Fulvic Acid Carbon Research Articles

Modification of soil humic matter after 4 years of compost application

Two soil plots, 1 ha each, were amended yearly for 4 years, respectively, with 35.8 and 71.6 Mg ha −1 yr −1 of mature compost (CM) obtained from food and vegetable residues. The compost, amended soils, and a control soil plot after 4 years (S 4), were analyzed for humin (HUC), humic acid (HAC), fulvic acid (FAC), and non-humic carbon (NHC) content. Compared to S 4, the amended soil contained more humified C (HAC, FAC and HUC) and less NHC. Further evidence of the effect of compost on soil organic matter was obtained by the analysis of the humic acid (HA) fractions isolated from both the compost and the soils. These were characterized by elemental analyses and Diffuse Reflectance Infrared Fourier Transformed spectroscopy. The HAs isolated from CM and from S 4 were significantly different. The HAs isolated from the amended plots were more similar to HA isolated from CM than to HA isolated from S 4. The experimental data of this work indicate that the compost application may affect significantly the soil organic matter composition, and that the approach used in this work allows one to trace the fate of compost organic matter in soil.

Long-term fertilization effects on soil organic matter quality and dynamics under different production systems in semiarid Pampean soils

Soil quality can be determined by monitoring, over time, specific chemical, physical or biological properties. Agronomists have long recognized the benefits of maintaining and increasing soil organic carbon (SOC), as well as its labile or particulate (POC) and humic acid (HA) fractions. This research was aimed at the evaluation of continuous wheat (WW) and wheat-grazing (WG), non-fertilized (nf) and annually fertilized with N + P (f), effects on the quantity, quality and dynamics of the organic fractions. The soil (0–0.15 m) was sampled during 1991, 1992, 1993, 1994, 1995 and 1997. Fertilizer application increased labile organic fraction contents compared with the recalcitrant ones. Fertilization increased POC from 0.11 to 0.19% in WW and from 0.15 to 0.20% in WG, while fulvic acid carbon was increased from 0.083 to 0.167% and from 0.101 to 0.140% in WW and WG, respectively. The humified fraction quantity and quality were modified by fertilization. Quantity differences depended on production system, mainly, animal grazing activity. Changes in HA quality were related to higher labile OC content. The HA extracted from fertilized soils showed higher aliphatic and phenolic OH groups contents than unfertilized ones, associated to high labile organic fractions contents. The POC dynamics suggested a strong dependence to annual precipitation, mainly water availability during the fallow period. These results confirm the important effect of the long-term fertilization on POC content and HA quality. They could be utilized as soil quality indicators, however, soil physical and climatic conditions must be considered.

Thermal analysis for the evaluation of the organic matter evolution during municipal solid waste aerobic composting process

A study aimed to monitor the composting process and to evaluate the effectiveness of indicators able to define the stability of a compost obtained by mixing municipal solid waste (MSW) and vegetal waste, was conducted. For this reason, composting process lasting 3 months, was monitored by chemical and thermal analysis. Total organic carbon (TOC), total extractable carbon (TEC) and humic and fulvic acid carbon (HA and FA, respectively) were determined after extraction, fractionation and analysis of organic matter from samples collected during the composting process. Differential scanning calorimetry (DSC), thermogravimetry (TG) and the first derivative of the TG (DTG) were simultaneously performed in oxidizing conditions on grounded compost samples and HA extracted. Thermoanalitical data resulted to be useful in integrating quantitative information coming from chemical analysis of humified fraction of compost organic matter. Particularly DSC curves allowed to distinguish between well and poor stabilized organic matter, and information deriving from weight losses, registered by the TG and DTG curves, enable to individuate the evolution state of the organic matter and therefore its stability.

PHOSPHORUS CONTENT IN SOIL IN RELATION TO FULVIC ACID CARBON FRACTION

The fulvic acid fraction is considered an important constituent of soil organic matter and is sensitive to management regimes and tillage impact. Both humic acids (HA) and fulvic acids (FA) are able to form metal complexes which bind appreciable amounts of phosphate or phosphorus (P) species. The aim of the present study is to evaluate the fulvic acid carbon content of agricultural soils in Argentina and to explore the possible relationship between acid carbon (FC) content and the level of available P in the soil. A total of 74 surface samples of Hapludolls and Haplustolls covering areas with decreasing levels of annual rainfall were analyzed. It was found that soils with FC content >5.5 g kg−1 exhibited available P levels >30 mg kg−1, whereas available P levels <20 mg kg−1 were related to FC contents <4.0 g kg−1. Soils with high FC content thus currently have adequate P without supplementing it in the form of fertilizer. A more meaningful relationship is found between the FC fraction and available P than between P status and total organic carbon of soil.

Alterações na matéria orgânica e na biomassa microbiana em solo de mata natural submetido a diferentes manejos

Avaliou-se, em um Latossolo Roxo, o efeito de diferentes formas de manejo do solo sobre a matéria orgânica do solo e na biomassa microbiana. Os tratamentos usados foram: mata natural; mata natural até 1976 e café até 1994 (amostragem na projeção da copa e na entrelinha); mata natural até 1976, café até 1991 e milho até 1994; mata natural até 1940, café até 1960, citros até 1978, e cana-de-açúcar até 1994 (amostragem na linha e na entrelinha). A mata natural apresentou os maiores valores de C orgânico no solo e na fração humina e os menores valores foram obtidos nas áreas com cana-de-açúcar, que apresentaram os maiores valores de C microbiano em relação à mata natural. O uso agrícola do solo aumentou a porcentagem de C orgânico na forma de ácidos húmicos e fúlvicos, em relação à mata natural. Em geral, o solo apresentou mais de 74% do C orgânico na forma de húmus residual.

Organic carbon quantity and forms as influenced by tillage and cropping sequence1

Soil organic matter and its chemical fractions have a profound impact on soil chemical and physical properties. In turn, the effect of management (cropping and tillage) on the quantity and chemical properties of soil organic matter can be substantial. The objective of this study was to compare the effects of specific tillage regimes and crop sequences commonly used in the central Great Plains of the United States on the quantity, quality, and distribution with depth of soil organic carbon (SOC). Soils were sampled in 1 cm or 2 cm increments to a depth of 10 cm from experimental field plots on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). The plots had been under 6 continuous tillage regimes since 1978 and cropped to continuous corn, continuous soybean, or corn‐soybean in rotation since 1985. Soils were analyzed for total SOC, fulvic acid (FA) carbon, and humic acid (HA) carbon. No‐till and continuous corn (Zea mays L.) management generally had the highest SOC, with a sharp reduction in SOC below 2 cm. Only no‐till increased FA, which also decreased with depth, especially between 2 and 4 cm. Humic acid concentration was highest under continuous corn but was unaffected by tillage. Humic acid also was highest in the 1‐ to 2‐cm increment of continuous corn. Two ratios which are used as indices of degree of humification, HA/FA and (HA+FA)/SOC, gave different estimates of the effect of management. Only continuous com increased HA/FA, suggesting increased humification. No treatment affected (HA+FA)/SOC. Overall, continuous corn and no‐till contributed the greatest amounts of residue and maintained a soil environment conducive to preserving the resulting organic matter. These management options increase not only total SOC, but also alter the quality of that SOC as measured by HA and FA. These changes in SOC characteristics may have implications for long‐term soil quality and soil productivity.

Relationships between water-soluble carbohydrate and phenol fractions and the humification indices of different organic wastes during composting

The present work dealt with the relationships between the degradation and humification processes which the organic matter underwent during the composting of six different organic-waste mixtures. Four of them were prepared by the Rutgers forced-ventilation composting system and the other two by the mobile (turn over) pile system. The main components were: sewage sludge, sorghum bagasse and municipal solid waste. Different degradation rates were observed for the three main components (cellulose, hemicellulose and lignin) of the organic matter during composting. In the case of the first two components, the degree of degradation ranged from 70 to 85% during the whole process, depending on the starting mixture, whereas only 30–50% of the initial concentration of lignin was degraded in the mixtures prepared with municipal solid wastes (MSW) and lignocellulosic materials. Water-soluble carbohydrate and phenol degradation were studied because they have been proposed as precursors of the humification processes. In the experiment described, they had different degradation rates during composting depending on the starting mixture and the composting system used. The water-soluble carbohydrate was the most intensely degraded fraction in the piles prepared with urban refuse although no appreciable degradation was measured in the other three mixtures, whereas there was an appreciable reduction in the water-soluble phenol fraction of all six mixtures during composting, values of less than 0.1% being reached in the mature composts. Humification processes were studied by quantification of the extractable humic-like substances and the generally accepted humification indices: extractable carbon to total organic carbon (EXC/TOC), humic acid carbon to total organic carbon (HAC/TOC), humic acid carbon to extractable carbon (HAC/EXC) and the humic acid carbon to fulvic acid carbon (HAC/FAC) and by determining the cation exchange capacity of the mixture during composting. All the indices increased during composting and followed a similar trend. The humic-like acid fraction was mainly responsible for these changes, showing that the composting involves a process of humification. The cation exchange capacity to total organic carbon ratio showed itself to be a useful humification index during composting since this index clearly increased more than the others. Correlations between some of the above humification indices and the concentrations of water-soluble and less polymerised carbohydrates and phenols indicates the possible influence of these fractions on the humification processes. Significant correlations were found between the phenols and the HAC/TOC and the HAC/EXC ratios, whereas no significant correlations were recorded with the carbohydrate fraction.

FULVIC ACID CARBON AS A DIAGNOSTIC FEATURE FOR AGRICULTURAL SOIL EVALUATION

The fulvic acid fraction is considered to be sensitive to agronomic and environmental factors. Therefore, the objectives of this study were to evaluate total carbon (TC) and fulvic acid carbon (FC) contents and to establish a possible relationship between the FC fraction and coarse organic matter in agricultural soils under different management practices: (i) conventional tilled soils (CVTs), (ii) conservation tilled soils (CSTs), and (iii) virgin soils (VIRs) from a wide region in Argentina. The investigation included 114 surface samples of Hapludolls, Haplustolls, and Entisols ranging in texture from sand to silt loam. In 29 selected samples, two separate soil mineral fractions were used ( CSTs > VIRs), and this ratio also increased from finer textured soils to coarser textured soils. Results from soil mineral fractions indicated that FC content was highly related to recently incorporated organic residues.

Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments

A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N 2O) production rates in laboratory incubations of riverbed sediments to evaluate the effect of varying nitrate concentrations, organic carbon concentrations and type, and water temperature on potential denitrification rates. Sediment incubations amended with nitrate, at concentrations ranging from 357 to 2142 μmol l −1 (as measured in the field), produced no significant increase ( P > 0.05) in N 2O production rates, indicating that the denitrification potential in these sediments was not nitrate limited. In contrast, incubations amended with acetate as a source of organic carbon, at concentrations ranging from 0 to 624 μmol l −1, produced significant increases ( P < 0.05) in N 2O production rates with increased organic carbon concentration, indicating that the denitrification potential in these sediments was organic carbon limited. Furthermore, N 2O production rates also were affected by the type of organic carbon available as an electron donor. Acetate and surface-water-derived fulvic acid supported higher N 2O production rates than groundwater-derived fulvic acid or sedimentary organic carbon. Lowering incubation temperatures from 22 to 4°C resulted in about a 77% decrease in the N 2O production rates. These results help to explain findings from previous studies indicating that only 15–30% of nitrate in groundwater was denitrified before discharging to the South Platte River and that nitrate concentrations in the river generally were higher in winter than in summer.

Copper Speciation and Binding by Organic Matter in Copper-Contaminated Streamwater

Fulvic acid binding sites (1.3−70 μM) and EDTA (0.0017−0.18 μM) accounted for organically bound Cu in seven stream samples measured by potentiometric titration. Cu was 84−99% organically bound in filtrates with 200 nM total Cu. Binding of Cu by EDTA was limited by competition from other trace metals. Water hardness was inversely related to properties of dissolved organic carbon (DOC) that enhance fulvic acid binding: DOC concentration, percentage of DOC that is fulvic acid, and binding sites per fulvic acid carbon. Dissolved trace metals, stabilized by organic binding, occurred at increased concentration in soft water as compared to hard water.

Prolonged humification of 14C-labelled oat residues in extensively fertilized soils

The turnover of 14C-labelled oat shoots and roots was studied for 1500 days in loamy sand and clay loam under optimal temperature and moisture conditions. Four fertilizer rates were tested: unfertilized control, single dose of NPK, triple dose of NPK, and triple NPK plus CaCO 3. The most extensive decay of the organic matter occurred during the first 100 days of decomposition. Increasing NPK. contents stimulated the accumulation of radioactive carbon in bitumens and fulvic acids. Addition of calcium enhanced the amounts of 14C in humic acids. Mineral fertilization also caused changes in the composition of humic acids and in their physico-chemical properties. Increasing NPK application rates enhanced small molecular fractions of humic acids in both soils: addition of calcium reduced the amount of high molecular fractions in sandy soils and increased in the clay soil.

Sources and characteristics of fulvic and humic acids from a salt marsh estuary

Fulvic and humic acids were isolated from living and dead Spartina alterniflora and the marsh sediments of a Georgia salt marsh estuary. Elemental composition, 13C-NMR, FTIR, carbohydrate and amino acid analyses were performed on these compounds and indicate that these fulvic acids and humic acids are very similar regardless of source material. Furthermore, both groups of compounds generally resemble marine humic matter, although specific differences can be identified. Calculations indicate that 28.6% of the fulvic acid carbon and 14.8% of the humic acid carbon can be accounted for as sugars and amino acids.

LIMITATIONS OF ALKALI-EXTRACTABLE ORGANIC FRACTIONS AS BASES OF SOIL CLASSIFICATION CRITERIA

Soil samples, mainly from eastern and northern Canada, were extracted with sodium hydroxide-pyrophosphate and the centrifuged extracts were fractionated into humic acid, fulvic acid and the polyphenolic component of the fulvic acid fraction. Details of the extraction and fractionation procedure were altered systematically and the effects of these changes on amounts of carbon in the various fractions were studied. A tenfold increase in the ratio of soil to extracting solution resulted in a marked increase (nearly double in some cases) in the ratio of humic acid carbon to fulvic acid carbon (Ch/Cf). Increasing the centrifugal force from 1150 × g to 8200 × g had little effect on Ch, but decreased Cf values. Dissolving and reprecipitating humic acid resulted usually in a decrease in Ch/Cf. Different shaking speeds and times, and extraction under nitrogen rather than air had minor, if any, effects on the Ch/Cf ratios. Most of the podzolic B horizons tested could be distinguished from the other 60 horizons by the combination of C ext (extractable carbon), Ch/Cf and Ca/Cf (carbon content of the polyphenols component of the fulvic acid fraction/fulvic acid carbon).Extractable organic fractions have some promise as bases of soil classification criteria but their potential is limited at present. The procedures are time-consuming and exacting, and results are not comparable between laboratories. Rigorous standardization of methods and interlaboratory comparisons of data might lead to more useful criteria based on organic matter composition. Key words: Humic acid carbon, fulvic acid carbon, polyphenols carbon, extractable carbon, classification criteria

Eolian particulates from oceanic and rural areas—their lipids fulvic and humic acids and residual carbon

The lipids of eolian particulates from oceanic areas (primarily the Atlantic) consist of predominantly terrestrial higher plant waxes and microbial lipid residues of mainly a lacustrine origin. Their solvent-insoluble organic matter has been separated into fulvic acid, humic acid and residual carbon fractions. The humic acids exhibit properties typical of terrestrial soil humates. The residual carbon consists primarily of amorphous carbon (soot). The lipids of rural particulate samples consist primarily of higher plant wax (based on the distributions of the n-alkanes, n-fatty acids and n-alcohols), with lesser amounts of higher plant terpenes and of microbial lipid residues from various sources. Some minor anthropogenic pollutants are also present. These samples were collected during summer and winter in the western United States. These data indicate that primary biogenic residues (i.e. plant waxes and terpenes, etc.) are major components of eolian particulates in the troposphere away from urban areas. This natural background of eolian organic matter is a significant component in the global cycling and flux of carbon.

Studies on the properties of organic matter in buried humic horizon derived from volcanic ash

Abstract In surface horizons (4 samples) and buried humic horizons (14 samples) derived from volcanic ash, the contents of total, fulvic acid. humic acid and humin carbon and nitrogen were determined. The C/N ratios and the percentage of carbon and nitrogen of each fraction in total carbon and nitrogen were calculated. These values varied with each soil profile and horizon. In the surface horizons and the buried humic horizons with age younger than 3,000 yrs. B.P., C/N ratios of soil samples, fulvic acid, and humic acid were low, and those of humin were distributed over a wide range. The C/N ratios increased in the order of fulvic acid, humic acid, humin among these soil samples. Among soil samples which have been buried from 3,000 to 28,000 yrs. B.P., the more were the total carbon contents of soil and also the fulvic acid, humic acid and humin carbon contents, the greater was the tendency of the C/N ratios to rise. The C/N ratios increased in the order of fulvic acid, humin, humic acid among these soil ...