Soil Dehydrogenase Research Articles

Remediation of PBDE-contaminated soil using biochar-based bacterial consortium QY2Y

Biochar-immobilized microbial technologies hold substantial promise for the remediation of environmental contaminants. However, the understanding of remediation efficiency and the operation of microbial consortia in complex soil environments using biochar as a carrier remains limited. In this study, we explored the impacts of biochar combined with bacterial consortium QY2Y (consisting of Chitinophaga sp. MH-1, Achromobacter sp. YH-1, Methylobacterium sp. ZY-1, and Sphingomonas sp. GY-1) on BDE-47 dissipation in contaminated soil, as well as its effects on soil-plant systems. The findings indicated that the immobilization of biochar and QY2Y not only stimulated the biodegradation of BDE-47 (61.50%) but also decreased the bioavailability of BDE-47, subsequently reducing the concentration of BDE-47 in the edible portion of rapeseed (Brassica napus L.) by 82.00%. In addition, the combined treatment notably increased soil pH, enhanced the physicochemical properties and nutrient conditions of the soil, and amplified soil dehydrogenase, catalase, urease, and acid phosphatase activities by 58.72%, 69.25%, 54.24%, and 74.74%, respectively. The application of biochar-based QY2Y improved the soil microbial community structure, bolstered the interspecific symbiotic and cooperative relationships, and restructured the keystone taxa. The key species microbes had direct and significant positive effects on BDE-47 degradation, soil nutrients, and soil enzyme activity. This study deepens our understanding of the potential applications of immobilized microbial consortia in treating PBDE-contaminated soils and offers guidance for the management and remediation of contaminated soils.

Effect of Different Kharif Paddy Straw Management Options and Different Levels of Nitrogen on Soil Dehydrogenase and Urease Activity

A field experiment was conducted during rabi 2020-21, at Regional Agricultural Research Station, Polasa, Jagtial, PJTSAU to study soil dehydrogenase and urease activity as influenced by different kharif paddy straw management options and nitrogen levels. The results reveal that dehydrogenase and urease activity of soil was significantly influenced by paddy straw management options and activity was increased with crop duration up to 60 DAT and decreased after harvest. Dehydrogenase activity was reduced after burning (1.93 mg TPF produced g-1 soil d-1) as compared to the initial values (2.34 mg TPF produced g-1 soil d-1). The highest dehydrogenase activity of 3.74 and 3.54 mg TPF produced g-1 soil d-1 was recorded at 60 DAT in paddy straw incorporation with phosphorus and incorporation without phosphorus and decreased to 3.36 and 3.03 mg TPF produced g-1 soil d-1 after harvest respectively. Soil urease activity was showed an increasing trend with crop duration up to 60 DAT and then declined. Maximum activity of 3.05, 4.84, 5.17 mg NH4+ released g-1 soil h-1 was observed at 60 DAT under paddy straw burning, paddy straw incorporation with phosphorus incorporation without phosphorus respectively. Paddy straw incorporation with phosphorus recorded higher urease activity and paddy straw burning recorded lower urease activity at all the intervals of crop growth. The effect of nitrogen levels on soil urease activity was found to be significant. Soil urease was highest with 120% RDN followed by 115% RDN, followed by 110% RDN, followed by 100% RDN and the similar trend was observed at all the intervals of crop growth.

Overexpressing Carbonic Anhydrase Transgenic Rice Plants Maintain the Regular Soil Functions and Microbial Activities of Soil

Background: Genetically modified (GM) crops are focused on establishing desirable traits to support the food demand of increasing populations. The effect of transgenic plants on soil diversity has been highlighted by a lot of researchers. Some of them showed the negative effect of transgenic crop on soil microbes and the food chain. So there is an urgent need to develop transgenic plants with no harmful effects on environmental health. Methods: We have examined the effects salt tolerant carbonic anhydrase overexpressing transgenic rice plants on the physiology of rhizospheric microbes and their enzymatic activities. In the present study, we have used pot experiments in the greenhouse of Centurion University of Technology and management, Bhubaneswar, Odisha, India. Result: No significant variation in the soil properties viz., pH, Eh, organic C, P, K, N, Ca, Mg, S, Na and Fe+2 were observed. The population of bacteria, fungi and nematodes were remained same in the soil. The enzymatic activities like soil dehydrogenase, nitrate reductase, urease and alkaline phosphatase were not significantly affected. Further, plant growth promotion (PGP) functions such as HCN, siderophore, salicylic acid, GA, IAA, zeatin, were, not influenced considerably. The present study ecologically pertinent of salt tolerant CA transgenic rice to usual functions of the rhizospheric organisms.

Assessment of Soil Dehydrogenase and Phosphatase Activities after Exposure to Certain Pesticides as Biomarkers for Pesticide Pollution

Assessment of Soil Dehydrogenase and Phosphatase Activities after Exposure to Certain Pesticides as Biomarkers for Pesticide Pollution

Enhancing fruit quality and yield in tomato through cyanobacterium mediated nutri-fertigation

Protected cultivation of high-value crops such as tomato, with several health benefits, is gaining global significance. This study explored the influence of aqueous formulations of cyanobacteria-Anabaena laxa (C11), Nostoc carneum (BF2), and Anabaena doliolum (BF4), applied as soil drench at pre-flowering and fruiting stages, on the dynamics of soil and plant attributes important for growth, productivity, and quality of fruits in an indeterminate tomato variety (NS4266) under protected cultivation. Drenching with the BF2 formulation resulted in a significant fold-increase in soil dehydrogenase activity and an increase of 40–45% in soil nitrogen availability; positively impacted glutamine synthetase activity, fruit weight, lycopene content, skin elasticity, in comparison to control. C11 drenching led to a 17% elevation in soil microbial biomass carbon, besides bringing about a 24 and 54% enhancement in available phosphorus and iron content. Additionally, it also enhanced chlorophyll a, b and total pigments by 54–65% over control. Principal Component Analysis (PCA) and Multivariate analysis showcased the distinct effects of cyanobacterial formulations on crop growth and soil fertility, as well as the significant and positive correlations among quality, plant, soil, and yield attributes contributed through cyanobacterial drenching. This investigation highlighted cyanobacterial drench as a promising organic option to augment soil nutrient availability, bolster overall productivity, and enhance fruit quality in tomato grown under protected cultivation.

Metagenomic insights into nitrogen cycling functional gene responses to nitrogen fixation and transfer in maize-peanut intercropping.

The fixation and transfer of biological nitrogen from peanuts to maize in maize-peanut intercropping systems play a pivotal role in maintaining the soil nutrient balance. However, the mechanisms through which root interactions regulate biological nitrogen fixation and transfer remain unclear. This study employed a 15N isotope labelling method to quantify nitrogen fixation and transfer from peanuts to maize, concurrently elucidating key microorganisms and genera in the nitrogen cycle through metagenomic sequencing. The results revealed that biological nitrogen fixation in peanut was 50 mg and transfer to maize was 230 mg when the roots interacted. Moreover, root interactions significantly increased nitrogen content and the activities of protease, dehydrogenase (DHO) and nitrate reductase in the rhizosphere soil. Metagenomic analyses and structural equation modelling indicated that nrfC and nirA genes played important roles in regulating nitrogen fixation and transfer. Bradyrhizobium was affected by soil nitrogen content and DHO, indirectly influencing the efficiency of nitrogen fixation and transfer. Overall, our study identified key bacterial genera and genes associated with nitrogen fixation and transfer, thus advancing our understanding of interspecific interactions and highlighting the pivotal role of soil microorganisms and functional genes in maintaining soil ecosystem stability from a molecular ecological perspective.

Evidence of Cooperative Interactions between Rhizobacteria and Wood-Decaying Fungi and Their Effects on Maize Germination and Growth

Advances in soil microbial communities are driving agricultural practices towards ecological sustainability and productivity, with engineering microbial communities significantly contributing to sustainable agriculture. This study explored the combined effects of two white-rot fungi (Trametes sp. and Pleurotus sp.) and six rhizobacterial strains belonging to four genera (Acinetobacter sp., Enterobacter sp., Flavobacterium sp., and Pseudomonas sp.) on maize growth and soil enzymatic activity over a 14-day period. At the plant level, germination, fresh and dry mass of the aerial and root parts, length, and stage of development of the stem, as well as the chlorophyll content, were evaluated. Furthermore, soil dehydrogenase, acid and alkaline phosphatases, pH, and electrical conductivity were evaluated. Rot fungi induced distinct effects on maize germination, with Pleurotus sp. strongly suppressing maize germination by 40% relative to that of the control. The isolated bacterial strains, except Enterobacter sp. O8, and 8 of the 12 fungus + bacterial strain combinations induced germination rates higher than those of the control (≥40%). Combinations of Flavobacterium sp. I57 and Pseudomonas sp. O81 with the rot fungus Pleurotus sp. significantly improved plant shoot length (from 28.0 to 37.0 cm) and developmental stage (fourth leaf length increase from 10.0 to 16.8 cm), respectively, compared with the same bacteria alone or in combination with the rot fungus Trametes sp. In the soil, the presence of both fungi appeared to stabilize phosphatase activity compared to their activity when only bacteria were present, while also promoting overall dehydrogenase enzymatic activity in the soil. Integrating all parameters, Trametes sp. rot fungus + Enterobacter sp. O8 may be a potential combination to be explored in the context of agricultural production, and future studies should focus on the consistency of this combination’s performance over time and its effectiveness in the field.

Role of compost in assisted phytostabilization via three naturally occurring species on mine-contaminated soil and health risk alleviation for livestock

Phytostabilization emerges as an efficient and enduring remediation technique for heavy metal-contaminated mine soils using plants acclimatized to such circumstances. In this research, the synergistic effects of Marrubium cuneatum, Verbascum speciosum, and Stipa arabica species, alongside municipal solid waste compost (MSWC) amendment at 0, 1, 3, and 5 % rates, were assessed for a six-month pot experiment aimed at remediating naturally polluted soil containing lead (Pb) and cadmium (Cd) and mitigating the health risks associated with these metal exposures for grazing ruminants. Applying compost improved the aboveground biomass of M. cuneatum and V. speciosum and S. arabica by 13, 19, and 18 %, respectively. Also, soil dehydrogenase and urease enzyme activities were enhanced up to 131 and 34 %. Upon MSWC application, all three species uptake Cd and Pb at a significantly lower rate, except in the V. speciosum shoot at 3 and 5 % doses, and bioaccumulation factors were markedly diminished. Compost notably augmented the antioxidant system, leading to a reduction in malondialdehyde content of V. speciosum, M. cuneatum, and S. arabica by 35, 29, and 23 %, respectively, and an elevation in chlorophyll level. Superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase activities either increased or displayed no significant differences. Risk assessment revealed that MSWC substantially decreased the daily intake of Pb and Cd and their accumulation in animal organs, thereby eliminating limits on meat consumption. Findings affirm the combined efficacy of MSWC and the study species in stabilizing contaminated Pb and Cd soils, diminishing risks to animal feed security and human health.

Effects of N, N-bis (carboxymethyl)-L-glutamic acid and polyaspartic acid on the phytoremediation of cadmium in contaminated soil at the presence of pyrene: Biochemical properties and transcriptome analysis

Chelator-assisted phytoremediation is an efficacious method for promoting the removal efficiency of heavy metals (HMs). The effects of N, N-bis(carboxymethyl)-L-glutamic acid (GLDA) and polyaspartic acid (PASP) on Cd uptake and pyrene removal by Solanum nigrum L. (S. nigrum) were compared in this study. Using GLDA or PASP, the removal efficiency of pyrene was over 98%. And PASP observably raised the accumulation and transport of Cd by S. nigrum compared with GLDA. Meanwhile, both GLDA and PASP markedly increased soil dehydrogenase activities (DHA) and microbial activities. DHA and microbial activities in the PASP treatment group were 1.05 and 1.06 folds of those in the GLDA treatment group, respectively. Transcriptome analysis revealed that 1206 and 1684 differentially expressed genes (DEGs) were recognized in the GLDA treatment group and PASP treatment group, respectively. Most of the DEGs found in the PASP treatment group were involved in the metabolism of carbohydrates, the biosynthesis of brassinosteroid and flavonoid, and they were up-regulated. The DEGs related to Cd transport were screened, and ABCG3, ABCC4, ABCG9 and Nramp5 were found to be relevant with the reduction of Cd stress in S. nigrum by PASP. Furthermore, with PASP treated, transcription factors (TFs) related to HMs such as WRKY, bHLH, AP2/ERF, MYB were down-regulated, while more MYB and bZIP TFs were up-regulated. These TFs associated with plant stress resistance would work together to induce oxidative stress. The above results indicated that PASP was more conducive for phytoremediation of Cd-pyrene co-contaminated soil than GLDA.

Diversified Cover Crops and No-Till Enhanced Soil Total Nitrogen and Arbuscular Mycorrhizal Fungi Diversity: A Case Study from the Karst Area of Southwest China

The deteriorating soil health under continuous monoculture is commonly found across various cropping systems. This study evaluated the effects of different tillage practices (conventional tillage and no till) and species mixtures (legumes and grasses) on arbuscular mycorrhizal fungi (AMF) community properties, soil nutrients, and enzyme activity in a 3-year experiment. Compared with traditional tillage, the number of AMF species under no-till conditions was increased, with the Glomus group being dominant. Under different tillage conditions, TN (total N) and AN (available N) contents under no till were significantly higher than those under conventional tillage, while no significant differences among other nutrients were found. The activities of soil acid phosphatase (S-ACP), soil dehydrogenase (S-DHA), and soil sucrose (S-SC) under conventional tillage were significantly higher than those under no till, and the cover crop mixtures also had an exclusive advantage in yield. Soil organic matter (SOM) indicated a significant negative correlation with glomalin-related soil protein (GRSP). The increase in diversity associated with the AMF species community was strongly correlated with the increase in three enzyme activities, and AN was negatively correlated with all species. Tillage did not significantly change soil chemistry, except for AN, and the high concentration of AN led to a decrease in AMF species. The results of this study showed that no till was an effective measure for enriching soil micro-organism population. Additionally, soil AMF diversity was improved by cover crop mixtures, and microbial diversity was higher than that under monoculture cover crops. Different AMF groups responded differently to tillage and cover crop mixtures. Across all mixtures, the combination of hairy vetch (Vicia villosa R.) and ryegrass (Lolium perenne L.) performed the best.

Remediation of petroleum-contaminated site soil by bioaugmentation with immobilized bacterial pellets stimulated by a controlled-release oxygen composite

Bioaugmentation techniques still show drawbacks in the cleanup of total petroleum hydrocarbons (TPHs) from petroleum-contaminated site soil. Herein, this study explored high-performance immobilized bacterial pellets (IBPs) embed Microbacterium oxydans with a high degrading capacity, and developed a controlled-release oxygen composite (CROC) that allows the efficient, long-term release of oxygen. Tests with four different microcosm incubations were performed to assess the effects of IBPs and CROC on the removal of TPHs from petroleum-contaminated site soil. The results showed that the addition of IBPs and/or CROC could significantly promote the remediation of TPHs in soil. A CROC only played a significant role in the degradation of TPHs in deep soil. The combined application of IBPs and CROC had the best effect on the remediation of deep soil, and the removal rate of TPHs reached 70%, which was much higher than that of nature attenuation (13.2%) and IBPs (43.0%) or CROC (31.9%) alone. In particular, the CROC could better promote the degradation of heavy distillate hydrocarbons (HFAs) in deep soil, and the degradation rates of HFAs increased from 6.6% to 33.2%–21.0% and 67.9%, respectively. In addition, the IBPs and CROC significantly enhanced the activity of dehydrogenase, catalase, and lipase in soil. Results of the enzyme activity were the same as that of TPH degradation. The combined application of IBPs and CROC not only increased the microbial abundance and diversity of soil, but also significantly enhanced the enrichment of potential TPH-biodegrading bacteria. M. oxydans was dominant in AP (bioaugmentation with addition of IBPs) and APO (bioaugmentation with the addition of IBPs and CROC) microcosms that added IBPs. Overall, the IBPs and CROC developed in this study provide a novel option for the combination of bioaugmentation and biostimulation for remediating organic pollutants in soil.

Insights on soil biological properties and crop yields under natural farming in western Himalaya

Sustainability of agricultural production systems is a major concern in context to present environmental conditions. Natural farming (NF) is being promoted as low-cost environment friendly option. A study was carried out to investigate the effects of NF vis-a-vis organic farming (OF) and conventional farming (CF) systems on soil microbial population, enzymatic activity, and microarthropod population under tomato crop in the mid-hill zone of Himachal Pradesh, India. The results showed that bacterial population under NF increased by 42.8% and 24% in comparison to CF and OF, respectively. Similarly, the population of soil fungi and actinomycetes under NF increased by 80.5 and 67.7% over CF, and by 47.9 and 39.6% over OF, respectively. The soil dehydrogenase activity under NF (22.5µg TPF/g soil/h) was 150.6% higher than CF and 85.2% higher than OF. Similar trend was found for phosphatase and urease activity. Soil micro arthropod population after two years of experiment was also highest under NF followed by OF and CF. The system yield was statistically at par to each other, among different farming systems. All the soil biological parameters were significantly correlated with each other (P<0.001, N=42). However, the correlation of these parameters was not significant for crop yield.

Combined effects of border irrigation and super-absorbent polymers on enzyme activity and microbial diversity of poplar rhizosphere soil.

Fast-growing poplar plantations are considered a great benefit to timber production, but water availability is a key factor limiting their growth and development, especially in arid and semi-arid ecosystems. Super-absorbent polymers facilitate more water retention in soil after rain or irrigation, and they are able to release water gradually during plant growth. This study aimed to examine the effects of reduced irrigation (60% and 30% of conventional border irrigation) co-applied with super-absorbent polymers (0, 40 kg/ha) on root exudates, enzyme activities, microbial functional diversity in rhizosphere soil, and volume increments in poplar (Populus euramericana cv. 'Neva'). The results showed that 60% border irrigation co-applied with super-absorbent polymers significantly increased the content of organic acids, amino acids and total sugars in the root exudates, and the activities of invertase, urease, dehydrogenase, and catalase in the rhizosphere soil in comparison to conventional border irrigation without super-absorbent polymers. Meanwhile, this treatment also enhanced the average well-color development, Shannon index, and McIntosh index, but decreased the Simpson index. Additionally, the average volume growth rate and relative water content of leaves reached their maximum using 60% irrigation with super-absorbent polymers, which was significantly higher than other treatments. However, using 30% irrigation with super-absorbent polymers, had a smaller effect on rhizosphere soil and volume growth than 60% irrigation with super-absorbent polymers. Therefore, using an appropriate water-saving irrigation measure (60% conventional border irrigation with super-absorbent polymers) can help to improve enzyme activities and microbial diversity in the rhizosphere soil while promoting the growth of poplar trees.

Interactions of Microbial Inoculations with Fertilization Options and Crop Establishment Methods on Modulation of Soil Microbial Properties and Productivity of Rice

A field investigation was undertaken to assess the interactive effects of different crop establishment methods (CEMs) and microbial formulations in field conditions. The two year experiment was carried out in kharif season (June to October) of both 2013–14 and 2014–15 at Research Farm of ICAR-Indian Agricultural Research Institute, New Delhi India. The CEMs studied consist of puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS); while microbial formulations consist of Anabaena sp. (CR1)+Providencia sp. (PR3) consortium (MC1) and Anabaena–Pseudomonas biofilm formulation (MC2). The microbial inoculation was applied with 75% recommended dose of nutrients (RDN) (90 kg nitrogen ha-1 and 19.35 kg phosphorus ha-1) and compared with 100% RDN. Soil microbiological properties showed significantly higher values in SRI in the first year; while in the second year, SRI and PTR remained on par and superior to ARS. Among the combinations of nutrient supplements, application of Anabaena–Pseudomonas biofilm formulation (MC2) with 75% RDN was superior in terms of all microbiological attributes studied [acetylene reduction activity (ARA), soil chlorophyll, soil dehydrogenase activity, microbial biomass carbon and alkaline phosphatase activity]. Application of microbial inoculation led to an increase in milled rice yield from 230 to 240 kg ha-1. Among the different combinations of CEMs and inputs investigated the application of 75% RDN+MC2+zinc (Zn) (soil applied 5 kg Zn ha-1 through zinc sulphate heptahydrate) in SRI can be a judicious option to maximize rice yield and soil health.

Effect of Tank Mix Post-emergence Herbicides on Soil Dehydrogenase Activity and Its Phytotoxicity on Wheat

Effect of Tank Mix Post-emergence Herbicides on Soil Dehydrogenase Activity and Its Phytotoxicity on Wheat

System of wheat intensification (SWI): Effects on lodging resistance, photosynthetic efficiency, soil biomes, and water productivity.

Intense cultivation with narrow row spacing in wheat, a common practice in the Indo-Gangetic plains of South Asia, renders the crop more susceptible to lodging during physiological maturity. This susceptibility, compounded by the use of traditional crop cultivars, has led to a substantial decline in overall crop productivity. In response to these challenges, a two-year field study on the system of wheat intensification (SWI) was conducted. The study involved three different cultivation methods in horizontal plots and four wheat genotypes in vertical plots, organized in a strip plot design. Our results exhibited that adoption of SWI at 20 cm × 20 cm resulted in significantly higher intercellular CO2 concentration (5.9-6.3%), transpiration rate (13.2-15.8%), stomatal conductance (55-59%), net photosynthetic rate (126-160%), and photosynthetically active radiation (PAR) interception (1.6-25.2%) over the existing conventional method (plant geometry 22.5 cm × continuous plant to plant spacing) of wheat cultivation. The lodging resistance capacity of both the lower and upper 3rd nodes was significantly higher in the SWI compared to other cultivation methods. Among different genotypes, HD 2967 demonstrated the highest recorded value for lodging resistance capacity, followed by HD 2851, HD 3086, and HD 2894. In addition, adoption of the SWI at 20 cm × 20 cm enhanced crop grain yield by 36.9-41.6%, and biological yield by 27.5-29.8%. Significantly higher soil dehydrogenase activity (12.06 μg TPF g-1 soil hr-1), arylsulfatase activity (82.8 μg p-nitro phenol g-1 soil hr-1), alkaline phosphatase activity (3.11 n moles ethylene g-1 soil hr-1), total polysaccharides, soil microbial biomass carbon, and soil chlorophyll content were also noted under SWI over conventional method of the production. Further, increased root volumes, surface root density and higher NPK uptake were recorded under SWI at 20×20 cm in comparison to rest of the treatments. Among the tested wheat genotypes, HD-2967 and HD-3086 had demonstrated notable increases in grain and biological yields, as well as improvements in the photosynthetically active radiation (PAR) and chlorophyll content. Therefore, adoption of SWI at 20 cm ×20 cm (square planting) with cultivars HD 2967 might be the best strategy for enhancing crop productivity and resource-use efficiency under the similar wheat growing conditions of India and similar agro-ecotypes of the globe.

Organic Fertilizer with High Nutrient Levels Affected Peanut-Growing Soil Bacteria More Than Fungi at Low Doses

The breeding of laying hens and broilers in China has increased tremendously. Wet organic fertilizer prepared from hen manure using high-temperature container fermentation preserves high levels of nutrients and a diverse microbial community. We applied low doses of organic fertilizer to peanuts in the black soil area of China’s northeastern region. Based on the calculation of nitrogen content, treatments were set as follows: chemical fertilizer (PCF), organic fertilizer (POF, 4500 kg·ha−1), and replacement of 50% chemical fertilizer with organic fertilizer (PR, 2250 kg·ha−1). Compared to the plots with chemical fertilizers, the use of organic fertilizer and replacing 50% of the chemical fertilizers with organic fertilizer significantly increased peanut yields. Both the organic fertilizer and replacing 50% of the chemical fertilizers with organic fertilizer did not significantly affect the activities of the most tested soil enzymes related to carbon transformation and the absolute abundance of microorganisms. However, they did significantly enhance soil dehydrogenase and α-glucosidase. The community abundance ratio of fungi/bacteria trended downward, leading to soil with a high-fertility bacterial composition. The replacement of 50% chemical fertilizer with organic fertilizer significantly enhanced the species richness and diversity of the bacterial and fungal communities. Organic fertilizer treatment significantly increased the relative abundance of Gemmatimonas and Sphingomonas. The relative abundance of Mycobacterium in the treatment where 50% of the chemical fertilizers were replaced with organic fertilizer was significantly lower than that in the organic fertilizer treatment. PCoA results showed that the low-dose organic fertilizer treatment, replacing 50% of the chemical fertilizers with organic fertilizer, had a significant impact on the composition of soil bacterial communities.

Impact assessment of thiamethoxam on microbial and enzymatic activity in mango rhizosphere

Thiamethoxam is a globally used neonicotinoid insecticide in mango ecosystem which can cause hazardous impact on soil environment. The current study was carried out to assess the impact of 0.2 (T1/treament) and 2.0 g kg−1 (T2) concentrations of thiamethoxam on mango rhizospheric microbial community, enzyme activity along with its degradation. Indigenous microflora degraded thiamethoxam from 5.62 to 41.17 mg kg−1 at 0 day to 0.60 and 2.10 mg kg−1 in soil after 60 days of application of 0.2 and 2.0 g kg−1 doses, respectively. Thiamethoxam dissipated via pseudo first-order kinetics with t1/2 (half-life) values (23.00 and 14.00) days and K values (1.99–17.14) and (21.42–183.6) at T1 and T2, respectively. At bacterial count of 5.5 × 107 in soil, fluorescein diacetate (FDA) and dehydrogenase (DHA) showed that there was no change occurred in control soil after 60 days, while in thiamethoxam treated soil DHA was marginally increased from 0.164 to 0.168 µg g−1 and from 0.155 to 0.157 µg g−1 at lower and higher doses, respectively. While, FDA values were slightly decreased from 0.761 to 0.717 µg g−1 at T1 but no significant change was observed in T2. However, changes in fungal population were not significant but increase in bacterial population with the degradation of thiamethoxam was observed, which indicated the presence of thiamethoxam degrading beneficial bacteria in mango rhizosphere soil.

Effects of biochar immobilization of Serratia sp. F4 OR414381 on bioremediation of petroleum contamination and bacterial community composition in loess soil

Petroleum hydrocarbons pose a significant threat to human health and the environment. Biochar has increasingly been utilized for soil remediation. This study investigated the potential of biochar immobilization using Serratia sp. F4 OR414381 for the remediation of petroleum-contaminated soil through a pot experiment conducted over 90 days. The treatments in this study, denoted as IMs (maize straw biochar-immobilized Serratia sp. F4), degraded 82.5% of the total petroleum hydrocarbons (TPH), 59.23% of the aromatic, and 90.1% of the saturated hydrocarbon fractions in the loess soils. During remediation, the soil pH values decreased from 8.76 to 7.33, and the oxidation-reduction potential (ORP) increased from 156 to 229 mV. The treatment-maintained soil nutrients of the IMs were 138.94 mg/kg of NO3- -N and 92.47 mg/kg of available phosphorus (AP), as well as 11.29% of moisture content. The activities of soil dehydrogenase (SDHA) and catalase (CAT) respectively increased by 14% and 15 times compared to the CK treatment. Three key petroleum hydrocarbon degradation genes, including CYP450, AJ025, and xylX were upregulated following IMs treatment. Microbial community analysis revealed that a substantial microbial population of 1.01E+ 09 cells/g soil and oil-degrading bacteria such as Salinimicrobium, Saccharibacteria_genera_incertae_sedis, and Brevundimonas were the dominant genera in IMs treatment. This suggests that the biochar immobilized on Serratia sp. F4 OR414381 improves soil physicochemical properties and enhances interactions among microbial populations, presenting a promising and environmentally friendly approach for the stable and efficient remediation of petroleum-contaminated loess soil.

RHIZOSPHERE MICROBIOME, SOIL ENZYMES AND GROUNDNUT YIELD AS INFLUENCED BY ADDITION OF BIOCHAR AND FERTILIZERS IN IRRIGATED ALFISOL OF NORTH COASTAL ANDHRA PRADESH

The field experiment was conducted in irrigated Alfisols of North coastal Andhra Pradesh tostudy the effect of biochar and chemical fertilizers on rhizosphere microbiome, soil enzymes andyield performance of groundnut crop (variety K-6) during rabi, 2018-19. Biochar application tosoil significantly increased soil bacterial, fungal and actinomycetes population. At pod developmentstage, the highest number of bacterial count (39.0 x106 CFU g-1 soil) was observed in T5 (100%RDF + biochar @ 6 t ha-1) which was on par with all the biochar applied treatments (T3, T4, T6, T7,T8). The Biochar applied @ 6 t ha-1 (T5 & T8) significantly increased the bacterial population ascompared to non-biochar applied treatments (T1 & T2). Fungal and actinomycetes populationfollowed the similar trend of bacterial count. Soil urease activity was significantly superior inbiochar applied treatments (T3, T4, T5, T6, T7, T8) compared to non biochar applied treatments (T1and T2). With increased rates of biochar application the urease activity markedly increased insoil. Similar trend was noticed with respect to dehydrogenase, acid phosphatase and alkalinephosphatase enzymes in soil in response to addition of biochar. At pod development stage, thehighest leaf area index (3.16) was recorded with 100% RDF + biochar @ 6 t ha-1(T5) which wassignificantly higher than T1 (control), T2 (100% RDF) and T6 (75% RDF + biochar @ 2 t ha-1). Thehighest drymatter accumulation of 2951 kg ha-1 at peg penetration and 6428 kg ha-1 at poddevelopment was observed in T5 (100% RDF + biochar @ 6 t ha-1) which was on par with T3(100% RDF + biochar @ 2 t ha-1), T4 (100% RDF + biochar @ 4 t ha-1), T8 (75% RDF + biochar @6 t ha-1) treatments. Groundnut pod yield was highest (4019.58 kg ha-1) in treatment received100% RDF + biochar @ 6 t ha-1, which was on par with T4 (100% RDF + biochar @ 6 t ha-1) and T8(75% RDF + biochar @ 6 t ha-1).