Compost Organic Matter Research Articles

Properties of Organic Matter in Composts Based on Sewage Sludge

Properties of Organic Matter in Composts Based on Sewage Sludge

Analytical pyrolysis (Py-GC-MS) for the assessment of olive mill pomace composting efficiency and the effects of compost thermal treatment

Composting is an interesting solution for recycling the large amount of residues typically generated in olive oil production areas, particularly olive mill pomace. Bulking agents must be added to wet olive mill pomace for composting. The diversity of the materials used (such as olive tree-pruning residues, animal manure, or straw) and the variable proportion, in which they are mixed, are responsible for the heterogeneity and variability of the quality of the produced compost. For this reason, a comprehensive characterization of compost organic matter is necessary to gain information about its stability and maturity useful as well as to predict its behavior as a soil amendment. In this work, fresh olive mill pomace and four composted olive mill pomace samples were characterized using analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS). Results showed a large variety of pyrolysis products, many of which had a specific biochemical origin. Pyrolysis-GC-MS revealed a decrease in fatty acids and aliphatic compounds content with composting, along with carbohydrates degradation and an increase in phenolic and N-compounds levels. Furthermore, the differences observed in organic matter characteristics had an impact on agronomic aspects (water repellency and phytotoxicity). Thus, the occurrence of fatty acids in incompletely composted materials (mainly palmitic and cis-vaccenic acids) was associated with increased phytotoxicity and higher water repellency. The presence of chicken manure in the mixtures was proved to favor the humification process and the production of stabilized compost (characterized by a lower Aliphatic-C/Aromatic-C ratio and higher N-heterocycles content). Furthermore, in this work, the effectiveness of applying thermal treatments to improve compost quality has been evaluated. Analysis of the Py-GC-MS results by means of principal component analysis (PCA) revealed thermal rearrangement, predominantly aromatization, and loss of functional groups of carbohydrates, lignin, and proteins, at temperatures above 225 ºC. Interestingly, the results suggest that materials with a non-effective or incomplete composting process can be transformed by thermal treatment into more stable products, exhibiting similar agronomic characteristics as those have that undergone a more efficient biotransformation.

Electric field applications enhance the electron transfer capacity of dissolved organic matter in sludge compost

ABSTRACT Dissolved organic matter (DOM) plays an important role in heavy metal passivation and organic pollutant degradation owing to its redox ability. The structure and composition of DOM are determinants of redox ability changes during composting. Electric field-assisted aerobic composting (EAAC) has been shown to promote the degradation and humification of organic matter in compost. However, how EAAC affects the redox ability of DOM remains unclear. Hence, electron transfer capacity (ETC) of DOM extracted from EAAC was studied using the electrochemical method. Various spectral methods, such as excitation–emission matrix and ultraviolet and visible spectrophotometry were used to study the relationship of ETC with the compositional and structural changes of DOM. Results indicated that EAAC enhanced ETC of DOM at the later stage of composting, and ETC of DOM extracted from the final EAAC product was 10.4% higher than that of the control group. Spectral and correlation analyses showed that EAAC resulted in structural and compositional changes of DOM, and humification degree, aromatic compounds, molecular weight, and fulvic- and humic-like substance contents were improved in EAAC. This conversion increased ETC of DOM. Results of this study will contribute to the understanding of the redox of DOM and in expanding the application of EAAC products.

Extraction and Identification of a Wide Range of Microplastic Polymers in Soil and Compost.

Microplastic pollution is globally widespread; however, the presence of microplastics in soil systems is poorly understood, due to the complexity of soils and a lack of standardised extraction methods. Two commonly used extraction methods were optimised and compared for the extraction of low-density (polyethylene (PE)) and high-density microplastics (polyethylene (PET)), olive-oil-based extraction, and density separation with zinc chloride (ZnCl2). Comparable recoveries in a low-organic-matter matrix (soil; most >98%) were observed, but in a high-organic-matter matrix (compost), density separation yielded higher recoveries (98 ± 4% vs. 80 ± 11%). Density separation was further tested for the extraction of five microplastic polymers spiked at different concentrations. Recoveries were >93% for both soil and compost, with no differences between matrices and individual polymers. Reduction in levels of organic matter in compost was tested before and after extraction, as well as combined. Double oxidation (Fenton’s reagent and 1 M NaOH) exhibited the highest reduction in organic matter. Extracted microplastic polymers were further identified via headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME–GC–MS). This method has shown the potential for descriptive quantification of microplastic polymers. A linear relationship between the number of particles and the signal response was demonstrated for PET, polystyrene (PS), polyvinyl chloride (PVC), and PE (R2 > 0.98 in alluvial soil, and R2 > 0.80 in compost). The extraction and identification methods were demonstrated on an environmental sample of municipal biowaste compost, with the recovery of 36 ± 9 microplastic particles per 10 g of compost, and the detection of PS and PP.

Changes in the Spectral Characteristics of Hydrophilic Fraction in Compost Organic Matter

The hydrophilic fraction (HyI) is one of the important components of humus, and its structure and composition are important factors for evaluating the stability and maturity of compost. This study used spectroscopy to analyze the composition and structure of HyI. The results showed that with the passage of composting time, the UV–Vis curve had a red shift, indicating that the conjugated structure of the substance increased and the aromaticity is enhanced. The three-dimensional fluorescence excitation–emission spectrum (3D-EEM) showed that the fluorescence intensity of humus-like substances in HYI was significantly enhanced, and microbial metabolites such as protein-like substances, carbohydrates and other small molecules were continuously degraded, and the relative content decreased from 21% to 8%, the humus-like substances rose from 54% to 68%, which showed that the organic matter in the compost is continuously condensing and polymerizing, and the maturity and stability of the compost product are deepened.

Assessment of the Content of Dry Matter and Dry Organic Matter in Compost with Neural Modelling Methods

Neural image analysis is commonly used to solve scientific problems of biosystems and mechanical engineering. The method has been applied, for example, to assess the quality of foodstuffs such as fruit and vegetables, cereal grains, and meat. The method can also be used to analyse composting processes. The scientific problem lets us formulate the research hypothesis: it is possible to identify representative traits of the image of composted material that are necessary to create a neural model supporting the process of assessment of the content of dry matter and dry organic matter in composted material. The effect of the research is the identification of selected features of the composted material and the methods of neural image analysis resulted in a new original method enabling effective assessment of the content of dry matter and dry organic matter. The content of dry matter and dry organic matter can be analysed by means of parameters specifying the colour of compost. The best developed neural models for the assessment of the content of dry matter and dry organic matter in compost are: in visible light RBF 19:19-2-1:1 (test error 0.0922) and MLP 14:14-14-11-1:1 (test error 0.1722), in mixed light RBF 30:30-8-1:1 (test error 0.0764) and MLP 7:7-9-7-1:1 (test error 0.1795). The neural models generated for the compost images taken in mixed light had better qualitative characteristics.

Bulk and water-extractable organic matter from compost: evaluation of the selective dissolution in water using infrared absorbance ratios

Land application of composts affects concentration and composition of dissolved organic matter (OM) which plays important roles in soil functioning and may have effects on spreading of environmental pollution. Linking between the composition of bulk compost OM and its water-soluble fraction may, therefore, allow better understanding and prediction of the environmental impact of compost added to soil. The objectives of this study were to (i) examine composition-based links between bulk compost OM and water-extractable OM (WEOM), and (ii) evaluate and quantify selectivity of bulk compost OM dissolution, based on infrared (IR) absorbing functional groups. For that, 8 different composts and their freeze-dried WEOMs were characterized by mid-IR transmission spectroscopy. Compositions of compost OM and of WEOM were characterized in terms of ratios (R) defined on the basis of both areas and heights of specific IR absorbance bands in relation to absorbance by aliphatic CH groups. A simple novel approach is suggested, whereby selective dissolution of compost OM components is quantified by relating the R values determined for WEOM to those associated with compost OM. Significant similarities of IR spectra found in a series of WEOMs (and, to a lesser extent, in a series of compost OMs) suggest significant contributions of OM carboxylic groups to various bands. IR absorbance of compost OM contributed by hydrophilic and, specifically, carboxyl and carboxylate groups, when related to absorbance by aliphatic CH groups, can be used for predicting the indices characterizing WEOM composition, such as IR absorbance-based R values and aromaticity estimated from specific UV absorbance.

PENGGUNAAN KOMPOS BAGASE UNTUK MENGOPTIMALKAN PRODUKSI TANAMAN TERUNG (Solanum melongena L.)

Eggplant (Solanum melongena L.) is a plant species that is known as the fruit and vegetables grown for use as a food ingredient. These plants belong to one group of plants that produce seeds Eggplant Trunk divided into two kinds, namely the main stem and branching. Eggplant leaf consists of a petiole and the leaf blade. Eggplant flowers are hermaphrodite flowers, or better known as the bisexual flowers, the flowers are one of the stamen to the pistil. Eggplant fruit is the fruit of a true single.. Cultivation of eggplant in the Project of Independent Business is using composting technology bagase. Bagase compost is compost that comes from bagasse or the rest of the sugar mill. Bagase own compost organic matter content of about 90%, N content of 0,3%, 0,02% P2O5, K20 0,14%, Ca 0,06% and 0,04% Mg. The project goal independent business is the use of compost bagase on the cultivation of eggplant to reduce the use of chemical fertilizers and optimize plant production eggplant, farming systems semi-organic environmentally sustainable and analyze the feasibility of cultivation of eggplant with market potential in Payakumbuh and the District Fifty City. Independent business projects implemented during the four months from September to December 2015 and conducted experiments dikebun State Agricultural Polytechnic Payakumbuh with total area of ​​300 m2. Eggplant crop production on the independent business projects with the use of compost bagase treatment that is 575 Kg/300 m2, a profit of Rp. 835.310, the profitability of 92% and RC Ratio of 1,92.

Physiological Conditions of Decomposition Process and Quality of Compost Based on Beef Cattle Feces Enriched with Azolla sp.

The research was aimed to determine the effect of the addition of Azolla sp. on physiological conditions, the kinetics of temperature, and the quality of compost which includes carbon content, and compost organic matter. The method used was experimental with A Completely Randomized Design (CRD). There were three treatments that were the addition of Azolla sp. 0% (P0), 10% (P1), and 20% (P2). Each treatment was repeated 6 times, so that the number of experimental unit was 18 mounds of compost. Variables measured were temperature kinetics, levels of organic carbon and compost organic matter. Observations of temperature were carried out on days 0, 4, 8, 12, 16, 20, 24 and 28 at 01.30 – 02.30 pm. The carbon content and compost organic matter of the final compost product were analyzed in the laboratory. Data on the kinetics of temperature were analyzed using Repeated Measure Analysis of variance (RMA), while those of the levels of organic carbon and organic matter compost were analyzed using Analysis of variance (ANOVA). The results of the variance analysis showed a significant interaction (P < 0.05) between the treatment and the days of observation on the kinetics of temperature. The highest temperature kinetics observed for P2 and P1 were achieved on day 4 (54.00˚C and 50.50˚C, respectively), while the highest temperature for P0 was achieved on day 8 (50.33˚C). The temperature of P0, P1 and P2 ranged 27.17-50.33˚C; 28.17-50.50˚C and 30.00-54.00˚C, respectively. Least Significance Different (LSD) results showed significant variations in temperature kinetics. Enrichment of compost with Azolla sp had no significant effect (P > 0.05) on the levels of organic carbon and compost organic matter.

Spectral characteristics of soil dissolved organic matter: Long-term effects of exogenous organic matter on soil organic matter and spatial-temporal changes

The aim of this study was to evaluate the long-term effect of urban and green waste compost exogenous organic matter (EOM) on soil dissolved organic matter (DOM). A luvic cambisol was amended 7 years before the study. DOM was investigated along a soil profile down to 1 m depth regarding seasonal variations (autumn and spring). DOM sampled by suction cups was characterized using dissolved organic carbon (DOC) content and excitation emission matrix (EEM) fluorescence. The variability of DOM concentrations was pronounced but no major change in composition was determined. The results obtained, reinforced by statistical analysis, showed that the DOM quality was mainly influenced by soil management (organic matter amendment) whereas the quantity mainly depended on the season (heavy precipitation event). DOM humic characteristics were strongly dependent on amendment and changed with depth but was not affected by the season. Long term effect of compost organic matter was highlighted after a 7-years amendment.

PEMANFAATAN KOMPOS TANDAN KOSONG KELAPA SAWIT DENGAN BAKTERI SELULOLITIK DAN LIGOLITIK SERTA NPK TERHADAP PERTUMBUHAN BIBIT KAKAO (Theobroma cacao L.)

ABSTRACT Cocoa ( Theobroma cacao L.) is one of the large plantations after oil palm. The increase in cocoa nursery can be accompanied by the utilization of waste derived from palm oil, namely oil palm empty fruit bunches (OPEFB). oil palm empty fruit bunches can be useful as organic fertilizer because it can improve soil physical, chemical and biological properties. The use of OPEFB as organic fertilizer will also reduce excessive use of NPK. Utilization of OPEFB into organic fertilizer can be in the form of compost or raw OPEFB organic matter plus cellulolytic and lignolytic microbes. This study aims to determine the effect of NPK fertilizer and OPEFB compost on the growth of cocoa seedlings. This research was conducted experimentally using a completely randomized design consisting of nine treatments and three replications. Parameters of observation were plant height, stem diameter, number of leaves, root canopy ratio, dry weight of seedlings and age of planting. The results showed that the provision of 100 g polybag -1 OPEFB compost plus 50% NPK fertilizer (2 g polybag -1 ) could provide good growth in cocoa seeds ( Theobroma cacao L.).

Utilization of Trichoderma viride as organic fertilizer to induce the resistance of banana seeds on Fusarium oxysporum f.sp cubense (FOC)

Utilization of Trichoderma viride as Organic Fertilizer to Induce the Resistance of Banana Seeds to Fusarium oxysporum f.sp cubense (Foc). This study aimed to find out the type of organic material that is able to suppress Foc. and knowing the macronutrient value of organic matter decomposed by Trichoderma viride. This research was carried out on the field of the Faculty of Agriculture, Graha Nusantara Padangsidimpuan University, from February to August 2018. The treatment of research are control, Cow manure without decomposition by T. viride, Cow manure was decomposed by T. viride, Chicken manure without decomposition by T. viride, and Chicken manure was decomposed by T. viride. The results showed that compost with the addition of decomposer Trichoderma viride can suppress Foc growth and can increase the nutrient value of N, P, K compost organic matter.

Effects of Compost and Manure Application Rate on the Soil Physico-Chemical Layers Properties and Plant Productivity

The effects of manure and compost application rates on organic carbon (OC) and total nitrogen (TN) contents and their distribution in soil layers as well as basil growth on the amended soils were investigated. Five plots were experimented where the amended substrate was used at a rate of 10% manure, and 10%, 20% and 40% compost, compared to unamended control soil. After 3 months, the soil OC content showed a high mineralization with the compost compared to the manure used at 10%, reflecting a higher biodegradable compost organic matter (OM) fraction that contributed to soil microorganisms activity increase. As a result, a difference in vertical OC distribution in the soil layers was observed. Moreover, the compost rate increase improved the soil cation exchange capacity and the soil base saturation percentage by 41%, 56% and 76%, and by 46%, 77% and 140%, respectively. This improvement indicated the importance of the aggregate established at the 20% and 40% compost rates compared to the 10% compost rate treatment. Basil yields were the highest at low compost rate (10%) treatment. This short term study highlighted the benefits of the compost use and its potential effects on the soil structure and the basil plant productivity improvements while using low amendment rate, exhibiting the high stability of the soil aggregates newly established.

Effect of biochar amendment on compost organic matter composition following aerobic composting of manure

Biochar, a material defined as charred organic matter applied in agriculture, is suggested as a beneficial additive and bulking agent in composting. Biochar addition to the composting feedstock was shown to reduce greenhouse gas emissions and nutrient leaching during the composting process, and to result in a fertilizer and plant growth medium that is superior to non-amended composts. However, the impact of biochar on the quality and carbon speciation of the organic matter in bulk compost has so far not been the focus of systematic analyses, although these parameters are key to determine the long-term stability and carbon sequestration potential of biochar-amended composts in soil. In this study, we used different spectroscopic techniques to compare the organic carbon speciation of manure compost amended with three different biochars. A non-biochar-amended compost served as control. Based on Fourier-transformed infrared (FTIR) and 13C nuclear magnetic resonance (NMR) spectroscopy we did not observe any differences in carbon speciation of the bulk compost independent of biochar type, despite a change in the FTIR absorbance ratio 2925cm−1/1034cm−1, that is suggested as an indicator for compost maturity. Specific UV absorbance (SUVA) and emission-excitation matrixes (EEM) revealed minor differences in the extractable carbon fractions, which only accounted for ~2–3% of total organic carbon. Increased total organic carbon content of biochar-amended composts was only due to the addition of biochar-C and not enhanced preservation of compost feedstock-C. Our results suggest that biochars do not alter the carbon speciation in compost organic matter under conditions optimized for aerobic decomposition of compost feedstock. Considering the effects of biochar on compost nutrient retention, mitigation of greenhouse gas emissions and carbon sequestration, biochar addition during aerobic composting of manure might be an attractive strategy to produce a sustainable, slow release fertilizer.

Microbial Diversity and Bioactive Substances in Disease Suppressive Composts from India

ABSTRACTThe present study aimed to investigate microbial communities in seven Indian composts and their potential for biocontrol of Fusarium oxysporum f. sp. lycopersici. In addition, identification of bioactive substances in disease suppressive composts was also attempted. Composts were chosen based on disease suppressiveness and subjected to molecular microbial analyses. Total genomic DNA from the composts was extracted and amplified with polymerase chain reaction using primers targeting the 18S rRNA and 16S rRNA genes of fungi and bacteria, respectively. Denaturing gradient gel electrophoresis (DGGE) fingerprinting and DNA sequencing were used to identify the fungal and bacterial targets. Phylogenetic analysis of the fungal 18S rRNA ITS gene sequences showed that phylum Ascomycota was dominant in all composts, while in the bacterial 16S rRNA gene sequences, the phylum Proteobacteria was dominant. Some fungi in disease suppressive composts grouped phylogenetically close to F. oxysporum. Bacterial sequences with close similarity (>95% identity) with Actinobacterium showed a strong presence only in disease suppressive composts. Disease suppressive composts formed a separate group in the cluster analysis of 18S rRNA ITS and 16S rRNA gene sequences. Gas chromatography-time of flight-mass spectrometry was performed with compost extracts to determine if bioactive substances were present in disease suppressive composts. The analysis of compost organic matter showed a negative association of disease suppressiveness with phloroglucinol, sitosterol, and monoenoic fatty acid, while cholesterol and certain organic acids were positively associated with suppressiveness.

The change of organic matter in sewage sludge composting and its influence on the adsorption of pentachlorophenol (PCP).

Due to the abundance of organic matter in compost, the addition of compost to soil can promote the adsorption of pesticides. However, few studies have examined the influence of the composting duration on the organic matter (OM) transformation and adsorption capacity of the compost. In this study, a mixture of sewage sludge and straw was composted, and then the physicochemical properties of various OM were studied. Additionally, the sorption capacities of humic acid (HA), humin (HM), humic acid + humin, and fulvic acid (FA) + humic acid + humin extracted from composts of different stages toward pentachlorophenol (PCP) were compared. The sorption data can be well-described by the Freundlich model, and the sorption capacity of PCP on HM is the strongest of all organic components. After 120 days of composting, the sorption abilities of HA and HM increased by 54.76 and 36.73%, respectively, which corresponds with increases in the aromatization degree, BET specific area, and pore volume and with a decrease in acid functional groups. The sorption ability of HA and HM increased by 54.76 and 36.73% due to the increase of the aromatization degree. However, the sorption capacity of the compost decreased by 51.2%, which resulted from a decrease in total organic matter content and from the interaction between organic components in composts. This could be verified by the sequence of the sorption capacity: HM > HM + HA > HM + HA + FA > HA. The contribution of humus to the sorption of PCP onto compost is approximately 41 to 55%, and it increases with composting time. Therefore, it is possible that other components are present that affect the adsorption of PCP on composts.

Study of the Effects of Compost and Nitrogen on Concentrations of Nutrients in Citrange Seedlings

A one-year factorial experiment using the randomized complete block design with three replications was carried out to study the effects of compost and nitrogen on the concentrations of nutrients in citrange seedlings. The treatments included various levels of the organic matter compost (zero, 2.5, 5, and 7.5%) and different levels of pure nitrogen from ammonium sulfate (zero, 20, 40, and 80 mg/kg soil). In all, 48 treatments were applied on citrange stocks. Comparison of mean squares for the effects of compost and nitrogen fertilizer on micronutrients showed that these effects were significant on potassium and manganese at the five percent probability level (and on iron, zinc, and copper at the one percent probability level), but were not significant on elements such as nitrogen, phosphorous, or magnesium, in citrange rootstocks. The maximum nitrogen and potassium concentrations in citrange leaves (2.90 and 1.83%, respectively) were achieved in the treatment of applying 7.5% compost with no nitrogen fertilizer. The highest phosphorous concentration in citrange leaves (0.80%) was observed in the treatment of applying 2.5% compost with no nitrogen fertilizer. The maximum potassium concentration in citrange leaves in the treatment of applying 7.5% compost and 40 mg/kg nitrogen was 0.74%. The highest iron and zinc concentrations in citrange leaves (201.4 mg/kg and 16.32 mg/kg, respectively) were achieved by the application of 2.5% compost and 40 mg/kg of the nitrogen fertilizer. The maximum potassium concentration in citrange leaves by applying 7.5% compost and 80 mg/kg of the nitrogen fertilizer was 32.35 mg/kg.The highest copper concentration in citrange leaves by the application of 5% compost with no nitrogen fertilizer was 15.24 mg/kg.

Importance of different components of green roof substrate on plant growth and physiological performance

Green roof substrate is arguably the most important element of a green roof, providing water, nutrients and physical support to plants. Despite this there has been a lack of research into the role that different substrate components have on green roof plant growth and physiological performance.To address this, we assessed the importance of three green roof substrate components (organic matter type, brick particle size and water absorbent additive) for plant growth and plant physiological performance. Lolium perenne (Ryegrass) was grown in eight substrates in a controlled greenhouse environment with a factorial design in composition of (i) small or large brick, (ii) conifer bark or green waste compost organic matter, and (iii) presence/absence of polyacrylamide water absorbent gel (‘SwellGel™’).We found that large brick substrates had a lower water holding capacity than small brick (−35%), which led to decreased shoot growth (−17%) and increased root:shoot ratio (+16%). Green waste compost increased shoot and root growth (+32% and +13%) shoot nitrogen concentration and chlorophyll content (20% and 57%), and decreased root:shoot ratio (−15%) compared to bark. The addition of swell gel increased substrate water holding capacity (+24%), which increased shoot growth (+8%). Total evapotranspiration (a proxy for potential cooling) was increased by greater shoot biomass and substrate water holding capacity. Overall, this study provides one of the first quantitative assessments of the relative importance of commonly used green roof substrate components. It is clear that substrate composition should be considered carefully when designing green roofs, and substrate composition can be tailored for green roof service provision.

Aromatic Moieties from Matured Chicken Manure and Agriculture Residues Compost Suppress Growth of Lepidium sativum L. and Trichoderma harzianum

To better understand the role of organic matter (OM) prepared from chicken manure and agriculture residues compost on the growth of plants (Lepidium sativum L.) and antagonistic fungi (Trichoderma harzianum), we analyzed the structure and composition of extracted OM using fluorescence excitation-emission matrix (EEM) spectroscopy and solid-state 13C cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy. The results showed that the EEM contours of water-extracted OM (WEOM) and alkali-extracted OM (AEOM) were similar. Furthermore, solid-state 13C CPMAS NMR spectroscopy demonstrated that water extraction could not proportionally pull out aromatic moieties (112–145 ppm) from compost, but the alkali method in proportion extracted both carbohydrates (65–85 ppm) and aromatic moieties. The results suggest that AEOM may better reflect the bulk OM composition of compost, and one should be cautious when applying WEOM as an alternative indicator of total compost OM. Further investigations demonstrated that, compared to carbohydrates, aromatic moieties played a predominant role in growth suppression of Lepidium sativum L. seeds and Trichoderma harzianum.

Molecular Characterization of Organic Nitrogen in Cattle Manure Compost by Size-Exclusion HPLC with Chemiluminescent Nitrogen Detection

To characterize organic nitrogen present in cattle manure compost, a hot-water extract of the compost along with an acid-insoluble (humic acid-like) fraction either treated with alkali or laccase or untreated were separated by size-exclusion high-performance liquid chromatography (SE-HPLC). Nitrogen was then detected by chemiluminescent nitrogen detection (CLND), and humic acid-like substances were detected by measuring the absorbance at 420 nm. The acid-insoluble fraction comprised the higher molecular-weight region in the chromatogram of the whole extract, and its chromatogram pattern of CLND was similar to that of the absorbance at 420 nm. Changes in the molecular-weight distribution of the acid-insoluble fraction detected by CLND due to alkaline degradation and laccase polymerization were in agreement with those observed by measuring the absorbance at 420 nm. These results, together with other data, demonstrate that protein and humic acid-like moieties are present in the same molecule in compost organic matter.