Modelling Long‐Term Effects of Soil Compaction on Crop Yield, Soil Organic Carbon Stocks and Nitrogen Losses From Soil

Twenty percent of agricultural management effects on organic carbon stocks occur in subsoils – Results of ten long-term experiments

Agricultural operations such as excessive tillage and intense cropping deplete soil organic carbon (SOC), making sustainable agriculture management critical for reducing greenhouse gas (GHG) emissions. This study evaluates the impact of crop intensification on soil quality and soil organic carbon stocks (SOCS) under double cropping (DC) and single cropping pattern (SC) in upper Haramosh of Gilgit, Pakistan. Soil samples were taken from cropping zones (DC and SC) under three depths (0–20, 20–40, and 40–60 cm). Standard methods were used to analyze selected soil quality parameters and SOC. Statistical analysis using ANOVA showed that soil temperature, moisture, pH, SOC, and SOCS highly significantly differed (p < 0.001) for different cropping patterns (DC and SC), whereas bulk density (BD), electrical conductivity (EC), and clay were not significantly different. The SC retained 4.4% more moisture and had lower BD than the DC, while BD increased with increasing depth. The texture of the soil was sandy loam at both cropping zones. The mean SOC and SOCS of SC were greater (by 12%) than in the DC zone. Pearson correlation showed a significant and positive correlation of SOC stock with SOC, moisture (p < 0.01), and EC (p < 0.05), but had a negative correlation with bulk density, pH (p < 0.01), and sand (p < 0.05). DC apparently degraded soil quality and organic carbon reserves, thus reducing the soil health in mountain agriculture.

In their paper "Unrecognized threat to global soil carbon by a widespread invasive species" O'Bryan et al. (2021) suggested that wild boar (also named feral pigs or wild pigs) and their grubbing reduce global soil organic carbon (SOC) stocks. In this study models were used to estimate global wild boar abundance and postulated additional CO2 emissions due to wild boar bioturbation. However, the authors ignored experimental evidence about the effects of wild boar on SOC that points in a completely different direction altogether.

Refining benchmarks for soil organic carbon in Australia’s temperate forests

Summary Uncertainties in soil organic carbon (SOC) stock assessments are rarely quantified even though they are critical in determining the significance of the results. Previous studies on this topic generally focused on a single variable involved in the SOC stock calculation (SOC concentration, sampling depth, bulk density and rock fragment content) or on a single scale, rather than using an integrated approach (i.e. taking into account interactions between variables). This study aims to apply such an approach to identify and quantify the uncertainties in SOC stock assessments for different scales and spatial landscape units (LSU) under agriculture. The error propagation method (δ method) was used to quantify the relative contribution of each variable and interaction involved to the final SOC stock variability. Monte Carlo simulations were used to cross‐check the results. Both methods converged (r 2 =0.78). As expected, the coefficient of variation of the SOC stock increased across scales (from 5 to 35%), and was higher for grassland than for cropland. Although the main source of uncertainty in the SOC stock varied according to the scale and the LSU considered, the variability of SOC concentration (due to errors from the laboratory and to the high SOC spatial variability) and of the rock fragment content were predominant. When assessing SOC stock at the landscape scale, one should focus on the precision of SOC analyses from the laboratory, the reduction of SOC spatial variability (using bulk samples, accurate re‐sampling, high sampling density or stratified sampling), and the use of equivalent masses for SOC stock comparison. The regional SOC stock monitoring of agricultural soils in southern Belgium allows the detection of an average SOC stock change of 20% within 11 years if very high rates of SOC stock changes occur (1 t C ha –1 year –1 ). Amplitude et sources des incertitudes liées aux estimations des stocks de carbone organique dans le sol (COS) à différentes échelles Résumé Les erreurs associées aux estimations du stock de carbone organique dans le sol (COS) sont rarement quantifiées bien qu’elles puissent empêcher l’obtention de résultats significatifs. Les quelques études qui le font focalisent en général sur une seule variable nécessaire au calcul du stock de COS (concentration en COS, profondeur échantillonnée, densité apparente et contenu en fragments rocheux) ou sur une échelle spatiale particulière, sans utiliser d’approche intégrée (prenant en compte les interactions entre les variables). Cette étude a pour objectif d’utiliser une telle approche pour identifier et quantifier les incertitudes liées aux estimations de stock de COS à différentes échelles spatiales et pour diverses unités spatiales de paysages (USP) agricoles. La loi de propagation des erreurs (méthode δ) permet de quantifier la contribution relative de chaque variable et interaction à la variabilité finale du stock de COS. Les simulations de Monte Carlo sont utilisées pour la vérification croisée des résultats. Les deux méthodes ont convergé (r 2 = 0.78). Comme prévu, le coefficient de variation du stock de COS a proportionnellement augmenté avec l’échelle spatiale considérée (de 5 à 35%), et était plus élevé pour les cultures que pour les prairies. Bien que la principale source d’erreur sur le stock de COS soit fonction de l’échelle spatiale et du type d’USP considérés, la variabilité du contenu en COS (du fait des erreurs de laboratoire et de sa grande variabilité spatiale) et du contenu en fragments rocheux étaient prédominants. Lors de l’estimation des stocks de COS à l’échelle du paysage, l’attention devrait prioritairement porter sur la précision des analyses en COS du laboratoire, la réduction de la variabilité spatiale du COS (en utilisant des échantillons composites, un ré‐échantillonnage précis, une densité d’échantillonnage élevée ou un échantillonnage stratifié), et sur l’utilisation de masses équivalentes pour comparer les stocks de COS. Le réseau régional de suivi des stocks de COS des sols agricoles dans le sud de la Belgique permet la détection d’un changement de stock de COS moyen de 20% en 11 ans pour un taux très élevé de changement en stock de COS (1 t C ha –1 year –1 ).

Tools used by agencies and organizations like the Forest Service (FS), the Natural Resource Conservation Service (NRCS), the Nature Conservancy (TNC), and the Central Appalachian Spruce Restoration Initiative (CASRI) to help guide red spruce (Picea rubens) ecosystem restoration within Central Appalachia could better address outcomes from management practices implemented in terms of soil organic carbon (SOC) stock changes. These high-elevation landscapes have a natural capacity to produce diverse ecosystem services that affect humans, animals, and plants alike. Ecological site descriptions (ESD) are an important tool used to restore impacted landscapes and provide detailed management prescriptions specific to red spruce ecological sites (ES) and ecological states occurring in the Monongahela National Forest (MNF). Previous studies have evaluated ESD utility for identifying ecologic communities and restoration pathways primarily in western rangelands, but none have focused on Central Appalachian landscapes. Research associated with SOC stocks and forest ESD is minimal. Studies have analyzed how SOC can benefit ecosystem services, yet none seek to compare SOC stocks across multiple ecological states to address both restoration pathways and management outcomes that could potentially increase SOC sequestration capacity while restoring impaired ecosystem services. 120 individual plots within the dual extent of the Spodic Shale Upland Conifer Forest (SSUCF) and Spodic Intergrade Shale Upland Hardwood and Conifer Forest (SISUHCF) ES were analyzed using soil profiles and ecosystem descriptions sampled between 2009 and 2021. Soil samples were analyzed using dry combustion to determine SOC percent weight and further used to calculate the SOC stock to 100 cm in depth where applicable. Here, mean SOC stock, SOC stock variance, and the relationship between percent conifer canopy cover and SOC stocks of ecological states of both ES were compared and discussed. Analyses showed differences between ES total SOC (TSOC) stock (p < 0.0001), O horizon SOC (OSOC) stock (p < 0.0001), and spodic horizon SOC (SPSOC) stocks (p = 0.001), while mineral SOC (MSOC) showed no difference (p = .628) (Table 4.1). At the ecological state level, there were only two significant differences when examining TSOC (p = 0.038) and OSOC (p = 0.001) stocks (Table 4.2). The SSUCF demonstrated higher variance than the SISUHCF in TSOC stock (p-value < 0.0001) and OSOC stock (Table 4.3, p-value < 0.0001). Conversely, there was no significant difference between ES when comparing MSOC stock variance (p-value = 0.971) and SPSOC stock variance (p-value = 0.126). Regression analysis used a fixed model and showed

Changes in soil organic and inorganic carbon stocks in deep profiles following cropland abandonment along a precipitation gradient across the Loess Plateau of China

Although soil organic matter (SOM) forms a small portion of the soil body. Nevertheless, it is the most important component of the soil ecosystem, as well as of the carbon global cycle. In the semi-arid environment, there has been little research on the spatial distribution of SOM and soil organic carbon (SOC) stock. In this study, stratified random samples of total 30 soils were collected from two different soil depth (topsoil, subsoil) of Al Balikh plain and used for mapping the spatial variability of SOC and to estimating the SOC stock. The result showed that the values were relatively homogenate, with the normal decreasing trend with increasing the depth. The standard deviation (Std. D) for both SOC and SOC stock indicates homogeneous and absence of outliers values, whereas the coefficient of variation (C.V) indicates non-dispersion and clustering of values around the average. SOC was 0.38%, 0.17% in topsoil and subsoil respectively; the corresponding averages of SOC stock were 1.23 kg·m-2 and 1.14 kg·m-2 respectively, these values reflecting typical characteristics of poor SOC semi-arid soil. The correlation between SOC and SOC stock was (R2 = 0.996, p < 0.001) in topsoil and it was (R2 = 0.941, p < 0.001) for subsoil. The semivariograms were indicated that both SOC and SOC stock were best fitted to the exponential model. Nugget, range, and sill were equal to 0.002, 0.036, and 0.044, respectively for SOC in topsoil, and 0.014, 0.071, and 0.081, for SOC in the subsoil. For SOC stock, it was 0.0, 0.036, and 0.0508, respectively in topsoil. In the subsoil, the values were 0.1899, 0.086, and 4.159, respectively. SOC and SCO stock in both two layers are shown a strong spatial dependence, for which were 4.3, 17.2 for SOC in topsoil and subsoil respectively, and 0.0, 4.5 for SOC stock in topsoil and subsoil respectively, thus, which can be attributed to intrinsic factors.

Impact of land use type and altitudinal gradient on topsoil organic carbon and nitrogen stocks in the semi-arid watershed of northern Ethiopia

Huang-Huai-Hai (HHH) plains of China account for 69.2 % of annual wheat (Triticum aestivum) and 35.3 % of annual maize (Zea mays) production in China, and are China’s principal crop production area. Thus, the understanding of crop yield response to increase in soil organic carbon (SOC) stock in different fertilizer managements, soil types, and the threshold of SOC stock in the HHH region is the key factor affecting the adoption of fertilizer managements. Thus, data from ten long-term experiments have been collated and synthesized in this article. These long-term experiments involved four groups of similar fertilizer managements: (i) no chemical fertilizer or organic as control (CK), (ii) chemical nitrogen (N) fertilizer applied without organic manure (UF), (iii) combined application of chemical fertilizer (N, P, K) without organic manure (CF), and (iv) integrated nutrient management (INM) based on use of manure/straw and chemical fertilizer (N, P, K). The results indicated that (i) Crop yield increased with increase in SOC stock in all sites across the HHH. Increase in SOC stock by one Mg ha−1 increased crop yield (kg ha−1 year−1) from 66.9 in Changpin to 333.2 in XinjiA and 495.2 in XinjiB in sub-region 1, 1,031.4 in HengshuiA, 419.2 in HengshuiB, and 148.5 in Yucheng in sub-region 2, and 914.2 in ZhengzhouA, 1,116.6 in ZhengzhouB, 1,135.6 in Xuzhou, and 437.3 in Mengcheng in sub-region 3. (ii) The magnitude of increase in crop yield with increase in SOC stock varied among CK,UF,CF, and INM treatments for different sites across the HHH. A gradual but sustainable increase was observed through SOC-induced improvements in soil quality. (iii) The threshold value of SOC stock for sub-region 1 was 44.9 Mg ha−1 in XinjiA with the corresponding crop yield of 12.3 Mg ha−1 year−1. The available data were not sufficient to identify the threshold level of SOC stock for sub-region 2. The threshold values of SOC stock(Mg ha−1) for sub-region 3 were 27.5 in Xuzhou, and 44.6 in Mengcheng with the corresponding crop yield(Mg ha−1 year−1) of 14.5 and 10.5, respectively. (v)The threshold value of SOC stock in response to crop yield for the entire HHH ranged from 25.0 to 41.0 Mg ha−1, and the corresponding potential of increase in crop yield from 12.8 to 18.0 Mg ha−1 year−1. In comparison with a rapid yield response by application of chemical fertilizers, increase in SOC stock and improvement in soil quality result in a gradual but sustainable yield increase. Thus, restoration of the depleted SOC stock by conversion to a restorative land use and adoption of INM across the HHH can enhance soil quality and improve crop production.

Post-farming land restoration schemes exhibit higher soil aggregate stability and organic carbon: Evidence in the Three Gorges Reservoir Area, China

Integrated crop–livestock management systems (ICLS) have been increasingly recommended in Brazilian agroecosystems. However, knowledge of their effect on soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks is still limited. The study was undertaken to evaluate the effects of ICLS under two tillage and fertilization regimes on SOC and TN concentrations and stocks in the 0–30 cm soil layer, in comparison with continuous crops or pasture. The following soil management systems were studied: continuous pasture; continuous crop; 4 years’ crop followed by 4 years’ pasture and vice-versa. The adjacent native Cerrado area was used as a control. Under the rotation and continuous crop systems there were two levels of soil tillage (conventional and no-tillage) and fertility (maintenance and corrective fertility). The stock calculations were done using the equivalent soil mass approach. The land use systems had a significant effect on the concentrations of SOC and TN in the soil, but no effect was observed for the soil tillage and fertilizer regimes. For these two latter, some significant discrepancies appeared in the distribution of SOC and TN concentrations in the 0–30 cm layer. Carbon storage was 60.87 Mg ha −1 under Cerrado, and ranged from 52.21 Mg ha −1 under the ICLS rotation to 59.89 Mg ha −1 with continuous cropping. The decrease in SOC stocks was approximately 8.5 and 7.5 Mg ha −1, or 14 and 12%, for continuous pasture and ICLS respectively. No-tillage for 10 years after the conversion of conventional tillage to no-tillage under the continuous crop system, and 13 years of conventional tillage in continuous cropping did not result in significant changes in SOC stocks. The SOC and TN stocks in surface layers, using the equivalent soil mass approach rather than the equivalent depth, stress the differences induced by the calculation method. As soil compaction is the principal feature of variability of stocks determinations, the thickness should be avoid in these types of studies.

Changes in soil organic carbon and total nitrogen stocks along a chronosequence of Caragana intermedia plantations in alpine sandy land

The effect of agricultural abandonment and mountain terrace degradation on soil organic carbon in a Mediterranean landscape

Grazing exclusion has been widely used to restore the degraded alpine grasslands on the Qinghai-Tibetan Plateau (QTP). However, the dynamics of soil organic carbon (SOC) and soil total nitrogen (STN) pools after grazing exclusion and their controlling factors are currently less understood in this region. Here, a meta-analysis was conducted to quantitatively assess the changes in SOC and STN stocks in topsoil (0–30 cm) following grazing exclusion in three major grassland types (alpine meadow, alpine steppe, and alpine desert steppe) on the QTP and to explore the potential factors controlling the effects of grazing exclusion on SOC and STN stocks. The results showed that overall, grazing exclusion significantly increased SOC stock by 16.5% and STN stock by 11.2%. Significant increases in both SOC and STN stocks were observed after grazing exclusion of alpine meadow. In contrast, grazing exclusion did not improve SOC and STN stocks in the other two grassland types. The difference in mean annual precipitation among grassland types was a likely reason for the different dynamics of SOC and STN stocks after grazing exclusion. The effect sizes of both SOC and STN stocks were positively related to the duration of grazing exclusion, and a positive relationship was detected between the effect size of SOC stock and that of STN stock, demonstrating that the dynamics of SOC and STN were closely coupled during the period of grazing exclusion. However, grazing exclusion had no impact on soil C:N ratio for all grassland types, indicating that soil C:N ratio was generally stable after grazing exclusion. Therefore, it is suggested that the increase in STN can support continuous SOC accumulation following grazing exclusion. In conclusion, the findings suggest that the effects of grazing exclusion on SOC and STN stocks differ among grassland types on the QTP, and grazing exclusion of alpine meadows may provide substantial opportunities for improving SOC and STN stocks in this region.