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Accepted, edited articles are published here after author proofing to provide rapid publication and better access to the newest research. Articles are compiled into issues at dl.sciencesocieties.org/publications/sssaj, which includes the complete archive.

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Nouwakpo, S. K. and C.-H. Huang. 2012. A Fluidized Bed Technique for Estimating Soil Critical Shear Stress Soil Sci. Soc. Am. J. doi:10.2136/sssaj2012.0056

Current issue: Soil Sci. Soc. Am. J. 81(5)


    • Francesca Giannetti, Gherardo Chirici, Davide Travaglini, Francesca Bottalico, Enrico Marchi and Martina Cambi
      Assessment of Soil Disturbance Caused by Forest Operations by Means of Portable Laser Scanner and Soil Physical Parameters

      Forest operations can cause compaction and rutting, resulting in soil degradation processes. Soil damage is usually assessed through costly and time-consuming manual field measurements. The aim of this study is to investigate the impact of logging operations on soil using traditional ground surveys integrated with laser scanning data acquired by a terrestrial portable laser scanner (PLS). This approach provides an alternative to soil rut manual measurements. (continued)

      Core Ideas:
      • Forest operations may cause severe soil disturbances.
      • Soil impacts are usually assessed by time consuming methods.
      • Our study investigated the use of a portable laser scanner to assess forest soil disturbance.

      Published: October 19, 2017


    • Martin F. Jurgensen, Deborah S. Page-Dumroese, Robert E. Brown, Joanne M. Tirocke, Chris A. Miller, James B. Pickens and Min Wang
      Estimating Carbon and Nitrogen Pools in a Forest Soil: Influence of Soil Bulk Density Methods and Rock Content

      Soils with high rock content are common in many US forests, and contain large amounts of stored C. Accurate measurements of soil bulk density and rock content are critical for calculating and assessing changes in both C and nutrient pool size, but bulk density sampling methods have limitations and sources of variability. Therefore, we evaluated the use of small-diameter soil cores (SD), irregular soil volume excavation (IR), and a nuclear density gauge (ND) to measure bulk density and rock content, and estimate C and N pools in three 10-cm increments to a 30-cm depth in a glacial till soil in northern Wisconsin. Total and fine bulk densities were lower when measured with SD cores than with larger soil volume IR and ND methods. (continued)

      Core Ideas:
      • Three bulk density methods used in a rocky soil gave different total bulk density values, but not fine bulk density.
      • Bulk density sampling method had little effect on C and N pool estimates in the surface 20 cm of soil, but did so deeper in the soil.
      • Small-diameter cores probably underestimated total soil bulk density and C and N pools at deeper soil depths.
      • Rocks present on the soil surface cause an overestimation of soil C and N pools.

      Published: October 19, 2017


    • Anna S. Williams, Md. Rasel Parvej, David L. Holshouser, William H. Frame and Mark S. Reiter
      Correlation of Field-Moist, Oven-Dry, and Air-Dry Soil Potassium for Mid-Atlantic USA Soybean

      The extractable soil-K concentration, used for fertilizer-K recommendations, may be affected by soil drying. Although air or oven drying are the most common soil processing me, K from field-moist soil has been documented to be a better predictor of soil-K availabilities and fertilizer-K needs for soybean [Glycine max. (L.) Merr.] grown on fertile silt loam to clayey soils. We evaluated the effect of four soil processing methods (field-moist [FM], air-dry [AD], air-dry followed by oven-dry [ADOD], and oven-dry [OD]) in predicting extractable soil-K availability for soybean production on less fertile Mid-Atlantic sandy-textured soils. Twelve soybean field trials were conducted in 2014 on Coastal Plain and Piedmont soils in Virginia and North Carolina. (continued)

      Core Ideas:
      • Soil K extracted by each processing method were similar and strongly correlated with relative yield.
      • Soil K from FM, AD, and OD soils were equally good in predicting yield response to fertilizer-K.
      • Soil drying should not be an issue of concern in extracting soil K from soils in the US Mid-Atlantic.

      Published: October 19, 2017


    • Zane T. Walker, Jeffrey A. Coulter, Michael P. Russelle, Rodney T. Venterea, Antonio P. Mallarino, Joseph G. Lauer and Matt A. Yost
      Do Soil Tests Help Forecast Nitrogen Response in First-Year Corn Following Alfalfa on Fine-Textured Soils?

      Improved methods are needed to predict grain yield response to fertilizer N for first-year corn (Zea mays L.) following alfalfa (Medicago sativa L.) on fine-textured soils. Data from 21 site-years in the North Central Region of the United States were used to determine how Illinois soil nitrogen test (ISNT) and pre-sidedress soil nitrate test (PSNT) concentrations change during alfalfa–corn rotations and how they relate to mineralized N, available N, and grain yield response to fertilizer N in first-year corn. In five long-term crop rotation trials, ISNT and PSNT taken in the alfalfa phase did not change with alfalfa stand age, but PSNT concentration in first-year corn increased with alfalfa stand age in three of five trials. Across 21 site-years, the PSNT more accurately predicted corn response or nonresponse to fertilizer N than the ISNT (67 vs. (continued)

      Core Ideas:
      • ISNT and PSNT concentrations did not differ among alfalfa stand ages in five long-term trials.
      • Only PSNT concentration increased during first-year corn in three of five long-term trials.
      • The PSNT was less related to soil N mineralization and more related to available N than the ISNT.
      • The PSNT more accurately predicted corn response or nonresponse to fertilizer N than the ISNT.
      • The product of alfalfa stand age and PSNT separated N response in 87% of 15 independent site-years.

      Published: November 22, 2017

    • Juan B. Rodriguez
      Simple, Simultaneous Gravimetric Determination of Calcite and Dolomite in Calcareous Soils

      Literature pertaining to the determination of calcite and dolomite is not modern and generally describes slow methods that require expensive specialized apparatus. The objective of this paper is to describe a new method that requires no specialized equipment. The separation of calcite and dolomite was done by placing 0.2000 ± 0.0200 g of calcareous soil into a 6-mL glass vial with 4.0 mL of fresh 4 mol L–1 HCl–3% FeCl2 4H2O in a 50-mL Erlenmeyer flask. The Erlenmeyer flask was capped with the tubed rubber stopper and the carbonate meter’s (CM) initial weight was recorded to the accuracy of four decimal places. (continued)

      Core Ideas:
      • The carbonate meter (CM) method was modified to measure calcite and dolomite.
      • The modified carbonate meter (MCM) method efficiently separated calcite and dolomite.
      • The MCM method can be done in any soil testing lab.
      • The MCM technique not only measures calcite and dolomite but also total inorganic C
      • The MCM categorized calcareous soils as calcitic, dolomitic, and calcitic-dolomitic.

      Published: November 22, 2017

    • Qiang Zhu, Monica Ozores-Hampton, Yuncong C. Li and Rao S. Mylavarapu
      Comparing Extractants for Calibrating Potassium Rates for Tomato Grown on a Calcareous Soil

      Potassium application rates based on a reliable soil testing method are critical for maximizing crop yields and minimizing fertilizer costs. Vegetables grown on calcareous soils, however, have no soil test potassium (STK) interpretations in Florida. Therefore, the objectives of this study were to compare Mehlich-3, ammonium bicarbonate-DTPA (AB-DTPA), and water to estimate K availability and calibrate K rates for tomato (Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted during the winter seasons of 2014 and 2015. (continued)

      Core Ideas:
      • Water was ineffective to estimate K availability in calcareous soils in Florida.
      • Both Mehlich-3 and AB-DTPA can be used to calibrate K rates in calcareous soils.
      • High K level was above 213 and 183 mg kg–1 with Mehlich-3 and AB-DTPA, respectively.

      Published: November 22, 2017


    • A. N. Cambouris, A. J. Messiga, N. Ziadi, I. Perron and C. Morel
      Decimetric-Scale Two-Dimensional Distribution of Soil Phosphorus after 20 Years of Tillage Management and Maintenance Phosphorus Fertilization

      Improving soil test P assessment at plot scale is essential for productivity in conservation agriculture systems. We characterized the distribution of Mehlich-3 P (PM3) concentrations at the decimetric scale with depth on either side of the sowing row in no-till (NT) and moldboard plow (MP) plots fertilized with 35 kg P ha–1 every 2-yr in a corn–soybean rotation (20-yr). A total of 996 soil samples (83 samples × 2 depths [0–5 and 5–20 cm] × 6 plots [3 blocks each MP and NT]) were collected at corn harvest in 2012. The average PM3 concentrations in the 0- to 5-cm layer were 35.7 and 63.4 mg kg–1 in MP and NT, respectively. (continued)

      Core Ideas:
      • 2-D distribution of Mehlich-3 P across seeding row had no spatial pattern in no-till and moldboard plow.
      • Horizontal distribution of Mehlich-3 P was less sensitive to extrinsic factors.
      • Soil-surface P accumulation in no-till is due in part to P recycled by corn and soybean.
      • Surface P accumulation in no-till is also due to the replenishment of solution P by residual P.

      Published: November 2, 2017


    • Bryant C. Scharenbroch, Margaret B. Bialecki and Robert T. Fahey
      Distribution and Factors Controlling Soil Organic Carbon in the Chicago Region, Illinois, USA

      Information on soil organic carbon (SOC) storage and dynamics in urban ecosystems will improve the accuracy of global and regional C budgets, sink and source projections of urban SOC with disturbance and climate change, and soil management for maximization of ecosystem services. Soil organic C (0–100 cm) was measured on 190 (0.04 ha) plots in the seven-county Chicago metropolitan region (14,625 km2) to understand and model SOC distribution across an urban landscape. Most SOC (>75%) was at depths greater than 25 cm and these data suggest that 100 cm may not be deep enough to fully capture SOC in urban ecosystems. Compared to other terrestrial ecosystems (e.g., forests, prairies), SOC across the Chicago region is relatively high (25–75 kg m−2). (continued)

      Core Ideas:
      • The majority (>75%) of soil organic carbon was found at depths greater than 25 cm.
      • Compared to other soils, soil organic carbon in Chicago is relatively high (25–75 kg m-2).
      • Anthropogenic factors were the most important predictors of Chicago soil organic carbon.

      Published: November 16, 2017

    • P.D.S.N. Somarathna, Budiman Minasny and Brendan P. Malone
      More Data or a Better Model? Figuring Out What Matters Most for the Spatial Prediction of Soil Carbon

      Modeling techniques used in digital soil carbon mapping encompass a variety of algorithms to address spatial prediction problems such as spatial non-stationarity, nonlinearity and multi-colinearity. A given study site can inherit one or more such spatial prediction problems, necessitating the use of a combination of statistical learning algorithms to improve the accuracy of predictions. In addition, the training sample size may affect the accuracy of the model predictions. The effect of varying sample size on model accuracy has not been widely studied in pedometrics. (continued)

      Core Ideas:
      • Sample size is the major driving factor of prediction accuracy of soil carbon.
      • The prediction accuracy increases at a decreasing rate with increasing sample sizes.
      • Larger sample sizes deliver equally good prediction accuracy despite the model type.
      • Model type affects the reproducibility (precision) of the predictions.
      • Uncertainty of model predictions decreases with increasing sample sizes.

      Published: November 2, 2017

    • Florian Hirsch, Thomas Raab, William Ouimet, David Dethier, Anna Schneider and Alexandra Raab
      Soils on Historic Charcoal Hearths: Terminology and Chemical Properties

      Historic charcoal hearth remains provide a unique archive of the long-term interaction between biochar, soil development, and plant growth. Charcoal as raw material was crucial for production of iron in iron works, and hence numerous charcoal hearths can be found in the forests near historic iron works in Europe and in the eastern United States. Charcoal hearths are round to elliptical forms often around 10 m in diameter and consist of several-decimeter-thick layers that contain charcoal fragments, ash, and burnt soil. We studied the soil chemistry of 24 charcoal hearths and compared them with the surrounding “natural” soils in the northern Appalachians of northwestern Connecticut. (continued)

      Core Ideas:
      • Charcoal hearth remains are a widespread legacy of historic iron production.
      • Soils on charcoal hearth remains are a carbon sink.
      • Soils on charcoal hearths are classified as Anthropic Udorthents.

      Published: October 19, 2017


    • Matthew W. Farthing and Fred L. Ogden
      Numerical Solution of Richards’ Equation: A Review of Advances and Challenges

      The flow of water in partially saturated porous media is of importance in fields such as hydrology, agriculture, environment and waste management. It is also one of the most complex flows in nature. The Richards’ equation describes the flow of water in an unsaturated porous medium due to the actions of gravity and capillarity neglecting the flow of the non-wetting phase, usually air. Analytical solutions of Richards’ equation exist only for simplified cases, so most practical situations require a numerical solution in one- two- or three-dimensions, depending on the problem and complexity of the flow situation. (continued)

      Core Ideas:
      • The numerical solution of Richards’ equation remains challenging.
      • Space/time discretization affects both computational effort and accuracy.
      • Adaption of space and time discretizations produces benefits.
      • Dissemination of codes and improved documentation are needed.
      • Recent reformulation of one-dimensional Richards’ equation shows promise.

      Published: October 19, 2017


    • R. L. Baumhardt, G. L. Johnson, R. C. Schwartz and D. K. Brauer
      Grazing and Tillage Effects on Soil Properties, Rain Infiltration, and Sediment Transport during Fallow

      Depletion of the High Plains Aquifer that supplies irrigation water for the semiarid Southern Great Plains may necessitate dryland production of crops like wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] using the wheat–sorghum–fallow (WSF) rotation. Reduced crop productivity without irrigation can be offset by intensifying the WSF rotation with cattle (Bos taurus) grazing. Biomass removal and soil trampling without tillage, however, may reduce rain infiltration and storage during fallow that increases with no-tillage (NT) over stubble-mulch (SM) tillage. Our objective was to quantify grazing and tillage effects on infiltration, sediment transport, and aggregate stability during fallow periods after sorghum and wheat. (continued)

      Core Ideas:
      • Soil loss tended higher (>40%) with grazing, but tillage increased soil loss significantly.
      • Infiltration increased with tillage and did not vary with grazing during either fallow phase.
      • Combined grazing and NT management decreased infiltration without tillage to disrupt compaction.

      Published: November 22, 2017

    • Eugenia M. Pena-Yewtukhiw, Emily Leslie Romano, Nicole Lynn Waterland and John H. Grove
      Soil Health Indicators during Transition from Row Crops to Grass–Legume Sod

      Grass–Legume sod inclusion in row crop rotations changes soil health. The transition to a 3-yr orchardgrass (Dactylis glomerata L.) and red clover (Trifolium pratense L.) sod was examined in an existing 7-yr organic rotation with four row crop years: corn (Zea mays L.), soybean (Glycine max L. Merr.), wheat (Triticum aestivum L.), and kale with cowpea (Brassica oleracea and Vigna unguiculata). The study objectives were to determine changes in soil physical health indicators, nutrient stratification, and grass and/or legume biomass during the 3-yr sod growth period, at two composted beef manure rates applied twice in the rotation, prior to corn or wheat establishment. (continued)

      Core Ideas:
      • Transition from organic row crop to 3-yr sod led to significant changes in surface soil health.
      • Changes in soil chemistry were generally subject to a manure × transition time interaction.
      • Manure plus sod are required to increase organic matter in deficient soils.
      • Soil quality and/or health changes with grass sod insertion in a rotation.

      Published: November 22, 2017

    • Ben W. Thomas, Xinlei Gao, Jessica L. Stoeckli, Ryan Beck, Kui Liu, Karen M. Koenig, Brian L. Beres and Xiying Hao
      Nitrapyrin Reduced Nitrous Oxide Emissions from Beef Cattle Urine Patches on a Semiarid Tame Pasture

      Urease and/or nitrification inhibitors applied to urine patches or pastures may increase N retention in the soil–plant system, but how N2O emissions respond to these N stabilizers in semiarid regions is poorly understood. The objectives of this research were (i) to quantify N2O emissions and the associated emission factors, based on the percentage of applied urine-N emitted as N2O–N, from beef cattle urine patches (urine) and (ii) to test the N2O reduction potential of three N stabilizers [2-chloro-6(trichloromethyl) pyridine (nitrapyrin), N-(n-butyl)-thiophosphoric triamide (NBPT), and NBPT plus dicyandiamide (DCD)] on a semiarid tame pasture over two grazing seasons in western Canada. A deionized water control was also included. Nitrapyrin reduced cumulative N2O emissions by 39% and the N2O emission factor by 50% compared with untreated urine in a dry grazing season and reduced cumulative N2O emissions by 58% and the N2O emission factor by 68% compared with untreated urine in a grazing season with normal precipitation. (continued)

      Core Ideas:
      • Limited data are available about mitigating N2O emissions from urine patches on semiarid pasture.
      • Nitrapyrin reduced cumulative N2O emissions by 39% in a dry season.
      • Nitrapyrin reduced cumulative N2O emissions by 58% in normal precipitation season.
      • NBPT and NBPT plus DCD did not limit N2O emissions compared with untreated urine patches.
      • N2O emission factors ranged from 0.03 to 0.21% over two grazing seasons

      Published: November 16, 2017

    • James A. Ippolito, David Bjorneberg, Diane Stott and Doug Karlen
      Soil Quality Improvement through Conversion to Sprinkler Irrigation

      Conversion from furrow to sprinkler irrigation is a recommended conservation practice for improved water-use efficiency (and erosion control), but effects on soil quality indicators are unknown. Several soil quality indicators were therefore quantified within a northwestern United States Conservation Effects Assessment Project (CEAP) watershed after changing from long-term furrow to sprinkler irrigation. Four on-farm sites were identified where producers were growing irrigated barley (Hordecum vulgare L.) using both irrigation practices. Climate, soil type, and management were similar between sites. (continued)

      Core Ideas:
      • Long-term furrow irrigation has caused soil erosional losses.
      • Sprinkler irrigation is considered a water conservation practice.
      • Conversion from furrow to sprinkler irrigation improves soil quality in degraded field areas.

      Published: November 2, 2017

    • Robin L. Brown, Ryan Hangs, Jeff Schoenau and Angela Bedard-Haughn
      Soil Nitrogen and Phosphorus Dynamics and Uptake by Wheat Grown in Drained Prairie Soils under Three Moisture Scenarios

      In semiarid and sub-humid Saskatchewan, Canada, there is growing interest in draining depressional areas within the landscape (prairie potholes) despite a clear understanding of the potential nutrient loss to nearby water sources. Nutrient fate and form can vary greatly depending on soil moisture regime; the aim of this study was to determine how drainage duration affects the nitrogen (N) and phosphorus (P) availability and mobility under varying moisture levels. A greenhouse experiment was conducted using four depressional soils from south-eastern Saskatchewan, which had been drained for 0, 14, 20, and 42 yr, and one undrained midslope soil for comparison. The potted soils were seeded with wheat (Triticum aestivum L.), three different moisture scenarios applied, and leachate was collected weekly. (continued)

      Core Ideas:
      • Nutrient fate and form was investigated in drained soils under various moisture scenarios.
      • Drained soils had greater aboveground biomass and N and P uptake than undrained soils.
      • Mineralization and water holding capacity appeared to affect nutrient losses.

      Published: November 2, 2017

    • Nan Shen, Zhanli Wang, Qingwei Zhang, Bing Wu, Dongdong Wang, Qilin Zhang and Jun’e Liu
      Quantifying the Contribution of Sediment Load to Soil Detachment Rate by Sediment-Laden Rill Flow

      Sediment load changes with downslope distance during rill erosion process, and thus quantifying the potential contribution of sediment load on soil detachment rate is essential to accurately model the rill erosion process. A standardization-based method was adopted to quantify the contribution for the first time, and the rill flume with a soil-feeding hopper was specifically designed to insulate the effect of sediment load on detachment rate. Loessial soil was quantitatively fed into rill flow to produce different sediment loads. Seven flow discharges were combined with six slopes. (continued)

      Core Ideas:
      • A standardization-based method was adopted to quantify the contribution rate.
      • The experiment was specifically designed to isolate the effect of sediment load on detachment rate.
      • The negative contribution of sediment load on detachment rate was almost one-third of the total.
      • This study aimed at rill erosion of loessial soil.

      Published: November 2, 2017

    • Joshua D. Gamble, Gary W. Feyereisen, Sharon K. Papiernik, Chris Wente and John Baker
      Regression-Kriged Soil Organic Carbon Stock Changes in Manured Corn Silage–Alfalfa Production Systems

      Accurate measurement of soil organic C (SOC) stock changes over time is essential to verify management effects on C sequestration. This study quantified spatial and temporal changes in SOC stocks on adjacent 65-ha corn (Zea mays L.) silage–alfalfa (Medicago sativa L.) fields receiving liquid dairy manure in west central Minnesota. We used regression kriging to interpolate SOC in four soil layers in 2006 and 2015, and calculated stock changes over time. Regression kriging with elevation, topographic wetness index, field (west vs. (continued)

      Core Ideas:
      • Regression kriging with elevation, topographic wetness index, field (west vs. east), and irrigation (yes vs. no) accurately predicted soil organic C (SOC) in the 0 to 15- and 15 to 30-cm layers.
      • Lack of spatial structure and a lack of relationships between SOC and auxiliary variables precluded the use of regression kriging for the 30 to 60- and 60 to 90-cm layers.
      • From 0 to 15 cm, SOC in the west field increased by 7% because of gains in irrigated portions of the field, but no changes were found in the east field or from 15 to 30 cm in either field.
      • Simple means indicated SOC gains of 13% in the 30 to 60-cm layer and 24% in the 60 to 90-cm layer across both fields.
      • Typical field management practices associated with large, modern dairies can sequester SOC.

      Published: November 2, 2017

    • Shuo Li, Juan Chen, Jianglan Shi, Xiaohong Tian, Xiushuang Li, Youbing Li and Huili Zhao
      Impact of Straw Return on Soil Carbon Indices, Enzyme Activity, and Grain Production

      Straw return is a promising method for managing soil organic carbon (SOC) in agricultural soils and thus may promote sustainable land use. However, the optimal straw-return strategy for economically sustainable grain production in intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems remains uncertain. A 4-yr field experiment was conducted in the central North China Plain to determine the effects of straw return on SOC stock and lability, soil enzyme activity, and grain yield, and to further evaluate the sustainability of crop production in intensive wheat–maize double-cropping systems. Four treatments were tested: no straw return (NR), return of wheat straw (WR), return of maize straw (MR), and return of both wheat and maize straw (WR+MR). (continued)

      Core Ideas:
      • Straw return could increase SOC stock and improve soil enzyme activities.
      • Both wheat and maize straw returned enlarged SOC stock, soil quality, and crop yield.
      • The single return of crop straw was better for improving the economic sustainability

      Published: October 19, 2017


    • Michael Jenkins, Martin Locke, Krishna Reddy, Daniel S. McChesney and R. Steinriede
      Glyphosate Applications, Glyphosate Resistant Corn, and Tillage on Nitrification Rates and Distribution of Nitrifying Microbial Communities

      We tested the null hypothesis that nitrification and the distribution of archaeal and bacterial nitrifying communities would not be impacted by long-term applications of the herbicide, glyphosate, to glyphosate-resistant (GR) and non-glyphosate-resistant corn (nonGR) under conventional tillage (CT) and reduced tillage (RT) systems. Bulk and rhizosphere soil nitrification potential rates and quantification of amoA genes of archaeal (AOA) and bacterial (AOB) communities were undertaken. In 2013, the nitrification rate of nonGR corn with no glyphosate application treatment associated with bulk and rhizosphere soils under RT displayed greater (P < 0.05) nitrification rates than GR corn with glyphosate applications. In 2014, the nitrification rate of the rhizosphere soil under RT in GR corn with no glyphosate application treatment was greater (P < 0.05) than other rhizosphere soil treatments. (continued)

      Core Ideas:
      • The herbicide glyphosate can affect nitrification rates.
      • Archaeal nitrifiers were dominant in the rhizosphere.
      • In bulk soil, bacterial and archaeal nitrifiers were evenly distributed.

      Published: November 22, 2017


    • Sima Bargrizan, Ronald J. Smernik and Luke M. Mosley
      Development of a Spectrophotometric Method for Determining pH of Soil Extracts and Comparison with Glass Electrode Measurements

      Soil pH measurement using conventional glass electrodes has several limitations. A spectrophotometric method was developed for determining soil pH involving indicator dye (bromocresol purple or phenol red) addition to soil extracts. Results were compared against values determined using a glass electrode for a range of soils (n = 13) with varying properties using different extraction conditions (1:1 w/v soil/water, 1:1 soil/0.01 mol L–1 CaCl2, 1:5 soil/water and 1:5 soil/0.01 mol L–1 CaCl2) and high and low ionic strength buffer calibrations of the electrode. For all extraction conditions, there was a strong relationship (r2 > 0.95, slope ≈ 1) between values of the spectrophotometric (pHspec) and glass electrode (pHelec) methods. (continued)

      Core Ideas:
      • Soil pH is a critical parameter in soils as it influences many biogeochemical processes.
      • There are problems in pH measurements in soils using glass electrodes.
      • A new spectrophotometric method was developed to measure pH in soils.
      • The method compared well to measurements using glass electrodes in a range of soils.
      • A reflectance probe technique was also successfully trialed for in situ measurement.

      Published: November 2, 2017


    • Nina Hacker, Gerd Gleixner, Markus Lange, Wolfgang Wilcke and Yvonne Oelmann
      Phosphorus Release from Mineral Soil by Acid Hydrolysis: Method Development, Kinetics, and Plant Community Composition Effects

      The release kinetics of phosphate (inorganic P [Pi]) at constant proton pressure in a pHstat experiment may be used as a proxy for P mobilization by rhizosphere acidification. pHstat experiments are challenging for calcareous soils because of the strong carbonate buffering. Our objectives were (i) to modify an existing pHstat method for calcareous soils and (ii) to determine plant species richness, plant functional group richness, and identity effects on pool sizes and rate constants (i.e., the fast- and slow-reacting Pools A and B, respectively, and the associated release constants ka and kb). The study was conducted in “The Jena Experiment” comprising grassland mixtures with different functional group composition and species richness. (continued)

      Core Ideas:
      • A modified pHstat approach captures P release kinetics in soil relevant for plant nutrition.
      • The fast-reacting P pool comprises P from charged surfaces and easily soluble Ca-phosphates.
      • The slow-reacting P pool is a mixture of Ca-phosphates and P released by dissolution of pedogenic oxides.
      • Legumes increase the exploitation of more stable P pools.

      Published: November 16, 2017

    • W. L. Pan, L. E. Port, Y. Xiao, A. I. Bary and C. G. Cogger
      Soil Carbon and Nitrogen Fraction Accumulation with Long-Term Biosolids Applications

      Global sustainability depends on the recycling of organic wastes, containing carbon and plant nutrients, back into food production. Biosolids are capable of building total soil organic matter, but their ability to build stable organic C and N fractions is less well understood. The sequestration of stable soil C and replacement of energy-requiring commercial fertilizers both have implications for greenhouse gas mitigation. Our aim was to assess the effectiveness of biosolids amendments to store labile and stable soil C and N fractions while supplying crop N needs. (continued)

      Core Ideas:
      • Biosolids N contribute to wheat grain and soil N.
      • Applied biosolids contain light fraction and non-hydrolyzable C and N.
      • Biosolids C efficiently increased soil C at 0.91 Mg C in soil per Mg C in added biosolids.
      • Buildup of non-hydrolyzable, high C:N light fraction originates in light density biosolids.
      • High total and non-hydrolyzable C retention rates have implications for greenhouse gas mitigation.

      Published: November 2, 2017


    • Feng Gu, Tusheng Ren, Baoguo Li and Lujiu Li
      Accounting for Calcareous Concretions in Calcic Vertisols Improves the Accuracy of Soil Hydraulic Property Estimations

      The soil water retention curve (WRC) is one of the most important properties in soil hydraulic studies. Current studies normally focus on fine soils, ignoring the water-holding capacity of coarse fragments (>2 mm) and their effects on soil available water content (AWC). Calcareous concretions (CC) are coarse inclusions distributed widely in soils around the world. This study was conducted to quantify the effects of the proportion and size of CCs on the soil WRC and AWC of a calcic vertisol. (continued)

      Core Ideas:
      • Calcareous concretions (CCs) could maintain a considerable amount of water and the water content of CCs decreased with an increase in CC sizes.
      • The addition of CCs to soils changed the WRC and the pore distribution of soils significantly.
      • The available water content (AWC) of soil–CC mixtures decreased when the CC content increased.
      • A linear equation, which included CC content and CC water content, was proposed to estimate the AWC of soils containing CCs accurately.

      Published: November 16, 2017

    • Donghao Ma, Jiabao Zhang, Robert Horton, Quanjiu Wang and Jianbin Lai
      Analytical Method to Determine Soil Hydraulic Properties from Vertical Infiltration Experiments

      Soil hydraulic properties are basic inputs for simulating water and solute transport in the vadose zone. Many methods have been developed to directly measure or indirectly estimate soil hydraulic properties. However, low-cost, simple and robust methods are still scarce even in a laboratory. Here we present a new analytical method, based on an approximate solution to the one-dimensional vertical infiltration problem that can be used to determine Brooks–Corey model parameters. (continued)

      Core Ideas:
      • A new method was proposed to determine Brooks-Corey (BC) model parameters.
      • Only a vertical infiltration experiment and simple measurements were required.
      • The new method has great potentials to be applied in situ on various scales.

      Published: November 9, 2017

    • Amanda Ramcharan, Tomislav Hengl, Dylan Beaudette and Skye Wills
      A Soil Bulk Density Pedotransfer Function Based on Machine Learning: A Case Study with the NCSS Soil Characterization Database

      This paper describes a method to develop a soil bulk density pedotransfer function (PTF) using the Random Forest machine-Learning algorithm with soil and environmental data for the conterminous United States. Complete data from 45,818 horizons were extracted from the National Cooperative Soil Survey (NCSS) soil characterization database and used to calibrate and validate the PTF. Environmental data included surficial materials and hierarchical ecosystem land classifications. The results of a five-fold cross-validation showed that the average root mean squared prediction error (RMSPE) was 0.13 g cm–3, and the mean prediction error (MPE) was –0.001 g cm–3. (continued)

      Core Ideas:
      • A soil bulk density pedotransfer function for the conterminous United States.
      • Across a climate gradient, PTF provided bulk densities to estimate SOC stocks.
      • PTF model and the resulting bulk density estimates are available for use under an Open Data license.

      Published: November 9, 2017

    • Hu Zhou, Sacha Jon Mooney and Xinhua Peng
      Bimodal Soil Pore Structure Investigated by a Combined Soil Water Retention Curve and X-Ray Computed Tomography Approach

      Well-structured soils are considered to have bimodal pore structure, including textural pores between particles and structural pores between aggregates. Pore structure can be inferred from the soil water retention curve (SWRC) but our understanding of the 3-D pore geometry that regulates this curve is limited. This study investigated the pore structure of a paddy soil under different fertilization regimes by both SWRC and X-ray micro-computed tomography (micro-CT) imaging with the aim of comparing the two methods. Undisturbed soil aggregates and cores were collected from the surface layer of long-term unfertilized (CK), inorganically fertilized (NPK), and organically and inorganically fertilized (NPKOM) paddy soils. (continued)

      Core Ideas:
      • Soil water retention curves of the paddy soil were bested fitted with bimodal models.
      • Computed-tomography imaging and retention curves generated similar bimodal pore structure.
      • Combined use of organic and inorganic fertilizers increased structural porosity.
      • Textural porosity was not affected by fertilization treatments.

      Published: November 2, 2017

    • A. Markert, K. Bohne, M. Facklam and G. Wessolek
      Pedotransfer Functions of Soil Thermal Conductivity for the Textural Classes Sand, Silt, and Loam

      Data of soil thermal conductivity (λ) covering the whole range of soil water content (θ) are needed in many environmental disciplines. However, laboratory measurements of λ(θ) are time consuming and costly. Therefore the use of pedotransfer functions is promising. In this study, we describe the procedure of deriving such λ(θ) pedotransfer functions for the FAO texture groups (TG) of Sand, Silt and Loam. (continued)

      Core Ideas:
      • The work describes the estimation of soil thermal conductivity (λ) from easily available soil data.
      • Measured high-resolution λ(θ) data were used to improve the accuracy of the model of Lu et al. (2014).
      • Reliable pedotransfer functions estimated soil thermal conductivity of classes Sand, Silt and Loam.
      • Good quality λ data need precise, quantitative measurements and accurate, model-based estimations.

      Published: November 2, 2017


    • Natalie A. Griffiths, Paul J. Hanson, Daniel M. Ricciuto, Colleen M. Iversen, Anna M. Jensen, Avni Malhotra, Karis J. McFarlane, Richard J. Norby, Khachik Sargsyan, Stephen D. Sebestyen, Xiaoying Shi, Anthony P. Walker, Eric J. Ward, Jeffrey M. Warren and David J. Weston
      Temporal and Spatial Variation in Peatland Carbon Cycling and Implications for Interpreting Responses of an Ecosystem-Scale Warming Experiment

      We are conducting a large-scale, long-term climate change response experiment in an ombrotrophic peat bog in Minnesota to evaluate the effects of warming and elevated CO2 on ecosystem processes using empirical and modeling approaches. To better frame future assessments of peatland responses to climate change, we characterized and compared spatial vs. temporal variation in measured C cycle processes and their environmental drivers. We also conducted a sensitivity analysis of a peatland C model to identify how variation in ecosystem parameters contributes to model prediction uncertainty. (continued)

      Core Ideas:
      • We compared spatial vs. temporal variation in C cycle processes and drivers in a bog.
      • The bog was indistinguishable as a C source or sink because of high spatial variation.
      • Sensitive C cycle parameters in the model differed under ambient vs. warming scenarios.
      • Characterizing pretreatment variability is necessary when interpreting warming effects.

      Published: November 22, 2017


    • Danilo J. Romero, Gabriel N. Nóbrega, Xosé L. Otero and Tiago O. Ferreira
      Diffuse Reflectance Spectroscopy (Vis-Nir-Swir) as a Promising Tool for Blue Carbon Quantification in Mangrove Soils: A Case of Study in Tropical Semiarid Climatic Conditions

      The assessment of the soil organic carbon (SOC) stocks in mangrove ecosystems is essential for coastal management activities seeking the mitigation of CO2 emissions. However, the wet chemical analysis conventionally used to quantify SOC may overestimate SOC content due to oxidation of reduced compounds. This work focused on the use of diffuse reflectance spectroscopy (DRS) for predicting SOC in mangrove forest areas. When used properly, DRS may be, in some cases, a more accurate and more efficient method for the determination of SOC in mangrove soils than conventional analytical approaches. (continued)

      Core Ideas:
      • The full-range DRS spectrum (350–2500 nm) generated the best model of prediction.
      • Further DRS studies are necessary to cope with the variability in the mangrove soils.
      • DRS is an effective and fast method for blue carbon stock quantification in mangroves.

      Published: October 19, 2017

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