Light Fraction Of Organic Matter Research Articles

Assessment of organic matter state and physical properties of postagrogenic sod-podzolic soil and its arable analogue

Land is often withdrawn from agriculture for various reasons, about 1/4 of the world’s fallow land is in Russia, mainly in the taiga forest zone. Some changes, determined by a combination of various factors, take place in fallow land. Therefore, in order to determine the expediency or priority of returning fallow land to arable land, it is relevant to assess the main indicators of its fertility. To this end, a comparative study of the organic matter and physical properties of an arable sod-podzolic soil and its post-agricultural analogue, which has been fallow for more than 20 years, was carried out. A reliable increase in the carbon content of the light fraction of organic matter in the 0-10 cm layer of the fallow soil was observed in comparison with the corresponding horizon of the arable analogue. In the 10-20 cm horizon this increase was manifested in the form of a tendency, also the tendency of increase in the content of organic carbon (total humus) in the former arable layer of the fallow soil was manifested. The increase in these indicators of the state of organic matter is apparently due to the increase in the amount of plant residues as a result of the succession of natural herbaceous vegetation compared to the amount of post-harvest residues on arable land. The fallow soil also showed an increase in the number of macroaggregates, agronomically valuable aggregates and the water holding capacity of macroand microaggregates compared to the arable soil. Obviously, such an improvement in the structural condition indicators is related to the increase in humus content and the absence of mechanical tillage, which favours the destruction of aggregates. The fallow soil in comparison with the arable soil had reliably lower density and density of solid phase, which is explained by higher content of light fraction of organic matter in it, as well as better structure. The obtained results allow to assess the nature of changes in fertility indicators of sod-podzolic soil as a result of staying in fallow condition. The indicator of the content of the light fraction of organic matter is an earlier indicator of the recovery of the fallow soil compared to the total carbon content in the soil, which allows to determine the expediency and priority of the return of fallow soils to arable land.

Carbon indices to assess quality of management systems in a Subtropical Acrisol

ABSTRACT: Management systems to improve soil quality are essential for agricultural and environmental sustainability. We assessed the quality of soil management systems applied to a subtropical Acrisol in terms of the carbon management index (CMI), the stratification ratio for total organic carbon (SR-TOC) and light fraction of organic matter (SR-LF). In addition, we examined their relationship to chemical, physical and biological soil quality indicators, as well as to maize yield. The study was conducted on a long-term experiment (18 years) in southern Brazil involving two different systems [no tillage (NT) and conventional tillage (CT)], two cropping systems [black oat/maize (O/M) and black oat + vetch/maize + cowpea (OV/MC)] and two nitrogen fertilizer rates for maize (0 and 180 kg ha–1). Based on the three indices, the best managements for soil quality comprised NT (50-212 % better than CT), legume cover crops (10-47 % better than O/M) and N fertilization (8-33 % better than no fertilizer). All three indices proved accurate to assess the impact of soil management systems, especially SR-LF, which showed increased sensitivity and close relationships with chemical, physical and biological soil quality indicators. On the other hand, a poor relationship was observed between soil C indices and maize yield, which was improved only by legume cover crops and N fertilization. The results showed that the association of no-till system to an abundant supply of crop residues is key to ensure high soil quality and crop yields in humid subtropical regions.

Intensive Management Increases Phytolith-Occluded Carbon Sequestration in Moso Bamboo Plantations in Subtropical China

Plantation management practices could markedly change the sequestration of phytolith-occluded carbon (PhytOC) in plants and soils. However, for Moso bamboo (Phyllostachys pubescens) plantations, the effect of intensive plantation management (including fertilization, tillage, and removal of understory vegetation) on the accretion rate of PhytOC in the soil-plant system is much less understood than extensive management (without fertilization, tillage, and removal of understory vegetation). The objectives of this study were to investigate the effect of intensive and extensive management practices on the production, accumulation, and runoff of PhytOC and their distribution in physical fractions in Moso bamboo plantations. Our results showed that intensive management (1) increased PhytOC production mainly due to increased forest productivity; (2) increased PhytOC storage in the heavy fraction but decreased its storage in the light fraction of organic matter, resulting in the lack of effect on soil PhytOC storage; (3) increased the rate of dissolution of phytolith and the loss of PhytOC in runoff; and (4) promoted PhytOC sequestration in the soil-plant system, mostly in the plants, due to the greater rate of PhytOC production than the rate of loss. We conclude that intensive bamboo plantation management practices are beneficial to increasing long-term PhytOC sequestration in the soil-plant system.

Soil organic matter formation as affected by eucalypt litter biochemistry — Evidence from an incubation study

Linking plant litter biochemistry, its decomposition and soil organic matter (SOM) formation is not straightforward. In this research, we evaluated the decomposition of four biochemical fractions operationally defined as i) hot-water extractable (HWE), ii) total solvent (acetone) extractable (TSE), iii) acid-base (HNO3-KOH) unhydrolyzable cellulosic fraction (CF), and iv) acid (H2SO4) unhydrolyzable (AUR) and the transfer of C from these fractions to SOM. Each biochemical fraction was Soxhlet-extracted from isotopically labeled (13C) leaves, twigs, bark and roots of eucalypt plants (120days old). The molecular composition of each fraction was inferred from thermochemolysis with tetramethylammonium hydroxide (TMAH), followed by gas chromatography coupled to mass spectrometry (GC-MS). For the incubation, we collected soil samples from the topsoil (0–20cm) of a sandy-clay loam, kaolinitic Haplic Ferralsol. Four plant organs and four biochemical fractions were arranged into a (4×4)+1 factorial scheme, including one control treatment (soil only). The samples were incubated at 80% of their water-holding capacity and kept under controlled temperature (25°C). The decomposition of the biochemical fractions was monitored by determining the CO2 concentration into the headspace of the vials at 1, 2, 3, 4, 7, 13, 21, 28, 38, 46, 70, 80, 92, 112, 148, 178, and 200days after the incubation had started. After the incubation, soil samples were submitted to density followed by particle-size fractionation. HWE and CF decomposed at faster rates than TSE and AUR throughout the incubation. The soil fraction <53μm retained a significantly higher proportion of the initial C input of HWE (32%) and AUR (31%) than TSE (19%) or CF (15%). Light fraction of organic matter (LFOM) with density<1.8gcm−3, retained a significant proportion of AUR (37%) and TSE (32%) while CF was mostly lost as CO2 (79%). Selective preservation of organic materials (e.g., long-chain lipids) within the AUR and TSE fractions appears to be a significant pathway for the formation of SOM. SOM formation through a microbial-driven pathway cannot be ruled out for any biochemical fraction evaluated, but it seems more relevant for HWE and CF. In short-term, substrate biochemistry exerts a strong influence on the conversion of eucalypt litter fractions into either CO2 or SOM. Despite inherent challenges upfront, considering such dynamics at the ecosystem level will help to improve our current understanding on C storage and CO2 emissions from soils in long-term scales.

Light fraction of organic matter under different land management systems in a Nigerian derived savanna soil

This study determined the influence of land management practices on the light fraction of soil organic matter in a derived savanna ecosystem. Soil samples were collected from Tectona grandis, Eucalyptus camadulensis, Musa paradisiaca plantations and the Natural forest in the Institute of Food Security, Environmental Resources and Agricultural Research (IFSERAR) farm, Federal University of Agriculture, Abeokuta, Nigeria. Soil samples were collected randomly under each land practices at 0-10 cm and 10-15 cm depths. Microbial identification, total heterotrophic (THC), light fraction organic matter (LFOM) were determined. Data obtained were subjected to descriptive statistics, ANOVA, and correlation analysis, means were separated using Duncan Multiple range Test. Actinomycetes, Bacillus enterobacter, Staphylococcus, Flavobacterium, Escherichia coli, Serratia, Aspergillus niger, Fusarium spp, Penicillum spp and Aspergillus flavis were identified in the four land management practices. Significantly (P&lt;0.05) highest THC was observed in the Musa paradisiaca plantation while Euclayptus had the least. Significantly (p&lt;0.05) higher LFOM was observed in plantain and teak plantation. There was positive correlation between THC and LFOM. Conclusive, the study revealed that light fraction contents provide a sensitive and reasonably precise measure of organic matter indices. © 2013 International Formulae Group. All rights reserved.Keywords: light fraction, organic matter, management system, derived savanna.

Carbono total e δ13C em agregados do solo sob vegetação nativa e pastagem no bioma cerrado

Diferentes sistemas de uso e manejo alteram o teor de carbono no solo (C), porém diminuições no C do solo têm sido reportadas quando áreas de Cerrado nativo são convertidas em pastagem. Disso resulta a necessidade da realização de pesquisas em diferentes sistemas e condições edafoclimáticas, a fim de elucidar as tendências encontradas. O objetivo deste trabalho foi avaliar a agregação, os teores de C e a abundância natural de δ13C do solo em uma área cultivada há nove anos sob lavoura seguida de 20 anos sob pastagem, a qual atualmente apresenta sinais de degradação (PA), comparando-a a uma vegetação nativa no bioma Cerrado (CE) que ocorre em área adjacente. As áreas de estudo estão localizadas no município de Rio Verde (GO), em solo classificado como Latossolo Vermelho distrófico, de textura argilosa. Em amostras de solo coletadas nas camadas de 0-5, 5-10 e 10-20 cm de profundidade, foram determinados a distribuição de agregados estáveis em água (micro, meso e macroagregados), o diâmetro médio aritmético (DMA) e geométrico (DMG), os teores de C total e de δ13C, o tempo de residência média do C (TRM) e a fração da matéria orgânica leve livre (FLL). Os resultados indicaram que o uso sob lavoura seguido de pastagem reduziu em 21 % o estoque de C original, possivelmente devido ao menor aporte de material na FLL. O solo apresentou elevada agregação e não houve diferenças significativas entre as áreas avaliadas. No entanto, os teores de C nos macroagregados foram menores na PA em relação ao CE, enquanto nos microagregados não houve diferença entre os sistemas de uso, sugerindo, respectivamente, maior e menor sensibilidade ao manejo e menor e maior proteção do C por essas classes de agregados. Os valores de TRM e as análises isotópicas reforçaram esses resultados, mostrando, ainda, substituição de 83 % do C original durante os 29 anos de cultivo. O constante aporte de resíduos vegetais, assim como a manutenção do C no interior dos macro e mesoagregados, são importantes fatores para que ocorra o acúmulo de C nesse tipo de solo.

Changes in Vertisol properties as affected by organic amendments application rates

AbstractThere is considerable global interest in using recycled organic materials because of perceived benefits to soil health and environment. However, information on the effects of organic waste products and their optimal application rates on the quality of heavy clay soils such as Vertisols is sparse. An incubation experiment was therefore conducted using five organic amendments at various rates to identify their optimal application rates, which could improve the quality of the Vertisol. Cotton gin trash, cattle manure, biosolids (dry weight basis 7.5–120 t/ha), chicken manure (dry weight basis 2.25–36 t/ha) and a liquefied vermicast (60–960 L/ha, volumetric basis) changed the soil chemical, physical and microbiological properties compared with a control where no amendments were applied, viz. higher light fraction of organic matter, nutrient content (N and P) and soil microbial activity. Higher application of chicken manure resulted in an increase in dry‐sieved mean weight diameter. Increasing rates of cattle manure increased exchangeable Na concentration and ESP. Although vermicast itself did not contribute a significant amount of N into the soil, when applied at higher rates (60–960 L/ha), its application resulted in increased concentration of NO3‐N in soil by amounts ranging from 43 to 429%. Optimal application rates for cattle manure and cotton gin trash were 30 t/ha, whereas for biosolids and chicken manure, the optimum rate was 60–18 t/ha, respectively.

Efeito da Gliricidia sepium sobre nutrientes do solo, microclima e produtividade do milho em sistema agroflorestal no Agreste Paraibano

Gliricidia sepium é uma leguminosa arbórea que tem sido utilizada em sistemas em aléias no semi-árido nordestino por apresentar bom desenvolvimento em condições de estresse hídrico. Entretanto, há pouca informação disponível sobre o efeito da introdução dessa espécie nos agroecossistemas da região. No presente estudo, objetivou-se avaliar a influência da distância de plantas de Gliricidia sepium sobre características da cultura do milho e do solo e microclima no Agreste Paraibano. O estudo foi realizado no município de Esperança (PB), em área de 0,5 ha, onde, em 1996, foram plantadas fileiras de G. sepium espaçadas 6 m entre si e com 1 m entre as árvores. Nesta área, em 2002, foram delimitadas quatro parcelas de 6 x 8 m e, em cada parcela, foi estabelecido um transeto perpendicular às fileiras de árvores com três posições de amostragem: (1) nas fileiras de árvores (0 m); (2) a 1 m das fileiras de árvores, e (3) a 3 m de distância das fileiras de árvores. O delineamento experimental utilizado foi em blocos casualizados com quatro repetições. A massa seca de folhedo caído embaixo da fileira de árvores foi de 1.390 kg ha-1 e diminuiu, gradativamente, para 270 kg ha-1 a 3 m de distância das árvores. As concentrações de P, K e matéria orgânica leve (MOL) embaixo das árvores foram maiores do que a 1 e 3 m de distância das fileiras. As médias mensais das temperaturas mínimas do ar e do solo embaixo e a 3 m das árvores foram similares. Entretanto, as médias mensais das temperaturas máximas do solo e do ar foram de 6 e 2 °C mais altas a 3 m das árvores, respectivamente, ao longo do período de estudo. A umidade do solo foi significativamente menor embaixo das árvores do que a 1 e 3 m de distância. O milho produziu mais grãos e palha e acumulou mais nutrientes nas posições mais próximas das fileiras de G. sepium.

Enhancement of growth and reproduction of the tropical earthworm Polypheretima elongata (Megascolecidae) by addition of Zea mays and Mucuna pruriens var. utilis litter to the soil

The effect of light fractions of organic matter of different origin, on the growth and reproduction of the mesohumic endogeic earthworm Polypheretima elongata, has been tested in laboratory cultures. Earthworms were fed with savannah soil from “La Mancha” Veracruz (Mexico), added with different amounts of fresh or composted Mucuna pruriens var. utilis (Leguminosae), or Zea mays (Graminaceae) leaf material. Earthworm cultures were performed under controlled conditions of temperature (27 °C) and humidity (33% on a dry weight basis) during 63 days for the growth study and 98 days for the reproduction study. The highest individual fresh weight (5.8 ± 0.7 g after 63 days) and the highest cocoon production (33 ± 8.4 cocoons ind −1 in 98 days) were obtained when litter of M. pruriens var. utilis was added to the soil. Mucuna leaf material was more efficient when fresh, whereas maize litter gave higher growth and fecundity rates when composted for 6 weeks. The addition of organic matter from the light fraction of the soil did not improve earthworm growth.

Cultivation and grassland type effects on light fraction and total organic C and N in a Dark Brown Chernozemic soil

Light fraction of organic matter is a source of nutrients for plants and a substrate for microbes, while total organic matter is critical for optimum physical conditions and retention of nutrients and other chemicals in soil. The objective of this study was to evaluate the effects of cultivation and grassland type on light fraction and total C and N in a Dark Brown Chernozemic soil. Three paired-sets of soil samples, in five replications, were collected from three cultivated field areas under annual crops [mostly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)] and from three adjacent grassland areas. The three sets were a 30-yr-old bromegrass (Bromus inermis Leyss.)/alfalfa (Medicago sativa L.) dominated stand cut annually for hay (Lm) and cultivated area 1 (Ct1), an unbroken native grass stand having no vegetation removed (Ng) and cultivated area 2 (Ct2) and a bromegrass/crested wheatgrass (A gropyron cristatum L. Gaertn.) dominated stand on a land reverted to grassland 60 yr ago having no vegetation removed (Og) and cultivated area 3 (Ct3). Soil samples from the 0- to 5-cm, 5- to 10-cm, 10- to 15-cm, 15- to 20-cm and 20- to 30-cm depths were taken using a 4-cm-diameter coring tube sampler. Total organic C (TOC), total N (TN), light fraction organic C (LFOC) and light fraction N (LFN) in soil were determined and the equivalent mass technique was used to calculate their masses in different soil layers. Total mass (for all soil layers) was less in the cultivated areas compared to the grassland areas by 31 to 43% for TOC, by 84 to 85% for LFOC, by 15 to 34% for TN and by 82 to 84% for LFN. The effect of cultivation was much greater in the surface 5-cm depth compared to deeper soil layers. The proportions of LFOC in TOC and LFN in TN as well as the TOC:TN ratios were lower in the cultivated areas than in the grassland areas, whereas the LFOC:LFN ratios were similar in cultivated and grassland areas. The light fractions of C and N were thus more responsive to change from grassland to cultivation of annual crops compared to the total C and N. Within the grassland areas, the mass of TOC and TN in most of the soil layers was greater in the Lm compared to both Ng and Og areas, while the LFOC and LFN did not show the effect of grassland type. The differences in the mass of both total and light fraction C and N in the cultivated areas were small and generally not significant. The findings suggest that including legume in grassland stands can sequester more organic C and N into the soil even when used for hay production. Key words: Cultivated land, light fraction C and N, native grassland, total organic C and N

Influence of forest age on forms of carbon in Douglas-fir soils in the Oregon Coast Range

The amount and type of carbon (C) in a forest soil reflects the past balance between C accumulation and loss. In an old-growth forest soil, C is thought to be in dynamic equilibrium between accumulations and losses. Disturbance upsets this equilibrium by altering the microclimate, the amount and type of vegetation growing on a site, and properties that affect organic matter decomposition. We measured total C and forms of soil C in the L, F, and H layers and in the light fraction of soil organic matter in the 0-10 cm of mineral soil in old-, second-, and young-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) soils in the Oregon Coast Range. Total C in L, F, and H layers and in organic material in the top 10 cm of mineral soil in old-growth forests was higher than in young- or second-growth forests. Old-growth forests had a higher lignin concentration and lower concentrations of sugar, hemicellulose, and cellulose in the L, F, and H layers and in the light fraction of organic material than second- or young-growth forests. Old-growth forests had greater amounts of fats, waxes, and oils, sugar, cellulose, and lignin, in the L, F, and H layers per square hectare and greater amounts of hemicellulose, cellulose, and lignin in the light fraction of organic matter in the 0-10 cm of mineral soil per square hectare than young- and second-growth forests. Concentrations of fats, waxes, and oils, sugar, and tannin in the light fraction of organic matter in the 0-10 cm of mineral soil did not differ with forest age.