Soil Solution Concentrations Research Articles

Interaction of Mn and Cd during their uptake in Celosia argentea differs between hydroponic and soil systems

Celosia argentea (Amaranthaceae) can accumulate both Cd and Mn. This study reveals the interactive effect and underlying mechanism of Cd and Mn during their uptake in this species. Plants were grown in hydroponic and soil media with different Cd and Mn treatments. The concentrations of Cd and Mn in plants and soil solutions were determined by ICP-MS. The real-time Cd2+ flux values into roots were measured with non-invasive micro-test technology. Manganese supply significantly decreased Cd bioaccumulation in C. argentea in hydroponic experiments. The mean net Cd2+ flux rates into roots decreased by 10.5% and 56.9% with the addition of 0.01 and 0.5 mM Mn2+, respectively. The Mn supply (1 mM) increased the Michaelis constant by 1.8-fold but did not significantly change the maximum uptake velocity of Cd. In soil culture experiments, Mn application significantly increased Cd bioaccumulation and Cd concentrations in soil solutions. The interactions of Cd and Mn in C. argentea differ between hydroponic and soil cultures. Mn inhibits Cd uptake in hydroponic experiments via competition in common transport systems. The enhancement effect of Mn on Cd uptake in soil systems is attributed to an increase of Cd in soil solutions by competitive adsorption.

Image-based quantification of soil microbial dead zones induced by nitrogen fertilization

Microbial communities in agricultural soils underpin many ecosystem services including the maintenance of soil structure, food production, water purification and carbon storage. However, the impact of fertilization on the health of microbial communities is not well understood. This study investigates the spatial and temporal dynamics of nitrogen (N) transport away from a fertilizer granule with pore scale resolution. Specifically, we examined how soil structure and moisture content influence fertilizer derived N movement through the soil pore network and the subsequent impact of on soil microbial communities. We develop a mathematical model to describe N transport and reactions in soil at the pore-scale. Using X-ray Computed Tomography scans, we reconstructed a microscale description of a soil-pore geometry as a computational mesh. Solving two-phase water/air model produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The N-speciation model considered ammonium (NH4+), nitrate (NO3−) and dissolved organic N (DON), and included N immobilization, ammonification and nitrification processes, as well as diffusion in soil solution. We simulated the dissolution of a fertilizer pellet and a pore scale N cycle at three different water saturations. To aid interpretation of the model results, microbial activity at a range of N concentrations was measured. The model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predict that the maximum NH4+ and NO3− concentrations in soil solution around the pellet under dry conditions are in the order of 1 × 103 and 1 × 104 mol m−3 respectively, and under wet conditions 2 × 102 and 1 × 103 mol m−3, respectively. Supporting experimental evidence suggests that these concentrations would be sufficient to reduce microbial activity in the short-term in the zone immediately around the fertilizer pellet (ranging from 0.9 to 3.8 mm), causing a major loss of soil biological functioning. This model demonstrates the importance of pore-scale processes in regulating N movement and their interactions with the soil microbiome.

Raising the groundwater table in the non-growing season can reduce greenhouse gas emissions and maintain crop productivity in cultivated fen peats

Fen peatlands represent a globally important carbon (C) store, while also providing highly productive agricultural land. Drainage of these organic soils is required to create conditions suitable for crop growth, but this results in substantial greenhouse gas (GHG) emissions. One potential GHG mitigation option is to raise the groundwater table to reduce the duration and volume of peat exposure to aerobic conditions. However, the trade-off between maintaining food production and securing ecosystem function under a high water table (WT) presents a serious challenge for both land managers and policy makers. Therefore, we conducted a controlled mesocosm experiment to investigate the effects of WT elevation (from −50 cm to −30 cm) under three contrasting scenarios: (i) WT raised throughout the year, (ii) WT raised in the winter only, and (iii) WT raised in the growing season only. We measured GHG emissions, nitrate, ammonium and dissolved organic C concentrations in soil solution, alongside the yield of a commercially important crop (lettuce). Raising the WT throughout the year reduced lettuce yields by 37% and reduced CO2 emissions by 36% without changing the loss rates of N2O or CH4. Raising the WT only in the winter did not significantly reduce crop yield, but still suppressed CO2 emissions during the fallow period (by 30%). Raising the WT only in the growing season reduced root growth and CO2 emissions (by 27%), but had no major effect on lettuce yield. In conclusion, the present study shows that raising the groundwater table in the non-growing season reduced GHG emissions without negatively affecting lettuce yields, and may therefore represent a viable GHG mitigation option for agricultural peatlands.

Changes in microelement availability in a paddy field exposed to long-term atmospheric CO2 enrichment

The stimulations of plant growth and soil nutrient availability by elevated carbon dioxide (CO2) concentration have been demonstrated in a series of experiments. However, the long-term response of microelement availability to elevated CO2 in paddy ecosystems without micronutrient fertilizer inputs is a matter of debate. Changes of microelement availability in paddy field were investigated by performing a situ experiment under the Free Air CO2 Enrichment (FACE) platform that lasted for a decade. Elevated CO2 stimulated the dry matter production of rice and enhanced accumulation of iron (Fe), manganese (Mn), and zinc (Zn) in the stem and panicle. High CO2 concentration led to significant reductions in Fe, Mn, and Zn concentrations in soil solution at jointing and/or pre-filling stages, which were the vigorous growth periods for rice. A significant increase for Fe concentration in the surface water was observed at the vegetative stage, under elevated CO2 condition. Additionally, the contents of Zn extracted by diethylene triamine pentoacetic acid (DTPA) increased significantly in 0–10 cm soil treated by elevated CO2. Our study provides an improved understanding on changes of microelements availability in paddy field. The results demonstrated that high CO2 concentration promoted the accumulation of micronutrients in rice plants, but had no significant and positive effects on the availability of Fe and Mn in soil following a decade of CO2 fumigation.

Biochar retards Al toxicity to maize (Zea mays L.) during soil acidification: The effects and mechanisms

Biochar can effectively alleviate the Al phytotoxicity in acidic soils due to its alkaline nature. However, the longevity of this alleviation effect of biochar under re-acidification conditions is still unclear. In the present study, the maize root growth responding to the simulated re-acidification of two acidic soils amended by peanut straw biochar or Ca(OH)2 was investigated to evaluate the long-term effect of biochar on alleviating Al toxicity in acidic soils. Compared with Ca(OH)2 amendment, the application of biochar significantly retarded Al toxicity to plant during soil re-acidification. When 4.0 mM HNO3 was added, the maize seedling root elongation in an Oxisol with biochar was 99% higher than that in the Oxisol with Ca(OH)2. Also, the Evans blue uptake and Al content in the root tip in the biochar treatment were 60% and 51% lower than those in the Ca(OH)2 treatment. The retarding effect was mainly attributed to the slow decrease in soil pH during acidification and the release of dissolved organic carbon (DOC) in the soils amended by biochar. The slower decrease in soil pH resulting from the increased pH buffering capacity after biochar application inhibited the increase of soluble and exchangeable Al during re-acidification. The increased DOC after biochar application decreased the toxic soluble Al speciation at the same pH value and total Al concentration in soil solution. Therefore, given the re-acidification of soils, biochar presented a longer-term effect on alleviating Al toxicity of acidic soil than liming.

Increased irrigation water salinity enhances nitrate transport to deep unsaturated soil

AbstractExcessive use of N fertilizers in agriculture often leads to NO3− accumulation in the unsaturated zone and to groundwater pollution. There is uncertainty regarding the variability in fertilizer transport and uptake efficiency due to the lack of studies based on continuous nondestructive measurements in unsaturated soils. In this study, we analyzed solute dynamics across the unsaturated zone underlying cultivated agricultural fields. Commercial crop rotations under four treatments, comprising two N fertilization regimes and two irrigation water salinity levels, were conducted in loess soil in the semiarid climate of the northern Negev Desert, Israel. The impact of the various treatments on water and solute dynamics below the root zone was monitored by a vadose zone monitoring system. The patterns of variations in soil water content and solute concentrations were analyzed using nonnegative tensor factorization. We found that irrigating using higher salinity water resulted in the earlier arrival of wetting fronts to the deeper layers and increased NO3− concentrations relative to the lower salinity treatments. Surprisingly, this effect was only seen in the deeper soil levels, whereas there was no significant difference in the arrival times and concentrations in the upper soil layers. Possible mechanisms are suggested and discussed.

Increased soil pH and dissolved organic matter after a decade of organic fertilizer application mitigates copper and zinc availability despite contamination

Long-term organic fertilizer (OF) application on agricultural soils is known to induce soil Cu and Zn contamination, along with pH and organic matter changes, which in turn alter the soil Cu and Zn availability. Our study was aimed at assessing Cu and Zn availability in long-term OF-amended soils by distinguishing the importance of increased contamination levels versus pH and organic matter changes in soil. Seventy-four soil samples were collected over time from fields corresponding to three soil types upon which no, mineral, or organic fertilization had been applied over a decade, and thus exhibited a gradient of Cu and Zn contamination, pH, and organic matter concentration. Soil Cu and Zn contamination (i.e. total and DTPA-extractable Cu and Zn concentration), soil solution chemistry (i.e. pH and dissolved organic matter concentration and aromaticity) and Cu and Zn availability (i.e. total concentration and free ionic activity in solution and DGT-available concentration in soil) levels were measured. The Windermere humic aqueous model (WHAM) was used to estimate Zn2+ activity and dissolved organic matter (DOM) binding properties in soil solution. Regardless of the soil type, organic fertilization increased Cu and Zn contamination in soil, in addition to the pH and the DOM concentration, aromaticity and binding properties in soil solution. The pH increase prompted a decrease in the total Zn concentration and Zn2+ activity in soil solution. The concomitant pH increase and DOM concentration, aromaticity and binding properties boosted the total Cu concentration but decreased the Cu2+ activity in soil solution. DGT-available Cu and Zn varied very little between the three fertilization modalities. Our results suggest that pH and DOM changes were able to regulate Cu and Zn availability in long-term OF amended soils by exerting a protective effect that offset the concomitant increase in soil Cu and Zn contamination.

Application of biochars and solid fraction of digestate to decrease soil solution Cd, Pb and Zn concentrations in contaminated sandy soils.

Biochar prepared from waste biomass was evaluated as a soil amendment to immobilize metals in two contaminated soils. A 60-day incubation experiment was set up on a French technosol which was heavily contaminated with Pb due to former mining activities. Grass biochar, cow manure biochar (CMB) and two lightwood biochars differing in particle size distribution (LWB1 and LWB2) were amended to the soil at a rate of 2% (by mass). Rhizon soil moisture samplers were employed to assess the Pb concentrations in the soil solution at regular times. After 30days of incubation, soil solution concentrations in the CMB-amended soil decreased by more than 99% compared to the control. CMB was also applied to a moderately contaminated Flemish soil and resulted in lowered soil solution Cd and Zn concentrations. While the application of 4% CMB resulted in 90% and 80% reductions in soil solution concentrations of Cd and Zn, respectively, the solid fraction of digestate (as a reference) reduced the soil pore water concentrations by only 63% for Cd and 73% for Zn, compared to the concentrations in the control. These results emphasize the potential of biochar to immobilize metals in soil and water systems, thus reducing their phytotoxicity.

Vegetation canopy effects on total and dissolved Cl, Br, F and I concentrations in soil and their fate along the hydrological flow path

Although halogens are omnipresent in the environment, detailed understanding of processes involving chlorine (Cl), bromine (Br), fluorine (F) and iodine (I) in the terrestrial halogen cycle is still sparse. Our objectives were to (i) assess vertical depth profiles of total and water-extractable inorganic halogen concentrations (Cltot, Brtot, Ftot, Itot) in solid soil, (ii) test the effect of a tree canopy, and (iii) follow the fate of dissolved inorganic halogens along the hydrological flow path. More than 200 soil samples and ecosystem solutions (rainwater, soil solution, adit and creek water) collected in the Schwarzwald, SW Germany, were analyzed by combustion ion chromatography and ion chromatography for total and inorganic halogen concentrations.We found decreasing Cltot concentrations with increasing soil depth which were indicative of biological chlorination of organic matter and nutrient uplift, both associated with Cl accumulation in upper soil horizons. Vertical patterns of total Br, F and I were contrary to Cltot concentrations and were related significantly (positively) to pedogenic oxides, revealing their dependence on abiotic processes. The presence of a canopy at our study site resulted in significantly higher halogen concentrations in throughfall compared to rainfall and higher Brtot concentrations in the organic layer. We attribute this difference to leaching from leaves and needles and wash-off of dry deposition. There were hardly any differences in halogen concentrations along the hydrological flow path except for significantly higher inorganic I concentrations in soil solution compared to rainfall due to equilibrium reactions between the soil solution and the solid soil phase. Highest inorganic F concentrations of up to 0.2 mg L−1 were detected in creek water samples and may originate from the weathering of fluorite-bearing veins. Our study indicates halogen-specific processes underlying Cl, Br, I and F cycling in ecosystems.

Toxicity and bioavailability of antimony in edible amaranth (Amaranthus tricolor Linn.) cultivated in two agricultural soil types

Although elevated levels of antimony (Sb) in agricultural soil and plant systems can have harmful effects on human health and ecosystems, little is known about the toxicity of Sb to plants and its mechanism. The assessment of Sb bioavailability is essential for understanding its potential risks and toxicity. In this study, we used pot experiments with two agricultural soil types spiked with Sb to investigate the dose-effect relationship between exposure to Sb and toxic effects (growth and bioaccumulation) on edible amaranth (Amaranthus tricolor Linn.). Soil solution (pore water) and seven single extractants were used to assess the bioavailability of Sb. Different toxic effects of Sb to amaranth cultivated in two types of soils (alkaline and acid soil) were observed. In alkaline soil (chestnut soil, pH 8.39), antimony is more easily absorbed by root and transported to shoot by plants, leading to more adverse effects, than in acid soil (pH 4.91) under the same exposure level. Our findings also highlight the need for more attention on asymptomatic accumulation of Sb in plants, especially for agricultural products cultivated in contaminated areas. The extraction efficiency of Sb was various in different extractants and soil types, Mehlich 3, NaHCO3 and Na2HPO4 for Sb were more efficient than other extractants in both tested alkaline and acid soil. Based on the extractability and correlation coefficients of toxic effects on amaranth and extractable Sb, we found that 0.1 M Na2HPO4 is the best extractant to predict the bioavailability of Sb in soil, and M3 is a suitable alternative. Antimony concentration in soil solution can also be used as an alternative indicator of the bioavailability of Sb.

Efficient Use of Water and Fertilizers in Irrigated Agriculture: Drip Irrigation and Fertigation

Abstract Increasing food demand and decreasing water resources have composed a kind of pressure to find new technologies for efficient use of water and fertilizers in agriculture. Drip irrigation can be able to save irrigation water from 30% up to 50% in case it is properly designed, installed and operated compared to surface irrigation, and it can also enable increasing crop yields and crop quality. In order to get the highest benefits using drip irrigation, some soil data (infiltration rate, soil texture and soil structure), crop characteristics (row space, plant density, canopy cover, root system, crop species, crop variety) and water resources properties (water quality, surface or well water) must be considered in drip system design, management and operation. Fertigation is basically an agricultural technique and application together with water and fertilizer to soil and/or plants. It increases both yield and fertilizer use efficiency; therefore, leaching of nutrients is prevented. In order to utilize fertigation successfully, the four main factors must be considered: (i) the consumption rate of water and nutrients throughout the growth season that result in optimal yields, (ii) response in uptake of different crops to nutrient concentration in the soil and soil solutions, (iii) monitoring for total soil water potential, nutrients concentration in soil solution and % elements in plants as a function of time and (iv) root mass and distribution in the soil for given irrigation regimes and soil types.

Manure plume modeling in feedlot pen soils

The generation of large amounts of manure by confined cattle feeding operations (feedlot) in reduced areas is a concern due to its potential to act as pollutant for ground and surface water. Studies have revealed that leaching may occur in pen soils, with negative effects on water quality. The objective of this work was to develop a mathematical model for predicting manure plume vertical advancement in soil beneath feedlot pens. The study was carried out in feedlot pens situated in a Argentine region called the Sandy Pampa (Pampa Arenosa). Five areas or treatments were selected, four of which were located in pens (considerably impacted by beef cattle operations) with 1, 4, 8 and 15 years of use, and the remaining one in natural soil area as control. The soil in the study areas was morphologically characterized. Applying standard procedures, the following variables were quantified: gravimetric moisture content and chloride concentration in soil solution. Chloride ion was used as a tracer to estimate manure flux. Data of different chloride profiles adjusted to a first-order model, from which it was possible to predict the depth of penetration of the manure, and the factor of plume advance in the underlying soil. In addition, the dominance of flows was analyzed from the development of a flow number indicator (Nf), which could be useful for environmental regulatory purposes bringing a base for easy estimation of pollutant transport mechanism in water–soil systems.

Biological enhancement of mineral weathering by <i>Pinus</i> <i>sylvestris</i> seedlings – effects of plants, ectomycorrhizal fungi, and elevated CO<sub>2</sub>

Abstract. Better understanding and quantifying the relative influence of plants, associated mycorrhizal fungi, and abiotic factors such as elevated CO2 on biotic weathering is essential to constraining weathering estimates. We employed a column microcosm system to examine the effects of elevated CO2 and Pinus sylvestris seedlings, with or without the ectomycorrhizal fungi Piloderma fallax and Suillus variegatus, on rhizosphere soil solution concentrations of low-molecular-weight organic acids (LMWOAs) and on the weathering of primary minerals. Seedlings significantly increased mineral weathering, as estimated from elemental budgets of Ca, K, Mg, and Si. Elevated CO2 increased plant growth and LMWOA concentrations but had no effect on weathering. Colonization by ectomycorrhizal fungi, particularly P. fallax, showed some tendency to increase weathering. LMWOA concentrations correlated with seedling biomass across both CO2 and mycorrhizal treatments but not with total weathering. We conclude that nutrient uptake, which reduces transport limitation to weathering, is the primary mechanism by which plants enhanced weathering in this system. While the experimental system used departs from conditions in forest soils in a number of ways, these results are in line with weathering studies performed at the ecosystem, macrocosm, and microcosm scale, indicating that nutrient uptake by plants and microbes is an important biological mechanism by which mineral weathering is enhanced.

Influence of amendments on metal environmental and toxicological availability in highly contaminated brownfield and agricultural soils.

The immobilizing effects of wood biochar (BW2%) and iron grit (Z1%) applied alone or in combination (BW2% + Z1%) to agricultural (M750) and brownfield (MAZ) soils highly contaminated by metals were assessed in a greenhouse experiment. The results showed that Z1% and BW2% + Z1% were the most efficient amendments to reduce Cd, Cu, Pb, and Zn mobility, environmental availability, and phytoavailability in the M750 soil. The oxidation of Z1% allowed part of the Cu and Zn pools present in exchangeable or carbonate-bound forms (labile fraction) to complex in less mobile forms. In this soil, the metal chemical extractions (0.01 M CaCl2 and 0.05 M EDTA) and the DGT (diffusive gradient in thin films) devices to assess metal in soil solution and soil pore water (SPW) also highlighted the immobilizing characteristic of Z1%. In most cases, the addition of BW2% to Z1% (BW2% + Z1%) did not improve this effect, except for the dissolved Pb and Zn concentrations in the M750 soil solution. It was also observed that Cd, Pb, and Zn passed throughout DGT mimicking the biological cell membrane were reduced by all amendments of the M750 soil corroborating metal concentrations measured in rye grass shoots. In the MAZ soil, metals were less available as shown by their low extractability rate, low capacity of metal resupply from the solid phase to pore water, and low phytoavailability. The poor metal availability could be explained by the high levels of carbonate and organic matter contents in this soil. Nevertheless, a decrease of the Cu environmental availability and the Cu concentrations in rye grass shoots grown on the MAZ soil was also observed in the soil amended with Z1% alone or in combination with BW2%. From a health point of view, the most effective amendment to reduce human exposure through ingestion of soil particles for the M750 and MAZ soils was BW2% for Cd and BW2% + Z1% for Pb. However, the presence of rye grass minimized the amendments' beneficial effects.

Adsorption of Lead, Cadmium, and Nickel on Benchmark Soils of Pakistan

Adsorption and desorption reactions at the solid phase–solution interface, play a significant role in controlling metal concentrations in soil solution and metal translocation to plants. Five predominant benchmarks soils of Pakistan were characterized for their lead (Pb), cadmium (Cd), and nickel (Ni) adsorption parameters by constructing equilibrium adsorption isotherms. The adsorption parameters (maximum adsorption capacity and affinity coefficient) were calculated by fitting measured adsorption data to Langmuir, Freundlich, and Redlich–Peterson adsorption models. Thermodynamic properties (Gibbs free energy—ΔG°, enthalpy—ΔH°, and entropy—ΔS°) were measured by equilibrating soils with Pb, Cd, and Ni solution at 25 ± 2 and 45 ± 2°C. The results revealed that the Langmuir and Redlich–Peterson adsorption models described metal adsorption data equally good. Langmuir’s predicted Pb, Cd, and Ni adsorption demonstrated better correlation with measured adsorption than Freundlich’s model. According to the maximum Pb, Cd, and Ni adsorption calculated by Langmuir and Redlich–Peterson models and Freundlich sorbate affinity to sorbent, the studied soils were formed the following sequence: Kotli > Miranpur > Gujranwala > Shahdara > Rasulpur. The magnitude of metal adsorption (b and qmon) and affinity (Kf) was highly correlated with the clay, soil organic matter, and iron and aluminum contents and cation exchange capacity. The measured metal adsorption in different soils followed the order: Pb > Cd > Ni. The magnitude of maximum Pb sorption (calculated by Langmuir and Redlich–Peterson models) was approximately two and four times higher than that for Cd and Ni, respectively. Similarly, the Freundlich’s sorbate affinity was also higher for Pb than for Cd and Ni. Thermodynamic parameters revealed that the Pb, Cd, and Ni adsorption reactions were spontaneous and exothermic in nature, and the process was dominated by physical adsorption.

Broccoli Nutrition and Changes of Soil Solution with Green Manure and Mineral Fertilization

The crop response and characteristics of soil solution (SS) change depending on the dose and fertilizer type used. This research determined the growth and yield of the broccoli and changes of the SS to identify the effect of the dose and fertilizer type used for the crop nutrition. Mineral fertilizer (MF) in 200% of the recommended dose (MF200), 10 t ha−1 of the green manure velvet bean (GM10), MF similar to that supplied with GM10 (MF=GM10), GM10 + MF to supply a dose similar to that applied with MF200 (GM10+MF=MF200), and a control treatment were applied to broccoli. GM10 promoted growth, yield, and dry matter (DM) similar to the control but promoted less electrical conductivity (EC) in SS in the first 21 days after transplanting (TF21DAT). Less yield, harvest index (HI), DM, accumulation of nutrients, recovery efficiency (RE) of Ca and Mg, EC, and macronutrient concentration of SS in TF21DAT were obtained with GM10 compared with MF=GM10. The GM10+MF=MF200 promoted less accumulation of N, P, and Mg and EC in the SS in TF21DAT compared with MF200. A negative correlation was observed between the canopy area with the EC and concentration of N, K, Ca, Mg, and S of the SS. The GM10 did not alter the growth, yield, and DM of broccoli. Higher yield, DM, and RE were obtained with MF=GM10 compared with GM10. The combined fertilization allowed to obtain similar growth, yield, DM, and RE to the obtained with MF200. The characteristics of SS changed depending on fertilization dose, fertilizer type, and broccoli growth.

Spatially resolved soil solution chemistry in a central European atmospherically polluted high-elevation catchment

Abstract. We collected soil solutions by suction lysimeters in a central European temperate forest with a history of acidification-related spruce die-back in order to interpret spatial patterns of soil nutrient partitioning, compare them with stream water chemistry and evaluate these parameters relative to concurrent loads of anions and cations in precipitation. Five lysimeter nests were installed in the 33 ha U dvou loucek (UDL) mountain catchment at different topographic positions (hilltops, slopes and valley). Following equilibration, monthly soil solution samples were interrogated over a 2-year period with regard to their SO42-, NO3-, NH4+, Na+, K+, Ca2+, Mg2+ and total dissolved Al concentrations, organic carbon (DOC) and pH. Soil pits were excavated in the vicinity of each lysimeter nest to also constrain soil chemistry. For an estimation of phosphorus (P) availability, ammonium oxalate extraction of soil samples was performed. Cation exchange capacity (CEC ≤58 meq kg−1) and base saturation (BS ≤13 %) were found to be significantly lower at UDL than in other monitored central European small catchments areas. Spatial trends and seasonality in soil solution chemistry support belowground inputs from mineral-stabilized legacy pollutants. Overall, the soil solution data suggest that the ecosystem was still chemically out of balance relative to the concurrent loads of anions and cations in precipitation, documenting incomplete recovery from acidification. Nearly 30 years after peak acidification, UDL exhibited similar soil solution concentrations of SO42, Ca2+ and Mg2+ as median values at the Pan-European International Co-operative Program (ICP) Forest sites with similar bedrock lithology and vegetation cover, yet NO3- concentrations were an order of magnitude higher. When concentrations of SO42-, NO3- and base cations in runoff are compared to soil pore waters, higher concentration in runoff points to lateral surficial leaching of pollutants and nutrients in excess than from topsoil to subsoil. With P availability being below the lowest range observed in soil plots from the Czech Republic, the managed forest ecosystem in UDL probably reflects growing inputs of C from regenerating vegetation in the N-saturated soil, which leads to P depletion in the soil. In addition, the observed spatial variability provides evidence pointing to substrate variability, C and P bioavailability, and landscape as major controls over base metal leaching toward the subsoil level in N-saturated catchments.

RELEASE OF SULFUR ON PADDY SOIL CONDITION

The objective of this study was to determine the release of S in paddy soil. The experiment was carried out in the greenhouse which the soil sample was taken from three different sites. The treatment consists of (T0) control, (T1) 0.02 g S pot-1, (T2) 0.04 g S pot-1, (T3) 0.08 g S pot-1, (T4) 0.04 g S pot-1 + rice straw. The concentration of S was measured in soil, surface water (soil solution) and leached water. The results showed that the addition of S increased the available S. In general, concentration of S in soil was high for site 1 and 3. It was possible due to the higher clay content for site 1 and 3 compared to site 2. The higher S concentration in soil solution was obtained by treatment T3 for all sites. Sulfur concentration in leached water was higher for T2 compared to T4. It indicated that rice straw could protect the release of S in leached water.

Evaluation of several phosphate amendments on rare earth element concentrations in rice plant and soil solution by X-ray diffraction

The exploitation and smelting of rare earth resources lead to serious pollution of rare earth elements (REEs) in farmland around mining area. The influence of four kinds of phosphate amendments—phosphate rock (PR), superphosphate (SSP), bone char (BC), and calcium magnesium phosphate (CMP)—on the bioavailability of REEs and the uptake and accumulation of 15 types of REE in rice were conducted in this study. Soil solutions were collected at tillering stage, heading stage and maturing stage, and rice was harvested at maturing stage. The mechanism of phosphate amendments reducing the bioavailability of REEs was studied by X-Ray diffraction and ICP-MS. PR treatment inhibited rice growth, but SSP, BC and CMP treatments all promoted rice growth, improved biomass of roots, shoots and grains, and promoted the uptake of phosphorous in rice. When compared with the CK, SSP, BC and CMP reduced the total REE concentrations in rice roots by 82.2%, 67.9% and 89.6%, shoots by 75.4%, 40.1% and 65.5%, grains by 23.8%, 29.0% and 29.3%, respectively. PR, SSP, BC and CMP significantly reduced the concentrations of REEs in the soil solution at three stages of rice growth. Analytic results of X-ray diffraction shows that adding PR, SSP, BC and CMP can lead to the formation of rare earth phosphate in the soil, thus reduce the activity of the REEs in the soil. Because SSP releases H+ during its dissolution, which has the risk of activating REEs in soil, CMP and BC are potential materials for remediation of REE-contaminated soil.

Wheat Straw Biochar Increases Potassium Concentration, Root Density, and Yield of Faba Bean in a Sandy Loam Soil

ABSTRACTA greenhouse experiment was conducted to study the effect of different irrigation levels (100%, 75%, and 50% of water requirement) and wheat straw biochar levels (0%, 1.25%, 2.5%, 3.75%, and 5% w/w) on faba bean yield, water productivity, root length density, and different ions concentration in soil solution, using a factorial arrangement in complete randomized design with three replications. Results showed that application of high level of biochar (5% w/w) destroyed the plants before they reached maturity. The maximum yield was obtained in 1.25% w/w biochar under full irrigation, while the maximum water productivity was obtained in 2.5% w/w biochar and 50% of water requirement. Further, the root length density in soil top layer (0–8 cm) was significantly more than those in 8–16 cm, due to holding more water content in top layer and no drainage from the pots. Sodium, potassium, calcium and magnesium ions’ concentrations in soil solution were significantly increased by increasing biochar levels; however, the rate of increase in potassium was higher than other ions due to high potassium concentration in biochar in comparison with the soil. In conclusion, application of biochar in the level of 1.25% w/w is suggested as a suitable agent to decrease water consumption and improving the crop performance.