regional to global spatial scales. In order to provide realistic values transferrable beyond the scientific community, SOC storage capacity assessments should consider the timescales over which this capacity might be reached, considering the effects of C inputs, soil type and depth on soil C dynamics. This research was conducted in a 320 km<sup>2</sup> territory in North-eastern France where eight contrasted soil types have been identified, characterized and mapped thanks to a high density of fully-described soil profiles. Continuous profiles of SOC stocks were interpolated for each soil type and land use (cropland, grassland or forest). Depth-dependent estimates of maximum SOC additional storage capacity using the Hassink equation and a data-driven approach were compared. We used a novel method that uses the data-driven approach to constrain C inputs in a simple model of depth-dependent C dynamics to simulate SOC accrual over 25 years, and mapped the SOC stocks, maximum additional storage capacity and stock evolution. SOC stocks and maximum additional storage capacities are highly heterogenous over the region of study. Median SOC stocks range from 78–333 tC ha<sup>-1</sup>. Data-driven maximum SOC additional storage capacities vary from 19 tC ha<sup>-1</sup> in forested Leptosols to 197 tC ha<sup>-1</sup> in grassland Gleysols. Estimations of SOC maximum additional storage capacities based on the Hassink approach led to unrealistic vertical distributions of SOC stock, with particular overestimation in the deeper layers. Crucially, the simulated SOC accrual over 25 years was five times lower than the maximum SOC additional storage capacity (0.57 and 2.5 MgC respectively). Further consideration of depth-dependent SOC dynamics in different soil types is therefore needed to provide targets of SOC storage over timescales relevant to public policies aiming to approach carbon neutrality by 2050.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"26 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141156629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-24DOI: 10.5194/egusphere-2024-1470
Rebecca J. Even, Megan B. Machmuller, Jocelyn M. Lavallee, Jane T. Zelikova, M. Francesca Cotrufo
Abstract. To build confidence in the efficacy of soil carbon (C) crediting programs, precise quantification of soil organic carbon C (SOC) is critical. Detecting a true change in SOC after a management shift has occurred, specifically in agricultural lands, is difficult as it requires robust soil sampling and soil processing procedures. Informative and meaningful comparisons across spatial and temporal time scales can only be made with reliable soil C measurements and estimates, which begin on the ground and in soil testing facilities. To gauge soil C measurement inter-variability, we conducted a blind external service laboratory comparison across eight laboratories selected based on status and involvement in SOC quantification for C markets. To better understand how soil processing procedures and quantification methods commonly used in soil testing laboratories affect soil C concentration measurements, we designed an internal experiment assessing the individual effect of several alternative procedures (i.e., sieving, fine grinding, and drying) and quantification methods on total (TC), inorganic (SIC), and organic (SOC) soil C concentration estimates. We analyzed 12 different agricultural soils using 11 procedures that varied either in the sieving, fine grinding, drying, or quantification step. We found that a mechanical grinder, the most commonly used method for sieving in service laboratories, did not effectively remove coarse materials (i.e., roots and rocks), thus resulted in higher variability and significantly different C concentration measurements from the other sieving procedures (i.e., 8 + 2 mm, 4 mm, and 2 mm with rolling pin). A finer grind generally resulted in a lower coefficient of variance where the finest grind to < 125 µm had the lowest coefficient of variance, followed by the < 250 µm grind, and lastly the < 2000 µm grind. Not drying soils in an oven (at 105 °C) prior to elemental analysis on average resulted in a relative difference of 3.5 % lower TC, and 5 % lower SOC due to inadequate removal of moisture. Compared to the reference method used in our study where % TC was quantified by dry combustion on an elemental analyzer, % SIC was measured using a pressure transducer, and % SOC was calculated by the difference of % TC and % SIC, predictions of all three soil properties (% TC, % SIC, % SOC) using Fourier Transformed Infrared Spectroscopy were in high agreement (R2 = 0.97, 0.99, 0.90, respectively). For % SOC, quantification by loss on ignition had a low coefficient of variance (5.42 ± 3.06 %) but the least agreement (R2 = 0.83) with the reference method.
{"title":"Large errors in common soil carbon measurements due to sample processing","authors":"Rebecca J. Even, Megan B. Machmuller, Jocelyn M. Lavallee, Jane T. Zelikova, M. Francesca Cotrufo","doi":"10.5194/egusphere-2024-1470","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1470","url":null,"abstract":"<strong>Abstract.</strong> To build confidence in the efficacy of soil carbon (C) crediting programs, precise quantification of soil organic carbon C (SOC) is critical. Detecting a true change in SOC after a management shift has occurred, specifically in agricultural lands, is difficult as it requires robust soil sampling and soil processing procedures. Informative and meaningful comparisons across spatial and temporal time scales can only be made with reliable soil C measurements and estimates, which begin on the ground and in soil testing facilities. To gauge soil C measurement inter-variability, we conducted a blind external service laboratory comparison across eight laboratories selected based on status and involvement in SOC quantification for C markets. To better understand how soil processing procedures and quantification methods commonly used in soil testing laboratories affect soil C concentration measurements, we designed an internal experiment assessing the individual effect of several alternative procedures (i.e., sieving, fine grinding, and drying) and quantification methods on total (TC), inorganic (SIC), and organic (SOC) soil C concentration estimates. We analyzed 12 different agricultural soils using 11 procedures that varied either in the sieving, fine grinding, drying, or quantification step. We found that a mechanical grinder, the most commonly used method for sieving in service laboratories, did not effectively remove coarse materials (i.e., roots and rocks), thus resulted in higher variability and significantly different C concentration measurements from the other sieving procedures (i.e., 8 + 2 mm, 4 mm, and 2 mm with rolling pin). A finer grind generally resulted in a lower coefficient of variance where the finest grind to < 125 µm had the lowest coefficient of variance, followed by the < 250 µm grind, and lastly the < 2000 µm grind. Not drying soils in an oven (at 105 °C) prior to elemental analysis on average resulted in a relative difference of 3.5 % lower TC, and 5 % lower SOC due to inadequate removal of moisture. Compared to the reference method used in our study where % TC was quantified by dry combustion on an elemental analyzer, % SIC was measured using a pressure transducer, and % SOC was calculated by the difference of % TC and % SIC, predictions of all three soil properties (% TC, % SIC, % SOC) using Fourier Transformed Infrared Spectroscopy were in high agreement (R<sup>2</sup> = 0.97, 0.99, 0.90, respectively). For % SOC, quantification by loss on ignition had a low coefficient of variance (5.42 ± 3.06 %) but the least agreement (R<sup>2</sup> = 0.83) with the reference method.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"137 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141092051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-22DOI: 10.5194/egusphere-2024-1466
W. Marijn van der Meij, Svenja Riedesel, Tony Reimann
Abstract. Soil bioturbation plays a key role in soil functions such as carbon and nutrient cycling. Despite its importance, fundamental knowledge on how different organisms and processes impact the rates and patterns of soil mixing during bioturbation is lacking. However, this information is essential for understanding the effects of bioturbation in present-day soil functions and on long-term soil evolution. Luminescence, a light-sensitive mineral property, serves as a valuable tracer for soil bioturbation. The luminescence signal resets (bleaches) when a soil particle is exposed to daylight at the soil surface and accumulates when the particle is buried in the soil, acting as a proxy for subsurface residence times. In this study, we compiled three luminescence-based datasets of soil mixing by different biota and compared them to numerical simulations of bioturbation using the soil-landscape evolution model ChronoLorica. The goal was to understand how different mixing processes affect depth profiles of luminescence-based metrics, such as the modal age, width of the age distributions and the fraction of bleached particles. We focus on two main bioturbation processes: mounding (advective transport of soil material to the surface) and subsurface mixing (diffusive subsurface transport). Each process has a distinct effect on the luminescence metrics, which we summarized in a conceptual diagram to help with qualitative interpretation of luminescence-based depth profiles. A first attempt to derive quantitative information from luminescence datasets through model calibration showed promising results, but also highlighted gaps in data that must be addressed before accurate, quantitative estimates of bioturbation rates and processes are possible. The new numerical formulations of bioturbation, which are provided in an accompanying modelling tool, provide new possibilities for calibration and more accurate simulation of the processes in soil function and soil evolution models.
{"title":"Mixed signals: interpreting mixing patterns of different soil bioturbation processes through luminescence and numerical modelling","authors":"W. Marijn van der Meij, Svenja Riedesel, Tony Reimann","doi":"10.5194/egusphere-2024-1466","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1466","url":null,"abstract":"<strong>Abstract.</strong> Soil bioturbation plays a key role in soil functions such as carbon and nutrient cycling. Despite its importance, fundamental knowledge on how different organisms and processes impact the rates and patterns of soil mixing during bioturbation is lacking. However, this information is essential for understanding the effects of bioturbation in present-day soil functions and on long-term soil evolution. Luminescence, a light-sensitive mineral property, serves as a valuable tracer for soil bioturbation. The luminescence signal resets (bleaches) when a soil particle is exposed to daylight at the soil surface and accumulates when the particle is buried in the soil, acting as a proxy for subsurface residence times. In this study, we compiled three luminescence-based datasets of soil mixing by different biota and compared them to numerical simulations of bioturbation using the soil-landscape evolution model ChronoLorica. The goal was to understand how different mixing processes affect depth profiles of luminescence-based metrics, such as the modal age, width of the age distributions and the fraction of bleached particles. We focus on two main bioturbation processes: mounding (advective transport of soil material to the surface) and subsurface mixing (diffusive subsurface transport). Each process has a distinct effect on the luminescence metrics, which we summarized in a conceptual diagram to help with qualitative interpretation of luminescence-based depth profiles. A first attempt to derive quantitative information from luminescence datasets through model calibration showed promising results, but also highlighted gaps in data that must be addressed before accurate, quantitative estimates of bioturbation rates and processes are possible. The new numerical formulations of bioturbation, which are provided in an accompanying modelling tool, provide new possibilities for calibration and more accurate simulation of the processes in soil function and soil evolution models.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"40 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141079161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-17DOI: 10.5194/soil-10-321-2024
Sebastian Vogel, Katja Emmerich, Ingmar Schröter, Eric Bönecke, Wolfgang Schwanghart, Jörg Rühlmann, Eckart Kramer, Robin Gebbers
Abstract. In situ soil pH measurements with ion-selective electrodes (ISEs) are receiving increasing attention in soil mapping for precision agriculture as they can avoid time-consuming sampling and off-site laboratory work. However, unlike the standard laboratory protocol, in situ pH measurements are carried out at lower and varying soil moisture contents (SMCs), which can have a pronounced effect on the sensor readings. In addition, as the contact with the soil during in situ measurements should be relatively short, effects of soil texture could be expected because texture controls the migration of protons to the electrode interface. This may be exacerbated by the fact that the electrodes used for in situ measurements are made of less sensitive but more robust materials as compared to the standard glass electrode. Therefore, the aim of the present study was to investigate the effect of soil moisture and soil texture on pH measurements using robust antimony and epoxy-body ISEs pressed directly into the soil for 30 s. The SMC was gradually increased from dry conditions to field capacity. A wide range of soil texture classes were included, with sand, silt, and clay contents ranging from 16 % to 91 %, 5 % to 44 %, and 4 % to 65 %, respectively. An exponential model was fitted to the data to quantify the relationship between SMC and pH. The results show that an increase in SMC causes a maximum increase in pH of approximately 1.5 pH units, regardless of the type of pH ISE used. Furthermore, for sandy soil textures, a rather linear relationship between pH and SMC was observed, whereas, with decreasing mean particle diameter (MPD), the model had a pronounced exponential shape, i.e., a greater pH increase at low SMC and a plateau effect at high SMC. With increasing SMC, the pH values asymptotically approached the standard pH measured with a glass electrode in 0.01 M CaCl2 (soil : solution ratio of 1:2.5). Thus, at high SMC, subsequent calibration of the sensor pH values to the standard pH value is negligible, which may be relevant for using the sensor pH data for lime requirement estimates. The pH measurement error decreases exponentially with increasing soil moisture and increases with decreasing MPD. Using a knee point detection, reliable pH values were obtained for SMC > 11 %, irrespective of the pH ISE used. An analysis of the regression coefficients of the fitted exponential model showed that the maximum pH increase also depends on soil texture; i.e., the influence of soil moisture variation on the pH value increases with decreasing MPD. Moreover, the concavity of the exponential curve increases with decreasing MPD.
{"title":"The effect of soil moisture content and soil texture on fast in situ pH measurements with two types of robust ion-selective electrodes","authors":"Sebastian Vogel, Katja Emmerich, Ingmar Schröter, Eric Bönecke, Wolfgang Schwanghart, Jörg Rühlmann, Eckart Kramer, Robin Gebbers","doi":"10.5194/soil-10-321-2024","DOIUrl":"https://doi.org/10.5194/soil-10-321-2024","url":null,"abstract":"Abstract. In situ soil pH measurements with ion-selective electrodes (ISEs) are receiving increasing attention in soil mapping for precision agriculture as they can avoid time-consuming sampling and off-site laboratory work. However, unlike the standard laboratory protocol, in situ pH measurements are carried out at lower and varying soil moisture contents (SMCs), which can have a pronounced effect on the sensor readings. In addition, as the contact with the soil during in situ measurements should be relatively short, effects of soil texture could be expected because texture controls the migration of protons to the electrode interface. This may be exacerbated by the fact that the electrodes used for in situ measurements are made of less sensitive but more robust materials as compared to the standard glass electrode. Therefore, the aim of the present study was to investigate the effect of soil moisture and soil texture on pH measurements using robust antimony and epoxy-body ISEs pressed directly into the soil for 30 s. The SMC was gradually increased from dry conditions to field capacity. A wide range of soil texture classes were included, with sand, silt, and clay contents ranging from 16 % to 91 %, 5 % to 44 %, and 4 % to 65 %, respectively. An exponential model was fitted to the data to quantify the relationship between SMC and pH. The results show that an increase in SMC causes a maximum increase in pH of approximately 1.5 pH units, regardless of the type of pH ISE used. Furthermore, for sandy soil textures, a rather linear relationship between pH and SMC was observed, whereas, with decreasing mean particle diameter (MPD), the model had a pronounced exponential shape, i.e., a greater pH increase at low SMC and a plateau effect at high SMC. With increasing SMC, the pH values asymptotically approached the standard pH measured with a glass electrode in 0.01 M CaCl2 (soil : solution ratio of 1:2.5). Thus, at high SMC, subsequent calibration of the sensor pH values to the standard pH value is negligible, which may be relevant for using the sensor pH data for lime requirement estimates. The pH measurement error decreases exponentially with increasing soil moisture and increases with decreasing MPD. Using a knee point detection, reliable pH values were obtained for SMC > 11 %, irrespective of the pH ISE used. An analysis of the regression coefficients of the fitted exponential model showed that the maximum pH increase also depends on soil texture; i.e., the influence of soil moisture variation on the pH value increases with decreasing MPD. Moreover, the concavity of the exponential curve increases with decreasing MPD.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"64 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140953635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.5194/egusphere-2024-1143
Thiago M. Inagaki, Simon Weldon, Franziska B. Bucka, Eva Farkas, Daniel P. Rasse
Abstract. Quantifying the impact of biochar on carbon persistence across soil textures is complex, owing to the variability in soil conditions. Using artificial soils with precise textural and mineral composition, we could disentangle the effects of biochar from the effects of soil particle size. We can show that biochar application significantly reduces early-stage carbon mineralization rates of plant residues in various soil textures (from 5 to 41 % clay) but more significantly in sandy soils. This finding suggests that biochar can compensate for the lack of clay in promoting C persistence in soil systems. This short report significantly contributes to understanding soil texture and biochar application interactions.
{"title":"Biochar reduces early-stage mineralization rates of plant residues more in coarse than fine-texture soils – an artificial soil approach","authors":"Thiago M. Inagaki, Simon Weldon, Franziska B. Bucka, Eva Farkas, Daniel P. Rasse","doi":"10.5194/egusphere-2024-1143","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1143","url":null,"abstract":"<strong>Abstract.</strong> Quantifying the impact of biochar on carbon persistence across soil textures is complex, owing to the variability in soil conditions. Using artificial soils with precise textural and mineral composition, we could disentangle the effects of biochar from the effects of soil particle size. We can show that biochar application significantly reduces early-stage carbon mineralization rates of plant residues in various soil textures (from 5 to 41 % clay) but more significantly in sandy soils. This finding suggests that biochar can compensate for the lack of clay in promoting C persistence in soil systems. This short report significantly contributes to understanding soil texture and biochar application interactions.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"12 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140845479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.5194/egusphere-2024-1014
Rotem Golan, Ittai Gavrieli, Roee Katzir, Galit Sharabi, Uri Nachshon
Abstract. Many of the globe arid areas are exposed to severe soil contamination events, due to the presence of highly pollutant industries in these regions. In this work a case study from the Ashalim basin, at the Judean desert, Israel was used to examine the nature of solutes and contaminants transport in sandy terraces of an ephemeral stream that was exposed to a severe pollution event. In order to to shed new light on contaminants distribution along the soil profile and transport mechanisms, in arid environments, three complimentary approaches were used: (1) Periodic on-site soil profile sampling, recording the annual solute transport dynamics; (2) Laboratory analyses and controlled experiments in a rain simulator, to characterize solutes release and transport; and (3) Numerical simulation was used to define and understand the main associated processes. The study highlights the stubborn nature of the pollutants in these natural setting that dictates they will remain near the soil surface, despite the presence of sporadic rain events. It was shown that a vertical circulation of the contaminates is occurring with soil wetting and drying cycles. The ‘surface evaporation capacitor’ concept of Or and Lehmann from 2019 was examined and compared to field measurements and numerical simulations, and found to be a useful tool to predict the fate of the contaminants along the soil profile.
{"title":"Soil contamination in arid environments and assessment of remediation applying surface evaporation capacitor model; a case study from the Judean Desert, Israel","authors":"Rotem Golan, Ittai Gavrieli, Roee Katzir, Galit Sharabi, Uri Nachshon","doi":"10.5194/egusphere-2024-1014","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1014","url":null,"abstract":"<strong>Abstract.</strong> Many of the globe arid areas are exposed to severe soil contamination events, due to the presence of highly pollutant industries in these regions. In this work a case study from the Ashalim basin, at the Judean desert, Israel was used to examine the nature of solutes and contaminants transport in sandy terraces of an ephemeral stream that was exposed to a severe pollution event. In order to to shed new light on contaminants distribution along the soil profile and transport mechanisms, in arid environments, three complimentary approaches were used: (1) Periodic on-site soil profile sampling, recording the annual solute transport dynamics; (2) Laboratory analyses and controlled experiments in a rain simulator, to characterize solutes release and transport; and (3) Numerical simulation was used to define and understand the main associated processes. The study highlights the stubborn nature of the pollutants in these natural setting that dictates they will remain near the soil surface, despite the presence of sporadic rain events. It was shown that a vertical circulation of the contaminates is occurring with soil wetting and drying cycles. The ‘surface evaporation capacitor’ concept of Or and Lehmann from 2019 was examined and compared to field measurements and numerical simulations, and found to be a useful tool to predict the fate of the contaminants along the soil profile.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"11 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140845846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-02DOI: 10.5194/soil-10-307-2024
Sam J. Leuthold, Jocelyn M. Lavallee, Bruno Basso, William F. Brinton, M. Francesca Cotrufo
Abstract. Spatiotemporal yield heterogeneity presents a significant challenge to agricultural sustainability efforts and can strain the economic viability of farming operations. Increasing soil organic matter (SOM) has been associated with increased crop productivity, as well as the mitigation of yield variability across time and space. Observations at the regional scale have indicated decreases in yield variability with increasing SOM. However, the mechanisms by which this variability is reduced remain poorly understood, especially at the farm scale. To better understand the relationship between SOM and yield heterogeneity, we examined its distribution between particulate organic matter (POM) and mineral-associated organic matter (MAOM) at the subfield scale within nine farms located in the central United States. We expected that the highest SOM concentrations would be found in stable, high-yielding zones and that the SOM pool in these areas would have a higher proportion of POM relative to other areas in the field. In contrast to our predictions, we found that unstable yield areas had significantly higher SOM than stable yield areas and that there was no significant difference in the relative contribution of POM to total SOM across different yield stability zones. Our results further indicate that MAOM abundance was primarily explained by interactions between crop productivity and edaphic properties such as texture, which varied amongst stability zones. However, we were unable to link POM abundance to soil properties or cropping system characteristics. Instead, we posit that POM dynamics in these systems may be controlled by differences in decomposition patterns between stable and unstable yield zones. Our results show that, at the subfield scale, increasing SOM may not directly confer increased yield stability. Instead, in fields with high spatiotemporal yield heterogeneity, SOM stocks may be determined by interactive effects of topography, weather, and soil characteristics on crop productivity and SOM decomposition. These findings suggest that POM has the potential to be a useful indicator of yield stability, with higher POM stocks in unstable zones, and highlights the need to consider these factors during soil sampling campaigns, especially when attempting to quantify farm-scale soil C stocks.
摘要时空产量异质性是农业可持续发展工作面临的一个重大挑战，并可能对农业经营的经济可行性造成压力。土壤有机质（SOM）的增加与作物产量的提高以及跨时空产量变化的减缓有关。区域范围的观测结果表明，随着土壤有机质的增加，产量变异性也会降低。然而，人们对降低这种变异性的机制仍然知之甚少，尤其是在农场尺度上。为了更好地理解 SOM 与产量异质性之间的关系，我们研究了位于美国中部的九个农场中，颗粒有机质（POM）和矿质相关有机质（MAOM）在亚田尺度上的分布情况。我们预计，SOM 浓度最高的区域是稳定的高产区，这些区域的 SOM 池中 POM 的比例会高于田间其他区域。与我们的预测相反，我们发现产量不稳定区域的 SOM 明显高于产量稳定区域，而且不同产量稳定区域的 POM 对总 SOM 的相对贡献率没有显著差异。我们的研究结果进一步表明，MAOM 的丰度主要是由作物生产力与质地等土壤特性之间的相互作用所解释的，而这些特性在不同的稳定区之间存在差异。然而，我们无法将 POM 丰度与土壤特性或种植系统特征联系起来。相反，我们认为这些系统中的 POM 动态可能受控于稳定产量区和不稳定产量区之间分解模式的差异。我们的研究结果表明，在亚田块尺度上，SOM 的增加可能不会直接带来产量稳定性的提高。相反，在具有高度时空产量异质性的田块中，SOM 储量可能是由地形、天气和土壤特性对作物产量和 SOM 分解的交互影响决定的。这些研究结果表明，POM 有可能成为产量稳定性的一个有用指标，在不稳定区域，POM 储量较高，这也强调了在土壤采样活动中考虑这些因素的必要性，尤其是在试图量化农场规模的土壤碳储量时。
{"title":"Shifts in controls and abundance of particulate and mineral-associated organic matter fractions among subfield yield stability zones","authors":"Sam J. Leuthold, Jocelyn M. Lavallee, Bruno Basso, William F. Brinton, M. Francesca Cotrufo","doi":"10.5194/soil-10-307-2024","DOIUrl":"https://doi.org/10.5194/soil-10-307-2024","url":null,"abstract":"Abstract. Spatiotemporal yield heterogeneity presents a significant challenge to agricultural sustainability efforts and can strain the economic viability of farming operations. Increasing soil organic matter (SOM) has been associated with increased crop productivity, as well as the mitigation of yield variability across time and space. Observations at the regional scale have indicated decreases in yield variability with increasing SOM. However, the mechanisms by which this variability is reduced remain poorly understood, especially at the farm scale. To better understand the relationship between SOM and yield heterogeneity, we examined its distribution between particulate organic matter (POM) and mineral-associated organic matter (MAOM) at the subfield scale within nine farms located in the central United States. We expected that the highest SOM concentrations would be found in stable, high-yielding zones and that the SOM pool in these areas would have a higher proportion of POM relative to other areas in the field. In contrast to our predictions, we found that unstable yield areas had significantly higher SOM than stable yield areas and that there was no significant difference in the relative contribution of POM to total SOM across different yield stability zones. Our results further indicate that MAOM abundance was primarily explained by interactions between crop productivity and edaphic properties such as texture, which varied amongst stability zones. However, we were unable to link POM abundance to soil properties or cropping system characteristics. Instead, we posit that POM dynamics in these systems may be controlled by differences in decomposition patterns between stable and unstable yield zones. Our results show that, at the subfield scale, increasing SOM may not directly confer increased yield stability. Instead, in fields with high spatiotemporal yield heterogeneity, SOM stocks may be determined by interactive effects of topography, weather, and soil characteristics on crop productivity and SOM decomposition. These findings suggest that POM has the potential to be a useful indicator of yield stability, with higher POM stocks in unstable zones, and highlights the need to consider these factors during soil sampling campaigns, especially when attempting to quantify farm-scale soil C stocks.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"7 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140819148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.5194/egusphere-2024-934
Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, Hanna Kekkonen
Abstract. We experimented a gradual water table rise at a highly degraded agricultural peat soil site with plots of willow, forage and mixed vegetation (set-aside) in southern Finland. We measured the emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) for four years. The mean annual ground water table depth was about 80, 40, 40 and 30 cm in 2019–2022, respectively. The results indicated that a 10 cm raise in the water table depth was able to slow down annual CO2 emissions from soil respiration by 0.87 Mg CO2-C ha-1. CH4 fluxes changed from uptake to emissions with a raise in the water table depth, and the maximum mean annual emission rate was 11 kg CH4-C. Nitrous oxide emissions ranged from 2 to 33 kg N2O-N ha-1 year; they were high from bare soil in the beginning of the experiment but decreased towards the end of the experiment. Short rotation cropping of willow reached net sequestration of carbon before harvest, but all treatments and years showed net loss of carbon based on the net ecosystem carbon balance. Overall, the short rotation coppice of willow had the most favourable carbon and greenhouse gas balance over the years (10 Mg CO2 eq. on the average over four years). The total greenhouse gas balance of the forage and set-aside treatments did not go under 27 Mg CO2 eq. ha-1 year-1 highlighting the challenge in curbing peat decomposition in highly degraded cultivated peatlands.
{"title":"Carbon balance and emissions of methane and nitrous oxide during four years of moderate rewetting of a cultivated peat soil site","authors":"Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, Hanna Kekkonen","doi":"10.5194/egusphere-2024-934","DOIUrl":"https://doi.org/10.5194/egusphere-2024-934","url":null,"abstract":"<strong>Abstract.</strong> We experimented a gradual water table rise at a highly degraded agricultural peat soil site with plots of willow, forage and mixed vegetation (set-aside) in southern Finland. We measured the emissions of carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) for four years. The mean annual ground water table depth was about 80, 40, 40 and 30 cm in 2019–2022, respectively. The results indicated that a 10 cm raise in the water table depth was able to slow down annual CO<sub>2</sub> emissions from soil respiration by 0.87 Mg CO<sub>2</sub>-C ha<sup>-1</sup>. CH<sub>4</sub> fluxes changed from uptake to emissions with a raise in the water table depth, and the maximum mean annual emission rate was 11 kg CH<sub>4</sub>-C. Nitrous oxide emissions ranged from 2 to 33 kg N<sub>2</sub>O-N ha<sup>-1</sup> year; they were high from bare soil in the beginning of the experiment but decreased towards the end of the experiment. Short rotation cropping of willow reached net sequestration of carbon before harvest, but all treatments and years showed net loss of carbon based on the net ecosystem carbon balance. Overall, the short rotation coppice of willow had the most favourable carbon and greenhouse gas balance over the years (10 Mg CO<sub>2</sub> eq. on the average over four years). The total greenhouse gas balance of the forage and set-aside treatments did not go under 27 Mg CO<sub>2</sub> eq. ha<sup>-1</sup> year<sup>-1</sup> highlighting the challenge in curbing peat decomposition in highly degraded cultivated peatlands.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"71 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140814333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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