Root exudates can greatly modify microbial activity and soil organic matter (SOM) mineralization. However, the mechanism of root exudation and its stoichiometric ratio of C/N controlling upon paddy soil C mineralization are poorly understand. In this study, we used a mixture of glucose, oxalic acid, and alanine as root exudate mimics, employing three C/N stoichiometric ratios (CN6, CN10, and CN80) to explore the underlying mechanisms involved in C mineralization. The input of root exudates enhanced CO2 emission by 1.8–2.3-fold than that of the control. Artificial root exudates with low C/N ratios (CN6 and CN10) increased the metabolic quotient (qCO2) by 12% over those obtained at higher stoichiometric ratios (CN80 and C-only), suggesting a relatively high energy demand for microorganisms to acquire organic N from SOM by increasing N-hydrolase production. The stoichiometric ratios of enzymes (β-1,4-glucosidase to β-1,4-N-acetyl glucosaminidase) promoting organic C degradation compared to those involved in organic N degradation showed a significant positive correlation with qCO2; the stoichiometric ratios of microbial biomass (MBC/MBN) were positively correlated with carbon use efficiency. This suggests that root exudates with higher C/N ratios entail an undersupply of N for microorganisms, triggering the release of N-degrading extracellular enzymes. This in turn decreases SOM mineralization, implying the C/N ratio of root exudates to be a controlling factor. Our findings show that the C/N stoichiometry of root exudates controls C mineralization by the specific response of the microbial biomass through the release of C- and N-releasing extracellular enzymes to adjust for the microbial C/N ratio.

Sustainable agronomic practices are tried all over the world to promote safe and eco-friendly crop production. Therefore, in the present study, the effect of seed endophytic bacteria and its consortia on soil biochemical property, soil nutrient, and yield of chickpea (Cicer arietinum L.) under field and pot conditions are investigated. Both the experimental results proved a significant increase in total soil organic carbon (OC), electric conductivity (EC), organic matter (OM), soil nutrient like available N, P and K content and important soil enzymes like dehydrogenase (DHA), beta glucosidase, alkaline phosphate, and urease was observed under the Enterobacter hormaechei BHUJPCS-15 (T1), Enterobacter cloacae BHUJPCS-21 (T2) and combined T3 (consortia of T1 and T2) treatments. Similarly, a significant increase in the grain yield (27-45% and 57-73%) in microbial treatment was found in pot and field experiments, respectively than control. In addition, whereas the higher plant biomass (14-38% and 42-78%) was recorded in the treated plant over the control plant. Similarly, the plant photosynthetic pigment (Chl a, b, total Chl) were also increased in the microbial treated plant than the control untreated chickpea plant. Our present study highlights the significance of sustainable agronomic practices for improving the soil quality and agricultural yield while reducing adverse impacts of chemicals by the use of seed endophytic microbes and their consortia.

Sustainability of agroecosystems is the most challenging task for humans in this anthropocentric era. The faulty agriculture practices and several undesirable anthropological factors caused substantial soil erosion, desertification, and soil dryness, resulting in a severe decline in soil biodiversity and crop productivity. The mismanagement of agriculture land has deteriorated around 25% of the world’s total land area, resulting in the annual loss of approximately 24 billion tonnes of soil. By 2050, 95% world’s land might be degraded if current trends continue. The tillage practices are responsible for more than 150 t ha -1 of annual soil loss around the world. Soil erosion is responsible for 40% of all soil deterioration worldwide. Agricultural land degradation is mainly caused by intensive soil ploughing, removal or burning of crop leftovers, poor pasture management, and insufficient crop rotations. Conservation Agriculture (CA) practices are essential for soil quality restoration and improvement. The global annual adoption rate of CA has been 7 M ha year -1 over the last ten years. By decreasing soil erosion, maintaining soil structure, and encouraging soil organisms, by using CA practices, Brazil has stored around 12 million tonnes of carbon from 23.6 M ha of land. The regenerative CA practices are also important to the achievement the sustainable development goals (SDGs). This review seeks to gather and provide collective literature on the global agroecosystem situation and the impact of CA methods in restoring our degraded agroecosystems for food security.

Landslides are common in tropical and subtropical regions with hilly terrains and heavy rainstorms, which cause significant economic, ecological, and social impacts. Natural forest succession is usually slow on landslide scars due to poor soil structure and the lack of seeds of woody plant seeds, and often comes with a higher risk of repeated landslide. Ecological forest restoration has recently been suggested as an effective alternative to restore the exposed landslide scars, however, a comprehensive study to identify effective landslide restoration strategies remains lacking, particularly associated with seed treatment methods and species selection. Here we evaluated the effectiveness of different seed coating treatments of both pioneer and later successional tree species of different seed sizes on seed germination in a one-year study on three landslides in Hong Kong. Our results show that bare seeds had germination rates of 17 to 67% across all selected species (n=7). Biochar-dominant seed coating formulation boosted an additional 9.33 (SE= 0.04) in seed germination rate, while the clay-dominant seed coating formulation did not show significant effect on germination. Our results also show that medium and large-seeded non-pioneer species have significantly higher germination rates than pioneer species. These results collectively suggest that direct seeding using a biochar seed coat is a manageable and useful method to enhance tree seed germination—an essential first step to restore the forests after landslide disturbances in Hong Kong, with potential to be extended to other humid tropical and subtropical forests.

Fly ash (FA) is the 80% of coal burnt by-product of thermal power plants (TPPs), its disposal in landfills causes environmental and health issues. The amount of FA production is increasing continuously to fulfil the worldwide energy for demand, which possibly never find a practically safe method for FA dumping. Its fine particle size disperses in the air and causes air pollution and water pollution is resulted due to slurry erosion from FA dumps and contamination by leachate. Health issues and environmental concerns due to fly ash landfills/dumpsites can be prohibited by covering with phytoaccumulator plant species. Limitations of plant growth in FA includes alkaline pH, contain metals such as Cr, Cd, As, Hg and Pd, toxic level of B, pozzolanic properties of FA and lack of microbial activity. Generally, the phytoremediation process is slow therefore, to accelerate the phytoremediation process FA require organic amendments and bio-fertilizers. This article focuses on the role of naturally occurring plants in stabilization of FA dumpsite and physiochemical changes in FA. This review summarises the different holistic approaches of rehabilitations of FA landfills and also compiles how to convert FA landfills into useful landfills for bioenergy productions. Utilization of organic matter and industrial waste has been proved to provide essential nutrients for plant establishment and heavy metal accumulation. The outcomes of this learning are beneficial for classifying site-specific ecological restoration of FA landfills through holistic approach.

Mitigating soil nutrient depletion and increasing utilization efficiency is a prerequisite of sustainable agriculture. Therefore, a field experiment was carried out for 2 years in the midland agroecology of Ethiopia, to identify soil amendment types that can improved soil nitrogen (N) and phosphorus (P) balances at the same time maximize utilization efficiency and profitability under teff cultivation. Using RCBD with three replications, the soil amendments applied on the degraded acidic farmland plots were polyacrylamide (PAM = 40 kg ha−1), biochar (B = 8 t ha−1), lime (L = 4 t ha−1), gypsum (G = 5 t ha−1), PAM+B, PAM+L, PAM+G, and a control. N and P inflows from (atmospheric deposition, biological fixation, and fertilizers), and outflows by (water erosion, leaching, gaseous emissions, and harvested products) were monitored in the 24 plots via NUTrient MONitoring model. Results showed that all of the applied soil amendments improved nutrient balances (by 8–134%) compared with the control. Of the measured outflows, harvested products (43–60%) and water erosion (14–31%) were the major contributors to N depletion, followed by leaching (15–23%) and gaseous emissions (11–13%). Among the applied soil amendments, PAM+L appreciably reduced P loss from water erosion by 61% and N losses from erosion, leaching, and emissions by 55%, 10%, and 3%, respectively, and increased N use efficiency by 31% compared to control plot. Moreover, PAM+L provided a net benefit much higher compared with others. Thus, application of PAM+L would be an effective strategy to combat nutrient depletion and foster crop production in dryland agriculture.

Soil erosion is an important environmental problem that threatens human ecological security and socioeconomic development. Unreasonable land use is one of the main causes of soil erosion. By collecting the topography, climate, soil, vegetation and satellite image data of Dongzhiyuan (DZY) in the tableland and gully region (TGR) of the Loess Plateau (LP), the Revised Universal Soil Loss Equation (RUSLE) and the Chinese Soil Loss Equation (CSLE) models were used to simulate the soil erosion intensity in different periods (1987, 1997, 2007 and 2017). We found that under high rainfall erosivity factor (R), the soil erosion usually be overestimated in the RUSLE model. However, the result has been changed when we use the annual average R.Besides, the model of CSLE based on the RUSLE takes engineering measure factor (E) into account, making the results more reliable. Also, land use change will affect soil erosion. The conversion of urban to farmland and grassland will increase soil erosion, and vice versa. The mutual transfer between farmland and grassland, forest and grassland will cause soil erosion to change in different directions, and the greater of land use change, the more serious soil erosion will be. Nevertheless, we shouldn’t increase the urban land by mountain excavation and gully filling blindly. Otherwise, geological disasters such as landslides and surface subsidence may occur in the near future. This work may enhance our understanding of soil erosion mechanisms in DZY, and provide references for land use planning and soil and water conservation in China’s Loess Plateau.

The limited land is under unprecedented pressure from production, living and ecology. In order to evaluate the land pressure in the Yangtze River Delta region in 1995, 2000, 2005, 2010, 2015, and 2020 from the perspective of production, living, and ecology. This study builds a land pressure evaluation index system based on a fuzzy comprehensive evaluation model using multi-source and multi-scale data. In order to investigate trade-offs and synergies among production, living, and ecology pressures, we use the mechanical equilibrium model in physics. We then analyze land pressure model reliability and uncertainty using Monte Carlo simulations. The results show that (1) Our model can effectively reveal the level of land pressure and reflect the land pressure geographical pattern of “high in the east and low in the west, high in the south and low in the north” that characterizes the Yangtze River Delta region. (2) While living and ecology pressures are tending to rise, production pressures are tending to decrease. (3) Except for Shanghai, the trade-off areas are primarily concentrated in economically successful regions with high production and living pressure and low ecology pressure. The coordinated areas are primarily found in northern Jiangsu Province and northern Anhui Province.

Periphyton plays an indispensable role in coastal saline-alkali land, but its function is poorly understood. Soil physical and chemical properties (pH value, salinity, soil organic matter), enzyme activity and microbial diversity (based on 16s rDNA, ITS and functional genes) were measured in periphyton formed on rice-growing coastal saline-alkali soil modified by a new type of soil conditioner. The results showed that the content of organic matter and catalase activity in periphyton were significantly higher than in the unplanted control soil. Soil pH and salinity were decreased in periphyton compared to the unplanted control soil. Based on the relative abundance, bacterial genera Desulfomicrobium, Rhodobacter, cyanobacterium_scsio_T−2, Gemmatimonas, and Salinarimonas as well as fungal genus Fusarium were more abundant in periphyton than the unplanted control soil. In terms of functional genes, the cbbM and cbbL sequencing showed higher abundance of Hydrogenophaga, Rhodovulum, Magnetospira, Leptothrix, and Thiohalorhabdus, whereas the nifH sequencing indicated higher abundance of Cyanobacteria in the periphyton compared to the unplanted soil. The relative abundance and community structure of soil microorganisms were improved by periphyton, thus reducing soil salinity and pH, increasing soil organic matter and enzyme activity. This indicated that the periphyton can improve the conditions and offer a suitable environment for plant growth in coastal saline-alkali soil.

We investigated the soil physicochemical property and arbuscular mycorrhizal fungi (AMF) resilience to the degradation and deforestation of the Chilimo dry evergreen Afromontane forest (CF). Topsoil (1-10cm) physicochemical property, AMF spore abundance (SA), and AMF infectivity were determined across four land uses, viz., natural forest (NF), shrubland (ShL), cropland (CrL), and grazing land (GrL). According to the PERMANOVA and NMDS results, soil physicochemical property was resilient to degradation (NF-ShL conversation) but not deforestation (NF-CrL or NF-GrL conversions) of CF. The one-way ANOVA results indicated that most soil physicochemical variables were significantly (p<0.05) affected by land-use change. Soil organic matter and total nitrogen, in particular, reduced significantly (p<0.05) by up to 48 and 57% due to NF-CrL and NF-GrL conversion respectively. Whereas SA was found to be resilient to both CF degradation and deforestation, AMF infectivity was resilient only to NF-CrL conversion. Generally, our results did not show a similar pattern in soil physicochemical property, SA, and AMF infectivity resilience to degradation and deforestation. However, in the case of NF-GrL conversion, both soil physicochemical property and AMF infectivity exhibited significantly (p<0.05) low resilience. Based on our results, we conclude that soil physicochemical property and AMF are important factors to consider in CF restoration planning. When planting sites are either the croplands or grazing lands, soil amendment could be recommended. AMF inoculation, however, could be recommended when the planting sites are grazing lands. These recommendations may also apply widely to dry evergreen Afromontane forests restoration but additional studies are required.

The soil acidity level is a key soil characteristic that determines soil nutrient availability, soil microbial activities and crop growth. However, studies on distribution and extent of soil acidity in Ethiopia are not available. This study was carried out to predict the extent and severity of soil acidity. The study used 88,265 soil pH samples collected from soil laboratories and 21,439 samples compiled from studies. Rainfall, altitude, slope gradient, soil, and land cover were considered to generate spatial autocorrelation and integrated into geospatial analysis to predict the soil pH. The performance of the kriging model was found to be satisfactory with a standard error of 0.77, RMSE of 0.51, and R2 of 0.74. The model estimates showed that 47% and 30.2% of the country’s total area and rainfed areas were acidic (pH<6.5), respectively. Out of the total area of the country, 3.7% is found to be extremely to strongly acidic (pH<5.5), 20.7% is moderately acidic (5.6

Stopping land degradation is one of the biggest challenges worldwide and particularly in Burundi, which currently faces unprecedented rates of soil loss and food insecurity. This paper proposes a different development discourse on how to stop land degradation, and presents results and lessons learned of a bottom-up inclusive approach implemented since 2014 in Burundi: the Integrated Farm Planning approach (PIP) approach. This approach aims to build a solid foundation for sustainable change towards enhanced food production and good land stewardship, based on three foundation principles (motivation, stewardship and resilience) and three guiding principles (empowerment, integration and collaboration). Findings from an impact study on the PIP approach and testimonies of farmers from a qualitative study show profound changes in land management practices and diversity of activities on the farm, as well as in the social cohesion in households and villages. Based on a vision and a plan, nearly 80,000 motivated households are currently actively involved to stop land degradation and make their farms more productive, while in all PIP villages concrete collective action is undertaken for sustainable land stewardship. Given that these actions are widespread and come along with a change in mind-set rooted in all three foundation principles, the paper concludes that the PIP approach is able to effectively build a foundation for sustainable change. Five key lessons from this experience reveal the key elements of a different development discourse that actually motivates and mobilises farmers to stop land degradation.

Soil salinization is a serious problem leading to ecological degradation. Melia azedarach is highly salt-tolerant, and its application to saline-alkali land is a promising strategy for restoring degraded lands. In this study, we analyzed the soil properties and metabolome of M. azedarach roots grown in low- (< 3 g/kg; L), medium- (5~8 g/kg; M), and high- (> 10 g/kg; H) salinity soils to explore the amelioration effect and adaptation mechanism of M. azedarach to soils with differential salinity. Cultivation of M. azedarach was associated with a decrease in the concentration of Na + and increases in organic matter content and alkaline phosphatase and urease activities in the rhizosphere soil. The metabolome analysis revealed that a total of 382 (ESI+) and 277 (ESI-) differential metabolites (DEMs) were detected. The number of DEMs in roots rose with increased soil salinity, such as sugars and flavonoids in H vs. L, and amino acids in M vs. L. The most up-regulated DEMs were 13-S-hydroxyoctadecadienoic acid, 2’-Deoxyuridine and 20-hydroxyleukotriene B4. Combined analysis of soil properties and M. azedarach DEMs indicated that alkaline phosphatase activity was positively correlated with traumatic acid concentration. Taken together, these results indicate that M. azedarach has the potential to reduce soil salinity and enhance soil enzyme activity, and it can adapt to salt stress by regulating metabolites like sugars, amino acids, and flavonoids . This study provided a basis for understanding the mechanism underlying the adaptation of M. azedarach to saline-alkali soil and its amelioration.

Microbial biomass (MB) production and turnover strongly affect soil organic carbon (SOC) accumulation. Microbial carbon use efficiency (CUE) and MB turnover in paddy soil were determined using a novel substrate-independent H218O labeling approach and the effect of long-term fertilization with mineral (NPK) or combined (NPK+OM (manure)) amendments in 0-10, 10-20, and 20-30 cm depths were investigated. Long-term fertilization increased microbial C uptake, CUE, and growth rates, and all indexes were the highest in the NPK+OM treatment. The CUE ranged between 0.07 and 0.23 and showed variable behavior with depth: it reduced in the control treatment, indicating that more C was allocated to energy production than biomass growth, and increased in fertilized soils, showing the shift of C usage for biomass growth. The highest CUE was observed at 20-30 cm in NPK and NPK+OM and indicated that microorganisms overcome the nutrient deficiency in deep soil layers by keeping high C uptake rates at a constant CUE. MBC turnover was more rapid in NPK (10-70 d) and NPK+OM (40-65 d) compared to control (80 d) and intensified with the depth. These findings highlight that under long-term fertilization MB turnover can be controlled by CUE. These shifts in the strategies of microorganisms functioning can explain the accumulation of SOC in heavily fertilized paddy soils.

Permafrost regions are under particular pressure from climate change resulting in widespread landscape changes, which impact also freshwater chemistry. We investigated a snapshot of hydrochemistry in various freshwater environments in the lower Kolyma river basin (North-East Siberia, continuous permafrost zone) to explore the mobility of metals, metalloids and non-metals resulting from permafrost thaw. Particular attention was focused on heavy metals as contaminants potentially released from the secondary source in the permafrozen Yedoma complex. Permafrost creeks represented the Mg-Ca-Na-HCO 3-Cl-SO 4 ionic water type (with mineralisation in the range 600-800 mg/L), while permafrost ice and thermokarst lake waters were the HCO 3-Ca-Mg type. Multiple heavy metals (As, Cu, Co, Mn and Ni) showed much higher dissolved phase concentrations in permafrost creeks and ice than in Kolyma and its tributaries, and only in the permafrost samples and one Kolyma tributary have we detected dissolved Ti or Hg. In thermokarst lakes, several metal and metalloid dissolved concentrations increased with water depth (Fe, Mn, Ni and Zn - in both lakes; Al, Cu, K, Sb, Sr and Pb in either lake), reaching 1370 µg/L Cu, 4610 µg/L Mn, and 687 µg/L Zn in the bottom water layers. Permafrost-related waters were also enriched in dissolved phosphorus (up to 512 µg/L in Yedoma-fed creeks). The impact of permafrost thaw on river and lake water chemistry is a complex problem which needs to be considered both in the context of legacy permafrost shrinkage and the interference of the deepening active layer with newly deposited anthropogenic contaminants.

Biochar or pyrogenic carbon, obtained from thermo-chemical conversion of biomass in an anaerobic or oxygen limited environment has been in use in agriculture since long back to Neolithic era. Its unique soil ameliorating properties, render it suitable for environmental remediation as well as sustainable crop production. It improves soil physicochemical properties and plant nutrient availability, facilitates biodiversity, and reduces emission of greenhouse gases, thereby subsiding global warming. Application of biochar reduces soil erosion, improves soil hydrological properties, and soil microbial dynamics. It has synergistic effects on plant growth, disease-pest resistance, and crop yield per unit area and time. Due to its soil ameliorative effects, and soil and water conserving ability, it can very well be used in organic farming, pemaculture, dryland farming, conservation agriculture, and land remediation. Cheaper production cost, simple and easy pyrolytic technologies, easy availability of feedstock and bio-wastes in many developing countries and its long-term effects in soil not only build up soil carbon pool but also help support small and marginal farmers in resource-rich but economically deprived countries for sustainable agriculture and environment. In this review, efforts have been made to elucidate various methods of biochar synthesis, its characteristics and effects on soil properties, and plant growth and development, its role in sustainable agriculture and remediation of the environment.

There is currently a lack of evidence surrounding changes in the health of riparian zones under different land-use patterns within mega-reservoirs and around dams. Scientific evidence for the quantitative effects of stress indicators is vague and varies significantly among reservoirs and dams worldwide. In this study, we used a field-based approach to evaluate riparian health changes—influenced by pressure indicators—across 274 transects from three land-use areas (rural, rural–urban transitional, and urban) in the Three Gorges Dam Reservoir (TGDR) in China during 2019. Multivariate statistical techniques were applied to test for riparian zone changes under these variant land-use patterns. Our results showed that 13 pressure indicators significantly influenced 27 health indicators (including parameters for habitat, plant cover, regeneration, erosion, and exotics) of the riparian zones from the three land-use areas differently. Our results also showed that parameters for plant cover, erosion, and exotics were major contributors within the selected riparian health indicators, whereas land-use designs, farming systems, and pollutant activity variables were the pressure indicators with the strongest impact. Pearson correlation (with r ranging from -0.731 to 0.989) showed that urban transects exhibited the strongest comparative interaction, whereas rural–urban transitional transects formed the weakest association. Furthermore, the agglomerative hierarchical cluster analysis revealed similarities between rural and rural–urban transitional sites while confirming substantial dissimilarity in urban locations. These comprehensive and relevant results provide essential information for reservoir administrators to implement functional changes suited to TGDR land-use scenarios.

People’s preferences influence national priorities for economic development and ecological integrity. Often policy makers and development agents base their actions on unclear assumptions about people’s preferences. This paper explores rural citizens’ preferences for economic and ecological development goals and how they differ within and between communities. We collected data from three purposely selected communities representing dominant social-ecological systems in the transboundary Cubango-Okavango River Basin in southern Africa. We used contingent ranking survey experiments, which are a novel methodological advance in policy related research. This included a qualitative experimental design process that provided a broad framing underpinning the research. The contingent ranking itself allowed us to simultaneously assess (i) participants’ ranking priorities for the development goals; and (ii) participants’ preferences for the ordering of those goals. We found relatively strong preference homogeneity within and between communities. Economic development attributes were given high priority across all communities. At the same time, all communities expressed a high preference for a healthy river system providing stable water quality and quantity. This does not mean that our respondents prioritized nature conservation. They showed low preferences for preserving biodiversity and forests which provide less important local benefits than water. This is of high governance relevance. The results point at development domains where policy makers can most likely expect stronger buy-in from citizens. Understanding citizens’ preferences helps to better align national development priorities with what citizens want.