About the Journal

Soil Science Society of America Journal, the flagship journal of the SSSA, publishes basic and applied soil research in soil chemistry, soil physics, soil pedology, and hydrology in agricultural, forest, wetlands, and urban settings. SSSAJ supports a comprehensive venue for interdisciplinary soil scientists, biogeochemists, and agronomists.

Featured Article

SSAJ Volume 84, Number 2 Cover

2021 SSSA Outstanding Paper: Expanding perspectives of soil nitrification to include ammonia-oxidizing archaea and comammox bacteria

Catalyzed by multiple groups of phylogenetically distinct microorganisms, soil nitrification impacts ground water quality, greenhouse gas emissions, and agricultural practices. This review explores known microbial players involved in nitrification, encompassing aspects of biogeography, phylogenetic diversity, physiology, and activity. Read more


Browse Articles

Molecular orbital study of Fe(II) and Fe(III) complexation with salicylate and citrate ligands: Implications for soil biogeochemistry

  •  9 November 2021

Core Ideas

  • Density functional theory shows to what extent Fe valence affects electron density and atomic charges of the bonded complex.
  • Complexation between Fe and organic acid ligands are through electrostatic forces.
  • Highest occupied natural bond orbitals of Fe complexes is less negative than that of the uncomplexed Fe(II).

Apparent kinetic properties of soil phosphomonoesterase and β‐glucosidase are disparately influenced by pH

  •  2 November 2021

Core Ideas

  • Soil enzyme kinetic properties (Vmax, Km, Ka) may be sensitive to pH.
  • Enzyme Vmax and Km showed strong soil- and enzyme-specific sensitivity to pH.
  • Decoupling of enzyme Vmax and Km means that Ka is not predictable.
  • Enzymological principle of Km sensitivity to pH appears to hold true for soil enzymes.

Biochar restructures plant–soil–microbe relationships in a woody cropping system

  •  2 November 2021

Core Ideas

  • Biochar application increased soil extracellular enzyme activities up to fivefold.
  • Dissolved organic C and soil moisture were increased by biochar.
  • Decreases to N availability suggest biochar induced N immobilization.
  • Biochar led to less diverse root fungal communities and dominance by Wilcoxina.
  • The growth and/or survival of two conifer trees was decreased by biochar.

Open access

Minimum dataset and metadata guidelines for soil‐test correlation and calibration research

  •  2 November 2021

Core Ideas

  • Data sharing is needed for transparent soil-test-based recommendations.
  • A soil-test correlation and calibration minimum dataset provides a data quality standard.
  • A minimum dataset will facilitate meta-analysis for nutrient recommendations.

Open access

A modeling framework to quantify the effects of compaction on soil water retention and infiltration

  •  27 October 2021

Core Ideas

  • We developed novel models for the water retention curve of compacted soils.
  • Measured and predicted soil water retention data were in good agreement.
  • The proposed models may be applied to a wide range of soil types.
  • A 10–20% increase in soil bulk density reduced the soil water storage capacity by 3–49%.
  • A 10–20% increase in soil bulk density reduced cumulative infiltration by 55–82%.

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Evaluation of mehlich‐3 for determination of cation exchange capacity in Kansas soils

Core Ideas

  •  Mehlich-3 extractable K, Mg, and Na were correlated to the standard ammonium acetate counterparts
  •  Mehlich-3 extracted more Ca than ammonium acetate in soils with above neutral pH
  •  Ammonium acetate CEC-summation was correlated with CEC-displacement across a wide range of pH
  •  Mehlich-3 CEC-summation was poorly correlated to CEC-displacement in soils with a pH ≥ 7.3

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A Closed‐form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils

Abstract

A new and relatively simple equation for the soil-water content-pressure head curve, θ(h), is described in this paper. The particular form of the equation enables one to derive closed-form analytical expressions for the relative hydraulic conductivity, Kr, when substituted in the predictive conductivity models of N.T. Burdine or Y. Mualem. The resulting expressions for Kr(h) contain three independent parameters which may be obtained by fitting the proposed soil-water retention model to experimental data. Results obtained with the closed-form analytical expressions based on the Mualem theory are compared with observed hydraulic conductivity data for five soils with a wide range of hydraulic properties. The unsaturated hydraulic conductivity is predicted well in four out of five cases. It is found that a reasonable description of the soil-water retention curve at low water contents is important for an accurated prediction of the unsaturated hydraulic conductivity.

Development of a DTPA Soil Test for Zinc, Iron, Manganese, and Copper

Abstract

A DTPA soil test was developed to identify near-neutral and calcareous soils with insufficient available Zn, Fe, Mn, or Cu for maximum yields of crops. The extractant consists of 0.005M DTPA (diethylenetriaminepentaacetic acid), 0.1M triethanolamine, and 0.01M CaCl2, with a pH of 7.3. The soil test consists of shaking 10 g of air-dry soil with 20 ml of extractant for 2 hours. The leachate is filtered, and Zn, Fe, Mn, and Cu are measured in the filtrate by atomic absorption spectrophotometry.

The soil test successfully separated 77 Colorado soils on the basis of crop response to Zn, Fe, and Mn fertilizers. Critical nutrient levels must be determined separately for each crop using standardized procedures for soil preparation, grinding, and extraction. The critical levels for corn using the procedures reported herein were: 0.8 ppm for Zn, 4.5 ppm for Fe, and tentatively 1.0 ppm for Mn, and 0.2 ppm for Cu.

Development of the soil test was based, in part, on theoretical considerations. The extractant is buffered at pH 7.30 and contains CaCl2 so that equilibrium with CaCO3 is established at a CO2 level about 10 times that of the atmosphere. Thus, the extractant precludes dissolution of CaCO3 and the release of occluded nutrients which are normally not available to plants. DTPA was selected as the chelating agent because it can effectively extract all four micronutrient metals. Factors such as pH, concentration of chelating agent, time of shaking, and temperature of extraction affect the amount of micronutrients extracted and were adjusted for maximum overall effectiveness.

Field‐Scale Variability of Soil Properties in Central Iowa Soils

Abstract

Spatial distributions of soil properties at the field and watershed scale may affect yield potential, hydrologic responses, and transport of herbicides and NO3 to surface or groundwater. Our research describes field-scale distributions and spatial trends for 28 different soil parameters at two sites within a watershed in central Iowa. Two of 27 parameters measured at one site and 10 of 14 parameters measured at the second site were normally distributed. Spatial variability was investigated using semivariograms and the ratio of nugget to total semivariance, expressed as a percentage, was used to classify spatial dependence. A ratio of <25% indicated strong spatial dependence, between 25 and 75% indicated moderate spatial dependence, and >75% indicated weak spatial dependence. Twelve parameters at Site one, including organic C, total N, pH, and macroaggregation, and four parameters at Site two, including organic C and total N, were strongly spatially dependent. Six parameters at Site one, including biomass C and N, bulk density, and denitrification, and 9 parameters at Site two, including biomass C and N and bulk density, were moderately spatially dependent. Three parameters at Site one, including NO3 N and ergosterol, and one parameter at Site two, mineral-associated N, were weakly spatially dependent. Distributions of exchangeable Ca and Mg at Site one were not spatially dependent. Spatial distributions for some soil properties were similar for both field sites. We will be able to exploit these similarities to improve our ability to extrapolate information taken from one field to other fields within similar landscapes.

Soil Water Characteristic Estimates by Texture and Organic Matter for Hydrologic Solutions

Abstract

Hydrologic analyses often involve the evaluation of soil water infiltration, conductivity, storage, and plant-water relationships. To define the hydrologic soil water effects requires estimating soil water characteristics for water potential and hydraulic conductivity using soil variables such as texture, organic matter (OM), and structure. Field or laboratory measurements are difficult, costly, and often impractical for many hydrologic analyses. Statistical correlations between soil texture, soil water potential, and hydraulic conductivity can provide estimates sufficiently accurate for many analyses and decisions. This study developed new soil water characteristic equations from the currently available USDA soil database using only the readily available variables of soil texture and OM. These equations are similar to those previously reported by Saxton et al. but include more variables and application range. They were combined with previously reported relationships for tensions and conductivities and the effects of density, gravel, and salinity to form a comprehensive predictive system of soil water characteristics for agricultural water management and hydrologic analyses. Verification was performed using independent data sets for a wide range of soil textures. The predictive system was programmed for a graphical computerized model to provide easy application and rapid solutions and is available at http://hydrolab.arsusda.gov/soilwater/Index.htm

Black Carbon Increases Cation Exchange Capacity in Soils

Abstract

Black Carbon (BC) may significantly affect nutrient retention and play a key role in a wide range of biogeochemical processes in soils, especially for nutrient cycling. Anthrosols from the Brazilian Amazon (ages between 600 and 8700 yr BP) with high contents of biomass-derived BC had greater potential cation exchange capacity (CEC measured at pH 7) per unit organic C than adjacent soils with low BC contents. Synchrotron-based near edge X-ray absorption fine structure (NEXAFS) spectroscopy coupled with scanning transmission X-ray microscopy (STXM) techniques explained the source of the higher surface charge of BC compared with non-BC by mapping cross-sectional areas of BC particles with diameters of 10 to 50 μm for C forms. The largest cross-sectional areas consisted of highly aromatic or only slightly oxidized organic C most likely originating from the BC itself with a characteristic peak at 286.1 eV, which could not be found in humic substance extracts, bacteria or fungi. Oxidation significantly increased from the core of BC particles to their surfaces as shown by the ratio of carboxyl-C/aromatic-C. Spotted and non-continuous distribution patterns of highly oxidized C functional groups with distinctly different chemical signatures on BC particle surfaces (peak shift at 286.1 eV to a higher energy of 286.7 eV) indicated that non-BC may be adsorbed on the surfaces of BC particles creating highly oxidized surface. As a consequence of both oxidation of the BC particles themselves and adsorption of organic matter to BC surfaces, the charge density (potential CEC per unit surface area) was greater in BC-rich Anthrosols than adjacent soils. Additionally, a high specific surface area was attributable to the presence of BC, which may contribute to the high CEC found in soils that are rich in BC.

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