Impact of woodchip biochar amendment on the sorption and dissipation of pesticide acetamiprid in agricultural soils

Pyrolysis of vegetative biomass into biochar and application of the more stable form of carbon to soil have been shown to be effective in reducing the emission of greenhouse gases, improving soil fertility, and sequestering soil contaminants. However, there is still lack of information about the impact of biochar amendment in agricultural soils on the sorption and environmental fate of pesticides. In this study, we investigated the sorption and dissipation of a neonicotinoid insecticide acetamiprid in three typical Chinese agricultural soils, which were amended by a red gum wood (Eucalyptus spp.) derived biochar. Our results showed that the amendment of biochar (0.5% (w/w)) to the soils could significantly increase the sorption of acetamiprid, but the magnitudes of enhancement were varied. Contributions of 0.5% newly-added biochar to the overall sorption of acetamiprid were 52.3%, 27.4% and 11.6% for red soil, paddy soil and black soil, respectively. The dissipation of acetamiprid in soils amended with biochar was retarded compared to that in soils without biochar amendment. Similar to the sorption experiment, in soil with higher content of organic matter, the retardation of biochar on the dissipation of acetamiprid was lower than that with lower content of organic matter. The different effects of biochar in agricultural soils may attribute to the interaction of soil components with biochar, which would block the pore or compete for binding site of biochar. Aging effect of biochar application in agricultural soils and field experiments need to be further investigated.     

Use of amendments to reduce leaching loss of phosphorus and other nutrients from a sandy soil in Florida

Goal, Scope and Background Transport of P from agricultural land contributes to the eutrophication of surface waters. Soil amendment is considered one of the best management practices (BMPs) to reduce P loss from sandy soils. Laboratory column leaching experiments were conducted to evaluate the effectiveness of different soil amendments in reducing P leaching from a typical sandy soil in Florida. Methods The tested amendments were CaCl₂, CaCO₃, Al(OH)₃, cellulose, and mill mud, and applied at the rate of 15 g/kg for a single amendment and each 7.5 g/kg if two amendments were combined. Leaching was conducted every four days for 32 days, 250 mL of deionized water being leached for each column per leaching event. Leachates were collected from each leaching event and analyzed for reactive P, PO₄-P, and macro and micro-elements. Results and Discussion Except for the soils amended with CaCl₂, or CaCl₂+CaCO₃, reactive P and PO₄-P leaching losses mainly occurred in the first three leaching events. Phosphorus leaching from the soils amended with CaCl₂ or CaCl₂+CaCO₃ was less but more persistent than that of other amendments. Reactive Pleaching loss was reduced by 36.0% and 40.4% for the amendments of CaCl₂, and CaCl₂+CaCO₃, respectively, as compared with chemical fertilizer alone, and the corresponding values for PO₄-P were 70.8% and 71.9%. The concentrations of K, Mg, Cu, and Fe in leachate were also decreased by CaCl₂ or CaCl₂+CaCO₃ amendment. Among the seven amendments, CaCl₂, CaCO₃, or their combination were most effective in reducing P leaching from the sandy soil, followed by cellulose and Al(OH)₃, the effects of mill mud and mill mud + Al(OH)₃ were marginal. Conclusions These results indicate that the use of CaCl₂, CaCO₃, or their combination can significantly reduce P leaching from sandy soil, and should be considered in the development of BMPs for the sandy soil regions. Recommendations and Outlook Most agricultural soils in south Florida are very sandy with minimal holding capacities for moisture and nutrients. Repeated application of fertilizer is necessary to sustain desired yield of crops on these soils. However, eutrophication of fresh water systems in this area has been increasingly concerned by the public. Losses of P from agricultural fields by means of leaching and surface runoff are suspected as one of the important non-point contamination sources. The benefits and effectiveness of soil amendment in reducing P losses from cropping production systems while sustaining desired crop yield need to be demonstrated. Calcium chloride, CaCO₃, or their combination significantly reduce Pleaching from sandy soil, and should be considered in the development of BMPs for the sandy soil regions.     

Contrasting effects of black carbon amendments on PAH bioaccumulation by Chironomus plumosus larvae in two distinct sediments: role of water absorption and particle ingestion

Two sediment matrices with different characteristics were amended with chars from different sources for bioaccumulation assay with filter-feeding Chironomus plumosus larvae. Chars greatly decreased porewater concentrations of PAHs (C_iw) measured using polyethylene devices in sediments. In organic rich sediment matrix-based systems where suspended char particles were absent, PAH concentrations in larvae (C_iB) were significantly correlated with C_iw, and there was no difference in water-based bioaccumulation factors (BAFs) between different treatments, suggesting that water absorption was the main contaminant uptake route for larvae. In organic poor sediment matrix-based systems where suspended char particles were present, poor Pearson correlation between C_iB and C_iw was found, but there was a significant linear increase of BAF values with char contents, which indicated that ingestion of suspended char particles could also be important for PAH bioaccumulation. Therefore, we need to rethink of the effectiveness and risks for the application of black carbon to sediment/soil remediation.     

Effect of charcoal amendment on adsorption, leaching and degradation of isoproturon in soils

The effects of charcoal amendment on adsorption, leaching and degradation of the herbicide isoproturon in soils were studied under laboratory conditions. The adsorption data all fitted well with the Freundlich empirical equation. It was found that the adsorption of isoproturon in soils increased with the rate of charcoal amended (correlation coefficient r=0.957**, P<0.01). The amount of isoproturon in leachate decreased with the increase of the amount of charcoal addition to soil column, while the retention of isoproturon in soils increased with an increase in the charcoal content of soil samples. Biodegradation was still the most significant mechanism for isoproturon dissipation from soil. Charcoal amendment greatly reduced the biodegradation of isoproturon in soils. The half-lives of isoproturon degradation (DT(50)) in soils greatly extended when the rate of added charcoal increased from 0 to 50 g kg(-1) (for Paddy soil, DT(50) values increased from 54.6 to 71.4 days; for Alfisol, DT(50) from 16.0 to 136 days; and for Vertisol, DT(50) from 15.2 to 107 days). The degradation rate of isoproturon in soils was significantly negatively correlated with the amount of added charcoal. This research suggests that charcoal amendment may be an effective management practice for reducing pesticide leaching and enhancing its persistence in soils.     

Evaluating the phytoremediation potential of Phragmites australis grown in pentachlorophenol and cadmium co-contaminated soils

Pot-culture experiments were conducted to evaluate the phytoremediation potential of a wetland plant species, Phragmites australis in cadmium (Cd) and pentachlorophenol (PCP) co-contaminated soil under glasshouse conditions for 70 days. The treatments included Cd (0, 5 and 50 mg kg^?1) without or with PCP (50 and 250 mg kg^?1). The results showed that growth of P. australis was significantly influenced by interaction of Cd and PCP, decreasing with either Cd or PCP additions. Plant biomass was inhibited and reduced by the rate of 89 and 92 % in the low and high Cd treatments and by 20 and 40 % in the low and high PCP treatments compared to the control. The mixture of low Cd and low PCP lessened Cd toxicity to plants, resulting in improved plant growth (by 144 %). Under the joint stress of the two contaminants, the ability of Cd uptake and translocation by P. australis was weak, and the BF and TF values were inferior to 1.0. A low proportion of the metal is found aboveground in comparison to roots, indicating a restriction on transport upwards and an excluding effect on Cd uptake. Thus, P. australis cannot be useful for phytoextraction. The removal rate of PCP increased significantly (70 %) in planted soil. Significant positive correlations were found between the DHA and the removal of PCP in planted soils which implied that plant root exudates promote the rhizosphere microorganisms and enzyme activity, thereby improving biodegradation of PCP. Based on results, P. australis cannot be effective for phytoremediation of soil co-contaminated with Cd and PCP. Further, high levels of pollutant hamper and eventually inhibit plant growth. Therefore, developing supplementary methods (e.g. exploring the partnership of plant–microbe) for either enhancing (phytoextraction) or reducing the bioavailability of contaminants in the rhizosphere (phytostabilization) as well as plant growth promoting could significantly improve the process of phytoremediation in co-contaminated soil.     

Influence of biowaste compost amendment on soil organic carbon storage under arid climate

Organic matter amendments have been proposed as a means to enhance soil carbon stocks on degraded soils, particularly under arid climate. Soil organic carbon (SOC) plays a critical role in terrestrial carbon cycling and is central to preserving soil quality. The effects of biowaste compost (BWC) on soil carbon storage were investigated. In addition, changes in soil organic matter (SOM) and even soil organic carbon (SOC) in BWC-amended soils following different applications were studied. The added BWC quantities were as followed: BWC/soil (weight/weight (w/w) respectively: 1/8, 1/4, and 1/2). The different BWC-amended soils were assessed during 180 days under arid ambient conditions and in comparison with control soil. Results showed a significant increase in SOM and SOC with relation to BWC quantities applied. This increase was relatively clear up to 120 days, after which decrease in SOM and SOC levels were observed. Furthermore, results showed improved microbiological activities of the amended soils in comparison with the control soil. This was reflected by the increase of the amended soils’ respirometric activities as cumulative carbon dioxide carbon (C-CO₂) as function of incubation time and also in terms of specific respiration expressed as C-CO₂/SOC ratios.

Implications: Mediterranean soils under arid climate such as Tunisian soils are poor in organic matter content. Biowastes are potential source for soil fertilization. Composting process is the best method for the stabilization of organic matter of diverse origins. The biowaste compost amendment improves the soil organic carbon storage and enhances the soil microbial activity.     

Effects of Soil Amendments at a Heavy Loading Rate Associated with Cover Crops as Green Manures on the Leaching of Nutrients and Heavy Metals from a Calcareous Soil

The potential risk of groundwater contamination by the excessive leaching of N, P and heavy metals from soils amended at heavy loading rates of biosolids, coal ash, N‐viro soil (1:1 mixture of coal ash and biosolids), yard waste compost and co‐compost (3:7 mixture of biosolids to yard wastes), and by soil incorporation of green manures of sunn hemp (Crotalaria juncea) and sorghum sudangrass (Sorghum bicolor × S. bicolor var. sudanense) was studied by collecting and analyzing leachates from pots of Krome very gravelly loam soil subjected to these treatments. The control consisted of Krome soil without any amendment. The loading rate was 205 g pot^? 1 for each amendment (equivalent to 50 t ha^? 1 of the dry weight), and the amounts of the cover crops incorporated into the soil in the pot were those that had been grown in it. A subtropical vegetable crop, okra (Abelmoschus esculentus L.), was grown after the soil amendments or cover crops had been incorporated into the soil. The results showed that the concentration of NO₃‐N in leachate from biosolids was significantly higher than in leachate from other treatments. The levels of heavy metals found in the leachates from all amended soils were so low, as to suggest these amendments may be used without risk of leaching dangerous amounts of these toxic elements. Nevertheless the level of heavy metals in leachate from coal ash amended soil was substantially greater than in leachates from the other treatments. The leguminous cover crop, sunn hemp, returned into the soil, increased the leachate NO₃‐N and inorganic P concentration significantly compared with the non‐legume, sorghum sudangrass. The results suggest that at heavy loading rates of soil amendments, leaching of NO₃ ^? could be a significant concern by application of biosolids. Leaching of inorganic P can be increased significantly by both co‐compost and biosolids, but decreased by coal ash and N‐viro soil by virtue of improved adsorption. The leguminous cover crop, sunn hemp, when incorporated into the soil, can cause the concentration of NO₃‐N to increase by about 7 fold, and that of inorganic P by about 23% over the non‐legume. Regarding the metals, biosolids, N‐viro soil and coal ash significantly increased Ca and Mg concentrations in leachates. Copper concentration in leachate was increased by application of biosolids, while Fe concentration in leachates was increased by biosolids, coal ash and co‐compost. The concentrations of Zn, Mo and Co in leachate were increased by application of coal ash. The concentrations of heavy metals in leachates were very low and unlikely to be harmful, although they were increased significantly by coal ash application.     

As(V) retention on soils and forest by-products and other waste materials

As(V) retention capacity is determined by means of adsorption/desorption trials performed for coarse and fine ground mussel shell, forest and vineyard soils with or without fine shell, pine wood ash, oak wood ash, pine sawdust and slate-processing fines. Pine ash shows the highest arsenic retention potential (with >97 % adsorption and ≤1 % desorption), followed by shell-amended forest soil (adsorption between 96 and 92 %), by un-amended forest soil (adsorption between 98 and 86 %) and by the amended vineyard soil (adsorption between 92 and 75 %). Sawdust is the material with the lowest arsenic retention capacity in most cases, with un-amended vineyard soil also showing poor results. In the case of oak ash, As(V) percentage adsorption becomes higher with increasing added arsenic concentrations, while this increase in added arsenic causes lower percentage adsorption in the case of slate fines. Regarding adsorption ability, As(V) adsorption data were fitted to Freundlich and Langmuir models, showing good fitting, with pine ash and shell-amended forest soil having the highest K _F values. In view of that, mussel shell amendment would be useful to increase arsenic retention on forest and vineyard soils, while pine ash could be used to retain arsenic even from wastewaters.     

Effect of organic amendments on the mobility of trace elements in phytoremediated techno-soils: role of the humic substances

The efficiency of aided phytostabilization using organic amendments such as ramial chipped wood (RCW) and composted sewage sludge (CSS) was studied on contaminated techno-soils, on nine experimental plots. The objective was to characterize the role of fulvic (FA) and humic acids (HA) on the mobilization of trace elements, specifically As, Cu, Mo, Pb and Zn. Results showed that the addition of CSS increased the total organic carbon and nitrogen content more than with RCW and as a result, the C/N ratio in the CSS soil was higher than in the RCW and non-amended (NE) soil, reflecting the high decomposition of soil organic matter in the CSS soil compared with the other soils. The RCW and CSS amendments increased the hydrogen index (HI) values and the oxygen index (OI) values compared with the NE soil, especially for the soil treated with CSS which contained more aliphatic than aromatic compounds. The addition of CSS to the techno-soil significantly increased the percentage of C _org associated with the HA fractions compared with the RCW and NE soils. The soil amended with CSS showed the highest E ₄/E ₆ ratio and the lowest E ₂/E ₃ ratio of FA. Zn and As were more abundant in the FA fraction than in the HA fraction, whereas Pb, Cu and Mo were more associated to HA than to FA in the treated and untreated soils, which may explain the difference in their mobility and availability.     

Phytoremediating a copper mine soil with Brassica juncea L., compost and biochar

The soils at a depleted copper mine in Touro (Galicia, Spain) are chemically degraded. In order to determine the effect of amendments and vegetation on the chemical characteristics of a mine soil and on the plant uptake of metals, a greenhouse experiment was carried out for 3 months. A settling pond soil was amended with different percentages of a compost and biochar mixture and vegetated with Brassica juncea L. The results showed that the untreated settling pond soil was polluted by Cu. Amendments and planting mustards decreased the pseudototal concentration of this metal, reduced the extreme soil acidity and increased the soil concentrations of C and TN. Both treatments also decreased the CaCl₂-extractable Co, Cu and Ni concentrations. However, the amendments increased the pseudototal concentration of Zn in the soil, provided by the compost that was used. The results also showed that mustards extracted Ni efficiently from soils, suggesting that B. juncea L. is a good phytoextractor of Ni in mine soils.     

Influence of fly ash aided phytostabilisation of Pb, Cd and Zn highly contaminated soils on Lolium perenne and Trifolium repens metal transfer and physiological stress

Due to anthropogenic activities, large extends of soils are highly contaminated by Metal Trace Element (MTE). Aided phytostabilisation aims to establish a vegetation cover in order to promote in situ immobilisation of trace elements by combining the use of metal-tolerant plants and inexpensive mineral or organic soil amendments. Eight years after Coal Fly Ash (CFA) soil amendment, MTE bioavailability and uptake by two plants, Lolium perenne and Trifolium repens, were evaluated, as some biological markers reflecting physiological stress. Results showed that the two plant species under study were suitable to reduce the mobility and the availability of these elements. Moreover, the plant growth was better on CFA amended MTE-contaminated soils, and the plant sensitivity to MTE-induced physiological stress, as studied through photosynthetic pigment contents and oxidative damage was lower or similar. In conclusion, these results supported the usefulness of aided phytostabilisation of MTE-highly contaminated soils.     

Amendment of arsenic and chromium polluted soil from wood preservation by iron residues from water treatment

An iron-rich water treatment residue (WTR) consisting mainly of ferrihydrite was used for immobilization of arsenic and chromium in a soil contaminated by wood preservatives. A leaching batch experiment was conducted using two soils, a highly contaminated soil (1033 mg kg⁻¹ As and 371 mg kg⁻¹ Cr) and slightly contaminated soil (225 mg kg⁻¹ As and 27 mg kg⁻¹ Cr). Compared to an untreated reference soil, amendment with 5% WTR reduced leaching in the highly contaminated soil by 91% for Cr and 98% for As. No aging effect was observed after 103 d. In a small field experiment, soil was mixed with 2.5% WTR in situ. Pore water was extracted during 3 years from the amended soil and a control site. Pore water arsenic concentrations in the amended soil were more than two orders of magnitude lower than in the control for the upper samplers. An increased release of arsenic was observed during winter in both fields, mostly in the deepest samplers. This is likely due to the formation of a pseudo-gley because of precipitation surplus. Stabilization of arsenic and chromium contaminated soil using WTR is a promising method but the transformation of ferrihydrite in soil proves a concern in case of waterlogged soils. Still the amendment minimized the leaching of arsenic, even in cases of seasonal releases.     

Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action

We evaluated wheat straw biochar produced at 450 °C for its ability to influence bioavailability and persistence of two commonly used herbicides (atrazine and trifluralin) with different modes of action (photosynthesis versus root tip mitosis inhibitors) in two contrasting soils. The biochar was added to soils at 0%, 0.5% and 1.0% (w/w) and the herbicides were applied to those soil-biochar mixes at nil, half, full, two times, and four times, the recommended dosage (H₄). Annual ryegrass (Lolium rigidum) was grown in biochar amended soils for 1 month. Biochar had a positive impact on ryegrass survival rate and above-ground biomass at most of the application rates, and particularly at H₄. Within any given biochar treatment, increasing herbicide application decreased the survival rate and fresh weight of above-ground biomass. Biomass production across the biochar treatment gradient significantly differed (p < 0.01) and was more pronounced in the case of atrazine than trifluralin. For example, the dose-response analysis showed that in the presence of 1% biochar in soil, the value of GR₅₀ (i.e. the dose required to reduce weed biomass by 50%) for atrazine increased by 3.5 times, whereas it increased only by a factor of 1.6 in the case of trifluralin. The combination of the chemical properties and the mode of action governed the extent of biochar-induced reduction in bioavailability of herbicides. The greater biomass of ryegrass in the soil containing the highest biochar (despite having the highest herbicide residues) demonstrates decreased bioavailability of the chemicals caused by the wheat straw biochar. This work clearly demonstrates decreased efficacy of herbicides in biochar amended soils. The role played by herbicide chemistry and mode of action will have major implications in choosing the appropriate application rates for biochar amended soils.     

Chemical amendment of pig slurry: control of runoff related risks due to episodic rainfall events up to 48 h after application

Losses of phosphorus (P) from soil and slurry during episodic rainfall events can contribute to eutrophication of surface water. However, chemical amendments have the potential to decrease P and suspended solids (SS) losses from land application of slurry. Current legislation attempts to avoid losses to a water body by prohibiting slurry spreading when heavy rainfall is forecast within 48 h. Therefore, in some climatic regions, slurry spreading opportunities may be limited. The current study examined the impact of three time intervals (TIs; 12, 24 and 48 h) between pig slurry application and simulated rainfall with an intensity of 11.0?±?0.59 mm h^?1. Intact grassed soil samples, 1 m long, 0.225 m wide and 0.05 m deep, were placed in runoff boxes and pig slurry or amended pig slurry was applied to the soil surface. The amendments examined were: (1) commercial-grade liquid alum (8 % Al₂O₃) applied at a rate of 0.88:1 [Al/ total phosphorus (TP)], (2) commercial-grade liquid ferric chloride (38 % FeCl₃) applied at a rate of 0.89:1 [Fe/TP] and (3) commercial-grade liquid poly-aluminium chloride (10 % Al₂O₃) applied at a rate of 0.72:1 [Al/TP]. Results showed that an increased TI between slurry application and rainfall led to decreased P and SS losses in runoff, confirming that the prohibition of land-spreading slurry if heavy rain is forecast in the next 48 h is justified. Averaged over the three TIs, the addition of amendment reduced all types of P losses to concentrations significantly different (p?<?0.05) to those from unamended slurry, with no significant difference between treatments. Losses from amended slurry with a TI of 12 h were less than from unamended slurry with a TI of 48 h, indicating that chemical amendment of slurry may be more effective at ameliorating P loss in runoff than current TI-based legislation. Due to the high cost of amendments, their incorporation into existing management practices can only be justified on a targeted basis where inherent soil characteristics deem their usage suitable to receive amended slurry.     

Influence of soil properties on heavy metal sequestration by biochar amendment: 1. Copper sorption isotherms and the release of cations

The amendment of carbonaceous materials such as biochars and activated carbons is a promising in situ remediation strategy for both organic and inorganic contaminants in soils and sediments. Mechanistic understandings in sorption of heavy metals on amended soil are necessary for appropriate selection and application of carbonaceous materials for heavy metal sequestration in specific soil types. In this study, copper sorption isotherms were obtained for soils having distinct characteristics: clay-rich, alkaline San Joaquin soil with significant heavy metal sorption capacity, and eroded, acidic Norfolk sandy loam soil having low capacity to retain copper. The amendment of acidic pecan shell-derived activated carbon and basic broiler litter biochar lead to a greater enhancement of copper sorption in Norfolk soil than in San Joaquin soil. In Norfolk soil, the amendment of acidic activated carbon enhanced copper sorption primarily via cation exchange mechanism, i.e., release of proton, calcium, and aluminum, while acid dissolution of aluminum cannot be ruled out. For San Joaquin soil, enhanced copper retention by biochar amendment likely resulted from the following additional mechanisms: electrostatic interactions between copper and negatively charged soil and biochar surfaces, sorption on mineral (ash) components, complexation of copper by surface functional groups and delocalized π electrons of carbonaceous materials, and precipitation. Influence of biochar on the release of additional elements (e.g., Al, Ca) must be carefully considered when used as a soil amendment to sequester heavy metals.     

Effect of EDTA and citric acid on phytoremediation of Cr- B[a]P-co-contaminated soil

Polycyclic aromatic hydrocarbons and heavy metals in the environment are a concern, and their removal to acceptable level is required. Phytoremediation, the use of plants to treat contaminated soils, could be an interesting alternative to conventional remediation processes. This work evaluates the role of single and combined applications of chelates to single or mixed Cr + benzo[a]pyrene (B[a]P)-contaminated soil. Medicago sativa was grown in contaminated soil and was amended with 0.3 g citric acid, 0.146 g ethylenediaminetetraacetic acid (EDTA), or their combination for 60 days. The result shows that in Cr-contaminated soil, the application of EDTA + citric acid significantly (p?<?0.05) decreased the shoot dry matter of M. sativa by 55 % and, as such, decreased the Cr removal potential from the soil. The soluble Cr concentration in single Cr or Cr + B[a]P-contaminated soil was enhanced with the amendment of all chelates; however, only the application of citric acid in Cr-contaminated soil (44 %) or EDTA and EDTA + citric acid in co-contaminated soil increased the removal of Cr from the soil (34 and 54 %, respectively). The dissipation of B[a]P in single B[a]P-contaminated soil was effective even without planting and amendment with chelates, while in co-contaminated soil, it was related to the application of either EDTA or EDTA + citric acid. This suggests that M. sativa with the help of chelates in single or co-contaminated soil can be effective in phytoextraction of Cr and promoting the biodegradation of B[a]P.     

The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings

A historically multi-metal contaminated soil was amended with biochars produced from different parts of rice plants (straw, husk and bran) to investigate how biochar can influence the mobility of Cd, Zn, Pb and As in rice seedlings (Oryza sativa L.). Rice shoot concentrations of Cd, Zn and Pb decreased by up to 98%, 83% and 72%, respectively, due to biochar amendment, though that of As increased by up to 327%. Biochar amendments significantly decreased pore water concentrations (C_pw) of Cd and Zn and increased that of As. For Pb it depended on the amendment. Porewater pH, dissolved organic carbon, dissolved phosphorus, silicon in pore water and iron plaque formation on root surfaces all increased significantly after the amendments. The proportions of Cd and Pb in iron plaque increased by factors 1.8-5.7 and 1.4-2.8, respectively; no increase was observed for As and Zn. Straw-char application significantly and noticeably decreased the plant transfer coefficients of Cd and Pb. This study, the first to investigate changes in metal mobility and iron plaque formation in rice plants due to amending a historically contaminated soil with biochar, indicates that biochar has a potential to decrease Cd, Zn and Pb accumulations in rice shoot but increase that of As. The main cause is likely biochar decreasing the C_pw of Cd and Zn, increasing the C_pw of As, and increasing the iron plaque blocking capacity for Cd and Pb.     

Potential Use of Olive-Waste Ash from Cogeneration Plants as a Soil Amendment

A greenhouse study was conducted to evaluate the potential use of olive-cake ash as a soil amendment, using pepper (Capsicum annuum, L. cv Italian sweet). Three soils of different pH (acidic, neutral and calcareous) were used. Treatments included a control (no fertilizer application), NPK fertilizer, and two ash-application rates that provided a complete dose (equivalent to the K₂O amount in the fertilizer) and a half dose (equivalent to half the K₂O amount in the fertilizer), respectively. The ash was effective in raising soil pH. Ash treatments increased the pepper (stems and leaves) dry matter yield over control; although these increases were lower than treatment including NPK. Application of ash significantly increased leaf P concentration and AB-DTPA extractable P in soil, especially in the acidic and neutral soils. Leaf K concentrations and readily and slowly available K forms in soils were affected positively by the addition of the ash. These results demonstrate that ash from the combustion of wet olive cake can be used as a beneficial organic soil amendment.     

Effect of green manure amendment on herbicide pendimethalin on soil

Manure amendment in agricultural practice can have a large effect on herbicide dissipation because the period of manure plowing is close to the period of herbicide application. In addition, manure amendment is among the frequently encountered options in ameliorating pesticide pollution. In this research, the dissipation of the herbicide pendimethalin was examined after amendment with two common green manures, Lupinus luteus (L) or Cosmos bipinnatus (C), for 110 days in pH 5.2 and 7.7 soils (Sankengtzu [Sk] and Erhlin [Eh] soil, respectively). The microbial activity and ecology changes were examined by using Biolog EcoPlate and denaturing gradient gel electrophoresis (DGGE). In Sk soil, the half-lives of pendimethalin with L, C, and blank treatment were 49.0, 54.9, and 62.2 days, respectively, whereas that in Eh soil they were 46.3, 52.6, and 34.8 days, respectively. Pendimethalin dissipated quickly in more neutral soil (Eh soil), but the addition of manure can only increase the dissipation rate in acidic soil (Sk soil), indicating that the amendment of manures exerted different effect in pendimethalin dissipation rates in different pH soils. The application of pendimethalin and/or manure altered the microbial community activity after 24 h of incubation. After 110 days, the microbial community activities in green manure–amended soil were more similar to that with blank than pendimethalin treatment in both types of soils. In comparison with treatment C, microbial communities were more similar between treatment L and blank, indicating the superior effect over pendimethalin on microbial communities when applying Lupinus luteus. The research showed that the application of herbicide pendimethalin changed soil microbial community, and the amendment of manures exerted different effect in pendimethalin dissipation rates in different pH soils. It is assumed that the change in dissipation rates was originated from the microbial community change after different manure amendment.     

Adsorption/Desorption of Copper by a Sandy Soil Amended with Various Rates of Manure,Sewage Sludge,and Incinerated Sewage Sludge

Organic amendments are sometimes applied to agricultural soils to improve the physical, chemical, and microbiological properties of the soils. The organic fractions in these soil amendments also influence metal reaction, particularly the adsorption and desorption of metals, which, in turn, determine the bioavailability of the metals and hence their phytotoxicities. In this study, a Quincy fine sandy (mixed, mesic, Xeric Torripsamments) soil was treated with 0 to 160 g kg^?1 rates of either manure, sewage sludge (SS), or incinerated sewage sludge (ISS) and equilibrated in a greenhouse at near field capacity moisture content for 100 days. Following the incubation period, the soil was dried and adsorption of copper (Cu) was evaluated in a batch equilibration study at either 0, 100, 200, or 400 mg L^?1 Cu concentrations in a 0.01M CaCl₂ solution. The desorption of adsorbed Cu was evaluated by three successive elutions in 0.01M CaCl₂. Copper adsorption increased with an increase in manure rates. At the highest rate of manure addition (160 g kg^?1 soil), Cu adsorption was two-fold greater than that by the unamended soil at all rates of Cu additions. With increasing rates of Cu additions, the adsorption of Cu decreased from 99.4 to 77.6% of Cu applied to the 160 g kg^?1 manure amended soil. The desorption of Cu decreased with an increase in rate of manure amendment. Effects of sewage sludge amendments on Cu adsorption were somewhat similar to those as described for manure additions. Likewise, the desorption of Cu was the least at the high rate of SS addition (160 g kg^?1), although at the lower rates there was not a clear indication of the rate effects. In contrast to the above two amendments, the ISS amendment had the least effect on Cu adsorption. At the highest rate of ISS amendment, the Cu adsorption was roughly 50% of that at the similar rate of either manure or SS amendments, across all Cu rates.