Restore Soil Quality Research Articles

The Impact of Ecological Restoration on Soil Quality in Humid Region Forest Habitats: A Systematic Review

Ecological restoration is widely recognized as an essential technique for addressing soil degradation, biomass decline, and biodiversity loss. Improving and maintaining soil quality is critical to ensuring environmental sustainability and successful forest recovery. This systematic review aimed to assess the impact of ecological forest restoration efforts on soil quality in humid regions, as well as to compare the effectiveness of various ecological restoration strategies on soil quality indicators. Subsequently, a systematic search on various databases (e.g., Scopus and Google Scholar) yielded 696 records, of which 28 primary studies met the inclusion criteria. The results emphasized that chemical and physical soil properties are the key indicators for assessing ecosystem performance during forest restoration. The most commonly measured parameters were soil carbon, nitrogen, phosphorus, pH, bulk density, and soil porosity. It was shown that the restoration process required a longer duration to reach a comparable level of recovery as seen in mature forests, particularly in terms of fully restoring soil quality. Additionally, it has been noted that prior land use influences the length of time needed for soil quality recovery. In planted sites, soil quality may keep improving as the site ages, though it tends to stabilize after a certain period.

Soil quality and vegetation identification in closed sand-gravel mining area in West Java, Indonesia

This paper examines the soil quality and vegetation identification in a closed sand gravel mining area in West Java, Indonesia. Revegetation of disturbed mining areas is crucial in restoring soil quality and environmental function. The native plants play a pivotal role in accelerating this process. The goal of this mixed-methods study in closed sand-gravel mining was to look at the nutrient profile, texture, and microbial count of the soil in two places in the foothills of a closed mine, as well as to find and name the plant species that naturally grow well and to find and name the plant species that naturally grow well when it rains. The observation showed that the soil near the spring was more fertile than the soil away from the spring, and the soil surrounding the spring supported a higher plant density. The study area supported the growth of 22 plants, including two trees, 13 shrubs, two sedges, four grasses, and one fern. Notably, two perennial trees–Mexican lilac and beech wood–were successfully grown during the initial greening program conducted three years ago. The bacterial and fungal counts for both soils were 109 colony-forming units (CFU) per g and 104 CFU/g, respectively. We found different morphology in the soil fungal colonies, while the bacteria colonies remained homogenous. The results underscore that the soil in the disturbed mine area still supported the native plant growth. These findings are crucial for the preservation of these native plants, making them crucial for the intensive revegetation of the mining area prior to the introduction of suitable perennial trees.

Metagenomic Insights into Coal Slag Remediation Effects on Soil and Microbial Health in Qinghai’s Muli Coal Mine

Long-term coal mining in the Muli coal mine area of Qinghai Province has degraded soil quality and reduced microbial diversity, making it imperative to implement effective ecological restoration measures to restore soil quality and enhance ecosystem functions. This study evaluated soil samples under 11 ecological restoration treatments using metagenomic sequencing combined with soil quality analysis to explore the responses of the microbial community structure and function to identify effective restoration measures. This study demonstrated that ecological restoration significantly increased the soil microbial diversity and richness, with the MLII1 (soil samples treated with a chemical weathering agent, attapulgite, and a microbial agent) and MLIII1 (soil samples treated with sheep manure (2.4 kg/m2), granular organic fertilizer (1.2 kg/m2), and the microbial agent) treatment groups performing exceptionally well. Further analysis of the functional networks revealed that although the MLII2 (soil samples treated with the chemical weathering agent and attapulgite) treatment group did not exhibit the highest species diversity, it exhibited the highest functional network complexity. The results of hierarchical clustering analysis showed that the microbial community of the MLII2 treatment group was most similar to that of the natural meadows compared to the other treatment groups. From the perspective of overall ecological restoration, this study concluded that the MLII2 treatment group exhibited the most favorable ecological restoration outcomes. This finding emphasizes the importance of not only enhancing microbial diversity but also prioritizing the restoration of community functions, especially for the recovery of fragile high-altitude ecosystems.

Effects of volatile fatty acids on soil properties, microbial communities, and volatile metabolites in wheat rhizosphere of loess

The Loess Plateau faces critical challenges due to soil degradation. In this context, using volatile fatty acids (VFAs) from biowaste as readily available soil conditioners offer promising sustainable solutions to restore soil quality and enhance agricultural productivity. The study examined how applying different VFAs as soil amendments in arid and high-salt loess soil affected wheat plant growth, soil properties, soil microbial community diversity, volatile metabolites in soil and root exudate. The non-targeted analysis was used to identify and classify 49 soil volatile organic compounds (VOCs) and 63 root exudate VOCs to seek further specific functional volatile metabolites and explore the interaction mechanisms among plants, microorganisms, and soil. The results showed that acetic acid increased soil EC by 21.0% and decreased soil organic matter by 14.4%. Propionic acid reduced soil organic matter by 14.7%. Valeric acid increased the average root diameter by 15.1%. Further analysis revealed that rhizosphere bacterial communities, but not fungal communities, showed greater sensitivity to VFAs application. Bacterial α diversity was significantly reduced in the acetic acid treatment. The main contribution of VOCs in soil with acetic acid and propionic acid applications was alcohol, and its relative percentage was 50.06% and 43.54%, respectively, which has a significantly negative correlation with the α diversity of soil bacteria. On the contrary, the content of acylamides in soil with butyric acid and valeric acid applications was higher and significantly positively correlated with the average root diameter. It was concluded that soil microbial communities respond rapidly to acetic acid, propionic acid, butyric, and valeric acid applications by adjusting the concentration of alcohols and acylamides as secondary metabolites, respectively. This study revealed the close relationship between VFAs application type and soil properties, soil microbial community diversity, soil VOCs, and root exudates VOCs. VFAs derived from biowaste will contribute to restoring loess soil quality and achieving sustainable agriculture.

Combination of plant species and water depth enhance soil quality in near-natural restoration of reclaimed wetland

Plant introduction and hydrological management are essential strategies for near-natural wetland restoration. However, the combined effects of plant species and water depth on soil quality restoration remain poorly understood. The wetland ecosystem is crucial for Earth ecosystem health and sustainable development, but it faces challenges due to environmental change and human activities leading to soil quality degradation. In this study, we conducted a five-year near-natural restoration experiment covering approximately 2071 m2 area in the Changbai Mountains region of northeastern China to assess the impact of plant species and water depth combinations on soil quality dynamics in reclaimed wetlands. Through an ecological engineering project, a meticulous controlled experiment was implemented to investigate the impact of different plant species and water depth combinations on soil quality in near-naturally restored wetlands. Over the five-year restoration period, we observed significant improvements in soil quality indicators, including pH, bulk density, soil organic carbon content, and labile organic carbon fractions. Soil pH and bulk density both showed a decreasing trend, with notable variations influenced by the combination of plant species and water depth. Particularly significant drops were observed in wetlands where Lythrum salicaria L. was introduced at 10 cm water depth and Iris wilsonii C. H. Wright was introduced at 30 cm water depth. Meanwhile, soil organic carbon content also appeared optimal restoration effects in the aforementioned combinations, highlighting the regulatory effect of these combinations on soil quality regulation. Linear regression modeling demonstrated a significant positive correlation between soil organic carbon and both above-ground and below-ground biomass, highlighting the interplay between vegetation dynamics and soil quality restoration. Our study provides valuable insights into the complex dynamics of soil quality restoration in reclaimed wetlands and underscores the importance of considering plant species-water depth combinations in restoration planning. By understanding these dynamics, restoration practitioners can make informed decisions to enhance the sustainability of wetland ecosystems and their invaluable ecological services.

Mixed planting mode is the best measure to restore soil quality in alpine mines

In ecologically fragile areas heavily affected by human disturbance, it is imperative to restore soil quality to preserve nutrient cycling and ensure ecosystem stability. However, our understanding about the underlying mechanisms of dynamic change in soil quality associated with revegetation in alpine areas remains incomplete. In this study, data from 96 plots were collected to reveal the response of soil quality to vegetation restoration in alpine mines. The soil quality index (SQI) was developed utilizing 19 measured indicators to assess differences in soil quality between various vegetation restoration modes (natural restoration (CK), planting with Elymus dahuricus (ED), Medicago sativa (MS), and multi-plant mixed (Avena fatua L. + Elymus dahuricus + Medicago sativa + Oxytropis coerulea, MM)) and restoration periods (1, 3, 4, and 6 years). A partial least squares structural equation model (PLS-SEM) was constructed to recognize the impact of 14 variables related to topographical features, plant biodiversity and community stability, aboveground plant productivity characteristics, root functional traits, and soil erosion on soil quality. The results revealed significant variations in soil quality among different vegetation restoration modes. Within the initial four years following vegetation restoration, the discernible discrepancies in SQI values were as follows: ED > MM > MS > CK; by the sixth year, the order shifted to MM > ED > MS > CK. Aboveground plant productivity characteristics and functional root traits significantly contribute to soil quality. In contrast, plant biodiversity and community stability had no significant effects on soil quality. Topographical features and soil erosion adversely affected soil quality, with soil erosion exerting the most prominent effect.

Effects of different reclamation measures on soil quality restoration in open-pit mines: A meta-analysis based on the Chinese Loess Plateau

In the Loess Plateau region, ecological restoration projects have been implemented to restore the ecological environment of open-pit mines. However, no consistent conclusion has been reached regarding the response of soil remediation efforts to different ecological measures and restoration years. A meta-analysis was performed on the results of studies published over the past 30 years for open-pit mining areas on the Loess Plateau in China. The findings reveal that land rehabilitation considerably improved soil quality in open-pit mining areas on the Loess Plateau. Different ecological measures revealed a significant variability in soil quality restoration. Specifically, forestland reclamation affected soil organic matter and microbial carbon the most. Grassland reclamation substantially influenced soil total potassium, organic carbon, enzyme activity, and microbial abundance. Plowland caused the most effective improvement in soil total nitrogen and physical properties. However, total phosphorus and pH were unaffected by restoration measures. In addition, the period of land reclamation and soil nutrients showed a high correlation in the early stage of reclamation. After long-term reclamation, a decreased rate of soil quality improvement by remediation measures occurred after the soil quality returned to its premining level. A relatively lag was observed in the response of soil microbial indicators to environmental changes, and the premining level was reached after longer-term reclamation.

Prediction of Total Petroleum Hydrocarbons and Heavy Metals in Acid Tars Using Machine Learning

Hazardous petroleum wastes are an inevitable source of environmental pollution. Leachates from these wastes could contaminate soil and potable water sources and affect human health. The management of acid tars, as a byproduct of refining and petrochemical processes, represented one of the major hazardous waste problems in Romania. Acid tars are hazardous and toxic waste and have the potential to cause pollution and environmental damage. The need for the identification, study, characterization, and subsequently either the treatment, valorization, or elimination of acid tars is determined by the fact that they also have high concentrations of hydrocarbons and heavy metals, toxic for the storage site and its neighboring residential area. When soil contamination with acid tars occurs, sustainable remediation techniques are needed to restore soil quality to a healthy production state. Therefore, it is necessary to ensure a rapid but robust characterization of the degree of contamination with hydrocarbons and heavy metals in acid tars so that appropriate techniques can then be used for treatment/remediation. The first stage in treating these acid tars is to determine its properties. This article presents a software program that uses machine learning to estimate selected properties of acid tars (pH, Total Petroleum Hydrocarbons—TPH, and heavy metals). The program uses the Automatic Machine Learning technique to determine the Machine Learning algorithm that has the lowest estimation error for the given dataset, with respect to the Mean Average Error and Root Mean Squared Error. The chosen algorithm is used further for properties estimation, using the R2 correlation coefficient as a performance criterion. The dataset used for training has 82 experimental points with continuous, unique values containing the coordinates and depth of acid tar samples and their properties. Based on an exhaustive search performed by the authors, a similar study that considers machine learning applications was not found in the literature. Further research is required because the method presented therein can be improved because it is dataset dependent, as is the case with every ML problem.

Using a soil quality index to evaluate the artificial soil quality response to rehabilitation time

External-soil spray seeding (ESSS) supplies nutrients and water to plants, soils play a pivotal role in the successful rehabilitation of rock-cut slopes. However, few studies have explored how to accurately evaluate the artificial soil quality response to rehabilitation time to determine the effectiveness of the ESSS technique. In this study, taking the rock-cut slopes of Suining Railway Station to study, various soil samples were obtained from 20-year-old, 13-year-old and 9-year-old rehabilitation slopes, where we sampled the surface soil in north- and south-facing slopes, respectively. Fifteen soil indicators were measured as potential indicators of artificial soil quality, and the indicators with significant differences between rehabilitation time considered as a total data set (TDS). Principal component analysis (PCA) and correlation matrix analysis (CMA) were used to determine a minimum data set (MDS), and these indicators within MDS were integrated into a soil quality index (SQI) by standardized scoring functions (SSF) and weighted-additive methods. Results suggested that (1) the SQI was an effective tool for evaluating artificial soil quality, (2) the longer rehabilitation time, the higher artificial soil quality, and (3) the SQI of the north-facing slopes was higher than that of the south-facing slopes in the same rehabilitation years. Nevertheless, all rehabilitation slopes had a low SQI (SQI ≤ 0.560). Overall, ESSS is a technology that can effectively promote the ecological restoration of rock-cut slopes, but there still exist a room for improvement. In the future ecological reconstruction of rock-cut slopes, more attention should be paid to the restoration of soil quality on the south-facing slopes.

Mine reclamation practices and effects of stakeholder perception — a case study of Saoner mines, Maharashtra, India

The Saoner mine reclamation study conducted in Maharashtra, India, meticulously investigates the practicality and efficacy of ecological restoration initiatives post-mining operations. Employing multifaceted research approach, including field observations, interviews, and questionnaires, the study captures a diverse array of perspectives from stakeholders representing local communities, mining companies, regulatory bodies, and environmental organizations. Within this complexity, the research uncovers spectrum of viewpoints. Encouragingly, positive outcomes emerge from specific reclamation practices like revegetation and soil stabilization. However, substantial challenges linger in vital areas such as water management, soil quality restoration, and post-reclamation monitoring, demanding targeted interventions. Stakeholders’ diverse concerns reflect varying priorities. Local communities express apprehension about the adequacy of reclamation efforts and potential health implications, underscoring immediate impact on their lives. Mining companies prioritize regulatory compliance and economic contributions, emphasizing their immediate obligations. Simultaneously, environmental organizations advocate for stringent monitoring and the adoption of more robust practices, reflecting long-term ecological perspective. The study suggests a holistic approach to mining, beyond regulatory compliance, involving integrated planning, ongoing monitoring, and stakeholder engagement. This approach can reduce the industry’s environmental footprint, promote sustainable development, and foster harmony between mining activities and local communities, making it a crucial foundation for Saoner and other Indian mining regions.

Evaluation of dredge fines material in manufactured soil blends on soil health parameters

AbstractSolutions are needed to address increasing concerns over degraded land and global food insecurity. One solution is to design soil blends that can restore soil quality and fertility. Dredge material has many soil‐like properties, which makes it a good candidate for the main component of manufactured soil blends. Questions have arisen over contaminants of concern (heavy metals and polyaromatic hydrocarbons [PAH]) in dredge fines precluding them from reuse. One approach is to remove the fine fraction of dredge to lower the contaminant concentration; however, it may result in a lower quality soil substitute for land reclamation. In this study, soil blends were designed to compare the use of whole dredge to dredge fines (e.g., dredge with silt and clay fraction) and to assess the benefits of compost material, clay, and fertilizer additions. Dredge fines blends led to increases in soil quality, dry matter growth, plant available water, total and active C, potentially mineralizable N, and micronutrients. The addition of compost material led to better soil quality for a vast majority of the tested parameters. Dredge fines were below regulatory standards for contaminants of concern (e.g., carinogenic polyaromatic hydrocarbon and heavy metals), allowing their reuse in soil blends. Removal of fines from dredge decreases the quality of soil blends and should not be removed from dredge material for use as topsoil or in topsoil blends. The 80% (v/v) dredge fines blend with 20% (v/v) additions of compost material resulted in the greatest improvements in the assessed soil health parameters.

The beneficial use of basalt flour combined to a microbial consortium to improve soil quality in basalt and carbonatic dismissed quarries

The recovery of degraded soils to restore their capacity to carry out important ecological functions such as promoting nutrient cycling is a very topical issue. The aim of the present work was to assess soil quality changes within two different disused quarries in central Italy (named Cornale and Poggio Tabor) through the addition of basalt flour combined with a microbial consortium (BBF) (2.7 kg of basalt flour and 54 ml of microbial consortium inoculum at each supply date). Soil samples were collected within 9 plots where three treatments 1) Control (C) no treatment; 2) bioactive basalt flour (BBF) and 3) bioactive basalt flour and cover crop (BBF + CC) were randomly replicated three times per quarry. Chemical indicators showed little changes due to the different amendments, conversely, the biochemical ones showed that the addition of BBF increased enzymatic activities involved in C, N, P, and S cycling, and promoted microbial growth and C mineralization activity at both studied sites. At the Cornale site in summer, the rooting of the cover crop, through the rhizodeposition provided the carbon substrates necessary to fuel the added microorganisms showing an increase in the microbial quotient of about 5 % compared to the control soil. Conversely, at the Poggio Tabor site, the peculiar geomorphology prevented the cover crop growth; therefore, the positive responses of enzymatic activities were evident only in the BBF treated plots.From a management perspective, the use of bioactive basalt flour consisting of basalt flour and microbial consortium could be a good strategy to restore soil quality according to nutrient cycling function in a degraded area. However, in highly limited organic matter conditions, an external input of organic carbon is strongly recommended to sustain the exogenous microbial consortium.

Periodic Flooding Decoupled the Relations of Soil C, N, P, and K Ecological Stoichiometry in a Coastal Shelterbelt Forest of Eastern China

Understanding the variation in soil nutrients found in coastal shelterbelt forests in response to periodic flooding is crucial for restoring the soil quality of flooded stands. In this study, we examined soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK) contents and their ecological stoichiometry, as well as soil organic matter and soil-available N, P, and K contents at three soil depths (0–10, 10–20 and 20–30 cm), in a shelterbelt forest of eastern China that was affected by periodic flooding. Results showed that soil C, N, and P contents all had a clear decreasing trend after being flooded, with significant decreases in SOC, TN and hydrolyzable N of 0–10 cm soil, as well as TP of 10–20 cm soil. Soil K content, however, had minimal changes after flooding across different soil layers. Soil C:N ratio increased significantly in 0–10 cm layer, while soil C:P, C:K, N:P, N:K, and P:K ratios decreased notably in both 0–10 cm and 20–30 cm layers following the flooding. Additionally, periodic flooding partially decoupled the correlations among SOC, TN, TP, TK and their ratios. For example, the connection between TK and N:P reversed into a negative correlation in 10–20 cm soil, while SOC and TK became negatively correlated with TP and P:K in the 20–30 cm layer. Principal component analysis revealed the effects of periodic flooding on soil C, N, P, and K availability, in which the total explained variance was decreased from 94% to 86.6%. Specifically, flooding significantly reduced the SOC and soil TN contents on the first axis, influencing C- and N-related ratios. On the second axis, flooding mainly affected soil TK content, which subsequently influenced the correlation between SOC and TK. Thus, periodic flooding notably affected the soil C, N, P, and K ecological stoichiometries of the coastal forest, but the variation patterns were depth-dependent. The insights gained from these results can contribute to the restoration of soil quality in degraded stands caused by flooding in the coastal shelterbelts regions of Eastern China.

Spatial Distribution of Soil Heavy Metal Concentrations in Road-Neighboring Areas Using UAV-Based Hyperspectral Remote Sensing and GIS Technology

Monitoring and restoring soil quality in areas neighboring roads affected by traffic activities require a thorough investigation of heavy metal concentrations. This study examines the spatial heterogeneity of copper (Cu) and chromium (Cr) concentrations in a 0.113 km² area adjacent to Jin-Long Avenue in Wuhan, China, using Unmanned Aerial Vehicle (UAV)-based hyperspectral remote sensing technology. Through this UAV-based remote sensing technology, we innovatively achieve a small-scale and fine-grained analysis of soil heavy metal pollution related with traffic activities, which represents a major contribution of this research study. In our approach, we generated 4375 spectral variates by transforming the original spectrum. To enhance result accuracy, we applied the Boruta algorithm and correlation analysis to select optimal spectral variates. We developed the retrieval model using the Gradient Boosting Decision Tree (GBDT) regression method, selected from a set of four regression methods using the LOOCV method. The resulting model yielded R-square values of 0.325 and 0.351 for Cu and Cr, respectively, providing valuable insights into the heavy metal concentrations. Based on the retrieved heavy metal concentrations from bare soil pixels (17,420 points), we analyzed the relationship between heavy metal concentrations and the perpendicular distance from the road. Additionally, we employed the universal kriging interpolation method to map heavy metal concentrations across the entire area. Our findings reveal that the concentration of heavy metals in this area exceeds background values and decreases as the distance from the road increases. This research significantly contributes to the understanding of spatial distribution characteristics and pollution caused by heavy metal concentrations resulting from traffic activities.

Restoration of soil quality of degraded grassland can be accelerated by reseeding in an arid area of Northwest China.

Grassland restoration measures control soil degradation and improve soil quality (SQ) worldwide, but there is little knowledge about the effectiveness of restoration measures affecting SQ in arid areas, and the restoration rate of degraded grasslands to natural restoration grasslands and reseeded grasslands remains unclear. To establish a soil quality index (SQI) to evaluate the effects of different grassland restoration measures on SQ, continuous grazing grassland (CG) (as a reference), grazing exclusion grassland (EX), and reseeding grassland (RS) were selected and sampled in the arid desert steppe. Two soil indicator selection methods were conducted (total data set (TDS) and minimum data set (MDS)), followed by three SQ indices (additive soil quality index (SQIa), weighted additive soil quality index (SQIw), and Nemoro soil quality index (SQIn)). The results indicated that SQ was better assessed using the SQIw (R 2=0.55) compared to SQIa and SQIn for indication differences among the treatments due to the larger coefficient of variance. The SQIw-MDS value in CG grassland was 46% and 68% lower than that of EX grassland and RS grassland, respectively. Our findings provided evidence that restoration practices of grazing exclusion and reseeding can significantly improve the SQ in the arid desert steppe, and native plant reseeded can accelerate soil quality restoration.

Arthropod Community Structure Indicating Soil Quality Recovery in the Organic Agroecosystem of Mount Ciremai National Park’s Buffer Zone

<a name="_Hlk128052096"></a><a name="_Hlk128036424"></a><span lang="EN-US">The</span><span lang="EN-US"> Mount Ciremai National Park (TNGC) buffer zone is designed to support conservation efforts. However, agriculture in this area is dominated by conventional farming that excessively uses synthetic fertilizers, which threatens soil quality. Introducing an organic fertilizer and plant growth-promoting rhizobacteria (PGPR) is expected to enhance soil quality recovery in this area. This study aimed to analyze the differences in soil arthropod communities between organic and conventional agriculture and a forest in the TNGC buffer zone to assess soil quality improvement generated by the application of the organic fertilizer and PGPR. Soil arthropods were collected with Berlese-Tullgren funnels and pitfall traps. Several associated environmental parameters, including soil pH, C-organic, temperature, and moisture, were also measured. Data were analyzed using ecological indices (i.e., richness, diversity, evenness, dominance, similarity) and soil biological quality (QBS-ar). Non-metric multidimensional scaling (NMDS) was performed to examine the relation of arthropods with environmental parameters. In total, 957 individuals of soil arthropods belonging to four classes and 15 orders were recorded. Berlese-Tullgren and pitfall traps resulted in a similar tendency in most variables, with higher richness, diversity, and evenness values in the forest, followed by organic and conventional habitats. In addition, similarity and QBS-ar indicated that forest and organic communities were more similar than conventional community. C-organic, soil moisture and pH were considered the most deciding environmental parameters for arthropod assemblages. All measured variables in this study illustrated better soil quality in organic than in conventional agriculture. This study implicates the benefit of utilizing organic fertilizers and PGPR for soil quality restoration in agroecosystems.</span>

Restoring soil quality and carbon sequestration potential of waterlogged saline land using subsurface drainage technology to achieve land degradation neutrality in India

Subsurface drainage (SSD) has been proved to be an effective technology to reclaim waterlogged saline soils. Three SSD projects were implemented in Haryana, India in 2009, 2012 and 2016 to study the long term effect of SSD (10, 7 and 3 years) operation on restoring productivity and carbon sequestration potential of degraded waterlogged saline soils under prevalent rice-wheat cropping system. These studies indicated that successful operation of SSD improved soil quality parameters such as bulk density, BD (from 1.58 to 1.52 Mg m−3), saturated hydraulic conductivity, SHC (from 3.19 to 5.07 cm day−1); electrical conductivity, ECe (from 9.72 to 2.18 dS m−1), soil organic carbon, OC (from 0.22 to 0.34 %), dehydrogenase activity, DHA (from 15.44 to 31.65 μg g−1 24 h−1), and alkaline phosphatase, ALPA (from 16.66 to 40.11 μg P-NP g−1 h−1) in upper soil surface (0–30 cm). The improved soil quality resulted in increased rice-wheat system yield (rice equivalent yield) by 328 %, 465 % and 665 % at Kahni, Siwana Mal and Jagsi sites, respectively. Studies also revealed that carbon sequestration potential of degraded land increased with the implementation of SSD projects. The principal component analysis (PCA) showed that % OC, ECe, ALPA, available N and K content were the most contributing factor for soil quality index (SQI). The overall result of the studies showed that SSD technology holds great potential to improve soil quality, increase crop productivity, farmers' income and ensure land degradation neutrality and food security in waterlogged saline areas of western Indo Gangetic Plain of India. Hence, it can be concluded that large scale adoption of SSD may fulfill the promise “No poverty, Zero hunger, and Life on land” sustainable development goals of United Nation in degraded waterlogged saline areas.

Long-term intensive management reduced the soil quality of a Carya dabieshanensis forest

The evaluation of soil quality can provide new insights into the sustainable management of forests. This study investigated the effects of three types of forest management intensities (non-management (CK), extensive management (EM), and intensive management (IM)), and five management durations (0, 3, 8, 15, and 20 years) on the soil quality of a Carya dabieshanensis forest. Further, minimum data sets (MDS) and optimized minimum data sets (OMDS) were established to evaluate the soil quality index (SQI). A total of 20 soil indicators representing its physical, chemical, and biological properties were measured for the 0–30 cm layer. Using one-way ANOVA and principal component analysis (PCA), the total data set (TDS), the minimum data set (MDS), and optimized minimum data set (OMDS) were established. The MDS and OMDS contained three (alkali hydrolyzed nitrogen (AN), soil microbial biomass nitrogen (SMBN), and pH) and four (total phosphorus (TP), soil organic carbon (SOC), AN, and bulk density (BD)) soil indicators, respectively. The SQI derived from the OMDS and TDS exhibited a stronger correlation (r = 0.94, p < 0.01), which was suitable for evaluating the soil quality of the C. dabieshanensis forest. The evaluation results revealed that the soil quality was highest during the early stage of intensive management (IM-3), and the SQI of each soil layer was 0.81 ± 0.13, 0.47 ± 0.11, and 0.38 ± 0.07, respectively. With extended management times, the degree of soil acidification increased, and the nutrient content decreased. Compared with the untreated forest land the soil pH, SOC, and TP decreased by 2.64–6.24%, 29.43–33.04%, and 43.63–47.27%, respectively, following 20 years of management, while the SQI of each soil layer decreased to 0.35 ± 0.09, 0.16 ± 0.02 and 0.12 ± 0.06, respectively. In contrast to extensive management, the soil quality deteriorated more rapidly under longer management and intensive supervision. The OMDS established in this study provides a reference for the assessment of soil quality in C. dabieshanensis forests. In addition, it is suggested that the managers of C. dabieshanensis forests should implement measures such as increasing the amount of P-rich organic fertilizer and restoring vegetation to increase soil nutrient resources for the gradual restoration of soil quality.

Cooperative Action of Fulvic Acid and Bacillus paralicheniformis Ferment in Regulating Soil Microbiota and Improving Soil Fertility and Plant Resistance to Bacterial Wilt Disease.

Excessive continuous cropping and soil degradation, such as acidification, hardening, fertility decline, and the degradation of microbial community, lead to the epidemic of soilborne diseases and cause great loss in agriculture production. Application of fulvic acid can improve the growth and yield of various crops and effectively suppress soilborne plant diseases. Bacillus paralicheniformis strain 285-3 producing poly-gamma-glutamic acid is used to remove the organic acid that can cause soil acidification and increase the fertilizer effect of fulvic acid and the effect of improving soil quality and inhibiting soilborne disease. In field experiments, the application of fulvic acid and Bacillus paralicheniformis ferment effectively reduced the incidence of bacterial wilt disease and improved soil fertility. Both fulvic acid powder and B. paralicheniformis ferment improved soil microbial diversity and increased the complexity and stability of the microbial network. For B. paralicheniformis ferment, the molecular weight of poly-gamma-glutamic acid became smaller after heating, which could better improve the soil microbial community and network structure. In fulvic acid and B. paralicheniformis ferment-treated soils, the synergistic interaction between microorganisms increased and the number of keystone microorganisms increased, which included antagonistic bacteria and plant growth-promoting bacteria. Changes in the microbial community and network structure were the main reason for the reduced incidence of bacterial wilt disease. Application of fulvic acid and Bacillus paralicheniformis ferment improved soil physicochemical properties and effectively controlled bacterial wilt disease by changing microbial community and network structure and enriching antagonistic and beneficial bacteria. IMPORTANCE Continuous cropping tobacco has led to soil degradation and caused soilborne bacterial wilt disease. Fulvic acid as a biostimulator was applied to restore soil and control bacterial wilt disease. For improving its effect, fulvic acid was fermented with Bacillus paralicheniformis strain 285-3 producing poly-gamma-glutamic acid. Fulvic acid and B. paralicheniformis ferment inhibited bacterial wilt disease, improved soil quality, enriched beneficial bacteria, and increased microbial diversity and microbial network complexity. Some keystone microorganisms in fulvic acid and B. paralicheniformis ferment-treated soils had potential antimicrobial activity and plant growth-promoting attributes. Fulvic acid and B. paralicheniformis 285-3 ferment could be used to restore soil quality and microbiota and control bacterial wilt disease. This study found new biomaterial to control soilborne bacterial disease by combining fulvic acid and poly-gamma-glutamic acid application.

Scattered wild pistachio trees profoundly modify soil quality in semi-arid woodlands

Scattered wild pistachio trees (Pistacia atlantica Dest.) support various ecological functions and services, including soil conservation, in semi-arid woodlands of the Irano-Turanian zone, but over-exploitation puts the populations at risk. The current paucity of information precludes a thorough assessment of the effect of wild pistachio trees on soil quality. Therefore, we quantified their role in soil quality of semi-arid woodlands dominated by a Pistachio-Amygdalus community. At three sites in the southern Irano-Turanian zone, we contrasted moisture, pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (TN) and nutrient concentrations of bare soil with below-crown soil. In addition, we examined soil microbial respiration (Rmic), substrate-induced respiration (SIR), microbial biomass carbon (Cmic) and nitrification potential to evaluate the influence of pistachio trees on soil microbial activity. Soil pH and C/N ratio were similar between bare and below-crown soils but significantly greater soil moisture (+41 %), EC (+13 %), SOC (+82 %) and TN (+75 %) were observed below pistachio crowns. Most soil nutrients were more abundant beneath tree crowns, especially zinc and manganese. Soil microbial activity was greater below crowns compared to bare soil as evidenced by significantly elevated Rmic (+11 %), SIR (+86 %), Cmic (+61 %) and nitrification potential (+49 %). SOC-normalization of microbial variables revealed that a SOC-driven increase in Cmic was largely responsible for the enhanced soil microbial activity below crowns. Microbial communities in bare soil showed a higher metabolic quotient (Rmic/Cmic) than in below-crown soil, suggesting low microbial efficiency and higher metabolic costs. Our findings indicate that the soils below wild pistachio crowns represent fertility islands, where soil quality and microbial activity are supported by an increased supply of organic matter and more favourable soil moisture conditions. The few woodlands that have remained relatively intact in this area urgently require conservation action while restoration planting of wild pistachio trees in degraded areas may help restore soil quality.