Effects of silicate stabilizers on cadmium reduction and the quality of rice grains in acidic paddy soil.

Silicate has been proven to be highly-effective at immobilizing soil heavy metals, but the effects of silicate stabilizers on rice grain cadmium (Cd) reduction and rice quality under field conditions are not clear. In this study, a field experiment was conducted over three consecutive years was conducted to examine the Cd reduction in rice grains and to reveal the potential effects of silicate stabilizers on rice grain nutrients, by setting different amounts of bentonite (B), silica‒calcium fertilizer (SC) and zeolite powder (ZP). The results revealed that the application of the B, SC and ZP significantly decreased the soil CaCl2‒Cd concentration (> 39%) and significantly reduced the grain Cd concentration in both early rice (> 70%) and late rice (> 18%) under field conditions; the silicate stabilizers reduced the soil available iron (Fe) but did not limit rice grain Fe nutrition. Additionally, the three silicates promoted rice yield and improved the rice grain Ca and Mg contents; and the application of B increased the amylose concentration of the late rice grains. In conclusion, high amounts of silicate stabilizers did not adversely influence the soil conventional nutrient indices, rice minerals or rice taste, but changes in rice selenium content need attention. Overall, in comparison with lime, silicate stabilizers can improve not only the safety of rice but also the nutritional and taste qualities of rice and are more eco-friendly for long-term use in soil.

Plants Restoration Drives the Gobi Soil Microbial Diversity for Improving Soil Quality.

Desertification and salt stress are major causes of terrestrial ecosystem loss worldwide, and the Gobi, representing a salt-stressed area in inland China, has a major impact on the ecosystems and biodiversity of its surrounding environment. The restoration of the Gobi Desert is an important way to control its expansion, but there are few studies on the evaluation of restoration. In this study, soils under different restoration scenarios, namely, soils in restored areas (R1, R2), semi-restored areas (SR1, SR2), and unrestored control areas (C1, C2), were used to investigate differences in microbial diversity and physicochemical properties. The results showed that the soil was mainly dominated by particles of 4-63 µm (26.45-37.94%) and >63 µm (57.95-72.87%). Across the different restoration levels, the soil pH (7.96-8.43) remained basically unchanged, salinity decreased from 9.23-2.26 to 0.24-0.25, and water content remained constant (10.98-12.27%) except for one restored sample in which it was higher (22.32%). The effective Al, Cu, and Zn in the soil increased, but only slightly. Total organic matter (TOM) decreased from 3.86-5.20% to 1.31-1.47%, and total organic nitrogen (TON) decreased from 0.03-0.06% to 0.01-0.02%, but the difference in total organic carbon (TOC) was not significant. High-throughput testing revealed that the bacterial population of the restored area was dominated by A4b (6.33-9.18%), MND1 (4.94-7.39%), and Vicinamibacteraceae (7.04-7.39%). Regarding archaea, samples from the restored areas were dominated by Marine Group II (76.17-81.49%) and Candidatus Nitrososphaera (6.07-9.75%). PCoA showed that the different restoration levels were the main cause of the differences between the samples. Additionally, salinity was the dominant factor that induced this difference, but it was inhibited by the restoration and targeted enrichment of some of these functional genera. Desert restoration should therefore focus on conserving water rather than adding nutrients. Planting salt- and drought-tolerant vegetation will contribute to the initial restoration of the desert and the restoration of the microbiological content of the soil as it migrates over time, creating a cycle of elements. Restoration stimulates and enhances the microbial diversity of the soil via beneficial microorganisms.

Contamination risk by heavy metals and enzymatic stoichiometry in agricultural soils under intense use of pesticides.

Soil contamination by heavy metals (HM) from pesticides poses a serious environmental threat, affecting sustainability and agricultural productivity. Soil enzymes are essential for biochemical reactions such as organic matter decomposition and nutrient cycling and are vital for maintaining soil health. However, the effects of HM on soil enzyme activity are not yet well understood. This study examined the impact of HM contamination on enzymatic stoichiometry in regions with intensive pesticide use. We selected flower cultivation areas with 5 years (CA1) and 10 years (CA2) of pesticide exposure and a native forest area (NFA) as a reference during the dry and rainy seasons. We measured Cd, Cu, Mn, Pb, and Zn levels and employed ecological risk indices to assess contamination levels. We also analyzed enzyme activities (arylsulfatase, ß-glucosidase, acid phosphatase, urease) and enzymatic stoichiometry. CA2 exhibited the highest concentrations of Cd, Cu, and Mn in both periods, while Zn was highest in both CA1 and CA2. CA2 had higher values for all indices, indicating significant contamination. Compared with NFA, arylsulfatase activity was lower in cultivated areas during both periods, suggesting decreased soil quality. We found negative correlations between Cu, Mn, Zn, and arylsulfatase, as well as a reduction in urease with Cd; these elements also increased microbial C limitation. Our findings show that continuous pesticide input increases HM levels and that enzyme activity and stoichiometry are effective bioindicator of soil contamination. This study underscores the urgent need for guidelines to protect soils from prolonged HM buildup.

Effect of the irregular shelterwood system on soil organic carbon stock and soil quality of Shorea robusta Gaertn. f. forest in Nepal.

The effective management of forests relies on the crucial role played bysilvicultural systems. However there exist a significant knowledge gap regarding impact of these systems in Nepalese forests. Therefore, this research was conducted to assess the effects of the forest management activities under irregular shelterwood system on soil organic carbon (SOC) stock and the overall soil quality of Sal (Shorea robusta Gaertn. f.) forests in Terai region of Nepal. Stratified random sampling method with 1.67 % sampling intensity was adopted in this study where management of stands was used as basis of strata. A total of 30 composite soil samples (15 each from managed and unmanaged forest stands) were collected from a depth of 0-30 cm, taken from the four corners and the center of each plot. Soil quality index (SQI) method was used for soil quality assessment using indicators on the basis of prior studies conducted in Nepal. Our study found significant difference in soil parameters except organic carbon, pH, silt, and clay among the managed and unmanaged forest stands (p < 0.05). SOC stock of unmanaged forest stands (48.87 ± 1.34 ton ha-1) was significantly greater than managed forest stands (27.76 ± 1.27 ton ha-1). Similarly, unmanaged forest stands demonstrated better soil quality with higher SQI value (0.66) than managed forest stands (0.50). This negative impact of irregular shelterwood silviculture system highlights the necessity for management interventions to enhance SOC stock and overall soil quality. To establish a robust conclusion, further replication of similar studies at different soil depths and in other management regimes, along with longitudinal studies, is essential.

Assessing the efficacy of natural soil biotin on soil quality, microbial diversity, and Rhododendron simsii growth for sustainable landscape architecture.

Fertilization significantly influences soil quality and its sustainable use in urban garden maintenance. The widespread application of inorganic fertilizers has raised ecological concerns due to their potential environmental impacts. Organic fertilizers, while beneficial, often have slow effects and are costly. Biofertilizers, with their eco-friendly nature and low carbon footprint, are gaining attention for their multifaceted role in supporting plant growth. Despite the focus on fruit trees, vegetables, and medicinal plants, ornamental plants have been understudied. This study aims to evaluate the efficacy of a novel microbial fertilizer, 'natural soil biotin', on Rhododendron plants, specifically the Azalea hybrid 'Carnation'. The study employed a comparative approach to assess the impact of different fertilization strategies on soil properties, microbial diversity, enzyme activity, plant morphology, and physiological parameters. The application of 'natural soil biotin' was compared with the use of inorganic and organic fertilizers. The combined application of 'natural soil biotin' was found to effectively enhance soil properties and mitigate the impact of other fertilizers on soil pH. It also improved the relative abundance of beneficial microbial groups such as Proteobacteria, Ascomycota, and Basidiomycota. Furthermore, the mixed application significantly increased the activities of urease and sucrase in Rhododendron plants, which promoted their growth, development, and stress resistance. The results indicate that the mixed application of 'natural soil biotin' with inorganic and organic fertilizers not only improved the soil quality but also enhanced the efficiency of fertilizer utilization. This approach led to increased economic and environmental benefits in Rhododendron cultivation. The findings contribute to the foundation for soil improvement and ecological restoration, suggesting that 'natural soil biotin' could be a promising alternative or supplement to traditional fertilization methods in sustainable landscape architecture.

Soil quality and heavy metal contamination in an open dumpsite in Navrongo, Ghana.

The increasing proximity of the Dudumbia dumpsite, an open dumpsite in Navrongo, Ghana, to human settlements necessitates an investigation of the soil quality to safeguard the environment from heavy metal toxicity. This study examined the impact of waste dumping activities on the physicochemical properties of the soil, as well as the level of heavy metal (Pb, Cd, Ni, Cr, As, Hg, Cu, Mn, and Zn) contamination and associated risks. Various contamination and risk assessment tools were used, including the geoaccumulation index (Igeo), pollution load index (PLI), potential ecological risk (Er), and potential ecological risk index (PERI). The study found significant improvements in notable soil attributes such as phosphorus (P), organic carbon (C), total nitrogen (N), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and effective cation exchange capacity, with percentage increases ranging from 50.8 to 2078.3%. Igeo values ranged from 2.07 to 6.20, indicating contamination levels from moderate to extreme. The PLI and PERI values were 16.241 and 1810, respectively. The Er values for the heavy metals ranged from 36 to 607, indicating ecological risk levels from low to very high, with Cd and Hg posing very high risks. These results suggest that while the dumpsite soil shows improvements in some characteristics favourable for plant cultivation, waste dumping significantly contributes to heavy metal contamination. The soil at the dumpsite is deteriorated and poses significant health risks, particularly due to Cd and Hg. Therefore, remediation efforts should prioritise mitigating the risks posed by Cd and Hg.

Long-term agricultural reuse of treated wastewater and sewage sludge: developing a Time to Critical Content Index for metal species.

This study evaluates the sustainability of spreading wastewater or sewage sludge on agricultural land, balancing benefits with contamination risks. Conventional ecological risk indices often fail to address the long-term accumulation of metals in soils. We investigate the feasibility of spreading based on current knowledge of potentially contaminating metals and their behavior in soil. We analyzed the speciation of metals (Ag, Cd, Co, Cr, Cu, Ni, Pb, Ti, Zn) through sequential extraction in sludge, treated wastewater, and soils after 14 years of application of sewage sludge and treated wastewater issued from an Algerian wastewater treatment plant. We introduce a Time to Critical Content Index (TCCI) that calculates the time required to reach critical levels of potentially mobile metals, considering total metal content and speciation. The TCCI takes into account product knowledge, soil characteristics, metal behavior, ecological/toxicological thresholds, and regulations. Applied to our case study, the TCCI indicates that spreading sewage sludge can continue despite metal contents exceeding regulatory ceiling values. The index serves as a precautionary measure, adaptable to evolving knowledge, providing a comprehensive framework for sustainable agricultural practices.

Quantitative analysis of soil quality around brick kilns using pollution indices and ANOVA in Jammu district of Jammu and Kashmir, India.

The study investigated soil quality around brick kilns in the Jammu district of Jammu and Kashmir, analyzing 200 samples from 50 sites for selected parameters such as pH, electrical conductiv1ity, soil temperature, organic carbon content, organic matter, macronutrients, and heavy metals. The findings revealed that soil electrical conductivity ranged from 0.33 to 0.63 dS/m, with significant differences observed at varying distances from the kilns. Copper concentrations were highest at 5.32 mg/kg near the kilns, while iron and lead levels also varied significantly, indicating potential contamination. The mean soil temperature was recorded to be 27.69°C.The pH values ranged from 6.5 to 7.8, and the average pH of 8.22 indicated the slightly alkaline nature of the soil around the brick kilns. The organic carbon ranged from 0.34% to 1.02%.Soil temperature and electrical conductivity decreased with increasing distance from the kilns, with temperature showing positive correlations with organic carbon, organic matter, nitrogen, potassium, manganese, and iron and negative correlations with pH, phosphorus, zinc, copper, lead, and cadmium. A perfect positive correlation was noted among nitrogen, organic carbon, and organic matter. Heavy metals, except for zinc and manganese, showed positive correlations with each other. The average Zn, Cu, Mn, Fe, Pb and Cd concentration was recorded as 1.07, 1.03, 6.71, 10.30, 37.04 and 1.91 ppm, respectively. The contamination factor indicated moderate contamination with lead and cadmium, while the geo-accumulation index also suggested moderate contamination. The pollution load index reflected unpolluted soil and enrichment factor values for heavy metals ranked as Cd > Pb > Cu > Zn > Mn > Fe.ANOVA results revealed significant variations in electrical conductivity, copper, iron, and lead, underscoring the potential environmental impacts at different distances from the kilns. However, no significant differences were found between agricultural and non-agricultural sites in other physicochemical parameters. These variations highlight the considerable impact of brick kilns on soil health, emphasizing the need for enhanced environmental management and further research to mitigate these effects.

Derivation of site-specific environmental quality guideline values for fuel-contaminated soils on sub-Antarctic Macquarie Island.

Accidental fuel spills associated with the storage, transfer, and use of diesel fuel for power generation have occurred on sub-Antarctic Macquarie Island since the establishment of the island's research station in 1948. An extensive in situ remediation program was implemented by the Australian government from 2009 to 2016 that used nutrient addition and air sparging to enhance the microbial degradation of petroleum products. During this period, a range of ecotoxicological assessments were conducted to better understand the impacts of fuel in soils on native biota and their sensitivity. This study compiles this ecotoxicological data into a species sensitivity distribution (SSD) to establish environmental quality guideline values (EQGVs) for fuels in soils on Macquarie Island. The SSD model includes 13 critical effect concentrations (CECs) selected using an expert judgment approach. These include data from functional and community-based tests as well as traditional single-species toxicity tests using microbes, plants, and invertebrates and representing the range of carbon content (~3%-48%) and fuel composition at various stages of degradation (from fresh to 18 months aged) in soils as occurs at contaminated sites on the island. A protective concentration (PC80) of 97 mg/kg TPH C9-C40 (95% CI 24-283) was derived for special Antarctic blend diesel from the SSD and is recommended as an appropriate site-specific EQGV and potential remediation target for the immediate station area in the vicinity of infrastructure. More conservative PC values are also provided for areas with higher conservation values outside the station footprint. These EQGVs are the first to be produced for fuels in the sub-Antarctic and Antarctic regions. They will be used to inform ongoing environmental management on Macquarie Island and are likely suitable and recommended for use more broadly across the sub-Antarctic. Integr Environ Assess Manag 2024;00:1-13. © 2024 Commonwealth of Australia. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Long-term evolution of soil quality in citrus orchard terrace system: A whole life cycle perspective.

Terracing is widely recognized as an effective strategy for mitigating soil erosion and preserving soil quality. This study aimed to evaluate the variations in soil aggregate C, N, and P composition, as well as the soil quality index (SQI), in subtropical citrus orchards of different plantation ages (PA) and across various terrace positions (TP). Surface soil samples (0-20 cm) were collected from four TP categories: terrace wall (TW), slub ditch (SD), under grove (UG), and between grove (BG), across varying PA (5, 15, 25, 35, and 45 years). The results showed the C, N, and P concentrations in most soil aggregates, along with the SQI of the slub ditch and under grove, increased significantly with plantation age. Compared to the 5-year-old plantations, the SQI of the slub ditch and under grove increased by 84 % and 66 % at 45 years, respectively. The aggregate stability and SQI of BG generally trended upwards but declined at 25 and 35 years. By 45 years, the SQI of the terrace wall was significantly lower than that of other positions, being 58 %, 61 %, and 39 % lower compared to the slub ditch, under grove, and between grove, respectively. Additionally, the C/P and N/P ratios of the terrace wall were higher than those of other positions, indicating phosphorus limitation in TW. Path analysis revealed plantation ages had greater effects on SQI. Aggregate stability and soil properties showed significant positive impacts on SQI. Overall, as plantation age increased, the differences in SQI among the slub ditch, under grove, and between grove decreased, while the terrace wall exhibited the weakest erosion resistance. Therefore, efforts should be made to restore the ecological function of the terrace wall, such as by colonizing it with moss. Additionally, reasonable tillage plans, including appropriate fertilization, should be formulated to enhance orchard soil quality.

Survival and transfer potential of Salmonella enterica serovar Typhimurium colonising polyethylene microplastics in contaminated agricultural soils.

Agricultural environments are becoming increasingly contaminated with plastic pollution. Plastics in the environment can also provide a unique habitat for microbial biofilm, termed the 'plastisphere', which can also support the persistence of human pathogens such as Salmonella. Human enteric Salmonella enterica serovar Typhimurium can enter agricultural environments via flooding or from irrigation with contaminated water. Using soil mesocosms we quantified the ability of S. Typhimurium to persist on microplastic beads in two agriculturally relevant soils, under ambient and repeat flood scenarios. S. Typhimurium persisted in the plastisphere for 35 days in both podzol and loamy soils; while during multiple flood events was able to survive in the plastisphere for up to 21 days. S. Typhimurium could dissociate from the plastisphere during flooding events and migrate through soil in leachate, and importantly could colonise new plastic particles in the soil, suggesting that plastic pollution in agricultural soils can aid S. Typhimurium persistence and facilitate further dissemination within the environment. The potential for increased survival of enteric human pathogens in agricultural and food production environments due to plastic contamination poses a significant public health risk, particularly in potato or root vegetable systems where there is the potential for direct contact with crops.

The advantage of afforestation using native tree species to enhance soil quality in degraded forest ecosystems.

Different vegetation restoration methods have improved soil quality to varying degrees. This study, focused on the forest-grassland-desert transition zone in the Hebei-Inner Mongolia border region, and employed a systematic grid sampling method to establish fixed monitoring plots in the Saihanba Mechanized Forest Farm and the Ulan Buh Grassland. The differences in soil quality evolution across various vegetation restoration methods under the same climatic and soil historical conditions were analyzed, elucidating the roles of these vegetation restoration methods in degraded forest ecosystems, with the aim of providing a reference for ecological restoration under similar land conditions. This study used a grid method to establish sample points in the forest-grassland-desert transitional zone and assessed five methods of vegetation restoration sites: artificial forest composed of native species of Larix principis-rupprechtii (FL), artificial forest composed of exotic Pinus sylvestris var. mongolica (FP), natural secondary broad-leaved forest (FN), open grassland (GO), and enclosed grassland (GC). The differences in soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkaline hydrolysis nitrogen (AN), rapidly available phosphorus (AP) and rapidly available potassium (AK) among the different vegetation restoration sites were compared via variance analysis, and the soil quality index (SQI) was calculated to assess the soil quality at the sample points. The SOC, TN, and AN contents of forest soil were significantly greater than those of grassland, and the TN, TP, AN, AK, and SOC contents of FL, FN, and GC were significantly greater than those of FP and GO. Among them, the TN, TP, and SOC contents were the highest in the FL, reaching 2.74, 0.39, and 47.27 g kg-1, respectively. In terms of ecological stoichiometric characteristics, the average N:P ratio in the study area was 6.68, indicating a serious lack of N in the study area. Among the different types of restoration sites, the effect was stronger in the FP than in the FL, and the TN and AN contents were only 1.48 g kg-1 and 116.69 mg kg-1, respectively. The SQI in the FL was not significantly different from that in the FN or GC, but it was significantly greater than that in the FP and GO. These findings indicate that native tree species restoration in degraded forest ecosystems significantly improved soil quality, while the introduction of exotic tree species for afforestation had a minimal effect on improving soil quality.

Impacts of land use and management methods on soil quality dynamics in central highlands of Ethiopia.

Land degradation often results in poor soil quality in many parts of Ethiopia, including the study area. To address this issue and promote sustainable land management practices, various land use and management methods (LUMMs) have been implemented. However, little information is available regarding how these management practices influence overall soil quality dynamics of the study area. This study aimed at evaluating soil quality dynamics in the Urago micro-watershed, central highlands of Ethiopia, under major LUMMs: barren land (BL), grassland (GL), established farm boundary (EFB), restored degraded land (RDL), and stone-supported soil bund (SSB). Forty-five disturbed and fifteen undisturbed soil samples were collected from the ploughed soil layer (0-20 cm) of each LUMM and analysed for selected physicochemical properties to be used as indicators of soil quality. Principal component analysis and multiple correlation were used to select the minimum data set (MDS) to evaluate the overall soil quality index (SQI). The MDS included SOC, clay content, exchangeable Mg2+, and available P, which could replace other indicators for assessing the overall soil quality dynamics of the study watershed. The result showed notable variations in particle-size fractions, soil organic carbon (SOC), total nitrogen (TN), available P (av. P), and exchangeable Na+, K+, and Mg2+ levels among the LUMMs. RDL had higher sand and silt contents than SSB, whereas SSB had higher clay content compared to RDL, GL, and BL. GL, RDL, and EFB showed significantly higher levels of SOC, TN, and av. P, respectively, compared to other LUMMs. The obtained SQI showed that GL had the highest score (0.847), followed by SSB (0.703), RDL (0.701), EFB (0.644), and BL (0.628). This underscores the significance of stone-supported soil bund and restored degraded land as an efficient management method to enhance soil quality and agro-ecosystem through conserving soil and encouraging sustainable farming practices.

Changes in soil bacterial community characteristics in patches of different vegetation types under different stages of restoration in the desert of northern China.

In desert areas, the process of mobile sandy land changing to semi-fixed sandy land and eventually to fixed sandy land after undergoing vegetation restoration is inevitable. The presence of shrub patches and herb patches is common in this restoration process. No relevant studies have reported the soil bacterial community characteristics of different vegetation-type patches (shrub patches and herb patches) under different stages of restoration. Therefore, we utilized long-established experimental plots to collect soil from 0-20 cm soil layer under shrub patches (dominated by Salix psammophila) and herb patches under different stages of restoration (i.e., mobile sand land, semi-fixed sand land, and fixed sand land), by determining soil physicochemical properties, enzyme activities, and soil bacterial communities. Our results found that soil bacterial α-diversity under different restoration stages showed higher shrub patches than herb patches. The dominant bacterial communities (phyla) in shrub patches and herb patches at different recovery stages were Actinobacteria, Proteobacteria, and Bacteroidota. When the mobile sandy land returned to fixed sandy land, the relative abundance of Actinobacteria and Bacteroidota gradually decreased under shrub patches and herb patches, while the relative abundance of Proteobacteria increased significantly. In addition, herb patches significantly increased the relative abundance of bacteria (genus) relative to shrub patches at different stages of recovery. Soil nutrients, soil fine particles, and soil enzyme activities were significantly higher under shrub patches than under herb patches when fixed sandy land due to differences in life form and architecture between shrub patches and herb patches. Based on this, soil bacterial community composition and diversity under shrub patches were driven by more soil properties during the restoration of sandy land. This study complements the dynamic recovery processes and driving mechanisms of soil bacterial community structure under different vegetation patches in sandy areas, especially in the context of global climate change.

Soil Acidification Can Be Improved under Different Long-Term Fertilization Regimes in a Sweetpotato-Wheat Rotation System.

Soil acidification is a significant form of agricultural soil degradation, which is accelerated by irrational fertilizer application. Sweetpotato and wheat rotation has emerged as an important rotation system and an effective strategy to optimize nutrient cycling and enhance soil fertility in hilly areas, which is also a good option to improve soil acidification and raise soil quality. Studying the effects of different fertilization regimes on soil acidification provides crucial data for managing it effectively. An eight-year field experiment explored seven fertilizer treatments: without fertilization (CK), phosphorus (P) and potassium (K) fertilization (PK), nitrogen (N) and K fertilization (NK), NP fertilization (NP), NP with K chloride fertilization (NPK1), NP with K sulfate fertilization (NPK2), and NPK combined with organic fertilization (NPKM). This study focused on the soil acidity, buffering capacity, and related indicators. After eight years of continuous fertilization in the sweetpotato-wheat rotation, all the treatments accelerated the soil acidification. Notably, N fertilization reduced the soil pH by 1.30-1.84, whereas N-deficient soil showed minimal change. Organic fertilizer addition resulted in the slowest pH reduction among the N treatments. Both N-deficient (PK) and organic fertilizer addition (NPKM) significantly increased the soil cation exchange capacity (CEC) by 8.83% and 6.55%, respectively, compared to CK. Similar trends were observed for the soil-buffering capacity (pHBC). NPK2 increased the soil K+ content more effectively than NPK1. NPKM reduced the sodium and magnesium content compared to CK, with the highest magnesium content among the treatments at 1.60 cmol·kg-1. Regression tree analysis identified the N input and soil magnesium and calcium content as the primary factors influencing the pHBC changes. Structural equation modeling showed that the soil pH is mainly influenced by the soil ammonium N content and pHBC, with coefficients of -0.28 and 0.29, respectively. Changes in the soil pH in the sweetpotato-wheat rotation were primarily associated with the pHBC and N input, where the CEC content emerged as the main factor, modulated by magnesium and calcium. Long-term organic fertilization enhances the soil pHBC and CEC, slowing the magnesium reduction and mitigating soil acidification in agricultural settings.

Straw Retention with Reduced Fertilization Enhances Soil Properties, Crop Yields, and Emergy Sustainability of Wheat-Soybean Rotation.

Cereal + legume rotation is an integrated system that facilitates soil fertility and sustainable agricultural production. However, research on the management compatibility affecting soil physico-chemical properties yields overall agro-ecosystem sustainability, but profitability is lacking, especially under straw retention and potential reductions in fertilizer application. An 11-year field experiment investigated three treatments: no straw retention + traditional mineral fertilization (TNS), straw retention + traditional mineral fertilization (TS), and straw retention + reduced mineral fertilization (DS). Compared with TNS, TS significantly improved soil physico-chemical properties, including macro-aggregates (R > 0.25 mm), porosity, field water capacity (FWC), soil organic carbon (SOC) storage, total nitrogen storage, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) by 17.3%, 3.2%, 13.0%, 5.5%, 3.2%, 15.5%, and 13.8%, respectively. TS also significantly increased total (wheat + soybean) yields (TYs), economic profits, and emergy sustainability index (ESI) by 15.8%, 25.0%, 3.7 times that of TNS, respectively. Surprisingly, compared with TS, DS further significantly improved R > 0.25 mm, porosity, FWC, SOC storage, MBC, MBN, TY, economic profits, and ESI by 11.4%, 1.5%, 6.1%, 3.0%, 10.6%, 7.2%, 5.7%, 11.1%, and 36.5%, respectively. Overall, retaining straw with reduced fertilization enhances soil properties, yields, and emergy sustainability in wheat-soybean rotation systems.

Anthropogenic shrub encroachment has accelerated the degradation of desert steppe soil over the past four decades.

Anthropogenic and natural shrub encroachment have similar ecological consequences on native grassland ecosystems. In fact, there is an accelerating trend toward anthropogenic shrub encroachment, as opposed to the century-long process of natural shrub encroachment. However, the soil quality during the transition of anthropogenic shrub encroachment into grasslands remains insufficiently understood. Here, we used a soil quality assessment method that utilized three datasets and two scoring methods to evaluate changes in soil quality during the anthropogenic transition from temperate desert grassland to shrubland. Our findings demonstrated that the soil quality index decreased with increasing shrub cover, from 0.49 in the desert grassland to 0.31 in the shrubland. Our final results revealed a gradual and significant decline of 36.73 % in soil quality during the transition from desert grassland to shrubland. Reduced soil moisture levels, nutrient availability, and microbial activity characterized this decline. Nearly four decades of anthropogenic shrub encroachment have exacerbated soil drought conditions while leading to a decrease in perennial herbaceous plants and an increase in bare ground cover; these factors can explain the observed decline in soil quality. These findings emphasize the importance of considering soil moisture availability and potential thresholds when implementing revegetation strategies in arid and semiarid regions.

Evaluating the impact of soil erosion on soil quality in an agricultural land, northeastern China.

The impact of soil erosion on soil quality is still not systematically understood. The purpose of this study was thus to quantify the impact of soil erosion on soil quality and its change with slope morphology in an agricultural field, northeastern China based on radionuclide 137Cs, unmanned aerial vehicle derived high resolution digital elevation model, and soil sampling. 137Cs method yielded an average soil erosion rate of - 275 t km-2 yr-1 ranging from - 1870 to 1557 t km-2 yr-1. The soil quality index derived from total dataset (SQI_TDS) can be well explained by that derived from minimum data set (SQI_MDS) with a determination coefficient R2 of 0.874. SOM, sand, and cation exchange capacity in the MDS play more important roles than other soil indicators. Soil quality was significantly affected by soil erosion, with Adj. R2 of 0.29 and 0.33 for SQI_TDS and SQI_MDS, respectively. The spatial variations of soil erosion and soil quality were both affected by slope topography. Soil erosion must be controlled according to topographic and erosion characteristics in northeastern China.

Ecotoxicity of hexavalent chromium [Cr (VI)] in soil presents predominate threats to agricultural production with the increase of soil Cr contamination.

The relative severity between chromium (Cr)-mediated ecotoxicity and its bioaccumulation has rarely been compared and evaluated. This study employed pot incubation experiments to simulate the soil environment with increased Cr pollution and study their effects on the growth of crops, including pepper, lettuce, wheat, and rice. Results showed that increasing total Cr presented ascendant ecotoxicity in upland soils when pH > 7.5, and significantly reduced the yield of pepper, lettuce and wheat grain by 0.3-100 %, whereas, this effect was weakened even reversed as the pH decreased. Surprisingly, a series of soils with Cr concentration of 22.7-623.5 mg kg-1 did not cause Cr accumulation in four crops over the Chinese permissible limit. The toxicity of Cr was highly associated with extractable Cr, where Cr (VI) made the greater contributions than Cr (III). Conclusively, the ecotoxicity of Cr poses a greater environmental issue as compared to the bioaccumulation of Cr in crops in upland soils, while extractable Cr (VI) makes the predominant contributions to the ecotoxicity of Cr as the total Cr increased. Our study proposes a synchronous consideration involving total Cr and Cr (VI) as the theoretical basis to establish a more reliable soil quality standard for safe production in China.

Environmental risks of mask wastes binding pollutants: Phytotoxicity, microbial community, nitrogen and carbon cycles.

The increasing contamination of mask wastes presents a significant global challenge to ecological health. However, there is a lack of comprehensive understanding regarding the environmental risks that mask wastes pose to soil. In this study, a total of 12 mask wastes were collected from landfills. Mask wastes exhibited negligible morphological changes, and bound eight metals and four types of organic pollutants. Masks combined with pollutants inhibited the growth of alfalfa and Elymus nutans, reducing underground biomass by 84.6 %. Mask wastes decreased the Chao1 index and the relative abundances (RAs) of functional bacteria (Micrococcales, Gemmatimonadales, and Sphingomonadales). Metagenomic analysis showed that mask wastes diminished the RAs of functional genes associated with nitrification (amoABC and HAO), denitrification (nirKS and nosZ), glycolysis (gap2), and TCA cycle (aclAB and mdh), thereby inhibiting the nitrogen transformation and ATP production. Furthermore, some pathogenic viruses (Herpesviridae and Tunggulvirus) were also found on the mask wastes. Structural equation models demonstrated that mask wastes restrained soil enzyme activities, ultimately affecting nitrogen and carbon cycles. Collectively, these evidences indicate that mask wastes contribute to soil health and metabolic function disturbances. This study offers a new perspective on the potential environmental risks associated with the improper disposal of masks.