Showing papers in "Soil Science in 2014"

Biochar effects on soil aggregate properties under no-till maize

Abstract: Soil aggregates are useful indicators of soil structure and stability, and the impact on physical and mechanical aggregate properties is critical for the sustainable use of organic amendments in agricultural soil. In this work, we evaluated the short-term soil quality effects of applying biochar (0–10 kg m−2), in combination with swine manure (2.1 and 4.2 kg m−2), to a no-till maize (Zea mays L.) cropping system on a sandy loam soil in Denmark. Topsoil (0–20 cm) aggregates were analyzed for clay dispersibility, aggregate stability, tensile strength (TS), and specific rupture energy (SRE) using end-over-end shaking, a Yoder-type wet-sieving method, and an unconfined compression test in soil samples collected 7 and 19 months after final biochar application. The highest rates of biochar and swine manure application resulted in the highest aggregate stability and lowest clay dispersibility. Applying both amendments systematically increased TS and SRE for large aggregates (4–8 and 8–16 mm) but not for small aggregates (1–2 and 2–4 mm). Increased biochar application also decreased the friability index of soil aggregates. Based on X-ray visualization, it was found that aggregates containing larger amounts of biochar particles had higher TS and SRE probably because of bonding effects. Based on the improved soil aggregate properties, we suggest that biochar can be effective for increasing and sustaining overall soil quality, for example, related to minimizing the soil erosion potential.

Consecutive biochar application alters soil enzyme activities in the winter wheat-growing season

Abstract: Soil enzymes catalyze key biochemical processes in organic matter decomposition and nutrients cycles and are regarded as indicators of soil quality. In this study, we investigated the impact of 4 consecutive years of biochar (corncob; 360°C) amendment on dynamics of enzyme activities (i.e., invertase, urease, catalase, and alkaline phosphatase) during the winter wheat (Triticum aestivum L.) growing period in Northern China. The experiment consisted of four treatments: control (CK), biochar rate at 4.5 t · ha · y (B4.5), biochar rate at 9.0 t · ha· y (B9.0), and crop straw return (SR). Four times throughout the wheat growth period (i.e., 5 Nov. 2010; 26 Mar. 2011; 25 Apr. 2011; 5 Jun. 2011), we determined the enzyme activities down to the 30-cm depth of the soil profile (i.e., 0–5, 5–10, 10–20, and 20–30 cm). Results showed that there were considerable fluctuations in enzyme activities across the observed period and depths. All enzyme activities decreased significantly in deeper soil horizons. High biochar amendment rates (B9.0) lead to the peak activities of invertase, urease, and phosphatase occurring in the 0- to 5-cm layer on 25 Apr. 2011 samples. The greatest catalase activity under B9.0 was found on 26 Mar. 2011 samples. In addition, the effect by B4.5 and SR on enzyme activities was variable and limited. These data support the conclusion that consecutive application of biochar for 4 years increased enzyme activities, which potentially influence soil nutrients dynamics under field condition, although the effects were dependent on sampling depth and time.

Soil salinity measurement via portable X-ray fluorescence spectrometry

Abstract: Saline soils are defined as those containing appreciable salts more soluble than gypsum (e.g., various combinations of Na, Mg, Ca, K, Cl, SO4, HCO3, and CO3). Saline soils can occur across diverse climates and geological settings. As such, salinity is not germane to specific soil textures or parent materials. Traditional methods of measuring soil salinity (e.g., electrical conductance), although accurate, provide limited data and require laboratory analysis. Given the success of previous studies using portable X-ray fluorescence (PXRF) as a tool for measuring soil characteristics, this study evaluated its applicability for soil salinity determination. Portable X-ray fluorescence offers accurate quantifiable data that can be produced rapidly, in situ, and with minimal sample preparation. For this study, 122 surface soil samples (0–15 cm) were collected from salt-impacted soils of coastal Louisiana. Soil samples were subjected to standard soil characterization, including particle size analysis, loss-on-ignition organic matter, electrical conductivity (EC), and elemental quantification via PXRF. Simple and multiple linear regression models were developed to correlate elemental concentrations and auxiliary input parameters (simple: Cl; multiple: Cl, S, K, Ca, sand, clay, and organic matter) to EC results. In doing so, logarithmic transformation was used to normalize the variables to obtain a normal distribution for the error term (residual, ei). Although both models resulted in similar acceptable r between soil EC and elemental data produced by PXRF (0.83 and 0.90, respectively), multiple linear regression is recommended. In summary, PXRF has the ability to predict soil EC with reasonable accuracy from elemental data.

Coadaptation of Plants to Multiple Stresses in Acidic Soils

Abstract: Abstract Soil acidification is an increasing problem in agricultural production and ecological stability worldwide. An understanding of the mechanisms by which plants adapt to acidic soils would help address this problem. Poor plant growth in acidic soils results from a variety of factors, including proton toxicity; deficiencies in nitrogen, phosphorus, calcium, magnesium; and toxicities of various metals (aluminum (Al), manganese, iron). Aluminum toxicity is generally the primary limitation for plant growth in acidic soils. Although much research has focused on Al toxicity in recent decades, it is rarely the only limiting factor in acidic soils. The occurrence of Al toxicity depends on many other factors that coexist with Al in acidic soils. The interactions between Al and such factors are important determinants of Al toxicity to plants under field conditions. In this review, therefore, instead of focusing only on mechanisms of Al tolerance, we examine the effects of the interactions between Al and other limiting factors on plant adaptation to acidic soils. We summarize research on the interactions between Al and nitrogen, phosphorus, pH, and iron. Accordingly, three strategies are proposed to improve plant growth in acidic soils: a combined application of lime and nutrients, depending on the types of soils and plants; development of plant varieties tolerant to multiple stresses; and inoculation of plants with certain beneficial microbes. This review emphasizes the ability of plants to coadapt to multiple stresses in acidic soils.

Cultivar and Previous Crop Effects on Methane Emissions From Drill-Seeded, Delayed-Flood Rice Production on a Silt-Loam Soil

Abstract: The effects of cultural practices on drill-seeded delayed-flood rice (Oryza sativa L.) production on methane (CH4) emissions are not well quantified. In Arkansas, rice is produced predominantly on loamy soils following soybean (Glycine max L.) as the previous crop, and hybrid rice has replaced a large percentage of pure-line cultivars in the past decade. Therefore, research was conducted during the 2012 growing season to assess the effects of previous crop (rice or soybean) and cultivar (standard-stature, semi-dwarf, and hybrid) on CH4 emissions on a silt-loam soil. A 30-cm-diameter chamber-based method was used to determine fluxes during the 2012 growing season. When soybean was the previous crop, fluxes were generally lower (P < 0.05) until heading, after which all fluxes decreased until flood release. Seasonal emissions differed based on previous crop and cultivar (P < 0.05). Area- and yield-scaled growing season emissions from rice following soybean were less (127 kg CH4-C ha; 13.7 kg CH4-C (mg grain)) than when rice followed rice (184 kg CH4-C ha; 20.5 kg CH4-C (mg grain)). Hybrid rice emitted less (111 kg CH4-C ha; 11.1 kg CH4-C (mg grain)) than semi-dwarf (169 CH4-C ha; 18.3 kg CH4-C (mg grain)) or standard-stature rice (186 kg CH4-C ha; 21.9 kg CH4-C (mg grain)), which did not differ. Thus, results indicated decreased emissions when soybean was the previous crop and when the hybrid cultivar was grown. The incorporation of factors known to influence CH4 emissions (i.e., previous crop, cultivar, and yield) will improve estimates of the carbon footprint of rice.

Impacts of 1.5-Year Field Aging on Biochar, Humic Acid, and Water Treatment Residual Amended Soil

Abstract: While biochar research has progressed, there is relatively little field-scale data over time, which constrains our understandings of biochar’s “true” effects on soil quality and our ability to make appropriate recommendations to users, especially in comparison to other amendments. Thus, this study compares 2 successive years’ field-scale soil data with biochar and other amendments added to a scalped silty clay loam soil at an application rate of 0.5%. None of the amendments significantly affected any of the measured soil physicochemical properties and greenhouse gas emissions even after 1.5 years of field aging. However, some of the measured soil properties were significantly changed after the second year compared with those of the first year. On temporal scale, soil electrical conductivity and penetration resistance significantly increased under most treated soils, and soil available water capacity significantly increased only under biochar. Although no differences in soil properties were detected, there was a trend toward higher corn dry grain and biomass yields under biochar compared with those of the control. Biochar was able to reduce N2O emissions from soil, only in the first year, whereas gaseous emissions were not different from control in the rest of the experiment. Thus, the findings of this study suggest that the improvements in soil fertility due to biochar amendment were not because of changes in most of the observed physical properties of the soil, but some other effects (changes in microbial community or nutrient additions) may have controlled the crop yield. In addition, these data demonstrate that selected amendment application rate of 0.5% (wt/wt) was not sufficient to cause significant changes in most observed physical properties beyond 1.5 years of field aging, suggesting additional research using higher rate of application.

Quantification of SOC and Clay Content Using Visible Near-Infrared Reflectance–Mid-Infrared Reflectance Spectroscopy With Jack-Knifing Partial Least Squares Regression

Abstract: A total of 125 soil samples were collected from a Danish field varying in soil texture from sandy to loamy. Visible near-infrared reflectance (Vis-NIR) and mid-infrared reflectance (MIR) spectroscopy combined with chemometric methods were used to predict soil organic carbon (SOC) and clay contents. The main objective of this study was to find the best model for predicting SOC and clay content in the sampled field using Vis-NIR, MIR, and the combination of Vis-NIR and MIR and using different model development techniques. The secondary objectives were (i) to use iterations of calculation to find the optimal number of replicates for MIR measurements based on the root mean square error of cross validation (RMSECV) and (ii) to apply partial least squares regression in combination with jack-knifing (JK) to identify the most important part of spectral variables and the best model for predicting SOC and clay content. The study showed that with repeated MIR measurements it was possible to improve RMSECV by 20%. The optimal number of repeated MIR measurements was between 3 and 4 for SOC and clay content. Comparing all the prediction results, the combination of MIR and Vis-NIR with the partial least squares regression–JK technique resulted in the lowest prediction errors (RMSECVsoc of 0.35% and RMSECVclay of 1.05%). The average uncertainties of laboratory measurements were 0.39% and 1.86% for SOC and clay contents, respectively. All models had acceptable and—to a large extent—comparable margins of error. Partial least squares regression with JK simplified and enhanced the interpretation of the developed models because of a reduction in the number of variables used in the models.

Change in Peat Coverage in Danish Cultivated Soils During the Past 35 Years

Abstract: Mapping the spatial and temporal changes of peatland in farming systems is crucial to the study of soil quality and productivity and the modeling of the global carbon cycle (in relation to climate change). This study compiles a contemporary map (2010) of peatland coverage (according to Kyoto protocol) across the cultivated wetlands of Denmark and compares this actual map to a historical 1975 peat coverage map using simple indicator kriging. For the contemporary peatland mapping, extensive soil sampling databases consisting of 42,568 points with 32,817 historical samples and 9,751 contemporary samples were used. These databases contain partly categorical information on parent material (organic [peat, gytje] and mineral [sand, silt and clay]) and partly continuous data (soil organic carbon, in %) reclassified into organic and mineral soils (using 12% soil organic carbon as a cutoff value). In the simple indicator kriging procedure, the values 0 and 1 were assigned to the stationary means of the indicator codes to represent two hypotheses, that is, mineral and organic (peat) soils, respectively. The collected and analyzed contemporary unbiased organic samples (measured on different rectangular grid scales of 250, 275, and 500 m) in addition to some transformed historical organic samples (according to certain decision rules) were used to estimate the recent areal coverage of peat (2010) that was equivalent to 70,176 ha, and this estimate corresponds to an indicator kriging probability of 0.35. Results revealed there has been a total areal coverage loss of 35% (37,786 ha) of the Danish organic cultivated wetlands during a period of 35 years (map 1975 had 107,962-ha coverage of peat). The peat depletion is related to peat mining and agricultural drainage/tillage activities, rather than natural geological processes.

Effects of Rainstorm Patterns on Runoff and Sediment Yield Processes

Abstract: Varying rainfall intensity during rainfall events is a common phenomenon, but little information is available concerning its effects on soil erosion processes. Five simulated rainstorm patterns (even, rising, falling, rising-falling, and falling-rising patterns), each with a different rainfa

Utility and limitations of portable x-ray fluorescence and field laboratory conditions on the geochemical analysis of soils and floors at areas of known human activities.

Abstract: Portable x-ray fluorescence (pXRF) technology can be implemented in soil geochemical analysis for faster and more efficient testing of trace metals in soils. The level of soil phosphorus (P) is one of the major indicators of human activities related to food distribution, preparation, and was

Adsorption-Desorption of Myo-Inositol Hexakisphosphate on Hematite

Abstract: Adsorption, desorption, and precipitation reactions at environmental interfaces impact the bioavailability, mobility, and fate of organic phosphates in terrestrial and aquatic environments. Myo-inositol hexakisphosphate (IHP) is the most abundant organic phosphate in soils. The adsorption/desorption characteristics of IHP on/from hematite were studied using batch adsorption and desorption experiments, Zeta (ζ) potential measurement, and in situ attenuated total reflectance Fourier transform infrared spectroscopy. The experiments were also conducted with phosphate (Pi) for comparison. Adsorption of both IHP and Pi has an initial rapid uptake followed by a slow adsorption process. The adsorbed amounts of IHP and Pi on hematite were 0.67 and 1.78 μmol m at pH 5, respectively, decreasing with increasing pH. At all pH levels between 3 and 10, the surface of IHP adsorbed hematite was highly negative charged, leading to increasing IHP adsorption with ion strength. The desorption of IHP/Pi decreased sharply with the increasing desorption cycle and decreasing preadsorption amount. The desorption curves of IHP/Pi by 0.02 mol L KCl or H2O can be well fitted by an exponential equation, whereas those for citrate followed a linear equation. Readsorption occurred in the later stage of Pi desorption by H2O, which was not observed in case of IHP probably because of the greater steric hindrance of IHP with the larger molecular size. In combination with adsorption-desorption characteristics, ζ potential measurements, and attenuated total reflectance Fourier transform infrared spectroscopy analysis, it is suggested that each adsorbed IHP molecule binds on hematite in the form of inner-sphere surface complexes via two phosphate groups.

Modeling Selenate Adsorption Behavior on Oxides, Clay Minerals, and Soils Using the Triple Layer Model

Abstract: Abstract Selenate adsorption behavior was investigated on amorphous aluminum oxide; amorphous iron oxide; clay minerals kaolinites, montmorillonites, and illite; and 18 soil samples from Hawaii and the Southwestern and Midwestern regions of the United States as a function of solution pH. Selenate adsorption decreased with increasing solution pH. The triple layer model, a chemical surface complexation model, was able to describe Se(VI) adsorption as a function of solution pH by simultaneously optimizing either two outer-sphere Se(VI) surface complexation constants or one inner-sphere and one outer-sphere Se(VI) surface complexation constant. The fit of the triple layer model to Se(VI) adsorption by oxides, clay minerals, and soils was excellent, as evidenced by very low values of the model variance goodness-of-fit criterion. The predominantly outer-sphere Se(VI) surface speciation predicted using the triple layer model was in agreement with the weak adsorption behavior previously observed for Se(VI) using electrophoretic mobility measurements and ionic strength dependence of adsorption. Direct spectroscopic investigations of Se(VI) surface configurations are needed to corroborate the species predicted by the triple layer modeling approach.

Calculating particle density, bulk density, and total porosity of soil based on its texture

Abstract: Abstract This paper provides the verification of coefficients for the calculation of particle density, bulk density, and total porosity based on the texture of soils proposed by Brogowski (1990). The verified and supplemented coefficients for the calculation of particle density, bulk density, and total porosity permit obtaining credible results within the range of analytical errors. The proposed calculations of density and total porosity of soils can be used for the general description of soils. They cannot, however, replace exact scientific research on the physical state of soils.

Soil-Aggregating Bacterial Community as Affected by Irrigation, Tillage, and Cropping System in the Northern Great Plains

Abstract: Little is known about the microbial community structure associated with soil aggregation in microaggregates (0.25–0.05 mm) that are held within macroaggregates (>0.25 mm). We investigated the effects of irrigation, tillage, and cropping system on aggregate distribution and the community stru

Long-term Residue Management Effects on Soil Respiration in a Wheat-Soybean Double-Crop System

Abstract: One of the most significant contributors to the greenhouse effect is carbon dioxide (CO2) gas in the atmosphere. Soil respiration, the combined production of CO2 from soil, as a result of root and microorganism respiration, is the largest flux of CO2 from the terrestrial ecosystem to the atm

Continuous Wheat in Semiarid Regions: Long-term Effects on Stock and Quality of Soil Organic Carbon

Abstract: Continuous wheat (Triticum aestivum L.) cropping in semiarid regions results in variable dry matter production. As a consequence, the balance of soil organic carbon (SOC) may vary across time. The aim of this research was to assess the dynamics and long-term changes of physically and chemically extracted SOC fractions. Soil samples (0- to 5-, 5- to 10-, and 10- to 20-cm depths) from continuous wheat with (f) and without (nf) fertilizer (N + P) under conventional tillage ((CT) for 25 years) and no-tillage ((NT) for 6 years) were taken during the experiment. Mineral-associated ((MOC) 0–0.053 mm), fine particulate ((POCf) 0.053–0.100 mm), and coarse particulate ((POCc) 0.1–2.0 mm) SOC and humic substances were obtained. The SOC variability depended on water availability during fallow periods (SOC decomposition) or crop cycles (dry matter production). The mean wheat yields were 1.33 (nf) and 2.09 (f) Mg grain ha, with an estimated carbon input of 1.64 (nf) and 2.20 (f) Mg C ha year. Losses from the initial level were higher in labile fractions, POCc (−75%) and POCf (−53%), than in MOC (−15%). Humic acids present slight differences in their structure and quantity as a result of long-term cropping. Conversion from CT to NT resulted in contrasting results. For an equivalent soil mass, fertilizer application increased SOC by 4.31 Mg ha (under CT) and 7.29 Mg ha (under NT). The SOC turned out to be higher under NT with fertilizer use and lower without application. No-tillage does not increase SOC content by itself; it must be combined with other agricultural practices such as fertilization and/or crop rotation.

Iron Reduction Coupled to Reductive Dechlorination in Red Soil: A Review

Abstract: Iron reduction plays an important role in the reductive transformation of organochlorine pesticides in red paddy soils. This interaction between iron reduction and organochlorine pesticides (OCPs) in red soils in south China is particularly important because of the high abundance and reactivity of iron within unique man-made paddy ecosystems. However, the relationships between iron reduction and reductive dechlorination and the geochemical constraints of these relationships are not fully understood. In this comprehensive review, we summarized current understanding of iron reduction, reductive dechlorination, the relationships between them, and their interactions with the reduction of nitrate, sulfate, Cu(II), and humic substances in red soils. Recent studies showed that iron reduction and dechlorination occur simultaneously in soils and that iron reduction could either stimulate or inhibit dechlorination. Meanwhile, sulfate and Cu(II) reduction can stimulate or inhibit iron reduction and dechlorination. Nitrate reduction can be coupled to iron reduction, but it inhibits dechlorination. Increasing evidence showed that humic substances can enhance the rates of both iron reduction and dechlorination by accelerating electron transfer. However, there is insufficient information in the literature for delineating the effects of several rising environmental problems (e.g., heavy metal pollution, deficiencies in phosphorus and aluminum) on iron reduction, OCP transformation, and the related microbial activities. Future studies are necessary because such information may be key for sustainable development of agriculture and pollution control in red soils.

Effects of Poultry Litter Injection on Ammonia Volatilization, Nitrogen Availability, and Nutrient Losses in Runoff

Abstract: Abstract Poultry litter is a common organic amendment in agricultural production, but nutrient losses can reduce its effectiveness as a fertilizer. Three experiments were conducted to evaluate ammonia nitrogen (NH3-N) volatilization, N availability, and runoff losses of nutrients by conducting a closed chamber volatilization study, a soil incubation, and a rainfall simulation. In all studies, poultry litter was applied at a rate of 6.7 Mg · ha−1 either on the surface or injected and compared with an unamended control. In the volatilization and soil incubation studies, Braddock Loam and Bojac Sandy Loam surface soils were compared. Of the ammonium N added, cumulative loss of NH3-N by volatilization was 3% from injected and 121% from surface applied poultry litter after 7 days in the Loam. In the Sandy Loam, cumulative loss of NH3-N was 9% from injected and 153% from surface applied poultry litter after 7 days. After a 40-day soil incubation, injection increased total inorganic N by 52% and 99% for the Loam and Sandy Loam soils, respectively, when compared with surface application. Injection reduced total Kjeldahl N by 59%, total Kjeldahl P by 53%, dissolved reactive P, dissolved nitrate N by 73%, and dissolved NH3-N in runoff by 99%, compared with surface application. Injection reduced NH3-N volatilization and nutrients in runoff to levels of the control. These studies show that injection increases plant available N while decreasing losses through volatilization and runoff.

Measurements of Texture of Soils Formed from Glaciolimnic Sediments by Areometric Method, Pipette Method and Laser Diffraction Method

Abstract: Abstract The aim of the research was to compare the results of texture analyses of glaciolimnic sediments deposited in the basins of ice-dammed lakes origin in north eastern Poland. The study was carried out using aerometric method, pipette method and laser diffraction method. The studied soils were classified as Haplic and Mollic Vertisol, Vertic Cambisol, and Gleyic Chernozem. The soils were formed from clayey (clay, heavy clay), loamy (loam, clay loam, sand clay loam) and silty (silt loam, clay loam) deposits. The studied soils did not contain fractions > 2.0 mm. The amounts of clay fraction (< 0.002 mm) measured by areometric and pipette methods were similar and strongly correlated. In comparison to laser diffraction method, these amounts were 3-4-fold higher. The sub-fraction of fine silt (0.02-0.002 mm) predominated in soil formations analyzed by laser diffraction method. In comparison to areometric or pipette method, the amounts of fine silt were 2-4 fold higher. Basing on the calculated sedimentological indices, it was stated that the examined soils were well sorted and the mean grain diameter (GSS) was very low and did not exceed 0.005 mm in areometric and pipette methods, and 0.011 mm in laser diffraction method for clay sediments.

Coarse Fragments Affect Soil Properties in a Mantled-Karst Landscape of the Ozark Highlands

Abstract: Abstract The Ozark Highlands region of the mid-southern United States is characterized in many areas by thin stony soils overlying highly fractured and dissolution-prone carbonate bedrock that are highly susceptible to groundwater contamination. The objective of this study was to evaluate the effect of coarse fragments on soil physical and hydraulic properties within a typical mantled-karst landscape in northwest Arkansas. In 2002, three representative soil series (i.e., Clarksville, Captina, and Razort) that vary taxonomically in coarse fragment content were selected for investigation. The alluvial Razort soil had the largest coarse fragment content, ranging between 15% in the top 10 cm and 80% in the 90- to 100-cm depth, which strongly affected the soil’s hydraulic properties. With increasing coarse fragment contents with depth (P < 0.05) in all three soils, total bulk density increased with depth to approximately 1,400 kg m−3, whereas the soil bulk density markedly decreased to less than 500 kg m−3 across all three soils in the 90- to 100-cm depth. Ponded infiltration measurements, which did not differ among the three soils, demonstrated that coarse fragments reduced the vertical one-dimensional volume available for water flow, increased the tortuosity, and reduced the hydraulic conductivity of the soil pore system. However, ponded intake measurements demonstrated that the soil surface properties of the alluvial soil generated greater two-dimensional water flow below the land surface once infiltration occurred. Transmissivity was roughly 35 times greater in the alluvial Razort compared with the residual Captina and Clarksville soils, resulting in greater estimated saturated hydraulic conductivity at the surface for the alluvial soil. The combination of results from this study shows that careful consideration of the coarse fragment content of the soil is necessary when managing land use in mantled-karst landscapes.

Phosphorus Fractions of Red Soils in Guangdong Province of South China and Their Bioavailability for Five Crop Species

Abstract: Red soil, the main soil type in south China, has many limitations for crop production, especially low phosphorus (P) bioavailability. Currently, little is understood concerning P fractions and their bioavailability for crops. In the present study, P fractions were analyzed from 50 red soil samples collected from regions leading agricultural production in Guangdong Province of south China. The most abundant P forms were iron-bound P (Fe-P) and organic P (Org-P), which, combined, account for 64.4% ± 1.9% of total soil P. Both Org-P and Fe-P had less bioavailability for soybean in sand culture than the other sparingly soluble P forms tested, with growth reduced by 78.0% ± 4.2% or 35.4% ± 6.7% and P content reduced by 50.2% ± 8.4% or 68.7% ± 1.8% when P was supplied as Org-P or Fe-P, respectively, compared with plants supplied with KH2PO4. Further field experiment using five crop species showed that P bioavailability in red soils is very low, as reflected by an average of 53.9% ± 2.9% loss in shoot P content for all tested crops in soils without P fertilization compared with plots amended with P fertilizer. After evaluation of root-to-shoot ratio and specific root length, along with rhizosphere P depletion and acidification, it is reasonable to speculate that different crop species have evolved various strategies to overcome P deficiency in red soils. Among the tested crops, rapeseed displayed more rhizosphere acidification and lower carbon cost for maintaining root growth and subsequently possessed a superior ability to use and activate P from red soils than the other four crops.

Influence of human activities on the soils of Debrecen, Hungary

Abstract: Abstract Soil profiles of the city centre of Debrecen were investigated in order to examine their properties and investigate the vertical distribution of heavy metals as a measure the anthropogenic activity. During the laboratory work the basic soil features were identified (texture, artefact content, pH, CaCO3, and amounts of organic matter). Furthermore, contents of Pb, Zn, Cu and Co in the soils were measured. Most of the metals showed a strong positive correlation with the humus content and the silt fraction. The soils of the city centre are exposed to a significant anthropogenic effect, therefore the original soil morphologies are usually difficult to identify. The soil profiles are greatly disturbed, which is traceable in the vertical distribution of certain soil features and metal contents.

Laboratory Methods for the Estimation of Soil Apparent N Mineralization and Wheat N Uptake in Calcareous Soils

Abstract: Estimating soil N mineralization is important for determining the amount of N fertilizer needed to obtain optimum yields at minimal environmental and economic costs. The aim of this work was to determine the most appropriate laboratory method for the estimation of N mineralization during a winter wheat-growing season in calcareous soils under a humid Mediterranean climate. Laboratory methods were developed involving three chemical extractants, CaCl2, KCl, and NaHCO3, and several soil-drying and extraction temperatures. Soil N indexes calculated based on extractions were compared with potentially mineralizable N (No). Moreover, soil mineralization indexes estimated from both chemical extractions and aerobic incubation were related to apparent N mineralization and wheat N uptake in a pot experiment. The mineralization index estimated from an extraction with KCl boiled at 100°C (HotKCl) was the index that best correlated with No and the apparent mineralization under greenhouse conditions. The combination of preplant soil mineral N and the HotKCl N mineralization index was more strongly correlated with wheat N uptake than soil mineral N data alone. Consequently, estimation of N mineralization using HotKCl extraction is the most appropriate methodology for establishing N fertilizer use recommendations for wheat cultivation in calcareous soils under Mediterranean conditions.

Long-Term Effects of Biosolid-Amended Soils on Phosphorus, Copper, Manganese, and Zinc Uptake by Wheat

Abstract: Abstract Biosolids have long been applied to agricultural land as fertilizer, and concerns exist regarding the long-term environmental impact of residual P and metals in biosolid-amended fields. Objectives of this study were to determine (i) P solubility in three soils from Maryland, Minnesota, and Illinois with histories of biosolid application and (ii) uptake of P, Cu, Mn, and Zn by wheat (Triticum aestivum L.) grown on these amended soils. In a pot study, wheat was grown on three soils that had received applications of biosolids 16 to 24 years before soil collection. Mehlich-3–extractable P increased by as much as 246%, 350%, and 274% for the amended Maryland, Minnesota, and Illinois soils, respectively, compared with control values. Mehlich-3–extractable Cu and Zn concentrations also increased with biosolid application for the three soils, whereas Mn decreased or did not change. Wheat biomass yield was reduced by 78% for the Maryland soil amended with lime-composted biosolids, accompanied by a decline of wheat tissue Mn concentration of 86%. Tissue P concentration increased by as much as 237%, 141%, and 304% for the amended Maryland, Minnesota, and Illinois soils, respectively. This study demonstrated that, regardless of soil or biosolid source, soils that had received biosolids 16 to 24 years earlier retained elevated levels of phytoavailable P and Zn, resulting in elevated levels of those elements in wheat. Although biosolids are beneficial for crop production, the risk of long-term negative effects of excess P and metal on the environment should be considered before application.

Field Testing a Mobile Inelastic Neutron Scattering System to Measure Soil Carbon

Abstract: Cropping history in conjunction with soil management prac- tices can have a major impact on the amount of organic carbon stored in soil.Currentmethodsofassessingsoilcarbonbasedonsoilcoringandsub- sequent processing procedures before laboratory analysis are labor inten- sive and time-consuming. Development of alternative methods that can make in situ field measurements of soil carbon is needed to successfully evaluatemanagementpracticesinatimelymanner.Therobustdesign,field testing procedure, and results of measuring soil carbon in situ using a mo- bile inelasticneutron scattering (MINS) system are described. A method of MINS spectra data processing that gives more accurate peak area determi- nation compared with the traditional "trapezoidal" method is described. The MINS reliable autonomous operation for 29 h per charge cycle was demonstrated in the field. For comparison, soil cores were also collected for laboratory carbon analysis using the dry combustion technique. Soil carbon assessments by dry combustion technique and MINS demonstrated a linear correlation between the two methods in the 0- to 30-cm soil layer.

Stabilization of Organic Carbon via Chemical Interactions with Fe and Al Oxides in Gley Soils

Abstract: The importance of soil organic carbon (SOC) stabilization via chemical interactions with Fe and Al oxide minerals within gley soils remains unclear. Changes in the proportions of Fe/Al oxides and SOC and N contents associated with Fe/Al oxides within the profiles of gley soils under contrasting hydrological regimes and freely draining control soils from Harwood Forest (northeast England) were investigated. Sequential selective dissolution techniques were used to measure Fe/Al oxide crystallinity and explore whether crystallinity differed between gleyed and freely draining soils. Extracts were analyzed using Fourier transform infrared spectroscopy to investigate the chemical characteristics of organic matter (OM) associated with Fe/Al oxides. Strongly crystalline Fe oxides were the dominant (∼50%–80% of total Fe oxides present) mineral phase in gley mineral soils. Contrasting gley soil hydrological regimes influenced total subsoil Fe and total and weakly crystalline Al oxide concentrations. Also, within-profile changes in strongly crystalline Fe oxide concentrations were linked to differences in hydrological and redox conditions. A large proportion of SOC (generally 70%–90% of total) seemed to be associated with Fe/Al oxides. Correlation plots, however, indicated that SOC contents were not linearly related to amounts of total Fe and Al oxides, weakly crystalline Fe and Al oxides, or strongly crystalline Fe oxides. The lack of linear correlations observed for these acidic soils may be caused by contributions from other extractable soil components and factors such as high organic loadings and insufficient amounts of Fe/Al oxides for interaction with SOC in topsoils and variable surface loadings of different organic inputs at different soil depths. Subsoil C/N ratios (∼18–21) were higher than those in extracted subsoil residues (∼9–17), suggesting that minerals other than Fe/Al oxides preferentially adsorbed N-rich microbially processed compounds. The OM associated with weakly and strongly crystalline Fe/Al oxides was chemically different, the latter generally having greater hydroxyl, aliphatic, carboxylate, and /or phenolic character and less carbohydrate character than the former. This research shows that interactions between Fe/Al oxides and SOM in redox-dynamic gley soils under different hydrological regimes are complex, and further investigations of SOC stabilization in these systems using selective dissolution and other complementary techniques are required.

Hydraulic and Physiochemical Properties of a Hillslope Soil Assemblage in the Ozark Highlands

Abstract: Abstract Heterogeneity of infiltration and subsurface redistribution of soil water can have a profound influence on plant growth and productivity as well as water quality. However, substantial uncertainty exists in assessing hydrologic impacts over multiple scales confounded by multiple adjacent land uses. Spatial variabilities of soil surface hydraulic properties are key elements in understanding vadose zone hydrodynamics. The objective of this investigation was to evaluate the effects of land use, soil series, and microtopographic position on soil surface physiochemical and hydraulic properties (i.e., ponded and tension infiltration) during the transition from fall to winter seasons during a period of shallow aquifer recharge. Measurements were made across three Fragiudults (Captina, Nixa, and Johnsburg soil series) on a young alley-cropped agroforestry tract and an adjacent cattle-grazed pasture that constitute a headwater hillslope soil assemblage in the Ozark Highlands. Ponded and tension infiltration rates were affected (P < 0.05) by soils, microtopographic positions, and/or land uses. Tension infiltration rates, averaged across soils and land uses at a pressure head of -3 cm, were nearly twofold greater at the microtopographic low position (17.8 mm h−1) than the high (9.2 mm h−1) position, where the microtopographic high position in the landscape was generally a shallower soil than that at the microtopographic low position. However, when all infiltration measurements were evaluated together, no significant differences in infiltration dynamics were observed among soils, microtopographic positions, or land uses. Thus, a single infiltration pressure head function effectively characterized the hillslope soil assemblage evaluated in this study when shallow aquifer recharge was occurring. Greater bioporosity in upland grazed pastures may serve to naturally decrease hydraulic property variability across soils, which may simplify, rather than complicate, hydrologic partitioning between infiltration and runoff in grassland-based agroecosystems receiving frequent applications of animal manures in the Ozark Highlands.

Anthropogenic transformation of soils in the Barycz valley – conclusions for soil classification / Antropogeniczne przekształcenia gleb w Dolinie Baryczy - wnioski dotyczące klasyfikacji gleb

Abstract: Abstract Large-scale river regulation, drainage and intense farming in the Barycz valley initiated in 17th century activated a transformation of the initial alluvial and swamp-alluvial soils. Soils on the Holocene flooded terraces have deep, acid humus horizons (umbric) and gleyic properties at shallow depth, but have no stratification of parent material to a depth of 100 cm. Despite the location in the floodplain, soils cannot be classified as black-earth alluvial soils (mady czarnoziemne) using the criteria of Polish soil classification (2011). The soils on the Pleistocene non-flooded terraces have a deep, base-saturated humus horizon (mollic) and gleyic properties in the lower part of soil profile, which allows to classify them as the black earths (czarne ziemie). Prominent stratification of the parent material well preserved in these soils has no influence on their classification (due to the age sediments). Almost all humus horizons of these soils meet the definition of anthric characteristics, and more than half of the studied soils can be classified as culturozemic soils - rigosols - which emphasises the important role of man in the transformation and gaining of morphological features of these soils. The lack of precise criteria for identifying soil types in the chernozemic order of the Polish soil classification (2011) causes difficulties in the classification of soils on the river terraces, in particular, in distinguishing between black-earth alluvial soils and black earths. Streszczenie Wielkoskalowa regulacja, odwodnienia oraz intensywne rolnicze zagospodarowanie doliny Baryczy zainicjowane w XVII wieku uruchomiły transformację pierwotnych gleb aluwialnych i błotno-aluwialnych. Gleby na holoceńskich terasach zale- wowych mają głęboki, kwraśny poziom próchmczny (umbric) i są płytko oglejone, a do głębokości 100 cm nie zaznacza się stratyfi- kacja materiału macierzystego} Mimo położenia na terenach zalewowych, gleb tych me można zaliczyć do mad czamoziemnych posługując się kryteriami Systematyki gleb Polski (2011). Gleby na plejstoceńskich terasach nadzalewowych mają głęboki, wysyco- ny zasadami poziom prócliniczny (mollic) i oglejenie w dolnej części profilu, co przybliża je do czarnych ziem. Dobrze widoczna stratyfikacja materiału macierzystego nie ma w tych glebach znaczenia klasyfikacyjnego ze względu na wiek osadów'. Niemal wszyst- kie poziomy próchmczne spełniają kryteria poziomu anthric, a ponad pokwa badanych gleb może być zaliczona do gleb kulturo- ziemnych - ngosoli, co podkreśla istotną rolę człowieka w transformacji i kształtowaniu cech morfologicznych tych gleb. Brak precyzyjnych kryteriów identyfikacji typów' w rzędzie gleb czamoziemnych w Systematyce gleb Polski (2011) powoduje trudności w klasyfikacji gleb na terasach rzecznych, a wr szczególności rozgraniczanie między madami czamoziemnymi oraz czarnymi ziemiami.

Validation of SWEEP for Contrasting Agricultural Land Use Types in the Tarim Basin

Abstract: The Tarim Basin is a major source of windblown dust in China. Land management and use can greatly impact windblown dust, thus, models such as the Wind Erosion Prediction System (WEPS) are important for identifying management practices that reduce the emission of dust. The objective of this study was to test the performance of the WEPS erosion submodel (the Single-event Wind Erosion Evaluation Program (SWEEP)) under contrasting agricultural land use types in the Tarim Basin of northwest China. Wind erosion of a sandy soil was measured and simulated in a cotton (Gossypium hirsutum L.) field and red date (Ziziphus jujuba L.) orchard during the spring of 2012 and 2013. The SWEEP did not simulate differences in soil loss for contrasting agricultural land use types, although measured soil loss was typically smaller than that considered to be of consequence (>100 g m) in the original design of the SWEEP. In fact, the model simulated no erosion for all six high wind events in which we observed erosion in the cotton field and red date orchard. The insensitivity of SWEEP to simulate erosion was caused by the simulated friction velocity being consistently lower than the threshold friction velocity for the loess soil at the cotton field and red date orchard. Because SWEEP is being used to assess wind erodibility of lands and simulate regional air quality in China, SWEEP must be improved for application to lands that emit large and small amounts of windblown dust.