Changes In Soil Properties Research Articles

Low-temperature treatment optimization for diesel-contaminated kaolin: Mutual impacts of generated pyrolytic carbon and particle agglomeration

Efficiency improvement in low-temperature treatment for diesel-contaminated sites is urgent because changes in soil properties and the generation of new substance during the remediation process can influence the duration and energy utilization. This paper focuses on low-temperature treatment optimization based on the mutual impacts of pyrolytic carbon and kaolin aggregation. Results reveal that the peak mass loss rate occurred between 100–150°C, with minimal loss beyond 200°C. Samples thermally treated at 150–200°C exhibited darker colors, indicating pyrolytic carbon formation, corroborated by x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and three-dimensional fluorescence spectrum (3D-EEM) analyses. Additionally, diesel contamination influenced the fractal dimension of aggregates by influencing adhesion forces (<10000 mg/kg) and forming liquid bridges (≥10000 mg/kg) in untreated kaolin, resulting in an initial increase and subsequent fall in fractal dimension with increasing concentration. Decline rates of pollutant gas concentration were closely correlated with fractal dimension changes under thermal conditions due to pollutant volatilization and pyrolytic carbon formation. Based on the consistency between fractal dimension and decline rate, two critical remediation concentrations (C0) and temperatures (T0) indices were identified to optimize the low-temperature remediation.

Effects of alpine meadow degradation on the soil physical and chemical properties in Maqu, China

While alpine meadow degradation presents a significant ecological challenge, research on the complex patterns of soil property changes induced by degradation has been somewhat limited. In this study, we investigated the Maqu alpine meadow, meticulously categorizing it into different grassland types exhibiting varying degrees of degradation based on factors such as vegetation coverage and community, soil characteristics, and landscape features. These classifications included typical grassland, degraded grassland, desertified grassland, and sandy land. In August 2018, we established three quadrats at each sample point and collected soil samples at five depths (surface [0–2 ​cm], 2–5 ​cm, 5–10 ​cm, 10–20 ​cm, and 20–40 ​cm) to analyze soil particle size distribution (PSD) and nutrients content. The results revealed a discernible trend: alpine meadow degradation led to selective loss of nutrient-rich soil fine particles, resulting in significant alterations in soil PSD and nutrients, particularly pronounced in grasslands with low degrees of degradation. Moreover, within a specific range of degradation degree, the clay content in the shallow soil of alpine meadow increased with the degradation degree, but it declined when the degradation degree exceeded a certain threshold. Degradation also disrupted the intricate relationship between soil nutrients, with notable variations in their coupling. This difference was also reflected in the influence of soil physical and chemical properties on soil nutrients, with the explanatory power of each environmental indicator on soil nutrients decreasing significantly with increasing degradation. This study systematically analyzed the variation in soil physical and chemical properties throughout the degradation process, revealing the mechanism of soil nutrient imbalance and decline caused by the degradation process. It provides crucial theoretical foundations and reference points for the preservation and rejuvenation of alpine meadows, enriching the methodology for assessing the impact of grassland degradation.

Resolving the Intricate Effects of Multiple Global Change Drivers on Root Litter Decomposition.

Plant roots represent about a quarter of global plant biomass and constitute a primary source of soil organic carbon (C). Yet, considerable uncertainty persists regarding root litter decomposition and their responses to global change factors (GCFs). Much of this uncertainty stems from a limited understanding of the multifactorial effects of GCFs and it remains unclear how these effects are mediated by litter quality, soil conditions and microbial functionality. Using complementary field decomposition and laboratory incubation approaches, we assessed the relative controls of GCF-mediated changes in root litter traits and soil and microbial properties on fine-root decomposition under warming, nitrogen (N) enrichment, and precipitation alteration. We found that warming and N enrichment accelerated fine-root decomposition by over 10%, and their combination showed an additive effect, while precipitation reduction suppressed decomposition overall by 12%, with the suppressive effect being most significant under warming-alone and N enrichment-alone conditions. Significantly, changes in litter quality played a dominant role and accelerated fine-root decomposition by 15% ~ 18% under warming and N enrichment, while changes in soil and microbial properties were predominant and reduced decomposition by 7% ~ 10% under precipitation reduction and the combined warming and N enrichment. Examining only the decomposition environment or litter properties in isolation can distort global change effects on root decomposition, underestimating precipitation reduction impacts by 38% and overstating warming and N effects by up to 73%. These findings highlight that the net impact of GCFs on root litter decomposition hinges on the interplay between GCF-modulated root decomposability and decomposition environment, as well as on the synergistic or antagonistic relationships among GCFs themselves. Our study emphasizes that integrating the legacy effects of multiple GCFs on root traits, soil conditions and microbial functionality would improve our prediction of C and nutrient cycling under interactive global change scenarios.

Effects of fire and fire-induced changes in soil properties on post-burn soil respiration

Abstract Background Boreal forests cover vast areas of land in the northern hemisphere and store large amounts of carbon (C) both aboveground and belowground. Wildfires, which are a primary ecosystem disturbance of boreal forests, affect soil C via combustion and transformation of organic matter during the fire itself and via changes in plant growth and microbial activity post-fire. Wildfire regimes in many areas of the boreal forests of North America are shifting towards more frequent and severe fires driven by changing climate. As wildfire regimes shift and the effects of fire on belowground microbial community composition are becoming clearer, there is a need to link fire-induced changes in soil properties to changes in microbial functions, such as respiration, in order to better predict the impact of future fires on C cycling. Results We used laboratory burns to simulate boreal crown fires on both organic-rich and sandy soil cores collected from Wood Buffalo National Park, Alberta, Canada, to measure the effects of burning on soil properties including pH, total C, and total nitrogen (N). We used 70-day soil incubations and two-pool exponential decay models to characterize the impacts of burning and its resulting changes in soil properties on soil respiration. Laboratory burns successfully captured a range of soil temperatures that were realistic for natural wildfire events. We found that burning increased pH and caused small decreases in C:N in organic soil. Overall, respiration per gram total (post-burn) C in burned soil cores was 16% lower than in corresponding unburned control cores, indicating that soil C lost during a burn may be partially offset by burn-induced decreases in respiration rates. Simultaneously, burning altered how remaining C cycled, causing an increase in the proportion of C represented in the modeled slow-cycling vs. fast-cycling C pool as well as an increase in fast-cycling C decomposition rates. Conclusions Together, our findings imply that C storage in boreal forests following wildfires will be driven by the combination of C losses during the fire itself as well as fire-induced changes to the soil C pool that modulate post-fire respiration rates. Moving forward, we will pair these results with soil microbial community data to understand how fire-induced changes in microbial community composition may influence respiration.

Research Progress of Desertification Control in China

Desertification is a change in soil properties, vegetation, or climate that leads to the ongoing loss of ecosystem services essential for sustaining life. Desertification affects large areas of dry land around the world and is a major cause of stress in human societies. Desertification is a serious ecological problem in China. Desertification has seriously affected vegetation growth, food security, and human economy, and has caused certain adverse effects on the natural environment and social environment. Based on the causes of desertification and the present situation of desertification, this paper analyzes various measures to prevent and control desertification and puts forward some useful ideas on desertification in China, which will provide a reference for the research of desertification control in China.

Effects of inoculation with Bacillus arenosi on physical and biochemical properties of soil, surface runoff and erosion in degraded forestlands of Northern Iran

A viable practice to improve key properties of soil, and reduce runoff generation and erosion may be inoculation with selected bacteria. However, no previous studies have evaluated whether the direct inoculation of Bacillus arenosi K64 (hereafter simply indicated as B. arenosi) to soil impacts the main physical and biochemical properties of soil as well as the runoff and erosion rates. This study has measured the infiltration rate (IR), tensile strength (TS), mean weight diameter (MWD), polysaccharides (PS) and important enzymes of soil (β-glucosidase, N-acetyl glucosaminidase, phosphatase and arylsulphatase) in degraded forest soils (Northern Iran) inoculated with B. arenosi in comparison to untreated soils (control). Moreover, the runoff coefficient and soil loss have been measured in plots with soil sampled in those sites under natural rainfalls. IR, TS and MWD increased by 65 % to 160 % in treated soils compared to the control. PS and enzymes were significantly higher (by 20 % to 200 %) after soil inoculation. A noticeable decrease in both surface runoff and soil loss (both by 45 %) in the inoculated soils resulted from those changes. High correlations between the hydrological response of soil on one side, and the measured physical and biochemical variables on the other side were observed. A derivative variable calculated by the Principal Component Analysis can be considered as a meaningful parameter to estimate the changes in soil properties and response due to inoculation with bacteria. Agglomerative Hierarchical Cluster Analysis clearly discriminated the treated from the untreated soils. This study has demonstrated that soil inoculation with B. arenosi plays a significant role in reducing runoff generation and soil erosion under the experimental conditions, thanks to the general improvement in physical and biochemical properties of soil.

STUDIES OF THE EFFECT OF REINFORCEMENT WITH GEOSYNTHETIC MATERIALS ON THE STRENGTH OF SOILS UNDER CONDITIONS OF TRIAXIAL COMPRESSION AND SINGLE-PLANE SECTION

The study is a comprehensive analysis of the effect of geosynthetic materials on the strength characteristics of soils under triaxial compression and single plane shear conditions. The triaxial compression method is used to investigate the complex effects on soil specimens, which reflects real conditions and ensures the reliability of the results.The aim of the study is to evaluate the effectiveness of geosynthetic materials as a means of soil reinforcement. Particular attention is paid to analysing changes in the mechanical properties of soils reinforced with different types of geosynthetics compared to unreinforced samples. The study includes laboratory tests, during which the parameters of strength, deformability and stability of soils under different loads and variations of test conditions are evaluated.The results of the study provide important information for specialists in geotechnical design and construction. They help to evaluate the effectiveness of geosynthetic materials in strengthening soil structures under high loads and complex conditions.Additionally, the study includes an analysis of the effect of geogrid on the strength of weak soils, which allows to identify optimal strengthening options and compare their effectiveness.Thus, the study is a relevant contribution to the development of knowledge on the interaction between geosynthetic materials and soil structures, contributes to the optimisation of design and increases the durability of soil structures

Assessment of High-Severity Post-Fire Soil Quality and Its Recovery in Dry/Warm Valley Forestlands in Southwest China through Selecting the Minimum Data Set and Soil Quality Index

Recurrent wildfires can negatively affect soil quality, and post-fire soil quality recovery is critical for maintaining sustainable ecosystem development. The objective of this study was to evaluate the changes and recovery of soil properties and soil quality in the forests of dry/warm river valleys in southwest China after disturbance by high-severity fires. In this study, the impact of fire on soil properties and soil quality was investigated for three years post-fire. Unburned forest land with a similar natural environment compared to the fire area was used as a control. Soil samples were collected from three different depths of 0–10 cm, 10–20 cm, and 20–30 cm, respectively. Principal component analysis (PCA) combined with the Norm value was used to select the minimum data set (MDS), thus calculating the soil quality index (SQI). The results showed that the soil properties changed significantly after high-severity fires. On average, soil bulk density (0.91 g/cm3, p = 0.001), total nitrogen (0.12 g/kg, p = 0.000), total phosphorus (0.10 g/kg, p = 0.000), and total potassium (5.55 g/kg, p = 0.000) were significantly lower in the burned areas than in the unburned areas at the first sampling. These indicators increased in the following three years but still did not recover to unburned levels. Compared with the above indicators, soil porosity and organic matter increased post-fire, but gradually decreased over time. Soil clay, geometric mean diameter, and total potassium were included in the MDS. The SQI was ranked as unburned &gt; 3 years &gt; 2 years &gt; 1 year &gt; 6 months. The SQI was significantly (p = 0.001) reduced six months post-fire by an average of 36%, and, after three years of recovery, the soil quality of the post-fire areas could be restored to 81% of soil in unburned areas. Apparently, high-severity fires caused changes in soil properties, thereby significantly decreasing soil quality. Soil quality gradually improved with increasing restoration time. However, the complete recovery of soil quality post-fire in forest land in the dry/warm river valley will take a longer time.

Desertification indirectly affects soil fauna by reducing complexity of soil habitats and diversity of energy sources

Soil fauna is closely linked to ecological functions such as biogeochemical cycling, soil structure, ecosystem sustainability and trophic interactions. However, little consideration has been given to how desertification influences the abundance and diversity of soil fauna in arid areas. In this study, soil fauna was sampled in four desert habitats (gravel, sand, salt and mud desert) in northwest China. At the same time, the plant traits, geographic location and soil properties were investigated. We also measured contribution of environmental factors explained faunal community diversity and abundance, and by what pathways desertification controls soil fauna. The results showed that total abundance and diversity of soil fauna in the mud desert were significantly (P < 0.05) higher than salt, sand and gravel deserts. Soil fauna diversity, composition and community were more sensitive to desertification-induced changes in soil properties than to changes in plant traits and geographic locations (changes in soil properties explained 68.9 % and 73.7 % of the variation in diversity and abundance of soil fauna community, respectively). Among them, the available phosphorus, volumetric water content had a significant positive effect on community diversity and abundance, while pH had a significant negative effect (P < 0.01). The results of piecewise structural equation modeling imply that desertification may have mainly indirect impacts on soil fauna community, and that direct effects are almost zero. In summary, regardless of the type of desertification, it will affect the material cycle, energy flow and information transfer of ecosystems by destroying the soil habitats and vegetation conditions, and will affect the structure and diversity of soil fauna from the bottom up.

Long-term stationary fertilization decreased soil health in field-grown sweetpotato by increasing soil-borne diseases or allelochemicals

Fertilization are commonly used strategies to alleviate continuous cropping obstacles, but long-term stationary fertilization also causes varying degrees of soil barriers that hinder the growth of crop with the extension of planting years. However, there was currently a lack of systematic research on which soil properties change caused by long-term stationary fertilization were the reasons for the production obstacles in sweetpotato-planting fields. Here, soil samples from a 21-year-old continuously sweetpotato-planting field covering four fertilizations (CK: no fertilizer; M: organic manure only; NPK: chemical fertilizer only; MNPK: chemical fertilizer plus organic manure) were collected and analyzed. Compared with CK, fertilization significantly increased soil microbial biomass carbon content, the activities of urease, invertase and alkaline phosphatase, and the increase amplitudes in these indicators was the largest in MNPK. Moreover, fertilization significantly decreased the relative abundance of harmful fungi (i.e., Gibberella_avenacea, Alternaria_alternata, Mortierella_alpina, etc.) compared with CK. Especially, the relative abundance of fungal pathogens, Fusarium_oxysporum and Fusarium_proliferatum, showed a trend of MNPK<M < NPK. The abundance of plant-parasites nematodes in M and NPK were higher than that of CK, while long-term application of MNPK decreased the abundance of plant-parasites nematodes compared with CK. Suggesting that fertilization, especially applied MNPK, resulted in a faster cycling of soil nutrients and, to some extent, reduced soil fungal diseases and plant-parasites nematodes abundance, which was positively related to sweetpotato yield based on RDA analysis. However, high concentration of phenolic acids (i.e., syringic acid, syringaldehyde, vanillic acid, vanillin, ferulic acid and p-coumaric acid, etc.) were still observed in MNPK. Our results demonstrated that long-term fertilization, especially MNPK, can improve soil nutrient cycling and decrease the abundance of some harmful fungi and plant-parasites nematodes, while lead to the accumulation of phenolic acids. Therefore, the potential hazards of phenolic acids derived from long-term application of MNPK in sweetpotato-planting fields were deserved further attention.

Enhanced Water Resistance of TiO2-GO-SMS-Modified Soil Composite for Use as a Repair Material in Earthen Sites.

Most earthen sites are located in open environments eroded by wind and rain, resulting in spalling and cracking caused by shrinkage due to constant water absorption and loss. Together, these issues seriously affect the stability of such sites. Gypsum-lime-modified soil offers relatively strong mechanical properties but poor water resistance. If such soil becomes damp or immersed in water, its strength is significantly reduced, making it unviable for use as a material in the preparation of earthen sites. In this study, we achieved the composite addition of a certain amount of sodium methyl silicate (SMS), titanium dioxide (TiO2), and graphene oxide (GO) into gypsum-lime-modified soil and analyzed the microstructural evolution of the composite-modified soil using characterization methods such as XRD, SEM, and EDS. A comparative study was conducted on changes in the mechanical properties of the composite-modified soil and original soil before and after immersion using water erosion, unconfined compression (UCS), and unconsolidated undrained (UU) triaxial compression tests. These analyses revealed the micro-mechanisms for improving the waterproof performance of the composite-modified soil. The results showed that the addition of SMS, TiO2, and GO did not change the crystal structure or composition of the original soil. In addition, TiO2 and GO were evenly distributed between the modified soil particles, playing a positive role in filling and stabilizing the structure of the modified soil. After being immersed in water for one hour, the original soil experienced structural instability leading to collapse. While the water absorption rate of the composite-modified soil was only 0.84%, its unconfined compressive strength was 4.88 MPa (the strength retention rate before and after immersion was as high as 93.1%), and the shear strength was 614 kPa (the strength retention rate before and after immersion was as high as 96.7%).

Changes in rill detachment capacity after deforestation and soil conservation practices in forestlands of Northern Iran

Rill erosion is particularly intense after deforestation on hillslopes with steep and long profiles. Since the rill detachment capacity (“Dc”) shows a noticeable variability resulting from different soil properties and vegetation characteristics, there is a need to explore the changes in key soil properties and rill erosion rates under different natural or planted species and a variety of soil conservation practices after deforestation. This study evaluates the changes in four key soil properties (organic carbon content, bulk density and water-stable aggregates of soil, and weight density of plant roots) and rill detachment capacity in forest sites with natural tree species as well as in areas subjected to reforestation and soil conservation treatments in comparison to deforested sites. To this aim, 2000 soil samples have been collected in forestlands of Northern Iran. Sampling was done in deforested areas (assumed as reference condition), and in forest sites 14 plant species (natural or after reforestation). Deforested samples were subjected to five soil conservation treatments (using additives or hydromulching). On all soil samples, Dc has been measured in a laboratory flume at five water flow rates (0.27 to 0.69 L/m s−1) and five soil slopes (5.9 to 31.7 %). All soil properties, when compared to the reference condition, were significantly different (between −50 % to 124 %) among the three soil conditions (natural forests, reforested soils and deforested and treated sites), the natural forests and the treated sites showing a better quality compared to planted forests. Dc was noticeably lower in all conditions (0.022 ± 0.021 kg m−2 s−1) compared to the deforested and untreated sites (0.046 ± 0.023 kg m−2 s−1). Natural and planted forests showed a similar decrease in rill erodibility (−70 to 80 %), while a much lower reduction in Dc (−36 %) was measured for the treated areas. Overall, the study demonstrates that the changes in soil properties due to plant species and soil management as well as the associated variability in rill detachment are noticeably site-specific, and greatly depend on soil conservation treatments. The results of this study may give landscape planners clear indications about the relationships between rill detachment and the associated soil properties among treated and untreated (natural or reforested) soils.

Multi-year soil response to conservation management in the Virginia Coastal Plain

In the coastal plain region of the United States, conservation agriculture practices are being implemented to improve soil health, minimize environmental impacts, and improve farm profitability. Common practices include cover cropping and conservation tillage using strip tillage, minimal tillage, or no tillage. However, the soil response to specific combinations of conservation tillage and cover crop rotations remains poorly quantified. The objective of this research was to evaluate changes in soil properties from different combinations of conservation management. Four tillage systems – conventional, strip, minimal, and no tillage – and three winter cover rotations – fallow, winter cash crop, and high-biomass cover crop – were tested in a split-plot design. Bulk density, depth to a root-restrictive layer, soil carbon concentration, soil carbon stock, field-saturated hydraulic conductivity, and yield were measured over a seven-year period. Bulk density and field-saturated hydraulic conductivity showed greater temporal variation in the strip tillage and conventional tillage practices. Depth to root-restrictive layer was consistently highest in the strip and minimal tillage treatments, which both included implements designed to alleviate subsoil compaction. Treatments that combined conservation tillage with a winter cover (i.e., cash crops or high-biomass cover crops) had greater increases in soil carbon concentrations and carbon stock. Summer cash crop yield was significantly increased following the high-biomass cover crop treatment in 2 out of the 7 years. Altogether, soil carbon showed a more consistent response to conservation management than the other soil properties, which tended to show greater variability based on the time since disturbance (e.g., tillage). Conservation management practices therefore need to be consistently applied for multiple years in order to improve soil properties such as bulk density and saturated hydraulic conductivity.

Calibration of Low-Cost Moisture Sensors in a Biochar-Amended Sandy Loam Soil with Different Salinity Levels.

With the increasing focus on irrigation management, it is crucial to consider cost-effective alternatives for soil water monitoring, such as multi-point monitoring with low-cost soil moisture sensors. This study assesses the accuracy and functionality of low-cost sensors in a sandy loam (SL) soil amended with biochar at rates of 15.6 and 31.2 tons/ha by calibrating the sensors in the presence of two nitrogen (N) and potassium (K) commercial fertilizers at three salinity levels (non/slightly/moderately) and six soil water contents. Sensors were calibrated across nine SL-soil combinations with biochar and N and K fertilizers, counting for 21 treatments. The best fit for soil water content calibration was obtained using polynomial equations, demonstrating reliability with R2 values greater than 0.98 for each case. After a second calibration, low-cost soil moisture sensors provide acceptable results concerning previous calibration, especially for non- and slightly saline treatments and at soil moisture levels lower than 0.17 cm3cm-3. The results showed that at low frequencies, biochar and salinity increase the capacitance detected by the sensors, with calibration curves deviating up to 30% from the control sandy loam soil. Due to changes in the physical and chemical properties of soil resulting from biochar amendments and the conductive properties influenced by fertilization practices, it is required to conduct specific and continuous calibrations of soil water content sensor, leading to better agricultural management decisions.

Effects of elevated temperature and treatment duration on selected index and engineering properties of lateritic soils

Lateritic soils are important to various engineering applications, especially in tropical regions, where they serve as key components in road construction, embankments, and other geotechnical structures. This study investigated the combined effects of elevated temperature and heating duration on the index and engineering properties of lateritic soils derived from two distinct parent rocks (charnockite and quartzite) in Ado-Ekiti, Nigeria. Disturbed lateritic soil samples were heated in a furnace at various temperatures (100, 200, 300, and 400 °C) for two designated durations (2 and 3 h). Standard geotechnical tests were conducted to evaluate Atterberg limits, compaction parameters, and unconfined compressive strength. The results showed that elevated temperature led to a decrease in the plastic limit, liquid limit, plasticity index, optimum moisture content (OMC), and UCS for both soils, though the extent varied between the two parent rocks. For instance, at 400 °C for 3 h, the plasticity index decreased by 47.82% for charnockite-derived soil and 55.22% for quartzite-derived soil. At the same temperature for 2 h, it decreased by 38.79% for charnockite-derived soil and 48.92% for quartzite-derived soil. Similarly, UCS decreased by 29.83% for charnockite-derived soil and 25.97% for quartzite-derived soil at 400 °C for 3 h, while at 400 °C for 2 h, UCS decreased by 21.20% for charnockite-derived soil and 23.48% for quartzite-derived soil. Conversely, maximum dry density (MDD) increased with temperature, rising by up to 20.64% for charnockite-derived soil and 14.66% for quartzite-derived soil at 400 °C for 3 h, and by 18.29% for charnockite-derived soil and 12.62% for quartzite-derived soil at 400 °C for 2 h. Longer heating durations (3 h) generally caused more pronounced changes in soil properties compared to shorter durations (2 h). For instance, OMC decreased by 13.41% for charnockite and 14.18% for quartzite at 400 °C for 3 h compared to a 2-h duration. Statistical analyses indicated that temperature had a significant influence on most properties, while the effect of heating duration was less consistent. These findings highlight the need to consider both temperature and heating duration when evaluating the engineering behavior of lateritic soils exposed to elevated temperatures. Practical implications include potential adjustments in construction practices and design parameters for road construction and embankments in regions prone to high temperatures, such as those experiencing frequent forest fires.

Significant Differences in Microbial Soil Properties, Stoichiometry and Tree Growth Occurred within 15 Years after Afforestation on Different Parent Material.

The mineralogical composition of the parent material, together with plant species and soil microorganisms, constitutes the foundational components of an ecosystem's energy cycle. Afforestation in arid-semi arid regions plays a crucial role in preventing erosion and enhancing soil quality, offering significant economic and ecological benefits. This study evaluated the effects of afforestation and different parent materials on the physicochemical and microbiological properties of soils, including microbial basal respiration (MR), as well as how these changes in soil properties after 15 years influence plant growth. For this purpose, various soil physicochemical parameters, MR, soil microbial biomass carbon (Cmic), stoichiometry (microbial quotient = Cmic/Corg = qMic and metabolic quotient = MR/Cmic = qCO2), and tree growth metrics such as height and diameter were measured. The results indicated that when the physicochemical and microbiological properties of soils from different bedrock types, along with the average values of tree growth parameters, were analyzed, afforestation areas with limestone bedrock performed better than those with andesite bedrock. Notably, sensitive microbial properties, such as Cmic, MR, and qMic, were positively influenced by afforestation. The highest values of Cmic (323 μg C g-1) and MR (1.3 CO2-C g-1 h-1) were recorded in soils derived from limestone. In contrast, the highest qCO2 was observed in the control plots of soils with andesite parent material (7.14). Considering all the measured soil properties, the samples can be ranked in the following order: limestone sample (LS) > andesite sample (AS) > limestone control (LC) > andesite control (AC). Similarly, considering measured plant growth parameters were ranked as LS > AS. As a result, the higher plant growth capacity and carbon retention of limestone soil indicate that it has high microbial biomass and microbial activity. This study emphasizes the importance of selecting suitable parent material and understanding soil properties to optimize future afforestation efforts on bare lands.

Assessment of nutrient differences in detached soil particles between cropland and revegetated abandoned land

AbstractCropland (CRL) abandonment is a worldwide phenomenon of land use change with significant impacts on agro‐ecosystems. This research attempts to deepen the analysis of the positive and negative effects arising by focusing on the changes in soil properties and the amount and composition of soil particles detached after several periods of rainfall and the resulting exported sediment that occurs in abandoned areas with natural revegetation compared to CRL. The study was carried out in an agroforestry catchment with a temperate climate, on which CRL and abandoned land with natural vegetation were compared. The soil was sampled along two representative hillslopes integrating elements of the landscape and land use/land covers. Sediments were collected after seven periods in which flood events were recorded during the period July 2016 to December 2017, using artificial‐lawn mats. Soil and sediment composition (texture, soil organic carbon [SOC] and nutrients [total nitrogen and total phosphorous]) under both land uses were assessed and compared and related to rainfall characteristics using principal component analysis. Nutrient enrichment factors in the sediments compared to soils were also evaluated. The results highlight that after abandonment, SOC increased significantly, reaching contents almost three times higher than in CRL. Consequently, soil erodibility decreased, resulting in substantially lower sediment generation after erosive rainfall events. On average, sediment generation was three times lower in abandoned areas than in CRL, despite their steeper slopes. Soil total nitrogen also increased on abandoned lands, reaching values about twice as high as those in CRL. However, total phosphorous content was almost twice as high in CRL than in abandoned land posing a potential risk for water due to higher erosion rates recorded in CRL. The results confirmed the association of phosphorous with smaller particles and also demonstrated the total phosphorous‐SOC link in abandoned land. Furthermore, the effect of rainfall intensity on phosphorous mobilisation was confirmed, whilst nitrogen losses were mainly related to the total amount of rainfall recorded. In a scenario of increasing extreme precipitation, both total amount and increased precipitation intensity may exacerbate water pollution problems following nutrient loss in cultivated areas. This research contributes to identifying the impacts on agroforestry systems within the current context of converting natural areas into cultivated land, whilst in other regions revegetated natural areas are developed from abandoned agricultural land.

Crop Residue Biochar Rather Than Manure and Straw Return Provided Short Term Synergism Among Grain Production, Carbon Sequestration, and Greenhouse Gas Emission Reduction in a Paddy Under Rice‐Wheat Rotation

ABSTRACTReturn of crop residues directly as straw, animal manure, or biochar are recommended management options for biowaste recycling and soil organic carbon (SOC) maintenance in agriculture. However, to address the soil health challenges associated with soil degradation and climate change, it is critical to determine if or which of these different forms of crop residues could deliver a synergic improvement in SOC storage, emission reduction, and crop productivity following field application. In this study, maize straw in the form of air‐dried biomass (CS), manure via cattle digestion (CM), and biochar via pyrolysis (CB) was respectively amended once at a dose of 10 t C ha−1, in comparison to no maize straw addition (CK), in a paddy field under rice‐wheat rotation. Changes in soil properties, SOC storage, greenhouse gas (GHG) emissions, and rice/wheat yield were examined over two consecutive rice/wheat rotation cycles following soil amendment. The total rice grain yield considerably increased by 6% under CM and CB, while it reduced by 6% under CS compared to CK. Soil nutrient content persistently increased under CM and CB by 4.2% ~ 17% and 11% ~ 26% for total nitrogen, 26% ~ 61% and 20% ~ 53% for available P, and 2% ~ 82% and 30% ~ 115% for available K, respectively. Topsoil SOC storage increased considerably by 8% under CM and 20% under CB, while remained unchanged under CS, compared to CK. The total methane (CH4) and nitrous oxide (N2O) emissions were considerably increased by 7 folds and 15% under CS and 3.5 folds and 61% under CM, respectively, compared to CK. In contrast, these emissions considerably decreased under CB by 33% for CH4 and 29% for N2O. Consequently, the C emission efficiency considerably reduced under CS and CM but increased under CB over the two rotation cycles monitored. Moreover, the soil quality index (SQI) considerably improved under CM and CB but remained unchanged under CS compared to CK. Among the different forms of straw return, manure, and biochar, straw amendments differed considerably in their effects on C sequestration, GHG emissions, and crop productivity. Only biochar from crop residues synergistically improved these functions in the short‐term following application to paddy soil.

Patterns of Changes in the Mechanical and Filtration Properties of Semi-Rock Soils Modified by Jet Cementation

When installing underground structures in soil layers with high groundwater filtration rates, special requirements are imposed on the material of anti-filtration curtains. The conditions of application of jet cementation technology for modification of watered fractured rocky soils of low strength in order to form a composite material with the required mechanical and filtration characteristics are considered.The technological parameters of the cementation process have been experimentally and theoretically determined to ensure the necessary radius of propagation of the bonding mixture, and methods of laboratory and field control of the modified zone have been developed. The maximum permissible values of the controlled parameters have been determined.

Changes in Soil Properties During Smoldering Fire Caused by Wildfire

Changes in Soil Properties During Smoldering Fire Caused by Wildfire