Effects of nitrogen fertilization on the fate of high-risk antibiotic resistance genes in reclaimed water-irrigated soil and plants.

High-risk antibiotic resistance genes (ARGs) in reclaimed water-irrigated soil pose a potential threat to ecosystem and human health. Inorganic fertilization - including with nitrogen, a key ingredient in agricultural production - may affect the ARG profile in soil. However, little is known about nitrogen fertilization's influence on ARGs profiles in the soil-plant system. This study investigated the effects of different nitrogen fertilizer types (CO(NH2)2, NO3--N (NaNO3) and NH4+-N (NH4HCO3)) and different nitrogen fertilizer application rates (low, medium, high) on the distribution of high-risk ARGs in reclaimed water-irrigated soil and plants using quantitative PCR, high-throughput sequencing and metagenomic sequencing. Soil microcosms results revealed that nitrogen fertilization significantly affected the pattern of high-risk ARGs in soil, and also affected high-risk ARGs abundance and transfer capacity in plants. Compared with nitrogen fertilizer application rate, nitrogen fertilizer types significantly contributed to enhancing the soil resistome, with the order of CO(NH2)2 > NO3--N ≈ NH4+-N. The medium application of NO3--N and NH4+-N significantly reduced high-risk ARGs abundance in the leaf endophyte. Bacterial community mainly drove the variation of ARGs in nitrogen-fertilized soil-plant system, and class I integron and metal resistance genes (MRGs) also had direct effects on these high-risk ARGs. A similar high-risk ARGs pattern was also found in field plot experiments, and several dangerous pathogens were observed as the main high-risk ARGs potential hosts in nitrogen-fertilized soil. Based on an economic assessment, application of NH4+-N (NH4HCO3) could reduce costs by $1,312.83 ha-1 compared with NO3--N (NaNO3). These results showed that the more important role of nitrogen type might be an effective and economical way to control high-risk ARGs spread in soil-plant system under reclaimed water irrigation.

The introduction of influent sulfamethoxazole loads induces changes in the removal pathways of sulfamethoxazole in vertical flow constructed wetlands featuring hematite substrate.

High frequent detection of sulfamethoxazole (SMX) in wastewater cannot be effectively removed by constructed wetlands (CWs) with a traditional river sand substrate. The role of emerging substrate of hematite in promoting SMX removal and the effect of influent SMX loads remain unclear. The removal efficiency of SMX in hematite CWs was significantly higher than that in river sand CWs by 12.7-13.8% by improving substrate adsorption capacity, plant uptake and microbial degradation. With increasing influent SMX load, the removal efficiency of SMX in hematite CWs slightly increased, and the removal pathways varied significantly. The contribution of plant uptake was relatively small (< 0.1%) under different influent SMX loads. Substrate adsorption (37.8%) primarily contributed to SMX removal in hematite CWs treated with low-influent SMX. Higher influent SMX loads decreased the contribution of substrate adsorption, and microbial degradation (67.0%) became the main removal pathway. Metagenomic analyses revealed that the rising influent load increased the abundance of SMX-degrading relative bacteria and the activity of key enzymes. Moreover, the abundance of high-risk ARGs and sulfonamide resistance genes in hematite CWs did not increase with the increasing influent load. This study elucidates the potential improvements in CWs with hematite introduction under different influent SMX loads.

Global warming potential assessment under reclaimed water and livestock wastewater irrigation coupled with co-application of inhibitors and biochar.

The application of nitrification inhibitors (nitrapyrin) and urease inhibitors (N-(N-butyl) thiophosphoric triamide) under conventional water resources has been considered as an effective means to improve nitrogen utilization efficiency and mitigate soil greenhouse gas emissions. However, it is not known whether the inhibitors still have an inhibitory effect under unconventional water resources (reclaimed water and livestock wastewater) irrigation and whether their use in combination with biochar improves the mitigation effect. Therefore, unconventional water resources were used for irrigation, with groundwater (GW) control. Nitrapyrin and N-(N-butyl) thiophosphoric triamide were used alone or in combination with biochar in a pot experiment, and CO2, N2O, and CH4 emissions were measured. The results showed that irrigation of unconventional water resources exacerbated global warming potential (GWP). All exogenous substance treatments increased CO2 and CH4 emissions and suppressed N2O emissions, independent of the type of water, compared to no substances (NS). The inhibitors were ineffective in reducing the GWP whether or not in combination with biochar, and the combined application of inhibitors with biochar further increased the GWP. This study suggests that using inhibitors and biochar in combination to regulate the greenhouse effect under unconventional water resources irrigation should be done with caution.

[Effects of Foliar Application of Silicon Fertilizers on Phyllosphere Bacterial Community and Functional Genes of Paddy Irrigated with Reclaimed Water].

Agricultural utilization of reclaimed water is considered to be an effective way to solve water shortage and reduce water environmental pollution. Silicon fertilizer can improve crop yield and quality and enhance crop resistance. The effect of foliar spray with silicon fertilizer on phyllosphere microbial communities remains lacking. In this study, a pot experiment was conducted to explore the effects of different types of silicon fertilizer on the composition and diversity of a phyllosphere bacterial community and the abundances of related functional genes in rice irrigated with reclaimed water. The results showed that Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, and Verrucomicrobiota dominated the phyllosphere bacteria of rice. The relative abundance of Bacillus was higher than that of other treatments in RIS3. Reclaimed water irrigation significantly increased the relative abundances of the potential pathogens Pantoea and Enterobacter. The unclassified bacteria were also an important part of the bacterial community in the rice phyllosphere. Bacillus, Exiguobacterium, Aeromonas, and Citrobacter were significantly enriched by silicon fertilizer treatments. Functional prediction analysis showed that indicator species were mainly involved in metabolism and degradation functions, and the predicted functional groups of phyllosphere bacteria were attributed to chemoheterotrophy, aerobic chemoheterotrophy, nitrate reduction, and fermentation. Quantitative PCR results showed that AOA, AOB, and nifH genes were at low abundance levels in all treatments, and nirK genes was not significantly different among treatments. These results contribute to the in-depth understanding of the effects of foliar spray silicon fertilizer on the bacterial community structure and diversity of rice phyllosphere and provide a theoretical basis for the application of silicon fertilizer in reclaimed water irrigation agriculture.

Effect of the Lipoxin Receptor Agonist BML-111 on Cigarette Smoke Extract-Induced Macrophage Polarization and Inflammation in RAW264.7 Cells.

Background: Macrophages are known to play a crucial role in the chronic inflammation associated with Chronic Obstructive Pulmonary Disease (COPD). BML-111, acting as a lipoxin A4 (LXA4) receptor agonist, has shown to be effective in protecting against COPD. However, the precise mechanism by which BML-111 exerts its protective effect remains unclear. Methods: In order to establish a cell model of inflammation, cigarette smoke extract (CSE) was used on the RAW264.7 cell line. Afterwards, an Enzyme-linked immunosorbent assay (ELISA) kit was employed to measure concentrations of tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1ß), interleukin-18 (IL-18), and interleukin-10 (IL-10) in the cell supernatants of the RAW264.7 cells.In this study, we examined the markers of macrophage polarization using two methods: quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. Additionally, we detected the expression of Notch-1 and Hes-1 through Western blotting. Results: BML-111 effectively suppressed the expression of pro-inflammatory cytokines TNF-α, IL-1ß, and IL-18, as well as inflammasome factors NLRP3 and Caspase-1, while simultaneously up-regulating the expression of the anti-inflammatory cytokine IL-10 induced by CSE. Moreover, BML-111 reduced the expression of iNOS, which is associated with M1 macrophage polarization, and increased the expression of Arg-1, which is associated with M2 phenotype. Additionally, BML-111 downregulated the expression of Hes-1 and the ratio of activated Notch-1 to Notch-1 induced by CSE. The effect of BML-111 on inflammation and macrophage polarization was reversed upon administration of the Notch-1 signaling pathway agonist Jagged1. Conclusion: BML-111 has the potential to suppress inflammation and modulate M1/M2 macrophage polarization in RAW264.7 cells. The underlying mechanism may involve the Notch-1 signaling pathway.

[Effects of Soil Amendments on the Bacterial Diversity and Abundances of Pathogens and Antibiotic Resistance Genes in Rhizosphere Soil Under Drip Irrigation with Reclaimed Water].

Due to reclaimed water, irrigation can cause human health and environmental risks. Soil amendments are applied to reveal the abundance of pathogens and antibiotic resistance genes in rhizosphere soil irrigated by reclaimed water and to better understand the effects of environmental factors on the rhizosphere soil bacterial composition, which has guiding significance for the reasonable use of soil amendments. In this study, the effects of biochar, bioorganic fertilizer, humic acid, loosening soil essence, and corn vinasse on bacterial community diversity and certain gene abundances in rhizosphere soil under drip irrigation with reclaimed water were studied using high-throughput assays and quantitative PCR. The results showed that biochar significantly increased pH, organic matter, and total nitrogen contents in the rhizosphere soil. The corn vinasse significantly decreased soil pH and increased the contents of total nitrogen and total phosphorus but significantly increased the soil EC value (P<0.05). The effects of the five soil amendments on the α-diversity of rhizosphere bacteria were not significantly different. The bacterial community structure and diversity of rhizosphere bacteria were similar at different taxonomic levels, but their relative abundance was different. α-Proteobacteria, γ-Proteobacteria, Bacteroidia, Actinobacteria, Acidimicrobiia, and Anaerolineae were the dominant bacteria in all treatments. The dominant genera consisted of Pseudomonas, Sphingobium, Sphingomonas, Cellvibrio, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Flavobacterium, and Algoriphagus (relative abundance>1%). Correlation analysis of environmental factors showed that the composition of the rhizosphere bacterial community was strongly correlated with pH, EC, total nitrogen, and total phosphorus content. The abundances of pathogenic bacteria and antibiotic resistance genes were 103-107 copies·g-1 and 104-108 copies·g-1, respectively. There were significant differences in the detection levels of pathogens and antibiotic resistance genes. Bioorganic fertilizer, loosening soil essence, and corn vinasse significantly increased the abundances of some antibiotic resistance genes, whereas humic acid and corn vinasse significantly decreased the abundances of Pseudomonas syringae, Ralstonia solanacearum, and total coliforms (P<0.05). A significant correlation was found between pathogens (Arcobacter, Bacillus cereus, Pantoea agglomerans, and Fecal bacteroidetes) and antibiotic resistance genes (tetA, tetB, tetO, tetQ, sul1, ermB, and ermC). In conclusion, while monitoring pathogens and antibiotic resistance genes in the agricultural environment under reclaimed water irrigation, attention should be paid to the rational application of soil amendments to avoid exacerbating the spread of biological contamination.

Reduction effect of individual N, P, K fertilization on antibiotic resistance genes in reclaimed water irrigated soil.

The transfer of antibiotic resistance genes (ARGs) in soil under reclaimed water irrigation poses a potential environmental risk. Regulation of NPK fertilizer could influence the behavior of bacterial communities, mobile genetic elements (MGEs), and soil properties, which determine the fate of ARGs. To identify the key element in NPK fertilizer and realize efficient regulation, we explored the effect of individual N, P, K fertilization on ARG variation in tomato rhizosphere and bulk soils. Compared with an unfertilized treatment, N fertilization resulted in greater decreases in the abundance of ARGs (decreases of 24.06%-73.09%) than did either P fertilization (increases of up to 35.84%, decreases of up to 58.80%) or K fertilization (decreases of 13.47%-72.47%). The influence of different forms of N (CO(NH2)2, NaNO3, and NH4HCO3), P (Ca(H2PO4)2 and CaMgO4P+), and K (KCl and K2(SO4)) fertilizers was also investigated in this study, and showed the influence of NaNO3, CaMgO4P+, and K2(SO4) on reducing ARGs abundance was greater in different types of N, P, K fertilizers. Bacterial communities showed the strongest response to N fertilization. The reduced bacterial diversity and abundance of ARG-host and non-host organisms explained the decline of total ARG abundance in soil. In soils fertilized with either P or K, the effect of soil properties, especially total nitrogen and pH, on ARG variation was greater than that of bacterial community and MGEs. These results suggest that N regulation of in NPK fertilizer may be an effective way to reduce the risks of ARGs in soil associated with reclaimed water irrigation.

Removal effects of different emergent-aquatic-plant groups on Cu, Zn, and Cd compound pollution from simulated swine wastewater.

Aquatic plants play effective in removing heavy metal (HM) as a prominent factor of bioremediations, however, there are still knowledge gaps in species selection and configuration for high removal efficiency (RE) of compound HM and ornamental value. In this study, seven emergent-aquatic-plant species were configured into seven groups and planted in a simulated swine wastewater (SW) with Cu, Zn, and Cd for 75 days in summer. REs of Cu, Zn, and Cd were 45.06-86.93%, 42.40-87.22%, and 73.85-85.52% at day 75, respectively. Higher REs were observed from day 30-45 for Cu and Zn, whereas days 15-30 for Cd. The synergistic removal of Zn and Cu or Zn and Cd was almost observed (p < 0.05). The configuration of G5 (S. tabernaemontani, I. sibirica, and P. cordata) was generally efficient roles in the removal at day 45, with REs of 85.14%, 87.06%, and 83.56% for Cu, Zn, and Cd, respectively. The dry weight of roots, water NH4+-N, temperature, pH, and dissolved oxygen acted on heavy-metal removal. During days 45-75, concentrations of Cu, Zn, and Cd in G5 were 0.52-0.66, 0.54-0.65, and 0.23-0.33 mg L-1. The former two were below the limits of Grade Ⅱ (1.0 mg L-1) and the latter was above the limits of Grade Ⅴ (0.1 mg L-1; GB3838-2002). Thus, G5 could be optimal for Cu and Zn removal from simulated SW, however, efficient Cd removal is required to ensure efficient SW recycling.

Ryegrass (Lolium multiflorum L.) and Indian mustard (Brassica juncea L.) intercropping can improve the phytoremediation of antibiotics and antibiotic resistance genes but not heavy metals.

Lolium multiflorum and Brassica juncea display phytoremediation potential for heavy metals and antibiotics pollution. However, there is limited understanding of their function in removing combined pollutants (heavy metals, antibiotics and antibiotic resistance genes (ARGs)) under different cropping patterns. Sole cropping had little effect on heavy metals, but reduced antibiotics by 2.46%-84.88% and increased ARGs by 15.96%-33.82%. Intercropping was more beneficial to soil remediation and plant accumulation of L. multiflorum, and further increased the remediation of antibiotics by 2.38%-54.40%. Members of phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) were mainly responsible for most antibiotics removal. Compared with sole cropping, intercropping reduced more ARGs abundance in rhizosphere soil for L. multiflorum (20.43%) and in bulk soil for B. juncea (23.22%). Mobile genetic elements (MGEs) played a significant role in the variation of ARGs. Further, sample type showed a higher indirect negative impact on ARGs by mainly affecting soil properties and bacterial community, and the co-occurrence between the bacterial community and ARGs in bulk soil was more complex than that in rhizosphere soil. Together these results suggest that phytoremediation of combined soil pollution was positive but limited, and intercropping resulted in enhanced removal efficiency when compared with sole cropping.

[Effects of Selected Biochars Application on the Microbial Community Structures and Diversities in the Rhizosphere of Water Spinach (Ipomoea aquatica Forssk.) Irrigated with Reclaimed Water].

The utilization of reclaimed water is one of the most important ways of alleviating the shortage of water resources for agricultural irrigation. As an effective disposal method for biomass waste, biochar has been widely used in the improvement and remediation of agricultural environments. However, few studies have been performed on the effects of biochar application on microbial community structures and pathogen abundances in rhizosphere soils irrigated with reclaimed water. Based on a pot experiment, high throughput sequencing technology and quantitative polymerase chain reaction (PCR) methods were used to investigate the effects of different biochars on the microbial community structure and diversity and pathogen abundance of rhizosphere soils irrigated with reclaimed water. The results showed that four different types of biochars had different effects on the soil nutrient status. Rice hull-derived biochar and rice straw-derived biochar resulted in significantly increased soil pH with reclaimed water irrigation, while peanut shell-derived biochar, rice straw-derived biochar, and wheat straw-derived biochar significantly increased EC values (P<0.05). The Sobs index, Shannon index, and Chao1 index of bacterial community in the rhizosphere soil significantly increased with rice straw-derived biochar treatment, while the Simpson index significantly decreased by adding peanut shell-derived biochar, rice hull-derived biochar, and wheat straw-derived biochar (P<0.05). There were differences in the relative abundances of bacterial communities in rhizosphere soils under different treatments. The dominant taxonomic groups at the phylum level were Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, and Acidobacteria. The dominant genera included Pseudomonas, Rheinheimera, Arthrobacter, Sphingomonas, and Aeromonas (relative abundance>5%). Redundancy (RDA) and heatmap analyses showed that the diversities and compositions of bacterial communities in rhizosphere soils in different treatments were closely related to soil EC values, organic matter, total nitrogen, and cadmium contents. Biochar application had no significant effect on the abundances of Aeromonas hydrophila and Bacillus cereus. Rice straw-derived biochar and peanut shell-derived biochar could significantly reduce the γ-Proteobacteria, while rice hull-derived biochar and wheat straw-derived biochar could significantly reduce the relative abundance of AOA (P<0.05). In conclusion, there were no obvious negative effects observed from reclaimed water irrigation on soil quality. Biochar application not only significantly improved the physicochemical properties of the soil, but also impacted the bacterial community structure and the abundance of the functional bacteria in the rhizosphere soil, which was closely related to the soil properties.

[Effect of Different Reclaimed Water Irrigation Methods on Bacterial Community Diversity and Pathogen Abundance in the Soil-Pepper Ecosystem].

Reclaimed water is considered to be a reasonable and sustainable alternative water resource to improve water resource layout and mitigate the shortage of traditional water resources. Its use in irrigation will cause changes in the microbial community structure and opportunistic pathogen abundance in soils and crops, but few studies have been conducted on this subject. Peppers were used as the research subjects, and the treatments were direct irrigation of reclaimed water, mixed irrigation with freshwater and reclaimed water, rotated irrigation with freshwater and reclaimed water, with potable water irrigation as the control. The effects of different irrigation methods of reclaimed water on the soil physicochemical properties were analyzed through a pot experiment. Furthermore, changes in bacterial community and opportunistic pathogen abundance in pepper fruit and the rhizosphere under reclaimed water irrigation conditions were investigated based on high-throughput sequencing technology and quantitative PCR methods. The results showed that direct irrigation with reclaimed water increased soil EC and decreased soil pH. 16S rDNA high-throughput sequencing showed that Proteobacteria, Bacteroides, Actinobacteria, and Firmicutes were present in both pepper fruit and the rhizosphere at phylum level, and the most dominant genera (Pantoea, Pseudomonas, Sphingomonas, Sphingopyxis, Luteimonas, and Mariniflexile) were greatly affected by reclaimed water irrigation methods. Quantitative PCR results indicated that the influence of reclaimed water irrigation on the distribution and abundance of pathogenic bacteria in the soil-pepper system was different, and the abundance of Legionella spp. in pepper fruit and Pseudomonas syringae in the rhizosphere increased with reclaimed water irrigation. Our results indicated that the reclaimed water was suitable for agricultural irrigation, but different reclaimed water irrigation methods may introduce different degrees of microbial contamination. In addition, attention must be given to some opportunistic pathogens and phytopathogens.

Reducing water use by alternate-furrow irrigation with livestock wastewater reduces antibiotic resistance gene abundance in the rhizosphere but not in the non-rhizosphere.

Livestock wastewater is rich in nutrients but may contain antibiotics and antibiotic resistance genes (ARGs). Their discharge to watercourses or soil may result in proliferation of ARGs. Irrigation with wastewater appears to be the most feasible option of disposing of it. One efficient irrigation technology used in arid regions is alternate-furrow irrigation (AFI) by alternately drying part of the plant roots for a prolonged period to physiologically reduce transpiration without compromising yield. However, the extent to which AFI with wastewater influences the concentration of antibiotics and spread of ARGs in soil is poorly understood. The purpose of this paper is to investigate how AFI using swine wastewater alters antibiotic kinetics and ARGs abundance under different irrigation rates, using pepper as the model plant. We examined three AFI treatments using 50%, 65% and 80% of the amount of water employed in sufficient conventional furrow irrigation. Each treatment had a groundwater irrigation control. The results showed that antibiotic concentrations and relative ARGs abundance in the top 20 cm of soil did not increase with the irrigation amount, although they were higher than those in the groundwater-irrigated soils. The relative ARGs abundance in the soil was modulated by irrigation amount and reducing the irrigation amount in AFI reduced ARGs dispersion only in rhizosphere. When the soil moisture was close to field capacity, ARGs were more abundant in rhizosphere than in non-rhizosphere, possibly because the rhizosphere is rich in microbes and increasing antibiotic concentrations due to an increase in irrigation rate favors antibiotic-resistant microbiome in competing for substrates. These, however, were not mirrored in the relative ARGs abundance in the roots. These results have important implications as it revealed that reducing the input of antibiotics and ARGs into soil with AFI does not necessarily reduce ARGs proliferation.

Peanut-Shell Biochar and Biogas Slurry Improve Soil Properties in the North China Plain: A Four-Year Field Study.

Biochar and biogas slurry have been proved to improve the quality of some soil types, but the long-term effects on fluvo-aquic soil are not fully understood. This study aimed to compare the continuity effects of peanut-shell biochar and biogas slurry on the physicochemical properties, microbial population size, and enzyme activities of fluvo-aquic soil. We conducted a four-year field experiment of winter wheat-summer maize rotation in the North China Plain. Along with equal nitrogen inputs, three treatments were applied-conventional fertilizers, peanut-shell biochar, and hoggery biogas slurry-after which various soil quality indicators were compared. Compared with those of control, both biochar and biogas slurry increased the soil total nitrogen and organic matter content, and improved soil aggregation, microbial biomass, and actinomycetes. Biogas slurry decreased soil pH and improved urease and protease activities. With biochar and biogas slurry treatments, wheat yield increased by 8.46% and 23.47%, and maize yield by 18% and 15.46%, respectively. Biogas slurry increased the content of crude protein and starch in the grains. Both biogas slurry and peanut-shell biochar improved fluvo-aquic soil nutrient content, water-stable macroaggregates, and microbial population, which might be related to their high nutrient content, large specific surface area, adsorption capacity, and functional groups. Biogas slurry generally exhibited stronger effects than biochar probably because of its richness in nutrients and bioactive substances.

Amendment soil with biochar to control antibiotic resistance genes under unconventional water resources irrigation: Proceed with caution.

The spread of antibiotic resistance genes (ARGs) has become a cause for serious concern because of its potential risk to public health. The use of unconventional water resources (e.g., reclaimed water or piggery wastewater) in agriculture to relieve groundwater shortages may result in an accumulation of ARGs in soil. Biochar addition has been proven to be a beneficial method to alleviate the pollution of ARGs in manure-amended soil. However, the role of biochar on ARGs in soil-plant systems repeatedly irrigated with unconventional water resources is unknown. Under reclaimed water or piggery wastewater irrigation, rhizobox experiments using maize plants in soil amended with biochar were conducted to investigate the variation of typical ARGs (tet and sul genes) in soil-plant systems during a 60-day cultivation, and ARGs was characterized by high-throughput qPCR with a 48 (assays) × 108 (samples) array. Only piggery wastewater irrigation significantly increased the abundance of ARGs in rhizosphere and bulk soils and root endophytes. Following 30-day cultivation, the abundance of ARGs in soil was significantly lower due to biochar addition. However, by day 60, the abundance of ARGs in soil supplemented with biochar was significantly higher than in the control soils. Antibiotics, bio-available heavy metals, nutrients, bacterial community, and mobile gene elements (MGEs) were detected and analyzed to find factors shaping ARGs dynamics. The behavior of ARGs were associated with antibiotics but not with bio-available heavy metals. The correlation between ARGs and available phosphorus was stronger than that of ARGs with total phosphorus. MGEs had good relationship with ARGs, and MGEs shifts contributed most to ARGs variation in soil and root samples. In summary, this study provides insights into potential options for biochar use in agricultural activities.

Amending the seedling bed of eggplant with biochar can further immobilize Cd in contaminated soils.

Untreated municipal sewage is a potential source of Cd but has been used for irrigating vegetables in many countries in recent years. In growing vegetables and fruits in greenhouses, seedling breeding method is generally used in which the seedlings are transplanted into soils together with their seedling culture. Biochar has been increasingly used to amend soils contaminated by heavy metals, but there are few studies on the effectiveness of different ways of applying the biochar. In this paper, we investigated the efficacy of immobilizing Cd by amending eggplant seedling bed with biochar before transplanting them to biochar-amended soil contaminated by Cd. The results showed that, in comparison with traditional seedling method (without adding biochar), amending the seedling bed by biochar not only had a positive effect on plant growth and production, but further reduced the Cd concentration in the roots, shoots and the fruits by 12.2%, 12.5% and 18.5%, respectively. Furthermore, it increased the pH in rhizosphere to 8.83, reduced the exchangeable Cd concentration in soil by 28.6%, and decreased the Cd bio-accumulation factor from 0.36 to 0.32. Phytochelatin synthesis could be induced when plants are exposed to Cd and it has been used in the literature as a biomarker for evaluating metal toxicity. Our results showed that the seedling culture amended with biochar reduced phytochelatin synthesis in both roots and shoots. It can therefore be concluded that amending the eggplant seedlings bed with biochar can further enhance the effectiveness of remediating Cd contamination in soil after transplanting the plants into soil also amended with biochar. CAPSULE ABSTRACT: We found a new method to further immobilize Cd in contaminated soils by amending the seedling bed with biochar.

[Influences of different kinds of water retentive agents on water use efficiency and root mor- phology of winter wheat].

The effects of 5 different kinds of water retentive agents at 2 application levels on yield, water use efficiency and root morphology of winter wheat were studied through field experiments. The results showed that there were significant differences in tiller number, flag leaf area, yield and water use efficiency (WUE) among the water retentive agent treatments of different varieties and application levels. Compared with the control, the yield increased by 1.3%-7.9%, and the WUE increased from 17.1 kg · hm⁻² · mm⁻¹ to 18.0-20.7 kg · hm⁻² · mm⁻¹ under these 5 different kinds of water retentive agent treatments. The influences of water retentive agents on average root diameter, total root length and total root surface of winter wheat all reached a significant level. The total root length increased by 3.7%-19.1% and 6.3%-27.3%, and the total root surface area increased by 6.5%-21.7% and 2.9%-18.5% in the 0-20 and 20-40 cm soil layers, respectively. The root morphology characteristics were significantly positively correlated with both yield and WUE of winter wheat. The compound water retentive agent of acrylamide/inorganic mineral had the most significant influence on the increase of WUE and the promotion of root growth of winter wheat.

[Effects of elevated CO2 on the Cd uptake and root morphology of different rice varieties under cadmium stress].

A hydroponic experiment was conducted to study the effects of elevated CO2 on the Cd uptake and root morphology of rice varieties Rongyou-398 (RY) and Yueza-889 (YZ) under different levels of Cd stress. Low levels (5, 10, and 20 micromol x L(-1)) Cd stress increased the biomass of the two rice varieties significantly, while high levels (> 50 micromol x L(-1)) Cd stress was in adverse. Elevated CO2 increased the varieties dry biomass significantly, and increased the stem Cd concentration of YZ but decreased that of RY. Under the stress of 5-200 micromol Cd x L(-1), elevated CO2 increased the proportion of active root length in total root length of YZ but decreased that of RY, which could be one of the main reasons for the difference in the Cd uptake of the two varieties under Cd stress.

[Effects of alternate partial root-zone subsurface drip irrigation on potato yield and water use efficiency].

Field experiment was conducted to investigate the effects of alternate partial root-zone subsurface drip irrigation (APRSDI) on the physiological responses, yield, and water use efficiency of potato. Compared with conventional drip irrigation (CDI), APRSDI had less negative effects on the potato leaf photosynthesis rate (P(n)), but decreased the transpiration rate and stomatal conductance significantly. The slightly higher P(n) under CDI was at the expense of consuming more water. No significant difference was observed in the potato yield under APRSDI and CDI, but APRSDI saved the irrigation amount by 25.8% and increased the irrigation water use efficiency and total water use efficiency by 27.5% and 15.3%, respectively, suggesting that APRSDI would be a feasible water-saving irrigation technique for the planting of potato.