Effects of different types of humic acid isolated from coal on soil NH3 volatilization and CO2 emissions

Metagenomic characterization of biomethane transformation by lipid-catalyzed anaerobic fermentation of lignite

The present study aims at using lipid in a novel way to improve the efficiency of methane production from lignite anaerobic digestion. The obtained results showed an increase by 3.13 times of the cumulative biomethane content of lignite anaerobic fermentation, when 1.8 g lipid was added. The gene expression of functional metabolic enzymes was also found to be enhanced during the anaerobic fermentation. Moreover, the enzymes related to fatty acid degradation such as long-chain Acyl-CoA synthetase and Acyl-CoA dehydrogenase were increased by 1.72 and 10.48 times, respectively, which consequently, accelerated the conversion of fatty acid. Furthermore, the addition of lipid enhanced the carbon dioxide trophic and acetic acid trophic metabolic pathways. Hence, the addition of lipids was argued to promote the production of methane from lignite anaerobic fermentation, which provided a new insight for the conversion and utilization of lipid waste.

Biodegradation of organic compounds in the coal gangue by Bacillus sp. into humic acid

Coal gangue (CG), one of the world's largest industrial solid wastes produced during coal mining, is extremely difficult to be used owing to its combined contents of clay minerals and organic macromolecules. This study explored a novel process of degrading the harmful organic compounds in the CG into humic acid using a biological method characterized by scanning electron microscope-energy dispersive spectrometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and elemental analyzer. The results reveal that adding selected Bacillus sp. to the CG for 40 days can increase the humic acid content by ~ 17 times, reaching 17338.17 mg/kg, which is also the best level for promoting plant growth. FTIR and XPS spectra show that the organic compounds in the CG transforms primarily from C=C to C=O, COOH, and O-H groups, indicating that the organic compounds are gradually oxidized and activated, improving the humic acid concentration of soil. In addition, Bacillus sp. decreases pH and benzo[a]pyrene contents, and increases the content of available nutrients. After microbial degradation, coal gangue can be turned into ecological restoration materials.

Effective adsorption of ammonium nitrogen by sulfonic-humic acid char and assessment of its recovery for application as nitrogen fertilizer

Ammonium nitrogen (NH₄⁺-N) is a form of N that is non-negligible in eutrophication water as well as an essential nutrient for plants growing. Carbon materials are considered superior for the adsorption recovery of excess NH₄⁺-N in water bodies. The sulfonic-humic acid char (SHAC) was prepared from humic acid (HA) by pyrolysis and hydrothermal grafting with sodium allyl sulfonate. SEM-mapping, FTIR and XPS results indicated that sulfonic groups (-SO₃H) were successfully grafted onto SHAC. The adsorption kinetic fitting displayed that the adsorption of NH₄⁺-N by SHAC conformed to the pseudo-second-order kinetics and could reach equilibrium in about 100 min. The maximum adsorption of NH₄⁺-N by SHAC was 77.24 mg/g, it was mainly contributed by electrostatic attraction, hydrogen bonding and pore volume sites. SHAC adsorption of NH₄⁺-N resulted in the material SHAC-N, which desorption rate was considerably slower than that of commercially available ammonium chloride (NH₄Cl) fertilizer and in accordance with the first order model. Wheat growth experiments revealed that the quality of wheat treated with SHAC-N (higher 100-grain weight and lower nitrate content) was better than that of NH₄Cl fertilizer. In addition, the higher residual NH₄⁺-N in the SHAC-N treatment soil facilitated subsequent crop planting. These results indicated that SHAC has excellent adsorption and slow release of NH₄⁺-N, and has great potential application for N management in environment and agriculture.

Effect of chemical fertilizer and humic acid on cabbage leaves' N, P, K and S concentrations (Brassica oleracea var. capitata L.)

A field study was carried out in one of the fields of Jdeidet Al-Shatt district is, located 30 km from the center of Baquba in Diyala governorate, during the autumnal season 2021-2022 on silty loam soil classified to a level under the Typic Torrifluvent according to the modern American classification to know the effect of adding chemical fertilizer and humic acid on the availability of nitrogen, phosphorus and potassium concentrations for cabbage leaves, according to of randomized complete block design (RCBD) by using three replicates. The first factor was the chemical compound fertilizer NPK( 20:20:20 ) added at three different levels 0, 150 kg ha-1, 300 kg ha-1, while the second factor was humic acid at three levels 0, 15 kg ha-1, 30 kg ha-1. Fertilizers were added to the soil by making an incision around the plant and were added in two stages, the first when planting and the second 43 days after the date of the first batch. The results of the study showed that adding chemical fertilizer at a level of 300 kg ha-1 led to significant differences in the concentrations of nitrogen, phosphorous, potassium and sulfur elements in the inner leaves, where the concentrations of elements reached 2.55%,0.34%, 2.95%,1.36% respectively, the outer leaves. In contrast, the concentrations of nitrogen, phosphorous and potassium reached 4.00 %, 0.34%, and 2.67%, respectively, While the superiority of the humic acid at the level of 30 kg ha-1 to 2.33%, 0.32%, 2.77%,1.47% in the inner leaves, respectively, while in the outer leaves 3.80 %,0.31 %,2.49%. Keywords: chemical fertilizer, humic acid, concentrations of N,P, K and S, cabbage.

Characteristics of soil CO2 emission and ecosystem carbon balance in wheat-maize rotation field with 4-year consecutive application of two lignite-derived humic acids

Humic acid originating from lignite is a popular resource of organic fertilizer. The effects of humic acid application on crop biomass and soil CO₂ emission charged the regional agro-ecosystem carbon balance. Two kinds of humic acid, obtained from lignite via H₂O₂-oxidation (OHA) and KOH-activation (AHA), were applied in a wheat-maize rotation located field at three levels of 500 (OHA1; AHA1), 1000 (OHA2; AHA2), and 1500 kg hm^-2 (OHA3; AHA3), only chemical fertilizer treatment (CF) as control to investigate the change of soil CO₂ emission, crop yield and ecosystem carbon balance in 2016-2019. During the four experimental years, the trend of cumulative efflux of soil CO₂ was increasing in medium and high dosage humic acid treatments. The grain yield of wheat and maize had the same trend as the cumulative efflux of soil CO₂ due to the increase of soil NO₃^--N and soil available P directly affected by humic acid application. The main factor of cumulative soil CO₂ efflux improvement was soil NO₃^--N and soil available P in 2016, while soil available potassium became key factor in 2019 with the step regression. Net ecosystem productivity (NEP) was used to assess ecosystem carbon balance, which was positive values showed atmospheric CO₂ sink under all the fertilization treatments and increased with the increase of humic acid use level. AHA2 and AHA3 treatments charged the higher NEP in 2019 than 2016. Meanwhile, AHA treatment presented a higher NEP average than OHA treatment with the same applied level. Crop yield and soil available P was the directly positive factor to NEP over four years under the fertilization by SEM analysis. It is recommended that AHA be applied at 1000 kg hm^-2 together with chemical fertilizers to achieve the higher crop yield and a sink of the atmospheric CO₂ in agricultural fields in North China.

Effect of Humic Acid on Soil Physical and Chemical Properties, Microbial Community Structure, and Metabolites of Decline Diseased Bayberry

In recent years, bayberry decline disease has caused significant damage to the bayberry industry. In order to evaluate whether humic acid can be used to effectively control the disease, this research examined the nutritional growth and fruit quality of bayberry, soil physical and chemical properties, soil microbial community structure, and metabolites. Results indicated that the application of humic acid not only improved the vigor and fruit quality of diseased trees, but also increased the diversity of microbial communities in the rhizosphere soil. A great increase was observed in the relative abundance of bacterial genus Mycobacterium and Crossiella; fungal genus Fusarium and Coniosporium. In contrast, a significant decrease was observed in the relative abundance of bacterial genus Acidothermus, Bryobacter, Acidibacter, fungal genus of Geminibasidium and Mycena. Analysis of redundancies (RDA) for microbial communities and soil characteristics showed that the main four variables, including available nitrogen, phosphorus, potassium, and calcium, had a great effect on the composition of bacterial and fungal communities in bayberry rhizosphere soil at the genus level. The main four variables had a greater effect on bacterial communities than on fungal communities. In addition, ABC transporter, arginine and proline metabolism, galactose metabolism, and glutathione metabolism were significantly affected by humic acid, which changed the content of 81 metabolites including 58 significantly down-regulated metabolites such as isohexonic acid and carinitine, and 23 significantly up-regulated metabolites such as acidic acid, guaninosuccinate, lyxose, 2-monoolein, epicatechin, and pentonolactone. These metabolites also significantly correlated with rhizosphere soil microbiota at the phylum, order, and genus levels. In conclusion, the results demonstrated the role of humic acid on plant growth and fruit quality, as well as rhizosphere soil characteristics, microbiota, and secondary metabolites, which provides novel insights into the control of bayberry decline disease.

Mulched drip irrigation and biochar application reduce gaseous nitrogen emissions, but increase nitrogen uptake and peanut yield

Nitrous oxide and ammonia emissions from farmland need to be abated as they directly or indirectly affect climate warming and crop yield. We conducted a two-year field experiment to investigate the effect of biochar applied at two rates (no biochar application vs. biochar applied at 10 t ha^-1) on gaseous nitrogen (N) losses (N₂O emissions and NH₃ volatilization), plant N uptake, residual soil mineral N, and peanut (Arachis hypogaea L.) yield under three irrigation regimes: furrow irrigation (FI), drip irrigation (DI), and mulched drip irrigation (MDI). We found that MDI reduced residual (post-harvest) soil mineral N, cumulative N₂O emissions, and yield-scaled N₂O emissions as compared to FI. Biochar application increased residual soil NO₃^--N and decreased yield-scaled N₂O emissions as compared with the control without biochar application. Under the three irrigation regimes, biochar application decreased cumulative NH₃ volatilization and increased plant N uptake and yield compared with the control. Biochar application improved the sustainability of peanut production and could be used to alleviate the environmental damage associated with gaseous N emissions. Where possible, biochar application under MDI in peanut fields is recommended as a management strategy to minimize gaseous N losses.

Fertilizer type and humic acid improve the growth responses, nutrient uptake, and essential oil content on Coriandrum sativum L

In recent decades, the over-use of chemical fertilizers has imposed many environmental challenges worldwide. Nowadays, organic fertilizers such as vermicompost and livestock manure have gained a huge interest in sustainable agricultural systems. A 2-year field research was conducted as factorial based on a randomized complete block design to assay the fertilizer and humic acid (HA) efficiency on the growth responses and essential oil composition of Coriandrum sativum. The treatments were different fertilizer sources (livestock manure, vermicompost, and chemical fertilizers) and humic acid fertigation before and at the beginning of the flowering stage. The highest protein content was observed under vermicompost × HA application before flowering (0.118 μmol L^-1 and 0.128 μmol L^-1, respectively). Moreover, the co-application of organic fertilizers × HA at the beginning of flowering resulted in a significant increase in the photosynthetic pigments and N, P, K, Fe, Zn, and Mn content. According to the GC-FID and GC-MS analysis, linalool (55.91-63.19%), γ-terpinene (4.65-6.13%), α-pinene (2.64-5.74%), geranyl acetate (3.49-5.51%), 2-dodecanal (2.92-4.46%), menthol (1.33-3.90%), p-cymene (1.73-2.24%), and geraniol (1.25-2.15%) were the main essential oil constituents. The top linalool content was obtained by using chemical fertilizers and vermicompost × HA at the flowering onset stage. In general, the results revealed that chemical fertilizers could be replaced with vermicompost × HA and their co-application positively influenced the growth responses and the essential oil composition of coriander. Furthermore, the results obtained would be advisable to the extension section and the pioneer farmers to amend the large-scale production systems in favor of environmental health.

Surface tuned polyethersulfone membrane using an iron oxide functionalized halloysite nanocomposite for enhanced humic acid removal

Nanomodification of ultrafiltration (UF) membranes has been shown to be a simple and efficient technique for the preparation of high-performance membranes. In this work, an iron oxide functionalized halloysite nanoclay (Fe-HNC) nanocomposite was prepared and used as a nanofiller for polyethersulfone (PES) membranes. The effect of Fe-HNC concentration on the filtration performance of the membrane was investigated by varying the nanocomposite dosage (0-0.5 wt %) in the casting dope. Various characterization studies showed that the incorporation of Fe-HNC nanocomposites improved the membrane morphology and enhanced the surface properties, thermal stability, mechanical strength, hydrophilicity, and porosity. The permeability to pure water and filtration of humic acid (HA) were significantly improved by incorporating Fe-HNC into the PES membranes. The membrane with Fe-HNC loading of 0.1 wt % exhibited the highest pure water permeability (174.3 L/(m² h bar)) and removal of HA (90.1 %), which were 1.8 times and 29 % higher, respectively than the pristine PES membrane. Moreover, fouling studies showed the enhanced antifouling ability of the Fe-HNC nanocomposites modified PES membranes, especially against irreversible fouling. Continuous membrane regeneration-based fouling removal studies from HA showed that the PES/0.1 wt % Fe-HNC membrane exhibited a high fouling recovery of 70.4 % with very low reversible and irreversible fouling resistance of 9.61 % and 14.78 %, respectively, compared to the pristine PES membrane (fouling recovery: 40.4 %; reversible fouling: 21.7 %; irreversible fouling: 20.1 %). Overall, the Fe-HNC nanocomposite proved to be an effective nanomodifier for improving the permeability of PES membranes and the antifouling ability to treat HA polluted aqueous streams.

Effects of microplastics on humification and fungal community during cow manure composting

The effect of microplastics (MPs) on the biological treatment of organic waste has been extensively studied, but little is known about the influence of different MPs on composting humification and the fungal community. In this study, PE, PVC, and PHA MPs were individually mixed with cow dung and sawdust and then composted. The results showed that different MPs had various influences on humification, and the humic acid to fulvic acid ratio of all MP-added treatments (0.44-0.83) was lower than that of the control (0.91). During the composting process, Ascomycota (26.32-89.14%) and Basidiomycota (0.47-4.78%) are the dominant phyla in all treatments and all microplastics decreased the diversity and richness of the fungal community at the thermophilic stage of composting. Exposure to MPs had an obvious effect on the fungal community at the genus level, and the addition of PHA and PE MPs increased the relative abundance of phytopathogenic fungi. LEfSe and network analysis indicated that MPs reduced the number of biomarkers and led to a simpler and more unstable fungal community structure compared to the control. This study has important implications for assessing microplastic pollution and organic waste disposal.

Efficiency and mechanism of reducing ammonia volatilization in alkaline farmland soil using Bacillus amyloliquefaciens biofertilizer

Ammonia volatilization from the farmland caused by the application of synthetic nitrogen fertilizer is the most important source of anthropogenic ammonia emissions. Biofertilizer application has been considered as an alternative option for agriculture sustainability and soil improvement. In this study, field trials were carried out to investigate the efficiency of Bacillus amyloliquefaciens (BA) biofertilizer on alleviating ammonia volatilization in alkaline farmland soil and increasing crop yield and nitrogen utilization. Potential response mechanisms were investigated from soil enzyme, nitrogen cycle function genes and microbial community levels. Compared with conventional fertilization, BA biofertilizer application reduced the ammonia volatilization by 68%, increased the crop yield and nitrogen recovery by 19% and 19%, respectively. Soil enzyme activity analysis showed that BA biofertilizer inhibited the urease activity and enhanced the potential ammonia oxidation (PAO). In addition, BA biofertilizer application also increased the bacterial amoA gene abundance, while decreased the ureC gene abundance. BA biofertilizer also significantly altered the community structure and composition, and especially raised the abundance of ammonia oxidation bacteria (AOB), while no changes were observed in abundance of nitrite oxidation bacteria (NOB). Briefly, BA biofertilizer was approved to reduce the transformation of fertilizer nitrogen to NH₄⁺-N, simultaneously accelerating NH₄⁺-N into the nitrification process, thus decreasing the NH₄⁺-N content remained in alkaline soil and consequently alleviating the ammonia volatilization. Thus, these results suggested that the application of BA biofertilizer is a feasible strategy to improve crop yields and reduce agricultural ammonia emissions.