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The acidic soils of western Newfoundland require liming for successful production of most crops. Locally sourced paper mill waste wood ash (WA) and paper sludge (SL) have potential as cheaper alternatives to limestone (LIME). Two greenhouse experiments evaluated WA and SL as liming and soil conditioning amendments for annual ryegrass (Lolium multiflorum) production. At 55 days after seeding, soil pH in WA (6.2 and 6.3) and wood ash and paper sludge (WASL) (6.0 and 6.3) were not different from that in LIME (6.0 and 6.5) for Experiments 1 and 2, respectively. However, pH in SL was 0.4 and 0.3 points lower than in LIME. Compared to LIME, WA, SL, and WASL produced 31%–52% and 57%–74% greater biomass yield in Experiments 1 and 2, respectively. N uptake was greater in WA (60 and 129 kg N ha−1) and WASL (51 and 97 kg N ha−1) compared to LIME (40 and 85 kg N ha−1), in Experiments 1 and 2, respectively. SL did not differ from LIME in Experiment 1, but reduced N uptake by 57% in Experiment 2. The results show significant potential of WA as an alternative amendment for liming and yield improvement of annual ryegrass grown in NL podzolic soils. However, SL has limited potential due to the risk of increasing N immobilization and residual soil mineral N when growing conditions are limiting. Combining SL with WA or biochar seemed to alleviate these risks. Overall, the adoption of these amendments for field production systems warrants serious consideration, following supplemental field studies to determine optimal application rates and timing. Core Ideas: The podzolic soils of Newfoundland have low pH and fertility, hence require liming.Locally sourced wastes, such as paper mill wood ash (WA) and sludge (SL), could be used as liming and nutrient sources.WA was equivalent to limestone (LIME) in improving and sustaining optimal soil pH.WA produced 52% and 74% greater annual ryegrass yield than conventional LIME application in podzolic soils. [ABSTRACT FROM AUTHOR]

Land-use change in the boreal forest region leads to agriculture to be carried out on acid, shallow and low fertility soils. To correct soil fertility and promote crop productivity, manure and inorganic fertilizers are added, increasing the risk for greenhouse gas emissions (GHGE). To reduce the reliance on synthetic soil amendments while taking advantage of locally relevant industrial by-products, wood ash (WA) and paper sludge (SL) have been proposed as soil amendments for a range of soil types. We posited that amending soils with WA , SL and biochar will improve soil health parameters and fertility of boreal soils. Microbial activity resulting to nitrogen losses and availability were assessed. WA had a stronger ameliorative effect on acid boreal soils compared to SL. Both WA and SL increased soil microbial biomass and basal respiration resulting in higher net mineralization and thus significant increases in CO 2 emissions. Co-application of urea with WA or SL further increased net mineralization compared to when used independently. Conversely, the biochar's effect was short-lived and not significant. Nevertheless, addition of biochar was shown to reduce CO 2 emissions in all cases except in WA amended soils. No significant differences were observed in CH 4 emissions across all treatments. WA and SL may improve soil fertility and quality but could also contribute significantly to GHG emissions in acid boreal soils. Further research is recommended to assess the mitigating effect of various biochar feedstocks on GHG emissions when co-applied with WA and SL. • The effect of wood ash and paper sludge on acid soils was tested in incubation tests. • Both increased the soil microbial biomass, respiration, and net mineralization. • Greenhouse gas emissions were larger for paper sludge amended soils. • Supplementing biochar to wood ash increased soil CO 2 fluxes. • Supplementing biochar to paper sludge or limestone ash reduced soil CO 2 fluxes. [ABSTRACT FROM AUTHOR]

Soil biochar is a kind of organic matter rich in carbon, which is of great significance in soil fertility improvement, fertilizer type innovation and greenhouse gas emission reduction. In this paper, Mg-modified biochar was prepared by thermal cracking using rice straw and corn straw as raw materials. The Mg-modified biochar and unmodified biochar were fully mixed with prepared soil samples at the addition amounts of 0.5% (w/w), 1% (w/w) and 2% (w/w), respectively, and then simulated indoor soil cultivation experiments were carried out. The effects of magnesium ion-modified biochar and non-modified biochar on soil chemical properties and the effects of different amounts of biochar on soil properties were studied. The results showed that the yield of Mg-modified biochar from rice straw and corn straw, prepared by pyrolysis, was 65%, and the ash content was large. The pH of MG-modified corn stalk biochar (MCBC) is weakly basic (8.55), while the pH of MG-modified rice stalk biochar (MRBC) is basic (10.1), and their internal structures are slightly different. After the application of biochar prepared from rice straw and maize stover, soil indicators were determined. Compared to the control, the chemical properties of the treated soil samples were significantly improved, with an increase in soil pH, an increase in the content of effective nutrients, such as fast-acting potassium, fast-acting phosphorus and alkaline dissolved nitrogen, and an increase in the content of the total phosphorus and total nitrogen, as well as an increase in the content of organic matter. The Mg-modified biochar was generally superior to the unmodified biochar in improving soil fertility, at the same addition level. It was also found that the rice-straw biochar performed better than the corn-stover biochar and had a more obvious effect on soil improvement in terms of fast-acting potassium, ammonium nitrogen, nitrate nitrogen, total phosphorus and total nitrogen contents. [ABSTRACT FROM AUTHOR]

This paper describes a wireless and battery‐free soil pH sensor made entirely of degradable materials. Soil pH monitoring is significant for precision agriculture and environmental conservation because soil health can be estimated by measuring soil pH. Soil pH can be measured by collecting soil samples and analyzing them in a laboratory environment or by inserting an electrode‐type sensor into the soil and measuring soil pH on site. However, neither method is suitable for wide‐area soil pH sensing for precision agriculture or environmental conservation. Herein, a fully biodegradable wireless pH sensor is presented that can be dispersed to outdoor environment to detect soil acidity. The sensor is operated wirelessly through split‐ring resonators (SRRs) that consist of patterned octacalcium phosphate (OCP)‐coated magnesium (Mg) on a poly‐lactic acid (PLA) sheet. At acidic soil pH, the degradation of each SRR results in a change in the electromagnetic response of the sensor. The operation of the sensor in six different types of acidic soils is demonstrated to distinguish the acidic soil wirelessly. It is expected that the biodegradable sensor can be applied to low‐cost, easy‐to‐use, and environmentally friendly monitoring of soil pH. [ABSTRACT FROM AUTHOR]

Soil microbial communities, which play a key role in the provision of essential ecosystem services, are significantly influenced by several physical and chemical soil properties that may change with land management. This study explores the effect of different land cover types (coniferous tree stands, broad-leaved stands, shrublands, pastures/grasslands and croplands) on physical, chemical and microbial properties (all contributing to soil health) in southern European areas under moderate-high desertification risk selected in Italy, Spain and Portugal. In sites that differ in land cover, we determined microbial biomass (C mic), activity and indices of microbial metabolism including C mic /C org ratio, metabolic quotient (qCO 2) and quotient of mineralization (qM). Soil physical and chemical properties were also measured, comprising bulk density (BD), water content (WC), pH, cation exchange capacity (CEC), total organic C (C org) and some of its labile fractions, extractable C (C ext) and mineralizable C (C min), total N content and C/N. Results showed that land cover type played a strong role in determining magnitude of microbial variables with biomass and activity being higher under coniferous tree cover than in other land covers, according to trends in WC, CEC, C org , C ext , C min , N, C/N. Compared to land cover, aridity index had lower effect on investigated variables. In comparison to sites with higher C org content, sites with lower C org content (most croplands) tended to lose C more rapidly, as suggested by high qM values, except for Spanish acidic soils. Therefore, urgent actions must be taken to counteract the tendency of C-poorer soils to lose C, promoting land cover types that facilitate soil recovery by ensuring denser and more continuous soil cover over time. We also identified a minimum set of soil variables that provide information on soil health changes in both short term (microbial variables) and longer term (physical and chemical variables) in areas under desertification risk. [Display omitted] • Land cover is a key factor affecting soil health in areas at desertification risk. • Coniferous cover had the best effect on soil microbial, physical and chemical variables. • Croplands, grasslands, shrublands and broad-leaved soils differed at a lesser extent. • Soils poorer in organic C tended to lose C more rapidly than richer soils. • A minimum data set of soil health indicators was proposed. [ABSTRACT FROM AUTHOR]

Background and aims: The frequent occurrence of extreme rainfall events results in soils experiencing drying–rewetting (DRW) cycles. Such rewetting can lead to a surge in soil CO2 emissions; however, the main regulatory factors involved in this priming effect are unclear. Methods: In this study, we conducted a meta-analysis using data extracted from 43 published papers, to determine the direct regulatory factors involved in the priming effect of soil CO2. Results: The results indicated that the priming effect of rewetting on soil CO2 emissions was influenced by ecosystem type, soil properties, climatic factors, and the number of DRW cycles. The priming effect was the highest in cropland but the lowest in grassland when taking flux values observed before rewetting as the control group. It was also greater in acidic soils (pH < 6.5) and soils with a high clay fraction (clay ≥ 30%) than in other soils. The effect size (lnRR) of soil CO2 emissions was exponentially related to the mean annual precipitation (MAP), and decreased with increases in MAP. In DRW experiments, the priming effect of the first rewetting on soil CO2 emissions was the largest, an effect that gradually decreased with the number of DRW cycles, before disappearing completely. Most importantly, soil moisture influenced the peak time and the pulse time of the priming effect: the greater the change in soil moisture, the longer the peak time duration; the higher the maximum soil moisture content after rewetting, the longer the pulse time duration; and the lower the initial soil moisture content, the bigger the priming effect. Conclusion: Generally, physical mechanisms, especially soil moisture, directly regulate the CO2 priming effect during DRW cycles. Thus, this study provides a theoretical basis for assessing and predicting the impact of future precipitation changes on soil carbon cycling. Future studies should also carefully monitor any changes in soil microorganisms in response to changes in soil moisture during DRW cycles, because these appear to be significantly involved in CO2 release from soils. [ABSTRACT FROM AUTHOR]

Volcanic tuffs rich in chabazite zeolites have been extensively examined for their potential to enhance soil properties and increase fertilizer efficiency, both in their natural state and when enriched with nitrogen (N). However, there is a scarcity of data regarding their utilization in acidic sandy soil, particularly when used alongside organic fertilizers. This paper presents the findings of a 50-day laboratory incubation study that investigated the dynamics of N pools in an acidic sandy-loam agricultural soil treated with various N sources. These sources included urea, N-enriched chabazite zeolite tuff, and pelleted composted manure applied at a rate of 170 kg N/ha. Additionally, the N sources were tested in combination with chabazite zeolite tuff mixed into the soil to assess its role as a soil conditioner. The results revealed distinct behaviours among the tested N sources, primarily impacting soil pH and N dynamics. Soil fertilized with manure exhibited slow N mineralization, whereas N-enriched zeolite displayed a more balanced behaviour concerning net NO3−-N production and NH4+-N consumption. Both N-enriched zeolite and urea temporarily altered the soil pH, resembling a "liming" effect, while pelleted manure facilitated a prolonged shift towards neutral pH values. Considering the water adsorption capacity of zeolite minerals, caution is advised when adjusting water content and employing combustion methods to measure soil organic matter in zeolite-treated soil to avoid potential inaccuracies. In summary, N-enriched chabazite zeolite tuff emerged as a valuable N source in acidic sandy-loam soil, offering a promising alternative to synthetic fertilizers and showcasing a sustainable means of N recycling. [ABSTRACT FROM AUTHOR]

Selenium is an important element for human health. Many studies have identified selenium deficiency in soil and water as an important factor in causing Keshan Disease (KD) in Northeast China. Previous studies have mainly focused on soil selenium content, staple food selenium content, and human selenium level, but there are few systematic studies on soil selenium's existing forms and their migration from soil to crops and the human body. This paper focused on inferring the barrier factors in the migration of selenium from soil to crop and the human body and transformation of its compounds. It provides a reference basis for the etiological analysis, prevention, control, and elimination of KD. The study used 121 183 samples of topsoil (0−20 cm), 30 295 soil parent samples of selenium and other geochemical indices in northeast China, and crop seeds and human hair samples from the KD endemic area. The surface soil selenium was dominantly selenium-sufficient in Northeast China. However, the soil selenium levels were generally low. The average topsoil selenium in Northeast China was 0.20 mg/kg, significantly lower than the world's average soil selenium content (0.4 mg/kg) and slightly lower than the Chinese average soil selenium content (0.24 mg/kg). Soil selenium mainly existed in strongly bounding by organic bound, with humic acid, and residue forms. The amount of selenium available to plants was sufficient in the selenium-sufficient and KD-endemic areas. However, the average selenium content of human hair was deficient, on average, with 0.16 mg/kg in KD endemic area. We assume that lower soil selenium content may be the basic factor influencing the biogeochemical deficiency of selenium in Northeast China. The sequestration of selenium by clay chemical constituents, such as iron and aluminum oxides and soil organic matter, especially in acidic soils, is another direct contributing factor to the low selenium content in biogeochemical food chain, which increases the risk of KD in the population. [ABSTRACT FROM AUTHOR]

Acid soils cover about 30% of the total ice-free land area. Based on this, the study aimed to evaluate soil acidity correction, focusing on identifying studies on limestone recommendations and corrective measures in agricultural systems. To do so, a systematic literature review (SLR) was carried out, composed of: 1) a systematic literature mapping (SLM), which identifies studies using topic-specific keywords and database automatic search; 2) Snowballing, technique that expands the initial selection using references of the selected studies; and 3) a SLR to synthesize the selected papers. First, 169 scientific papers were selected, of which 116 by SLM, 26 by backward Snowballing, and 27 by forward Snowballing. Most of the papers were about lime requirement (LR) methods (43%) and liming effects on soil and plants (19%). A total of 26 LR methods were found in the papers, of which most were base saturation and Shoemaker-McLean-Pratt methods. Calcium and magnesium carbonates, as well as dolomite, were the main sources of soil acidity correction. In brief, the study provided a critical and constructive analysis of the existing literature on soil acidity correction; the findings showed that liming is the most used and effective method to neutralize soil acidity. [ABSTRACT FROM AUTHOR]

Acid sulfate soils (ASS) are rich in Fe, low in available P, and low in soil pH. In acid soils, low P availability is associated with high Fe concentration, which has a high capability in P retention. The reactivity of Fe oxyhydroxides turns large proportions of soil P into insoluble or unavailable form. This review paper is addressed to provide new insights into the Fe and P relationship as the P source for rice (Oryza sativa L.) in ASS. Fertilizer application did not significantly alter P solubility in soil solution due to high reactivity and retention power of Fe mineral in ASS, but rice cultivation practice such as water management and soil amelioration has influenced formation, crystallization and character of Fe mineral. Subsequently determining adsorption and desorption of P. Soil waterlogging and drying alternately during rice cultivation have change soil pH and redox potential (Eh), causing dissolution of P from vivianite and reduction of Fe(III)-P to Fe(II)-P. We summarize that Fe-P pools (amorphous-Fe-P) in the rice fields in ASS are categorized as readily available or labile P fraction. [ABSTRACT FROM AUTHOR]

Soil acidification is a natural phenomenon that human activity can accelerate or manage. Acid soils limit plant growth by reducing nutrient availability and causing aluminum toxicity, significantly reducing crop production. Liming has proven efficient for increasing crop yield on acidic soils. Knowledge is required on the effect of liming on the soil pH dynamics to find the suitable material, application rate, timing, and method. The objective of this study was to develop a prediction model of soil pH temporal variations after lime application using data from the literature. A database was built from research results extracted from 16 scientific papers that provided data on soil acidity changes over time under different liming treatments. Machine learning (ML) was used to predict soil pH dynamics from eight predictive parameters: rate of application, time since application, neutralizing value (CCE), grind fineness (D50), pH measurement depth, soil acidity (pH prior to liming), the type of solution used for pH measurement (water or CaCl 2) and the soil:solution ratio used to measure pH. Since soil pH fluctuates with seasons, all pH values were expressed as difference between the actual pH value and that of an unlimed control (ΔpH). The Random Forest (RF) algorithm was tested to predict ΔpH over time. On testing, we obtained an R2 between measured and predicted ΔpH values of 0.881 and an RMSE of 0.230. These results are excellent, considering the heterogeneity in soils, liming materials, and pedoclimatic conditions found in the 16 papers. The primary factors influencing ΔpH, ranked by their impact are application rate, time elapsed post-application, and lime characteristics including its grind fineness and neutralizing value. • Random Forest robustly predicts soil pH change over time following lime application. • The predictors are: rate, neutralizing value, particle size, depth, and initial pH. • The model predicts that, on average, lime increases soil pH for 82 weeks. • Machine learning models are promising tools in managing liming practices. [ABSTRACT FROM AUTHOR]

Biochar is important for soil improvement, fertilizer innovation, and greenhouse gas reduction. In this paper, Mg-modified biochar was prepared from rice and corn straw and mixed with soil at a 1% (w/w) addition in an indoor soil simulation experiment to study the effect of Mg-modified biochar on the chemical properties of acidic soil. The results showed that the addition of Mg-modified biochar reduced soil acidity and improved soil fertility. Compared with the control group, the Mg-modified biochar treatment significantly increased the concentrations of available potassium, available phosphorus, total phosphorus, organic carbon and exchangeable calcium and magnesium in the soil, and effectively increased the concentration of total nitrogen. Rice straw Mg-modified biochar treatment was more effective in increasing the soil-available potassium, available phosphorus, total phosphorus and exchangeable magnesium concentration, while corn straw Mg-modified biochar was more effective in increasing the soil organic carbon and exchangeable calcium concentration. In addition, the high pyrolysis temperature of Mg-modified biochar was more effective in promoting the soil-available potassium, available phosphorus and total nitrogen concentration, while the low pyrolysis temperature of Mg-modified biochar was more effective in promoting soil alkaline nitrogen, exchangeable calcium and magnesium. [ABSTRACT FROM AUTHOR]

Established international soil classification systems have not properly accommodated acid sulfate soils (ASS) and soil materials in Finland and Sweden because: (1) in these soils some diagnostic ASS properties are too deep to meet the depth requirements, and (2) there is a lack of defined diagnostic soil classification criteria for acidic and potentially acidic soil materials that do not completely fulfill the diagnostic pH-criterion of pH < 4.0. In this paper, two new ASS materials are introduced with the prefix "para" for parasulfuric material (oxidized material) and parahypersulfidic material (reduced material). These materials have diagnostic pH-criteria of pH 4.0-4.5 and 3.0-3.5 (field-pH for parasulfuric material and incubation-pH for parahypersulfidic material) for mineral and organic soil materials (here defined as > 20% organic matter; peat and gyttja), respectively. The term "para-acid sulfate soil (para-ASS) material" is introduced for soil materials which may have a considerable environmental impact due to mobilization of acidity and dissolved metals. Because organic acids may lower pH to values below the established pH-value of < 4.0 for ASS materials, a pH of < 3.0 is used in the Finnish-Swedish ASS classification for organic soil materials. These changes and new additions to existing diagnostic ASS materials have consequently also led to a slight modification of the required field-pH values of the existing terms "hypersulfidic material" and "sulfuric material". The Finnish-Swedish ASS classification further includes a systematic way for classification of the entire soil profile and no depth requirements for diagnostic ASS materials are present; what matters is the current or potential environmental impact that the soil has or may have. It is proposed that the Finnish-Swedish ASS classification may serve as a framework for establishing a unified ASS classification globally and that the new diagnostic ASS materials are included in relevant international soil classification systems. [ABSTRACT FROM AUTHOR]

Simple Summary: This paper focuses on the role of synergistic removal effects of earthworms and plants on two types of chromium-contaminated soils and their biological responses. We firstly examined the synergistic removal rate of chromium from contaminated acidic and alkaline soils via earthworms and plants, and then analyzed the speciation characteristics of chromium in soil after the experiment. Additionally, we also explored the accumulation of chromium in organisms and the earthworm intestinal bacterial community to reveal the biological responses. The main contribution of this study was to successfully prove that the combined use of Eisenia fetida and ryegrass had the best effect on removing chromium pollution from soil, and acidic soil exerted stronger pressure on earthworms which finally unbalanced the intestinal bacterial phyla. In future studies, we should consider not only the removal effect of heavy metals on soil via organisms, but also the stress effect on organisms themselves, and weigh up the advantages and disadvantages, which would be more conducive to the sustainable development of the ecological environment. Soil heavy metal pollution has become one of the major environmental issues of global concern and solving this problem is a major scientific and technological need for today's socio-economic development. Environmentally friendly bioremediation methods are currently the most commonly used for soil heavy metal pollution remediation. Via controlled experiments, the removal characteristics of chromium from contaminated soil were studied using earthworms (Eisenia fetida and Pheretima guillelmi) and plants (ryegrass and maize) at different chromium concentrations (15 mg/kg and 50 mg/kg) in acidic and alkaline soils. The effects of chromium contamination on biomass, chromium bioaccumulation, and earthworm gut microbial communities were also analyzed. The results showed that E. fetida had a relatively stronger ability to remove chromium from acidic and alkaline soil than P. guillelmi, and ryegrass had a significantly better ability to remove chromium from acidic and alkaline soil than maize. The combined use of E. fetida and ryegrass showed the best effect of removing chromium from contaminated soils, wih the highest removal rate (63.23%) in acidic soil at low Cr concentrations. After soil ingestion by earthworms, the content of stable chromium (residual and oxidizable forms) in the soil decreased significantly, while the content of active chromium (acid-extractable and reducible forms) increased significantly, thus promoting the enrichment of chromium in plants. The diversity in gut bacterial communities in earthworms decreased significantly following the ingestion of chromium-polluted soil, and their composition differences were significantly correlated with soil acidity and alkalinity. Bacillales, Chryseobacterium, and Citrobacter may have strong abilities to resist chromium and enhance chromium activity in acidic and alkaline soils. There was also a significant correlation between changes in enzyme activity in earthworms and their gut bacterial communities. The bacterial communities, including Pseudomonas and Verminephrobacter, were closely related to the bioavailability of chromium in soil and the degree of chromium stress in earthworms. This study provides insights into the differences in bioremediation for chromium-contaminated soils with different properties and its biological responses. [ABSTRACT FROM AUTHOR]

In the course of highway construction and use in loess area, subgrade settlement disease is common and has great destructiveness. The cone penetration test (CPT), especially the pore pressure cone penetration test, can provide three continuous readings along the exploration depth cone tip resistance, lateral friction resistance and excess pore water pressure. In this paper, CPT tests are carried out in the losses areas in Shanxi, China. Some data and curves are obtained by using CPT, which are quite different from those obtained by conventional drilling, reflecting the soil layer characteristics of the subgrade section, in order to provide a reference for similar projects. The results showed that CPT has a strong advantage in the analysis of the effect of compacted pile in the treatment of pile length and the improvement and reduction of indicators of different layers along the depth direction. However, the correlation between the static penetration and the compaction coefficient commonly used in the current norms still needs to be further studied to enhance the correlation analysis with detection parameters. [ABSTRACT FROM AUTHOR]

The effect of soil fixation and anti-scour instability of slope vegetation generally depends on the strength and anti-disintegration ability of slope soil due to increase of root system. Therefore, it is particularly necessary to study the disintegration characteristics of expansive soil related to slope instability under acidic conditions (simulated acid rain). In this paper, the response surface method (RSM) was used with the pH value, root diameter, root length, root coefficient, and distribution as independent variables, and the disintegration amount of root-soil (DARS) after 60min as the response value. Then X-ray diffractometer (XRD) was used to analyze the mineral composition changes of the sample under this environment. Simultaneously, the plasticity index of expansive soil at different values of pH was studied to discuss the disintegration mechanism of root compound expansive soil in an acid environments. The results show that the root system improves the anti-disintegration characteristics of the root-soil, and the effects of various factors on the amount of disintegration were as follows: root length > pH value > root distribution > root amount > root diameter. The DARS with a length of 20mm increased by 26.67% and 41.56% compared to the 30mm and 40mm. Compared to the horizontal distribution and horizontal + slant distribution, the DARS with slant distribution was increases by 11.39% and 20.24% respectively. The DARS with 2 roots is increased by 9.92% and 16.75% compared to 4 and 6 roots respectively. The 1mm diameter DARS is 6.65% and 15.49% higher than the 2mm and 3mm, respectively. In addition, an acidic environments can lead to an increase in the amount of disintegration or rate of disintegration. The disintegration at pH = 4.2 was increased by 11.4% and 22.4% compared to pH = 5.6 and pH = 7, respectively. The acidity affects soil disintegration is due to the hydrophilic minerals in the expansive soil react with H+ ion in the acid solution to form soluble salts. Due to the dissociation and leaching of free quartz and metal oxides in the soil to varying degrees, the ability of expansive soil to accumulate is reduced. The intensity of erosion and leaching decreases with increasing pH. In addition, the pH value can affects the plasticity index of the soil, which increases with the increasing pH, thus affects the disintegration properties of the expansive soil. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the corrosion behavior of Q235 steel in the bentonite-based resistance-reducing agent (RRA) with different infiltration rates of underground water. Design/methodology/approach: The corrosion behavior of the steel in underground water was assessed by weight loss experiment, electrochemical impedance spectroscopy and polarization curve. Findings: The results showed that the corrosion rate of the steel in the RRA pastes was much lower than that in the original acidic soil. The underground water infiltration slightly accelerated the corrosion rate of the steel in the RRA pastes, but the acceleration role is weak. The bentonite-based RRA can be compatibly applied in the acidic soil. Originality/value: The bentonite-based RRA can significantly reduce the corrosion rate of the steel and is suitable to compatibly apply in the acidic soil. [ABSTRACT FROM AUTHOR]

This paper aims to assess the durability of one-part geopolymer (OPG) pastes exposed to acidic environments. Two different acids (HCl and H2SO4) with different pH values (pH of 2, 4, and 6) were used to simulate the acidic environment in the current study. Acid resistance of the OPG paste activated by sodium hydroxide [NaOH (NH)] and sodium metasilicate [ Na2SiO3 (NS)], respectively, was assessed in terms of pH variation, mass change, visual appearance, deterioration depth, and compressive strength loss for varied immersion periods (∼120 days). The scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) and mercury intrusion porosimetry (MIP) tests were employed to investigate the evolution of porosity, morphological change, and hydrate composition for the varied immersion times. The experimental results revealed that due to the formation of a dense structure, the NS-activated OPG paste had better resistance to the acid attack compared with the NH-activated paste. It was also found that the gypsum crystals formed in the sample immersed in H2SO4 solution could fill the open pores and adhere to the surface of the sample, which reduced the further acid attack to some extent. However, the expansion properties of gypsums would lead to a loss of mechanical performance at the later immersion period. Furthermore, higher porosity of the OPG paste developed as the pH value of the acid solution decreased, thereby inducing the loss of mass and compressive strength and the increase of deterioration depth. Finally, as the immersion age and acid concentration increased, decalcification in the sample tended to occur, which caused a greater loss of compressive strength and a higher porosity. The outcome of this study could provide guidance for the application of the novel material in acid soil layer improvements or acid-resistant geotechnical structures. [ABSTRACT FROM AUTHOR]

Liming is one of the key agronomic practices to improve crop yields in acid soils because, among other things, it reduces aluminum toxicity and creates favorable conditions for crop growth. For an effective liming program, the methods to determine lime requirement should be as precise as possible. This paper reviews the existing lime requirement methods and discusses the potential of a new one suitable for routine use in the laboratory to test most agricultural soils. The most widely used lime requirement methods can be categorized into four groups: titration, incubation, buffer, and field methods. Other methods such as spectroscopy method or the use of empirical equations have also been adopted. Although some methods are highly reliable, they are not optimal for routine use because they are inconvenient during the laboratory procedures or cannot be validated for all conditions. Based on the linearity between soil pH and the added base in the pH range from 4.5–6.5 in most agricultural soils, a titration‐based method on 1:1 soil:0.01 M CaCl2 slurry of a single sample appears to be a promising candidate for routine use. In further studies, this generally applicable method should be evaluated to provide a better comparison to established methods for lime requirement determination. [ABSTRACT FROM AUTHOR]

Aluminum toxicity in acidic soil has become one of the main factors limiting crop growth and yield. Rapeseed is an important oil crop in China, which is mainly planted in the provinces and regions of the Yangtze River Basin where soil acidification is more serious. Rapeseed is one of the crops sensitive to aluminum toxicity, but the mechanisms of aluminum tolerance are still poorly understood. This paper reviewed the production of aluminum toxicity, the effect of aluminum toxicity on crop growth, the mechanism of crop aluminum tolerance, and the research progress on aluminum tolerance of rapeseed, and provide reference for the cultivation of new varieties of aluminum tolerant and high yielding rapeseed. [ABSTRACT FROM AUTHOR]

Aggregates are the basic structural units of soil; therefore, understanding the distribution and speciation of heavy metals (HMs) in soil aggregates is crucial for the clarification of the environmental behaviour of HMs. In this paper, seven soil profiles from different climatic type regions were sampled and grouped into six size aggregates (>2, 2–1, 1–0.6, 0.6–0.25, 0.25–0.053, <0.053 mm) to determine the distribution and chemical speciation of Cd, Cu, Mn and Pb. The results showed that the vertical distribution of Cd, Cu, Mn and Pb was differed, and the content of total Cd and Pb was ranked in the same order at both subsoil and parent material layer. Although the proportion of <0.053 mm size aggregate was lowest in bulk soil, fine particles showed higher content of total HMs and higher per cent of labile form distribution. However, the contents of total HMs were not always positively correlated with the content of acid soluble or potentially labile fractions of HMs. Total contents of Cu and Mn in aggregates from acidic soils were high, but these two HMs only posed light ecological risk according to the risk assessment code values. Soil organic matter (SOM) and soil pH were involved in the speciation of HMs. Acid exchangeable fraction of Mn in aggregates showed a decreasing trend from alkaline to acidic soils, and SOM positively correlated with the content of oxidisable fraction. For Cd, Cu and Pb, the content of potentially labile fraction of Cu positively associated with the content of Pb potentially labile fraction, and the content of residual fraction of Cd were negatively correlated with the content of Cu residual fraction. [ABSTRACT FROM AUTHOR]

: Despite the determination of zinc (Zn) isotope in soil being undertaken by several laboratories worldwide, sample preparation steps are varied due to diverse soil properties and compositions. This paper proposes a widely applicable soil acid digestion procedure that has been thoroughly evaluated for both soil and geological reference materials. To ensure the general applicability of this method to large varieties of soil samples, synthetic multi‐element solutions of high matrix element: Zn ratios (M/Zn) were prepared by embracing all possible elemental compositions of forty‐three certified reference materials; the chemical preparation procedure was then tested and optimised using these synthetic solutions. Results show that the recovery rate of Zn could reach 99–100% after the pre‐treatment. Based on this method, the δ66/64Zn data relative to JMC‐Lyon 3‐0749L Zn of previously uncharacterised NIST reference materials (including SRM 2709a San Joaquin soil, SRM 2710a Montana Soil and SRM 2711 Montana Soil) and Chinese certified reference materials (GSS‐1a, GSS‐7a, GSS‐5, GSS‐8, GSS‐14, GSS‐18, GSS‐20, GSS‐24, GSS‐31) were measured using MC‐ICP‐MS with a range from ‐0.08‰ to 0.35‰. The Zn isotope compositions of twenty‐nine soil samples from twenty‐one provinces/municipalities across China were also analysed and were found to fall within typical ranges from ‐0.09‰ to 0.28‰. The intermediate precision of several pure Zn standard solutions was better than ± 0.05‰ (2s) over 22 months of measurement. This method and results are useful for comparison and calibration of data between laboratories as well as providing a solid reference soil dataset for future studies dealing with Zn isotopes. [ABSTRACT FROM AUTHOR]

The use of peracetic acid (PAA) in advanced oxidation processes has gained significant attention recently, but the knowledge of activating PAA to degrade polycyclic aromatic hydrocarbons (PAHs) is limited due to the variety and selectivity of reactive substances in PAA oxidation system. This paper presented the first systemically study on the degradation of PAHs by PAA activation in soil. It was found that heat-activated peracetic acid (heat/PAA) was capable of degrading phenanthrene (PHE) efficiently with degradation efficiency > 90 % within 30 min. Experimental results demonstrated that a series of reactive oxygen species (ROS) including organic radicals (RO•), hydroxyl radicals (HO•) and singlet oxygen (1O 2) were generated, while acetylperoxyl (CH 3 C(O)OO•) and acetyloxyl (CH 3 C(O)O•) radicals were primarily responsible for PHE degradation in soil. Further analysis shows that polymerization products such as diphenic acid, 2′-formyl-2-biphenylcarboxylic acid and other macromolecules were dominant products of PHE degradation, suggesting polymerization driving PHE degradation instead of the conventional mineralization process. Toxicity analysis shows that most of the polymerization products had less toxicity than that of PHE. These results indicate that PAA activation was a highly effective remediation method for PAHs contaminated soil, which also provided a novel mechanism for pollutant degradation with the PAA activation process for environmental remediation. [Display omitted] • The degradation of PAHs in soil by heat-activated peracetic acid was systematically studied. • Heat-activated peracetic acid was capable of degrading phenanthrene efficiently within 30 min. • CH 3 C(O)OO• and CH 3 C(O)O• were primarily responsible for phenanthrene degradation in soil. • Polymerization products and other macromolecules were dominant products of phenanthrene degradation. [ABSTRACT FROM AUTHOR]

To explore the differences and change rules of soil nutrients and enzyme activities in Larix gmelinii forest in the cold temperate zone, so as to provide scientific basis and data basis for in-depth understanding of forest ecosystem functions and future development trends in the cold temperate forest ecotone in China. In this paper, four different types of larch forest (Betula platyphylla -Larix gmelinii, Rhododendron dauricum-Larix gmelinii, Larix gmelinii, and Larix gmelinii plantation) in Heilongjiang Zhongyangzhan Black-Billed Capercaillie Nature Reserve were selected as the research objects. Sampling was carried out by season, and the soil. chemical properties and enzyme activities ( catalase, acid phosphatase, urease, sucrase and cellulase) were determined in different seasons, and the dynamic changes with seasons were also explored. Results showed that: (1) Soil chemical properties and enzyme activities were significantly different in different forest types and seasons, and the changing trends were also different to some extent. (2)Soil acid phosphatase was significantly affected by the contents of soil total P, total N and available K. Soil catalase was significantly positively correlated with the contents of total N, available N, available K and available P. Soil sucrase was mainly affected by the contents of available P and available N. Soil urease and cellulase were most affected by soil organic carbon content. (3)The principal component analysis showed that there were significant differences in soil enzyme activities and soil chemical properties among the four forest types, and first principal component 1 could explain more than 50% of the variance variables. The soil chemical properties and enzyme activities in different Larix gmelinii were significantly different with the seasons, which were related to the accumulation of litter and the difference of vegetation types. Soil enzyme activities were correlated with soil chemical properties to varying degrees. [ABSTRACT FROM AUTHOR]

The paper aimed at evaluating the effects of biochar (BC) produced by slow pyrolysis of vine pruning residue on soil physicochemical properties and tomato plant growth. A greenhouse experiment was conducted for 66 days, applying different treatments for 3 soil types, i.e., foliar fertilizer, BC (at a volumetric ratio between BC and soil of 20/80), BC + foliar fertilizer, and no treatments. Strongly alkaline BC (pH = 9.89 ± 0.01) had a significant beneficial effect on the growth performance of tomato plants sown in a strongly acidic soil (pH = 5.40 ± 0.02). The mean values of height, number of leaves, and collar diameter of plants grown in BC-amended soil without foliar treatment were up to 50% higher than those of plants grown in soil with the other treatments. This positive effect of BC on plant growth is due to the changes in the soil properties. The addition of BC led to increased values of electrical conductivity, pH, soluble and available nutrient concentration. Moreover, BC reduced soil bulk density by about 50%, resulting in improved plant root development and thus enhanced water and nutrient uptake. Accordingly, BC derived from vine pruning residues can improve soil quality and tomato plant growth, as well as reduce biomass residues. [ABSTRACT FROM AUTHOR]

The aim of the paper is to give an overview on the chemistry of soil organic carbon (SOC) affecting nutrient availability, the emission of greenhouse gases and detoxifying harmful substances in soil. Humic substances represent the stable part of SOC, accounting for between 50 and more than 80% of organically bound carbon in soil. Humic substances strongly affect the soil solution concentration of several plant nutrients and may increase P-, Fe-, and Cu- solubility, thereby increasing their plant availability. Soil organic carbon, mainly humic substances, can detoxify monomeric Al in acid soils, can strongly bind toxic heavy metals, making them unavailable to the plant roots, and may strongly bind a vast variety of harmful organic pollutants. Increasing SOC is an important goal in agriculture. The inclusion of mixtures of semi-perennial plant species and cultivars may strongly increase SOC and humic substance content in soils. To increase SOC, farmyard manure and its rotted or composted forms are superior compared to the separate application of straw and slurry to soil. The storage of carbon, mainly in organic form, in soils is very important in the context of the emission of greenhouse gases. Worldwide, soils release about 10 times more greenhouse gases compared to fossil fuel combustion. Small increments in SOC worldwide will strongly affect the concentration of atmospheric CO2. The public discussion on soil fertility and greenhouse gas emissionshas been politically controlled in a way that leaves the important and positive contribution of soil organic carbon and mainly humic substances partly misinterpreted and partly underestimated. [ABSTRACT FROM AUTHOR]

Although litter can regulate the global climate by influencing soil N2O fluxes, there is no consensus on the major drivers or their relative importance and how these impact at the global scale. In this paper, we conducted a meta-analysis of 21 global studies to quantify the impact of litter removal and litter doubling on soil N2O fluxes from forests. Overall, our results showed that litter removal significantly reduced soil N2O fluxes (−19.0%), while a doubling of the amount of litter significantly increased soil N2O fluxes (30.3%), based on the results of a small number of studies. Litter removal decreased the N2O fluxes from tropical forest and temperate forest. The warmer the climate, the greater the soil acidity, and the larger the soil C:N ratio, the greater the impact on N2O emissions, which was particularly evident in tropical forest ecosystems. The decreases in soil N2O fluxes associated with litter removal were greater in acid soils (pH < 6.5) or soils with a C:N > 15. Litter removal decreased soil N2O fluxes from coniferous forests (−21.8%) and broad-leaved forests (−17.2%) but had no significant effect in mixed forests. Soil N2O fluxes were significantly reduced in experiments where the duration of litter removal was <1 year. These results showed that modifications in ecosystem N2O fluxes due to changes in the ground litter vary with forest type and need to be considered when evaluating current and future greenhouse gas budgets. [ABSTRACT FROM AUTHOR]

Degraded soils (including salinized, eroded, and low organic matter) resulting from natural and human effects are universal in arid and semi-arid regions all over the world. Bentonite and humic acid (BHA) are increasingly being tested to remediate these degraded lands, with potential benefits on crop production and soil health. A field study was conducted to quantify the effects of BHA application at six rates (0, 6, 12, 18, 24, and 30 Mg ha−1) on (i) dynamic changes in soil properties and (ii) oat crop productivity parameters in a dryland farming ecosystem. The specific objective of this paper was to determine the residual effects four to five years after a one-time BHA application on soil health and crop performance. The findings demonstrated that with the increasing rates of one-time BHA application, soil profile water storage displayed a piecewise linear plus plateau increase, whereas soil electrical conductivity, pH, and bulk density were all reduced significantly (p < 0.05) in the 0–20 cm and 20–60 cm layers. The improved soil environments gave rise to an increased activity of soil enzymes urease, invertase, and catalase that, respectively, reached peak values of 97%, 37%, and 32% of the control at the rates of 18 to 24 Mg BHA ha−1. In turn, this boosted soil nutrient turnover, leading to a 40% higher soil available P. Compared with the control treatment, application of BHA at the estimated optimum rate (roughly 24 Mg ha−1) increased grain yield by 20%, protein yield by 62%, water use efficiency by 41%, and partial factor productivity of N by 20%. The results of this study indicated for the first time that a one-time BHA application would be a new and effective strategy to combat land degradation and drought, and promote a sustainable soil micro-ecological environment in dryland agroecosystems under a varying climate scenario. [ABSTRACT FROM AUTHOR]

This paper presents a deep analysis of the accessory genome of an economically promising strain of Ensifer (Sinorhizobium) meliloti, L6-AK89, obtained as a result of next-generation high-throughput sequencing (MiSeq, MinIon). Strain L6-AK89 is a StrR mutant of the native strain CIAM1775, a symbiont of Medicago lupulina that adapted to a saline and arid habitat in NW Kazakhstan. CIAM1775 is an effective inoculant of M. lupulina cv. Mira (fodder type standard), cultivated on moderately acid soils in the NW agricultural region of Russia. Strain L6-AK89 makes it possible to obtain the expected high (>150%) increases in dry mass of the same plant variety in plant tests. The L6-AK89 genome has an increased proportion of sequences related to the accessory elements relative to reference strain Rm1021, 7.4% versus 4.8%. A set of 53 nod/noe/nol/nif/fdx/fix genes and 32 genes involved in stress tolerance together with 16S rRNA and recA–atpD–glnII–gyrB–dnaJ were evaluated. The high symbiotic efficiency of L6-АК89 with hop clover is most likely due to unique features of its genome, in combination with structural differences in its nod and stress-related genes, as well as unique clusters of quorum-sensing genes and osmoprotector synthesis. [ABSTRACT FROM AUTHOR]

The current opinion and position paper highlights (1) correct assignation of indicator phospholipid fatty acids (PLFA), (2) specificity and recycling of PLFA in microorganisms, and (3) complete extraction and detection of PLFA. The straight-chain PLFA 14:0, 15:0, 16:0, and 17:0 occur in all microorganisms, i.e., also in fungi and not only in bacteria. If the phylum Actinobacteria is excluded from the group of Gram-positive bacteria, all remaining bacteria belong to the bacterial phylum Firmicutes, which should be considered. The PLFA 16:1ω5 should be used as an indicator for the biomass of arbuscular mycorrhizal fungi (AMF) as there is no experimental evidence that they occur in marked amounts in Gram-negative bacteria. Fungal PLFA should embrace the AMF-specific 16:1ω5. In the presence of plants, ergosterol should be used instead of the PLFA 18:2ω6,9 and 18:1ω9 as fungal indicators for Mucoromycotina, Ascomycota, and Basidiomycota. The majority of indicator PLFA are not fully specific for a certain microbial group. This problem might be intensified by recycling processes during decomposition to an unknown extent. Soil handling and extraction conditions should be further optimized. The reliability and accuracy of gas chromatographic separation need to be regularly checked against unintentional variations. PLFA analysis will still be of interest over the next decades as an important independent control of DNA-based methods. [ABSTRACT FROM AUTHOR]

The paper deals with of the relations between the forest ecosystem, calcareous rocks and content and composition of soil organic matter in the Golo Bardo area in West Bulgaria. In that area Rendzinas are used mainly for forestry, viticulture and pastures. A specific study based on the accumulation of soil organic matter according to the data on the composition of the soil organic acids. The research on the soil organic matter composition provided information on the course of the humification processes in studied soils. Soil organic matter accumulation in Rendzinas depends on different factors, such as land use and climatic conditions. Soil has rapid transformations of organic residues and strongly decomposed plant tissue predominates. There are often signs of active work of the soil mesofauna. Studied soils have good reserves of organic carbon high degree of humification. The organic carbon content varies in a wide range from 0.8 to 7.2 %. The humic acids prevail over fulvic acids, and the degree of humification is higher in deeper horizons. According to the C/N ratio the humus type is Mull in almost all horizons. Studied soils are biologically active that have favorable impact over the soil structure and vegetation. Rendzinas have high potential of organic carbon sequestration. [ABSTRACT FROM AUTHOR]

The paper presents a synthesis of the research consisting in a complex capitalization of a brucitic limestone deposit from Romania, in environmental protection, respectively of the complex processing possibilities for using the final products could in a very well defined direction such as: the getting of MgO with 99% purity from a brucitic concentrate with 38-40% MgO content; the getting of a fertilizer containing struvite, limestone and microelements with benefit effects on the acid soils amelioration and on plants growth. The research allowed the establishing of a complex system of three technologies, respectively, one of brucitic limestone processing, the second of magnesia obtaining by brucitic concentrate leaching with carbon dioxide and the third, that of getting a double-role agricultural fertilizer (manure for plants growth and acid soils neutralizer). [ABSTRACT FROM AUTHOR]

[Objectives] This paper was aimed to study the remediation effects of phosphate-solubilizing fungi and bone char in different soils. [Methods] Three different types of lead-contaminated soils (neutral yellow brown soil, alkaline sand soil and acidic red soil)were mixed with the bone char sintered at different temperatures. We measured the contents of phosphorus and lead, and the remediation differences of different soils. The Pb bioavailability of lead-contaminated soil was then determined by planting non-heading Chinese cabbage. The application potential of compound remediation materials was confirmed by adding compound remediation agents to the soil with the best remediation effect. [Results] The bone char had the best effect of promoting the release of phosphorus in yellow brown soil, and the available phosphorus content was 64 times higher than that of the control, showing a high potential of lead remediation. The pH of yellow brown soil was neutral, and the available P in the soil would not be fixed by Ca, Fe, Al, etc., thus increasing the probability of its reaction with Pb. When bone char was solely used, the material treated at 200-300 ℃ had qualified remediation effect. We planted non-heading Chinese cabbage to verify the bioavailability of lead in yellow brown soil after bone char application. It was observed that addition of a certain proportion of bone char to yellow brown soil (the initial mass ratio of bone char to lead was over 0.5:1) could not only increase the absorption of phosphorus by 2.0 to 3.5 times, but also reduce the absorption of lead by non-heading Chinese cabbage(content of lead in pakchoi leaves was reduced by 70% to 80% compared with blank treatment). A composite of bone char and Aspergillus niger was further applied to yellow brown soil, and the effective lead was reduced to 14.36 mg·kg-1. In particular, the growth of the A. niger proved the remediation potential of the composite. [Conclusions] The composite of bone char and A. niger was suitable for lead remediation in neutral soils, and the suitable heating temperature for preparing bone char was 200-300 ℃. [ABSTRACT FROM AUTHOR]

Public concerns over environmental protection have increased after Fukushima accident. The soil-plant transfer factor (Fv) is a critical parameter for environmental risk assessment. 137Cs Fv values determined in acid Brazilian soils could be two orders of magnitude higher than Fv values measured in soils affected by the Chernobyl accident. This paper studied the behaviour of 90Sr in Brazilian soils where very few 90Sr Fv data is available. All classes of studied soils (Ferralsol, Acrisol and Nitisol) showed that more than 80% of total 90Sr in soils remains potentially mobile, mainly at the bioavailable phase, more than 2 years after soil contamination in an experiment conducted in lysimeters. Higher 90Sr Fv for maize and cabbage was observed in the acid soils with low content of exchangeable Ca, lower Fv values occurred at Nitisol, the subtropical soil type. It seems that the behaviour of 90Sr in these soils are mainly controlled by ionic competition mechanisms occurring for root uptake and sorption sites, with stable Sr and major nutrients (Ca, Mg and K). The mineralogy also seems to play a relevant role, since goethite rich clay soil presented 90Sr Fv values higher one or two orders of magnitude than 90Sr Fv values observed at clayed soil goethite rich with trace of vermiculite, for all studied crops. The high rate of 90Sr migration down the soil profiles observed for the studied soils during the 2 first years after contamination suggests a high rate of transfer to groundwater, even transfer to leafy crop group can be also a relevant pathway. In the present study, maize, among other plant species, presented the lowest Fv values, even when compared with maize cultivated in temperate soil. Our results suggest that stable Sr may not be a very good analogue of 90Sr for determining plant Fv values: geometric mean of stable Sr Fv for maize was Fv maize = 6.3E-1 ± 2.1E0 (n = 8) and for 90Sr was Fv maize = 1.8E-2 ± 2.5E0 (n = 16), geometric mean of stable Sr Fv for cabbage was Fv cabbage = 1.4E0 ± 3.9E0 (n = 17) and for 90Sr was Fv cabbage = 7.9E-1 ± 4.4E0 (n = 18). [Display omitted] • Transfer of 90Sr and stable-Sr was studied in Brazilian soils. • 90Sr in Brazilian soils (Ferralsol, Nitisol, Acrisol) had a high potential mobility. • Mineralogy plays a key role in determining 90Sr availability for plant uptake. • Stable-Sr is not a good analogue for 90Sr plant uptake. • A high rate of 90Sr migration down the soil profile was observed. [ABSTRACT FROM AUTHOR]

Sustained high yields of tea rely on the supply of nitrogen (N) from soil reserves, typically maintained by N fertilisation from inorganic or organic sources. This paper describes how soil N levels, including the effects of soil organic content and pH, were developed and incorporated into a crop yield simulation model called CUPPA-Tea. The nitrogen dynamics are presented in terms of i) the initial nitrogen stocks, ii) the addition of nitrogen to the system, iii) the uptake, use and loss of nitrogen by tea plants, and iv) nitrogen flows within the soil. CUPPA-Tea was then calibrated and validated using measured tea yields from Tanzania and Kenya. After integrating a wide range of nitrogen algorithms, the model explained 79% of the variation in annual yields within a nitrogen and irrigation experiment in Tanzania and a fertilizer experiment in Kenya. The slope of the relationship was 0.84 and 0.73 respectively, the root mean square error was 660 kg ha−1 and 507 kg ha−1, and the modelling efficiency was 0.77 and 0.75 respectively. The model predicted that in the absence of N application, tea yields would be higher from a site with a high rather than a low soil organic content. By contrast, at high levels of mineral N application, the yield response in the model was not sensitive to the soil organic content. Hence within the model, a site in Tanzania with a low soil organic content of 1.6% showed a greater yield response to applied mineral N than a site in Kenya where the soil organic carbon was 4.0%. The model also predicted small losses of N from the cropping system through denitrification and leaching due to the acidic soil conditions (pH < 4.5) and an assumed tea rooting depth between 300 and 500 cm. In Tanzania, irrigation was predicted to result in around 10% higher nitrogen uptake than under unirrigated conditions. The use of the CUPPA-Tea model can be useful in supporting decision making and improving the accuracy of tea yield estimates, as well as predictions of N fate within the soil-plant-atmosphere continuum. [Display omitted] • N dynamics, including the effects of soil organic content and pH, were developed and incorporated into the CUPPA-Tea model. • The resulting model explained 79% of the variation in tea yields from experiments in Tanzania and Kenya. • Under no N fertilizer, the model predicted greater yields in a site with a high rather than a low soil organic content. • Minimal N losses due to volatilisation, denitrification, and leaching were predicted (at pH 4.0–4.5 and rooting depths 3–5 m) • CUPPA-Tea was also used to identify the financially optimum N fertilizer application rate in pruned and unpruned tea. [ABSTRACT FROM AUTHOR]

Soil amendments, including lime, biochar, industrial by-products, manure, and straw are used to alleviate soil acidification and improve crop productivity. Quantitative insight in the effect of these amendments on soil pH is limited, hampering their appropriate use. Until now, there is no comprehensive evaluation of the effects of soil amendments on soil acidity and yield, accounting for differences in soil properties. We synthesized 832 observations from 142 papers to explore the impact of these amendments on crop yield, soil pH and soil properties, focusing on acidic soils with a pH value below 6.5. Application of lime, biochar, by-products, manure, straw and combinations of them significantly increased soil pH by 15%, 12%, 15%, 13%, 5% and 17%, and increased crop yield by 29%, 57%, 50%, 55%, 9%, and 52%, respectively. The increase of soil pH was positively correlated with the increase in crop yield, but the relationship varied among crop types. The most substantial increases in soil pH and yield in response to soil amendments were found under long-term applications (>6 year) in strongly acidic (pH < 5.0) sandy soils with a low cation exchange capacity (CEC, <100 mmol c kg−1) and low soil organic matter content (SOM, <12 g kg−1). Most amendments increased soil CEC, SOM and base saturation (BS) and decreased soil bulk density (BD), but lime application increased soil BD (1%) induced by soil compaction. Soil pH and yield were positively correlated with CEC, SOM and BS, while yield declined when soils became compacted. Considering the impact of the amendments on soil pH, soil properties and crop yield as well as their costs, the addition of lime, manure and straw seem most appropriate in acidic soils with an initial pH range from <5.0, 5.0–6.0 and 6.0–6.5, respectively. [Display omitted] • Soil amendments increased soil pH and crop yield by ca. 13% and 36%, respectively. • Amendments increased soil CEC, OM and base saturation and decreased bulk density. • Lime is the most economical while biochar is the most expensive for raising pH. • Lime, manure and straw are recommended at pH < 5.0, 5.0–6.0 and 6.0–6.5, respectively. [ABSTRACT FROM AUTHOR]

Aluminum (Al) is the most prevalent element in the earth crust and is toxic to plants in acidic soils. However, plants can address Al toxicity through external exclusion (which prevents Al from entering roots) and internal detoxification (which counterbalances the toxic-Al absorbed by roots). Nowadays, certain categories of exogenously added regulatory factors (EARF), such as nutritional elements, organic acids, amino acids, phytohormones, or biochar, etc. play a critical role in reducing the bioavailability/toxicity of Al in plants. Numerous studies suggest that regulating factors against Al toxicity mediate the expression of Al-responsive genes and transcription factors, thereby regulating the secretion of organic acids, alkalizing rhizosphere pH, modulating cell wall (CW) modifications, improving antioxidant defense systems, and promoting the compartmentalization of non-toxic Al within intracellular. This review primarily discusses recent and older published papers to demonstrate the basic concepts of Al phytotoxicity. Furthermore, we provide a comprehensive explanation of the crucial roles of EARF-induced responses against Al toxicity in plants. This information may serve as a foundation for improving plant resistance to Al and enhancing the growth of susceptible species in acidic soils. And this review holds significant theoretical significance for EARF to improve the quality of acidic soils cultivated land, increase crop yield and quality, and ensure food security. [Display omitted] • EARF influences rhizosphere pH and Al availability, reduces its absorption by root. • EARF regulates organic acids secretions in the tolerance to Al toxicity. • EARF modulates Al toxicity by reducing Al deposition in cell wall. • EARF protects Al-induced inhibition by regulating antioxidant defense system. • EARF chelates and separates Al to vacuoles to reduce its toxicity. [ABSTRACT FROM AUTHOR]

Soil physiochemical properties play a vital role in bioaccessibility-based health risk assessment as it can determine the bioaccessibility and the true risk of potentially toxic elements in soil. However, the effects of soil properties on bioaccessibility still remains unclear. In this paper, 17 of the 1454 literatures with 474 samples were identified, screened and reviewed for exploring the correlation between soil physicochemical properties and lead bioaccessibility (BAc Pb) through a meta-analysis approach. Five soil physicochemical parameters including pH, SOM, Clay, CEC and T-Pb were systematically analyzed using Principal component analysis, Pearson correlation analysis and survival analysis. The results showed that pH of simulated gastric juice is a major source of heterogeneity of the correlation between soil pH and BAc Pb. In the gastric phase, the effect of alkaline soil on high BAc Pb (BAc >50%) is more sensitive, and the effect of acidic soil on low BAc Pb (BAc <50%) is more sensitive. However, in the small intestinal phase, soil pH displays little impacts on BAc Pb in acidic, alkaline and neutral soils. Although three principal components explained 66.2% and 64.9% of the total variance of the urban, agricultural, and mining soils in gastric and small intestinal phases, respectively, there was no strong evidence that soil type can influence the BAc Pb. The results of present study provide insights into the correlation between soil properties and BAc Pb , and prediction of the bioaccessibility and bioavailability of Pb in different types of soil. [Display omitted] • A meta-analysis of correlation between soil properties and BAc Pb was performed. • Five soil parameters pH, SOM, Clay, CEC and T-Pb were systematically analyzed. • BAc Pb can be greatly influenced by soil pH in gastric and small intestinal phases. • pH of gastric juice is a major source of heterogeneity for soil pH and BAc Pb. [ABSTRACT FROM AUTHOR]

This paper presents a closure to "Full-Scale Field Studies to Evaluate Deep Soil Mixing in Stabilizing Expansive Soils" by Anand J. Puppala, Raja S. Madhyannapu, and Soheil Nazarain. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002647. The discusser pointed out that the presence of alkalines and acids in the soil or groundwater could influence the performance of deep soil mixing based on lime and cement stabilizers. [Extracted from the article]

Responsible editor: Edward Brzostek, Ph.D. B Correction to: Biogeochemistry (2022) 162:79-95 b https://doi.org/10.1007/s10533-022-00990-0 The paper was updated as the phrase: "Furthermore, actinobacteria with the alkB gene were shown to be able to grow on n-alkanes with lengths ranging from C10 to C19 as their sole source of carbon and energy (Ratajczak et al. 1998; Gibu et al. 2019)." Should be corrected to: "Furthermore, actinobacteria and proteobacteria with the alkB gene were shown to be able to grow on n-alkanes with lengths ranging from C10 to C19 as their sole source of carbon and energy (Ratajczak et al. 1998; Gibu et al. 2019)". [Extracted from the article]

• The Pre-Eifelian paleosol on rhyolite demonstrates surprisingly deep development. • Rhyolite contains allochthonous substituted by pyrite inclusions of nematophyte. • Pyrite oxidation drives the acid sulfate paleosol development. • Gypseous acid sulfate paleosol was developed under warm humid climate. During Late Devonian Voronezh Land was one of the main volcanic centers of Central Devonian Field. Earlier eruptions on the given territory have not been documented. This paper presents the detailed multidisciplinary study of the Pre-Eifelian paleosol developed from rhyolite lava deposited on the contact with the Proterozoic basement in Shkurlat granite quarry (Voronezh region, Russia). Discovered paleosol includes abundant coalified and partly substituted by pyrite allochthonous remnants of Nematasketum and Prototaxites. Main part of them had an outstanding preservation of tissues. Along with typical for rhyolite a quartz dominance, paleosol contains in situ developed kaolinite, gypsum, goethite, jarosite. Abundant Fe-nodules concentrated in the second half part of the shallow (∼50 cm) paleosol profile are composed of gypsum, goethite and metastable Fe-sulfates - jarosite and voltaite. Based on a complex of analytical characteristics, the discovered paleosol was attributed to acidic sulfate soil. The development of paleosol was initiated by pyrite oxidation which played the role of trigger. Being gypseous, paleosol bears the characteristics which are typical for paleosol of humid type. Based on geochemical data (CIA, CIA-K, PWI indexes) the obtained climatic parameters correspond to a subtropical climate with MAP 1200–1300 mm and MAT ∼ 17 °C. [ABSTRACT FROM AUTHOR]

In the subsurface environment, highly toxic hexavalent chromium (Cr(VI)) control and remediation are essential to avoid further ecological impacts and reduce environmental risks. This paper investigated the enhanced Cr(VI) electrokinetic removal in the soil through the approaching cathode method. Besides, a novel four-step sequential fractionation method was used to reflect the strength of Cr(VI) binding to the soil. The approaching cathode enhanced the electrokinetic delivery of surface-bound Cr(VI) by advancing the alkaline front for Cr(VI) desorption and improving the electric potential flattening of the soil layers. Desorption of Cr(VI) by the alkaline front involved converting the inner-sphere complexes form of Cr(VI) to a weakly adsorbed form susceptible to ionic strength. In addition, the acidic front provided a favorable environment for the photochemical reduction of Cr(VI) by soil species or the added citrate as the electron donors. Improving the potential distribution could regulate the energy consumption of individual soil layers and efficiently operate the electrokinetic transfer of pollutants. The work results have significant scientific and practical significance for applying the in-situ electrokinetic technique in subsurface pollution control. [Display omitted] • Cr(VI) forms bound to the soil were classified into four categories. • The approaching cathode improved potential flattening and Cr(VI) desorption. • Advancing the alkaline front could modulate system energy consumption distribution. • The acidic front supports photochemical reducing Cr(VI) within the anolyte and soil. [ABSTRACT FROM AUTHOR]

Aggregate-associated soil organic carbon (SOC) controls organic carbon stabilization. The research question of this paper was: what were the effects of conversion of forest land uses to agriculture at Ranchi, India on SOC pools, soil aggregation and aggregate-associated C? The samples were taken from six different land uses viz. native forest (NF), agri-horticulture (AH), native grass land (NG), rice-wheat (RW), rice- vegetable (RV) and maize-wheat (MW) from three soil depths (0–15, 15–30 and 30–45 cm). Soil aggregation, SOC pools and aggregate-associated C were determined. Results revealed that SOC concentration in NF was 36%, 67% and 127% higher than RW, RV and MW land uses, respectively, at 0–15 cm depth. The microbial biomass carbon (MBC) was higher in NF land uses than rice-based systems in the soil surface (0–15 cm) due to less disturbance. In surface soils (0–15 cm depth) under NF, the large macroaggregates had 21% and 40% higher SOC concentration than RW and RV, respectively. Similarly, NF soil had larger small macroaggregate-associated C than RW, RV and MW systems in the 0–15 and 15–30 cm layers. This result supports that tillage and regular crop removal under arable (MW, RW and RV) systems adversely affect loss of SOC contents in the surface layers and C storage inside aggregates, both in the 0–15 and 15–30 cm soil layers at Ranchi, India. • Conversion of native forest (NF) to rice-wheat (RW) system reduced total C by 36%. • Large macroaggregates of NF had ~21% and 40% higher total C than RW system. • RW system had higher C than rice-maize (RM) in the surface (0–15 cm) soils. • NF and grassed soils had higher soil aggregation and macroaggregates than RW. [ABSTRACT FROM AUTHOR]

Manure amendments to agricultural soils is an excellent opportunity for sustainable utilization of agricultural waste while providing multiple benefits to improve soil quality and increase the availability of nutrients to plants, including phosphorus (P). In this study, a meta-analysis of published data from 411 independent observations based on 133 peer-reviewed papers was performed for an in depth understanding of various factors affecting the transformation of soil P pools with manure application. Manure application increased all soil inorganic P (P i) by 58.0%–282% and organic P (P o) by 65.0%–105%, while decreasing P o /total P (TP), compared to those in unamended soils. Manure types, soil TP, and manure application rates were the important factors that influenced soil P fractions. Elevation of soil labile P i was more pronounced with compost application, while poultry and pig manure were more beneficial for promoting soil P i fractions and stable P o contents compared with other manure types. The manure application rate had pronounced effect on increasing the stable P o fractions. The effects of manure application on increasing soil P fractions were greater in soils with lower TP contents as compared to that in high TP soils. Manure effects on enhancing soil labile P i and moderately labile P i were greater in acidic soil than that in neutral and alkaline soils. In addition, soil P fractions showed significant correlation with latitude and mean annual precipitation (MAP). By integrating the impacts of manure types, soil properties, and climate, this meta-analysis would help to develop the management of manure application in a specific region of agriculture as well as promote the interpretation of the interfering factors on the soil P fractions changes in the manure-amended soils. • Global P fractions were integrated analyzed in manured arable soils. • Manure application had negative effects on the ratio of P o /TP in arable soil. • P i fractions increase was more conspicuous in acidic soil after manure application. • The magnitude of stable P o fraction enhanced with manure application rate increased. • Manure is beneficial for accumulating soil P i fractions under temperate regions. [ABSTRACT FROM AUTHOR]

Low phosphate (Pi) availability and high aluminum (Al) toxicity constitute two major plant mineral nutritional stressors that limit plant productivity on acidic soils. Advances toward the identification of genes and signaling networks that are involved in both stresses in model plants such as Arabidopsis thaliana and rice (Oryza sativa), and in other plants as well have revealed that some factors such as organic acids (OAs), cell wall properties, phytohormones, and iron (Fe) homeostasis are interconnected with each other. Moreover, OAs are involved in recruiting of many plant-growth-promoting bacteria that are able to secrete both OAs and phosphatases to increase Pi availability and decrease Al toxicity. In this review paper, we summarize these mutual mechanisms by which plants deal with both Al toxicity and P starvation, with emphasis on OA secretion regulation, plant-growth-promoting bacteria, transcription factors, transporters, hormones, and cell wall-related kinases in the context of root development and root system architecture remodeling that plays a determinant role in improving P use efficiency and Al resistance on acidic soils. [ABSTRACT FROM AUTHOR]

• An operational method to map soil carbon content (SOC) is applied in Tuscany. • It is based on the combination of ground, ancillary and remote sensing datasets. • The method is tested versus all measurements and through a leave-one-out approach. • The final map reproduces the SOC observations and follows main ecosystem features. The organic carbon stored in the topsoil is an essential component of the global carbon cycle which should be quantified for a variety of purposes. The current paper proposes a new approach to map the amount of organic carbon stored in the 0.3 m topsoil (SOC), based on the statistical combination of a large number of ground observations with ancillary and remote sensing data. This approach is applied and tested in Tuscany, a region of Central Italy that is characterised by extremely diversified and heterogeneous environmental features. More than 3500 soil samples were collected and made available for the purpose, together with a soil map, meteorological data, a land use map and MODIS Normalised Difference Vegetation Index (NDVI) imagery. This information was processed by advanced statistical methods to yield a final map which describes the SOC spatial distribution in the region with a spatial resolution of 250 m. The map well reproduces the SOC variability in the region, showing higher SOC values for forests with respect to grasslands and croplands and SOC peaks related to peats and acidic soils. The accuracy assessment, carried out both versus all ground observations and by a leave-one-out cross validation strategy, testifies to the high quality of the SOC map, which has a global RMSE comprised between 17.5 and 32.3 t ha−1. The map is also accompanied by per-pixel estimates of error variance which are informative on the uncertainty of SOC prediction. [ABSTRACT FROM AUTHOR]

In this paper, the corrosion behaviors of a welded joint of X80 pipeline steel underneath disbonded coating in an acidic soil solution were studied through electrochemical measurements, SEM/EDS and 3D ultra-depth microscopy. The results showed that the corrosion rates of the heat affecting zone (HAZ) specimens were the largest during the experiment, while the smallest corrosion rates always appeared with the base metal (BM) specimens at the same position. The corrosion rate of all the specimens at the opening were always larger than those at the bottom of the disbanded coating during the whole experiment. General corrosion dominated the surface of all specimen at different position, with much nonuniform corrosion inlaying in it. The nonuniform corrosion sensitivity of the HAZ specimens was larger than that of the BM and welded zone (WZ) specimens, whether at the opening or at the bottom. Under the disbonded coating, the nonuniform corrosion sensitivity of the specimens firstly decreased with the distance from opening and increased at the bottom. The maximum corrosion fluctuation of the HAZ specimen was available at the opening. • Corrosion of X80 steel welded joint under a crevice in acidic solution were studied. • Maximum and minimum corrosion rate existed in the HAZ and BM, respectively. • Corrosion rate at the opening was larger than that at the bottom of the crevice. • Nonuniform corrosion sensitivity of HAZ was larger than that of the BM and WZ. [ABSTRACT FROM AUTHOR]