Soil Water Extraction Research Articles

Historical charcoal additions alter water extractable, particulate and bulk soil C composition and stabilization

AbstractThe objective of this work was to investigate the chemical composition and the quantitative changes in soil organic matter (SOM) fractions in response to multiple historical inputs of charcoal that ceased > 60 years ago. The topsoil (0–5 cm) and subsoil (5–20 cm) samples of charcoal enriched soils and the unamended reference soils were assessed for C and N contents in bulk soil, particulate organic matter (POM) fractions and water extractable organic matter (WEOM). The SOM molecular characteristics were investigated in the solid phase by nuclear magnetic resonance (NMR) and in the WEOM by Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). Formerly added charcoal additions reduced the extracted amount of WEOM and altered POM pattern: an increased proportion of C and N stored in coarse, intermediate, and fine POM relative to corresponding total C and N was found in subsoils. In contrast, C and N stored in the residual fraction (< 20 µm) decreased. NMR results revealed a higher aromaticity of SOM in charcoal enriched soils, while the FT‐ICR‐MS results indicated an increased presence of lignin‐ and tannin‐like compounds in the WEOM of these soils. Former charcoal additions enhanced soils capacity to retain and stabilize C and N. Particularly, the presence of charcoal particles elevated C and N stored in large POM fractions > 20 µm, which presumably increases soil porosity and thus the soils' capacity to retain water.

Impact of soil organic matter on calcium carbonate equilibrium and forms of Pb in water extracts from Kastanozem complex

Accounting for ionic strength and ion association, the degree of calculated supersaturation with CaCO3 of gleyic solonetz and molic solonetz soil solution is high. The purpose of the research was to reveal the effect of the water-dissolved organic matter (DOM) on the calcium carbonate equilibrium (CCE) in soil solution, to create a thermodynamic model of carbonate association and complexation with DOM and heavy metals (HMs), and to correct the principal of soil management. Object of research—Kastanozem complex of the dry steppe, Rostov Oblast, Russia. The water extraction of soluble salts was made at the water-to soil-ratio 5:1 and analyzed using standard methods. DOM content was determined by Strosser (J Agrobiol 27:49–60, 2010). The soil solution macro-ion equilibrium composition was calculated using ION-2 program (Endovitsky et al. 2009). DOM role in soil solution supersaturation with СаСО3 was assessed, comparing C content in real solution and in identical artificial solution prepared without organic matter. Taking into account the ion association, the molar fractions of free and bound HM ion were calculated using microelement association coefficient, kas(ME). The soil liquid-phase saturation with CaCO3 was characterized by the ratio of the real solubility product (S) to the thermodynamic solubility product (S0): К = S/S0. The soil solution supersaturation with CaCO3 was characterized by the product of analytical concentrations (S), equilibrium concentrations [accounting ion activity (SI), ion association (SII), ion association and complexation (SIII)], and the thermodynamic solubility product (S0). To evaluate the role of DOM in soil solution supersaturation with CaCO3, the initial pure Ca (HCO3)2 solution series was prepared. The humic and fulvic acids from the illuvial horizon of gleyic solonetz with concentrations of 20 mg C L−1 and 120 mg C L−1 decreased the CaCO3 precipitation compared with initial soil solution. The release of CaCO3 from soil water extracts containing water-soluble organic matter was 1.2–1.9 times less compared with identical artificial solution not containing organic matter. The HM binding by carbonates is proportional to the DOM content. In molic solonetz and gleyic solonetz, the neutralization of the soda should be assessed by the soil solution supersaturation with CaCO3. To calculate the degree of HM passivation in soil solution containing DOM, the coefficient of soil solution oversaturation with CaCO3 is proposed. For reducing soil organic matter and DOM mobility and loss from soil, as well as for Pb passivation, intra-soil mechanical processing, intra-soil waste management, and intra-soil watering are proposed.

Infrared spectroscopy estimation methods for water-dissolved carbon and amino sugars in diverse Canadian agricultural soils

Infrared spectroscopy has the potential to rapidly analyse soil water-dissolved carbon and amino sugars. In this study, mid-infrared (MIR) and near-infrared (NIR) spectra collected from soil water extracts or from bulk soils were analysed with partial least squares regression (PLSr) to estimate the concentrations of water-dissolved carbon and amino sugars in diverse agricultural soils collected from five field sites in two western and two eastern Canadian provinces. The MIR-PLSr models developed from soil water extract spectra estimated hot-water (100 °C) dissolved carbon (HWDC) [R2 = 0.97–0.70, ratio of prediction to deviation (RPDp) = 6.13–1.83] well, but the MIR-PLSr models did not estimate cold-water (21 °C) dissolved carbon (CWDC) well (R2 = 0.82–0.50, RPDp = 2.35–1.42). The model estimates of HWDC at the multisite scale (all samples together) and for the two western Canada sites (R2 = 0.97–0.93, RPDp = 6.13–3.68) surpass the modal estimates for the three eastern Canadian sites (R2 = 0.81–0.70, RPDp = 2.28–1.83). The MIR- and NIR-PLSr models derived from bulk soil spectra both estimated HWDC well at the multisite scale (R2 = 0.91–0.88, RPDp = 3.32–2.90) and for the western Canada sites (R2 = 0.90–0.87, RPDp = 3.18–2.96). Models developed from hot-water extract spectra and bulk soil spectra resulted in poor estimates of soil amino sugars (R2 = 0.74–0.21, RPDp = 1.99–1.12), except for the approximate quantitative estimation of muramic acid by models based on soil spectra at the western and the multisite scale (R2 = 0.82–0.80, RPDp = 2.33–2.21). We concluded that MIR and NIR models at regional and multisite scales can be used as a tool to monitor HWDC but that additional research is required for estimating soil amino sugars.

Sensitivity analysis of the AquaCrop parameters for rainfed corn in the South of Brazil

Abstract: The objective of this work was to perform a sensitivity analysis of the main input parameters required for the AquaCrop water balance model, using biomass and grain yield data of a rainfed-simulated corn crop, obtained along the climate data series of 1987-2016 in the South of Brazil. The levels of soil-water stress and the depths of maximum effective rooting were the input parameters that most affected the biomass and grain yields simulated by the model, followed by the crop coefficient, water-use efficiency, soil water storage capacity, and contribution of groundwater to water availability in the root zone. The parameters crop cycle duration, plant density, pattern of soil-water extraction, and field surface practices showed little or no impact on the final results. AquaCrop is a robust water balance model, with small or moderate general sensitivity to variations of the main input parameter values, which makes it applicable to situations with field data limitations.

Yield of canola (Brassica napus L.) benefits more from elevated CO2 when access to deeper soil water is improved

This study investigated the interactive effects of atmospheric CO2 concentration ([CO2]) and water availability on yield, root growth and water use of two canola cultivars with contrasting growth and vigour (vigorous hybrid cv. Hyola 50 and non-hybrid cv. Thumper). Plants were grown under ambient [CO2] (a[CO2], ∼400 μmol mol−1) or elevated [CO2] (e[CO2], ∼700 μmol mol−1) in a glasshouse. Two water treatments (well-watered and drought) were established in each [CO2] treatment. During the growing season leaf gas exchange parameters were measured. Leaf area was measured at 80 days after sowing. Aboveground biomass, seed yield, yield components and root biomass in four different soil layers (Layer 1: 0–20 cm, Layer 2: 21–40 cm, Layer 3: 41–60 cm and Layer 4: 61–80 cm depth) were measured at maturity. Weekly water use was determined gravimetrically.Elevated [CO2] stimulated seed yield (38%), aboveground biomass (34%), root biomass (42%), leaf area (42%) and leaf biomass (41%). Whilst e[CO2] stimulated root biomass in all soil layers, this stimulation was greater in the deeper than upper soil layers, and was associated with greater extraction of deeper soil water under e[CO2]. The cultivar with greater stimulation of deeper root biomass under e[CO2] showed greater yield benefit from the ‘CO2 fertilisation effect’. Under well-watered conditions, e[CO2]-induced reductions of stomatal conductance (gs) balanced the effect of increased leaf area on water use, resulting in similar water use compared to a[CO2]. In contrast, under drought conditions, water use was greater under e[CO2] than a[CO2]. The ‘CO2 fertilisation effect’ depended on cultivar and water treatment. Under well-watered conditions, aboveground biomass of the hybrid cultivar benefitted more from the ‘CO2 fertilisation effect’. However, under drought both aboveground biomass and seed yield of the non-hybrid cultivar benefitted more from the ‘CO2 fertilisation effect’. These findings show that interactions between environmental conditions (here experimental water treatments) and expression of genotypic traits (here differences between cultivars) play a decisive role in determining potential yield and growth benefits from rising [CO2].

Distribution and phytotoxicity of soil labile aluminum fractions and aluminum species in soil water extracts and their effects on tall fescue

Soil acidification can alter the biogeochemistry of ecosystems and adversely affect biota; however, there are still many debates about the toxicity of aluminum (Al) fractions and Al species in soil:water extracts to plants. In this study, five crude soils with different pH values (4.92–8.51) were collected, seeded with tall fescue and grown in rhizosphere boxes for 120 days. Then, soil properties, labile Al fractions and Al species in soil:water extracts were determined, and their toxicities to plants were analyzed. Our study showed that a stable exchangeable Al fraction (ExAl) pool exists and is supplied by other labile Al fractions. Dissolution of Al from adsorbed hydroxyl-Al fraction (HyAl) and organic-Al fraction (OrAl) may play important roles in soil Al toxicity, as HyAl and OrAl account for major parts of soil labile Al. Additionally, Al3+ and mononuclear hydroxyl-Al species in soil:water extracts have few effects to plants. Nevertheless, high negative correlations were found between Al-F- complexes and tall fescue biomass, indicating their toxicity in the natural soil environment. Thus, in many cases, Al3+ toxicity should not be emphasized because of its lower activity in soil water extracts. Moreover, toxicities of AlF3(aq) and AlF4- to plants should be emphasized, because they have been confirmed in soil water extracts in this study.

Inter-laboratory comparison of cryogenic water extraction systems for stable isotope analysis of soil water

Abstract. For more than two decades, research groups in hydrology, ecology, soil science, and biogeochemistry have performed cryogenic water extractions (CWEs) for the analysis of δ2H and δ18O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soil water isotope composition. Here we present results from the first worldwide round robin laboratory intercomparison. We test the null hypothesis that, with identical soils, standards, extraction protocols, and isotope analyses, cryogenic extractions across all laboratories are identical. Two standard soils with different physicochemical characteristics along with deionized (DI) reference water of known isotopic composition were shipped to 16 participating laboratories. Participants oven-dried and rewetted the soils to 8 and 20 % gravimetric water content (WC), using the deionized reference water. One batch of soil samples was extracted via predefined extraction conditions (time, temperature, and vacuum) identical to all laboratories; the second batch was extracted via conditions considered routine in the respective laboratory. All extracted water samples were analyzed for δ18O and δ2H by the lead laboratory (Global Institute for Water Security, GIWS, Saskatoon, Canada) using both a laser and an isotope ratio mass spectrometer (OA-ICOS and IRMS, respectively). We rejected the null hypothesis. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to soil type and soil water content with mean differences compared to the reference water ranging from +18.1 to −108.4 ‰ for δ2H and +11.8 to −14.9 ‰ for δ18O across all laboratories. In addition, differences were observed between OA-ICOS and IRMS isotope data. These were related to spectral interferences during OA-ICOS analysis that are especially problematic for the clayey loam soils used. While the types of cryogenic extraction lab construction varied from manifold systems to single chambers, no clear trends between system construction, applied extraction conditions, and extraction results were found. Rather, observed differences in the isotope data were influenced by interactions between multiple factors (soil type and properties, soil water content, system setup, extraction efficiency, extraction system leaks, and each lab's internal accuracy). Our results question the usefulness of cryogenic extraction as a standard for water extraction since results are not comparable across laboratories. This suggests that defining any sort of standard extraction procedure applicable across laboratories is challenging. Laboratories might have to establish calibration functions for their specific extraction system for each natural soil type, individually.

Short-term effects of organo-mineral enriched biochar fertiliser on ginger yield and nutrient cycling

Biochar has agronomic potential but currently is too expensive for widespread adoption. New methodologies are emerging to reduce the cost such as enriching biochar with nutrients that match crops and soil requirements. However, the effects of biochar-based fertilisers on plant yield and soil nutrient availability have not been widely examined. This study investigated the effects of a novel organo-mineral biochar fertiliser in comparison to organic and commercial biochar fertiliser on ginger (Zingiber officinale Canton). There were four treatments: (1) commercial organic fertiliser (5 t ha−1), as the control; (2) commercial biochar-based fertiliser (5 t ha−1); (3) organo-mineral biochar fertiliser at low rate (3 t ha−1); and (4) organo-mineral biochar fertiliser at high rate (7.5 t ha−1). A replicated pot trial was established with black dermosol soil and ten replicate pots for each treatment. Ginger was planted and grown for 30 weeks. Plant growth, biomass, foliar nutrients and water extractable soil nutrients including phosphorus (P), potassium (K) and calcium (Ca) were examined. High rate organo-mineral biochar fertiliser increased soil P and K availability at week 30 (harvest) after planting, compared to all other treatments and low rate organo-mineral biochar fertiliser performed similarly to the organic control for P and K. High rate organo-mineral biochar fertiliser increased total foliar nutrient content at week 30 in P, K and Ca compared to commercial biochar fertiliser. High rate organo-mineral biochar fertiliser improved the commercial value of ginger (+ 36%) due to a shift in the proportion of higher grade rhizomes. Low rate organo-mineral biochar fertiliser plants displayed similar yield, total dry and aboveground biomass to commercial organic fertiliser. Commercial biochar fertiliser had significantly lower biomass measures compared with other treatments as the rate applied had lower nutrient concentrations. Our results show organo-mineral biochar fertilisers could be substituted for commercial organic fertilisers at low rates to maintain similar yield or applied at high rates to increase commercial value where economically feasible.

Methodological Approaches toward Chemico-Biological Diagnostics of the State of Soils in Technogenically Transformed Territories

The comprehensive diagnostics of the state of soils in the impact zone of thermal power station (TPS-5) in the city of Kirov was performed on the basis of the soil chemical analyses and the study of biota response to the loads at different organization levels. The chemical analyses attested to a satisfactory state of the soils. However, the use of soil cyanobacteria and bird’s-foot trefoil (Lotus corniculatus) as test objects showed the toxicity of studied soil samples. The toxicity of the samples was judged from the bioindication effects of cyanophytization and melanization of soil microbial complexes. The obtained results demonstrated that at relatively low concentrations of total and mobile heavy metal compounds in the soil samples, their amount released into the tested soil water (1: 4) extract exceeded the limit allowable for normal functioning of living organisms. For the first time, the express cyanobacterial tetrazole-topographic method of biotesting was applied in the geoecological study to estimate the toxicity of the soil samples. The results obtained with the help of traditional and express methods proved to be comparable. The express-method was sufficiently sensitive and efficient. It allowed the determination of the samples' toxicity in five hours, i.e., four to five times faster than the traditional technique. An inverse relationship between the number of viable cells of cyanobacteria (as judged from the inclusion of formazan crystals) and the concentration of lead ions in the tested soil extracts was found. This finding can be considered a prerequisite for further study and application of the express method in the practice of geoecological monitoring. Our study demonstrated the necessity of a comprehensive approach for the assessment of the real ecological state of soils in the investigated impact zone of the thermal power station.

Effects of climate on distribution of soil secondary minerals in volcanic regions of Tanzania

In the volcanic regions of Tanzania, including Mt. Kilimanjaro, Mt. Meru, and Mt. Kieyo, soils are formed on relatively recent tephra deposits (<0.45 Ma). Because of the diversity of climate caused by the volcanic terrain in these regions and different parent material compositions, various soil secondary minerals were expected to form. The objectives of this study were to determine the distribution of secondary minerals in soils formed on tephras in the volcanic regions of Tanzania and to estimate the effects of climate and parent material composition on the distribution of secondary minerals. A total of 30 soil samples from the B-horizon from different parent materials and under different climatic conditions (540–2800 m altitude) were collected. The soils were classified into five groups depending on location and considering the total elemental contents. Selective extraction methods, X-ray diffraction, and differential thermal analyses were applied to determine the composition of the secondary minerals. The composition of the soil water extract was determined to assess the stability of the minerals. Excess precipitation (EP), as an index to evaluate the soil water regime, was calculated by subtracting potential evapotranspiration from precipitation. The soils in Mt. Kilimanjaro and Mt. Meru were rich in Fe or Mg, whereas soils in Mt. Kieyo were rich in Si, indicating mafic and felsic parent materials, respectively. At the low moisture sites (EP < 500 mm), Alo + 1/2Feo (the sum of acid oxalate soluble Al and Fe) were low and increased with EP. Meanwhile, the values of Alo + 1/2Feo negatively correlated with mean average temperature (MAT) for all sites. At low moisture sites, low EP would be favorable for the crystallization of nanocrystalline Al and Fe. At the sites with sufficient moisture, the temperature was the primary factor controlling the distribution of nanocrystalline minerals. Furthermore, gibbsite was found at the sites with high EP (EP > 500 mm) with low H4SiO40 activities. More kaolinite was detected at the low elevation sites with high H4SiO40 activities in soil solutions. Soil moisture and temperature are critical factors influencing the distribution of secondary minerals, whereas parent material compositions have less effect on soils in the volcanic regions of Tanzania.

A simple greenhouse experiment to explore the effect of cryogenic water extraction for tracing plant source water

AbstractStable isotopes of water (2H and 18O) are useful tracers for determining root water uptake depths. In such studies, plant and soil water are extracted most commonly by cryogenic vacuum distillation. However, recent studies have suggested that cryogenic extraction conditions (extraction time, temperature, and vacuum) and soil physicochemical properties affect the isotopic composition of extracted soil water. Here, we perform a simple greenhouse trial with 2 plant species (Taraxacum officinale and Pelargonium spp.) in 2 soil types (clayey loam and sand) to test our ability to match plant water to its putative soil water source(s) by using different extraction conditions (30–240 min, 80–200 °C, 0.1 Pa). We irrigated plants with water of known isotopic composition, sampled root crowns and soils at 2 depths, and varied the cryogenic water extraction conditions.Our isotope results from the sandy soils were unaffected by cryogenic extraction conditions. In contrast, extraction parameters affected the isotope composition of waters recovered from clayey soil. This influenced the estimates of plant water sourcing, where δ2H and δ18O returned different results from each other. With higher extraction temperatures and longer extraction times, we gradually extracted more enriched soil water, which reflected the source water of both plant species. Our results imply that longer extraction times and temperatures for clayey soils are needed to reduce fractionation effects during the extraction procedure. Future studies should explore how these effects apply to natural clay‐rich soils as well as plant tissue isotope composition.

Modeling soil water flow and quantification of root water extraction from different soil layers under multi-chemicals application in dry land field

The combined application of different functional chemicals creates challenges both in modeling water flow in soil and quantification of water extraction by crops in dry land farming. In the present study, 2-year laboratory and field experiments were conducted in a typical dry land of northern China in order to: (i) develop a model to describe patterns of water flow in soil under two typical chemicals Superabsorbent polymer (SAP) and Fulvic acid (FA) combined applied in the soil-maize system and (ii) use the stable hydrogen and oxygen analysis method to further quantify the soil water extraction by crops as affected by SAP and FA. Two root water extraction (RWE) terms based on density of root length (DRL) and density of root nitrogen mass (DRNM), respectively, were established to describe the rate of RWE, demonstrating that the values simulated from DRNM were verified to be closer to measured values. A particular model was further developed to simulate flow of water in different soil layers, and its authenticity was confirmed for describing the patterns of soil water flow under multi-chemicals application. The results of hydrogen and oxygen isotope abundance estimated from multi-source mass balance method (IsoSource model) suggested that main depth of water extraction as affected by multi-chemicals decreased first and then increased, and mainly concentrated in the shallow soil layers, 0–20 cm soil layer for jointing stage, 20–40 cm soil layer for heading stage, 0–20 cm soil layer for grain filling stage. Combined application of SAP and FA played a synergistic role in promoting the rainfall WUE of maize.

Nitrogen management in crop rotations after the break-up of grassland: Insights from modelling

Currently there is a shift from grassland based forage production towards maize systems in the Low Countries of north-west Europe. Breaking-up grassland and turning it into arable fields is associated with high nitrate leaching. Crop models can help to identify cropping strategies to reduce nitrate leaching by performing long-term simulation experiments. This study aimed: (i) to evaluate the crop model APSIM against field trial data, in particular nitrogen (N) balance components N-uptake, leaching and soil mineral N, and (ii) conduct a simulation experiment for assessing suitable management practices over a long period using historical records (1980–2015).Evaluation data consisted of two rotation types over two years (maize-maize and barley-mustard-maize) with two nitrogen (N) fertilizer schemes (zero and standard fertilizer: 160 for maize and 120 kg N/ha for barley) after the break-up of grassland. Experiments were carried out at three different sites with contrasting soils in north-west Germany. Results showed that APSIM was capable of simulating the crop rotations and fertilizer applications satisfactorily: Total biomass (n = 21) was reproduced with a root mean square error (RMSE) of 1139 kg/ha against an observed mean of 9915 kg/ha across crops. Total N uptake (n = 21) was simulated well with a RMSE of 22 kg/ha (against observed mean 144 kg/ha). Simulated soil mineral N in the top 0–30 cm (n = 253) and 0–90 cm (n = 33) showed a high index of agreement (IA) of 0.90 and 0.86, respectively. Comparisons observed vs simulated over time confirmed that APSIM was able to capture the N dynamics in the soil. Extractable soil water was also modelled well. Leached nitrate (n = 16) was simulated with a RMSE of 50 kg N/ha, whereby APSIM captured the high nitrate losses of up to 240 kg N/ha/winter period caused by the high mineralization and the fertilization. In the long-term the simulation experiment showed that fertilization of maize did not result in additional biomass, but in higher leaching losses. Mustard was effective in reducing nitrate leaching but is difficult to implement in practice. Finally, the study demonstrated that crop modelling complements conventional analysis very well in identifying environmentally sound and profitable management practices for complex situations in soil-crop systems such as grassland break-up.

Soil Water Extraction Monitored Per Plot Across a Field Experiment Using Repeated Electromagnetic Induction Surveys

Soil water (θ) dynamics are important parameters to monitor in any field-based drought research. Although apparent electrical conductivity (ECa) measured by electromagnetic (EM) induction has been used to estimate θ, little research has shown its successful application at the plot-scale for evaluating crop water use. An EM38 conductivity meter was used to collect time-lapse ECa data at the plot scale across a field cropped with 36 different chickpea genotypes. An empirical multiple linear regression model was established to predict θ measured by neutron probes and depth-specific electrical conductivity (σ) generated by a 1-D EM inversion algorithm. Soil water dynamics and movement were successfully mapped with a coefficient of determination (R2) of 0.87 and root-mean-square-error of 0.037 m3 m−3. The rate of soil drying varied with depth and was influenced by chickpea growth stages and genotypes. The results were also used to evaluate the differences in soil water use and rooting depths within- and across-plant species and during the growth stages. Coupled with physiology measurements, the approach can also be used to identify mechanisms of drought tolerance in the field and screening for effective water use in crop breeding programs.

Effects of vegetation types on water-extracted soil organic matter (WSOM) from riparian wetland and its impacts on riverine water quality: Implications for riparian wetland management

Riparian wetlands play important roles in the enhancement of water quality by controlling nonpoint source pollution and protecting aquatic ecosystems. In the present study, we surveyed and identified vegetation types in riparian wetlands, evaluated how vegetation types influence spatial patterns of water-extracted soil organic matter (WSOM) from riparian wetland, and probed the impacts of riparian fluorescent WSOM on fluorescent dissolved organic matter (FDOM) and water trophic states in river ecosystems. We used absorption and excitation-emission-matrix (EEM) fluorescence spectroscopy to characterize the optical properties of riparian WSOM and riverine DOM from Chongming Island, China, the largest alluvial plain island in the world. Our results showed that fifty-eight spermatophytes in riparian wetland were clustered into five vegetation types, including warm coniferous forest (WCF), deciduous broad leaf forest (DBF), evergreen broad leaf forest (EBF), aquatic plants (AP) and herbaceous plants (HP). Absorption spectra revealed the effects of vegetation types on riparian chromophoric WSOM quantity. Although no difference in water-extracted soil organic carbon (WSOC) contents was observed, deciduous broad leaf forest (DBF) and evergreen broad leaf forest (EBF) fed more fluorescent WSOM quantity than did the other vegetation (AP, HP and WCF), and deciduous broad leaf forest (DBF) and aquatic plants (AP) provided more humic-like (RC.1 and RC.2) and fulvic-like (RC.3) substances into riparian wetland (P<0.05 or P<0.01). In addition, we noted that humic-like and protein-like substances (RC.4) transported from riparian wetland into a river water body, and riverine terrestrial-originated components (FC.1 and FC.2) were significantly related to the four riparian fluorescent WSOM components (P<0.05). Furthermore, the riverine trophic state was significantly higher when the fluvial DOM and its component quantity increased (P<0.05). We concluded that riparian wetland can control the quantity and quality of riparian WSOM and reshaped riverine DOM compositions and riverine water quality with important management implications.

Comparison of pore water samplers and cryogenic distillation under laboratory and field conditions for soil water stable isotope analysis

ABSTRACTWe used pore water samplers (PWS) to sample for isotope analysis (1) only water, (2) soil under laboratory conditions, and (3) soil in the field comparing the results with cryogenic extraction (CE). In (1) and (2), no significant differences between source and water extracted with PWS were detected with a mean absolute difference (MAD) always lower than 2 ‰ for δ2H and 1 ‰ for δ18O. In (2), CE water was more enriched than PWS-extracted water, with a MAD respect to source water of roughly 8 ‰ for δ2H and 4 ‰ for δ18O. In (3), PWS water was enriched relative to CE water by 3 ‰ for δ2H and 0.9 ‰ for δ18O. The latter result may be due to the distinct water portions sampled by the two methods. Large pores, easily sampled by PWS, likely retain recent, and enriched, summer precipitation while small pores, only sampled by CE, possibly retain isotopically depleted water from previous winter precipitation or irrigation inputs. Accuracy and precision were greater for PWS relative to CE. PWS is therefore suggested as viable tool to extract soil water for stable isotope analysis, particularly for soils used in this study (sandy and silty loams).

Comparative Ameliorative Efficiency of Phosphogypsum and Elemental Sulfur in Semi-Terrestrial Soda and Sulfate Moderately Halophytic Solonetz of the Light Gray Earth Subzone

The article presents the data from field tests on determination of the relative ameliorative efficiency of equivalent dosages of phosphogypsum and elemental sulfur on the alkaline saline semi-terrestrialsolonetz. Basing on the analysis data of soil water extract, higher ameliorative efficiency of elemental sulfur compared to phosphogypsum and fast amelioration of alkali-saline soils with the use of sulfur have been detected. Ten month of phosphogypsum and elemental sulfur incubation in soils significantly affected presence and contents of the salts, restructuring their ionic contents and growth of total salts. The latter required carrying out washing of the soils from the starting primary and newly formed secondary salts from root-inhabited soil layer. Washing of the soils ambiguously affected the ionic contents of the soil solution. It created more benefactor conditions on the elemental sulfur variant, to a greater degree reducing contents of all ions compared to phosphogypsum (the exception was НCO3-).

TerraClimate, a high-resolution global dataset of monthly climate and climatic water balance from 1958\u20132015

We present TerraClimate, a dataset of high-spatial resolution (1/24°, ~4-km) monthly climate and climatic water balance for global terrestrial surfaces from 1958–2015. TerraClimate uses climatically aided interpolation, combining high-spatial resolution climatological normals from the WorldClim dataset, with coarser resolution time varying (i.e., monthly) data from other sources to produce a monthly dataset of precipitation, maximum and minimum temperature, wind speed, vapor pressure, and solar radiation. TerraClimate additionally produces monthly surface water balance datasets using a water balance model that incorporates reference evapotranspiration, precipitation, temperature, and interpolated plant extractable soil water capacity. These data provide important inputs for ecological and hydrological studies at global scales that require high spatial resolution and time varying climate and climatic water balance data. We validated spatiotemporal aspects of TerraClimate using annual temperature, precipitation, and calculated reference evapotranspiration from station data, as well as annual runoff from streamflow gauges. TerraClimate datasets showed noted improvement in overall mean absolute error and increased spatial realism relative to coarser resolution gridded datasets.

Organic Phosphorus Can Make an Important Contribution to Phosphorus Loss from Riparian Buffers

Core Ideas Forested and vegetative buffers can retain P runoff from adjacent fields. High concentrations of molybdate unreactive P were detected in soil water extracts. With time, these buffer soils can be a source of soluble inorganic and organic P. High microbial activity in buffer soils suggests biologically mediated P release. Vegetative buffer strips (VBS) and managed or unmanaged riparian zones between the edge of field and receiving watercourse are widely adopted conservation practices aimed at reducing nonpoint nutrient pollution. However, their effectiveness at decreasing phosphorus (P) loss has been mixed. This study investigated the effectiveness of a VBS and a forested riparian zone (FRZ) in decreasing P loss from pasture soils receiving swine manure and aimed to determine the potential factors controlling P release, using water extractable P (WEP) as a proxy for P loss. The inorganic WEP concentrations were significantly greater in the fertilized pasture zone soils than the VBS or FRZ soils. However, there was no significant difference between the field and riparian soils for total WEP due to increased contribution from organic WEP in these soils. Degree of P saturation, which is a function of soil test P, was a good predictor of inorganic WEP, but not organic WEP, where the variation in concentrations was better explained by variables involved in biotic P release.

Comparing traditional and digital soil mapping at a district scale using residual maximum likelihood analysis

Conventional soil mapping uses field morphological observations to classify soil profiles into predefined classification systems and extrapolates the classified soils to make a map based on aerial photographs and the experience of the surveyor. A criticism of this approach is that the subjectivity of the surveyor leads to non-reproducible maps. Advances in computing and statistical analysis, and an increased availability of ancillary data have cumulatively led to an alternative, referred to as digital soil mapping (DSM). In this research, two agriculturally productive areas (i.e. Warren and Trangie) located in central New South Wales, Australia, were considered to evaluate whether pedoderms and soil profile classes defined according to the traditional approach can also be recognised and mapped using a DSM approach. First, we performed a fuzzy k-means analysis to look for clusters in the ancillary data, which include data from remote-sensed gamma-ray (γ-ray) spectrometry and proximal-sensed electromagnetic (EM) induction. We used the residual maximum likelihood method to evaluate the maps for various numbers of classes (k = 2–10) to minimise the mean square prediction error (σ2p,C) of soil physical (i.e. clay content, field capacity (FC), permanent wilting point (PWP) and available water content (AWC)) and chemical (pH, EC of 1 : 5 soil water extract (EC1:5) and cation exchange capacity (CEC)) properties of topsoil (0–0.3 m) and subsoil (0.6–0.9 m). In terms of prediction, the calculated σ2p,C was locally minimised for k = 8 when accounting for topsoil clay, FC, PWP, pH and CEC, and subsoil FC, EC1:5 and CEC. A comparison of σ2p,C of the traditional (seven pedoderm components) and DSM approach (k = 8) indicated that only topsoil EC1:5 and subsoil pH was better accounted for by the traditional approach, whereas topsoil clay content, and CEC and subsoil clay, EC1:5 and CEC were better resolved using the DSM approach. The produced DSM maps (e.g. k = 3, 6 and 8) also reflected the pedoderm components identified using the traditional approach. We concluded that the DSM maps with k = 8 classes reflected the soil profile classes identified within the pedoderms and that soil maps of similar accuracy could be developed from the EM data independently.