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In this paper, a highly copper-resistant fungal strain NT-1 was characterized by morphological, physiological, biochemical, and molecular biological techniques. Physiological response to Cu(II) stress, effects of environmental factors on Cu(II) biosorption, as well as mechanisms of Cu(II) biosorption by strain NT-1 were also investigated in this study. The results showed that NT-1 belonged to the genus Gibberella , which exhibited high tolerance to both acidic conditions and Cu(II) contamination in the environment. High concentrations of copper stress inhibited the growth of NT-1 to various degrees, leading to the decreases in mycelial biomass and colony diameter, as well as changes in morphology. Under optimal conditions (initial copper concentration: 200 mg L −1 , temperature 28 °C, pH 5.0, and inoculum dose 10%), the maximum copper removal percentage from solution through culture of strain NT-1 within 5 days reached up to 45.5%. The biosorption of Cu(II) by NT-1 conformed to quasi-second-order kinetics and Langmuir isothermal adsorption model and was confirmed to be a monolayer adsorption process dominated by surface adsorption. The binding of NT-1 to Cu(II) was mainly achieved by forming polydentate complexes with carboxylate and amide group through covalent interactions and forming Cu-nitrogen-containing heterocyclic complexes via Cu(II)-π interaction. The results of this study provide a new fungal resource and key parameters influencing growth and copper removal capacity of the strain for developing an effective bioremediation strategy for copper-contaminated acidic orchard soils.

The mineralization of nitrogen in apple orchard soil will increase the soil supply. An incubation study to test the soil potential and the validity of analytical methods was conducted at 3, 8, 15, and 20 °C for up to 128 days on soils from western and south-eastern Norway. Soils with the highest pH showed the highest mineralization. The mineralization increased with increasing temperature and time, but start-up N reduced mineralization. The mineralization cannot be estimated from standard soil chemical parameters because the different C/N ratio indicates organic material of different origin and quality. The increase in NO3-N started very quickly and ranged from 17 to 182% and 12 to 64% after 8 days at 3 °C and 20 °C, respectively. There was no correlation between total N in the soil and the amount of mineralized N. On average, the mineralization increased by 5–7% for a change of 1 °C in the interval from 8 to 15 °C in the soil. The chemical extraction method using heated KCl correlated well with the mineralization data. On average, the chemical method estimated 30 kg N ha−1, which corresponded to 0.48% of total N. Recommendations for N fertilization based on total N in the soil overestimate the contribution of plant-available N in most cases.

Imidacloprid, used against mango hopper, is a persistent insecticide in soil. Microbes have the ability to remove toxic pesticides from soil surface. Metagenomic is an approach for understanding the diversity and related metabolic activities in any environmental sample without culturing the microbes. Metagenomic analysis of mango orchard soil was carried out using 16S rRNA gene sequencing to understand the impact of imidacloprid on soil microbial population. In control and imidacloprid applied soil samples, representative sequences clustered were 0.142930 and 0.082320 million, respectively. At the kingdom level, 85 and 88 percent represented to bacteria, 2 and 1 percent to archaea, and 13 and 11 percent to unassigned for control and treated metagenomes, respectively. At phylum level, 16 and 17 percent of OTUs (operational taxonomic units) were assigned with Proteobacteria, while 13 and 11 percent of OTUs were unassigned in control and imidacloprid-treated samples, respectively. The other abundant phyla in both the samples were Planctomycetes, Bacteroidetes, and Actinobacteria. At class level, 9 and 11 percent of OTUs were assigned with Planctomycetia in control as well as imidacloprid-treated samples, respectively. A number of OTUs present in control and imidacloprid applied samples are 31,173 and 21,909, respectively, with 18,018 number of OTUs shared between the two samples. The genus Gemmata totally disappeared in imidacloprid applied soil, while those belonging to class Phycisphaerae, genus Prevotella and species copri were identified in imidacloprid treatment. Bacterial community transformation was evident from this study indicating possible microbial bioremediation of imidacloprid in mango orchard soil.

Mapping the spatial distribution of available copper (A-Cu) in orchard soils is important in agriculture and environmental management. However, data on the distribution of A-Cu in orchard soils is usually highly variable and severely skewed due to the continuous input of fungicides. In this study, ordinary kriging combined with planting duration (OK_PD) is proposed as a method for improving the interpolation of soil A-Cu. Four normal distribution transformation methods, namely, the Box–Cox, Johnson, rank order, and normal score methods, were utilized prior to interpolation. A total of 317 soil samples were collected in the orchards of the Northeast Jiaodong Peninsula. Moreover, 1472 orchards were investigated to obtain a map of planting duration using Voronoi tessellations. The soil A-Cu content ranged from 0.09 to 106.05 with a mean of 18.10 mg kg −1 , reflecting the high availability of Cu in the soils. Soil A-Cu concentrations exhibited a moderate spatial dependency and increased significantly with increasing planting duration. All the normal transformation methods successfully decreased the skewness and kurtosis of the soil A-Cu and the associated residuals, and also computed more robust variograms. OK_PD could generate better spatial prediction accuracy than ordinary kriging (OK) for all transformation methods tested, and it also provided a more detailed map of soil A-Cu. Normal score transformation produced satisfactory accuracy and showed an advantage in ameliorating smoothing effect derived from the interpolation methods. Thus, normal score transformation prior to kriging combined with planting duration (NSOK_PD) is recommended for the interpolation of soil A-Cu in this area.

Fire blight, caused by the bacterium Erwinia amylovora, is a major threat to pear production worldwide. Bacteriophages, viruses that infect bacteria, are a promising alternative to antibiotics for controlling fire blight. In this study, we isolated a novel bacteriophage, RH-42-1, from Xinjiang, China. We characterized its biological properties, including host range, plaque morphology, infection dynamics, stability, and sensitivity to various chemicals. RH-42-1 infected several E. amylovora strains but not all. It produced clear, uniform plaques and exhibited optimal infectivity at a multiplicity of infection (MOI) of 1, reaching a high titer of 9.6 × 109 plaque-forming units (PFU)/mL. The bacteriophage had a short latent period (10 min), a burst size of 207 PFU/cell, and followed a sigmoidal one-step growth curve. It was stable at temperatures up to 60 °C but declined rapidly at higher temperatures. RH-42-1 remained viable within a pH range of 5 to 9 and was sensitive to extreme pH values. The bacteriophage demonstrates sustained activity upon exposure to ultraviolet radiation for 60 min, albeit with a marginal reduction. In our assays, it exhibited a certain level of resistance to 5% chloroform (CHCl3), 5% isopropanol (C3H8O), and 3% hydrogen peroxide (H2O2), which had little effect on its activity, whereas it showed sensitivity to 75% ethanol (C2H5OH). Electron microscopy revealed that RH-42-1 has a tadpole-shaped morphology. Its genome size is 14,942 bp with a GC content of 48.19%. Based on these characteristics, RH-42-1 was identified as a member of the Tectiviridae family, Alphatectivirus genus. This is the first report of a bacteriophage in this genus with activity against E. amylovora.

Understanding the chronological changes in soil microbial and biochemical properties of tea orchard ecosystems after wasteland has been reclaimed is important from ecological, environmental, and management perspectives. In this study, we determined microbial biomass, net N mineralization, and nitrification, enzyme (invertase, urease, proteinase, and acid phosphatase) activities, microbial community diversity assessed by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA polymerase chain reaction (PCR) products, and related ecological factors in three tea orchard systems (8-, 50-, and 90-year-old tea orchards), adjacent wasteland and 90-year-old forest. Soil microbial biomass C (Cmic) and activity, i.e., soil basal respiration (Rmic), microbial biomass C as a percent of soil organic C (Cmic/Corg), N mineralization, invertase, urease, proteinase, and acid phosphatase, significantly increased after wasteland was reclaimed; however, with the succeeding development of tea orchard ecosystems, a decreasing trend from the 50- to 90-year-old tea orchard became apparent. Soil net nitrification showed an increasing trend from the 8- to 50-year-old tea orchard and then a decreasing trend from the 50- to 90-year-old tea orchard, and was significantly higher in the tea orchards compared to the wasteland and forest. Urea application significantly stimulated soil net nitrification, indicating nitrogen fertilizer application may be an important factor leading to high-nitrification rates in tea orchard soils. The Shannon's diversity index (H) and richness (S) based on DGGE profiles of 16S rRNA genes were obviously lower in all three tea orchards than those in the wasteland; nevertheless, they were significantly higher in all three tea orchards than those in the forest. As for the three tea orchard soils, comparatively higher community diversity was found in the 50-year-old tea orchard.

PURPOSE: Nitrous oxide (N₂O) is produced naturally in soils through microbial processes of nitrification and denitrification. In recent years, the long-term application of nitrogen-heavy fertilizers has led to the acidification of tea orchard soils with high N₂O emission. The present research aimed at finding out which process (nitrification or denitrification) dominates in N₂O production, whether certain fertilizer managements could reduce N₂O emission, and the effects of fertilizer management on the abundance of functional genes. MATERIALS AND METHODS: Two nitrification inhibitors, 3, 4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), combined with different N fertilizers (ammonium sulfate and potassium nitrate) were applied to highly acidic tea orchard soil in an aerobic incubation experiment. Both amoA and nosZ gene abundances from different treatments were determined by quantitative PCR. An anaerobic nitrate effect test was carried out using C₂H₂ inhibition method. RESULTS AND DISCUSSION: The application of nitrate fertilizers significantly (P < 0.05) enhanced total N₂O emission. A linear regression analysis between total N₂O emission and average nitrate contents indicated that denitrification is the dominant source of N₂O in this tea orchard soil. In the anaerobic incubation, no significant difference of N₂O emission was observed between KNO₃ and no KNO₃ treatments before 96 h. Quantitative PCR revealed lower copy numbers of nosZ in nitrate-associated fertilizer-treated soils than the soils from other treatments. Compared with the control, ammonium fertilizers with DCD or DMPP significantly (P < 0.05) inhibited nitrate production as well as N₂O. CONCLUSIONS: These results showed that denitrification is the dominant source of N₂O in this highly acidic soil. Nitrate addition could significantly inhibit the abundance of nitrous oxide reductase, therefore causing high N₂O emission. The application of ammonium fertilizers with DCD or DMPP could significantly reduce N₂O emission, possibly due to the effective inhibition of nitrate production.

BACKGROUND: Plant biostimulants are diverse substances and microorganisms used to enhance plant growth. The global market for biostimulants is projected to increase 12 % per year and reach over $2,200 million by 2018. Despite the growing use of biostimulants in agriculture, many in the scientific community consider biostimulants to be lacking peer-reviewed scientific evaluation. SCOPE: This article describes the emerging definitions of biostimulants and reviews the literature on five categories of biostimulants: i. microbial inoculants, ii. humic acids, iii. fulvic acids, iv. protein hydrolysates and amino acids, and v. seaweed extracts. CONCLUSIONS: The large number of publications cited for each category of biostimulants demonstrates that there is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species. The cited literature also reveals some commonalities in plant responses to different biostimulants, such as increased root growth, enhanced nutrient uptake, and stress tolerance.

Aerobic denitrification is the main process for high N₂O production in acid tea field soil. However, the biological mechanisms for the high emission are not fully understood. In this study, we examined N₂O emission and denitrifier communities in 100-year-old tea soils with four pH levels (3.71, 5.11, 6.19, and 7.41) and four nitrate concentration (0, 50, 200, and 1000 mg kg⁻¹of NO₃⁻-N) addition. Results showed the highest N₂O emission (10.1 mg kg⁻¹over 21 days) from the soil at pH 3.71 with 1000 mg kg⁻¹NO₃⁻addition. The N₂O reduction and denitrification enzyme activity in the acid soils (pH <7.0) were significantly higher than that of soils at pH 7.41. Moreover, TRF 78 of nirS and TRF 187 of nosZ dominated in soils of pH 3.71, suggesting an important role of acidophilic denitrifiers in N₂O production and reduction. CCA analysis also showed a negative correlation between the dominant denitrifier ecotypes (nirS TRF 78, nosZ TRF 187) and soil pH. The representative sequences were identical to those of cultivated denitrifiers from acidic soils via phylogenetic tree analysis. Our results showed that the acidophilic denitrifier adaptation to the acid environment results in high N₂O emission in this highly acidic tea soil.

Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H⁺) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H⁺ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H⁺ per hectare per year) made a small contribution to the acidification of agricultural soils across China.