Soil Content Research Articles

Soils after forestry management activities in spruce plantations

The carbon accumulation in forest ecosystems helps to mitigate climate changes, therefore the interest in finding strategies for adapted forest management is a major goal of our time. The artificial plantations of Norway spruce (Picea abies Karst) are part of the Bulgarian project to restore the regulatory functions of forest ecosystems. Due to their low resistance, intensive processes of deposition and degradation take place in them, which emphasizes the need to understand the condition of soils and the amount of accumulated carbon in them. This paper reports results from a study on the thinning in even-aged Norway spruce plantations (Picea abies Karst) and its effect on some soil properties. The study includes two thinned plots and an untinned control: 1) Control – an unmanaged spruce plantation, without any activities in it through the last 20 years; 2) Thinned – managed with regular felling over the years, the last of which was carried out 10 years ago with 25% intensity; and 3) Ice storm – plantation damaged from an ice storm in 2007 (when it was 33 years old), felling followed by removal of all affected trees – over 95%, and afforestation with spruce saplings. The soil was examined by layers from 10 cm to 30 cm depth. The main soil characteristics connected with the carbon stocks in soil are analyzed - bulk density, skel-eton, and carbon content. The results of the experiment show that the performed forestry activities were conducted with abidance of the requirements for habitat protection and the ecosystem’s functionality in the studied sites. No significant changes in coarse fraction content and bulk density of soils were found. There is no statistical difference between the plots in the studied depths, but there is a trend of decrease in the organic carbon content in the managed sites. The differences in the soil carbon stocks are significant for the first two soil layers between the control and the managed trough thinning plot. 

Vegetation restoration in the coarse‐textured soil area is more conducive to the accumulation of Fe‐associated C

Abstract Vegetation restoration has an important effect on soil carbon (C) pool dynamics. Highly stable iron (Fe)‐associated C is an important component of the soil C pool and it plays a crucial role in the soil C cycle. However, a knowledge gap remains regarding the existence of Fe‐associated C variation during vegetation restoration. Herein, 0–60 cm soil samples of cropland, grassland, shrubland and forestland from three soil types (loam, loess and sandy soils) were collected to explore the response of Fe‐associated C to vegetation restoration. The results showed that soil Fe‐associated C proportion in the study area ranged from 2.2% to 26.3%. Surface soil (0–20 cm) Fe‐associated C content in loess and sandy soils increased following vegetation restoration, but decreased in loam soil. The accumulation efficiency of soil Fe‐associated C during vegetation restoration was higher in coarser soils. Moreover, the Fe‐associated C content and proportion of forestland with a higher soil organic matter (SOM) pool were the highest among the land use types. Vegetation restoration affects soil Fe‐associated C in two different ways: (1) increasing the SOM and dissolved organic C and improving the efficiency of C and Fe binding to promote the accumulation of Fe‐associated C; (2) decreasing the total soil Fe content, reducing the trivalent iron (Fe(III)) to bivalent iron (Fe(II)) and breaking the binding of C and Fe to decrease soil Fe‐associated C content, and these two different ways were found in all three soil types. Additionally, higher SOM accumulation efficiency and less root destruction caused by vegetation restoration in coarse soils resulted in a higher Fe‐associated C accumulation efficiency. Synthesis and applications. Vegetation and soil type strongly regulated the effects of vegetation restoration on soil Fe‐associated C. Forestlands may be the optimum vegetation type to provide soil C sequestration benefits, effectively increasing soil C pool and maximising Fe‐associated C content. This study has addressed the knowledge gap regarding the effects of vegetation restoration on soil Fe‐associated C and provides scientific basis for a better understanding of the soil C cycle and developing scientific vegetation restoration measures.

Distribution characteristics of selenium and influencing factors in the plant–soil system of an arid oasis

A total of 323 topsoil samples, 63 profile soil samples, and 55 plant root samples were collected from an oasis area on the eastern margin of the Tarim Basin in China and the selenium content and other physical and chemical indicators were analyzed. The results showed that the average selenium content in the surface soil was 0.15 mg/kg, which was lower than the national background value, and only about 4% of the surveyed land area was classified as rich in selenium. The vertical distribution of selenium was characterized by surface accumulation. The organic carbon and clay content were positively correlated and the pH levels negatively correlated with the selenium content. Soil type had little effect on selenium content, though the selenium levels in Anthrosols and Gleysols were relatively high. The selenium content for cultivated land and garden soil was higher than for other land use types. The enrichment of selenium in plant roots was highest for Apocynum venetum L., followed by Pulicaria dysenterica (L.). Bernh., Populus euphratica Olive, Tamarix chinensis Lour., Phragmites australis (Cav.) Trin. ex Steud, and Pyrus bretschneideri Rehder. Correlation analysis revealed that the enrichment of selenium in the soil was mainly controlled by supergenesis in conjunction with long-distance migration and deposition. Overall, this study provides useful information for the rational development and utilization of regional land resources.

Yellow mealworm frass: A promising organic fertilizer for common sowthistle (Sonchus oleraceus L.) and bristly oxtongue (Helminthotheca echioides (L.) Holub) cultivation

Common sowthistle (Sonchus oleraceus L.) and bristly oxtongue [Helminthotheca echioides (L.) Holub] are winter broad-leaved weeds that have gained interest for cultivation as leafy vegetables. The aim of this study was to examine the effects of frass from the yellow mealworm (Tenebrio molitor L.) on nutrient content in soil, growth parameters, and nutrient content in above-ground plant tissues of common sowthistle and bristly oxtongue. Thus, two pot experiments were carried out with 5 treatments [control, calcium ammonium nitrate (CAN) applied at a dose of 100 kg N ha−1, and insect frass applied at a rate of 3500 kg ha−1 (0.5 % w/w) 7000 kg ha−1 (1 % w/w), and 14,000 kg ha−1 (2 % w/w)]. Our results showed that the lowest values of growth parameters for both plant species were recorded in the control treatment. At the final rosette growth stage [e.g., 152 days after sowing (DAS)], the CAN treatment exhibited the highest values of rosette diameter and above-ground dry weight, followed by the highest rate of insect frass. Similarly, at 152 DAS the SPAD index values in the CAN treatment were 28.4–41.5 % higher compared to the control treatment in both species. Regarding root dry weight, the highest values were found in the CAN and insect frass 2 % treatments. In addition, the application of insect frass significantly enhanced soil fertility, with the highest levels of P and K recorded in the insect frass 2 % treatment. In contrast, the CAN treatment resulted in the highest NO3–N content in the soil (15.83 and 19.26 mg kg−1 in common sowthistle and bristly oxtongue, respectively). Moreover, both P and K content in the above-ground plant tissues had the highest values in the insect frass 2 % treatment, while the content of Mg, Mn, and Cu in plant tissues was not affected by the fertilization sources. Therefore, our findings indicate that insect frass can be an additional option in crop fertilization programs as it can improve both the soil fertility and growth of crops compared to conventional inorganic fertilizer sources. However, the effects of insect frass in mixtures with inorganic fertilizers needs to be taken into consideration in future studies.

Mobile Phosphorus Presence of Typical Chernozems on Fertiliser System

Abstract Due to the systematic utilisation of substantial amounts of phosphorus fertilisers on agricultural crops in crop rotation, the amount of available phosphate compounds increases in the soil. It ensures the maximum increase in crop yields. The study of the phosphate level in chernozem soils in various agrocenoses is really up-to-date. The gist of our research was to determine the specifics of providing mobile phosphorus in typical chernozem in field crop rotation, especially in sunflower, varying according to fertilisation systems in the forest-steppe zone of Ukraine. The assessment of mobile phosphorus content was conducted using the Chirikov method, which involves extracting mobile phosphorus compounds from the soil using a solution containing acetic acid (CH3COOH) at a concentration of 0.5 mol dm−3, with a soil–to–solution ratio of 1:25. Phosphorus was determined with the spectrophotocolorimetric method, which is based on the colour intensity of the phosphorus-molybdenum complex. Our investigations showed that the typical low-humus chernozems have considerable reservoirs of potentially exploitable phosphorus for plant nourishment. We established that the mineral and organic-mineral fertilisation system leads to a greater use of mobile phosphorus with agricultural crops of crop rotation resulting in the formation of elevated phosphate content in the chernozem soil. By the end of the second rotation, the organic-mineral fertilisation system variant displayed the greatest concentration of mobile phosphorus within the 0–25 cm soil depth, marking a surge of 15.6 mg kg−1 compared to the unfertilised variant. In the period of sunflower germination, the content of mobile phosphates increased in the soil layers at depths of 0–25 cm and 25–50 cm in the variant of the mineral fertilisation system on 17.6 and 22.2 mg kg−1 of soil compared to the alternative without the fertiliser. In the sunflower’s ripening period, the mobile phosphorus concentration in the soil at 0–25 cm depth increased significantly in the variant of organic-mineral fertilisation system by 12.0 mg kg−1 and mineral fertilisation by 14.7 mg kg−1 of soil if compared with the variant lacking the fertiliser. In the variant of the mineral fertilisation system, the amount of mobile phosphorus increased in the 0–30 cm soil depth by 18.7 mg kg−1 of soil in two crop rotations compared to the beginning of the first crop rotation.

Soil organic carbon formation efficiency from straw/stover and manure input and its drivers: Estimates from long-term data in global croplands.

New soil organic carbon (SOC) formation in cropland from straw/stover or manure input is a vital source of SOC for climate change mitigation. However, location and variations in the efficiency, specifically the ratio of new SOC formation to organic C input (NCE), remain unquantified globally. In this study, the spatial variability of cropland NCE from straw/stover or manure input and explanatory factors were determined by analyzing 897 pairs of long-term field measurements from 404 globally distributed sites and by mapping grid-level cropland NCEs. The global NCE for paddy and upland averaged 13.8% (8.7%-25.1%, 5th-95th percentile) and 10.9% (6.8%-17.3%), respectively. The initial SOC and the clay content of soil, rather than temperature, were the most important factors regulating NCE. A parabola with an apex at approximately 17 g kg-1 between the initial SOC and NCE was resolved, and a positive correlation between soil clay content and NCE was observed. High-resolution mapping of the global NCE derived from manure/straw and insight into NCE dynamics provide a benchmark for diagnosing cropland soil C dynamics under climate change and identifying priority regions and actions for C management.

Effects of nano-clay on the geotechnical properties of gypseous soil

Abstract Gypseous soils suffer from sudden settlement when subjected to water flow due to dissolving of gypsum salts, so all structures constructed on gypseous soil undergo significant deformations due to the soil’s ability to collapse. Around the world, specifically in the arid and semi-arid regions gypseous soils are mostly found also, and can be found in the west desert of Iraq and even in the southern regions, amounting about between 30 and 35% of the country’s total area. There are several techniques to improve the geotechnical properties of collapsible soils, but one of the most recent techniques is using the nano technology. Five different proportions of nano-clay (NC) were incorporated into a gypseous soil containing 80% gypsum in order to enhance its chemical and geotechnical characteristics (1, 2, 3, 4, and 5%). The tests findings (chemical, physical, and mechanical tests) demonstrated that the addition of nano-clay to gypseous soil has a significant impact on the geotechnical properties of soil where it leads to decrease the gypsum content of soil, pH value, maximium dry density, specific gravity, and collapse index. On the other hand, the utilized of nano clay material causes to increase shear strength parameters (c and φ), optimum water content and liquid limit. Adding 4% of nano-clay results in a significant decrease of 53% in the collapse index and an increase of 311% in soil cohesion and 30% in the angle of internal friction.

Soil quality enhancement by multi-treatment in the abandoned land of dry-hot river valley hydropower station construction area under karst desertification environment.

The medium-intensity karst desertification environment is typically characterized by more rocks and less soil. The abandoned land in the construction areas of the dry-hot river valley hydropower station has more infertile soil, severe land degradation, and very low land productivity. Therefore, it is urgent to improve the soil quality to curb the increasingly degrading land and reuse the construction site. Few studies have focused on the effect of soil restoration and comprehensive evaluation of soil quality with multi-treatment in abandoned land in the dry-hot valley hydropower station construction area. Here, 9 soil restoration measures and 1 control group were installed at the Guangzhao Hydropower Station construction in Guizhou Province, China, for physical and chemical property analysis. In total, 180 physical and 90 chemical soil samples were collected on three occasions in May, August, and December 2022. Soil fertility and quality were evaluated under various measures using membership functions and principal component analysis (PCA). This study showed that almost all measures could enhance soil water storage capacity (The average total soil porosity of 9 soil treatments was 57.56%, while that of the control group was 56.37%). With the increase in soil porosity, soil evaporation became stronger, and soil water content decreased. Nevertheless, no decrease in soil water content was observed in the presence of vegetation cover (soil water content: 16.46% of hairy vetch, 13.99% of clover, 13.77% of the control). They also proved that manure, synthetic fertilizer, and straw could promote total and available nutrients (Soil total nutrient content, or the total content of TN、TP、TK,was presented as: synthetic fertilizer (11.039g kg-2)>fowl manure (10.953g kg-2)>maize straw (10.560g kg-2)>control (9.580g kg-2);Total available nutrient content in soil, or the total content of AN,AP,A,was shown as:fowl manure (1287.670 mg kg-1)>synthetic fertilizer (925.889 mg kg-1)>sheep manure (825.979 mg kg-1)>control (445.486 mg kg-1). They could also promote soil fertility, among which the first two reached the higher comprehensive soil quality. Fertilizer was conducive to improve soil quality and fertility, yet long-term application could cause land degradation like soil non-point source pollution, compaction, and land productivity decline. Ultimately, combining fertilizer with biochar or manure is recommended to improve soil fertility. Biochar and green manure could play an apparent role in soil improvement only when there is abundant soil water. The above views provide theoretical support for curbing soil degradation, improving soil fertility and quality, enhancing land productivity, and promoting the virtuous cycle of the soil ecosystem.

Antarctic Spore-Forming Microorganisms from Deception Island Inhibit the Growth of Various Bacterial Strains

Antarctic microbes have evolved and adapted unique strategies to survive in the harsh polar environment. Apart from the ability to adapt to the low nutrient soil content and extremely dry and cold polar environment, a particular strategy used by Antarctic bacteria is the production of antimicrobial compounds that can eliminate rivals in the same niche, giving them a competitive edge over other microbes. In contrast, it is unclear whether spore-forming microbes possess similar antimicrobial properties as one of their survival strategies, especially those from the Antarctic volcanic Deception island in the West Antarctic. Hence, this study aims to isolate and characterize the spore-forming microbes in Deception Island, Antarctica, as well as to identify the ones that are equipped with the ability to inhibit other microorganisms. Microbes were isolated using various growth media and were segregated into clusters based on their random amplified polymorphic DNA (RAPD) fingerprints. A total of 90 strains were isolated and clustered into 30 groups at a similarity of 60%. Representative strains from each cluster were assayed for antimicrobial activities against 13 Gram-positive and Gram-negative test bacteria comprising human pathogens. Twenty-five strains exhibited the ability to inhibit at least one test bacterium. The four strains, A60, Im31, Im32 and Im33 that showed the strongest inhibitory activities were subjected to 16S or 18S rDNA sequencing and analysis to identify them. They were identified as Pseudogymnoascus, Bacillus, Leohumicola, and Talaromyces spp. The ability of the aforementioned microbes to thrive in harsh environments and compete with fierce competitors for scarce nutrients is probably due to their ability to produce antimicrobial compounds that target and kill their rivals.

Effect of Multi-Year Protection of Grapevines with Copper Pesticides on the Content of Heavy Metals in Soil, Leaves, and Fruit

This study evaluates the impact of multi-year protection of grapevines using copper-based pesticides on heavy metal content in soil, leaves, and fruit under organic and conventional cultivation methods. Conducted on Solaris, Hibernal, and Muscaris grapevine varieties in north-western Poland, the research highlights significant differences between the two cultivation approaches. In organic vineyards, copper content in soil averaged 10.25 mg/kg, significantly higher than the 9.05 mg/kg found in conventional soils. Manganese levels were also elevated in organic soils (223 mg/kg) compared to conventional ones (299 mg/kg). Conversely, conventional vineyards exhibited higher zinc and lead concentrations, averaging 47.10 mg/kg and 20.34 mg/kg, respectively, versus 43.50 mg/kg and 11.22 mg/kg in organic soils. The organic soils also had higher salinity (46.50 mg/kg) than conventional ones (30.50 mg/kg). The fruits of grapevines in organic cultivation showed higher copper and zinc levels, with the Solaris variety containing 15.01 mg/kg of copper and the Muscaris variety having 11.43 mg/kg of zinc. These levels exceed the commonly encountered ranges of <1 to 10 mg/kg. Lead content in fruits was higher in organic cultivation (2.19 mg/kg) than in conventional cultivation (1.18 mg/kg), occasionally surpassing the critical value for consumable plants (1 mg/kg). Leaves of grapevines from organic vineyards had significantly higher copper and manganese content than those from conventional vineyards, with the Hibernal variety showing the highest levels. These findings underscore the necessity for monitoring and managing heavy metal content in vineyard soils to ensure fruit quality and safety.

Root-soil-microbiome interaction in the rhizosphere of Masson pine (Pinus massoniana) under different levels of heavy metal pollution

Heavy metal pollution of the soil affects the environment and human health. Masson pine is a good candidate for phytoremediation of heavy metal in mining areas. Microorganisms in the rhizosphere can help with the accumulation of heavy metal in host plants. However, studies on its rhizosphere bacterial communities under heavy metal pollution are still limited. Therefore, in this study, the chemical and bacterial characteristics of Masson pine rhizosphere under four different levels of heavy metal pollution were investigated using 16 S rRNA gene sequencing, soil chemistry and analysis of plant enzyme activities. The results showed that soil heavy metal content, plant oxidative stress and microbial diversity damage were lower the farther they were from the mine dump. The co-occurrence network relationship of slightly polluted soils (C1 and C2) was more complicated than that of highly polluted soils (C3 and C4). Relative abundance analysis indicated Sphingomonas and Pseudolabrys were more abundant in slightly polluted soils (C1 and C2), while Gaiella and Haliangium were more abundant in highly polluted soils (C3 and C4). LEfSe analysis indicated Burkholderiaceae, Xanthobacteraceae, Gemmatimonadaceae, Gaiellaceae were significantly enriched in C1 to C4 site, respectively. Mantel analysis showed that available cadmium (Cd) contents of soil was the most important factor influencing the bacterial community assembly. Correlation analysis showed that eight bacterial genus were significantly positively associated with soil available Cd content. To the best of our knowledge, this is the first study to investigate the rhizospheric bacterial community of Masson pine trees under different degrees of heavy metal contamination, which lays the foundation for beneficial bacteria-based phytoremediation using Masson pines in the future.

Spatial modeling for detection of water retention capacity in technosols developed on carboniferous spoil heap after hard coal mining

Post-industrial areas, such as heaps, are an Anthropocene pressure on the environment but show natural potential for new ecosystem services, i.e., water retention, biodiversity, and C-sequestration. All these ecosystem functions of such sites can be developed only in the case of appropriate reclamation treatments, which are especially difficult under the conditions of carboniferous spoil heaps after coal deep mining. The study of reclamation effects has been increasingly supported in recent years by modern remote sensing techniques. This paper presents the possibilities of using selected remote sensing data and topographic indices and their effect on volumetric water content, which is crucial for habitat development. PlanetScope satellite imagery and airborne laser scanning point clouds were used to estimate the volumetric water content (VWC) of soil. This integrated analysis allows for more accurate spatial modeling of soil moisture, a key indicator of ecological restoration in degraded land. The method of generalized additive models was used to develop a predictive model. The developed predictive model was characterized by the following values of model accuracy evaluation parameters: MAE – 4.1%; RMSE – 5.6%; and R2–0.49. As a result of the analysis, topographic and spectral variables with significant influence on VWC were identified, and a map of the retention capacity of the Sosnica heap was developed.

Experimental evaluation on in-soil water migration reducing performance of restraining moisture geotextile (RMG)

Engineering materials such as geosynthetics clay liners (GCL) and gravel layers are effective to cut off the in-soil water migration and have been widely employed to stabilize the moisture content of subgrades. However, the moisture stabilizing performance of GCL or gravel layer is usually compromised due to the complexity of service condition. This paper introduces an engineering material named restraining moisture geotextiles (RMG), which is expected to show low permeability as GCL. With characterization of basic properties of RMG, moisture migration column test of silty soil and test cases with employments of RMG, GCL, and gravel layer are performed, respectively. The temperature and moisture fields of soil columns subjected to a freezing-thawing process are measured, and the capillarity and in-soil water migrating behavior are analyzed. Carbon footprints of GCL and RMG are compared and discussed. Test results show that RMG, GCL and gravel layer are effective to cut off the capillarity, but the gravel layer can result in higher moisture content in silty soil due to the vapor migration and capillary isolation. In conclusion, RMG can be an alternative method with low permeability on reducing the in-soil water migration, and is much lighter and more engery-efficient than GCL.

Vermicompost Effects on Soil Chemistry and Biology: Correlations with Basil's (Ocimum basilicum L.) Total Phenolic Content and Phenological Traits

This study explores the effects of vermicompost on the chemical and biological properties of soils, their nutrient content, and the impact on the growth and phenolic content of basil (Ocimum basilicum L.). Using a controlled experimental setup, we tested five dosages of vermicompost (0%, 4%, 12%, 20%, and 24%) to evaluate their influence on soil biological activity by measuring basal respiration (CO2-C), microbial biomass C (MBC-C), and dehydrogenase enzyme activity (DHA) as well as on basil's growth parameters and total phenolic content (TPC). The results show that vermicompost addition to soil enhanced soil microbial activity in direct proportion to the dose of vermicompost. The application of lower dosages of vermicompost (4% and 12%) significantly enhanced both fresh and dry weights, suggesting an improvement in nutrient uptake and soil structure, which likely facilitated better root growth and nutrient absorption. However, higher dosages (20% and 24%) were associated with reduced growth metrics, likely due to nutrient overload or salt stress. Notably, the highest vermicompost concentration (24%) led to a substantial increase in total phenolic content (TPC) in basil leaves, correlating with decreased growth metrics. This response indicates the plant's defensive mechanism against oxidative stress caused by excess nutrients or salinity from the vermicompost. A multiple regression analysis following a correlation analysis also revealed an inversely proportional relationship between phosphorus content in the soil and total phenolic content in basil leaves. Our findings illustrate that while moderate vermicompost dosages optimize plant growth and health, higher concentrations can strategically enhance phenolic content due to nutrient overload or salt-induced stress. These results offer critical insights for tailoring organic amendment applications to balance plant growth and biochemical properties in agricultural practices.

Copper Sulfate Supplementation Alleviates Molybdenosis in the Tibetan Gazelles in the Qinghai Lake Basin.

Molybdenum (Mo), an essential mineral, plays a key role in the vital activity of the organism. However, excess Mo in the forage will cause loss of appetite, diarrhea, emaciation, bone injury, joint abnormalities, and anemia in animals. In order to study molybdenosis in the Procapra picticaudata in the animal rescue center, samples of soils, forages, blood, and liver were collected. The mineral contents of all samples were determined, and the blood parameters were also measured. The results showed that the Mo level in the soil and forage in the animal rescue center was significantly higher than that in healthy pastures (p < 0.01). The Mo concentrations in the blood and liver in the P. picticaudata from the animal rescue center were also noticeably higher than those in healthy animals (p < 0.01). The level of Cu in the blood and liver were noticeably lower than those in healthy P. picticaudata (p < 0.01). The superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and catalase (CAT) were significantly lower than those in healthy animals. Supplementing copper sulfate (CuSO4) could significantly decrease the Mo content in the blood, and cure molybdenosis. In summary, the excessive Mo content in the soil and forage in the animal rescue center had greatly affected physiological parameters and antioxidant capacity. It is likely that the molybdenosis of the P. picticaudata is caused by the high Mo contents in soils and forages. CuSO4 may alleviate molybdenosis in P. picticaudata.

Gnssrefl: an open source software package in python for GNSS interferometric reflectometry applications

An open source software package has been developed for Global Navigation Satellite Systems (GNSS) interferometric reflectometry. The gnssrefl package is written in python; it can be installed from the source code, the python packaging index website, or via a docker. It includes modules that download GNSS data and orbit data from global archives. A periodogram is used to retrieve the height of the GNSS antenna over the reflecting surface using signal to noise ratio data. Signals from the Global Positioning System, Glonass, Galileo, and Beidou constellations are supported. Modules are provided to estimate volumetric water content of soil, snow depth/accumulation, and water level. Utilities for mapping and assessing reflection zones and determining the maximum resolvable height are available.

Characterization and Source Analysis of Heavy Metal(loid)s Pollution in Soil of an Industrial Park in Kunming, China

This study investigated the characteristics and sources of heavy metal(loid) pollution in the soil of a key industrial park in Kunming, China. In total, 60 soil samples (40 from agricultural land and 20 from construction land) were collected from and around the park. The soil pH and contents of Arsenic (As), lead (Pb), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), nickel (Ni), and chromium (Cr) were measured. The contents of the eight heavy metal(loid)s were analyzed using the background values of heavy metal(loid)s in the Kunming soil. The pollution load, geoaccumulation, and Nemero Comprehensive Pollution Indices were used for environmental risk evaluation. Cluster and principal component analyses were used to resolve heavy metal(loid) sources. Cd was enriched in construction and agricultural soils. As, Hg, Cd, Pb, Cu, and Zn exhibited large spatial differentiation and were significantly affected by the external environment. A regional pollution load index of 3.02 indicated overall heavy pollution. The pollution load index for each heavy metal(loid) indicated light pollution. The geoaccumulation index indicated relatively severe As, Cd, Cu, Pb, and Zn pollution. The Nemero Composite Pollution Index value showed that the study area was heavily polluted, with construction land being mildly polluted by Cd, and agricultural land being moderately polluted. The results of the spatial distribution show that there were high levels of contamination in the center. Correlation and principal component analyses showed that the pollution sources of the eight heavy metal(loid)s varied. Hg, Cd, and Pb originate primarily from industrial and agricultural pollution. Traffic sources significantly impacted Cu, Pb, Cd, and Cr. Natural sources are the main sources of Cr, Ni, and Cd. Ni is also affected by industrial sources, whereas Zn and Cu are affected by agricultural pollution. The influences of As, Cd, and Pb on the surface soil in the study area were more serious. Cd is more widely polluted and should be a priority in controlling soil heavy metal(loid)s.

Carbon Storage Potential and Saturation Behavior of Soils As Influenced by Level of C Input and Soil Types in Indian Sub-Continent

ABSTRACT Agricultural soils have the potential to store C (carbon), thereby improving soil health, and contributing to climate change mitigation. However, the capacity of a soil to hoard C may be limited. We tested the C saturation behavior of agricultural soils belonging to predominant soil orders (Inceptisols, Entisols, Alfisols, Aridisols and Vertisols) in Indian Subcontinent. A mesocosm experiment in open environmental conditions was conducted with six rate of farmyard manure (FYM) addition (0, 2.5, 5.0, 10.0, 20.0 and 40 Mg ha−1) for three and half years and total carbon (TC) was analyzed. Addition of more than 10 Mg FYM ha−1 enhanced TC content of soil with the period of experimentation irrespective of soil orders. Application of C input of the agriculturally recommended addition of FYM in India at 5.0 Mg ha−1 maintained the soil TC content. Without addition of any C input, sometimes there was depletion in native carbon. With higher levels of C additions, all the soils did not show any evidence of C saturation, thereby suggesting their higher potential to additional C storage. Indian agricultural soils could contribute significantly toward achieving the target of “4 per 1000” initiative of the United Nations. Higher organic carbon in soils would make agroecosystems more resilient toward extreme climate events and sustain crops productivity thereby could help to meet the food demand of the ever-increasing population of the country in the years to come.

Fungal necromass contribution to carbon sequestration in global croplands: A meta-analysis of driving factors and conservation practices

Fungal necromass carbon (FNC) contributes significantly to the build-up of soil organic carbon (SOC) by supplying abundant recalcitrant polymeric melanin present in the fungal cell wall. However, the influence of a wide range of conservation practices and associated factors on FNC accumulation and contribution to SOC in global croplands remains unexplored. Here, a meta-analysis was performed using 873 observations across three continents, together with structural equation modeling, to evaluate conservation practices and factors responsible for the enhancement of FNC and SOC. FNC content (8.39 g kg−1) of North American soils was highest compared to FNC content of Asian and European soils. The structural equation models showed a significant (p < 0.05) positive influence of microbial biomass carbon (MBC), soil pH, and clay contents on the accumulation of FNC. Soil C/N ratio and climate factors, however, had only minor influences on FNC accumulation. Notably, the main driver of FNC was MBC, which is mainly influenced by the soil total N and geographic factors in the study areas. Typical 5 cropland practices had significant effect size (p < 0.05) on FNC, leading to an increase of 12 % to 26 %, and the FNC content was greatest under straw amendment (26 %). Fungal necromass accumulation efficiency ranged from 23 % to 45 % depending on cropland practices: non- and reduced tillage was the most efficient (45 %), followed by crop coverage (32 %), straw amendment (30 %), and manure application (27 %), while N fertilization had the lowest efficiency (23 %). We conclude that FNC contributes to over a quarter of SOC, highlighting its major role in enhancing C sequestration worldwide. Conservation practices, particularly non-tillage or reduced tillage, are important to enhance C sequestration from FNC in croplands.

Heavy Metal Uptake and Hyperaccumulation in Some Wild Plant Species Köyceğiz Special Environmental Protection Area Located Around Old Chrome Mineral Deposits

In this study, the possible presence of heavy metals in the soil and wild plant species around the old Cr deposits of Köyceğiz-Dalyan Special Environmental Protection Area (Sandras Mountain) was investigated. Possible anthropogenic risk factors to which wild plant biodiversity is exposed are also the subject of this research. Fe, Cd, Co, Cr, Ni and Pb contents of soil, shoot and root samples of five wild plant species growing naturally in the region in question were investigated. These five species are: Alyssum masmenaeum (AM), Cytisopsis pseudocytisus (CP), Centaurea ensiformis (CE), Fumana aciphylla (FA), Phlomis angustissima (PA). The data obtained showed that heavy metals other than Ni, Cr and Co were found within normal limits in the soil samples. Particularly, soil Ni content is extremely high. Heavy metals except Ni, Cr and Fe were found within normal limits in shoot and root samples. One species (AM) for Ni and three species (FA, PA and CE) for Fe showed distinct hyperaccumulator properties. Ni hyperaccumulation detected in the Alyssum masmenaeum species is a particularly striking but well-known phenomenon. Since the research area has special environmental protection status, the soil structure and endemism of the region must be absolutely protected.