Addition Of Amendments Research Articles

Effects of phosphate-solubilizing bacteria Aspergillus flavus AF-LRH1 on promoting phosphorus solubilization, wheat growth and soil heavy metal remediation

Increasing nutrient supply level and eliminating pollution risk are essential to promote farmland soil use. In the soil-plant nutrition cycle, phosphorus is a limiting nutrient, toxic metals such as Cd and Pb are stress threats. Utilizing microorganisms as a bio-amendment could be a viable approach to enhance the cycling of soil phosphorus nutrients and immobilize Cd and Pb in the soil. This study involved the isolation of Aspergillus flavus AF-LRH1, a phosphate solubilizing fungal strain from soil. The strain exhibited the capacity to solubilize calcium phosphate, attaining a phosphorus concentration of 220.73 mg L−1 in the medium. High performance liquid chromatography analysis showed that AF-LRH1 produced a combination of organic acids (tartaric acid 260.7 mg L−1, fumaric acid 0.8 mg L−1, citric acid 911.9 mg L−1) to dissolve Ca3(PO4)2 by providing H+ ions. AF-LRH1 also utilizes NH4+ for the biosynthesis of amino acids and releases protons, which facilitate the dissolution of insoluble Ca3(PO4)2 and calcium phytate. Through these processes, calcium phosphate is partly converted into hydroxyapatite because of biological solubilization. AF-LRH1 strain showed the capability to recover phosphorus from various types of sludge-based solid residue by increasing the solubility of insoluble phosphate compounds for plant nutrient supply. In addition, the combining addition of AF-LRH1 strain and phosphate-containing amendments (calcium phosphate, sludge ash and biochar) benefited the decontamination of Pb and Cd contaminated soil. This finding confirmed the AF-LRH1 could be a promising environmental-friendly biofertilizer suitable for agricultural applications and bioremediation of heavy metal contaminated soil.

Response of Chemical Fertilisation on Six-year-old Oil Palm Production in Shambillo-Padre Abad- Ucayali

It was proposed to determine the response of chemical fertilization in the production of oil palm (Elaeis guineensis Jacq.) six years old in the area of Rio Negro Shambillo Padre Abad in order to have a sustainable and economic alternative of chemical fertilization in the field stage, which contributes to the survival of the palm and provides the necessary resistance against pests and diseases. A completely randomized block design (DBCA) was used with four repetitions and treatments, 96 plants / UE / treatment were used, the spacing was 9x9 in rows and plants. Results obtained indicate the treatments; T3 and T2 (16,54 – 15,48 kg / plant) obtained the highest averages by bunch weight, T1 and T3 (17,48 – 15,42 fruits / bunch) obtained the highest averages regarding number of fruit / bunch, T1 and T3 (13,93 – 11,59 to 45 cm ) obtained the highest averages for bunch length, T1 and T3 (7,33 – 5,52 cm) obtained the highest averages regarding fruit length, T1 and T3 (11.37 – 9.54 g) obtained the highest averages regarding fruit weight, T1 and T3 (10,46 – 10,37 kg) obtained the highest averages to yield per plant. The addition of chemical fertilizers or organic amendments increases the weight of the oil palm bunch, consequently the production in soils with medium, low fertility; chemical fertilization influences the number of clusters of oil palm produced on a given surface, any dose is used as an alternative to phosphorous fertilization in oil palm with a direct relationship between plant height and root length.

Toxic and non-toxic cyanobacterial biomass as a resource for sustainable agriculture: A lettuce cultivation experiment

Cyanobacteria represent a promising resource for sustainable agriculture, as they have demonstrated the ability to restore soil fertility even after death and decay. However, several cyanobacteria can also release secondary metabolites, such as cyanotoxins, which may compromise the quality of agricultural products and pose a potential risk to human health. Depending on the concentration of exposure, few studies reported deleterious effects on plant species when irrigated with cylindrospermopsin (CYN) contaminated water, impairing plant growth and leading to food product contamination, while other studies show promoting effects on plant yield. To evaluate the potential of cyanobacterial biomass (cyanotoxin-containing or not) as a sustainable resource for soil amendment, biostimulants or fertilizers for lettuce cultivation, a study was carried out that consisted of the culture of lettuce plants under controlled conditions, in soil: (1) with no extra nutrient addition (control) and supplemented with 0.6 g of freeze-dried Raphidiopsis raciborskii biomass of (2) a non-CYN-producing strain, (3) a CYN-producing strain, and (4) the same CYN-producing strain pasteurized. Results showed no significant differences in photosystem II efficiency with the amendment addition. On the contrary, shoot fresh weight significantly increased in lettuce plants grown with the cyanobacterial biomass addition, especially in condition (3). In addition, there were significant differences in mineral concentrations in lettuce leaves after the cyanobacterial biomass addition, such as K, Na, Ca, P, Mg, Mn, Zn, Cu, Mo, and Co. CYN accumulation was detected under conditions (3) and (4), with concentrations observed in descending order from roots > soil > shoot. Nevertheless, the CYN concentration in edible tissues did not exceed the WHO-proposed tolerable daily intake of 0.03 μg/kg/day. These findings suggest that incorporating cyanobacterial biomass as a soil amendment, biostimulant or fertilizer for lettuce cultivation, even with trace amounts of CYN (1–40 μg/g), may enhance plant yield without leading to cyanotoxin accumulation in edible tissues above the WHO-recommended tolerable daily intake.

Insight into the differential response of functional denitrifiers to novel formulated organic amendments in soybean agroecosystem

Fertilizer application has been known to cause substantial changes in the microbial composition of agricultural soil. Therefore, there is a need for more fertilizer management practices that will improve nitrogen (N) content, which is the key restrictive factor for microbial growth. To elucidate the characteristics of these fertilizers in the soil, samples were collected from a soybean field of control (S0) with no addition of organic amendment, biochar made from rice straw (S1), compost made from cattle manure and maize straw at a ratio of 5:1 (S2), composting S2 + 10 % S1 (S3), and mixture of S2 + 10 % S1 without composting (S4). The soil functional denitrifiers (nirS and nirK) were unravelled using Illumina high-throughput sequencing. It was observed that S3 (66.56 %) and S4 (61.14 %) increased the NO3−-N, while S2 increased the total Kjeldahl nitrogen (TKN) by 15.79 % compared to S0. OTU847_norank_p_environmental_samples in nirS and OTU112_unclassified_f_Bradyrhizobiaceae in nirK were the most abundant genera in S1-S4 while S2 and S3 had the highest unique OTUs in nirK and nirS communities, respectively. The canonical correspondence analysis (CCA) showed that NO2−-N and nitrate reductase (NIR) enzyme-shaped nirS and nirK denitrifiers. Also, from the structural equation model (SEM), TKN showed a higher negative significant effect on nirK alpha and beta diversities, while S4 showed the lowest positive network in nirS and nirK- denitrifiers. Meanwhile, Bradyrhizobium was observed as a common genus in the multivariate co-occurrence network in nirS- and nirK-type denitrifiers. This study provides the theoretical basis and technical support that single and combined fertilizers could influence nirS and nirK denitrifiers in soybean-grown soil.

A Critical Analysis of the UAE Federal Decree-Law No.: (38) of 2021 on the Protection of Copyrights and Neighboring Rights

Recently, by virtue of Federal Decree-Law No.: (38) of 2021, the United Arab Emirates has passed a new legislation for the protection of copyrights and neighboring rights; a legislation that is meant to replace the prior Copyrights and Neighboring Rights Law No.: (7) of 2002. In this regard, this new Decree-Law is consisted of Fifty-Three (53) Articles; hence, it is somewhat similar to the prior law, except for the addition of some new amendments for certain details as mentioned herein in this paper (e.g. Smart Applications are added to the list of Digital Works).For instance, pursuant to this new Decree-Law, it is now impermissible for the author to request cessation of the circulation of his digital works; and that is as an exception to his moral right to withdraw his work from circulation after its publication. In addition, this new Decree-Law has granted people with special needs the right to alter the published work, without prior permission of the author or his successor, so that those people may be capable of using those works in a way that is suitable to their conditions. Furthermore, the new Decree-Law has permitted the formation of a Grievances Committee at the Ministry of Economy, presided by a competent judge; and that is in order to hear all appeals submitted against decrees of the Ministry of Economy, concerning the rejection of works registration, the rejection of works' transcription or translation for scientific purposes, or any other decrees issued by the ministry concerning copyrights and neighboring rights. In this sense, the executive regulation of this new Decree-Law has been issued under No.: (47) of 2022, including Twenty (20) Articles, duly covering the following aspects and procedures: a) the regulation of works' collective management; b) the stated procedures for works registration; c) the legal actions concerning the financial rights of works; d) the stated procedures of mandatory licensing from the Ministry of Economy for the works' transcription or translation for scientific purposes; and e) the stated procedures of appeal against decrees of the Ministry of Economy before the Grievances Committee. The object of research is to critically examine the similarity between the Federal Decree-Law No.: (38) of 2021 on the Copyrights and Neighboring Rights and the previous Law No.: (7) of 2002 on the Copyrights and Neighboring Rights, and to identify the new changes brought by the new legislation. The study reveals that the new law limits the right of the author, granted certain rights to the people with special needs, and provision for formation of the Grievance Committee. The study recommends for the unification of all legislations that relate to intellectual property, and create a separate provision for each type of intellectual property.

Seed- and Foliar-Applied Iron Chelate Improves Performance, Physiological, and Biochemical Aspects of Black Cumin (Nigella sative) under Semi-Arid Conditions

The cultivation of medicinal plants plays a crucial role in promoting human health benefits. However, the production of these plants can be affected by drought conditions. This research aimed to investigate the impact of differing water status (non-drought and drought during the flowering to harvest stage) and various iron treatments on the performance of black cumin. The iron treatments included no iron as the control (nFe), no iron with seed hydro-priming (nFe + P), seed iron priming (pFe), seed iron priming with iron foliar spraying (pFe + sFe), and double iron foliar spraying (sFe + sFe). The purpose of these treatments was to assess the effect of iron application methods on plant response under different water conditions. The findings revealed that drought significantly reduced the levels of Chla (15%) and RWC (5.9%), plant height (7%), follicle number (16.7%), seed number (4.6%), 1000-seed weight (3.2%), and seed yield (30.1%). Additionally, drought increased the proline content (90.9%), electrolyte leakage (9.2%), and MDA levels (23.9%). Interestingly, applying iron amendments reduced electrolyte leakage and increased seed yield under both water conditions. The drought-induced increase in proline content was more pronounced in the nFe treatment than in the other treatments. The amount of MDA in the nFe and nFe + P treatments was significantly higher under drought conditions compared to non-drought conditions. In conclusion, the addition of iron amendments helps black cumin plants recover from the effects of drought and reduces damage to seed growth. This means that using both seed iron priming and iron foliar spraying can significantly improve yields. Alternatively, focusing on either seed iron priming or double iron foliar spraying can also boost black cumin production compared to not using iron amendments.

Evaluating Impacts of Biochar and Inorganic Fertilizer Applications on Soil Quality and Maize Yield Using Principal Component Analysis

A 2-year field experiment was conducted to test the effects of individual and co-application of biochar and inorganic fertilizer on soil quality using the principal component analysis (PCA) technique. The dry season field experiments were performed with biochar applied at 0 and 20 t ha−1, and fertilizer at 300 and 0 kg ha−1 (control). The factorial combinations of the above-mentioned treatments were subjected to irrigation at 60, 80, and 100% of irrigation amounts (IAs). Soil hydro-physical and chemical properties and grain yield were determined at harvest. Results from the PCA indicated that the soil total nitrogen (N) and moisture content (MC) were the soil properties mostly affecting the grain yield. The amendments’ effects on the soil physico-chemical properties and maize yield were in the order control < biochar < fertilizer < biochar + fertilizer. The derived comprehensive soil quality index (CSQI) from the PCA showed that the soil quality increased by 76, 100, and 200% in treatments individually applied with biochar, inorganic fertilizer, and the co-applications. This study therefore showed that the PCA revealed the actual dynamics in soil properties, in terms of the SQI upon the soil amendment addition, as well as their relationship with maize yield under different weather conditions.

Amendments promote Douglas-fir survival on Formosa Mine tailings.

While mining provides valuable metals and minerals to meet societal demands, it can cause environmental contamination from the residuals (i.e., tailings) of mining. Tailings are often acidic, laden with heavy metals, and lacking adequate nutrients and physical conditions for plant growth, precluding the establishment of plant cover to reduce the offsite movement of mining wastes. This paper describes a case study at the Formosa Mine in Douglas County, Oregon, where tailings were amended with a mixture of lime, biosolids, biochar, and microbial inoculum to facilitate establishment of Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco) seedlings. Results show that the tailings pH increased, and Douglas-fir seedlings survived and grew with these amendments. After 2years, pH did, however, decrease in some downslope locations and was associated with an increase in tree mortality. This suggests that tailings conditions should be monitored, and amendments should be reapplied as needed, particularly in areas receiving acidic runoff from unamended upslope tailings, until the seedlings are fully established. This study not only provides a prescription for the addition of biochar and other amendments to enhance plant growth for revegetation purposes in low-pH, metal-contaminated mine tailings, but it also demonstrates a method that can be used to address similar problems at other mine sites.

The Influence of Plow Types, Tillage Depth and Amendment Addition on the Mean Weight Diameter (MWD) of Clay Soil

The Influence of Plow Types, Tillage Depth and Amendment Addition on the Mean Weight Diameter (MWD) of Clay Soil

Zinc phytotoxicity and cationic micronutrients contents in quinoa as influenced by high Zn levels and soil amendments

Contamination of soils with heavy metals (HMs) is a serious concern due to the non-biodegradability and accumulation of these metals in living organism. The aim of this study was to evaluate the effectiveness of fish scale powder, chitin, and chitosan in reducing zinc (Zn) accumulation of quinoa grown on Zn-polluted soil. A 3*4 factorial greenhouse trial was conducted with three levels of Zn contamination (0, 100, and 200 mg kg−1) and four types of amendment (control, and 0.15% of each fish scale powder, chitin, and chitosan). The quinoa seeds were sown in soil treated with Zn contamination and amendments. Results showed that application of amendments especially chitosan increased shoot and root dry weight and greenness index of quinoa leaf. While high soil Zn levels decreased cationic micronutrients uptake in quinoa shoot, chitosan addition desirably enhanced cationic micronutrients uptake in quinoa shoot. Overall, amendment addition significantly decreased Zn concentration and uptake in plant; the highest decrease was observed following the application of chitosan. Although the application of high Zn levels significantly increased the values of phytoextraction efficiency, application of chitin and chitosan significantly decreased it. The value of translocation factor was lower than one, demonstrating that a large amount of Zn was stabilized in the root tissues, while a small amount of this metal was transferred to aboveground parts of quinoa. Results of this study revealed that fish scales derivatives were effective in preventing Zn toxicity and at the same time increasing cationic micronutrients contents of quinoa grown on HMs-polluted soil.

Optimizing the water-ecosystem-food nexus of avocado plantations

Climate change, food and water security and ecosystem sustainable management are tightly interlinked and require holistic approaches to achieve solutions that do not impact adversely one-another. The objective of this work was to conduct studies, collect data and assess the Water-Ecosystem-Food (WEF) nexus in avocado plantations in the Mediterranean region systematically to minimize the environmental footprint while maximizing the benefits for the farmer and the environment. The study includes two distinct experiments; the first addresses the impact of soil organic amendments addition to optimize the WEF nexus and the second monitors experimentally crop water needs and thus illustrates how irrigation practices aided by technology can reduce substantially water consumption. The results showed that organic amendments addition improves fertility, nutrient sequestration and structure but only had a weak effect on biodiversity by increasing the number of unique species. For the development of an efficient irrigation system it is necessary to determine the radius around the tree, the depth of the roots and the time required for the water to reach the active root zone to determine the amount and duration of irrigation. In this way sufficient water will be added to replenish the soil moisture deficit created due to the evapotranspiration. HYDRUS-1D model was used to simulate soil moisture and the hydrologic budget of an avocado tree located in Koiliaris river basin and confirm the percolation losses to groundwater. The results of this study showed that the actual irrigation needs of avocados in the Mediterranean is less than 2,000 m3/ha which is 75% less than what is recommended and could become the primary measure for the mitigation of climate change impacts especially in semi-arid regions such as the Mediterranean.

Unveiling ammonium concentration ranges that determine competition for mineral nitrogen among soil nitrogen transformations under increased carbon availability

Globally, approximately 50% of nitrogen (N) fertilizer applied in agricultural practices escapes into the environment, resulting in water and air pollution and ozone depletion. Soil N transformation processes determine the chemical form of N and the amount of the various N forms, controlling where N fertilizer goes and how much of it is lost. Therefore, a comprehensive understanding of soil N transformation responses to N fertilizer is critical for developing effective management strategies to improve soil N retention capacity and minimize soil N losses. Using 15N tracing techniques with acetylene inhibition, three ranges for ammonium concentration in fertilizer were identified (I: 14–16, II: 46–59, and III: 90–115 mg N kg−1, depending on type of organic materials added) that determine competition for mineral N among N transformation processes under increased carbon availability in an agricultural soil. Increasing ammonium concentration caused a shift from a nitrate assimilation-dominated (<I) to an equally ammonium assimilation- and nitrification-dominated (I-II) to nitrification-dominated (II-III), and finally to nitrification-predominant (>III) period in organic amendment addition treatments. Structural equation modeling revealed that ammonium addition inhibited soil nitrate assimilation by enhancing nitrification and ammonium assimilation, resulting in the shift. Consequently, the ratios of nitrification to ammonium assimilation and to gross N assimilation (nitrate assimilation + ammonium assimilation) increased significantly in response to elevated ammonium concentration with organic amendment addition, indicating lower N retention capacity and higher potential risks of N loss. Overall, we present a comprehensive picture of how concurrent gross N transformation processes interact to compete for mineral N in response to ammonium-forming fertilizer application, and demonstrate that nitrification and ammonium assimilation weaken the stimulating effect of organic amendment on nitrate assimilation with increasing ammonium concentration.

English

An incubation study investigated the decomposition patterns, microbial activities, soil aggregates distribution, and soil organic carbon (SOC) contents, using four crop residues; wheat (Triticum aestivum L.), rice (Oryza sativa L.), cotton (Gossypium hirsutum L.), and maize (Zea mays L.), at low and high rates (10 and 20 g kg–1). An average increase of about 35% in cumulative C-CO2 emissions and 26% in soil microbial biomass carbon (MBC) was observed at high residue rates as compared to low rates. A positive and strong correlation (0.96) was found between C-CO2 emissions and MBC, and the effect of residue quality on decomposition was found to be less at high rates. The relative reduction in C-CO2 emissions by adding rice residues may be due to their high silica content. Differences in extracellular enzyme activities (EEA) with different residues indicated the effect of residue quality on microbial activities. Cotton residues increased β-glucosidase and chitinase activities by 41 and 38%, respectively, at high rates than at low rates. High maize residues also markedly increased chitinase activity by 41%, implying higher N cycling and fungal prevalence. Acid phosphatase activity was found to increase by about 25 to 32% with high rice and wheat residues, respectively. Higher EEA at high residues input likely reflected the microbial nutritional limitations. Crop residues raised SOC content from 0.7 under control to 1.0% at low residues input but not at high input. Increased macro-aggregates fraction at high residues input may be attributed to higher microbial activities. In summary, high residues input can minimize residue biochemical quality’s effect on decomposition, with no further increase in SOC content. While a positive effect on the soil MBC, but not on the SOC content, was observed at high residue input, suggesting moderation in the additions of organic amendments is key for SOC buildup. Crop residues, added at 10 g kg–1, may help maintain a positive SOC balance in the arid agroecosystems by moderating higher microbial activities and soil respiration.

Integrated Management of Rhizome Rot and Wilt Disease Complex of Ginger (Zingiber officinale) – A Review

This review article focuses on integrated management options for ginger diseases, especially rhizome rot and wilt. We compiled the results of several strategies, including chemical treatments, cultural practices, soil solarization, organic additions, and biological management for rhizome rot and wilt disease complex of ginger. Effective approaches includes (i) raise the temperature by soil solarization, (ii) additions of soil amendments like wood sawdust, oil cakes, neem cakes that prevent soil pathogen and simultaneously improve soil health, (iii) cultural techniques such as soil selection, crop rotation and intercropping, (iv) biological control using Trichoderma species is another useful method to lower infestation and increase ginger yield, and (v) use of chemical control measures such as Ridomil MZ, Metalaxyl, and Streptomycin. The above-listed aspects can be integrated to develop integrated management strategies that aid in developing a treatment strategy for management for rhizome rot and wilt disease complex of ginger.

Evaluation of the trade-off between water use efficiency and nutrient use efficiency in two semiarid coniferous tree species growing on an organic amended metalliferous mine tailing substrate

We evaluated the ecophysiological responses of two semiarid coniferous tree species, Pinus halepensis and Tetraclinis articulata, growing on a nutrient-poor metalliferous mine tailings substrate to organic amendments (biochar and/or organic municipal waste). The trees were grown in mesocosms under irrigated conditions for 20 months. Then, a comprehensive characterization of soil and plant parameters (including stable isotopes) was carried out. Treatments containing municipal waste showed better soil fertility indicators (approximately 2-fold higher organic carbon and total nitrogen concentrations) and higher plant biomass (up to 5-fold higher) than unamended and only biochar treatments. Trees in most of the treatments exhibited leaf N/P ratios <14 indicating severe N limitation of plant growth. Metal uptake was below phytotoxic levels across all the treatments. Leaf δ13C values correlated positively with δ18O across treatments for both species indicating increasing water use efficiency with tighter stomatal regulation of water flux, and with T. articulata exhibiting tighter stomatal control (higher δ18O values) than P. halepensis. Trees in treatments containing only biochar did not differ in ecophysiological performance from those in the unamended treatments. In contrast, leaf stable isotopes revealed sharply increased of time-integrated photosynthetic activity (favoured by higher leaf N concentrations) combined with lower time-integrated stomatal conductance in the treatments containing municipal waste, indicating greatly enhanced water use efficiency in better nourished plants. Trade-offs between water use efficiency and nutrient (N and P) use efficiency were evident across treatments, with higher leaf nutrient concentrations associated with higher water use efficiency, at the cost of a lower nutrient use efficiency. These trade-offs were not impaired by the high metal concentrations of the tailings substrate, indicating that ecophysiological adjustments in response to changes in plant nutrient status promoted by the addition of organic amendments are critical for the adaptability of native tree species employed in the phytostabilisation of mine tailings.

Organic amendments improved soil properties and native plants’ performance in an Australian degraded land

Context Land degradation poses a substantial threat to both the sustainable environment and human health. Efforts towards rehabilitation and remediation often require addition of soil amendments and careful selection of plant species. Aims We assessed the effect of recycled organic amendments on improvement of soil physicochemical properties and performance of native plant species in an Australian degraded soil. Methods A glasshouse pot experiment investigated the effects of compost (CO), biochar (BC), and compost-biochar (COBC) mixture on performance of three native Australian plant species (Eucalyptus tereticornis (EU), Acacia leiocalyx (AC), and Banksia integrifolia (BA)) in a degraded soil. Key results Application of CO, BC, and COBC organic amendments increased soil dissolved organic carbon and microbial biomass carbon contents compared to the control treatment. COBC amendment increased nutrient retention and reduced CO2 emissions compared to CO amendment. BC amendment also resulted in low CO2 emissions similar to the control treatment, where no significant differences were observed. AC outperformed the EU and BA species in biomass production due to its leguminous nature, with amendment application had an insignificant effect on AC performance. Within the EU treatments, the COBC:EU demonstrated the highest biomass production, followed by CO:EU, BC:EU, and CK:EU, respectively. Conclusion All amendments exhibited overall improvements in soil and plant parameters, with more significant outcomes observed with COBC application. However, the observed improvements from biochar application were minimal in this short-term experiment, which may not have allowed for the manifestation of long-term benefits. Implications Further research is warranted to investigate the effects of compost and biochar amendments on diverse soil types and native plant species.

Potential of biochar and humic substances for phytoremediation of trace metals in oil sands process affected water

Oil sands process affected water (OSPW) is produced during bitumen extraction and typically contains high concentrations of trace metals. Constructed wetlands have emerged as a cost effective and green technology for the treatment of metals in wastewaters. Whether the addition of amendments to constructed wetlands can improve metal removal efficiency is unknown. We investigated the synergistic effects of carbon based amendments and wetland plant species in removal of arsenic, cadmium, cobalt, chromium, copper, nickel, and selenium from OSPW. Three native wetland species (Carex aquatilis, Juncus balticus, Scirpus validus) and two amendments (canola straw biochar, nano humus) were investigated in constructed wetland mesocosms over 60 days. Amendment effect on metal removal efficiency was not significant, while plant species effect was. Phytoremediation resulted in removal efficiencies of 78.61–96.31 % for arsenic, cadmium, and cobalt. Carex aquatilis had the highest removal efficiencies for all metals. Amendments alone performed well in removing some metals and were comparable to phytoremediation for cadmium, cobalt, copper, and nickel. Metals were primarily distributed in roots with negligible translocation to shoots. Our work provides insights into the role of plants and amendments during metal remediation and their complex interactions in constructed treatment wetlands.

Soil Amendment Combining Bentonite and Maize Straw Improves Soil Quality Cropped to Oat in a Semi-Arid Region

Soil amendments have been proposed as an effective way to enhance soil carbon stocks on degraded soils, particularly in dryland farming areas. Soil organic carbon (SOC) plays an important role in improving soil quality, and soil aggregates are known to be crucial in sequestering and protecting SOC. However, how aggregation and protection of SOC by aggregates respond to a single application of bentonite combined with maize straw remains unknown, especially in the sandy soil of a semi-arid region. A three-year field experiment with four treatments [no amendment (CK), maize straw amendment addition only (T1, 6 Mg ha−1), bentonite amendment addition only (T2, 18 Mg ha−1), and maize straw combined with bentonite amendment (T3, 6 Mg ha−1 maize straw plus 18 Mg ha−1 bentonite)] was conducted in the Loess Plateau of China to assess the effects of bentonite and maize straw on aggregation and SOC. The results indicated that soil bulk density decreased by 2.72–5.42%, and soil porosity increased by 3.38–8.77% with three years of T3 application, especially in the 20–40 cm layer, compared with CK. T3 increased the amount of C input, SOC stock, and SOC stock sequestration rate by 1.04 Mg ha−1 y−1, 0.84–1.08 Mg ha−1, and 0.49 Mg ha−1 y−1, respectively, and it increased the mass proportions and aggregate-associated C stock of &gt;0.25 mm aggregates by 1.15–2.51- and 1.59–2.96-fold compared with CK. Correlation analysis showed a positive correlation of total SOC stock with the C concentration of &gt;2 mm, 0.25–2 mm, and 0.053–0.25 mm aggregates. Aggregates of various sizes in sandy soils have the potential for greater SOC stock. Our findings suggest that the application of maize straw (6 Mg ha−1) combined with bentonite (18 Mg ha−1) would be an effective management strategy to enhance the bulk soil C pools by improving the soil structure and thereby improving soil fertility.

Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO2 nanoparticle-modified biochar

Pollution by heavy metals (HMs) has become a global problem for agriculture and the environment. In this study, the effects of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles on the immobilization and bioavailability of Pb, Cd, Zn, and Ni in soil under ryegrass (Lolium perenne L.) cultivation were investigated. The results of SEM–EDX, FTIR, and XRD showed that ZnO and MnO2 nanoparticles were successfully loaded onto biochar. The results showed that BC, BC@MnO2 and BC@ZnO treatments significantly increased shoots and roots dry weight of ryegrass compared to the control. The maximum dry weight of root and shoot (1.365 g pot−1 and 4.163 g pot−1, respectively) was reached at 1% BC@MnO2. The HMs uptake by ryegrass roots and shoots decreased significantly after addition of amendments. The lowest Pb, Cd, Zn and Ni uptake in the plant shoot (13.176, 24.92, 32.407, and 53.88 µg pot−1, respectively) was obtained in the 1% BC@MnO2 treatment. Modified biochar was more successful in reducing HMs uptake by ryegrass and improving plant growth than pristine biochar and can therefore be used as an efficient and cost effective amendment for the remediation of HMs contaminated soils. The lowest HMs translocation (TF) and bioconcentration factors were related to the 1% BC@MnO2 treatment. Therefore, BC@MnO2 was the most successful treatment for HMs immobilization in soil. Also, a comparison of the TF values of plant showed that ryegrass had a good ability to accumulate all studied HMs in its roots, and it is a suitable plant for HMs phytostabilization.

Phytostabilization of Heavy Metals and Fungal Community Response in Manganese Slag under the Mediation of Soil Amendments and Plants.

The addition of soil amendments and plants in heavy metal-contaminated soil can result in a significant impact on physicochemical properties, microbial communities and heavy metal distribution, but the specific mechanisms remain to be explored. In this study, Koelreuteria paniculata was used as a test plant, spent mushroom compost (SMC) and attapulgite (ATP) were used as amendments, and manganese slag was used as a substrate. CK (100% slag), M0 (90% slag + 5% SMC + 5% ATP) and M1 (90% slag + 5% SMC + 5% ATP, planting K. paniculata) groups were assessed in a pilot-scale experiment to explore their different impacts on phytoremediation. The results indicated that adding the amendments significantly improved the pH of the manganese slag, enhancing and maintaining its fertility and water retention. Adding the amendments and planting K. paniculata (M1) significantly reduced the bioavailability and migration of heavy metals (HMs). The loss of Mn, Pb and Zn via runoff decreased by 15.7%, 8.4% and 10.2%, respectively, compared to CK. K. paniculata recruited and enriched beneficial fungi, inhibited pathogenic fungi, and a more stable fungal community was built. This significantly improved the soil quality, promoted plant growth and mitigated heavy metal toxicity. In conclusion, this study demonstrated that the addition of SMC-ATP and planting K. paniculata showed a good phytostabilization effect in the manganese slag and further revealed the response process of the fungal community in phytoremediation.