Amount Of Soil Organic Matter Research Articles

Clarifying the evidence for microbial- and plant-derived soil organic matter, and the path toward a more quantitative understanding.

Predicting and mitigating changes in soil carbon (C) stocks under global change requires a coherent understanding of the factors regulating soil organic matter (SOM) formation and persistence, including knowledge of the direct sources of SOM (plants vs. microbes). In recent years, conceptual models of SOM formation have emphasized the primacy of microbial-derived organic matter inputs, proposing that microbial physiological traits (e.g., growth efficiency) are dominant controls on SOM quantity. However, recent quantitative studies have challenged this view, suggesting that plants make larger direct contributions to SOM than is currently recognized by this paradigm. In this review, we attempt to reconcile these perspectives by highlighting that variation across estimates of plant- versus microbial-derived SOM may arise in part from methodological limitations. We show that all major methods used to estimate plant versus microbial contributions to SOM have substantial shortcomings, highlighting the uncertainty in our current quantitative estimates. We demonstrate that there is significant overlap in the chemical signatures of compounds produced by microbes, plant roots, and through the extracellular decomposition of plant litter, which introduces uncertainty into the use of common biomarkers for parsing plant- and microbial-derived SOM, especially in the mineral-associated organic matter (MAOM) fraction. Although the studies that we review have contributed to a deeper understanding of microbial contributions to SOM, limitations with current methods constrain quantitative estimates. In light of recent advances, we suggest that now is a critical time to re-evaluate long-standing methods, clearly define their limitations, and develop a strategic plan for improving the quantification of plant- and microbial-derived SOM. From our synthesis, we outline key questions and challenges for future research on the mechanisms of SOM formation and stabilization from plant and microbial pathways.

Drivers of soil respiration across a management intensity gradient in temperate grasslands under drought

Soil respiration is an important pathway of soil organic carbon losses in temperate grasslands; however, it is rarely studied across broad management intensity gradients in a landscape. Using the soda-lime method, we measured in-situ soil CO2 efflux with single measurements of long exposure time (i.e. 3 day long) in 150 grasslands in three German regions in early summer 2018 and 2019. The grasslands ranged from unfertilized and grazed grasslands to intensively fertilized and frequently harvested ones. To assess effects of grazing and fertilization intensities and plant diversity on soil CO2 efflux, we used Structural Equation Modeling to account for direct effects and indirect effects through soil and plant organic matter quantity and quality. Soil CO2 efflux was suppressed by limited water availability caused by naturally occurring droughts in both study years. Under the prevailing environmental conditions, grazing intensity, plant biomass and plant C:N ratio were not related to soil CO2 efflux. In contrast, fertilization intensity was positively associated with soil CO2 efflux (standardized coefficient of net effect: + 0.04 in 2018 and + 0.03 in 2019). This was because fertilization led to lower plant species richness and, thus, to lower C:N ratios in soils, which were associated with higher soil CO2 efflux (plant species richness net effect: −0.09 in 2018 and −0.18 in 2019; soil C:N ratio direct effect: −0.23 in 2018 and −0.33 in 2019). Intensively managed grasslands have higher soil respiration than extensively managed, plant species-rich grasslands even under the extreme conditions of natural droughts.

Quantifying pH buffering capacity in acidic, organic-rich Arctic soils: Measurable proxies and implications for soil carbon degradation

Dynamic pH change promoted by biogeochemical reactions in Arctic tundra soils can be a major control on the production and release of CO2 and CH4, which contribute to rising global temperatures. Large quantities of soil organic matter (SOM) in these soils are susceptible to microbial decomposition, leading to pH changes during permafrost thaw. Soil pH buffering capacity (β) modulates the extent of pH change but has not been thoroughly studied and represented in predictive ecosystem scale biogeochemical models in Arctic tundra soils. In this study, we generated titration curves for 21 acidic tundra soils from three Arctic sites across northern Alaska, United States of America. Geochemical and hydrological soil properties were evaluated, and correlations with β were developed. Strong correlations between β and both gravimetric water content (Θg) (R2 = 0.847, p < 0.001) and soil water retention (SWR) (R2 = 0.849, p = 0.001) indicate that the ability of soil to retain water could be associated with its buffering properties. Correlations between β and soil organic carbon (SOC) and cation exchange capacity (CEC) were also explored, and relationships to SWR are discussed. These correlations were then used with existing soil databases reporting SOC, CEC, and SWR to estimate β across Alaska soils. We further demonstrated the quantitative relationships between β and the simulated rates of biogeochemical reactions and show that lower β leads to higher soil pH and more CH4 production. Our study provides simple proxies for β in Arctic soils and highlights the importance and implications of representing soil buffering in predictive models, thereby enabling quantitative coupling between pH dynamics associated with biogeochemical reactions. Integrating β into predictive models of Arctic biogeochemical cycling may reduce model uncertainty and further our understanding of permafrost SOM degradation accelerated by warming.

Changes in Relationships between Humic Substances and Soil Structure following Different Mineral Fertilization of Vitis vinifera L. in Slovakia

The quantity and quality of soil organic matter (SOM) depending on many edaphic and environmental factors may change in response to agriculture-related practices. The SOM humification process can be supported by the application of mineral fertilizers, but in the production vineyards, such information is lacking. NPK fertilizer alters the soil quality, and therefore, the aim of this study was to: (1) assess the extent and dynamics of different NPK (control—no fertilization; 1st NPK; and 3rd NPK levels) rates to the soil with grass sward cover in a productive vineyard on changes in SOM, humic substances (HS), and soil structure, and (2) identify relationships between SOM, HS, and soil structure. Results showed that the share of humic acids in soil organic carbon decreased only in NPK1 compared to control and NPK3 treatments. The color quotient of humic substance values in NPK1 and NPK3 increased by 4 and 5%, respectively, compared to control. Over a period of 14 years, the content of soil organic carbon increased by 0.71, 0.69, and 0.53 g kg−1 year−1 in the control, NPK1, and NPK3, respectively. The content of HS increased linearly with slight differences due to NPK application. The vulnerability of the soil structure decreased due to fertilization—more at the higher NPK level. The rate of formed soil crust was decreasing in the following order: control &gt; NPK1 &gt; NPK3. In the control treatment, the relations between SOM, HS, and soil structure were most abundant and with the greatest significance, while with the increasing level of NPK, these relations lost their significance.

The Influence of Organic and Mineral Fertilizers on the Quality of Soil Organic Matter and Glomalin Content

The influence of different fertilizers (mineral/organic) on the quantity and quality of soil organic matter was monitored in long-term stationary experiments (27 years) with silage maize monoculture production on Luvisol. The main aim of this study was to investigate the relationship between easily extractable glomalin (EEG), total glomalin (TG), and parameters commonly used for the determination of soil organic matter quality, i.e., the content of humic acids (CHA), fulvic acids (CFA), and potential wettability index (PWI). A significant correlation was found between EEG content and CSOM content, humic acid content (CHA), humic acid/fulvic acid ratio (CHA/CFA), PWI, and index of aromaticity (IAR). Furthermore, the contents of EEG and TG correlated with soil organic carbon (CSOM). Periodical application of sewage sludge and cattle slurry increased the content of glomalin in soils. From the results, it is obvious that data about glomalin content can be used to study soil organic matter quality. A more sensitive method (a method that reacts more to changes in components of soil fertility) seems to be the determination of EEG rather than TG. The factors supporting use of EEG extraction in agronomic practice are mainly the substantially shorter time of analysis than TG, CHA, and CFA determination and lower chemical consumption. Furthermore, the PWI method is even suitable for studying soil organic matter quality. On the other hand, the humus quality ratio (E4/E6) does not provide relevant information about soil organic matter quality.

Total vs. Partial Acid Digestion Methods for Trace Element Analysis in Archaeological Sediments

Trace element analysis of sediments from archaeological sites is a valuable method to investigate the anthropic impact and obtain information on the functions of different areas and changes in human activities. One of the most used and effective techniques to carry out this kind of analysis is inductively coupled plasma–mass spectrometry. This technique needs a previous dissolution of the sample by acid attack, but the development of the best method is still a discussed issue. In the present work, total and partial digestion methods were carried out in sediment samples of Cueva de la Cocina (Dos Aguas, Spain), and trace elements were measured and statistically compared. Major elements, soil organic matter amount, and pH data were used to evaluate the main drivers of trace element contents. The differences between the results from the two methods were highlighted. Total digestion is more effective for aluminosilicates and heavy minerals, although the partial digestion results suggested that, in most cases, the difference between the two methods is irrelevant for archaeological interpretations. Furthermore, in some cases, the total digestion of the mineral phases related to the geological contribution could mask the anthropic elemental signals.

Effects of harvest residue management on soil organic nitrogen fractions in young Cunninghamia lanceolata plantation

Different treatments of harvest residues will change the quantity and quality of soil organic matter, with direct or indirect effects on the composition and content of soil nutrient. Nitrogen is one of the most important soil nutrients. However, the response of soil organic nitrogen fractions to different harvest residue treatments is still unclear. In this study, harvest residue treatments, including harvest residue removed, residue retained and residue burnt, were set up after clear-cutting a 50-year-old mature Cunninghamia lanceolata forest in Sanming City, Fujian, China. The H2SO4 hydrolysis method was used to determine soil organic nitrogen fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 5 years of harvest residue treatments. The results showed that residue retained treatment significantly enhanced the contents of soil organic nitrogen and its liable fractions. In the 0-10 cm soil layer, soil organic nitrogen content under residue retained treatment (3.36 g·kg-1) was 1.5 and 1.3 times as those of residue removed and residue burnt treatments, respectively. Residue retained treatment had the highest contents of labile nitrogen Ⅰ and Ⅱ fractions. In 10-20 cm soil layer, the contents of soil organic nitrogen and labile nitrogen Ⅱ fraction were also significantly higher in residue retained treatment (2.20, 0.73 g·kg-1) than that in residue removed and residue burnt treatments. The labile nitrogen index Ⅱ in residue retained treatment (33.9%) was significantly higher than in residue burnt treatment (26.1%). The contents of total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass under residue retained treatment were the highest in both soil layers. Compared with residue removed treatment, residue retained treatment significantly enhanced the abundance of soil bacteria (Gram-positive bacteria and Gram-negative bacteria) in 0-10 cm soil layer. In 10-20 cm soil layer, residue retained treatment had the highest content of fungi and the lowest content of actinomycetes. Pearson analysis showed that there were significant positive correlations of labile fractions of soil organic nitrogen with total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass carbon, microbial biomass nitrogen, bacteria (Gram-positive bacteria, Gram-negative bacteria), and fungi, and negative correlations with actinomycetes. It was concluded that the retention of harvest residue was beneficial to increase the content of soil organic nitrogen and labile fractions, improve soil biochemical properties and had a positive effect on soil microbial community composition. Retention of harvest residue was an effective management measure to maintain soil fertility and improve forest productivity.

Spatiotemporal variation in soil degradation and economic damage caused by wind erosion in Northwest China

Wind erosion causes significant dust emissions in northwest China, resulting in large amounts of soil organic matter and nutrient losses. It has a significant impact on air quality, climate change, vegetation growth, and economic growth at the regional scale. In this work, the Weather Research Forecasting with Chemistry atmospheric chemical transport model was used to simulate the temporal and spatial processes of dust emissions in northwest China from 1980 to 2015. The temporal and spatial variation characteristics of the loss of soil organic matter and nutrients (total nitrogen and total phosphorus) due to dust emissions, and the economic damage from wind erosion, were simulated and calculated. Spatial patterns of soil organic matter and nutrient losses are consistent with dust emission rates across the research region. The average annual dust emissions were approximately 65.17 million tons, with losses of soil organic matter, total nitrogen, and total phosphorus resulting from dust emissions of 531,494 tons, 30,754 tons, and 37,095 tons, respectively. In addition, the average annual economic loss caused by wind erosion was 309.25 million yuan in northwest China during the entire study period. This research is valuable for understanding the role of wind erosion on the carbon and nutrient cycles and the mechanism of soil degradation in northwest China and estimating the economic impacts of wind erosion.

Distribution and migration of polycyclic aromatic hydrocarbons in sediment and water of the Three Gorges Reservoir

AbstractSediment and water samples were collected from Xiangxi Bay in the Three Gorges Reservoir area of China to study the spatial distribution, migration, and ecological risks of 16 priority polycyclic aromatic hydrocarbons (PAHs) across four periods associated with different water levels from June 2017 to March 2018. Results showed that PAH contents ranged from 178.61 to 250.20 ng L−1 in water and from 5.26 to 1,325.25 ng g−1 in sediments, leading to a classification of moderate pollution in Xiangxi Bay relative to that in other estuarine systems. Polycyclic aromatic hydrocarbon levels varied across the four stages, with the proportion of two‐, three‐, and four‐ringed PAHs increasing in water and five‐ and six‐ringed PAHs decreasing in sediment across these periods. Pearson correlation analysis showed that the amount of five‐ and six‐ringed PAHs in water was significantly and positively correlated with the amount of suspended solids (p &lt; .05) and that three‐ringed PAHs in sediments were significantly and positively correlated with the amount of soil organic matter (p &lt; .05). Based on fugacity fraction estimation, two‐ringed PAHs mainly diffused from sediment to water, whereas five‐ and six‐ringed PAHs mostly migrated from water to sediment across stages. Ecological risk assessment revealed that PAHs present a moderate ecological risk in Xiangxi Bay overall, with low ecological risk in the second and fourth water level stages and moderate ecological risk in the first and third stages in sediment.

Distribution of Phosphorus Fractions in Orchard Soils in Relation to Soil Properties and Foliar P Contents

Phosphorus (P) fractionation is the validation of the nature, solubility and relative bioavailability of P. A sequential P extraction was used to determine the distribution of plant-available P fractions in soils. The relationships of these P fractions to soil properties and foliar P contents were also determined. Results of this study showed substantial differences in soil properties among orchards. Higher amounts of soil organic matter (SOM), cation exchange capacity (CEC) and major plant nutrients were found under orchard soils when compared with control soil. Most of the soil variables varied among orchard species as loquat &gt; citrus &gt; guava. The orchard soil exhibited a slightly higher soil pH. Overall, the P fractions were higher in all types of orchard soils and lowered in the control soils. Among tree species, P fractions in soils were achieved as loquat &gt; citrus &gt; guava. The extracting agents differed for P in the order residual P &gt; HCl-P &gt; NaOH-P &gt; NaHCO3-P &gt; H2O-P. Mostly higher amounts of the P fractions were achieved in the topsoil. The average amount of extractable P was found significantly higher in those soils of fruit orchards where the total amount of P was actually higher. The higher r2 values between P fractions versus SOM, clay and CEC of soils predicted a strong interrelationship among these soil variables. Leaf N contents of loquat and guava trees were consistently higher, and leaf P contents varied as loquat &gt; citrus &gt; guava. Potassium and Ca contents were higher in citrus than in the other two species. Micronutrients were found as Fe &gt; Zn &gt; Mn &gt; Cu in the leaves. Regression models indicated a sufficient relationship between Hedley P fractions and the foliar P contents in tree species. This study indicates that the above soil properties can be used to ascertain soil P fractions, and that can influence the bioavailability of P from orchard soils.

Polycyclic aromatic hydrocarbons accumulation in soil horizons of different temperate forest stands

AbstractPollution due to polycyclic aromatic hydrocarbons (PAHs) is a serious environmental issue. The aim of this study was to determine the effect of stand species composition on PAH content. The research covered the stand soils of the Rybnik Forest District, which experiences some of the highest deposition of industrial emissions in Europe. Pine, pine–oak and oak stands growing in the same soil conditions were selected for the study. Samples for further analyses were collected from the organic, humus mineral and mineral soil horizons. The organic C and N concentrations, pH, alkaline cation content, microbiological biomass of C and N, soil enzyme activity, soil organic matter (SOM) fractions and PAH content were determined. The oak stand soils were characterised by the lowest accumulation of PAHs (2936.0 μg kg−1) with high biochemical activity expressed by enzyme activity (dehydrogenases, N‐acetyl‐β‐d‐glucosaminidase, phosphatase) and high microbiological biomass. In contrast, pine stand soils are acidified; hence, SOM decomposition is slowed, resulting in a high accumulation of PAHs (3805.0 μg kg−1). A strong correlation (r = 0.825) between PAH accumulation and SOM free light fraction (fLF) C concentration was noted. The stand species composition plays an important role in shaping the quality and quantity of SOM and soil acidification, which is reflected in the microbial activity and PAH accumulation in forest soils. Such accumulation in forest soils is related to the fractional composition of SOM, which is due to the influence of species composition through the supplied biomass.

Trend setting impacts of organic matter on soil physico-chemical properties in traditional vis -a- vis chemical-based amendment practices

Amongst the soil qualities that are taken into consideration while quantifying the fertility status of soil for agri-production, the properties of water holding capacity, bulk density, electrical conductivity and soil pH play crucially important roles, directly as well as indirectly. The role of organic matter content of soil in altering the aforesaid properties occurs through various complex interactions. In our study we attempted to understand the impact of amendments in traditional ecological knowledge (TEK)-based organic input agri-management systems (A1), versus conventional chemical-intensive agri-systems (A2) in altering/modifying the few important properties viz soil organic matter (SOM), pH, electrical conductivity (EC), bulk density, and water holding capacity of the soil in the three different crop phases viz. pre, mid and the post-harvest, spread over six cropping seasons in four years. The study area was a geo-ecologically unique terrain of Kachchh, Western India. Natural stressors as erratic rainfall, drought and salinity are a typical feature of this zone. Physico-chemical soil attributes have shown significant differences in the amendment systems. The application of organic manures and concoctions likeJivamritfrom indigenous knowledge base of local farming community, certainly rendered better organic matter content that affect soil structure and stability, which in turn affected the maximum water holding capacity (MWHC), which was significantly higher in A1 (47.53%; (Standard Error [SE] = ±0.92%) across phases and seasons than A2 (37.99%; SE = ±0.74%). Probably, for the same reason, amendments with organic inputs had a lower bulk density (1.04 g/cm3; SE = ±0.02 g/cm3) as compared to amendments with no or very few organic inputs (1.31 g/cm3; SE = ± 0.03 g/cm3).The reduction in pH and electrical conductivity in A1 may be ascribed to increased amounts of SOM as a result of addition of green manures and organic concoctions. Even during the stressed period of drought in cropping seasons of season 2 (Kharif2012) and season 3 (Rabi 2012–2013) this trend was followed. This clearly shows that salinity endurance and drought resistance are remarkable features of organically amended soils and this resilience to drought is achieved over continual usage of organic manures. The arid and semi-arid tropics are highly prone to stressors like drought, highly erratic rainfall patterns, and salinity, and the present study advocates the supremacy of TEK-based agri-management systems in soil sustainability for maintaining the soil fertility in the long run.

Impact of Biochar Amendment on Soil Properties and Organic Matter Composition in Trace Element-Contaminated Soil.

The application of biochar as an organic amendment in polluted soils can facilitate their recovery by reducing the availability of contaminants. In the present work, the effect of biochar application to acid soils contaminated by heavy metal spillage is studied to assess its effect on the quantity and composition of soil organic matter (SOM), with special attention given to soil humic acids (HAs). This effect is poorly known and of great importance, as HA is one of the most active components of SOM. The field experiment was carried out in 12 field plots of fluvisols, with moderate and high contamination by trace elements (called MAS and AS, respectively), that are located in the Guadiamar Green Corridor (SW Spain), which were amended with 8 Mg·ha−1 of olive pit biochar (OB) and rice husk biochar (RB). The results indicate that 22 months after biochar application, a noticeable increase in soil water holding capacity, total organic carbon content, and soil pH were observed. The amounts of oxidisable carbon (C) and extracted HAs in the soils were not altered due to biochar addition. Thermogravimetric analyses of HAs showed an increase in the abundance of the most thermostable OM fraction of the MAS (375–650 °C), whereas the HAs of AS were enriched in the intermediate fraction (200–375 °C). Spectroscopic and chromatographic analyses indicate that the addition of biochar did not alter the composition of the organic fraction of HAs, while Cu, Fe, and as were considerably accumulated at HAs.

Addressing the soil carbon dilemma: Legumes in intensified rotations regenerate soil carbon while maintaining yields in semi-arid dryland wheat farms

Semi-arid regions support the majority of global wheat production, but they are threatened by continued soil erosion and increased risk of drought and extreme temperatures from climate change. Enhancing soil organic matter (SOM) is a key adaptation strategy for sustaining agriculture in these regions because it can improve water retention and nutrient cycling. When seeking to increase SOM, growers face a dilemma, known as the ‘soil carbon (C) dilemma’ (Janzen, 2006): How can SOM be increased, while also increasing the release of nutrients that accompanies decomposition? Our observational study examined whether growers could address this dilemma through intensification with diverse grain crops. We specifically tested whether incorporating legumes into a continuous rotation influences the form and amount of SOM as well as productivity in farms of the central Great Plains region of the U.S. by contrasting three, no-till rotation systems: 1) conventional wheat-fallow; 2) continuous grain-only rotations, and 3) continuous grain rotations that incorporate a legume crop. We sampled on-farm fields and experimental agricultural research station plots that had received one of these rotations for at least eight years. We compared yield, soil organic C (SOC), and nitrogen (N) stocks in bulk soil to 1 m, as well as SOC and N in particulate organic matter (POM) and mineral-associated organic matter (MAOM) in surface soils (0–10 cm) among the different rotations. We also estimated the long-term effects of the rotations on SOC fractions through a simulation of each rotation with the MEMS 1.0 model, verified with measured data.We found that intensifying the rotation with continuous grains led to 1.5-fold increase in aggregate size but did not change SOC stocks. Incorporating a legume to the continuous grain rotation resulted in 1 Mg C ha-1 more SOC on average in surface soil compared to wheat-fallow rotations. No significant soil changes among rotations were observed at depth. Longer-term simulations of these cropping systems suggest that including legumes could allow for 10% greater SOC gains over time compared to wheat-fallow. Since legume incorporation also increased crop yields across the full rotation cycle, our results support our hypothesis that growers can solve the ‘soil C dilemma’ by simultaneously increasing the quantity and N-content of soil input through continuous cropping with both grains and legumes.

Positive associations of soil organic matter and crop yields across a regional network of working farms

AbstractThe amount of soil organic matter (SOM) is considered a key indicator of soil properties associated with higher fertility. Despite the ubiquity of assumptions surrounding SOM's contributions to soil functioning, we lack quantitative relationships between SOM and yield outcomes on working farms. We quantified the relationship between SOM and yields of corn (Zea mays L.) and silage for a dataset of 170 fields arrayed across 49 farms in a network of growers based in Wisconsin and Minnesota, USA. As SOM concentrations increase so do yields, though gains start to level off around 4% SOM. When examining the relationship between yield and soil health indicators representative of biologically active C pools, we found that mineralizable C has a stronger relationship with yield than permanganate oxidizable C. Mineral fertilizer, manure, and SOM had relationships of similar magnitude with yield, highlighting that SOM in combination with exogenous inputs likely plays an important role in driving agricultural productivity in this region. An interaction between SOM and crop rotation indicated that the impact of SOM on crop yields varied depending on rotation (continuous corn vs. corn in rotation). That is, continuous corn had lower yields than corn in rotation despite higher SOM concentrations. Our findings provide insight into the relationship between indicators of soil health, farm management, and crop yields for a set of working farms and lend support to the goals of soil health initiatives that rest on building SOM in agricultural soils to improve agricultural outcomes.

Transferability between soil organic matter measurement methods for database harmonization

Soil organic matter (SOM) is one of the most important soil-forming factors and complex with a chemical composition not fully known. The amount of SOM traditionally is estimated by stoichiometric determination of carbon dioxide (CO2) released from oxidation reaction with a chromium mixture, hence the term soil organic carbon (SOC). The two most common oxidation methods are Tyurin (T) and Walkley-Black (WB). However, the efficiency of organic carbon oxidation depends upon the conditions of the oxidation reduction (redox) reaction (temperature, reagent concentration, oxidation time), which vary for both methods. The lack of consistent results from the oxidation methods has led to widely different conversion factors. Although the Tyurin’s method has been slowly removed from some laboratories, there still remains a large number of samples, especially from Eurasia, that have been measured by this method for more than a century and continue at the present time. The objective of this research was to develop equations or pedotransfer functions (ptf) for converting SOC determined by the Tyurin method to current and more widely used methods, such as WB and dry combustion (DC).A comparative analysis was performed for the assessment of soil organic carbon content obtained by Tyurin and Walkley-Black methods for ten quality control soil samples and 100 field soil samples. The selected soils differed in their genesis, geographical origin, and organic carbon content. SOC determined by dry combustion, providing a maximum oxidation of organic carbon, was used as a standard for comparing Tyurin and WB methods. The conversion factors from Corg by DC developed from equations (ptf) were 1.15 and 1.30 for WB and Tyurin methods. The SOM measurement error for both methods did not exceed 20%. The relationship between the absorption of calibration solutions and the mass of sucrose carbon or the equivalent amount of iron (II) for the entire OC range in this study was very strong (r = 0.99). The values of the calibration function coefficients (A0, K) of the calibration functions A = A0 + Km (OC) for both methods, did not depend upon the nature of the reducing agent. The relative error of the K coefficients when using two reducing agents (Mohr’s salt or sucrose) was not more than δ2 ≤ 2.5%. Soil samples prepared using the Tyurin method experienced additional dispersion compared to the Walkley-Black method, which caused higher values in the measurement of SOC even after centrifugation of soil suspensions. The mean SOC measured value by the Tyurin method combined with 48 h settling time was comparable with the mean SOC measured by dry combustion.The established coefficients ensure that the results are transferable and consistent with the standard method. The results from this study facilitate the integration of the accumulated data that are analyzed by different methods across the Eurasian countries into one comprehensive database that could be incorporated into the global network for monitoring soil quality and carbon stocks

Soya Bitkisinin Gelişiminde Gübre, Kompost, Mikoriza ve Bakteri Uygulamalarının Etkileri

One of the most important factors that increase soil fertility is the amount of soil organic matter. One of the ways to increase soil organic matter is the addition of organic fertilizers. Yemsoy soybean cultivar was used in the study, and pot study was carried out in 3 replications according to the randomized blocks experimental design. In the study, three different fertilizer doses (EC 0- 0.5- 1), three different grape pomace compost (0- 20-40 %) were applied to the peat perlite mixture, and mycorrhiza and bacteria inoculation to these environments. At the end of a 60-day growing period, the plants were harvested from the top of the pot, and measurements were made. In the study, there was an increase in the above-ground fresh and dry weights, root fresh, and root dry weights of soybean plants grown with increasing fertilizer rates. The addition of compost to the growing medium, the addition of mycorrhiza, and bacteria caused different results in the investigated properties. The increase in compost and plant nutrition doses was effective in increasing plant growth.

The Impact of Agricultural Use of Retisols on the Molecular Structure of Humic Substances

Agricultural soil use does not only affect the amount of soil organic matter, but also the molecular composition of humic (HAs) and fulvic acids (FAs). Changed hydrothermal conditions and composition of the incoming plant residues are reflected in the rate of humification and its products. The objective of this study was to compare the molecular composition of HAs and FAs isolated from Eutric Albic Stagnic Histic Retisol (Loamic), two Eutric Albic Retisols (Loamic)—mature and arable. Plots of mature Retisols are located at a middle taiga (Komi Republic, Russia) in a bilberry-green-moss birch-spruce forest. The plot of Retisols arable is located in the fields of the Syktyvkar state farm, which is 3.3 km northeast of mature Retisol plots. The development period is about 40 years, it is sowed with a pea-oat mixture. The results obtained indicate that soil reclamation essentially increases the proportion of aromatic components and decreases the content of carboxyl and ester groups in the humic substance (HS) structure. An increased extent of hydromorphism of Retisols leads to the enrichment of HS with aliphatic fragments.

Addition of Tithonia Compost and Lime as Ultisol Soil Fertility Improvement for Oil Palm Sedling Media

Research to improve soil fertility, especially the chemical characteristics of Ultisol, has been carried out by adding compost and lime. The incubation method of soil plus compost at a dose of 0.5 kg/pot – 2 kg/pot and 1x exchanged Al lime was carried out for 2 weeks. The results of soil nutrient analysis after incubation were an increase in pH of 0.58 points, a decrease in exchanged Al to unmeasured, an increase in the C-organic content of the soil by 3.44%, an increase in the total N-value of the soil by 0.19%, an increase in the amount of soil organic matter. P-available was 5.81 ppm and exchanged K soil increased by 0.02 me/100 g soil. Likewise, the micro elements analyzed also increase. Thus there is a change in the chemical properties of the soil towards the better. The increase in nutrients N, P, K, Ca, and Mg clearly comes from tithonia, which is the result of decomposition of tithonia compost which is added containing high nutrients. In addition, tithonia compost produces organic acids that can dissolve previously insoluble nutrients into soluble ones. The improvement of the chemical properties of the soil towards a better direction is expected to be able to increase the growth of oil palm seedlings planted on the seedling medium growing.

Hot water extractable carbon in whole soil and particle-size fractions isolated from soils under contrasting land-use treatments

Context Understanding the dynamics of soil organic matter (SOM) requires that it be divided into fractions with contrasting behaviour. Aim Using soils from a field trial with a diverse set of treatments (pasture to arable conversion, ex-pasture soil maintained fallow for 13 years and arable cropping with contrasting tillage treatments), we evaluated two approaches to characterise SOM: particle-size fractionation and hot water extraction. Methods Soils were separated into four size fractions, including the &gt;50 μm fraction (particulate organic matter, considered the most labile fraction) and the &lt;5 μm fraction (stabilised C associated with clay particles). Hot water extractable C (HWC; 80°C for 16 h) was determined on whole soil and on the isolated size fractions. Key results Whereas total soil C stocks (0–25 cm) declined by an average of 14% under arable cropping and by 23% under continuous fallow, the decline in HWC was much greater (31% under arable and 49% under bare fallow). A large part (&gt;50%) of the C lost under cropping and bare fallow was derived from the clay fraction, which was also the source of 59–77% of HWC. Conclusions and Implications Our results indicate that hot water is specific for the labile component of SOM while SOM in size fractions is a composite of labile and stable components, the proportions of which may vary depending on land use and other factors. Ideally, data on quantity of SOM in size fractions should be complemented by information on its lability.