Ratio Of Humic Acid Research Articles

Enhancement of soil humic acid hydrophobicity by 5 consecutive years of full-amount straw shallow-mixed field return

Crop yield is directly influenced by the storage and stabilisation of soil organic carbon (SOC), which is determined by the hydrophobicity of soil humic acid (HA). Changes in soil HA hydrophobicity, humic substances, SOC and crop yield were compared after the application of different amounts of straw returns in the field, and the contribution of straw application in enhancing HA hydrophobicity was examined. The treatments included no straw application and soil stirring, no straw application with soil stirring, application of half-amount straw shallow-mixed field return, application of full-amount straw shallow-mixed field return and application of double-amount straw shallow-mixed field return. Using elemental analysis, infrared spectroscopy and fluorescence spectroscopy, the structural hydrophobicity of soil HA was exhaustively characterised. The results showed that the hydrogen to carbon ratio of HA increased by 11.46 %, the ratio of hydrophobic to hydrophilic intensity increased by 21.02 %, and the ratio of peak B to peak A fluorescence intensity decreased by 32.21 % after 5 years of full amount straw shallow-mixing field return compared to no straw application and soil stirring. The observed results indicate that the augmentation in hydrophobicity stimulates the formation of HA, enhances soil humification, elevates SOC content by 9.78 % and potentially contributes to the ultimate crop yield increase by 22.98 %. Compared with stirring the soil, the contribution rate of applying full amount of straw to increase HA hydrophobicity was 49.57–62.05 %, and the contribution rate to increase SOC and yield were 54.59 % and 76.37 %, respectively. While stirring the soil contributed to increasing hydrophobicity, straw application persisted as the primary factor in enhancing hydrophobicity. The findings of this study have significant implications for understanding the mechanism by which straw improves HA hydrophobicity, thereby facilitating carbon sequestration and increasing crop yield.

The role of cattle manure-driven polysaccharide precursors in humus formation during composting of spent mushroom substrate.

The study examined the impact of adding cattle manure to the composting process of Agaricus bisporus mushroom substrate on compost humification. A control group CK comprised entirely of Agaricus bisporus mushroom substrate, while the experimental group CD (70 percent Agaricus bisporus mushroom substrate and 30 percent cattle manure) comprised the two composting treatments that were established. The study determined that the addition of cow dung has promoted the formation of humus components. Particularly, humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%, respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased by 2.78. It showed that the addition of cow dung accelerated the synthesis and decomposition of precursors, such as polysaccharides, polyphenols, and reducing sugars. Thereby promoting the formation of humic acid. Network analysis revealed that adding cow dung promoted microbial interactions increased the complexity and stability of the bacterial and fungal symbiotic network, enhanced cooperation and reciprocity among microbes, and assisted in transforming fulvic acid (FA) components. Structural equation modeling (SEM) is a multivariate data analysis method for analyzing complex relationships among constructs and core indicators. SEM illustrated that introducing cattle manure into the composting process resulted in alterations to the correlation between physicochemical parameters and the microbial community, in addition to humus formation. Polysaccharides are the primary precursors for polymerization to form HA, which is an essential prerequisite for the conversion of fulvic acid to humic acid. Additionally, microbes affected the formation of humus, with bacteria substantially more influential than fungi. These findings provide new ideas for regulating the degree of humification in the composting process and have important practical implications for optimizing mushroom cultivation and composting techniques today.

Biochar addition accelerates the humification process by affecting the microbial community during human excreta composting

ABSTRACT Biochar addition plays an important role in manure composting, but its driving mechanism on microbial succession and humification process of human excreta composting is still unclear. In the present study, the mechanism of biochar addition was explored by analysing the humification process and microbial succession pattern of human excreta aerobic composting without and with 10% biochar (HF and BHF). Results indicated that BHF improved composting temperature, advanced the thermophilic phase by 1 d, increased the germination index by 49.03%, promoted the growth rate of humic acid content by 17.46%, and raised the compost product with the ratio of humic acid to fulvic acid (HA/FA) by 16.19%. Biochar regulated the diversity of fungi and bacteria, increasing the relative abundance of Planifilum, Meyerozyma and Melanocarpus in the thermophilic phase, and Saccharomonospora, Flavobacterium, Thermomyces and Remersonia in the mature phase, which accelerates the humification. Bacterial communities’ succession had an obvious correlation with the total carbon, total nitrogen, and temperature (P < 0.05), while the succession of fungal communities was influenced by the HA/FA and pH (P < 0.05). This study could provide a reference for the improvement of on-site human excreta harmless by extending the thermophilic phase, and facilitating the humification in human excreta compost with biochar addition.

Efficient recovery and characterization of humic acids from municipal and manure composts: A comparative study

The recovery of humic acids from low-quality compost obtained in municipal solid waste treatment plants provides opportunities for its valorization. This study compares the recovery and properties of the humic acids obtained from municipal mixed waste compost (MMWC) and manure compost. The effects of temperature, time, and KOH concentration on the ratio of humic acids in the extracted liquid and the content of organic carbon of the precipitates were investigated by response surface methodology. Optimal conditions were 30 °C and 24 h for both composts, with a KOH concentration of 0.53 M for MMWC and 0.25 M for manure compost. The manure compost provided a liquid extract richer in humic acids than MMWC (76.6 % vs. 33.7 %), but the precipitates presented similar organic carbon contents (38.1 % vs. 42.4 %). Regarding composition, both humic acids presented higher organic carbon and nitrogen contents than the composts used as feedstock. The extraction and further precipitation of humic acids reduced the concentration of heavy metals. Humic acids from manure compost have a slightly higher average molecular weight (2650 Da) than those from MMWC (1980 Da), while both present similar C/N ratios and degree of aromaticity. Most contaminants of emerging concern present in the original composts were not detected in the humic acids. Thus, it was demonstrated that MMWC constitutes an attractive source of humic acids with properties similar to those obtained from a high-quality compost and, therefore, with potential economic value.

Study on the Corrosion Behavior of Cemented Organic Soil in Dianchi Lake, China.

To study the corrosion behavior of cement soil in peat soil, the experiment involves the preparation of peat soil by incorporating humic acid into cohesive soil with a lower organic matter content. Cement soil samples are then prepared by adding cement to the mixture. These samples are subjected to immersion in fulvic acid solution and deionized water to simulate different working environments of cement soil. The experiment considers immersion time as the variable factor. It conducts observations of apparent phenomena, ion leaching tests, and unconfined compression strength tests on the cement soil. The experiment results are as follows: (1) With increasing immersion time, the surface of the cement soil in the peat soil environment experiences the disappearance of Ca(OH)2 and calcium aluminate hydrate. Additionally, large amounts of bird dropping crystals precipitate on the surface and within the specimen. The cement soil undergoes localized disintegration due to extensive erosion caused by swelling forces. (2) In the peat soil environment, fulvic acid reacts with the hydration products of cement, resulting in partial leaching of ions such as Ca2+, Mg2+, Al3+, and Fe3+ into the immersion solution. The lower the pH of the fulvic acid immersion (indicating higher concentration), the more significant the ion leaching. Increasing the ratio of humic acid to cement can slow down the leaching of ions. The cement soil undergoes dissolutive erosion in the peat soil environment. (3) The peat soil environment exerts both strengthening and corrosive effects on the cement soil. Cement soil without humic acid exhibits noticeable corrosion in the peat soil environment, gradually decreasing strength as immersion time increases. The strength decreases by 83% from 28 to 365 days. In contrast, cement soil with humic acid experiences an initial period of strengthening, leading to a significant increase in strength in the short term (34% increase from 28 to 90 days). However, the corrosive effects gradually dominate, resulting in a decrease in strength over time. The strength decreases by 80% from 90 to 365 days. This study also explores the strengthening effects of peat soil on cement soil. It identifies phenomena such as extensive erosion and new substance precipitation in cement soil.

Characteristics of Humic Acids in Drained Floodplain Soils in Temperate Climates: A Spectroscopic Study

This study aims to assess the characteristics of humic acids (HAs) in floodplain soils. HAs were isolated from the Fluvisols located out of the embankment in the riparian forest (unflooded riparian forest) and within the embankment (inter-embankment), in the area periodically flooded. HAs from these soils were examined for quantity, structure, and humification degree using extraction methods as well as elemental analysis, UV-Vis, FTIR, EPR, and 1HNMR spectroscopies. In the soils after drainage, a significant decrease in HAs has been observed compared to the periodically flooded areas. Obtained results showed that organic matter from periodically flooded soils is more humified and contains HAs with a more aromatic, lignin-like structure compared to the humus matter from unflooded Fluvisols. Humic acids from periodically flooded soil contained a lower amount of C and H compared to those isolated from unflooded soils located out of the embankment, which resulted in a less aliphatic or more aromatic character of their molecules. A higher H/C ratio of HAs from the Fluvisols after drainage exhibits more condensed aromatic ring or substituted ring structures in the molecules. Soils with organic matter with a higher humification index contained HAs with lower radical concentration values in comparison to soils with less humified organic matter. Results obtained show that in flooded areas with periodically reductive conditions, humic acids do not lose as many -OCH3 groups as in better oxidized soils and therefore exhibit a lignin-like aromatic structure. It has been proven that the formation and dynamics of HA transformation may vary due to the water regime in soils.

Qualitative composition of humus and physical and chemical properties of typical chernozem depending on the fertiliser system

The soil-forming process is closely related to the accumulation and circulation of organic substances, which are a source of nutrients for plants released during the mineralisation of humus, so research on determining the qualitative composition of humus is relevant. In this regard, the purpose of this paper is to determine humic and fulvic acids in typical chernozem, depending on the fertiliser system. The leading approaches to solving this problem are conducting field and laboratory studies to determine the quality indicators of humus and dispersion methods to establish the accuracy and reliability of experimental data. Based on the conducted studies, it was observed that the application of an organo-mineral fertiliser system leads to an increase in the content of humic acids, while the insoluble residue shows an increase in carbon content. The utilisation of organo-mineral fertilisers resulted in a reduction in the excessive accumulation of non-humified organic substances. Additionally, the soils in these areas exhibited a higher level of organic substance humification. The combination of organic matter at a rate of 11.5 tonnes per hectare (8 tonnes of manure and 3.5 tonnes of by-products) and mineral fertilizer N27P38K45 in a crop rotation resulted in an increasing trend of the buffering capacity of typical chernozem soil. In this scenario, there was an increase in absorption capacity at the end of the second rotation for grain-legume crop rotation by 6.05 mg/equiv per 100 g, specialised grain-legume rotation by 3.9 mg/equiv per 100 g, and legume rotation by 3.06 mg/equiv per 100 g of soil compared to the beginning of the first rotation. The use of organo-mineral fertilisers increases the third fraction of fulvic acids in specialised grain-legume rotation, which affects the ratio of humic acids to fulvic acids in favour of the humic type of humus formation. The ratio of humic acids to fulvic acids in the grain-planting crop rotation in the organo-mineral system was 2.84 at the end of the second rotation, and 2.24 at the beginning of the first rotation. The research materials are of practical importance for farmers when analysing the fractional-group composition of typical chernozem humus

Impact of long-term manuring and cropping system on stability of humus associated with clay-organic complex

ABSTRACT The objective was to study the impact of ten year’s manuring and fertilization on chemical stability of clay-organic complex (COC) in rice−potato−wheat (R–P–W) and maize−potato−onion (M–P–O) cropping systems. Soil samples were collected from the control, 100% NPK–Fertilizer, 100% N–Vermicompost (VC), 50% NPK–Fertilizer + 50% N–VC, 100% NPK–Fertilizer + crop residue (CR), 100% N–VC + CR. The stability (1/k) of humus C i.e. inverse of humus desorption rate constant (k) in hours (h), in COC was higher in 100% N–VC an1d 00% N–VC + CR in both the cropping systems. The C:N ratio of humic acid (HA) was also higher in the treatments receiving full organics (100% N–VC and 100% N–VC + CR) and showed positive correlation (p < 0.05) with the humus C stability in COC. Long-term manuring treatments created C = N and C–O stretching of aromatic ether in HA extracted from 100% NPK–VC and other selected treatments in both the cropping systems. 100% N–VC and 100%N–VC + CR produced higher stability of humus-C in Inceptisol. The R–P–W imparted higher stability of humus C than M–P–O cropping system.

Preparation of entrapment-based microcolumns for analysis of drug-humic acid interactions by high-performance affinity chromatography

Reversible interactions between drugs and humic acid in water can be an important factor in determining the bioavailability and effects of these pharmaceuticals as micropollutants in the environment. In this study, microcolumns containing entrapped humic acid were used in high-performance affinity chromatography (HPAC) to examine the binding of this agent with the drugs tetracycline, carbamazepine, ciprofloxacin, and norfloxacin. Parameters that were varied to optimize the entrapment of humic acid within HPLC-grade porous silica included the starting concentration of humic acid, the mass ratio of humic acid vs silica, and the method of mixing the reagents with the support for the entrapment process. The highest retention for the tested drugs was obtained when using supports that were prepared using an initial humic acid concentration of 80 mg mL−1 and a humic acid vs silica mass ratio of 600 mg per g silica, along with preincubation of the humic acid with hydrazide-activated silica before the addition of a capping agent (i.e., oxidized glycogen). Characterization of the humic acid support was also carried out by means of TGA, FTIR, SEM, and energy-dispersive X-ray spectroscopy. The binding constants measured by HPAC for the given drugs with entrapped Aldrich humic acid gave good agreement with values reported in the literature under similar pH and temperature conditions for this and other forms of humic acid. Besides providing valuable data on the binding strength of various drugs with humic acid, this work illustrates how HPAC may be used as an analytical tool for screening and characterizing the interactions of drugs and man-made contaminants with humic acid or related binding agents in water and the environment.

Resolving natural organic matter and nanoplastics in binary or ternary systems via UV–Vis analysis

Nanoplastics (NPs) and natural organic matter (NOM) are ubiquitous and usually present simultaneously in the environment. Both NPs and NOM can be adsorbed to minerals such as iron-(hydr)oxides, with such interactions being important for controlling their fate in the environment. However, the quantification of NPs and NOM in mixtures remains challenging even under controlled conditions in laboratory studies. In this research, a UV–Vis method was established to quantify concentrations of NOM, such as humic acid (HA) and fulvic acid (FA), and polystyrene NPs (PSNPs) in mixtures. In addition, both original NOM samples and those recovered following adsorptive fractionation using an iron oxide (goethite, α-FeOOH) were mixed separately with PSNPs and their concentrations were further calculated via the developed UV–Vis method. The UV–Vis method performed well (recovery of 100 ± 16 %) with original NOM and PSNPs system at detection limits of 20.8 and 7.4 mgC L−1, respectively. Particularly, for original FA and PSNPs systems with carboxylic groups (PSNPs-COOH, 200 nm), a similar recovery rate could be obtained at detection limits of only 2.5 and 1.9 mgC L−1, respectively. For fractionated NOM and PSNPs systems, detection limits (31.2 mgC L−1 and 27.5 mgC L−1, respectively) are increased to reach the same accuracy. Furthermore, the UV–Vis method can be used to estimate the proportion of HA that is adsorbed to PSNPs. The relative errors are < 13.7 % when the mass ratios of PSNPs and HA was between 1.6:1 and 8:1 and HA concentration was higher than 4.6 mgC L-1. This method developed can be applied to future laboratory research to investigate the interaction between NOM, NPs, and minerals.

Soil catenas and plant sites on the northern macroslope of Rila Mountain

The following paper represents results from a research focused on the soil associations and their corresponding vegetation communities (soil-plant catenas), located on the northern slopes (N, NW, NE) of the Rila Mountains. Data from eight key sites located between 815 and 2041 m above sea level is discussed. The slope in each site varies from 2&amp;deg; to 25&amp;deg;, and most often the tests and descriptions were carried out on sites with a slope of 10-15&amp;deg;. Vegetation cover is analyzed with plant community plots which provides data on species composition, abundance and coverage. The size of each plot varies from 16 up to 225 m2 depending on the vegetation type. Topsoil horizons were tested in each site in order to diagnose the subspecies diversity of brown forest soils (Cambisols) using ratio of humic acids to fulvic acids. That ratio varies from 0,69 up to 1,61 in all studied sites. Both acids are associated with the dominance of different vegetation types &amp;ndash; deciduous, mixed or coniferous forest or herbaceous canopy. The results are interrupted in terms of the diagnosis and classification of Cambisols and Umbrosols in the area of interest. Differences in soil and vegetation cover of Northwest and Eastern Rila Mountain are highlighted and analyzed.

Intercation Between Some Micro-Elements And Humic Substances in Some Forest Soils Northern Iraq

Four pedons were selected for different soils in the forest cover, two in each of Mankeesh and Atrush areas in Dohuk governorate, under pine and oak trees, in order to study the distribution of the main groups of humic compounds (humic and fulvic acids) and their association with iron and manganese ions. The results showed that the variation in the nature of the forest cover and the speed of decomposition of its remains led to a difference in the distribution of the content of organic matter, the ratios of Humic acid / fulvic acid (FA / HA) and the amount of humic substances produced in each soil, regarding the optical density of the extracted humic compounds, which is expressed as E4/E6, this ratio depends on the chemical composition of these Humic compounds. It is noted from the results that this ratio between E4: E6 ranged between (0.43 - 1.79), low values reflect the presence of aromatic Humic compounds with relatively low molecular weights, while high values indicate the presence of aliphatic humic compounds, the study also showed a difference in the values of iron and manganese associated with humic and fulvic acid as organic complexes, which is consistent with the difference in the degree of decomposition of forest tree residues and plant residues, and in turn is reflected on the quantity and type of humic compounds resulting from the decomposition. The Atrush soil under pine forests excelled in its composition of chelated iron with fulvic acid, Humic acid and manganese chelated with fulvic acid, while the Atrush soil under oak forests excelled in the composition of chelated manganese with humic acid on the rest of the studied soils.

Effects of phosphate-containing additives and zeolite on maturity and heavy metal passivation during pig manure composting

This study investigated the effects of the combination of phosphogypsum with calcium oxide (PPG + CaO), superphosphate with calcium oxide (SSP + CaO) and zeolite (Zeolite) on composting maturity and heavy metal passivation in pig manure composting. The results showed that all treatments reached the maturity requirements and the phosphorus-containing additive treatments had higher final germination indices (GIs). Compared with CK, additive treatments enhanced the compost maturity by promoting volatile fatty acids (VFAs) decomposition (26.4%-30.5%) and formation of stable humus substances. All additive amendment treatments increased humic acid-like substances by over 20%, and the PPG + CaO treatment had the highest level of humus. Composting process reduced the bioavailability of Cu (49.2%), Cd (5.0%), Cr (54.3%), and Pb (26.6%). Correlation analysis found that the heavy mental passivation rate was significantly negatively correlated with the contents of VFAs and nitrogenous substances, and positively correlated with the pH, GI, humic acid content and the ratio of humic acid to fulvic acid (HA/FA). Therefore, the PPG + CaO treatment further increased the passivation rates of Cu (65.6%), Cd (21.7%), and Pb (48.7%) and decreased the mobilization of Zn by promoting maturity and humification during composting.

Microbial-based detonation and processing of vegetable waste for high quality compost production at low temperatures

Composting is a resourceful and harmless technique for reducing vegetable waste (VW), but low temperatures limit the efficiency and quality of composting. Owing to the perishability of the VW and its high indigenous microbial populations, the development of microbial inoculants to enhance its composting is challenging, and thus rarely reported. This study proposed a method for screening and applying compost inoculants to improve the efficiency, safety, and maturity of VW composting at low-temperature. Five cold-adapted (10 °C) strains (Brachybacterium, Klebsiella, Myroides, and Proteus) with glycolytic, starch-hydrolytic, and pectin-degrading functions and four heat-adapted (60 °C) strains (two Parageobacillus and two Bacillus strains) with cellulose-degrading function were screened and inoculated before the initial and thermophilic period of composting, respectively. The inoculants (group T) raised the average temperature of the thermophilic period by more than 2 °C. During the cooling period, the germination index in the T group was 104.7% as compared to 83.3% in the control group. Initially added weed seeds and pathogens were inactivated in both groups, but the rate of inactivation was faster in the T group. The ratio of humic acid to fulvic acid was 2.2 in the T group during the cooling period as compared to 1.4 in the control group, which represented a significant increase (62.0%) in this conversion. During the thermophilic or cooling period of the composting, the inoculants significantly increased the cellulase activity by 74.9%, urease activity by 19.7%, protease activity by 18.6% and catalase activity by 24.4–43.5%. The inoculants not only enhanced enzymatic activities but also restructured and optimized the microbial communities, especially the composition of fungal communities. Moreover, inoculants improved microbial interactions and the contribution of fungi in the composting process. This study provides a theoretical basis and practical knowledge regarding the screening and application of inoculants for performing low-temperature VW composting. Our research could open new avenues of basic and applied research in the science of composting to utilize vegetable wastes for sustainable agriculture and a clean environment.

Response of microbial community diversity and subsoil properties to cow manure amendment in mollisols

ABSTRACT Subsoil fertilization can help agricultural sustainability, but this is not a widely adopted practice. Here, we conducted a pot experiment to study the response of microbial community diversity and topsoil/subsoil properties to cow manure amendment. Our results show that amending subsoil with cow manure (SM) increased available phosphorus (AP) and humic acid (HA) content and the ratio of humic acid to fulvic acid (HA/FA) by 22.2%, 17.7%, and 49.3%, respectively, relative to manure-amended topsoil (TM) (p < 0.05). SM was also more favorable for organic matter degradation and had 61.9%, 21.7%, and 85.3% higher relative abundances of the bacterial phyla Bacteroidetes and Actinobacteria and the order Cytophagales, respectively, relative to the TM treatment (p < 0.05). Compared with that of unamended subsoil (S), the Chao1 index, operational taxonomic units, and Shannon index of fungi were increased but bacterial diversity was decreased by SM treatment (p < 0.05). The only significant difference of the TM-treated soil with the unamended topsoil (T) was a lower bacterial Shannon index (p < 0.05). In conclusion, soil physicochemical properties and subsoil microbial communities were sensitive to cow manure amendment, which has the potential to improve the productivity of subsoils.

The quantity and quality of soil organic matter and humic substances following dry-farming and subsequent restoration in an upland pasture

Soil recovery, particularly soil organic matter (SOM), after land-use changes is crucial for the maintenance of ecosystem functioning and sustainability. The objective of this study was to investigate the influence of wheat dry-farming and subsequent abandonment of dry-farming on the quantity and quality of SOM and humic substances (HS) in a semi-humid upland pasture ecosystem. Soil samples were collected at 0–15 and 15–30 cm depths from cultivated pastures under dry-farming, restored pastures after dry-farming abandonment and never-cultivated pastures as a reference site. The samples were analyzed for total organic C (TOC), chemically labile organic C (LOC) and non-labile C (NLC) fractions; and further fractionated into conventional fulvic acid (FA), humic acid (HA) and humin (HU) components. Land-use changes in pastures altered both labile C and highly recalcitrant C fractions, depending on soil sampling depth. Long-term dry-farming reduced soil TOC (33%), LOC (64%) and NLC (29%) fractions, while dry-farming abandonment resulted in an increase in soil TOC (18–35%), LOC (45–65%) and NLC (17–33%), depending on the age of cultivation abandonment. The quantity of both FA and HU fractions decreased (40–43%) following dry-farming in pasture soils but increased (17–81%) after dry-farming abandonment when compared with cultivated pasture soils. Nevertheless, neither dry-farming nor abandonment of dry-farming affected the HA fraction. Although dry-farming practices increased the HA/FA ratio, (FA + HA)/TOC ratio and E4/E6 ratio of HA, the abandonment of dry-farming reduced these qualitative parameters of soil HS. Dry-farming abandonment in native pastures caused HA structure to be become more aromatic and stable. This study indicated that land-use changes in primary pastures can affect not only the quantity, but also the quality of SOM and its major fractions. Changes in both quantity and quality of SOM and HS could be used as sensitive indicators of soil degradation and ecological restoration in semi-humid pastures.

Spatial variability of the molecular composition of humic acids from subtropical forest soils

Humic acid (HA) plays vital roles in controlling the conservation of soil and water in the forest soils. The structure of HA is closely related to its stability. A clear understanding of the structural difference of HA will facilitate the rational assessment and efficient regulation of forest soils. This study aimed to investigate the structural difference of HA in the forest soils, and the difference in the stability of HA was evaluated according to HA structure. Soils were collected from different elevations and profile depths of Jiugong Mountain (Hubei, China). Soil HA was then extracted and purified. The structure of HA was analyzed by elemental analysis, fluorescence spectroscopy, and solid-state 13C nuclear magnetic resonance (13C NMR). The stability of soil HA was comprehensively accessed by structural complexity, alkyl C/O-alkyl C ratio, and hydrophobicity of HA. The complexity of HA structure was the greatest in soils in middle elevation (1200 m a.s.l.); it tended to decrease with soil depth in all examined soils. Alkyl C (25.1–40.1%) and O-alkyl C (21.2–44.3%) were the main structural fractions in HA samples. The percentage of alkyl C was the greatest in the HA from middle elevation while the O-alkyl C proportion was the highest in the HA from lower elevation (600 m a.s.l.). Alkyl C percentage tended to decrease with soil depth while O-alkyl C showed an opposite trend. The HA aromaticity increased with soil elevation but decreased with soil depth. The hydrophobicity and alkyl C/O-alkyl C ratio of HA was the greatest in middle elevation, and these indexes tended to decrease with soil depth. The HA structure in the subtropical forest soils showed clear spatial variability. The structural features of HA implied that the stability of soil HA was the greatest in the middle elevation and it tended to decrease with soil depth in the examined subtropical forest.

Ratio of elements in humic acids extracted from restored mine soil as a measure of quality of carbon sequestered

Mining land loses large amounts of C (carbon) due to loss of topsoil and mechanical mixing of soil horizons. Biological reclamation of this soil stimulates SOC sequestration. A chronosequence study consisting of 8, 14 and 25years old reclaimed mine soils under Azadirachta indica,Gmelina arborea, Dalbergia sissoo at Gevra, Chhattisgarh, India was initiated to quantify the composition and ratios of humic acid. Carbon content of humic acid was highest in the case of Azadirachta indica followed by Gmelina arborea and Dalbergia sissoo. It had increased from 34.95% to 41.94%, 16.31% to 28.65% and 18.50% to 21.16% for Azadirachta indica, Dalbergia sissoo and Gmelina arborea with increase in year of reclamation for surface soil. Humic acid nitrogen content was found highest in the case of Azadirachta indica followed by Dalbergia sissoo and Gmelina arborea. N (%) in humic acid ranged from 1.29 for Gmelina arborea and 2.65 for Azadirachta indica. Highest C/N ratio was observed in case of Gmelina arborea. The C/N ratios of HA fractions ranged from 30.91 in Gmelina arborea to 15.27 in Azadirachta indica plantations. In case of C/H ratio, it ranged from 6.26 to 15.01 in restored mine soils. Thus, C/H ratio was significantly differing with slightly wider ratios in increasing depths. From elemental composition, it is evident that HAs contained more C than N and H. From the results of experiment we can say that humic acid C and N content improved with increase in year of reclamation due to enrichment in TOC and process of humification.

Composting with biochar or woody peat addition reduces phosphorus bioavailability

Biochar and woody peat have been recognized as an additive to reduce carbon and nitrogen loss during composting. Yet little is known about their influences on the transformation of phosphorus (P) fractions in composting. This study investigated the quantitative and qualitative changes in different P forms during composting with adding biochar or woody peat using sequential extraction and P K-edge X-ray absorption near-edge structure (XANES). The results showed that compost products from the treatment with adding woody peat had a higher HA/FA (the ratio of humic acid to fulvic acid) compared to biochar treatment and the control, suggesting that the addition of woody peat might benefit the humification process of composting. Sequential extraction and XANES illustrated that adding biochar or woody peat limited the P availability. Biochar increased the proportion of Pi and woody peat decreased the conversion from Po to Pi compared to the control. Structural equation modeling and redundancy analysis suggested that biochar improved the refractory P based on the indirect effects of NH4+-N by regulating microbial community, while woody peat was beneficial for Po accumulation by affecting humic acid. Taken together, this research provides basis for regulating the nutrient level of carbon, nitrogen, and phosphorus in composts and reducing environmental risks.

Properties of humus-like substances isolated from organic wastes and their effects on structures of soil humus by Fourier transform infrared spectroscopy

ABSTRACT The structures of soil humus (HS) amended with organic wastes (OWs) were closely related to properties of OWs-derived humus-like substances (HSL). This work evaluated the properties of HSL isolated from mushroom residue (MR), chicken manure (CM), sheep manure (SM), tree leaves (TL), maize straw (MS) and fodder grass (FG) and studied the structures of soil humic acid (HA) and fulvic acid (FA) amended with these OW. FTIR results showed that the relative intensities at 1,640 cm−1 peaks of TL-, FG- and SM-derived HAL were higher than other CM-, MS- and MR-derived HAL (p < 0.05), while the 2,930/1,640 ratios were lower (p < 0.05). Relatively lower E4/E6 ratios and ΔlogK values of TL-, FG- and SM-derived HAL were recorded (p < 0.05). Relative intensities at 1,620 cm−1 peaks of soil HA and soil FA amended with TL, FG and SM were higher than other OWs, while the 2,930/1,620 ratios were significantly lower (p < 0.05). The 2,930/1,620 ratio of soil HA and soil FA amended with MS and CM was the highest, respectively. In conclusion, the properties of OWs-derived HSL play important roles in functional groups of soil HS amended with these OWs.