Soil Column Experiments Research Articles

Brackish water promote the ecological restoration of estuarine wetland

By taking the indoor soil column experiment as the experimental simulation object, an infiltration experiment was conducted using freshwater and brackish water with different concentrations (3-g/L, 9-g/L). The constant head or air boundary of 3 cm was set as different variables (Where the air boundary means the water surface is flush with the soil interface, and the 3 cm fixed head boundary means the water accumulation depth is 3 cm above the soil interface). By analyzing the cumulative infiltration, soil water content, wetting peak, and infiltration rate, the effects of different water and salt conditions and different boundary conditions on the infiltration process were summarized and analyzed. The results show that the infiltration rate was most favorable under the 3-g/L brackish water infiltration. Under this condition, the cumulative infiltration was the largest, the time for the soil moisture content to reach saturation was the shortest, the wetting peak first reached the bottom of the soil column, and the soil water potential changed first. The constant head condition accelerated the infiltration rate of soil water, increased the cumulative infiltration, increased the soil water content, and reduced the time for the wetting peak to reach the bottom. Compared with that in the air boundary condition, the soil water potential under the constant head infiltration condition was larger. These experimental results show that to some extent, proper concentrations of saltwater are conducive to the infiltration and circulation of soil water. The demand for water saving in agricultural irrigation is increasing, and the efficiency of agricultural irrigation can be improved by making full use of the theory of unsaturated soil infiltration. The instability and complexity of unsaturated soil is due to the presence of matrix suction, so the study of unsaturated soil has profound theoretical significance.

Suffusion of a sand–clay mixture: impact of the ionic-concentration gradient, clay type, sand-grain size and hydraulic gradient

Internal erosion by suffusion within a sand–clay mixture may occur as detachment of clay particles, which is induced by a decrease in ionic concentration (IC) along with application of a high hydraulic gradient. Through designed laboratory soil-column experiments, this study investigates the impact of the IC gradient (stepwise or gradual decrease), clay mineralogy, sand particle size and hydraulic gradient on the suffusion of a sand–clay mixture. The observed breakthrough concentration of clay particles revealed the substantial suffusion of a sand–clay mixture caused by a stepwise decrease in the IC for kaolinite and illite, while similar filtrated quantities of bentonite were observed for stepwise and gradual decreases in IC. In addition, the small-grained sand showed a relatively high susceptibility to suffusion by a stepwise decrease in IC, most likely because of the low reattachment of detached clay particles. The mass of filtrated clay particles evaluated from the area of the observed breakthrough curves in this study provides a clear insight into the need to incorporate the IC gradient when assessing the susceptibility to the suffusion of clay-containing soils.

Irrigation-facilitated low-density polyethylene microplastic vertical transport along soil profile: An empirical model developed by column experiment

The emerging issue of microplastic pollution of agricultural soils derives from the intensive utilization of plastic mulching film. Although surface runoff may transport microplastic off-site, infiltration may also facilitate microplastic transport from surface soil to deeper depths. Microplastic comprises a relatively new category of soil contaminants, whose transport in the soil has not yet been widely studied. In this study, we investigated microplastic transport from contaminated surface soil (50 g kg-1) driven by irrigation, from permanent wilting point to saturation, and developed an empirical model to characterize the resulting accumulation of microplastic along soil profile. A soil column experiment was conducted under various treatments: the control, 1, 2 and 4 runs of irrigation. Soil samples were collected from inside and outside of soil cracks (if present) in each soil layer (0–2 cm (source layer), 2–5 cm, 5–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm). The results showed that with increasing irrigation runs, microplastic in the source soil layer decreased, while microplastic contents in deeper soil depths increased significantly (p < 0.05), varying from 7.03 g kg-1 in 2–5 cm to 0.29 g kg-1 in 40–50 cm soil. The microplastic content detected in soil cracks was 1.3–17.8 times higher than that detected in the soil matrix at similar depths, indicating that the transported microplastic is prone to be enriched in soil cracks. In addition, the total amount of transported microplastic increased 1.5 times after four irrigation runs, and the variations were significantly observed especially at deeper soil depths. Based on correlation analyses, data-fitted empirical models that relate cumulative microplastic to the depth of soil layer and irrigation runs indicate that irrigation-facilitated microplastic transport could be well-characterized (R2 >0.92). Further research is needed to develop an physical-based model in order to assess microplastic migration risks driven by irrigation and other agricultural management practices.

The Temporal–Spatial Dynamic Distributions of Soil Water and Salt under Deep Vertical Rotary Tillage on Coastal Saline Soil

Different from the traditional deep tillage, deep vertical rotary tillage can smash deep soil without disturbing the soil layer, which improves soil water infiltration and promotes salt leaching. This has gradually been applied in the research into saline alkali improvements. However, there is limited knowledge about the effect of deep vertical rotary tillage on the temporal–spatial distributions of soil water and salt under the shallow underground water level. Therefore, a preliminary soil column experiment was carried out to explore the results of water and salt movement under three different tillage methods: traditional rotary tillage depth of 20 cm (XG−20), deep vertical rotary tillage depth of 20 cm (FL−20) and deep vertical rotary tillage depth of 40 cm (FL−40). The temporal–spatial variation in soil water and salt was analyzed. The results showed that the average infiltration rate of FL−40 increased by 1.25 and 0.46 cm h−1 in 0−40 cm soil layer compared with that of XG−20 and FL−20. At the same time, soil water content was also increased, and the order of soil water content was FL−40 &gt; FL−20 &gt; XG−20. With the increase in tillage depth, the desalinization rate and the soil electric conductivity (EC) of FL−40 were increased and decreased, respectively. The FL−40 treatment’s average desalinization rates increased by 16.32% and 13.99% compared with XG−20 and FL−20 treatments’ in 0−60 cm soil layer. In conclusion, FL−40 had a better effect on regulating water and salt. The deep vertical rotary tillage provided an effective method for the control and optimization of water and salt in coastal saline soil.

Transport, retention and release of phytate in soil with addition of Mg–Al layered double hydroxides

Organic fertilizers have been excessively used for agricultural production, raising P loss risk to river systems. Phytate is the most abundant organic phosphorus (OP) in organic fertilizers. In this study, Mg–Al layered double hydroxides (LDHs) as environmentally friendly materials were applied to soils to control phytate loss from soil and improve the sustainable utilization of phytate. Adsorption kinetic experiments, XRD, and zeta potential measurements were conducted to investigate adsorption mechanisms of phytate on LDHs. Saturated soil column experiments and numerical modeling were conducted to investigate the transport, retention, and release behaviors of phytate in natural soil with and without LDHs. The KCl and CaCl2 solutions were chosen as leachate to simulate different types of soil solutions. Adsorption modes of phytate on LDHs contained electrostatic attraction and surface complexation but not interlayer anion exchange. Retention of phytate in the soil increased with the addition of LDHs or the presence of Ca2+ due to irreversible retention. The retention of phytate in soil-LDHs column reduced with increasing ionic strength (IS) of KCl due to the competition of Cl− with anionic groups of phytate on the LDHs (Meff: 1 mM, 12.1% of total phytate; 20 mM, 16.6% of total phytate; 100 mM, 20.7% of total phytate). On the other side, the release of phytate from soil-LDHs occurred by the competition of phosphate but was not obvious by IS reduction. The injection of phytate brought release of organic substances from soil and the dissolution of LDHs with increasing IS of KCl.

Synergistic Fertilizers Improved Chemical Properties of Soil in Wheat (Triticum aestivum L.) Field

ABSTRACT In this study, the efficiency of fertilizers was improved by coating the fertilizers with a hydrogel formed by the polymerization of itaconic acid (IA), maleic acid (MA), acrylic acid (AA), and potassium persulfate (KPS) to form a synergistic fertilizer and improve its slow-release performance. The effect of synergistic fertilizers on the changes in soil nutrients in wheat fields was studied through field and soil column experiments using ordinary and commercial synergistic fertilizers as controls and different application rates of `synergistic fertilizers as treatments. The results revealed that the alkali-hydrolyzed nitrogen (N) and total N contents were significantly higher in T1 than that in CK, and the treatments were ranked as T3 > T2 > T5 > T1 > CK > T4. The difference in the alkali-hydrolyzed N and total N contents between CK and T3 was significant. In terms of available phosphorus (P) and potassium (K) contents, the treatments were ranked as T1 > T4 > T2 > CK > T3 in all soil layers and T3 > T2 > T5 > T1 > CK > T4 in the soil column. The treatments were ranked as T4>CK>T3>T1>T2 in terms of soil organic matter (SOM) content. Compared with ordinary fertilizers, synergistic fertilizers could significantly increase the soil total N, alkali-hydrolyzed N, available P, and available K contents. Compared with ordinary slow-release fertilizers in the market, the effect of synergistic fertilizers is better in improving the use efficiency of fertilizers. By slowly releasing nutrients, synergistic fertilizers can continuously provide nutrients for the growth and development of wheat and improve the use efficiency of fertilizer.

Quantifying Phosphorus Leaching Loss from Mollisol with Organic Amendments

The phosphorus (P) leaching from continuous fertilization is generally neglected in mollisol. The in situ leaching loss of phosphorus (P), especially dissolved organic P, is poorly quantified under organic amendments given its potential environmental risks. In this study, we conducted an in situ soil column experiment, instead of the traditional measuring of the soil layer, in the mollisol area of northeast China to investigate the seasonal variations in different P forms under three typical fertilization practices, including chemical fertilizer (CF), CF supplemented with straw (CFS), and CF co-applied with straw and manure (CFSM). Compared with the CF treatment, CFS treatment generally reduced the leaching loss of dissolved organic P by 57.3% to reduce the total P loss, while the CFSM treatment increased the leaching loss of dissolved inorganic P by 20.9% to increase the total P loss. Other than the effects of management practices, precipitation and temperature-oriented environmental factors significantly affected the seasonal variation in leaching loss of both the dissolved and particulate P forms. We conclude that straw incorporation into the mollisol of northeast China is recommended, considering its low leaching risk of P, while a co-amendment of straw and manure resulted in the opposite. Despite the slight environmental risk of P leaching loss (0.75–1.95% of external P input per year) practically quantified by in situ experiments, a proper reduction in chemical P input with organic amendments may be an effective P fertilizer management strategy in mollisol areas.

Soil column experiment and numerical simulation research of Pb migration process in the groundwater fluctuation zone based on HYDRUS

Groundwater level fluctuation alters hydrodynamic conditions and hydrogeochemical action, thus affecting the migration and transformation of pollutants. This study investigated the effect of groundwater level fluctuations on Pb migration processes. We selected two typical media, coarse sand and medium sand, for the soil column experiments and numerical simulations of the Pb migration process in the groundwater level fluctuation zone. The soil column experiments showed that when the contaminants were distributed at a 30–40 cm depth in the soil column, the Pb migrated into the water in the range of 20–45 cm in coarse sand, while the range of Pb migration in medium sand decreased to 30 cm–40 cm. We constructed a numerical model of Pb migration in the aeration zone–saturation zone coupled with water transport and solute transport by HYDRUS-1D. The model simulated the migration process of Pb in different amplitude and frequency of water level fluctuation and initial concentration of pollutants. The results showed that the coarse sand column and medium sand column showed relatively noticeable changes in Pb concentration in water at 30–40 cm and 30–35 cm, respectively. The migration range and concentration of Pb in water are proportional to the medium particle size and the frequency of water level fluctuation, and inversely proportional to the magnitude of water level fluctuation. The Pb concentration in the water increased or decreased as the initial pollutant concentration of the medium increased or decreased. Its variation is basically the same as the variation of the initial contaminant concentration. The research results can provide a scientific basis for the remediation of heavy metal pollution in groundwater.

Response relationship of environmental factors caused by toluene concentration during leaching of capillary zone.

Due to the leaching of capillary water, the petroleum pollutants initially trapped in vadose zone may migrate to lower aquifer, thus increasing the risk of groundwater pollution. In order to explore the effect of capillary leaching on toluene-contaminated soil and the relationship between toluene concentration (TC) and environmental factors (EFs) during the leaching process, the sterilized and non-sterilized soil column experiments were designed. The EFs were used to estimate TC. The results showed that the difference between leaching and volatilization rates directly determined the changing trend of toluene concentration in capillary water. The toluene concentration in the medium always showed decreasing trend due to leaching. The indigenous microbial community structure of the non-sterilized soil column was analyzed by 16S rRNA sequencing. It was found that indigenous microorganisms could degrade toluene after 33.0 days of acclimatation. The microbial population was dominated by bacteria, among them the Ellin6055 strain and Pseudomonas, Pseudoxanthomonas, Cupriavidus, Bdellovibrio, Sphingobium, Phenylobacterium, Ramlibacter, Bradyrhizobium, Shinella genera. The Pseudomonas was the most crucial bacterial genus that degraded toluene. Indigenous microbial degradation was the fundamental reason for strong response relationship. Furthermore, we suggested a relationship of function between environmental factors (pH, DO, ORP) and time (t) for toluene attenuation: C0+ln(eAtαBγCβ)=CToluene, (α, β, γ represent the pH, DO, and ORP in leaching capillary water, respectively; A, B, and C represent undetermined coefficients), and the fitting coefficient R2>0.950. This relationship can only characterize the attenuation process of capillary zone leaching on toluene. However, it may still be utilized to give a theoretical foundation for understanding the dynamic of pollutant concentration change processes under specific environmental factors.

The chromium migration risk from tannery sludge into shallow soil and groundwater: Influence factors, modeling, and microbial response

Combined pollution in tannery sludge landfill has become increasingly serious. Accurate identification of the contribution of coexisting substances to Cr migration in tannery sludge sites was essential for the selection of remediation methods for tannery contaminated sites. However, the effect of the coexisting substances on their contribution to Cr migration remained unclear. In this study, the analytical method of panel data and soil column experiments were combined for the first time to quantify the extent to which different contaminants contribute to Cr migration, and further identify the dominant microbial species. Results showed that NH3–N inhibited the migration of Cr(VI), while NO3––N and fatliquor agent promoted the migration of Cr(VI). The panel data analysis showed that the order of the contribution rate of the factors affecting the Cr(VI) migration was Cr(VI) concentration, coexisting substances, and environment factors. In addition, Veronii was the dominant popular in fatliquors-contaminated soils. The relative abundance of Veronii increased from 6.31% to 30.48% in the fatliquors treatment group, while it decreased to 21.65% in the fatliquors and Cr treatment group. This study provided a quantitative method to the contribution rate of various factors to Cr migration under rainfall, taken into account the response of the microbial community in each experimental group, and provided theoretical support for the selection of remediation methods in soil and groundwater for tannery sites.

Livestock manure-derived hydrochar improved rice paddy soil nutrients as a cleaner soil conditioner in contrast to raw material

Hydrothermal carbonization (HTC) is a promising technology for resource disposal of livestock manure due to its advantages of high efficiency, low-energy consumption and no dehydration. Previous studies most focused on the characterization and applications in various fields of livestock manure-derived hydrochar (LMH). However, the effects of LMH as soil conditioner on agricultural soil nutrients, dissolved organic matter (DOM) changes and crop yields have not been clarified. The major factors affecting the rice yield of LMH after returning to the field are also seldom mentioned. In this study, a soil column experiment was conducted to explore the changes in soil basic characteristics, DOM and rice yield after returning cattle manure (CM) and cattle manure-derived hydrochar (CC180 and CC260) to the field on the premise of reducing inorganic fertilizer application. The results showed that CCs increased soil nutrient partly, including total phosphorus (by 6.8–18.9%), soil organic carbon (by 8.2%) and dissolved organic carbon (by 18.7%) compared to CM. Soil ammonium nitrogen and nitrate nitrogen concentrations of CCs decreased by 5.8–9.9% and 4.7–15.8% in comparison with CM. LMH increased the stability of phosphorus by increasing the content of calcium bound phosphorus in soil. Three-dimensional fluorescence spectra expressed that soil DOM contained humic-like acid substances (C1 and C2) and tyrosine-like substances (C4). The three substances contents in soil DOM under LMH treatment were higher than that of CM by 15.8–85%. In addition, infrared spectra and two-dimensional correlation analysis showed the structure and evolution of functional groups in soil DOM, which indicated that high temperature could increase the hydrophobic and saturated substances in soil DOM. Furthermore, CCs were more significant than CM in rice yield by 19.9–36.9%. The findings illustrated that LMH is more beneficial to agricultural soil as a soil conditioner to replace part of chemical fertilizer than CM.

Improvement of Onsite Wastewater Systems Performance: Experimental and Numerical Investigation

Population growth and the associated increase in the use of Onsite Wastewater Treatment Systems (OWTS) in the Black Hills have been a reason for interest in nitrate contamination within the public water supply over the past few years. The main concern for the Black Hills is the presence of karst formation that all OWTS for wastewater travel faster, limiting the natural attenuation of wastewater contaminants. The treatment performance of common soils in the Black Hills and wood-based media was evaluated using soil column experiments and a numerical model, HYDRUS 2D. Nitrate treatment performances were evaluated using alluvial and cedar soils collected from the Black Hills, sand, woodchips (loose and dense), and biochar. This research investigated hydraulic and reaction parameters through a combination of experimental and inverse modeling approaches. A good agreement was obtained between the measured and model-predicted soil moisture content, with R2 values ranging from 0.57 to 0.99. The model was calibrated using flow data and nitrate concentration data measured from leachate collected at the bottom of the experimental columns. Nitrate removal rates varied from 32.3% to 70%, with the highest removal rate in loose woodchips, followed by dense woodchip and biochar, and the lowest removal rate in alluvial materials. The biochar and loose woodchips removed an additional 20% compared to common soils, attributable to the enhanced denitrification rate due to higher water content and organic content. The use of woodchips and biochar should be implemented in OWTS, where there are known karst formations.

Construction, application and validation of a new algorithm for determining light nonaqueous-phase liquid fluxes in unsaturated zones

An analytical algorithm coupling free-phase migration, precipitation, and natural attenuation through volatilization and biodegradation (FPVB) was developed to calculate the flux of light nonaqueous-phase liquid (LNAPL) leaking from unsaturated zone to groundwater. Sandbox and soil column experiments were performed to identify the LNAPL migration characteristics and states to provide data to establish and verify FPVB algorithm. For free-phase migration, the Kinematic Oily Pollutant Transport (KOPT) model was used to determine LNAPL movement velocity and leakage time. The correlations of water saturation, residual LNAPL saturation and the cumulative dissolution ratio of residual LNAPL were described using an empirical formula for the precipitation leaching process. Equations for diesel volatilization kinetics and first order degradation were used to describe the natural attenuation processes. Coupling the algorithms for the different stages gave the final FPVB algorithm. The FPVB algorithm was used to describe the pollution situation at a real site, and the results were consistent with the actual situation. The FPVB algorithm could be used to quickly assess the scale and degree of pollution with little information on the parameters for the actual LNAPL leakage event.

Monitoring In Situ Microbial Growth and Decay in Soil Column Experiments by Induced Polarization

AbstractReal‐time monitoring of the microbial activity in porous media faces considerable challenges because conventional analytical procedures are intrusive. Induced polarization has shown promises as a non‐intrusive monitoring approach for such processes. However, quantitative analysis of soil column experiments to show how IP‐based parameters can be related to the density of bacteria is still lacking. The evolution of bacterial density and the induced polarization was performed in soil‐packed column experiments using Pseudomonas aeruginosa O1. A quantitative relationship between the quadrature conductivity and the bacterial density was established and further applied to assess the bacterial growth and decay, and infer the Monod kinetic parameters. The Monod kinetic parameters inferred from the column experiments mimicking field conditions were different to those obtained from the batch experiments.

Changes in Physicochemical Properties of Typical Subtropical Soils under Different Treated Domestic Wastewater Irrigation Modes

Irrigation with treated domestic wastewater (TWW) affects the physicochemical properties of soils, but little research has been conducted for different soils in subtropical regions. Consequently, in order to evaluate the effects of domestic wastewater (treated by A2/O process) irrigation on the hydraulic properties, soil salinity and sodicity of four typical subtropical agricultural soils, a soil-column experiment was conducted for one year with eight cycles of wetting and drying. A clay soil (red soil), a silty clay soil (aquic soil), a loamy clay soil (purple soil), and a silty clay loam soil (paddy soil) were subjected to three irrigation modes: (a) cyclic irrigation with TWW (W1), (b) alternating irrigations with TWW and distilled water (W2), and (c) irrigation with distilled water as a control (CK). Our results indicated that EC values increased significantly (p &lt; 0.05) with TWW irrigation for all the soils. TWW irrigation increased the concentrations of Na+, K+, Ca2+, Mg2+, and SAR, ESP values in the red soil, for the W2 treatment especially. In contrast, it decreased Na+, K+, Ca2+, Mg2+ accumulation and ESP values in the aquic soil. Moreover, the soil physical properties exhibited correlations with soil salinity. The saturated hydraulic conductivity (Ks) of the red soil, purple soil, and paddy soil were lower under the W1 and W2 treatments than CK, but the Ks of the aquic soil for W1 were 183.7% higher than that under CK. The unsaturated hydraulic conductivity (Kψ) of the purple soil and paddy soil decreased after TWW irrigation, but those of the aquic soil increased. The water-retention capacities (WRCs) of the TWW-irrigated red soil and aquic soil decreased as a consequence of a shift in the pore-size distribution toward wider pores, but the those of the purple soil and paddy soil improved, associated with narrower pores. The W2 treatment alleviated the impact of TWW on the aquic soil, purple soil, and paddy soil but negatively affected the physical properties, salinity, and sodicity of the red soil. Our results will provide useful information for managing soil and water under TWW irrigation in subtropical regions.

Removal of nitrate and pesticides from groundwater by nano zero-valent iron injection pulses under biostimulation and bioaugmentation scenarios in continuous-flow packed soil columns

This study evaluates the NO3− removal from groundwater through Heterotrophic Denitrification (HDN) (promoted by the addition of acetate and/or an inoculum rich in denitrifiers) and Abiotic Chemical Nitrate Reduction (ACNR) (promoted by pulse injection of zerovalent iron nanoparticles (nZVI)). HDN and ACNR were applied, separately or combined, in packed soil column experiments to complement the scarce research on pulse-injected nZVI in continuous-flow systems mimicking a Well-based Denitrification Barrier. Together with NO3−, the removal of two common pesticides (dieldrin and lindane) was evaluated. Results showed that total NO3− removal (>97%) could be achieved by either bioestimulation with acetate (converting NO3− to N2(g) via HDN) or by injecting nZVI (removing NO3− via ACNR). In the presence of nZVI, NO3− was partially converted to N2(g) and to a lower extent NO2−, with unreacted NO3− being likely adsorbed onto Fe-(oxy)hydroxides. Combination of both HDN and ACNR resulted in even a higher NO3− removal (>99%). Interestingly, nZVI did not seem to pose any toxic effect on denitrifiers. These results showed that both processes can be alterned or combined to take advantage of the benefits of each individual process while overcoming their disadvantages if applied alone. With regard to the target pesticides, the removal was high for dieldrin (>93%) and moderate for lindane (38%), and it was not due to biodegradation but to adsorption onto soil. When nZVI was applied, the removal increased (generally >91%) due to chemical degradation by nZVI and/or adsorption onto formed Fe-(oxy)hydroxides.

Effects of whole-orchard recycling on nitrate leaching potential in almond production systems.

Inefficient nitrogen (N) fertilization and irrigation have led to unhealthy nitrate levels in groundwater bodies of agricultural areas in California. Simultaneously, high commodity prices and drought have encouraged perennial crop growers to turnover less-productive orchards, providing opportunities to recycle tree biomass in situ and to use high-carbon (C) residues to conserve soil and water resources. Although climate change adaptation and mitigation benefits of high-C soil amendments have been shown, uncertainties remain regarding the benefits and trade-offs of this practice for N cycling and retention. We used established almond [Prunus dulcis (Mill.) D. A. Webb] orchard trials on Hanford fine sandy loam with short-term and long-term biomass recycling legacies to better understand the changes in N dynamics and retention capacity associated with this practice. In a soil column experiment, labeled N fertilizer was added and traced into various N pools, including microbial biomass and inorganic fractions in soil and leachate. Shifts in microbial communities were characterized using the abundance of key N cycling functional genes regulating nitrification and denitrification processes. Our findings showed that, in the short term, biomass recycling led to N immobilization within the orchard biomass incorporation depth zone (0-15cm) without impacts on N leaching potential. However, this practice drastically reduced nitrate leaching potential by 52%, 10 yr after biomass incorporation without an increase in N immobilization. Although the timing of these potential benefits as a function of microbial population and C and N biogeochemical cycles still needs to be clarified, our results highlight the potential of this practice to meaningfully mitigate nitrate discharges into groundwater while conserving soil resources.

Regreening properties of the soil slow-mobile H2bpcd/Fe3+ complex: Steps forward to the development of a new environmentally friendly Fe fertilizer.

The application of synthetic Fe-chelates stands for the most established agronomical practice to alleviate lime-induced chlorosis, which still constitutes a major agronomic problem. However, the percolation through the soil profile due to the negative charge of the most deployed molecules results in agronomical and environmental problems. H2bpcd/Fe3+ complex features distinctive chemical characteristics, including moderate stability of the Fe(bpcd)+ species (logβML = 20.86) and a total positive charge, and we studied its behavior in soil and regreening effects on cucumber plants. Soil column experiments have underlined that H2bpcd/Fe3+ is retained in more amounts than EDDHA/Fe3+. The new ligand was not proven to be toxic for the cucumber and maize seedlings. A concentration of 20 μM H2bpcd/Fe3+ attained regreening of Fe-deficient cucumber plants grown in the hydroponic solution supplied with CaCO3, similar to that shown by EDDHA/Fe3+. Experiments with a 2 μM concentration of 57Fe showed that cucumber roots absorbed H2bpcd/57Fe3+ at a slower rate than EDTA/57Fe3+. The high kinetic inertness of H2bpcd/Fe3+ may explain such behavior.

Arbuscular mycorrhizal fungi reduce potassium, cadmium and ammonium losses but increases nitrate loss under high intensity leaching events

BackgroundNutrients and heavy metals can be lost from soils via leaching, and arbuscular mycorrhizal fungi (AMF) can influence these events. Soil column experiments were carried out to examine whether leaching intensity and AMF can alter nutrient and Cd uptake in white clover plants and the extent of their losses through leaching.ResultsThe presence of AMF significantly increased shoot and total biomass, as well as increased N, P, Cu and Zn uptake independent of water amount applied; while root P and Cu uptakes were promoted by AMF at any water amount treatments. Higher water amounts led to reductions in total N, K and Zn uptake for AMF-colonized plants in comparison to moderate water amount treatments. In the absence of AMF, white clover at low water amount treatment exhibited maximal root Cd uptake. At high water amount treatments, the presence of AMF significantly decreased leachate volumes and the amount of leached NH4+, K and Cd while AMF significantly increased the amounts of leached NO3−.ConclusionsOverall we found that AMF-colonized white clover plants reduced NH4+, K and Cd loss from soils but increased the risk of NO3− loss under high intensity leaching conditions.

Combined Application of Organic Amendments and Gypsum to Reclaim Saline–Alkali Soil

Saline–alkali soils have high sodicity, high pH, and high levels of soluble salts, as well as carbonates. This study aimed to evaluate the effect of cattle manure and chicken manure combined with gypsum at three levels on reclaiming a saline–alkali soil, through a soil column experiment. Combined treatments were more effective than those of sole gypsum in reducing the initial exchangeable sodium percentage (ESP) below 5%. Electrical conductivity (ECe) was lowered below 1.6 dS m−1 by all treatments, except the control. The higher effectiveness of manures combined with gypsum can be explained by their synergistic effect on Na+ displacement and subsequent soil structure improvement, leading to an enhancement in the leaching process, and then the salinity/sodicity reduction. Soluble salts and Na+ were considerably reduced in all treatments at the first leaching. Soil ESP and ECe threshold values from the US Salinity Lab classification were reached by any treatment, except the control. The addition of cattle manure or chicken manure might enhance the reclamation effect of gypsum with leaching for some saline–alkali soils.