AI and business management: Tracking future research agenda through bibliometric network analysis.

This study has been designed to analyse the academic landscape of AI on the Scopus and Web of Science (WOS) indices and compare the findings. AI is one of the most prominent and preferred research areas, only a few studies are dedicated to the bibliometric aspect of it. There is a need to compare studies on AI over different databases to identify the impact and usefulness of those studies in decision-making in business management. To conduct this analysis, the authors have collected data from both Scopus and WOS. 'VOSviewer', 'R-Studio', and 'MS Excel' software have been used for performance analysis and science mapping. This is one of the exceptional studies which perform a comparative analysis between two indices and also identifies funding sponsors for support of research in AI. "Dwivedi, Y.K." is the most productive author and "Huang, Minghui" is the most impactful author. "National Natural Science Foundation of China" is the funding agency which has significantly supported AI research. Technical aspects like "Machine learning", "neural networks", and "blockchain" with 'Sustainability', 'sustainable development', 'accounting', and 'auditing' are trending themes for managerial decision-making.

Independent antioxidant and anticancer properties of a novel thermostable lysozyme isolated from Bacillus paralicheniformis: in silico and in vitro studies.

In this study, we evaluated the independent anticancer properties of a novel heat-stable lysozyme derived from the thermophilic bacterium Bacillus paralicheniformis (BplzC) to identify potential alternative therapies to address the suboptimal outcomes of current cancer treatments. Using the String 10.5 database, an in-silico protein-protein interaction study predicted that BplzC was a strong functional partner of cytochrome c, indicating a potential role in cancer cell apoptosis. Further, the HDOCK server predicted that BplzC strongly bound to cell death receptors, such as cytokines FAS receptor, leading to activation of cytochrome c and subsequent apoptosis in the cancer cell line. In vitro assays demonstrated uniform apoptotic activity of BplzC against various cancer cell lines, while showing no apoptotic activity against normal non-cancer cell lines. And showing no apoptotic activity against normal non-cancer cell lines suggested a very specific mode of action and without any adverse side effects. Additionally, BplzC exhibited ROS scavenging activity and reducing ability comparable to ascorbic acid, and significantly accelerated HEK293 cell migration. Our findings suggest that BplzC has specific cytotoxic effects on cancer cells and may be a valuable natural source of antioxidants for future use in the nutritional and pharmaceutical sectors.

Impact of sequential herbicides application on crop productivity, weed and nutrient dynamics in soybean under conservation agriculture in Vertisols of Central India.

Adoption of conservation agriculture (CA) is very slow due to weed infestations. The application of herbicides is the only viable option to deal with problem of weed management to adhere with basic principles of CA. A field experiment was carried out for three years to evaluate the expediency of different herbicides and their sequential applications under CA. In this study, seven treatments comprised of either alone or sequential application of pre-emergence (PE) and post-emergence (PoE) herbicides, hand weeding and weedy check were tested in soybean. Result indicated that sequential application of glyphosate at 1 kg ai ha-1 + pendimethalin at 1 kg ai ha-1as PE followed by PoE application of imazethapyr at 100 g ai ha-1 at 30 days after sowing (DAS) proved to be the best economical option in terms of plant growth parameters, crop biomass, seed yield, weed index and carbon and nutrient recycling. Pearson's correlation coefficients matrix revealed that grain yield was significantly (P<0.0001) related to weed density at harvest (r = -0.84), (WDH) (r = -0.63), weed dry biomass (WDB) (r = -0.52), weed nitrogen (N), phosphorus (P) and potassium (K) uptake (r = -0.56, r = -0.59 and r = -0.66), respectively and weed index (WI) (r = -0.96). The bivariate linear regression study of grain yield on weed control efficiency (WCI) biomass, N, P and K uptake by grain showed a clear significant (P<0.0001) dependence with R2 value of 0.53, 0.99, 0.95 and 0.98, respectively. The fitted stepwise multiple regression model also revealed that N and P uptake in grain, weed density at 20 DAS and K uptake in weed were actual predictor for grain yield. We concluded that, effective and economical weed control under CA in soybean can be achieved through sequential application of glyphosate along with pendimethalin at 1 kg ai ha-1 each PE followed by PoE use of imazethapyr at 100 g ai ha-1 at 30 DAS.

Performance of chickpea (Cicer arietinum L.) in maize-chickpea sequence under various integrated nutrient modules in a Vertisol of Central India.

Present investigation was conducted at the Research Farm of Indian Institute of Soil Science, Bhopal during 2017-18 and 2018-19 to study the performance of chickpea crop under various nutrient management modules in a Vertisol. The field experiment was set up in a randomized block design with three replications of twelve different INM modules. During the rabi seasons of 2017-18 and 2018-19, the chickpea (cv. JG-315) was grown with a set of treatments. The crop's performance was evaluated in terms of growth, yield (grain and straw), nutritional content, and nutrient uptake under different treatments. At crop harvest, the physic-chemical characteristics of the soil were also evaluated. Finally, the relationship between the numerous examined parameters was determined. The results showed that integrated nutrient management modules had a positive impact on chickpea crop performance and productivity when compared to using only inorganic fertilizer. The INM modules dramatically increased soil organic carbon and improved soil health in terms of physical and chemical qualities, in addition to higher crop performance. Among the various modules, (1) application of 75% STCR dose + FYM @ 5t ha-1to maize followed by 100% P only to chickpea and (2) application of FYM @ 20t ha-1to maize followed by FYM @ 5t ha-1 to chickpea increased the productivity and nutrient uptake in chickpea, improved soil physico-chemical properties and reflected as viable technique in improving soil nutrient availability on sustainable basis.

Glycoproteins of arbuscular mycorrhiza for soil carbon sequestration: Review of mechanisms and controls.

Glycoproteins, e.g., glomalin related soil proteins (GRSP), are sticky organic substances produced by arbuscular mycorrhizal fungi (AMF). This review summarizes the information on i) the biochemical nature, physical state and origin of GRSP, ii) GRSP decomposition and residence time in soil, iii) GRSP functions, in particular the physical, chemical, and biochemical roles for soil aggregation and carbon (C) sequestration, and finally iv) how land use and agricultural management affect GRSP production and subsequently, organic C sequestration. GRSP augment soil quality by increasing water holding capacity, nutrient storage and availability, microbial and enzymatic activities, and microbial production of extracellular polysaccharides. After release into the soil, GRSP become prone to microbial decomposition due to stabilization with organic matter and sesquioxides, and thereby increasing the residence time between 6 and 42 years. Temperate soils contain 2-15 mg GRSP g-1, whereas arid and semiarid grasslands amount for 0.87-1.7 mg g-1, and GRSP are lower in desert soils. GRSP content is highest in acidic soils as compared to neutral and calcareous soils. Conservation tillage, organic fertilizers and AMF inhabiting crops (e.g. maize, sorghum, soybean, and wheat) increase GRSP production and transform C into stable forms, thereby sustaining soil health and reducing CO2 emissions. Crop rotations with non-mycorrhizal species (e.g. rapeseed) and fallow soils reduce AMF growth and consequently, the GRSP production. The GRSP production increases under nutrient and water deficiency, soil warming and elevated CO2. In the context of global climate change, increased C sequestration through GRSP induced aggregate formation and organic matter stabilization prolong the mean residence time of soil C. Protecting soils against degradation under intensive land use, stable aggregate formation, and prolonging the residence time of C calls for strategies that maximize GRSP production and functions based on reduced tillage, AMF-relevant crop rotations and organic farming.

Methylotroph bacteria and cellular metabolite carotenoid alleviate ultraviolet radiation-driven abiotic stress in plants.

Increasing UV radiation in the atmosphere due to the depletion of ozone layer is emerging abiotic stress for agriculture. Although plants have evolved to adapt to UV radiation through different mechanisms, but the role of phyllosphere microorganisms in counteracting UV radiation is not well studied. The current experiment was undertaken to evaluate the role of phyllosphere Methylobacteria and its metabolite in the alleviation of abiotic stress rendered by ultraviolet (UV) radiation. A potential pink pigmenting methylotroph bacterium was isolated from the phylloplane of the rice plant (oryzae sativa). The 16S rRNA gene sequence of the bacterium was homologous to the Methylobacter sp. The isolate referred to as Methylobacter sp N39, produced beta-carotene at a rate (µg ml-1 d-1) of 0.45-3.09. Biosynthesis of beta-carotene was stimulated by brief exposure to UV for 10 min per 2 days. Carotenoid biosynthesis was predicted as y = 3.09 × incubation period + 22.151 (r 2 = 0.90). The carotenoid extract of N39 protected E. coli from UV radiation by declining its death rate from 14.67% min-1 to 4.30% min-1 under UV radiation. Application of N39 cells and carotenoid extract also protected rhizobium (Bradyrhizobium japonicum) cells from UV radiation. Scanning electron microscopy indicated that the carotenoid extracts protected E. coli cells from UV radiation. Foliar application of either N39 cells or carotenoid extract enhanced the plant's (Pigeon pea) resistance to UV irradiation. This study highlight that Methylobacter sp N39 and its carotenoid extract can be explored to manage UV radiation stress in agriculture.

Deficiency of phyto-available sulphur, zinc, boron, iron, copper and manganese in soils of India.

Nutrient deficiencies in soil-crop contexts and inappropriate managements are the important reasons for low crop productivity, reduced nutritional quality of agricultural produce and animal/human malnutrition, across the world. The present investigation was carried out to evaluate nutrient deficiencies of sulphur (S) and micronutrients [zinc (Zn), boron (B), iron (Fe), copper (Cu) and manganese (Mn)] in agricultural soils of India for devising effective management strategies to achieve sustainable crop production, improved nutritional quality in crops and better animal/human health. A total of 2,42,827 surface (0-15 cm depth) soil samples were collected from agriculture fields of 615 districts lying in 28 states of India and were analysed for available S and micronutrients concentration. The study was carried out under the aegis of All India Coordinated Research Project on Micro- and Secondary-Nutrients and Pollutant Elements in Soils and Plants. The mean concentrations were 27.0 ± 29.9 mg kg-1 for available S, 1.40 ± 1.60 mg kg-1 for available Zn and 1.40 ± 4.70 mg kg-1 for available B, 31.0 ± 52.2 mg kg-1 for available Fe, 2.30 ± 3.50 mg kg-1 for available Cu and 17.5 ± 21.4 mg kg-1 for available Mn. There were variable and widespread deficiencies of S and micronutrients in different states. The deficiencies (acute deficient + deficient + latent deficiency) of S (58.6% of soils), Zn (51.2% of soils) and B (44.7% of soils) were higher compared to the deficiencies of Fe (19.2% of soils), Cu (11.4% of soils) and Mn (17.4% of soils). Out of 615 districts, > 50% of soils in 101, 131 and 86 districts were deficient in available S, available Zn and available B, respectively. Whereas, > 25% of soils in 83, 5 and 41 districts had deficiencies of available Fe, available Cu and available Mn, respectively. There were occurrences of 2-nutrients deficiencies such S + Zn (9.30% of soils), Zn + B (8.70% of soils), S + B (7.00% of soils) and Zn + Fe (5.80% of soils) to a greater extent compared to the deficiencies of Zn + Mn (3.40% of soils), S + Fe (3.30% of soils), Zn + Cu (2.80% of soils) and Fe + B (2.70% of soils). Relatively lower % of soils were deficient in 3-nutrients (namely S + Zn + B, S + Zn + B and Zn + Fe + B), 4-nutrients (namely Zn + Fe + Cu + Mn) and 5-nutrients (namely Zn + Fe + Cu + Mn + B) simultaneously. The information regarding the distribution of deficiencies of S and micronutrients (both single and multi-nutrients) could be used by various stakeholders for production, supply and application of right kind of fertilizers in different districts, states and agro-ecological regions of India for better crop production, crop nutritional quality, nutrient use efficiency, soil health and for tackling human and animal malnutrition.

Ecotoxicological effect of TiO2 nano particles on different soil enzymes and microbial community.

TiO2 nano particles (NPs) are one of the most produced nanoparticles in the world which are increasingly being released in to the soil. Soils are exposed to various level of concentration of TiO2 NPs, which has raised concern over the adverse influence on soil microbial community, in turn on ecosystem functions. Although, increasing number of studies on ecotoxicological effect of TiO2 NPs are coming up recently, however, a common conscience has yet to be reached regarding the impact of TiO2 NPs on soil microbial community and processes. Moreover, very few studies have targeted soil enzymes which are being considered as sensitive indicator of soil health. Therefore, the present study has been carried out to estimate the ecotoxicological effect of various doses of TiO2 NPs (5, 10, 20, 40, 80, 100 mg kg-1 soil) on different soil enzymes and microbial community structure. Results revealed that soil enzyme activities and microbial biomass had a uniform trend where the value increased up to the dose of 20 mg TiO2 NPs kg-1 soil and there onwards reduced drastically up to 100 mg TiO2 NPs kg-1 soil dose. On the contrary, soil respiration and metabolic quotient kept increasing up to 100 mg TiO2 NPs kg-1 soil dose indicating sub-lethal stress on microbial community. Nevertheless, the structure of microbial community had slightly different trend where the biomass of total phospho lipid fatty acid (PLFA), Gram positive, Gram negative bacteria, fungi, actinomyctetes and anaerobes were found to be increased up to dose of 80 mg TiO2 NPs kg-1 soil, but, significantly declined at 100 mg TiO2 NPs kg-1 soil dose. Furthermore, temperature effect on TiO2 NPs toxicity had exhibited a less negative impact at 40 °C rather than at 25 °C. In addition alteration index (AI3), an integrated indicator of C, N, P cycling of soils as well as a well-documented indicator of soil pollution, has been found to be regulated by soil respiration, clay content, anaerobe and eukaryote for AI3-Acid Phos. and by fungi to bacteria ratio, soil respiration, microbial biomass and Gram positive bacteria for AI3-Alk. Phos. Overall, the study provided valuable information regarding ecotoxicological impact of environmentally relevant concentrations of TiO2 NPs in clay loam soils as well as improved our perception regarding the impact of NPs on soil functioning.

Preparation of novel biodegradable starch/poly(vinyl alcohol)/bentonite grafted polymeric films for fertilizer encapsulation.

Sufficient hydroxyl moiety, ease of accessibility, biodegradability and reaction compatibility with other molecules make starch a basic ingredient for polymeric synthesis and to prepare encapsulated controlled release fertilizers. This article aims to prepare biodegradable clay-polymeric (starch/PVA) blended encapsulating films (CPSBs) from starch/PVA and economically feasible clay-fractioned bentonite for CPSB-encapsulated diammonium phosphate (DAP) production. The XRD, TEM and FTIR spectroscopy recognized the compatibility of bentonite with starch/PVA blend; several micropores in CPSB surface was visible through SEM. Relative crystallinity index, density of CPSBs increased with increasing bentonite content (0-20 wt%); but, porosity, water absorption was decreased. Half-life of CPSB-10 was 37.4, 40.1 and 51.9 days with Aspergillus awamori, Trichoderma viride and uninoculated soil, respectively. Nitrogen (N) and phosphorus (P) release data from CPSB-encapsulated-DAP and uncoated DAP fitted well to Korsmeyer-Peppas model. Overall, greater bentonite content stabilizes the CPSB structure and CPSB-encapsulation reduced the N and P release from DAP.

Potential of cotton for remediation of Cd-contaminated soils.

The present research was conducted to study the potential of cotton for the remediation of soils contaminated with Cd, to understand the biochemical basis of its tolerance to, and to investigate the plant-microbe interaction in the rhizosphere for enhancement of phytoextraction of Cd. Cotton (Bt RCH-2) was exposed to four Cd levels (0, 50, 100, and 200 mg/kg soil) in a completely randomised design and found that the plant could tolerate up to 200 mg/kg soil. Cd stress increased the total phenol, proline, and free amino acid contents in the plant leaf tissue compared with control but inhibited basal soil respiration, fluorescein diacetate hydrolysis, and activities of several enzymes viz. dehydrogenase, phosphatases, and ß-glucosidase in the soil over control. The concentration of Cd in the shoot was less than the critical concentration of 100 µg/g dry weight, and bioconcentration and translocation factors were < 1 to classify the plant as a hyperaccumulator of Cd. This was further confirmed by another experiment in which the cotton plant was exposed various higher levels of Cd (200, 400, 600, 800, and 1000 mg/kg soil). Though the concentration of Cd in the shoot was > 100 µg g -1dw beyond 600 mg Cd/kg soil, the bioconcentration and translocation factors were < 1. The study on plant-microbe (Aspergillus awamori) interaction revealed that the fungus did not affect the absorption of Cd by cotton. It was concluded that the cotton was classified as an excluder of Cd and therefore could be suitable for the phytostabilization of Cd-contaminated soils.

In situ decomposition of crop residues using lignocellulolytic microbial consortia: a viable alternative to residue burning.

Open field burning of crop residue causes severe air pollution and greenhouse gas emission contributing to global warming. In order to seek an alternative, the current study was initiated to explore the prospective of lignocellulolytic microbes to expedite in situ decomposition of crop residues. Field trials on farmers' field were conducted in the state of Haryana and Maharashtra, to target the burning of rice and wheat residue and sugarcane trash, respectively. A comparative study among crop residue removal (CRR), crop residue burning (CRB) and in situ decomposition of crop residues (IND) revealed that IND of rice and wheat residues took 30 days whereas IND of sugarcane trash took 45 days. The decomposition status was assessed by determining the initial and final lignin to cellulose ratio which increased significantly from 0.23 to 0.25, 0.21 to 0.23 and 0.24 to 0.27 for rice, wheat residues and sugarcane trash, respectively. No yield loss was noticed in IND for both rice-wheat system and sugarcane-based system; rather IND showed relatively better crop yield as well as soil health parameters than CRB and CRR. Furthermore, the environmental impact assessment of residue burning indicated a substantial loss of nutrients (28-31, 23-25 and 51-77 kg ha-1 of N+P2O5+K2O for rice, wheat and sugarcane residue) as well as the emission of pollutants to the atmosphere. However, more field trials, as well as refinement of the technology, are warranted to validate and establish the positive potential of in situ decomposition of crop residue to make it a successful solution against the crop residue burning.

Tolerance of cotton to elevated levels of Pb and its potential for phytoremediation.

Two experiments were conducted to determine the cotton plant's tolerance to Pb and its remediation potential. In the first experiment, the phytoremediation potential was determined by exposing the plant to four levels of Pb (0, 500, 750, and 1000 mg kg-1). The cotton plant exhibited an excellent tolerance index at Pb 1000 mg kg-1 (root 78.65% and shoot 93.08%) and lower grade of growth inhibition (root 21.35% and shoot 6.92%). Pb stress resulted in higher leakage of electrolytes and increased the synthesis of higher proline, total phenol, and free amino acid contents to mitigate stress. The plant could not meet the criteria of a hyperaccumulator of Pb. The concentration of Pb in the shoot was a mere 96 µg g-1 dry wt (< the critical judging concentration of 1000 µg g-1 dry wt), and bioconcentration and translocation factors were <1. The study established that cotton exhibited an exclusion mechanism of Pb. Further, the translocation efficiency (TE %) was very low, i.e., <50% (ranged from 49% at 500 mg kg-1 to 42% at 1000 mg kg -1), and the % of Pb removed by the crop was too little (on an average 0.1%). Pb inhibited the dehydrogenase activity (DHA) by 76%, fluorescein diacetate (FDA) hydrolysis by 60%, and ß-glucosidase activity by 20%. However, applied Pb increased the population of actinomycetes by 3.21 times, but significantly decreased heterotrophic bacteria by 3.40 times and N2 fixers by over 53% over control. In the second experiment, the plant was exposed to very high Pb (0, 1000, 1500, 2000, 2500, and 3000 mg kg -1) to determine the concentration up to which the plant will survive. The investigation revealed that plants could survive up to Pb 3000 mg kg-1. It confirmed the first experiment in the tolerance index, grade of growth inhibition, bioconcentration factor, translocation factor, and partitioning of Pb. Therefore, it was concluded that the cotton plant was an excluder of Pb and could be effectively cultivated for the phytostabilization of soils polluted with Pb.

Isolation of a broad spectrum antimicrobial producing thermophilic Bacillus and characterization of its antimicrobial protein.

The hot spring water of Atri in India was believed to have disease curing property. An antibacterial producing organism was isolated and identified as Bacillus paralicheniformis by morphology, microscopy, and 16S-rRNA. Its secretion inhibited bacteria, yeast, and fungus in well-diffusion-method. The secreted antimicrobial was a 16.74 kDa protein homologous of chicken-lysozyme-C. The novel lysozyme's activities were recorded under different parameters. It was active from pH 5-9 and endured up to 60 °C for 120 min. Complete cell wall lysis of S. flexneri and P. aeruginosa was observed under a microscope at 4500× with a minimum inhibitory concentration of 7.8 µg/ml, while others required a higher dose, i.e., 13 µg/ml, and 20 µg/ml for E.coli and S. typhimurium, respectively. The discovered lysozyme has the extraordinary potential to lyse Gram-positive bacteria, yeast, fungus, and more efficiently lyse chick-lysozyme-C resistant lipopolysaccharide rich Gram-negative bacteria's outer cell wall.

Evaluation of Furcraea foetida (L.)Haw. for phytoremediation of cadmium contaminated soils.

In the present study, we evaluated Furcraea foetida for the phytoremediation of cadmium (Cd)-contaminated soils. We selected F. foetida because it is a drought-resistant plant, produces high biomass, and needs minimum maintenance. It belongs to the leaf fiber group of plants and therefore has economic importance. Since it is a non-edible crop, there is no danger of food chain contamination. Despite possessing these ideal characteristics, surprisingly, to date, the plant is underutilized for phytoremediation purposes. Therefore, to evaluate the phytoremediation potential of the plant, we exposed it to five levels of cadmium (0, 25, 50, 100, and 200 mg Cd kg-1 soil) and studied its influence on growth, dry matter production, uptake, and translocation efficiency. The plant showed good tolerance to Cd 200 mg kg-1 soil without exhibiting any visible toxicity symptoms. The metal mainly accumulated in the roots (233 µg g-1dw), followed by leaf (51 µg g-1 dw). The bioconcentration factor was > 1, but the translocation factor was < 1. The plant was not classified as a hyperaccumulator of Cd; however, because of its high uptake (897 µ g-1 plant) and translocation efficiency (78%), we concluded that the plant could be utilized for phytoextraction of Cd from soils with low to moderately contaminated soils.

Effects of Co-composting of Municipal Solid Waste and Pigeon Pea Biochar on Heavy Metal Mobility in Soil and Translocation to Leafy Vegetable Spinach.

An experiment was conducted to study the effects of co-composted products of municipal solid waste (MSW) and pigeon pea biochar (PPB) on heavy metal mobility in soil and its uptake by spinach. Application of municipal solid waste biochar co-compost (MSWBC) significantly (p ≤ 0.05) reduced the heavy metal content in spinach leaves and roots compared to municipal solid waste compost (MSWC) amended soil. The percent decrease in spinach leaf following the application of MSWBC-10% PPB compared to MSWC was 20.62%, 28.95%, 36.02%, 41.88%, 41.50%, and 41.23% for Cu, Cd, Pb, Cr, Ni, and Zn, respectively. The dry matter yield of spinach and soil organic carbon (SOC) content in soil amended with MSWBC-10% PPB was significantly increased by 32.75% and 47.73%; and 17.62% and 27.45% relative to control and MSWC amended soil. The study concludes that co-composted product, MSWBC, stabilized heavy metals in MSW, reduced their uptake by spinach and thus making it a viable option for safe disposal of MSW.

Nitrous oxide production from soybean and maize under the influence of weedicides and zero tillage conservation agriculture.

Current experiment envisages evaluating N2O production from nitrification and denitrification under the influence of weedicides, cropping systems and conservation agriculture (CA). The weed control treatments were conventional hand weeding (no weedicide), pre emergence weedicide pendimethalin and post emergence weedicide imazethapyr for soybean, atrazine for maize. Experiment was laid out in randomized block design with three replicates. Soils were collected from different depths and incubated at different moisture holding capacity (MHC). N2O production from nitrification varied from 2.77 to 6.04 ng N2O g-1 soil d-1 and from denitrification varied from 0.05 to 1.34 ng N2O g-1 soil d-1. Potential nitrification rate (0.16-0.39 mM NO3 produced g-1 soil d-1) was higher than potential denitrification rate (0.45-0.93 mM NO3 reduced g-1 soil d-1). N2O production, nitrification, denitrification, and microbial gene abundance were higher in maize than soybean. Both N2O production and nitrification decreased (p < 0.05) with soil depth, while denitrification increased (p < 0.05) with soil depth. Abundance of eubacteria and ammonia oxidizing bacteria (AOB) were high (p < 0.01) at upper soil layer and declined with depth. Abundance of ammonia oxidizing archaea (AOA) increased (p < 0.05) with soil depth. Study concludes that intensive use of weedicides in CA may stimulate N2O production.

Do methanotrophs drive phosphorus mineralization in soil ecosystem?

Experiments were carried out to elucidate linkage between methane consumption and mineralization of phosphorous (P) from different P sources. The treatments were (i) no CH4 + no P amendment (absolute control), (ii) with CH4 + no P amendment (control), (iii) with CH4 + inorganic P as Ca3(PO4)2, and (iv) with CH4 + organic P as sodium phytate. P sources were added at 25 µg P·(g soil)-1. Soils were incubated to undergo three repeated CH4 feeding cycles, referred to as feeding cycle I, feeding cycle II, and feeding cycle III. CH4 consumption rate k (µg CH4 consumed·(g soil)-1·day-1) was 0.297 ± 0.028 in no P amendment control, 0.457 ± 0.016 in Ca3(PO4)2, and 0.627 ± 0.013 in sodium phytate. Rate k was stimulated by 2 to 6 times over CH4 feeding cycles and followed the trend of sodium phytate > Ca3(PO4)2 > no P amendment control. CH4 consumption stimulated P solubilization from Ca3(PO4)2 by a factor of 2.86. Acid phosphatase (µg paranitrophenol released·(g soil)-1·h-1) was higher in sodium phytate than the no P amendment control. Abundance of 16S rRNA and pmoA genes increased with CH4 consumption rates. The results of the study suggested that CH4 consumption drives mineralization of unavailable inorganic and organic P sources in the soil ecosystem.

Classification of Pigeonpea (Cajanus cajan (L.) Millsp.) Genotypes for Zinc Efficiency.

Pigeonpea (Cajanus cajan (L.) Millsp.) is grown globally for its protein-rich seed. However, low availability of soil zinc (Zn) adversely affects the seed yield of pigeonpea. The present study was therefore conducted to assess the Zn efficiency of pigeonpea genotypes based on seed yield and seed Zn uptake efficiency. Field experiments were conducted at the Indian Council of Agricultural Research-Indian Institute of Soil Science, Bhopal, India with twenty different pigeonpea genotypes and two levels of Zn application under a split-plot design. The two levels of Zn were low (without application of Zn fertilizer) and high (with application of 20 kg Zn ha-1 (as ZnSO4∙7H2O) as basal soil application, in conjunction with three foliar sprays of 0.50% (w/v) ZnSO4∙7H2O aqueous solution) (with 0.25% lime as neutralizing agent) at flowering, pod formation, and pod filling stages). Application of Zn improved plant height, branches plant-1, pods plant-1, seeds pod-1, and 100 seed weight of pigeonpea genotypes differently. The mean seed yield, seed Zn concentration, and seed Zn uptake of the genotypes increased from 1.71 to 2.12 t ha-1, 32.4 to 43.0 mg kg-1, and 54.9 to 90.6 g ha-1, respectively, with application of Zn. The seed yield efficiency index (SYEI) and Zn uptake efficiency index (ZUEI) of pigeonpea genotypes varied from 67.0 to 92.5 and from 47.0 to 69.9, respectively. Based on SYEI and ZUEI, the genotypes were classified as efficient and responsive (Virsa Arhar-1, GT-1, GT-101, SKNP 05-05, BDN-2, AAUT 2007-04, BSMR 853, T 15-15, DT 23, Pusa 9), efficient and non-responsive (ICPL 87119, PKV Trombay), inefficient and responsive (AKT 8811, Hisar Paras), and inefficient and non-responsive (AAUT 2007-10, JKM 7, Hisar Manak, C 11, Hisar HO2-60, GAUT 93-17). The efficient and responsive genotypes are the most useful as they yield well under low soil Zn conditions and also respond to Zn fertilizer application. The inefficient and responsive genotypes could be utilized for plant breeding programs by plant breeders for identification and utilization of responsive traits.

Nitrification Rates Are Affected by Biogenic Nitrate and Volatile Organic Compounds in Agricultural Soils.

The processes regulating nitrification in soils are not entirely understood. Here we provide evidence that nitrification rates in soil may be affected by complexed nitrate molecules and microbial volatile organic compounds (mVOCs) produced during nitrification. Experiments were carried out to elucidate the overall nature of mVOCs and biogenic nitrates produced by nitrifiers, and their effects on nitrification and redox metabolism. Soils were incubated at three levels of biogenic nitrate. Soils containing biogenic nitrate were compared with soils containing inorganic fertilizer nitrate (KNO3) in terms of redox metabolism potential. Repeated NH4-N addition increased nitrification rates (mM NO3 1- produced g-1 soil d-1) from 0.49 to 0.65. Soils with higher nitrification rates stimulated (p < 0.01) abundances of 16S rRNA genes by about eight times, amoA genes of nitrifying bacteria by about 25 times, and amoA genes of nitrifying archaea by about 15 times. Soils with biogenic nitrate and KNO3 were incubated under anoxic conditions to undergo anaerobic respiration. The maximum rates of different redox metabolisms (mM electron acceptors reduced g-1 soil d-1) in soil containing biogenic nitrate followed as: NO3 1- reduction 4.01 ± 0.22, Fe3+ reduction 5.37 ± 0.12, SO4 2- reduction 9.56 ± 0.16, and CH4 production (µg g-1 soil) 0.46 ± 0.05. Biogenic nitrate inhibited denitrificaton 1.4 times more strongly compared to mineral KNO3. Raman spectra indicated that aliphatic hydrocarbons increased in soil during nitrification, and these compounds probably bind to NO3 to form biogenic nitrate. The mVOCs produced by nitrifiers enhanced (p < 0.05) nitrification rates and abundances of nitrifying bacteria. Experiments suggest that biogenic nitrate and mVOCs affect nitrification and redox metabolism in soil.

Fe-exchanged nano-bentonite outperforms Fe3O4 nanoparticles in removing nitrate and bicarbonate from wastewater.

Nitrate (NO3-) and bicarbonate (HCO3-) are harmful for the water quality and can potentially create negative impacts to aquatic organisms, crops and humans. This study deals with the removal of NO3- and HCO3- from contaminated wastewater using Fe-exchanged nano-bentonite and Fe3O4 nanoparticles. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurement and particle size analysis revealed that the adsorbents fall under the nano-scale size range with high specific surface area, and Fe was successfully exchanged in the nano-bentonite clay. The kinetics of adsorption was well defined by pseudo-first order and pseudo-second order kinetic models for both NO3- and HCO3-. The Fe-exchanged nano-bentonite was a better performing adsorbent of the oxyanions than Fe3O4 nanoparticles. According to the Sips isothermal model, the Fe-exchanged nano-bentonite exhibited the highest NO3- and HCO3- adsorption potential of 64.76 mg g-1 and 9.73 meq g-1, respectively, while the respective values for Fe3O4 nanoparticles were 49.90 mg g-1 and 3.07 meq g-1. Thus, inexpensiveness and easy preparation process of Fe-exchanged nano-bentonite make it attractive for NO3- and HCO3- removal from contaminated wastewater with significant environmental and economic benefits.