Long-term fertilization and residue return affect soil stoichiometry characteristics and labile soil organic matter fractions

Ecological stoichiometry provides the possibility for linking microbial dynamics with soil carbon (C), nitrogen (N), and phosphorus (P) metabolisms in response to agricultural nutrient management. To determine the roles of fertilization and residue return with respect to ecological stoichiometry, we collected soil samples from a 30-year field experiment on residue return (maize straw) at rates of 0, 2.5, and 5.0 Mg ha^-1 in combination with 8 fertilization treatments:no fertilizer (F0), N fertilizer, P fertilizer, potassium (K) fertilizer, N and P (NP) fertilizers, N and K (NK) fertilizers, P and K (PK) fertilizers, and N, P, and K (NPK) fertilizers. We measured soil organic C (SOC), total N and P, microbial biomass C, N, and P, water-soluble organic C and N, KMnO₄-oxidizable C (KMnO₄-C), and carbon management index (CMI). Compared with the control (F0 treatment without residue return), fertilization and residue return significantly increased the KMnO₄-C content and CMI. Furthermore, compared with the control, residue return significantly increased the SOC content. Moreover, the NPK treatment with residue return at 5.0 Mg ha^-1 significantly enhanced the C:N, C:P, and N:P ratios in the soil, whereas it significantly decreased the C:N and C:P ratios in soil microbial biomass. Therefore, NPK fertilizer application combined with residue return at 5.0 Mg ha^-1 could enhance the SOC content through the stoichiometric plasticity of microorganisms. Residue return and fertilization increased the soil C pools by directly modifying the microbial stoichiometry of the biomass that was C limited.     

The quality of exogenous organic matter: short-term effects on soil physical properties and soil organic matter fractions

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased ( P  <   0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 × 10⁻³ m/s for the plots receiving organic amendments, compared with 0.34–0.43, and 0.42–0.64 × 10⁻³ m/s, respectively, for the unamended plots. There were significant differences between the organic amendments (P <  0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased ( P  <   0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98–1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092–0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased ( P  <   0.05), but there were no significant differences ( P  <   0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred.     

Soil fertility in organic farming systems – fundamentally different?

Abstract. Soil fertility is defined as the ability of a soil to provide the conditions required for plant growth. It is a result of the physical, chemical and biological processes that act together to provide nutrients, water, aeration and stability to the plant, as well as freedom from any substances that may inhibit growth. Within this definition, it is useful to distinguish between those components of fertility which change relatively slowly, perhaps over the course of a rotation, or in some cases, decades, and the more immediate contribution from materials such as fertilizers and manures. The term 'inherent fertility' is used to describe these more stable characteristics, while recognising that they are, to a large extent, products of soil management. We conclude that, although nutrient management in organically managed soils is fundamentally different to soils managed conventionally, the underlying processes supporting soil fertility are not. The same nutrient cycling processes operate in organically farmed soils as those that are farmed conventionally although their relative importance and rates may differ. Nutrient pools in organically farmed soils are also essentially the same as in conventionally managed soils but, in the absence of regular fertilizer inputs, nutrient reserves in less-available pools will be of greater significance.     

Qualitative and quantitative differences in particulate organic matter fractions in organic and conventional farming systems

To quantify functionally important differences in soil organic matter (SOM) that result from use of different farming practices, soils from 9 long-term trials comparing manure+legume-based organic, legume-based organic, and conventional farming systems were collected and particulate organic matter (POM) was fractionated to reflect its position within the soil matrix. The free, light POM (FPOM; <1.6 g cm⁻³) not occluded within aggregates and occluded POM (OPOM; <2.0 g cm⁻³) were compared to an undifferentiated POM fraction (coarse fraction, CF; >53 μm) obtained by wet sieving. Fraction C, N, and hydrolyzable N (quantified using the Illinois test (IL-N)) were determined. Organic farming systems had greater quantities of C and N in the OPOM and CF and, greater IL-N contents in all POM fractions considered. The OPOM's C:N ratio (16-19) and was least in the manure+legume-based organic, intermediate in the legume-based organic, and greatest in the conventional systems (P<0.10). Trends in OPOM C:N and IL-N abundance suggested occluded POM was most decomposed, and possibly a greater N reservoir, in the manured soils. The FPOM quality reflected the residues added to each system and its removal improved resolution of quality-based differences in POM associated with long-term management. Subdivision of POM revealed differences in its quality that were not evident using the undifferentiated CF. Quantification of hydrolysable N (IL-N) in POM did not enhance our understanding of management's affect on SOM quality. This multi-site comparison showed organic management simultaneously increased the size of the labile N reservoir and the amount of POM protected within aggregates; and that, occluded POM is more decomposed in manure+legume- than in legume-based organic systems. The characteristics of POM reveal how organic practices improve SOM and suggest the nutrient and substrate decay dynamics of organic systems may differ as a result of the N fertilization strategies they employ.     

Organic matter returns to soils must be higher under organic compared to conventional farming

The aim of this paper is to discuss the demand of fresh organic matter (FOM) supply to maintain soil organic matter (SOM) levels and productivity of arable soils under organic management. The basic question is whether the different frame conditions in organic vs. conventional farming result in a different and system‐specific FOM demand. If this is the case, it would follow that the farming system has to be considered in the calculation of SOM balances. SOM balances are the most common decision support tools in organic matter management. A conversion to organic farming in practice usually leads to an increase of SOM levels as well as soil microbial activity over time. The system‐specific driver of this effect is the indispensable extension of the share of (perennial) legumes in crop rotations at the expense of non‐legumes such as cereals, row crops, and maize. Extended legume cropping is essential for N supply in crop rotations as the import of N fertilizer in total is limited by organic farming regulations and mineral N fertilizer may not be used at all. Based on this characteristic of organic management, we argue that the demand of FOM supply to soils must be higher than in conventional crop production. The most relevant factors are (1) the non‐existence of mineral N fertilizer as an external N source that supports the maintenance of SOM by decreasing the demand for SOM‐N, (2) benefits of increasing SOM stocks and turnover for soil productivity under organic management, and, (3) increased mass‐losses of FOM and easily degradable SOM compartments due to higher microbial activity in soils. These effects have to be quantified and must be considered in SOM balances in order to avoid misleading assessments and erroneous decisions.     

Nitrogen pools and turnover in arable soils under different durations of organic farming: I: Pool sizes of total soil nitrogen,microbial biomass nitrogen,and potentially mineralizable nitrogen

Soil organic matter contents, soil microbial biomass, potentially mineralizable nitrogen (N) and soil pH values were investigated in the Ap horizons of 14 field plots at 3 sites which had been under organic farming over various periods. The objective was to test how these soil properties change with the duration of organic farming. Site effects were significant for pH values, microbial biomass C and N, and for potentially mineralizable N at 0—10 cm depth. The contents of total organic C, total soil N, and potentially mineralizable N tended to be higher in soils after 41 versus 3 years of organic farming, but the differences were not significant. Microbial biomass C and N contents were higher after 41 years than after 3 years of organic farming at 0—10 cm depth, and the pH values were increased at 10—27 cm depth. Nine years of organic farming were insufficient to affect soil microbial biomass significantly. Increased biomass N contents help improve N storage by soil micro‐organisms in soils under long‐term organic farming.     

Long-term effect of straw and farmyard manure on soil organic matter in field experiment in the Czech Republic

The effect of long-term (45 years) mineral and organic fertilization on soil organic matter (SOM) quantity (organic C and N content) and quality (hot-water-soluble C content, microbial biomass C content, hydrophobic organic components of SOM, soil enzyme activities) was determined in a field experiment established in Trutnov (North Bohemia, sandy loam, Eutric Cambisol). Six treatments were chosen for investigation: unfertilized control, mineral fertilization (NPK), straw N, farmyard manure (FYM) and straw and FYM completed with mineral NPK. Soil samples were taken from the arable layer (0–20 cm) in spring over the period of 2004–2010. The positive effect of FYM on the total organic C and N content, hot-water-soluble C content and hydrophobic organic components of SOM was more than 50% higher than that of straw and mineral N fertilization. Application of straw N increased microbial biomass C content in soil and generated invertase activity above the level of FYM. Hot-water-soluble C content, hydrophobic organic components of SOM and urease activity were positively correlated with total organic C and N content (R = 0.58–0.98; p < 0.05). Addition of mineral NPK to both the straw and FYM emphasized the effect of organic fertilization in most of monitored characteristics.     

不同轮作制度下土壤中不稳定有机碳组分的变化

Taking Kenli County in the Yellow River Delta, China, as the study area and using digital satellite remote sensing techniques, cultivated land use changes and their corresponding driving forces were explored in this study. An interactive interpretation and a manual modification procedure were carried out to acquire cultivated land information. An overlay method based on classification results and a visual change detection method which was supported by land use maps were employed to detect the cultivated land changes. Based on the changes that were revealed and a spatial analysis between cultivated land use and related natural and socio-economic factors, the driving forces for cultivated land use changes in the study area were determined. The results showed a decrease in cultivated land in Kenli County of 5321.8 ha from 1987 to 1998, i.e., an average annual decrement of 483.8 ha, which occurred mainly in the central paddy field region and the northeast dry land region. Adverse human activities, soil salinization and water deficiencies were the driving forces that caused these cultivated land use changes.     

水稻-小麦轮作系统中土壤活性有机碳库对长期施用化肥，秸秆和粪便的敏感度

Labile soil organic carbon(SOC) pools, estimated through chemical fractionation techniques, are considered sensitive indicators of management-induced changes in quality and composition of soil organic matter. Although the impacts of organic manure and crop residue applications on C sequestration in rice-wheat system are fairly well documented, their influence on labile SOC pools is relatively less known. Impacts of organic manure, rice straw, and inorganic fertilizer nitrogen(N) applications on soil total organic carbon(TOC)and SOC pools including water-extractable organic C(WEOC), hot water-soluble organic C(HWOC), potassium permanganateoxidizable organic C(KMnO 4-C), microbial biomass C(MBC), mineralizable organic C(Cmin), and the oxidizable fractions of decreasing oxidizability(easily-oxidizable, oxidizable, and weakly-oxidizable) were investigated in an 11-year field experiment under rice-wheat system. The field experiment included treatments of different combinations of farmyard manure, rice straw, and fertilizer N application rates, with C inputs estimated to be in the range from 23 to 127 Mg ha-1. After 11 years of experiment, WEOC,HWOC, and KMnO 4-C were 0.32%–0.50%, 2.2%–3.3%, and 15.0%–20.6% of TOC, respectively. The easily-oxidizable, oxidizable,and weakly-oxidizable fractions were 43%–57%, 22%–27%, and 10%–19% of TOC, respectively. The applications of farmyard manure and rice straw improved WEOC, HWOC, KMnO 4-C, easily-oxidizable fraction, Cmin, and MBC, though the rates of change varied considerably from-14% to 145% and-11% to 83% of TOC, respectively. At the C input levels between 29 and 78 Mg C ha-1during the 11-year period, the greatest increase was observed in WEOC and the minimum in KMnO 4-C. Water-extractable organic C exhibited a relatively greater sensitivity to management than TOC, suggesting that it may be used as a sensitive indicator of management-induced changes in soil organic matter under rice-wheat system. All the other labile SOC pools exhibited almost the same sensitivity to management as TOC. Most of the SOC pools investigated were positively correlated to each other though their amounts differed considerably. Long-term applications of farmyard manure and rice straw resulted in build-up of not only the labile but also the recalcitrant pool of SOC, emphasizing the need for continued application of organic amendments for permanence of the accrued C under the experimental conditions.     

Effects of organic versus conventional arable farming on soil structure and organic matter dynamics in a marine loam in the Netherlands

Abstract. We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg⁻¹ for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.     

Labile organic matter fractions as early‐season nitrogen supply indicators in manure‐amended soils

Soil test indicators are needed to predict the contribution of soil organic N to crop N requirements. Labile organic matter (OM) fractions containing C and N are readily metabolized by soil microorganisms, which leads to N mineralization and contributes to the soil N supply to crops. The objective of this study was to identify labile OM fractions that could be indicators of the soil N supply by evaluating the relationship between the soil N supply, the C and N concentrations, and C/N ratios of water extractable OM, hot‐water extractable OM, particulate OM, microbial biomass, and salt extractable OM. Labile OM fractions were measured before planting spring wheat (Triticum aestivum L.) in fertilized soils and the soil N supply was determined from the wheat N uptake and soil mineral N concentration after 6 weeks. Prior to the study, fertilized sandy loam and silty clay soils received three annual applications of 90 kg available N (ha · y)^?1 from mineral fertilizer, liquid dairy cattle manure, liquid swine manure or solid poultry litter, and there was a zero‐N control. Water extractable organic N was the only labile OM fraction to be affected by fertilization in both soil types (P < 0.01). Across both test soils, the soil N supply was significantly correlated with the particulate OM N (r = 0.87, P < 0.001), the particulate OM C (r = 0.83, P < 0.001), and hot‐water extractable organic N (r = 0.81, P < 0.001). We conclude that pre‐planting concentrations of particulate OM and hot‐water extractable organic N could be early season indicators of the soil N supply in fertilized soils of the Saint Lawrence River Lowlands in Quebec, Canada. The suitability of these pre‐planting indicators to predict the soil N supply under field conditions and in fertilized soils from other regions remains to be determined.     

Assessment of cropping‐system impact on soil organic matter levels in short‐term field experiments

It has been suggested that short‐term field experiments are not suitable for the quantitative assessment of cropping‐systems impact on soil organic matter (SOM) levels in arable soils, as expectable temporal changes are very small compared to a large spatial variation of SOM background levels. However, applying an optimized sampling design based on repeated sampling in small plots, we were able to detect soil total carbon (STC) and nitrogen (STN) changes in the magnitude of ≈ 1% (STC) and ≈ 2% (STN) of background levels with only four replications, respectively. Gradually enlarging the sample size up to n = 24 did not considerably improve change detectability with STC, but with STN (n = 15 allowing for the dection of ≈ 1% change of background levels). The common calculation of minimum detectable differences (MDD) based on a state analysis of SOM levels instead of repeated measurements considerably underestimated change detectability.     

平菇栽培废料等有机肥对土壤活性有机质和土壤酶活性的影响

通过大田试验研究了不施有机肥(CK)、施用平菇栽培废料(T1)、施用干腐熟牛粪(T2)和烘干鸡粪(T3)在种植黄瓜01～50.d内土壤中活性有机质和4种土壤酶活性的变化。结果表明:施入不同有机肥对土壤总有机质含量的影响为烘干鸡粪平菇栽培废料干腐熟牛粪对照;对活性有机质含量的影响为平菇栽培废料烘干鸡粪干腐熟牛粪对照;施用平菇栽培废料的土壤中脲酶、转化酶和脱氢酶活性最高,施用干腐熟牛粪的土壤中过氧化氢酶活性最高。相关性分析显示,脲酶、转化酶和脱氢酶活性与土壤活性有机质显著相关。用平菇栽培废料做有机肥能有效提高土壤活性有机质含量和土壤酶活性。     

Soil carbon sequestration,plant nutrients and biological activities affected by organic farming system in tea (Camellia sinensis (L.) O. Kuntze) fields

There is growing interest in investigations into soil carbon (C) sequestration, plant nutrients and biological activities in organic farming since it is regarded as a farming system that could contribute to climate mitigation and sustainable agriculture. However, most comparative studies have focused on annual crops or farming systems with crop rotations, and only a few on perennial crops without rotations, e.g. tea (Camellia sinensis (L.) O. Kuntze). In this study, we selected five pairs of tea fields under organic and conventional farming systems in eastern China to study the effect of organic farming on soil C sequestration, plant nutrients and biological activities in tea fields. Soil organic C, total nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg), available nutrients, microbial biomass, N mineralization and nitrification were compared. Soil pH, organic C and total N contents were higher in organic tea fields. Soil microbial biomass C, N and P, and their ratios in organic C, total N and P, respectively, net N mineralization and nitrification rates were significantly higher in organic fields in most of the comparative pairs of fields. Concentrations of soil organic C and microbial biomass C were higher in the soils with longer periods under organic management. However, inorganic N, available P and K concentrations were generally lower in the organic fields. No significant differences were found in available calcium (Ca), Mg, sodium (Na), iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) concentrations between the two farming systems. These findings suggest that organic farming could promote soil C sequestration and microbial biomass size and activities in tea fields, but more N-rich organic fertilizers, and natural P and K fertilizers, will be required for sustainable organic tea production in the long term.     

Nitrogen mineralization and nitrogen uptake by maize as influenced by light and heavy organic matter fractions

On a sandy tropical soil, organic materials (prunings of Leucaena leucocephala, Senna siamea and maize stover) with contrasting C/N ratio (13, 18 and 56, respectively) were applied at the rate of 15 t ha^?1a^?1 in order to increase the amount of soil organic matter. Two light fractions (LF1 = LF > 2 mm and LF2 = 0.25 mm < LF < 2 mm) and the heavy fraction (HF) of the soil organic matter pool were determined by means of a combined density/particle size fractionation procedure and data obtained were related to soil nitrogen mineralization under controlled conditions and to nitrogen uptake by maize under field conditions. Under controlled conditions and when the LF1 fraction was excluded, nitrogen mineralization was found not to be correlated to total organic carbon content in the soil (R²=0.02). The R²-value of the linear regression increased considerably, when amount and C/N ratio of the LF2 fraction was taken into account in the regression analysis (R² = 0.88). Under field conditions, a multiple linear regression with amount and C/N ratio of HF, LF1 and LF2 better explained variation in crop nitrogen content and nitrogen uptake of maize (R² = 0.78 and 0.94) than a simple linear regression with total organic carbon (R² = 0.48 and 0.76). The results illustrate the importance of the two light and heavy organic matter fractions for estimating soil nitrogen mineralization. Determination of light and heavy soil organic matter fractions by density/particle size fractionation seems to be a promising tool to characterize functional pools of soil organic matter.     

Land‐Use Type Effects on Soil Organic Carbon and Microbial Properties in a Semi‐arid Region of Northeast Brazil

Land‐use change is one of the most important anthropogenic environmental change drivers affecting the biodiversity and functioning of ecosystems. However, there is limited knowledge of the consequences for soil processes in many regions around the globe. The Brazilian semi‐arid ecosystem known as Caatinga has experienced the transformation from native forest into agricultural land, with heretofore unknown effects on soil processes and microbial properties. The aim of this study was to evaluate the impact of five land‐use changes (to maize and cowpea cropland, grape orchard, and cut and grazed pasture) on total organic C (TOC) and total N (TN) stocks and soil microbial properties of Ultisol from Caatinga. Soil samples (0–10 and 10–20 cm depth) were collected during the wet and dry periods. Split–split plot analysis of variance was used to test the effects of land use, soil depth, season and the interaction between land‐use and soil depth on soil microbial properties, TOC and TN stocks. Land‐use effects were more pronounced in the top soil layer than in the lower layer, while the pattern was less consistent in soil microbial properties. Land conversion from native forest to cropland may cause C losses from the soil, but conversion to pastures may even increase the potential of soils to function as C sinks. Grazed pastures showed not only high C and N stocks but also the highest soil microbial biomass and lowest respiratory quotients, all indications for elevated soil C sequestration. Thus, grazed pastures may represent a land‐use form with high ecosystem multifunctionality in Caatinga. Copyright © 2014 John Wiley & Sons, Ltd.     

Permanent–soil monitoring sites for documentation of soil‐fertility development after changing from conventional to organic farming

For monitoring soil fertility after changing farm management from highly conventional to organic farming on the newly established research farm of Kassel University, two permanent–soil monitoring sites were installed in 1999. Representative locations for installing the permanent–soil monitoring sites were selected using geographical information systems (GIS), based on available data from geology, topography, soil taxation, land use, and intensive auger‐borehole records and analysis with a very high spatial resolution of data. The soils are represented by a Luvisol derived from loess and a Vertisol developed from claystone. The soil properties of the two monitoring sites measured immediately after changing to organic farming showed high contents of extractable nutrients as a result of the former intensive fertilization practice during conventional farm management. The microbial soil properties of the two monitoring sites were in the medium range of regional soils. A first evaluation of the development of soil properties was done after 5 y of monitoring. The soil organic‐matter content increased slightly after grass‐clover and after application of farmyard manure. The amounts of K and P decreased clearly at the loess site without application of farmyard manure. At the clay site, the unique application of farmyard manure led to increasing contents of extractable K and P in the top soil. The variation of soil properties increased clearly after perennial crops like grass‐clover and in years after application of farmyard manure.     

Effect of burning on soil organic matter content and N mineralization under shifting cultivation system of Karen people in Northern Thailand

In the traditional shifting cultivation system practiced by the Karen people in northern Thailand, the effects of burning on the content of extractable organic matter, microbial biomass, and N mineralization process of the soils were studied. Five plots (5×5 m² quadrat) with 0, 10, 20, 50, and 100 Mg ha^-1 of slashed materials were arranged and burned. Ten to 20 Mg ha^-1 of slashed biomass corresponded to the amount commonly burned by the Karen people. During the burning process, the soil temperature at the depth of 2.5 cm in the 100 Mg ha^-1 plot almost evenly increased to 300°C while the temperature in the 10 to 50 Mg ha^-1 plots increased with large variations from 50 to 300°C. Burning caused a conspicuous increase in the contents of organic C and (organic + mineral)-N extracted at room temperature and a simultaneous decrease in the contents of microbial biomass C and N, especially in the soil of the 100 Mg ha^-1 plot. In the rainy season, the values of the changes induced by burning reverted to the values recorded before burning, except for the microbial biomass in the 100 Mg ha^-1 plot, which still remained lower. Based on an incubation experiment, N mineralization rate was higher in the soils taken just after burning, especially in the 100 Mg ha^-1 plot, than in the soils taken during the rainy season. However, the soil in the 100 Mg ha^-1 plot was considered to have the lowest ability to supply mineral N among the soils in the rainy season. Burning of 10 to 20 Mg ha^-1 biomass corresponding to the values recorded in Karen peoples' shifting cultivation system was more compatible with soil ecology in terms of N supply at the initial stage of crop growth and of microbial biomass recovery during the rainy season, compared to the burning of 100 Mg ha^-1 biomass corresponding to the value recorded in a natural forest. Thus, the shifting cultivation system implemented by the Karen people can be considered to be a well-balanced agricultural system.     

Detectability of degradable organic matter in agricultural soils by thermogravimetry

Sustainable agricultural land use requires an assessment of degradable soil organic matter (SOM) because of its key function for soil fertility and plant nutrition. Such an assessment for practical land use should consider transformation processes of SOM and its sources of different origin. In this study, we combined a 120‐day incubation experiment with thermal decay dynamics of agricultural soils altered by added organic amendments. The aim was to determine the abilities and limits of thermal analysis as a rapid approach revealing differences in the degradability of SOM. The carried out experiments based on two independent sampling sets. The first sample set consisted of soil samples taken from non‐fertilized plots of three German long‐term agricultural field experiments (LTAEs), then artificially mixed with straw, farmyard manure, sheep faeces, and charcoal equal to 60 Mg ha^?1 under laboratory conditions. The second sample set based on soil samples of different treatments (e.g., crop type, fertilization, cultivation) in LTAEs at Bad Lauchstädt and Müncheberg, Germany. Before and after the incubation experiment, thermal mass losses (TML) at selected temperatures were determined by thermogravimetry indicating the degradability of organic amendments mixed in soils. The results confirmed different microbial degradability of organic amendments and SOM under laboratory conditions. Thermal decay dynamics revealed incubation‐induced changes in the artificial soil mixtures primarily at TML around 300°C in the case of applied straw and sheep faeces, whereas farmyard manure showed mainly changes in TML around 450°C. Charcoal did not show significant degradation during incubation, which was confirmed by TML. Detailed analyses of the artificial soil mixtures revealed close correlations between CO₂‐C evolution during incubation and changes in TML at 300°C with R² > 0.96. Results of the soils from LTAEs showed similar incubation‐induced changes in thermal decay dynamics for fresh plant residues and farmyard manure. We conclude that the practical assessment of SOM could be facilitated by thermal decay dynamics if modified sample preparation and evaluation algorithms are used beyond traditional peak analysis.