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Summary: Green soybean (edamame), an early-harvested soybean, is a popular vegetable in Asia and is recognised as a healthy vegetable in the other parts of the world. In Japan, edamame yield has gradually decreased over the last 30 years, despite similar cultivation areas. Damage caused by the soybean cyst nematode (SCN), Heterodera glycines , is one of the main causes. We surveyed the distribution of SCN in different locations and found a wide distribution of SCN across Japan. Different control measures are available, such as chemical control using fumigants or a granular type of nematicide, solarisation, and rotation with non-host crops. We are developing a new type of biological control method, which comprises short-term field cultivation and soil incorporation of mung bean. This method not only decreases the SCN density in soil but also mitigates soil erosion and nitrate leaching. For future SCN control it is essential to establish an environmentally friendly management strategy. [ABSTRACT FROM AUTHOR]

Unregulated trampling in natural and urban forests compacts the soil, and the plants suffer. In an urban forest in Moscow, soil bulk density in heavily trampled sites increases significantly: 1.6–1.8 g/cm3 compared with 0.6–0.7 g/cm3 on sites under negligible human pressure. As soil density increases, heavy metals and their mobile fractions accumulate in the soil and roots. Amongst forest species capable of loosening soil and thereby improving its physicochemical properties, larch has the lowest soil density (0.42–0.57 g/cm−3) and appears to reduce the toxicity of heavy metals in forest and forest park landscapes. [ABSTRACT FROM AUTHOR]

Exogenous nitrogen addition can alter plant growth and community structure, thereby influencing soil carbon and nitrogen storage and ultimately impacting ecosystem services and functions. Previous studies have primarily focused on the effects of biological or abiotic factors on soil carbon and nitrogen storage in alpine meadows, but there is a lack of research investigating changes in soil organic carbon and total nitrogen storage as well as their controlling factors under nitrogen addition. Therefore, this study examined soil organic carbon and nitrogen storage across four levels of nitrogen addition. The results showed that nitrogen input significantly increased soil organic carbon and total nitrogen storage. Soil total nitrogen storage was positively influenced by soil total nitrogen, graminoid importance value, soil available nitrogen, and plant belowground biomass, while it was negatively affected by soil bulk density. Soil carbon storage was positively affected by soil organic carbon and soil nitrate nitrogen, and negatively affected by soil bulk density and forb importance value. This study emphasizes the positive effects of nitrogen addition on the accumulation of soil organic carbon and total nitrogen storage and highlights the combined effects of plant traits and soil physicochemical properties on soil total nitrogen storage. [ABSTRACT FROM AUTHOR]

In semi-arid savanna grasslands, the sparse distribution of trees often forms what are commonly known as fertile islands. However, the effect of these trees on soil organic carbon (SOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC), remains poorly understood. In this study, the spatial distribution patterns of SOC, MBC, and DOC were investigated across soil profiles (0–5, 5–10, 10–30, 30–50, and 50–100 cm) at three distances from the tree trunk in an elm-dominated savanna ecosystem in Northeast China. Our results suggest that SOC, MBC, and DOC were significantly influenced by both the distance from the tree and the soil depth. The research provides evidence that elm trees can form fertile island effects, thereby enhancing the contents of SOC and labile organic carbon fractions. [ABSTRACT FROM AUTHOR]

The critical bed-shear stress (cbs) for erosion of mud–sand bed mixtures was studied in laboratory and field conditions with currents, waves, and combined currents and waves. Three types of erosion were distinguished: particle/floc erosion, surface erosion, and mass erosion. Important influencing parameters were found to be sediment composition (percentage clay, silt, and sand), presence of organic and carbonate materials, type of bed (homogeneous, remolded, layered by depositional processes), and the dry bulk density (consolidation stage). The laboratory and field results reveal that the critical bed-shear stress is not much influenced by cohesive effects if the percentage of fines (<63 μm) is smaller than approximately 15%. For pfines>15% up to approximately 50%, the critical bed-shear stress increases for increasing values of pfines but decreases again for pfines>50%. The fine fraction includes the clay fraction (pclay≅0.2 to 0.4 pfines), which contributes primarily to the cohesive effects. In addition, the bulk density depending on the soil composition (clay, silt, sand content, and consolidation stage) has a strong effect on the cbs for surface erosion. Small bed irregularities (local disturbances) also play an important role by creating local accelerations and decelerations with enhanced turbulence and initiating particle movements. A new empirical relation is suggested to predict the critical bed-shear stress for erosion based on the dry bulk density of the sediment samples. This relation is successfully applied in a morphodynamic model of a schematized tidal basin to represent spatial variations in the erodibility of fines between sandy channels and (relatively) muddy shoals. [ABSTRACT FROM AUTHOR]

The present study explores the influence of silt content on the undrained monotonic behavior of compacted tuff. All undrained triaxial tests were performed at both relative densities Dr = 50 and 90% and compacted with the optimum water content on tuff soil mixed with silt in the range of 0 to 50%. Experimental results show that adding fines content (FC) up to 20% increases the resistance of dense compacted tuff (Dr = 90%) by about 35% for 100 kPa of confining pressure, and the addition of 10% silt fines results in a maximum increase of 15.71% in the medium dense state specimen (Dr = 50%). The deviator stress reveals a decrease by adding more than 20% of silt. Moreover, the soil cohesion was found to attain maximum values with the optimum silt percentage of FC = 10% for medium-density samples (Dr = 50%) and FC = 20% for dense samples (Dr = 90%), respectively. Finally, the study showed a direct correlation between the cohesion of the soil prepared in a dense state (Dr = 90%) and the soil's maximum dry density (MDD). In particular, the maximum dry density corresponds to a higher cohesion. [ABSTRACT FROM AUTHOR]

[Objective] Amending soil with biochar and crop straw is an effective technique to improve soil quality and agricultural productivity. This paper investigates the long-term impact of continuous application of straw and biochar on soil aggregation and soil organic carbon (SOC) content in fluvo-aquic soil. [Method] A four-year (2019--2023) experiment was conducted in a winter wheat and summer maize rotation system in the western Shandong Plain. Biochar and maize straw were applied annually at the start of the winter wheat season. Straw was applied at rates of 3.80 (S0.5), 7.60 (S1.0), 11.40 (S1.5), and 15.20 t/hm2 (S2.0), while biochar was applied at rates of 1.14 (B0.5), 2.28 (B1.0), 3.42 (B1.5), and 4.56 t/hm2 (B2.0). The control treatment (CK) involved no soil amendment. After four years, we measured the changes in soil bulk density, aggregate stability, and SOC content in the 0-10 cm and 10-20 cm soil layers. [Result] Both straw and biochar applications reduced soil bulk density. The soil bulk density in the 0-10 cm soil layer under B2.0 treatment and in the 10-20 cm soil layer under B1.5 treatment decreased the most compared with the corresponding soil layers of CK, with significant reductions of 9.08% and 7.97%, respectively. Both of the two straw returning methods promoted the increase of soil aggregate to a certain extent, and the improvement effect was best for >5 mm soil aggregate, and worst for 1-2 mm soil aggregate. Compared with CK, the aggregate volume of >5 mm granular soil treated with B1.0 in 0-10 cm soil layer increased the most significantly by 107.35%, and that of >5 mm granular soil treated with S1.5 in 10-20 cm soil layer increased the most significantly by 106.63%.Except for SOC content in aggregates < 0.25 mm in the 0-10 cm soil layer under S15.5 and aggregates of 1-2 mm in the 10-20 cm soil layer under B0.5, where SOC content decreased, biochar and straw application significantly increased SOC content in all other aggregate fractions and treatments. SOC content increased with the increase in biochar and straw application. [Conclusion] Annual applications of maize straw and biochar during the winter wheat season effectively improved soil quality by reducing bulk density, enhancing water-stable aggregates, and increasing SOC content in fluvo-aquic soil. For all treatments we compared, our results showed that applying 3.42-4.56 t/hm² of biochar is most effective for improving soil quality in the studied region. [ABSTRACT FROM AUTHOR]

The uranium mines both developed and abandoned appear to be one of the most significant sources of radon exhalation in the world. Therefore, the study of radon exposure of the population in the areas around rehabilitated uranium mines is very important. This article presents the results of the radon release studies at the rehabilitated Beshtaugorsky uranium mine site, which is now used by local people for hiking and picnicking. A dose assessment is also provided. The following parameters were measured: (i) radon flux density from the soil by the open charcoal chamber method using the beta radiometer "Camera-01"; (ii) concentration of radon and its progeny in the air using the radiometer "Alpha-AERO" based on a semiconductor detector; (iii) radon in groundwater by accumulation of radon in charcoal using the "Camera-01" equipment; (iv) content of natural radionuclides in soils and rocks by NaI(Tl) spectrometry; and (v) gamma dose rate using the Geiger-Muller counter. Measurements were taken at 38 points along the Beshtaugorskaya ring road, as well as at the mouths of abandoned adits. The measurements showed significant radon release at the mouths of the former adits and in some sections of tectonic faults. In our opinion, the abnormal radon release is due to convective thermally induced air convection in permeable zones of the mountain massif; radon transport by groundwater does not affect surface radon emissions. The most important source of radiation risk is the incompletely sealed mine openings, which periodically blow out radon-enriched air. In places around the mouth of these mines, the equivalent equilibrium concentration of radon progeny in the open air reaches 35,000–45,000 Bq/m3, and the gamma dose rate also exceeds 10 µSv/h, which is more than 30 times the permissible level. A person resting for 4 h in such an area may, in the worst case, receive a dose of more than 2 mSv. It is advisable to implement measures to prevent or reduce the time people spend in the area around the former mine openings. [ABSTRACT FROM AUTHOR]

Rotational grazing (RG) could be a valid alternative to continuous grazing (CG) in Mediterranean extensive pastures to fight land degradation. This study aimed to compare soil quality under RG and CG management, in paired RG-CG Portuguese pasture areas under strong aridity stress, with RG sites converted from CG management in 2018. Soils were sampled in 2022, at 10 cm depth, over 71 ha of RG and 37 ha of CG pastures, subdivided in 16 and 10 sampling plots, respectively. In each plot, five soil samples were taken to provide one composite sample. Physico-chemical and microbial indicators of soil quality were measured immediately after. Principal Component Analysis (PCA) and Redundancy analysis (RDA) showed a clear separation between RG and CG sites with significantly higher level of soil organic carbon (27%–67%), total nitrogen (67%–77%), cation exchange capacity (9%–36%), and, at a minor extent, water holding capacity (6%–17%), in the RG plots respect to CG plots. No significant difference was found for soil bulk density, microbial and fungal biomass and microbial diversity between sites with different management, although the latter was positively correlated with CG sites in the RDA analysis. Soil organic carbon was significantly correlated to the most relevant physico-chemical parameters for nutrient cycling and water balance and to microbial fungal biomass and N-mineralization, confirming the central role of soil organic carbon for soil health. Results support RG management as an effective choice to improve soil quality in areas under desertification risk. • Soil quality of pastures under rotational grazing (RG) and conventional grazing (CG) was compared. • Higher soil organic carbon, total nitrogen, cation exchange capacity and water holding capacity was measured under RG • No significant management effect was observed on soil microbial biomass, fungal biomass and bacterial diversity. • Microbial activities, respiration and N-mineralization were influenced both by management and site specific conditions. [ABSTRACT FROM AUTHOR]

• Field N 2 O flux can be both explained by various bulk soil and structure properties. • Thresholds for structure properties are proposed beyond which N 2 O flux can be high. • Gas diffusivity is a relevant soil structure parameter to describe field N 2 O flux. Nitrous oxide (N 2 O) emissions from soil are partly controlled by aeration and gas transfer in soil, and thus by soil structure. The intensity of N 2 O emissions is usually expressed according to the water filled pore space (WFPS), calculated using the soil bulk density. These factors, even if they describe the soil structure and the water proportion in the porous network, do not inform about porous network characteristics among scales and their connectivity. The aim of this work was therefore to determine (1) to what extent the soil structure of an agricultural soil controlled N 2 O emissions during a snap-shot campaign and (2) which metric of gas transfer or soil structure was the most appropriate to describe the N 2 O emission variability at field scale. N 2 O emissions were measured with a mobile chamber on a maize crop after fertilization with several soil management practices resulting in four soil states (strip-till versus tillage, compacted soil versus uncompacted) with contrasting soil structure. Soil cylinders and bulk soil were sampled from 24 plots exhibiting a strong gradient in N 2 O emissions. Classical soil physical and chemical properties were measured, including soil bulk density and water filled pore space. Soil structure also was characterized quantitatively by X-ray tomography at meso and macro scales, and indirectly by gas transfer parameters. Clear differences were observed between low and high emission plots in terms of soil structure, soil temperature and nitrate concentration. However, soil structure appeared more strongly connected to N 2 O emissions, and some thresholds on soil structural indicators were relevant to disentangle high and low N 2 O fluxes. Some structural indicators at both scales (e.g. porosity, surface density) and gas transfer parameters (relative gas diffusivity, air permeability) were good descriptors of the observed N 2 O fluxes. Nevertheless, the gas transfer parameters can be easily measured over a short period of time, whereas the soil structure indicators determined from 3D images require an acquisition and a processing phase that can be time consuming. A good compromise to evaluate the field N 2 O flux potential from an easy measure would be to evaluate the relative gas diffusivity, which directly controls the diffusion of oxygen in soil and thereby the microbial processes of N 2 O production. [ABSTRACT FROM AUTHOR]

• Grazing reduced topmost while maintaining subsurface SOC stability. • Grazing weakened topmost SOC protections by altering biotic and soil variables. • Subsurface SOC physical and mineral protection were driven by soil microbes. • Physical and mineral protection jointly drove SOC stability at topmost soil layer. • Mineral protection governed SOC stability in the subsurface soil. Conventional grazing with high grazing pressure can decrease soil organic carbon (SOC) stability by disrupting its protective mechanisms, eliciting soil depth-dependent responses. Grazing exclusion for hay-making by mowing is usually adopted to restore grassland. However, there is still a lack of systematic evaluation of SOC stability and its impact factors in different soil layers when mowing replaces conventional grazing. Here, based on an investigation of 15 paired sites from mowing vs. conventional grazing in a temperate grassland of northeast China, we found that mowing increased mean weight diameter of soil aggregates (MWD, 5.14 %), Fe/Al associated organic carbon (Fe/Al-OC, 12.20 %), and SOC stability (11.46 %) at topmost soil layer (0–10 cm) but only increased MWD (8.50 %) at subsurface soil (10–30 cm). Mowing increased root biomass of plant variables, soil bulk density and pH of soil properties, and microbial biomass carbon (MBC) of microbial properties at the topmost layer, collectively contributing to SOC protection. However, the reduction in soil nitrate nitrogen and increasing MBC induced by mowing drove the subsurface SOC protection. The protection mechanism for SOC stability shifted from a single physical protection dominance in mowing areas to joint physical and mineral protection in conventional grazing grasslands at the topmost depth. In contrast, subsurface SOC stability was consistently governed by mineral protection regardless of grazing. Our results imply that although grassland ecosystems can initiate more protection mechanisms to cope with disturbances, mowing induced the increase of physical and mineral protection resulting from the substantial promotion in plant C input quantity and microbial biomass, combined with alteration in soil properties, finally stabilized topmost SOC. The limited impact of management practices on the subsurface SOC stability indicates that the interaction of subsurface soil and microbial properties with SOC protection should be fully considered to forecast soil C dynamics and its resistance to disturbance accurately. [ABSTRACT FROM AUTHOR]

Tillage and reseeding are recognized as effective near-natural restoration practices for degraded grasslands. Despite of ecological restoration efforts of these practices on degraded saline-alkali grasslands in the semi-arid Songnen Plain, the focus on soil functions, particularly carbon (C) accumulation, remains inadequate. This study implemented four restoration measures—tillage (T), tillage combined with Astragalus adsurgens reseeding (TR), no-tillage and reseeding (NR), and no-tillage (N)—on degraded saline-alkali grasslands in 2017. We investigated changes in plant community characteristics and species diversity, soil physical and chemical properties, and soil organic carbon (SOC) pool in 2019 (third-year post-restoration) and 2022 (sixth-year post-restoration). The results indicate that TR had the highest coverage, above-ground biomass (AGB), and below-ground biomass (BGB) in both surveys. From 2019 to 2022, NR exhibited the most pronounced increase in coverage, whereas AGB and BGB of TR achieved the largest increment. In terms of soil properties, the TR and T treatments decreased soil total nitrogen (SN) content and soil bulk density (SBD), and the TR and NR treatments decreased pH and EC. Although SOC content and storage (TSOC) values were lower in T and TR treatments in 2019, a compensation effect with highest C accumulation rate in TR was observed in 2022. Regression analysis showed significant positive correlations between TSOC and plant community height, coverage, AGB, species richness, and SN and soil phosphorus (SP) content. Structural equation models (SEMs) further indicated that tillage practices negatively impacted TSOC. In contrast, legume reseeding, through adjustments in plant density, positively impacted TSOC, with SWC playing a pivotal role. This study quantifies the impact of tillage combined with reseeding on SOC sequestration and provides critical scientific evidence for managing the natural-based restored grasslands in semi-arid regions. • Reseeding combined with tillage practice increased plant coverage, AGB and BGB. • Tillage decreased SN content and SBD, while legume reseeding decreased pH and EC. • TSOC was related with plant community height, coverage, AGB, richness, SN, and SP. • Legume reseeding had a compensatory effect on SOC loss under tillage management. • Reseeding impacted TSOC through plant density, with SWC playing a pivotal role. [ABSTRACT FROM AUTHOR]

The Grain for Green Program (GGP) is an ecological protection plan launched by China. In this context, much cultivated land in Southwest China Karst has been converted into bamboo forest to balance both ecological and economic benefits. This study selected typical areas in southern Sichuan Province and used natural bamboo forests (CK) as controls to analyze the changes in soil carbon sequestration and water retention capacity of bamboo forests with different restoration periods. The results showed that there was no significant change in soil mechanical composition during forest restoration. The soil bulk density (BD) showed a decreasing trend overall with the restoration period. The total porosity (P t) and capillary porosity (P c) showed a trend of first decreasing and then increasing with the increase of restoration years, while no obvious change pattern was found in non-capillary porosity (P o). The variation characteristics of water retention capacity are similar to porosity, and returning farmland for 5 years can achieve good water retention performance, even higher than CK. The total organic carbon (TOC) and labile organic carbon (LOC) in the soil of bamboo forests after 20 years of returning farmland were significantly higher than those in 5 and 10 years of bamboo forests, and their organic carbon content was close to that of CK. It is worth noting that the soil organic carbon activity reached its optimal state after 10 years of returning farmland. To sum up, the implementation of the project of returning farmland to bamboo can effectively improve the soil carbon sequestration and water retention capacity. The research results provide a scientific basis for the optimization of the measures of the GGP, and help to promote the sustainable development in Southwest China Karst. [ABSTRACT FROM AUTHOR]

The formation of discontinuities within soil masses due to arching phenomena is a critical issue in geotechnical engineering, profoundly influencing the stability and integrity of underground structures. This study investigated the microscopic mechanisms and associated stress redistribution in the soil mass above an actively moving trapdoor. Utilizing the Discrete Element Method (DEM) model, the influence of varying initial soil packing densities on the induced arching phenomena is examined concerning the soil displacement mechanism and shearing configuration: transfer from inner triangular to vertical bands is observed in dense soil while only vertical shearing bands are observed in initially loose soil. To account for principal stress trajectories under differing initial density conditions, an analytical model was developed to quantify the variations in soil stress. The findings reveal a noteworthy impact of the initial soil void ratio e , on the pattern evolution and stress redistribution of soil arching, manifesting a passive stress limit coefficient, K p , in denser soils along the central line above the trapdoor. The analytical model demonstrates robust agreement with both numerical and experimental data in soil loosening stress distribution and the load–displacement response of the trapdoor. [ABSTRACT FROM AUTHOR]

Transforming arid and semi-arid deserts into farmlands significantly alters soil moisture and fertility, affecting the trophic structure and functionality of soil fauna. Diversity and function of soil macrofaunal community can accurately reflect changes in soil quality and health during the succession of oasis farmlands. In this study, the assemblage of soil macrofauna and soil environmental factors in cultivated and abandoned croplands in the Zhangye Oasis of Gansu Province, were investigated using a hand-sorting method, and we analyzed the relationship between the trophic structure of soil macrofauna and the soil environment. Our results showed that: 1) Farmland cultivation increased the soil water content, soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP), while reducing pH. 2) The density, taxon richness, and Shannon-Wiener index of soil macrofauna in cultivated croplands were higher than in abandoned croplands, increasing with cultivation duration. The density of soil macrofauna in 100-year-old farmlands was 2.5, 1.5 and 1.4 times of that in 10-year-old, 30-year-old and 50-year-old farmlands; 3) the density and taxon richness of predatory, phytophagous, and other feeding types of soil macrofauna in cultivated croplands were higher than those of abandoned croplands. The observed increases in density and taxon richness are likely due to the improved soil conditions resulting from cultivation practices. The density-based ratio of predatory to phytophagous and other feeding types of soil macrofauna initially increases then decreases, inversely related to cultivation age. 4) changes in soil environment had little effect on the predatory soil macrofaunal community, and the explained variance by SOC, TP, and pH indicates the significant influence of these soil properties on the composition of the phytophagous soil macrofaunal community. SOC, TP, and pH explained 7.3 % of the variation in phytophagous soil macrofaunal community, while TN, TP, and pH explained 15.4 % of the variation in other feeding types of soil macrofauna. In conclusion, our findings highlight the positive impact of oasis farmland cultivation on soil quality and the enhancement of soil macrofauna diversity, which in turn could contribute to the resilience and productivity of these agricultural ecosystems. • The density and taxon richness of soil macrofauna in cultivated croplands were higher than in abandoned croplands. • The ratio of predatory to phytophagous soil macrofauna in abandoned croplands is lower than that in the cultivated farmlands. • Soil environmental factors have little effect on predatory soil macrofaunal communities but significantly influence the phytophagy and other feeding types. [ABSTRACT FROM AUTHOR]