Equivalent Mass Method Research Articles

Potential of conservation tillage, cover crops, and digestate application as integrated C farming practices for processing tomato

Conventional soil management — based on intensive tillage and low input of organic material – negatively impacts soil quality via carbon (C) losses as carbon dioxide emissions (CO2), exacerbating the effect of climate change on agriculture. Carbon farming practices (CFPs), such as minimum tillage (MT) and strip tillage (ST), offer promising solutions to maintain soil fertility, sustain crop yields, and mitigate environmental impacts. However, applying CFPs in processing tomato (Solanum lycopersicum L.) cropping presents unique challenges due to specific crop and tillage characteristics. Our two-year field study investigated the effects of conservation tillage practices (i.e., MT and ST), both combined with cover crops and digestate application, on soil quality parameters and processing tomato yield. The field studies were conducted in fields with varying soil textures (i.e., clay and silty clay loam), and aimed to evaluate responses in terms of soil C sequestration, nutrient concentrations, soil structure, and abundance of earthworms. We hypothesized that both MT and ST would enhance soil quality parameters also in tomato cropping systems, with ST potentially outperforming MT in C sequestration. Results revealed that CFPs significantly increased soil organic matter, total nitrogen, and available phosphorous compared with conventional tillage. Both MT and ST increased soil C sequestration (up to 1.06 Mg C ha−1 y−1 and 1.21 Mg C ha−1 y−1, respectively) compared with conventional tillage (CT), which lost around 0.88 Mg C ha−1 y−1 under silty-clay loam soil, and had negligible C sequestration (+0.02 Mg C ha−1 y−1) under clay soil. We found no significant difference between MT and ST when using the equivalent soil mass method for calculating C sequestration. Noteworthy, CFPs enhanced fertility parameters without a negative impact on yields, underscoring their potential for enhancing soil C sequestration, improving nutrient availability, and supporting processing tomato yield under adaptation scenarios to climate change.

Analytical and numerical study of concrete slabs reinforced by steel rebars and perforated steel plates under blast loading

Civilian buildings have been imposed to blast loading, resulting in irrecoverable damages and casualties. This paper studies the analytical and numerical performance of concrete slabs reinforced by Conventional Steel Rebars and Perforated Steel Plates based on the values recommended by ASCE Blast-Resistant and nonlinear Finite Element Analysis performed in Abaqus. ASCE Blast-Resistant proposes the equations covering the burst of any explosive materials, while Abaqus uses the TNT equivalent mass method. This study uses PSP as an alternative to CSR in concrete slabs because PSPs are more integrated with surrounding concrete than CSRs due to the particular geometry of the holes. In the analytical phase, based on ASCE Blast-Resistant, the nonlinear performance of the rectangular concrete slab reinforced with CSR under blast loading was determined. Then, in the numerical step, the square concrete slab reinforced with CSR subjected to blast loading was simulated and verified with the literature results. Furthermore, a nonlinear finite element simulation of the rectangular concrete slab was performed to validate the modeling. Moreover, the simulation results of the rectangular slab were compared with the analytical results calculated based on ASCE Blast-Resistant, revealing that the equivalent mass method used in Abaqus accurately simulates the behavior of the reinforced concrete slab under blast loading. Finally, CSRs were replaced by PSPs with an equal volume in the rectangular concrete slab to compare their performance showing that PSPs with equal volume compared to CSRs can reduce the reinforced concrete slab's maximum displacement by up to 20% and decrease its following wavelength.

A fish-skeleton-like metastructure isolator for low-frequency vibration isolation

Vibration isolation for vibration-isolated objects in low-frequency vibration environment has been widely concerned by researchers. In this paper, we designed a local resonant (LR) fish-skeleton-like metastructure isolator with cantilever beam oscillators for low-frequency vibration isolation. Based on the theories of wave dynamics and structural dynamics, we analytically obtained the bandgap characteristics and transmissibility of the metastructure by using the equivalent mass and stiffness method, and carried out simulations through the finite element method (FEM). This metastructure isolator was fabricated by a 3D printing equipment and the vibration isolation test was carried out. Vibration transmissibility characteristics is obtained through the analytical method, FEM and experiment show that the local resonance near the natural frequency of the oscillators can effectively suppress the vibration transmission. The specific performance shows that the vibration transmissibility is as low as 21 % at the center frequency of the bandgap, while the mass of the isolator is only increased by about 2.3 % compared with the ordinary structure which has no oscillators. With the increasing of the mass of vibration-isolated objects (650 g), the transmissibility can be as low as 4 %. In addition, the contribution of different frame bodies and different oscillators of the isolator on the isolation effect and a way of widening the isolation frequency ranges are clarified. The proposed fish-skeleton-like metastructure in the present work provides a new design approach for vibration isolation in engineering applications.

Simulation of the impact of the atmospheric weather state on the efficiency of functioning of solar thermal and power plants

THE PURPOSE. Determine the impact of the meteorological state of the atmosphere on the efficiency of the functioning of solar thermal and power plants. Modeling the molecular absorption of solar radiation by the atmosphere. Modeling the optical characteristics of the gaseous components of the atmosphere, atmospheric aerosol and clouds.METHODS. A method for numerical modeling of incoming solar radiation fluxes their functioning to determine the efficiency of solar thermal and power plants. The solar fluxes are calculated by stacking layers in a multi-stream approximation, taking into account the multi-tiered cloud cover and the probability of overlapping the sky with clouds. The absorption of radiation by the gaseous phase of the atmosphere is taken into account by the method of equivalent mass in an inhomogeneous atmosphere. The optical characteristics of the dispersed phase of the atmosphere are calculated using the Mie theory.RESULTS. An electronic database has been created on the optical characteristics of the gaseous components of the atmosphere, the optical characteristics of atmospheric aerosol and clouds. The effect of anthropogenic impact on the flux of solar radiation falling on the underlying surface is taken into account. The developed modeling takes into account the effect of humidity on the optical characteristics of atmospheric aerosol and its multicomponent composition, depending on the location of the power plant.CONCLUSION. The information necessary for numerical modeling of meteorological effects on the functioning of solar thermal and power plants is generalized. When calculating solar radiation fluxes, direct illumination of the light-receiving surface by solar radiation, scattered radiation by atmospheric aerosol and clouds are taken into account.

Does Grazing Affect Soil Carbon in Subtropical Humid Seminatural Grasslands?

Rangelands account for a large portion of global carbon stocks and have high potential for carbon sequestration if managed properly. Grazing has variable effects on soil organic carbon depending on climate, geography, and soil type; therefore, grazers in various regions may need to be managed differently to ensure optimum carbon sequestration. This study aimed to assess the impacts of cattle grazing on soil carbon in seminatural subtropical humid rangelands in Florida. We measured root biomass, bulk density, soil organic carbon (SOC), and total carbon (TC) concentrations and used the equivalent soil mass method to assess organic carbon stock (OCS) and total carbon stock at three depths (0−5 cm, 5−15 cm, and 15−30 cm) inside and outside of five 15-yr-old grazing exclosures. We also surveyed the vegetation at each sampling location and litter biomass inside and outside of exclosures. We found that grazing increased bulk density, decreased root biomass, but did not affect litter amount. SOC and TC concentrations did not differ significantly between ungrazed and grazed plots. On an equivalent soil mass basis, we found greater soil carbon stocks in grazed plots within the shallower part of the soil (0−5 cm). Removal of grazing resulted in a clear difference in vegetation composition between grazed and ungrazed plots, with grazed plots having higher grass cover (on average 60% in grazed vs. 13% in ungrazed) and ungrazed having higher forb cover (on average 78% in ungrazed vs. 32% in grazed). Results provide evidence that grazing increased soil carbon stocks in the top layer of soil, but longer-term studies are needed to assess the impact of grazing on SOC concentrations. To further clarify the impact of grazing on drivers of soil carbon in subtropical humid seminatural grasslands, we recommend further study of grazing impacts on productivity, root production and turnover, and microbial responses.

The effect of soil and water conservation measures on soil organic carbon in a typical small watershed in the Mollisol region of Northeast China

Soil organic carbon (SOC) content is one of the most important indicators of soil sustainability. Understanding how soil and water conservation (SWC) measures affect the SOC stock is important for the protection of soil and water quality. In the present study, the impacts of SWC measures on the SOC stock change in a typical small watershed in the Mollisol region of Northeast China were investigated using a grid soil sampling scheme. A total of 292 soil samples were collected in the same locations in 2005 and 2016. The results indicated that the average annual increase rate of SOC was 5.43‰. The equivalent soil mass (ESM) method indicated that the change rate of the SOC stock significantly increased from 2005 to 2016, with an average annual increase rate of 3.33‰. The SOC stock change was significantly affected by the SWC measures, the initial SOC content, and the interaction between the SWC measures and the initial SOC content. Furthermore, grassland had a greater change rate of the SOC stock than the other SWC measures (P < 0.05). As the initial SOC content increased, the change rate of the SOC stock significantly decreased (P < 0.05). The change rate of the SOC stock in forestland significantly increased with an increase in the initial SOC level, but the opposite trend was found in the grassland and terrace (P < 0.05). In addition, soil erosion occurred on the upper and middle slopes, and soil deposition occurred on the foot slope in the typical sloping farmland (P < 0.05); forestland had better control effect on soil erosion than farmland. Our findings provide science-based recommendations for enhancing SOC storage in agricultural sites by implementing SWC measures.

Assessing Baseline Carbon Stocks for Forest Transitions: A Case Study of Agroforestry Restoration from Hawaiʻi

As the extent of secondary forests continues to expand throughout the tropics, there is a growing need to better understand the ecosystem services, including carbon (C) storage provided by these ecosystems. Despite their spatial extent, there are limited data on how the ecosystem services provided by secondary forest may be enhanced through the restoration of both ecological and agroecological functions in these systems. This study quantifies the above- and below-ground C stocks in a non-native secondary forest in Hawaiʻi where a community-based non-profit seeks to restore a multi-strata agroforestry system for cultural and ecological benefits. For soil C, we use the equivalent soil mass method both to estimate stocks and examine spatial heterogeneity at high resolution (eg. sub 5 m) to define a method and sampling design that can be replicated to track changes in C stocks on-site and elsewhere. The assessed total ecosystem C was ~388.5 Mg C/ha. Carbon stock was highest in trees (~192.4 Mg C/ha; ~50% of total C); followed by soil (~136.4 Mg C/ha; ~35% of total C); roots (~52.7 Mg C/ha; ~14% of total C); and was lowest in coarse woody debris (~4.7 Mg C/ha; ~1% of total C) and litter (~2.3 Mg C/ha; &lt;1% of total C). This work provides a baseline carbon assessment prior to agroforest restoration that will help to better quantify the contributions of secondary forest transitions and restoration efforts to state climate policy. In addition to the role of C sequestration in climate mitigation, we also highlight soil C as a critical metric of hybrid, people-centered restoration success given the role of soil organic matter in the production of a suite of on- and off-site ecosystem services closely linked to local sustainable development goals.

Spectral radiate characteristics of gas phase combustion product of energetic fules

The results of long-term experimental studies of the spectral radiation characteristics of the gas phase of the combustion products, performed on measuring complexes of medium and high spectral resolution in the temperature range 200-2800 K, are carried out. The spectral transmission functions are parametrized by the two-parameter equivalent mass method, which makes it possible to solve radiation heat transfer problems in structurally inhomogeneous high - temperature multicomponent gas environments of the products of combustion of energy fuels of the combustion chambers of energy units to generate thermal and electrical energy. The results of modeling radiation heat transfer in combustion chambers and heat exchangers of multi - chamber furnaces with hearth multi-row burner devices and bottom feeding of solid fuel combustion products into a radiation heat exchanger from cyclone furnaces are discussed.

Analysis and comparison of potential power and thermal management systems for high-speed aircraft with an optimization method

• An advanced PTMS with an indirect regenerative air cycle is analyzed. • A comparison based on minimum fuel weight penalty optimization is proposed. • Optimal matching of the PTMS and flight mission is achieved at Mach 1-4.4. • The PTMS with a ram air bleed mode is suitable for Mach 3.4–4.4 cruise aircraft. Under the dual effects of aerodynamic heating and high-power electronic equipment heating, the heat sink and power demand of advanced high-speed aircraft have been exponentially rising, which seriously restricts the aircraft performance. To improve system cooling and power supply performance and reduce engine performance loss, a power and thermal management system (PTMS) with high performance, low energy consumption, and light weight urgently needs to be developed. In this paper, three modes of a potential PTMS with different heat sinks and bleed air sources are further discussed to analyze and compare the optimal matching with the flight mission at Mach 1–4.4. The equivalent mass method is used to uniformly assess the costs of the fixed weight, bleed, resistance, etc. as a function of the fuel weight penalty, which is chosen as the optimization objective. The optimization variables consist of the compressor outlet temperature, cooling air flow rate, and fan duct heat exchanger structure size. The results show that the intermediate-stage bleed air and fan duct heat sink are more suitable when the Mach number is less than 2, but the ram air bleed is highly suitable for flight missions at a high Mach number. Especially at Mach 3.4–4.4, the ram air bleed mode can respond to the cooling and power demands with a simple architecture.

Organic carbon storage potential in deep agricultural soil layers: Evidence from long-term experiments in northeast Italy

The significant contribution to the global carbon budget made by soil organic carbon (SOC) inspired the “4 per 1000” initiative. It promotes agricultural practices aimed at raising SOC stocks 0.4 % annually over 20 years. However, the response of topsoil and deep soil profiles to agroecosystem changes is largely unknown at present. Our work aims to quantify deep SOC accumulations in stabilized croplands and grasslands of northeast Italy and identify the best management practices to increase those stores. Soil profiles were collected to 70 and 90 cm depths from three well-established long-term experiments. A total of 1242 soil samples were analyzed for SOC concentrations as a function of soil type, soil management practice, and cropping system. SOC stocks were quantified using the equivalent soil mass method. Results show that SOC stocks averaged 23.2 Mg ha−1 in sandy Arenosol, 59.3 Mg ha−1 in silty loam Cambisol, 111.6 Mg ha−1 in clay loam Gleysol, and 383.5 Mg ha−1 in peaty Histosol. Substantial SOC stocks were found in the subsoil beneath the tilled layer, ranging between 59 % and 74 % in sandy and clay loam soils. Among the considered managements, the SOC accumulation rate of permanent meadow topsoil was higher than croplands (0.299 Mg ha−1 yr−1), which fell to 0.256 Mg ha−1 yr−1 when estimated along the full soil profile. In contrast, organic carbon added through manures and residues, coupled with minimum tillage practices, led to increased average SOC stock rates in the topsoil (0.205 Mg ha−1 yr−1) and throughout the full soil profile (0.386 Mg ha−1 yr−1), suggesting that some translocation dynamics occurred. The long-term adoption of permanent meadow, along with manure or residue addition under minimum tillage, made it possible to achieve “4 per 1000” goals to great depths in naturally poor-SOC sandy and silty loam soils. In SOC-rich soil, only in the topsoil layer achieved this.

Soils' dirty little secret: Depth-based comparisons can be inadequate for quantifying changes in soil organic carbon and other mineral soil properties.

Quantifying changes in soil organic carbon (SOC) stocks and other soil properties is essential for understanding how soils will respond to land management practices and global change. Although they are widely used, comparisons of SOC stocks at fixed depth (FD) intervals are subject to errors when changes in bulk density or soil organic matter occur. The equivalent soil mass (ESM) method has been recommended in lieu of FD for assessing changes in SOC stocks in mineral soils, but ESM remains underutilized for SOC stocks and has rarely been used for other soil properties. In this paper, we draw attention to the limitations of the FD method and demonstrate the advantages of the ESM approach. We provide illustrations to show that the FD approach is susceptible to errors not only for quantifying SOC stocks but also for soil mass-based properties such as SOC mass percent, C:N mass ratio, and δ13 C. We describe the ESM approach and show how it mitigates the FD method limitations. Using bulk density change simulations applied to an empirical dataset from bioenergy cropping systems, we show that the ESM method provides consistently lower errors than FD when quantifying changes in SOC stocks and other soil properties. To simplify the use of ESM, we detail how the method can be integrated into sampling schemes, and we provide an example R computer script that can perform ESM calculations on large datasets. We encourage future studies, whether temporal or comparative, to utilize sampling methods that are amenable to the ESM approach. Overall, we agree with previous recommendations that ESM should be the standard method for evaluating SOC stock changes in mineral soils, but we further suggest that ESM may also be preferred for comparisons of other soil properties including mass percentages, elemental mass ratios, and stable isotope composition.

Investigation of Absorption and Emission Spectra of Nitrogen Oxides NO, N2O, NO2, and N2O4

The absorption and emission spectra of NO, N2O, NO2, and N2O4 nitrogen oxides have been studied with high and intermediate spectral resolution in the range 0.25–25 μm under conditions of self-broadening and nitrogen-induced broadening at room and enhanced temperatures. The experimental data on the spectral transmittance function have been parameterized by the two-parameter equivalent mass method. The rovibrational band intensities have been measured and the data on the absorption induced by the pressure in collisions of NO2–NO2 molecules have been obtained.

The impact of land use and cover change on soil organic carbon and total nitrogen storage in the Heihe River Basin: A meta-analysis

Land use and cover change (LUCC) is an important indicator of the human-earth system under climate/environmental change, which also serves as a key impact factor of carbon balance, and a major source/sink of soil carbon cycles. The Heihe River Basin (HRB) is known as a typical ecologically fragile area in the arid/semi-arid regions of northwestern China, which makes it more sensitive to the LUCC. However, its sensitivity varies in a broad range of controlling factors, such as soil layers, LUCCs and calculation methods (e.g. the fixed depth method, FD, and the equivalent mass method, ESM). In this study, we performed a meta-analysis to assess the response of soil organic carbon (SOC) and total nitrogen (TN) storage to the LUCC as well as method bias based on 383 sets of SOC data and 148 sets of TN data from the HRB. We first evaluated the calculation methods and found that based on the FD method, the LUCC caused SOC and TN storage to decrease by 17.39% and 14.27%, respectively; while the losses estimated using the ESM method were 19.31% and 18.52%, respectively. The deviations between two methods were mainly due to the fact that the FD method ignores the heterogeneity of soil bulk density (BD), which may underestimate the results subsequently. We then analyzed the response of SOC and TN storage to various types of the LUCC. In particular, when woodland and grassland were converted into cultivated land or other land types, SOC and TN suffered from heavy losses, while other LUCCs had minor influences. Finally, we showed that increasing the depth of the soil layers would reduce the losses of SOC and TN storage. In summary, we identified a series of controlling factors (e.g. soil layer, the LUCC and calculation method) to evaluate the impact of the LUCC on SOC and TN storage in the HRB, which should be considered in future research.

Effects of land use change on soil organic carbon and total nitrogen storage in Karst immigration regions of Guangxi Province, China.

Land use change is an important factor affecting soil carbon and nitrogen cycle, and this is a hot spot in the study of global climate change. Based on the fixed depth method (FD) and the equivalent mass method (ESM), we explored the effects of land use change on soil organic carbon (SOC) and total nitrogen (TN) storage from the perspectives of forest reclamation and farmland vegetation restoration in Karst area. The storage of SOC and TN significantly decreased after the fore-sts were converted to grassland, eucalyptus and farmland. On average, the SOC and TN losses calculated by the FD method were 47.4% and 41.6%, respectively, the losses of SOC and TN calculated by ESM method were 54.8% and 49.7%. The SOC and TN storage increased significantly after abandonment of farmland to grassland or planting eucalyptus. On average, the SOC and TN stocks calculated based on the FD method increased by 60.5% and 49.7%, while the SOC and TN calculated by the ESM method increased by 85.5% and 70.8% respectively. The difference between FD method and ESM method was analyzed, it was concluded that FD method ignored the difference of soil bulk density after land use change. Soil bulk density was significantly increased after forest destruction. The loss of SOC and TN storage was overestimated by the FD method. Soil bulk density decreased after vegetation restoration, FD method will underestimate the enhancement of SOC and TN storage. It is suggested that the ESM method should be used to estimate the impacts of land use change on SOC and TN storage.

Manure and Residue Inputs Maintained Soil Organic Carbon in Upper Midwest Conservation Production Systems

Core Ideas Management potential to enhance sustainability was evaluated through change in SOC. Manure application stabilized but did not increase SOC in organic systems. Loss of SOC was prevented with manure and high residue inputs. Conservation production systems are needed in the upper Midwest to slow soil and nutrient loss through tillage‐induced erosion. However, producers are reluctant to adapt no‐till strategies because of the cool‐wet climate. With focus on strip‐tillage (ST) and a diverse 4‐yr (4y) crop rotation as alternatives to no‐till, we assessed eight integrated strategies under both conventional (CNV) and organic (ORG) management. These included conventional moldboard plow + disk tillage (CT), with (YF) fertilizer or manure, with no (NF) amendments, and 2‐yr (2y) rotations: ST‐YF‐4y, ST‐NF‐4y, ST‐YF‐2y, ST‐NF‐2y, CT‐YF‐4y, CT‐NF‐4y, CT‐YF‐2y, and CT‐NF‐2y. Temporal change and loss rates of total soil organic C (SOC) and N (SON) were measured using the equivalent soil mass method for the 0‐ to 30‐ and 0‐ to 60‐cm profiles. Soil was sampled in autumn, after harvest and before tillage, in the first, second, sixth, and eighth years of rotation between 2002 and 2009. In 2002, management had no effect on baseline measurements. Average SOC and SON from 2002–2009 were significantly greater in YF strategy systems, with no other differences among strategies occurring. Net loss in SOC, but not SON, occurred over time, and estimated rates of loss were significant for all individual management strategies, but not all integrated strategies. Under CNV, estimated rates of loss were significant in all but the CNV‐CT‐NF‐2y system. In contrast, under ORG, estimated rates of loss were significant only for ORG‐CT‐NF‐4y and ORG‐ST‐NF‐4y systems. Animal manure, particularly in combination with high residue inputs, had a positive impact for maintaining SOC.

Soil organic matter accumulation in relation to changing soil volume, mass, and structure: Concepts and calculations

Change in soil organic matter (SOM) stocks over time is a critical issue for soil fertility, soil development (pedogenesis) and the global carbon (C) cycle. Measuring such change typically relies on sampling to constant depth (CD) which is well known to be inaccurate if bulk density (BD) has changed between sampling sites or times. The usual solution to this problem is to sample an equivalent mass (EM), but in most cases soil mass also changes over time. Indeed, the whole point in measuring ΔSOM is to quantify a change in C mass. As SOM accumulates, soil volume increases (soil dilation) unless all added SOM fills in existing pores. Soil dilation as a result of root ingrowth is well documented in the geological literature but has rarely been considered in conjunction with studies of ΔSOM. Other processes that can alter soil volume include eluviation, bioturbation and dissolution/decomposition of both mineral and organic soil particles.Here, we present a method (the volume/mass corrected or VMC method) for calculating potential effects of processes that alter soil volume (V) and/or mass (M) on calculated values for ΔC and other soil characteristics. We first present a hypothetical example to illustrate the expected differences in soil V, M, bulk density (BD), porosity and ΔC when determined via CD, EM, and VMC methods. We then compare these three approaches for assessing the actual changes in soil characteristics across four soil chronosequence studies in which ΔV was actually measured, allowing ΔC to be calculated correctly. Results show errors of −75% to +49% in ΔC had the profiles been sampled via the CD method and even larger errors (−87% to +54%) had they been sampled via the EM method. Studies where V had increased (dilation) generally showed underestimates for ΔC for both CD and EM methods, whereas those where V had decreased (collapse) over time showed overestimates for ΔC for the CD and EM methods. Results are discussed in light of the few laboratory, field, and simulation studies comparing effects of changes in soil volume on ΔC measurements as well as the processes that cause changes in soil V.We hope that the VMC method provides a conceptual framework for addressing the interplay between changes in soil volume, porosity, and structure, one that will provide the foundation for a new set of mechanism-based SOM models that take into account changes in soil volume, mass, and physical structure across a wide range of spatial and temporal scales.

Carbon balance implications of land use change from pasture to managed eucalyptus forest in Hawaii

ABSTRACTMitigation of climate change via increased plant productivity and soil carbon (C) sequestration during land use change can be a powerful driver of the net greenhouse gas emissions of a sustainable production system. Yet the net climate change mitigation of managed forests is affected by both tradeoffs between C sequestration and non-renewable C emissions and assessment methodology. As a case study, we measured ecosystem stocks to determine the potential C implications of converting pasture to managed eucalyptus forest and compared them with the eucalyptus production system's non-renewable C emissions. The forest border was chosen as the system boundary and operations spanned from forest establishment activities to harvested wood placed at the forest perimeter. Eucalyptus biomass C was 57.2 ± 4.2 Mg C ha−1 and soil C stock (to ∼1 m depth) was approximately an order of magnitude greater. By the prevalent method for bulk density-based determination of C stock, conversion of pasture to eucalyptus forest significantly increased soil C stock by 17.5 ± 8.0%. However, no significant change was detected by the equivalent soil mass method, a less prevalent but more accurate approach to detecting differences in soil C stock due to land use or management changes. A 7-year eucalyptus production cycle generated 1.0 Mg C ha−1 in non-renewable emissions, which was far exceeded by the tree biomass C. Thus, even without significant soil C sequestration, this system provided a substantial climate change mitigation service by offsetting non-renewable energy use and C emissions associated with wood production, and providing opportunities for biofuel and bioenergy products to displace fossil fuel products.

Impacts of Crop Sequence and Tillage Management on Soil Carbon Stocks in South‐Central North Dakota

Core Ideas After 18 years of a study, we measured soil properties and estimated soil C. Estimates based on equivalent mass (SOCem) exceeded those based on fixed depth. Stocks of SOCem were not affected by cropping sequence at any partition depth. We found more SOCem for no‐till than minimum tillage at cumulative depths ≥30.5 cm. Organic C in the 0–7.6‐cm depth had increased, in 2012, by about 16% since 2001. Emphasis is placed on developing robust, productive, economically competitive, and environmentally benign agroecosystems. In 2012, after 18 yr of a study to evaluate the effects of crop sequence and tillage, we measured soil properties at various depths to 91.4 cm and estimated soil C. The experiment, near Mandan, ND, was a split‐plot design, with crop sequence as whole plots and tillage (minimum tillage or no‐till) as subplots. Crop sequences included continuous spring wheat (Triticum aestivum L.) with crop residue retained or removed, spring wheat–millet [Setaria italica (L.) Beauv.], spring wheat–safflower (Carthamus tinctorius L.)–fallow, spring wheat–safflower–rye (Secale cereale L.), and spring wheat–fallow. Soil organic C, calculated by the equivalent mass method (SOCem), was consistently higher (P &lt; 0.001) than when calculated by the fixed‐depth method. Disparities between the two methods, greatest near the soil surface, were attributable to tillage. Estimates of SOCem were not affected by cropping sequence at any depth, averaging about 26, 47, 73, 114, and 156 Mg ha−1 in the 0‐ to 7.6‐, 0‐ to 15.2‐, 0‐ to 30.5‐, 0‐ to 61.0‐, and 0‐ to 91.4‐cm partitions. Tillage had no influence at depths &lt;30.5 cm, but no‐till plots contained more SOCem than minimum tillage plots in the 0‐ to 61‐cm (115 vs. 112 Mg ha−1) and 0‐ to 91.4‐cm (158 vs. 153 2.3 Mg ha−1) partitions (P &lt; 0.05). Soil organic C in the 0‐ to 7.6‐cm depth increased by an average of 3.2 Mg ha−1 or 16% since 2001. This study suggests that C sequestration in soil is less impacted by the choice of crop sequence than by tillage.

Repeated monitoring of organic carbon stocks after eight years reveals carbon losses from intensively managed agricultural soils in Western Germany

AbstractPast land‐use changes, intensive cropping with large proportions of root crops, and preferred use of mineral fertilizer have been made responsible for proceeding losses of soil organic C (SOC) in the plough layer. We hypothesized that in intensive agriculturally managed regions changes in SOC stocks would be detectable within a decade. To test this hypothesis, we tracked the temporal development of the concentrations and stocks of SOC in 268 arable sites, sampled by horizon down to 60 cm in the Cologne‐Bonn region, W Germany, in 2005 and in 2013. We then related these changes to soil management data and humus balances obtained from farmers' surveys. As we expected that changes in SOC concentrations might at least in part be minor, we fractionated soils from 38 representative sites according to particle size in order to obtain C pools of different stability.We found that SOC concentrations had increased significantly in the topsoil (from 9.4 g kg−1 in 2005 to 9.8 g kg−1 in 2013), but had decreased significantly in the subsoil (from 4.1 g kg−1 in 2005 to 3.5 g kg−­1 in 2013). Intriguingly, these changes were due to changes in mineral‐bound SOC rather than to changes in sand‐sized organic matter pools. As bulk density decreased, the overall SOC stocks in the upper 60 cm exhibited a SOC loss of nearly 0.6 t C (ha · y)−1 after correction by the equivalent soil mass method. This loss was most pronounced for sandy soils [−0.73 t SOC (ha · y)−1], and less pronounced for loamy soils [−0.64 t SOC (ha · y)−1]; silty soils revealed the smallest reduction in SOC [−0.3 t SOC (ha · y)−1]. Losses of SOC occurred even with the overall humus balances having increased positively from about 20 kg C (ha · y)−1 (2003–2005) to about 133 kg C (ha · y)−1 (2005–2013) due to an improved organic fertilization and intercropping. We conclude that current management may fail to raise overall SOC stocks. In our study area SOC stocks even continued to decline, despite humus conservation practice, likely because past land use conversions (before 2005) still affect SOC dynamics.

Comparison of soil carbon and nitrogen stocks at grazing-excluded and yak grazed alpine meadow sites in Qinghai–Tibetan Plateau, China

The effects of yak grazing on C and N below-ground pools were evaluated by comparing five grazing-excluded sample site pairs (5 years of grazing exclusion) at the Eastern edge of the Qinghai–Tibetan Plateau. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), bulk density, pH and soil particle size fractions were analyzed in these samples taken at a depth of 10cm. Our results showed TK stock and bulk density had increasing trends with grazing activity. pH presented a slight increase, but the differences were not significant. On the contrary, SOC, TSN and TP stocks declined in grazing plots (P<0.05) and respectively decreased by 32.9%, 27.4%, and 10.5%, while TK stocks increased by 6.8%. P may become limited elements over time owing to an imbalance of inputs and outputs. Elemental stocks calculated by the equivalent mass method indicated the reported SOC losses based on the conventional method might be overestimated and that sampling depth of 7.64cm rather than same with sampling depth for grazing-excluded site (10cm) should be applied for grazing site if conventional method is used to calculate carbon stock. The soil silt content in grazing-excluded sites was greater than that in grazed zones (P<0.05), whilst greater soil specific surface areas were also found in the grazing-excluded sites, indicating that manual fencing led to heterogeneous distribution of soil particles and those silts may play a primary role in nutrient stocks in this region.