An equivalent soil mass procedure for monitoring soil organic carbon in multiple soil layers

Soil organic carbon storage (SOCS) estimation is a crucial branch of the atmospheric–vegetation–soil carbon cycle study under the background of global climate change. SOCS research has increased worldwide. The objective of this study is to develop a two-stage approach with good extension capability to estimate SOCS. In the first stage, an artificial neural network (ANN) model is adopted to estimate SOCS based on 255 soil samples with five soil layers (20 cm increments to 100 cm) in Luoding, Guangdong Province, China. This method is compared with three common methods: The soil type method (STM), ordinary kriging (OK), and radial basis function (RBF) interpolation. In the second stage, a linear model is introduced to capture the regional differences and further improve the estimation accuracy of the Luoding-based ANN model when extending it to Xinxing, Guangdong Province. This is done after assessing the generalizability of the above four methods with 120 soil samples from Xinxing. The results for the first stage show that the ANN model has much better estimation accuracy than STM, OK, and RBF, with the average root mean square error (RMSE) of the five soil layers decreasing by 0.62–0.90 kg·m−2, R2 increasing from 0.54 to 0.65, and the mean absolute error decreasing from 0.32 to 0.42. Moreover, the spatial distribution maps produced by the ANN model are more accurate than those of other methods for describing the overall and local SOCS in detail. The results of the second stage indicate that STM, OK, and RBF have poor generalizability (R2 < 0.1), and the R2 value obtained with ANN method is also 43–56% lower for the five soil layers compared with the estimation accuracy achieved in Luoding. However, the R2 of the linear models built with the 20% soil samples from Xinxing are 0.23–0.29 higher for the five soil layers. Thus, the ANN model is an effective method for accurately estimating SOCS on a regional scale with a small number of field samples. The linear model could easily extend the ANN model to outside areas where the ANN model was originally developed with a better level of accuracy.

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Soil organic carbon and nitrogen sequestration and turnover in aggregates under subtropical leucaena–grass pastures

Soil Research ◽

10.1071/sr18016 ◽

2018 ◽

Vol 56 (6) ◽

pp. 632 ◽

Cited By ~ 4

Author(s):

Kathryn Conrad ◽

Ram C. Dalal ◽

Ryosuke Fujinuma ◽

Neal W. Menzies

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Soil Aggregates ◽

Soil Mass ◽

Δ13c And Δ15n ◽

Organic C ◽

Carbon And Nitrogen ◽

Nitrogen Sequestration ◽

C And N

Stabilisation and protection of soil organic carbon (SOC) in macroaggregates and microaggregates represents an important mechanism for the sequestration of SOC. Legume-based grass pastures have the potential to contribute to aggregate formation and stabilisation, thereby leading to SOC sequestration. However, there is limited research on the C and N dynamics of soil organic matter (SOM) fractions in deep-rooted legume leucaena (Leucaena leucocephala)–grass pastures. We assessed the potential of leucaena to sequester carbon (C) and nitrogen (N) in soil aggregates by estimating the origin, quantity and distribution in the soil profile. We utilised a chronosequence (0–40 years) of seasonally grazed leucaena stands (3–6 m rows), which were sampled to a depth of 0.3 m at 0.1-m intervals. The soil was wet-sieved for different aggregate sizes (large macroaggregates, >2000 µm; small macroaggregates, 250–2000 µm; microaggregates, 53–250 µm; and <53 µm), including occluded particulate organic matter (oPOM) within macroaggregates (>250 µm), and then analysed for organic C, N and δ13C and δ15N. Leucaena promoted aggregation, which increased with the age of the leucaena stands, and in particular the formation of large macroaggregates compared with grass in the upper 0.2 m. Macroaggregates contained a greater SOC stock than microaggregates, principally as a function of the soil mass distribution. The oPOM-C and -N concentrations were highest in macroaggregates at all depths. The acid nonhydrolysable C and N distribution (recalcitrant SOM) provided no clear distinction in stabilisation of SOM between pastures. Leucaena- and possibly other legume-based grass pastures have potential to sequester SOC through stabilisation and protection of oPOM within macroaggregates in soil.

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Estimation of soil organic carbon and total nitrogen in different soil layers using VNIR spectroscopy: Effects of spiking on model applicability

Geoderma ◽

10.1016/j.geoderma.2017.01.030 ◽

2017 ◽

Vol 293 ◽

pp. 54-63 ◽

Cited By ~ 27

Author(s):

Qinghu Jiang ◽

Qianxi Li ◽

Xinggang Wang ◽

Yu Wu ◽

Xiaolu Yang ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Total Nitrogen ◽

Soil Layers ◽

Vnir Spectroscopy

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Spatial variability of soil organic carbon in a typical watershed in the source area of the middle Dan River, China

Soil Research ◽

10.1071/sr12327 ◽

2013 ◽

Vol 51 (1) ◽

pp. 41 ◽

Cited By ~ 13

Author(s):

Guo-Ce Xu ◽

Zhan-Bin Li ◽

Peng Li ◽

Ke-Xin Lu ◽

Yun Wang

Keyword(s):

Land Use ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Spatial Variability ◽

Spatial Heterogeneity ◽

Spatial Variation ◽

Soil Depth ◽

Source Area ◽

Soil Layers ◽

Land Use Types

Soil organic carbon (SOC) plays an important role in maintaining and improving soil fertility and quality, in addition to mitigating climate change. Understanding SOC spatial variability is fundamental for describing soil resources and predicting SOC. In this study, SOC content and SOC mass were estimated based on a soil survey of a small watershed in the Dan River, China. The spatial heterogeneity of SOC distribution and the impacts of land-use types, elevation, slope, and aspect on SOC were also assessed. Field sampling was carried out based on a 100 m by 100 m grid system overlaid on the topographic map of the study area, and samples were collected in three soil layers to a depth of 40 cm. In total, 222 sites were sampled and 629 soil samples were collected. The results showed that classical kriging could successfully interpolate SOC content in the watershed. Contents of SOC showed strong spatial heterogeneity based on the values of the coefficient of variation and the nugget ratio, and this was attributed largely to the type of land use. The range of the semi-variograms increased with increasing soil depth. The SOC content in the soil profile decreased as soil depth increased, and there were significant (P < 0.01) differences among the three soil layers. Land use had a great impact on the SOC content. ANOVA indicated that the spatial variation of SOC contents under different land use types was significant (P < 0.05). The SOC mass of different land-use types followed the order grassland > forestland > cropland. Mean SOC masses of grassland, forestland, and cropland at a depth of 0–40 cm were 5.87, 5.61, and 5.07 kg m–2, respectively. The spatial variation of SOC masses under different land-use types was significant (P < 0.05). ANOVA also showed significant (P < 0.05) impact of aspect on SOC mass in soil at 0–40 cm. Soil bulk density played an important role in the assessment of SOC mass. In conclusion, carbon in soils in the source area of the middle Dan River would increase with conversion from agricultural land to forest or grassland.

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ORGANIC CARBON CONTENTS AND STOCKS IN PARTICLE SIZE FRACTIONS OF A TYPIC HAPLUDOX FERTILIZED WITH PIG SLURRY AND SOLUBLE FERTILIZER

Revista Brasileira de Ciência do Solo ◽

10.1590/01000683rbcs20140177 ◽

2015 ◽

Vol 39 (4) ◽

pp. 1161-1171 ◽

Cited By ~ 6

Author(s):

Maria Sueli Heberle Mafra ◽

Paulo Cezar Cassol ◽

Jackson Adriano Albuquerque ◽

Marco André Grohskopf ◽

Andreia Patrícia Andrade ◽

...

Keyword(s):

Particle Size ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Pig Slurry ◽

No Tillage ◽

Surface Layers ◽

Soil Layers ◽

Particle Size Fractions ◽

Soluble Fertilizer ◽

Clear Predominance

The use of pig slurry (PS) as fertilizer can affect the soil quality and increase total stocks of soil organic carbon (TOC). However, the effects of PS on TOC amount and forms in the soil are not fully understood, particularly in areas under no-tillage (NT). The purpose of this study was to determine TOC contents and stocks in the particulate (POC) and mineral-associated C fractions (MAC) of an Oxisol after nine years of maize-oat rotation under NT, with annual applications of PS, soluble fertilizer and combined fertilization (pig slurry + soluble fertilizer). The experiment was initiated in 2001 in Campos Novos, Santa Catarina, with the following treatments: PS at rates of 0 (without fertilization - PS0); 25 (PS25); 50 (PS50); 100 (PS100); and 200 m3 ha-1yr-1 (PS200); fertilization with soluble fertilizer (SF); and mixed fertilization (PS + SF). The TOC content was determined in samples of six soil layers to a depth of 40 cm, and the POC and MAC contents in four layers to a depth of 20 cm. From the rate of 50 m3 ha-1yr-1 and upwards, the soil TOC content and stock increased according to the PS rates in the layers to a depth of 10 cm. The POC and MAC contents and stocks were higher in the surface layers, with a clear predominance of the second fraction, but a greater relative amplitude in the contents of the first fraction.

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Litter contribution to soil organic carbon in the processes of agriculture abandon

Solid Earth ◽

10.5194/se-6-425-2015 ◽

2015 ◽

Vol 6 (2) ◽

pp. 425-432 ◽

Cited By ~ 51

Author(s):

A. Novara ◽

J. Rühl ◽

T. La Mantia ◽

L. Gristina ◽

S. La Bella ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Soil Profile ◽

Secondary Succession ◽

Co2 Emission ◽

Soil Cores ◽

Soil Layers ◽

C Stock ◽

One Year

Abstract. The mechanisms of litter decomposition, translocation and stabilization into soil layers are fundamental processes in the functioning of the ecosystem, as they regulate the cycle of soil organic matter (SOM) and CO2 emission into the atmosphere. In this study the contribution of litters of different stages of Mediterranean secondary succession on carbon sequestration was investigated, analyzing the role of earthworms in the translocation of SOM into the soil profile. For this purpose the δ13C difference between meadow C4-C soil and C3-C litter was used in a field experiment. Four undisturbed litters of different stages of succession (45, 70, 100 and 120 since agriculture abandon) were collected and placed on the top of isolated C4 soil cores. The litter contribution to C stock was affected by plant species and it increased with the age of the stage of secondary succession. One year after the litter position, the soil organic carbon increased up to 40% in comparison to soils not treated with litter after 120 years of abandon. The new carbon derived from C3 litter was decomposed and transferred into soil profile thanks to earthworms and the leaching of dissolved organic carbon. After 1 year the carbon increase attributed to earthworm activity was 6 and 13% in the soils under litter of fields abandoned for 120 and 45 years, respectively.

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The Vertical Differences in the Change Rates and Controlling Factors of Soil Organic Carbon and Total Nitrogen along Vegetation Restoration in a Subtropical Area of China

Sustainability ◽

10.3390/su12166443 ◽

2020 ◽

Vol 12 (16) ◽

pp. 6443

Author(s):

Zhiwei Cao ◽

Xi Fang ◽

Wenhua Xiang ◽

Pifeng Lei ◽

Changhui Peng

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Total Nitrogen ◽

Surface Soil ◽

Lower Layer ◽

Soil Layer ◽

Vegetation Restoration ◽

Soil Factors ◽

Deep Soil ◽

Soil Layers

The study was to investigate the change patterns of soil organic carbon (SOC), total nitrogen (TN), and soil C/N (C/N) in each soil sublayer along vegetation restoration in subtropical China. We collected soil samples in four typical plant communities along a restoration chronosequence. The soil physicochemical properties, fine root, and litter biomass were measured. Our results showed the proportion of SOC stocks (Cs) and TN stocks (Ns) in 20–30 and 30–40 cm soil layers increased, whereas that in 0–10 and 10–20 cm soil layers decreased. Different but well-constrained C/N was found among four restoration stages in each soil sublayer. The effect of soil factors was greater on the deep soil than the surface soil, while the effect of vegetation factors was just the opposite. Our study indicated that vegetation restoration promoted the uniform distribution of SOC and TN on the soil profile. The C/N was relatively stable along vegetation restoration in each soil layer. The accumulation of SOC and TN in the surface soil layer was controlled more by vegetation factors, while that in the lower layer was controlled by both vegetation factors and soil factors.

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Land-use and historical management effects on soil organic carbon in grazing systems on the Northern Tablelands of New South Wales

Soil Research ◽

10.1071/sr12376 ◽

2013 ◽

Vol 51 (8) ◽

pp. 668 ◽

Cited By ~ 14

Author(s):

Brian R. Wilson ◽

Vanessa E. Lonergan

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Surface Soil ◽

Soil Depth ◽

New South ◽

New South Wales ◽

Soil Layers ◽

South Wales ◽

Native Pasture ◽

Historical Management

We examined soil organic carbon (SOC) concentration (mg g–1) and total organic carbon (TOC) stock (Mg ha–1 to 30 cm soil depth) in three pasture systems in northern New South Wales: improved pasture, native pasture, and lightly wooded pasture, at two sampling times (2009 and 2011). No significant difference was found in SOC or TOC between sample times, suggesting that under the conditions we examined, neither 2 years nor an intervening significant rainfall event was sufficient to change the quantity or our capacity to detect SOC, and neither represented a barrier to soil carbon accounting. Low fertility, lightly wooded pastures had a slightly but significantly lower SOC concentration, particularly in the surface soil layers. However, no significant differences in TOC were detected between the three pasture systems studied, and from a carbon estimation perspective, they represent one, single dataset. A wide range in TOC values existed within the dataset that could not be explained by environmental factors. The TOC was weakly but significantly correlated with soil nitrogen and phosphorus, but a more significant pattern seemed to be the association of high TOC with proportionally larger subsoil (0.1–0.3 m) organic carbon storage. This we attribute to historical, long-term rather than contemporary management. Of the SOC fractions, particulate organic carbon (POC) dominated in the surface layers but diminished with depth, whereas the proportion of humic carbon (HUM) and resistant organic carbon (ROC) increased with soil depth. The POC did not differ between the pasture systems but native pasture had larger quantities of HUM and ROC, particularly in the surface soil layers, suggesting that this pasture system tends to accumulate organic carbon in more resistant forms, presumably because of litter input quality and historical management.

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Spatial variability and dynamics of soil pH, soil organic carbon and matter content: The case of the Wonji Shoa sugarcane plantation

Journal of Water and Land Development ◽

10.2478/jwld-2019-0045 ◽

2019 ◽

Vol 42 (1) ◽

pp. 59-66

Author(s):

Megersa Olumana Dinka ◽

Meseret Dawit

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Spatial Variability ◽

Soil Ph ◽

Ph Value ◽

Bottom Layer ◽

Matter Content ◽

Soil Layers ◽

Emission Effect ◽

Greenhouse Emission

Abstract This study presents the spatial variability and dynamics of soil organic carbon (SOC), soil organic matter (SOM) and soil pH contents at the Wonji Shoa Sugar Estate (WSSE), Ethiopia. Soil samples were collected immediately after the sugarcane was harvested and then analysed for SOC, SOM and pH content using standard procedures. The analysis results showed that the pH value varied between 6.7–8.4 (neutral to moderately alkaline) and 7.3–8.5 (neutral to strongly alkaline) for the top and bottom soil profiles, respectively. The SOM content is in the range of 1.1–6.7% and 0.74–3.3% for the upper and lower soil layers, respectively. Nearly 45% of the samples demonstrated a SOM content below the desirable threshold (<2.1%) in the bottom layer and, hence, inadequate. Moreover, most of the topsoil layer (95%) has an SOM content exceeding the desirable limit and hence is categorized within the normal range. Interestingly, the SOC content showed a spatial variability in both the surface and sub-surface soil layers. A lower SOC and SOM content was found for the sub-soil in the south and southwestern part of the plantation. A further decline in the SOC and SOM content may face the estate if the current waterlogging condition continues in the future for a long period. Overall, the study result emphasizes the need to minimize the pre-harvest burning of sugarcane and action is needed to change the irrigation method to green harvesting to facilitate the SOC retention in the soil and minimize the greenhouse emission effect on the environment, hence improving soil quality in the long-term.

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Towards accurate measurements of soil organic carbon stock change in agroecosystems

Canadian Journal of Soil Science ◽

10.4141/s05-106 ◽

2006 ◽

Vol 86 (3) ◽

pp. 465-471 ◽

Cited By ~ 85

Author(s):

A J VandenBygaart ◽

D A Angers

Keyword(s):

Experimental Design ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Bulk Density ◽

Statistical Power ◽

Prediction Models ◽

Soil Depth ◽

Soil Mass ◽

Soc Stock ◽

Stock Change

In response to Kyoto Protocol commitments, countries can elect agricultural carbon sinks to offset emissions from other sectors, but they need to verify soil organic carbon (SOC) stock change. We summarize issues we see as barriers to obtaining accurate measures of SOC change, including: soil depth, bulk density and equivalent soil mass, representation of landscape components, experimental design, and the equilibrium status of the SOC. If the entire plow depth is not considered, rates of SOC storage under conservation compared with conventional tillage can be overstated. Bulk density must be measured to report SOC stock on an area basis. More critical still is the need to report SOC stock on an equivalent mass basis to normalize the effects of management on bulk density. Most experiments comparing SOC under differing management have been conducted in small, flat research plots. Although results obtained from these long-term experiments have been useful to develop and validate SOC prediction models, they do not adequately consider landscape effects. Traditional agronomic experimental designs can be inefficient for assessing small changes in SOC stock within large spatial variability. Sampling designs are suggested to improve statistical power and sensitivity in detecting changes in SOC stocks over short time periods. Key words: Soil organic carbon change, agroecosystems, experimental design, sampling depth

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