Search

Phosphorus (P) limitation in acidic soils is well known and P-use and -recovery efficiency (PUE and PRE) is quite low. Rhizosphere-based P management has been considered as a means of enhancing PUE in acidic rice soils, but no clear dynamic study on this context. Rice was grown in pots using different P-sources [rock-phosphate (RP), single-super-phosphate (SSP), compost, P solubilizing bacteria (PSB), PSB + RP, PSB + compost, and compost + PSB + RP] in acidic Inceptisols (pH 4.31). Additionally, a micro-plot field experiment validated the results, using control, SSP, RP, PSB, and PSB + RP. Available-P (AvlP) and pH were analyzed every 10-days, while acid-phosphomonoesterases activity (PHA) and P-uptake in every 30-days until harvest. AvlP was peaked at 20 days after transplanting (DAT) and decreased until harvest. Compost + PSB + RP maintained significantly higher AvlP, soil pH and PHA, while root volume was highest in SSP throughout the growing period, and Soil pH showed an asymptotic trend. The P-content and uptake in biomass showed the highest peak at 60DAT and gradually declined until harvest. The effects of SSP and compost + PSB + RP on grain yield, chlorophyll concentration index (CCI), grain P content and uptake were comparable, but PUE and PRE were higher in compost + PSB + RP. Similar result was also observed in micro-plot field experiment, wherein grain yield and P uptake were comparable in SSP broadcast and PSB + RP. The study clearly shows that the combined application of PSB with RP, compost, or both in a 50% reduced amount can maintain higher AvlP in rice in acidic soil compared to full dose SSP while achieving a comparable yield. [ABSTRACT FROM AUTHOR]

Biochar-based sulfidized nano-sized zero-valent iron (SNZVI/BC) can effectively immobilize cadmium (Cd) in contaminated paddy soils. However, the synergistic effects between biochar and SNZVI on Cd immobilization, as well as the underlying mechanisms remain unclear. Herein, a soil microcosm incubation experiment was performed to investigate the immobilization performance of SNZVI/BC towards Cd in the contaminated paddy soil. Results indicated that the addition of SNZVI/BC at a dosage of 3% significantly lessened the concentration of available Cd in the contaminated soil from 14.9 (without addition) to 9.9 mg kg−1 with an immobilization efficiency of 33.3%, indicating a synergistic effect. The sequential extraction results indicated that the proportion of the residual Cd in the contaminated soil increased from 8.1 to 10.3%, manifesting the transformation of the unstable Cd fractions to the steadier specie after application of SNZVI/BC. Also, the addition of SNZVI/BC increased soil pH, organic matter, and dissolved organic carbon, which significantly altered the bacterial community in the soil, enriching the relative abundances of functional microbes (e.g., Bacillus, Clostridium, and Desulfosporosinus). These functional microorganisms further facilitated the generation of ammonium, nitrate, and ferrous iron in the contaminated paddy soil, enhancing nutrients' availability. The direct interaction between SNZVI/BC and Cd2+, the altered soil physicochemical properties, and the responded bacterial community played important roles in Cd immobilization in the contaminated soil. Overall, the biochar-based SNZVI is a promising candidate for the effective immobilization of Cd and the improvement of nutrients' availability in the contaminated paddy soil. Highlights: Biochar-based sulfidized nano-sized zero-valent iron (SNZVI/BC) synergistically immobilized Cd in the contaminated soil. SNZVI/BC effectively enhanced nutrients' availability in the contaminated soil. Nitrate-, Iron-, and sulfate-reducing bacteria were enriched in the SNZVI/BC-treated soil. Precipitation and complexation played an important role in the immobilization of Cd. [ABSTRACT FROM AUTHOR]

Gamma irradiation is an emerging technique in agriculture with the potential to enhance the nutritional quality of forage crops and improve their adaptability to infertile environments. This study examined how different doses of gamma irradiation affected the nutrient content, calcium (Ca) and phosphorus (P) uptakes, and the in vitro digestibility of Pennisetum purpureum cv. Mott, a forage grass cultivated on acidic soil. The experiment involved the application of various gamma irradiation doses (0 Gy, 5 Gy, 10 Gy, 15 Gy, 20 Gy, 25 Gy, and 30 Gy). Four replications were done using a randomized block design, with 25 P. purpureum cv. Mott seeds in each repetition, totaling 700 seeds. The plants were grown in acidic soil with a pH of approximately 4.5-5. After two months of growth, the plants were harvested, and various parameters were analyzed. The research results indicated that the treatment had a significant effect on increasing organic matter content (p<0.01), NDF (neutral detergent fiber) (p<0.01), ADF (acid detergent fiber) (p<0.01), cellulose (p<0.01), hemicellulose (p<0.01), crude protein (p<0.01), crude fat (p<0.05), non-nitrogen-free extract (p<0.05), fiber fractions (p<0.01), nutrient digestibility (p<0.01), and fiber fraction digestibility (p<0.01). Overall, it can be concluded from this study that a gamma irradiation dose of 15 gy can enhance the nutritional content of P. purpureum cv. Mott cultivated on acidic soil and improves its utilization efficiency for livestock due to the increased digestibility. [ABSTRACT FROM AUTHOR]

Up to 70% of the nitrogen (N) fertilizer applied to agricultural soils is lost through microbially mediated processes, such as nitrification. This can be counteracted by synthetic and biological compounds that inhibit nitrification. However, for many biological nitrification inhibitors (BNIs), the interaction with soil properties, nitrifier specificity, and effective concentrations are unclear. Here, we investigated three synthetic nitrification inhibitors (SNIs) (DCD, DMPP, and nitrapyrin) and three BNIs [methyl 3(4-hydroxyphenyl) propionate (MHPP), methyl 3(4-hydroxyphenyl) acrylate (MHPA), and limonene] in two agricultural soils differing in pH and nitrifier communities. The efficacies of SNIs and BNIs were resilient to short-term pH changes in the neutral pH soil, whereas the efficacy of some BNIs increased by neutralizing the alkaline soil. Among the BNIs, MHPA showed the highest inhibition and was, together with MHPP, identified as a putative AOB/comammox-selective inhibitor. Additionally, MHPA and limonene effectively inhibited nitrification at concentrations comparable to those used for DCD. Moreover, we identified the effective concentrations at which 50% and 80% of inhibition is observed (EC50 and EC80) for the BNIs, and similar EC80 values were observed in both soils. Overall, our results show that these BNIs could potentially serve as effective alternatives to SNIs currently used. [ABSTRACT FROM AUTHOR]

Mixed plantations are garnering increased attention due to their potential to provide a broader array of benefits compared to monocultures. Although numerous studies have indicated promising complementarity between black spruce (Picea mariana) and tamarack (Larix laricina), few have delved into individual tree growth interactions to thoroughly assess early growth complementarity. We sampled 119 planted black spruce and their immediate environment to quantify and qualify any differences between two conditions in young plantations: mixed tamarack ("mixtures") and black spruce monocultures ("monocultures") within young plantations. We investigated the effect of neighbouring under four perspectives: tree competition, microenvironment, foliar nutrients, and soil nutrients. Our results showed increased values for black spruce foliar nitrogen total concentration, soil pH, and canopy closure in mixtures compared to monocultures. Furthermore, black spruce stem volume was increased by 38.1% in mixture compared to monoculture. Black spruce stem volume was negatively affected (86% decrease) by the combined effect of shrubs and non-crop trees under high competition pressure, despite the plantation being mechanically released in 2017. Collectively, our results suggest that black spruce growing in mixtures holds a greater growth potential than black spruce in monocultures. [ABSTRACT FROM AUTHOR]

Soil acidification is an issue for agriculture that requires effective management, typically in the form of lime (calcium carbonate, CaCO3), application. Mid infrared (MIR) spectroscopy methods offer an alternative to conventional laboratory methods, that may enable cost-effective and improved measurement of soil acidity and responses to liming, including detection of small–scale heterogeneity through the profile. Properties of an acidic soil following lime application were measured using both MIR spectroscopy with Partial Least Squares Regression (MIR-PLSR) and laboratory measurements to (a) compare the ability of each method to detect lime treatment effects on acidic soil, and (b) assess effects of the different treatments on selected soil properties. Soil properties including soil pH (in H2O and CaCl2), Aluminium (Al, exchangeable and extractable), cation exchange capacity (CEC) and organic carbon (OC) were measured at a single field trial receiving lime treatments differing in rate, source and incorporation. Model performance of MIR-PLSR prediction of the soil properties ranged from R2 = 0.582, RMSE = 2.023, RPIQ = 2.921 for Al (extractable) to R2 = 0.881, RMSE = 0.192, RPIQ = 5.729 for OC. MIR-PLSR predictions for pH (in H2O and CaCl2) were R2 = 0.739, RMSE = 0.287, RPIQ = 2.230 and R2 = 0.788, RMSE = 0.311, RPIQ = 1.897 respectively, and could detect a similar treatment effect compared to laboratory measurements. Treatment effects were not detected for MIR-PLSR-predicted values of CEC and both exchangeable and extractable Al. Findings support MIR-PLSR as a method of measuring soil pH to monitor effects of liming treatments on acidic soil to help inform precision agricultural management strategies, but suggests that some nuance and important information about treatment effects of lime on CEC and Al may be lost. Improvements to prediction model performance should be made to realise the full potential of this approach. [ABSTRACT FROM AUTHOR]

One of the soil properties most commonly measured to describe agronomic and biogeochemical conditions of soils is soil pH. Soil pH measures the concentration of exchangeable H + that resides in bulk soil samples using extractants in the laboratory and thus differs from porewater pH, which we define here as an in situ measure of porewater H + concentration in soil/weathering profiles. The difference between the two pH measurements is often not fully known for a given system but could lead to a misunderstanding of soil conditions if the two measurements are directly compared. Agricultural soils are one of the targeted loci for the application of enhanced weathering (EW), a technique aimed at counteracting increasing anthropogenic carbon dioxide from burning fossil fuels. An increase in pH is thought to be one of the key advantages of EW, given that the process can mitigate soil acidification and increase crop yields. As a result, fully evaluating the biogeochemical and agronomic consequences of EW approaches requires accurate simulation of both soil pH (pH s) and porewater pH (pH pw). This paper presents an updated version of the reactive transport code SCEPTER (Soil Cycles of Elements simulator for Predicting TERrestrial regulation of greenhouse gases), which enables simulation of bulk soil pH measurements in the laboratory, in addition to porewater pH, as measured in the field along with a more comprehensive representation of cation exchange with solid-phase constituents of bulk soil. We first describe the implementation of cation exchange in the SCEPTER model, then introduce conceptual modeling frameworks enabling the calculation of bulk pH s. The validity of the model is examined through comparison of model results with soil pH measurements from mesocosm experiments on maize production with crushed basalt amendments. Finally, illustrative example simulations are shown, demonstrating that a difference between pH s and pH pw can lead to significantly different estimates of soil alkalinization and carbon capture by EW for a given targeted pH in cropland systems. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of different long-term (36 years) fertilizer treatments on soil pH, exchangeable acids, exchangeable base cation and cation exchange capacity (CEC) at 0–10 cm and 10–20 cm soil layers in a double-cropping rice field. The following fertilizer treatments were included: chemical fertilizer (MF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without any fertilizer input as a control (CK). This result indicated that soil pH at 0–10 cm layer with RF and OM treatments was higher than that of MF and CK treatments. Soil exchangeable acidity content at 0–10 cm and 10–20 cm layers with RF and OM treatments were decreased by 48.4%, 51.6% and 49.2%, 54.2%, compared with CK treatment, respectively. Soil exchangeable calcium (Ca2+), magnesium (Mg2+) and potassium (K+) contents at 0–10 cm and 10–20 cm layers in paddy field with OM and RF treatments were higher than that of CK treatment. Moreover, compared with CK treatment, soil exchangeable base ion content at 0–10 cm and 10–20 cm layers in paddy field with OM treatment were increased by 54.1% and 42.6%, respectively. Soil CEC and effective cation exchange capacity (ECEC) at 0–10 cm and 10–20 cm layers with OM and RF treatments were significantly higher than that of MF and CK treatments. In conclusion, our results indicated that long-term application of crop residue or organic manure can improve soil exchangeable base ion and exchangeable capacity contents, alleviate soil acidity in a double-cropping paddy field. [ABSTRACT FROM AUTHOR]

90Sr, as a typical artificial radionuclide, poses a serious threat to human health and the ecological environment. The selective removal of this radionuclide from industrial nuclear waste is crucial for our environment. Here we report a novel potassium fluoroaluminate, K2[(AlF5)H2O], which was synthesized by a simple low‐temperature one‐step method. It adopts a 1D AlF6‐chain structure, which consists of exchangeable potassium ions in between the infinite chains of octahedral Al centers. As a remarkable inorganic ionic exchanger, K2[(AlF5)H2O] has a high chemical stability (resistance of pH=~3‐12) and thermal stability (≥~300 °C). It possesses an excellent adsorption selectivity (Kd=~6.1×104 mL ⋅ g−1) and a maximum adsorption capacity of qm=~120.32 mg ⋅ g−1 for Sr2+. Importantly, it still keep a very good selectivity for Sr2+ ions even in the presence of competing Na+, Mg2+ and Ca2+ aqueous solutions. K2[(AlF5)H2O] is the first example of fluoroaluminate ionic exchange materials that can capture Sr2+. This result opens up a new way to design and synthesize inorganic ionic exchangers for the selective removal of Sr2+ ions from radioactive waste water. [ABSTRACT FROM AUTHOR]

The estimation of the postmortem interval (PMI) is one of the key challenges for forensic anthropologists. Although there are several methods referenced for this purpose, none is sufficiently effective. One of the main reasons justifying the complexity of this task is the influence of several taphonomic factors. The study of the Luminol technique has stood out as a promising method for estimating PMI, complementing the existing methods, since it is an economic, easy and reproducible method that operates as a presumptive test. However, it is not known which taphonomic factors can influence the results obtained by this technique. The aim of this study is to test the influence of taphonomic factors, such as temperature, humidity, soil type and pH, on the estimation of the PMI by the Luminol technique. In order to test the influence of the referred factors, a sample consisting of 30 clavicles, with known and similar PMI, collected from autopsies, was distributed as evenly as possible by six vases and buried with different decomposition conditions for a period of 12 months. After the exhumation and sample preparation, the Luminol technique was applied. It was possible to clearly observe differences in the results. Thus, according to our research, it is possible to conclude that the results obtained by the application of Luminol are influenced by taphonomic factors. Therefore, the context in which a body is found should always be considered for applying this technique. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the adsorption of anionic dye represented by Congo red (CR) using adsorbents prepared starting from Wyoming montmorillonite (Mt). The first group of adsorbents named homoionic montmorillonite (HMt) was obtained using Ca2+, Mg2+, Na+, and K+, while the second group called modified montmorillonite (Mt-CTA) was acquired after intercalation of cetyltrimethylammonium (CTA+) into HMt. The obtained XRD results analysis revealed that Mt-K-2CEC gave a maximal d001 value of 19.07 Å due to a relatively high amount of CTA+ cations in the interlayer spaces of Mt-K. From BET measurements, total pore volume, average pore size, and the BET surface area decreased with the increase in CTA+ loading on montmorillonite from 1 to 2CEC, except for Mt-Ca. On the other hand, adsorption kinetics data showed accordance with the pseudo-second-order equation, and the adsorption isotherm was in good agreement with the Langmuir model. Up to 274.48 and 258.46 mg g−1 of the dissolved CR were adsorbed by Mt-Mg and Mt-Na-2CEC, respectively. Finally, as shown in the FTIR spectra and SEM analyses, the adsorption of organo-clays was explained as a chemical adsorption process between the groups –N=N– and –SO3 of CR and CTA+. Hence, the use of these adsorbent materials to remove CR dye is highly beneficial due to their abundance and low cost. [ABSTRACT FROM AUTHOR]

Soil quality monitoring schemes are a useful tool for assessing the potential of soils to perform desired services such as agricultural productivity. When researchers or other stakeholders wish to compare results between different schemes or studies, failure to consider differences in soil sample storage conditions presents a significant potential for error. Here, we compared levels of nitrogen and potassium, as well as pH, in agricultural soil samples stored under three different conditions (refrigerated, frozen, and oven‐dried). All tests were performed after 7 and 24 weeks of storage. Nitrate decreased significantly in dried (p < 0.001) samples. When refrigerated, nitrate first increased (p < 0.01) and then decreased (p < 0.001). Nitrate levels where unchanged at Week 7 in the freezer but decreased significantly at Week 24 (p < 0.001). Nitrite and ammonium increased after drying (p < 0.001) and when frozen (p < 0.001 and p < 0.05) but remained stable when refrigerated. There was no significant difference in potassium levels between the fresh control and Week 7 in the freezer, but potassium had increased at Week 24 (p < 0.05). Potassium concentration increased in refrigerated samples (p < 0.001) and fluctuated up and down in dried samples (p < 0.01). pH measurements fluctuated significantly in refrigerated and frozen samples (p < 0.001 and p < 0.01, respectively) but were unchanged in dried samples. We suggest that soil monitoring schemes standardize their sample storage, and we encourage researchers to clearly report soil sample storage conditions in publications, to improve transparency and reproducibility. Core Ideas: Storage of soil samples is inevitable for large‐scale soil monitoring or research projects.Different types of storage conditions affect measurements of soil physiochemical properties.We show that type of storage and duration impacts measured levels of nutrients and pH in soil samples.We recommend that researchers use consistent sample storage conditions for making spatial or temporal comparisons. [ABSTRACT FROM AUTHOR]

Plant–soil biodiversity interactions are fundamental for the functioning of terrestrial ecosystems. Yet, the existence of a set of globally distributed topsoil microbial and small invertebrate organisms consistently associated with land plants (i.e., their consistent soil‐borne microbiome), together with the environmental preferences and functional capabilities of these organisms, remains unknown. We conducted a standardized field survey under 150 species of land plants, including 58 species of bryophytes and 92 of vascular plants, across 124 locations from all continents. We found that, despite the immense biodiversity of soil organisms, the land plants evaluated only shared a small fraction (less than 1%) of all microbial and invertebrate taxa that were present across contrasting climatic and soil conditions and vegetation types. These consistent taxa were dominated by generalist decomposers and phagotrophs and their presence was positively correlated with the abundance of functional genes linked to mineralization. Finally, we showed that crossing environmental thresholds in aridity (aridity index of 0.65, i.e., the transition from mesic to dry ecosystems), soil pH (5.5; i.e., the transition from acidic to strongly acidic soils), and carbon (less than 2%, the lower limit of fertile soils) can result in drastic disruptions in the associations between land plants and soil organisms, with potential implications for the delivery of soil ecosystem processes under ongoing global environmental change. [ABSTRACT FROM AUTHOR]

The discovery of complete ammonia oxidizers (comammox) challenged our cognition of the nitrification process. Ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB) and comammox can carry out soil autotrophic nitrification process together. However, the differentiation of the ecological niche of three types of ammonia oxidizers in different environments has not been fully discovered. In this study, a typical black soil collected from northeast China was adjusted to different pH (original and adjusted pH were 4.29 and 7, respectively) and NH4+-N concentrations (weekly adding and without adding 100 mg NH4+-N kg− 1 soil). The activities of AOA, AOB and comammox were examined using DNA stable isotope probing approach with 13CO2, the phylogenetic information of active ammonia oxidizers was detected by high-throughput sequencing. The results showed that niche differentiation of AOA, AOB and comammox in black soils differed with soil pH. AOA dominated the nitrification process in acidic soils, while AOA, AOB and comammox Clade A taken part in the nitrification process in neutral soils. Among them, AOB showed strong activity in the soils with the high N treatment. The active AOA mainly belonged to Nitrososphaera in acidic and neutral soils. The active AOB and comammox Clade A mainly belonged to Nitrosospira and Clade A.2 in neutral soils, respectively. Taken together, the results highlighted the significance of canonical ammonia oxidizers in nitrification process of black soils, and comammox Clade A played an active role in neutral condition. [ABSTRACT FROM AUTHOR]

Soil pH significantly impacts microbial activity and community assembly, which in turn determines the temperature sensitivity (Q10) of soil respiration. Due to the high soil acidification in China, it is necessary to understand how soil acidification impacts Q10. Here, the Q10 of soil respiration was examined in a long-term field experiment (1982–present) with different soil pH caused by fertilization management. In this experiment, we selected treatments with neutral pH: (1) no crops and fertilization (CK); (2) crops without fertilization (NF); low pH with (3) crops with chemical fertilization (NPK); and (4) crops with chemical fertilization combined with wheat straw incorporation (WS). Under natural soil temperature changes, we observed that soil acidification lowered the Q10 value of soil respiration. Considering only temperature changes, the Q10 of soil respiration was strongly associated with microbial community composition, alpha diversity, and soil ammonium nitrogen. Considering the interaction between soil pH and temperature, warming strengthened the negative effect of soil pH on the Q10 of soil respiration, and the pathway through which soil pH mediated Q10 included not only microbial community composition, alpha diversity, and biomass but also the soil's available phosphorus. This work enhanced our insights into the relationships between Q10, temperature, and soil pH by identifying important microbial properties and key soil environmental factors. [ABSTRACT FROM AUTHOR]

Understanding soil phosphorus (P) distribution and its key drivers is fundamental for sustainable P management. In this study, a 21-year fertilization experiment on black soil was carried out, setting up five fertilization treatments: unfertilized control (CK), nitrogen and potassium (NK), nitrogen, P and potassium (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM). The distribution and effecting factors of P pools within soil aggregates were investigated. Compared to CK, the NK and NPK treatments decreased calcium-associated P concentration in all aggregate fractions. Meanwhile, the NPK treatment significantly increased the organic P extracted from NaOH in unaggregated particles (<0.053 mm). This was mainly due to the reduction in soil pH. The NPKS and NPKM treatments increased almost all P forms in aggregates, especially Ca-P. For the NPKM treatment, inorganic P extracted from resin, NaHCO3, and NaOH increased as aggregate size increased. This was mainly because straw or manure addition promoted soil organic carbon (SOC) storage in aggregates, creating more sorption sites via association with amorphous metallic minerals, and, thus, facilitating P accumulation. In conclusion, decreasing soil pH by chemical fertilizers is an effective strategy for mobilizing soil P, whereas increasing SOC by straw or manure facilitates P accumulation. [ABSTRACT FROM AUTHOR]

• γ-PGA-Ca drove the highest improvements in the pH buffering capacity (pHBC) of the soil and exhibited the greatest potential in inhibiting HNO3-induced soil acidification. • The mechanism of improving pHBC by PASP-Ca or γ-PGA-Ca were protonation of carboxyl, complexing with Al3+, and cation exchange processes. • CaLS was the optimal one in inhibiting acidification and increasing exchangeable acidity during incubation via nitrification inhibition. • The sharp reduction in the population sizes of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were responsible for inhibition of nitrification by CaLS application. Soil acidification is a major threat to agricultural sustainability in tropical and subtropical regions. Biodegradable and environmentally friendly materials, such as calcium lignosulfonate (CaLS), calcium poly(aspartic acid) (PASP-Ca), and calcium poly γ-glutamic acid (γ-PGA-Ca), are known to effectively ameliorate soil acidity. However, their effectiveness in inhibiting soil acidification has not been studied. This study aimed to evaluate the effect of CaLS, PASP-Ca, and γ-PGA-Ca on the resistance of soil toward acidification as directly and indirectly (i.e., via nitrification) caused by the application of HNO 3 and urea, respectively. For comparison, Ca(OH) 2 and lignin were used as the inorganic and organic controls, respectively. Among the materials, γ-PGA-Ca drove the substantial improvements in the pH buffering capacity (pHBC) of the soil and exhibited the greatest potential in inhibiting HNO 3 -induced soil acidification via protonation of carboxyl, complexing with Al3+, and cation exchange processes. Under acidification induced by urea, CaLS was the optimal one in inhibiting acidification and increasing exchangeable acidity during incubation. Furthermore, the sharp reduction in the population sizes of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) confirmed the inhibition of nitrification via CaLS application. Therefore, compared to improving soil pHBC, CaLS may play a more important role in suppressing indirect acidification. Overall, γ-PGA-Ca was superior to PASP-Ca and CaLS in enhancing the soil pHBC and the its resistance to acidification induced by HNO 3 addition, whereas CaLS was the best at suppressing urea-driven soil acidification by inhibiting nitrification. In conclusion, these results provide a reference for inhibiting soil re-acidification in intensive agricultural systems. [Display omitted] [ABSTRACT FROM AUTHOR]

• Total As, As fractions and phosphatase activity reached a significant level. • V max and V max / K m of phosphatase decreased with elevated As pollution. • V max and K m were significantly negatively correlated with soil pH. • Phosphatase is more sensitive to As contamination at the soil's pH. • V max / K m as an index of pollution degree in As field contaminated soil. The pollution and ecological risks posed by arsenic (As) entering the soil are the major environmental challenges faced by human beings. Soil phosphatase can serve as a useful indicator for assessing As contamination under specific soil pH conditions. However, the study of phosphatase kinetics in long-term field As-contaminated soil remains unclear, presenting a significant obstacle to the monitoring and evaluation of As pollution and toxicity. The purpose of this study was to determine phosphatase activity and explore enzyme kinetics in soils subjected to long-term field As contamination. Results revealed that the soil phosphatase activity varied among the tested soil samples, depending on the concentrations of As. The relationship between total As, As fractions and phosphatase activity was found to be significant through negative exponential function fitting. Kinetic parameters, including maximum reaction velocity (V max), Michaelis constant (K m) and catalytic efficiency (V max / K m), ranged from 3.14 × 10−2–53.88 × 10−2 mmol/(L·hr), 0.61–7.92 mmol/L, and 0.46 × 10−2–11.20 × 10−2 hr−1, respectively. V max and V max / K m of phosphatase decreased with increasing As pollution, while K m was less affected. Interestingly, V max / K m showed a significant negative correlation with all As fractions and total As. The ecological doses (ED 10) for the complete inhibition and partial inhibition models ranged from 0.22–70.33 mg/kg and 0.001–55.27 mg/kg, respectively, indicating that V max / K m can be used as an index for assessing As pollution in field-contaminated soil. This study demonstrated that the phosphatase kinetics parameters in the soil's pH system were better indicators than the optimal pH for evaluating the field ecotoxicity of As. [Display omitted] [ABSTRACT FROM AUTHOR]

Rootstocks are used in viticulture to manage plant pests and diseases, particularly phylloxera and root-knot nematodes, and to improve grape and wine production. A wide range of rootstocks are commercially available, making selecting the optimal rootstock a difficult decision. In particular, distinct rootstock genotypes may manifest varying degrees of tolerance or resistance to abiotic stress, necessitating meticulous consideration during the rootstock selection process. This article reviews characteristics of various commercial rootstocks, as well as rootstocks being developed in recent years. This review further discusses responses of rootstocks to drought, soil nutrients, and soil pH. This review mainly focuses on influence of rootstocks on physiology characteristics of grafted scions rather than berry yield and quality. The breadth of this review benefits both researchers and practitioners by providing comprehensive summery of rootstocks to inform selection and to guide future research. [ABSTRACT FROM AUTHOR]

Background: Cricket feces is a potential high-quality soil amendment, but there is currently no established optimum rate for its application in paddy soils with varying moisture contents. This study therefore aimed to evaluate the effects of varied rates of cricket feces on soil properties, rice growth and yield in paddy soils with differing moisture contents. Methods: Two study factors were evaluated: (i) the maximum water-holding capacity (WHCmax) and flooded soils and (ii) cricket feces applied at rates of 0 (unamended), 3.13 (low), 6.25 (medium) and 12.50 (high) t/ha. Result: The total grain weight of rice in soil with WHCmax was 2.60, 4.33, 6.91 and 7.49 g/hill under the cricket feces from unamended to high rates, respectively, with no significant difference between the medium and high rates. Meanwhile, the total grain weight in flooded soil was 1.85, 4.02, 4.70 and 5.72 g/hill, respectively. Cricket feces increased the content of essential elements and decreased the acidity and toxicity of Al, Ca and Na in the soil, thereby promoting rice growth and yield. The optimal application rates of cricket feces for rice in the WHCmax soil were determined to be the medium rate, while that in flooded soil was the high rate. [ABSTRACT FROM AUTHOR]

Forest litter decomposition is an essential component of global carbon and nutrient turnover. Invertebrates play important roles in litter decomposition, but the regional pattern of their effects is poorly understood. We examined 476 case studies across 93 sites and performed a meta‐analysis to estimate regional effects of invertebrates on forest litter decomposition. We then assessed how invertebrate diversity, climate and soil pH drive regional variations in invertebrate‐mediated decomposition. We found that (1) invertebrate contributions to litter decomposition are 1.4 times higher in tropical and subtropical forests than in forests elsewhere, with an overall contribution of 31% to global forest litter decomposition; and (2) termite diversity, together with warm, humid and acidic environments in the tropics and subtropics are positively associated with forest litter decomposition by invertebrates. Our results demonstrate the significant difference in invertebrate effects on mediating forest litter decomposition among regions. We demonstrate, also, the significance of termites in driving litter mass loss in the tropics and subtropics. These results are particularly pertinent in the tropics and subtropics where climate change and human disturbance threaten invertebrate biodiversity and the ecosystem services it provides. [ABSTRACT FROM AUTHOR]

Explaining diversity in tropical forests remains a challenge in community ecology. Theory tells us that species differences can stabilize communities by reducing competition, while species similarities can promote diversity by reducing fitness differences and thus prolonging the time to competitive exclusion. Combined, these processes may lead to clustering of species such that species are niche differentiated across clusters and share a niche within each cluster. Here, we characterize this partial niche differentiation in a tropical forest in Panama by measuring spatial clustering of woody plants and relating these clusters to local soil conditions. We find that species were spatially clustered and the clusters were associated with specific concentrations of soil nutrients, reflecting the existence of nutrient niches. Species were almost twice as likely to recruit in their own nutrient niche. A decision tree algorithm showed that local soil conditions correctly predicted the niche of the trees with up to 85% accuracy. Iron, zinc, phosphorus, manganese, and soil pH were among the best predictors of species clusters. [ABSTRACT FROM AUTHOR]

Electrokinetics has gained importance as a sustainable soil modification and remediation method for improving problematic sites. The formation of cracks during the electrokinetic treatment is an important concern during the field implementation of the process. Therefore, considering this, this study investigated the impact of a voltage gradient on the performance evaluation of electrokinetic consolidation clayey soil after adding a lime. The performance was evaluated regarding cumulative discharge, surface settlement, power consumption, reducing water content, alteration in soil pH, and crack formation. The surface settlement increases by 50% for the applied voltage gradient of 1.00 V/cm compared to that of 0.25 V/cm. The power consumption in the case of 1.00 V/cm after the addition of lime is 3.67 times compared to that without lime; however, the difference is insignificant for 0.50 V/cm. Further, the pH near the cathode increases to 10.94 from 7.81 after the addition of lime in the case of 0.50 V/cm. Finally, adding lime helps drastically reduce the surface crack formed during the electrokinetic treatment. [ABSTRACT FROM AUTHOR]

Soil ameliorants play a crucial role in enhancing soil fertility and rice (Oryza sativa L.) production in acidsulfate soils. This research aims to study the impact of Si-humic ameliorants on soil chemical properties, plant growth, Fe levels, and rice production in acid-sulfate soil. The experiments were conducted at the Laboratory and Greenhouse of the Indonesia Swampland Agricultural Research Institute. The greenhouse experiment adopted a factorial RCBD with Factor 1 representing the ameliorant formula type: 100% lime (F0), 30% commercial humate+30% rice husk ash+40% lime (F1), 30% water hyacinth humate+0% rice husk ash+40% lime (F2), 30% water hyacinth humate+30% rice husk biochar+40% lime (F3), 30% commercial humate+30% rice husk biochar+40% lime (F4), and control without ameliorant. Factor 2 represents dosage of soil ameliorant: 0, 1, 2, and 4 t ha-1. Observations included soil properties such as pH, exchangeable Fe, available P, plant growth, Fe toxicity, yield, and yield components. Silicon-humic soil ameliorant demonstrated the ability to enhance soil pH from 3.16 to 3.63, available P from 6.12 to 30.16 mg kg-1, and decrease Fe 690 to 371 mg kg-1. Specifically, the F3 Si-humate formulation alleviated Fe toxicity, enhanced P availability, promoted rice growth, and improved yield. The application of 4 t ha-1 Sihumate F3 had the best effect in increasing grain yield by 4.22 g pot-1 compared to the control. The application of Si-humate F3 not only improved soil quality and increased rice yields but also reduced the need for lime, contributing to the potential maintenance of soil health. [ABSTRACT FROM AUTHOR]

The processes of occupation and exploitation in the Amazon have been increasing, and as a consequence, forest areas are being replaced by agroecosystems. As a consequence of this change, changes have been occurring in the soil attributes, and consequently, in the stability of aggregates in these environments. Thus, this work had two objectives: the first was to evaluate the impacts generated by the conversion of forests into agroecosystems on the soil attributes that are related to aggregates, in the southwestern region of the Amazon; the second objective was to evaluate the roles of pedophysical and pedochemical parameters on the stability of soil aggregates. The study was carried out on rural properties located in the southern part of Amazonas State, Brazil. Eight areas under different agroecosystems were selected: in the municipality of Canutama: (i) annatto, (ii) guarana, and (iii) cupuassu; in the municipality of Humaitá: (iv) cassava, (v) agroforestry, and (vi) sugarcane; and in the municipality of Manicoré: (vii) pasture and (viii) native forest. Unformed soil samples were collected from the 0.00–0.10 m layer and analyzed for aggregate stability, bulk density, soil organic carbon, and soil organic carbon stock. Univariate, bivariate, and multivariate analyses were performed. The largest soil aggregations occurred in the annatto, guarana, sugarcane, and pasture agroecosystems. We associate the greater aggregation capacity of soils with factors that are inherent to the cultivated species and soil properties. The first factor corresponds to the adaptability of the Amazonian and grass species and their ability to produce biomass. The second factor is related to the physical and chemical properties of Amazonian soils, largely influenced by the sand fraction, soil organic carbon, soil acidity, and availability of exchangeable Ca and Mg. [ABSTRACT FROM AUTHOR]

• More Cd was immobilized in the flooding period than that in the drainage period. • ZVI reduced the release of Cd and promoted Cd immobilization during drainage process. • Adding ZVI was more conducive to Cd immobilization than directly increasing soil pH. • Adding ZVI in the flooding stage immobilized more Cd than that in the drainage stage. Zero-valent iron (ZVI) is a promising material for the remediation of Cd-contaminated paddy soils. However, the effects of ZVI added during flooding or drainage processes on cadmium (Cd) retention remain unclear. Herein, Cd-contaminated paddy soil was incubated for 40 days of flooding and then for 15 days of drainage, and the underlying mechanisms of Cd immobilization coupled with Fe/S/N redox processes were investigated. The addition of ZVI to the flooding process was more conducive to Cd immobilization. Less potential available Cd was detected by adding ZVI before flooding, which may be due to the increase in paddy soil pH and newly formed secondary Fe minerals. Moreover, the reductive dissolution of Fe minerals promoted the release of soil colloids, thereby increasing significantly the surface sites and causing Cd immobilization. Additionally, the addition of ZVI before flooding played a vital role in Cd retention after soil drainage. In contrast, the addition of ZVI in the drainage phase was not conducive to Cd retention, which might be due to the rapid decrease in soil pH that inhibited Cd adsorption and further immobilization on soil surfaces. The findings of this study demonstrated that Cd availability in paddy soil was largely reduced by adding ZVI during the flooding period and provide a novel insight into the mechanisms of ZVI remediation in Cd-contaminated paddy soils. [Display omitted] [ABSTRACT FROM AUTHOR]

This study explores the high-precision mapping (1 : 50 K stratified random sampling) of spatial variability in soil acidity (pH), soluble aluminium (Al) and plantavailable micronutrients (Fe, Mn, Cu and Zn extracted by DTPA) for the acid soils of the Meghalaya Plateau northeastern Himalaya, India. Results revealed that soils in nearly 88% of the total geographical area (TGA: 22,429 sq. km) fell below the pH limit of 5.5, of which significant areas (13.9% TGA) were strongly acidic in reaction (pH < 4.5). In close to 90% of the plateau soils, Al exceeded the critical toxicity threshold (>9.0 mg kg–1). Over 93% of the soils were high in Fe concentration (>10.5–100.0 mg kg–1). Mn, Cu, and Zn were found to be deficient in 12% (Mn < 5.0 mg kg–1), 20% (Cu < 0.6 mg kg–1), and 27% (Zn < 0.9 mg kg–1) of TGA respectively. The multi-micronutrient composite maps of Fe, Mn, Cu and Zn displayed an intricate spatial dimension in the deficiency zones. The study concludes that there is a pressing need to manage site-specific micronutrients to improve crop productivity and the quality of the produce. [ABSTRACT FROM AUTHOR]

It has been proposed that the quality of acidic soils can be improved in the presence of alkaline byproduct amendments containing silicon (Si), calcium (Ca), magnesium (Mg), and potassium (K). In the present study, we aimed to explore the effect of byproduct amendments on ameliorating acidic soil in Jiaodong Peninsula of China in the existence of different types of low-molecular-weight organic acids (LOAs, such as malic acid, citric acid, oxalic acid, and succinic acid) that are usually excreted by plant roots. Therefore, a 60-day incubation test was carried out to assess the effect of byproduct amendments and LOAs on soil physicochemical properties, soil available Mg and Ca, cation exchange capacity (CEC), soil respiration, and enzyme activities. The results showed that in the presence of LOAs, the byproduct amendments could still increased the soil pH and decreased the soil exchangeable acid and exchangeable Al3+. Compared with the control group (CK), all byproduct amendment-containing treatments could increase soil available Mg and Ca, soil CEC, soil respiration, and soil sucrase (S-SC) activity. The addition of byproduct amendments could significantly improve the chemical and biological properties of the acidic brown soils in Jiaodong Peninsula of China. However, LOAs, especially the LOAs that could precipitate with Ca in byproduct amendments, negatively impair the ameliorating effect on acidic soil compared with byproduct amendments alone treatment. When using byproduct amendments to ameliorate acidic soil, the type of LOAs secreted by plant roots was an influencing factor that must be considered. [ABSTRACT FROM AUTHOR]

The formation of soils on loamy deposits during the primary succession of vegetation after biological reclamation of a technogenically disturbed area (quarry) in the middle taiga subzone of the northeast of European Russia (Komi Republic) is considered. The planting of Picea obovata on the reclaimed area activates the formation of the tree layer and helps to accelerate pedogenetic processes. In drained conditions, by the beginning of the third decade of succession, litter horizons were formed, soil bulk density in the upper mineral horizons decreased, and a tendency towards redistribution and differentiation of the clay fraction and iron and aluminum compounds in the soil profile was noted. The latter may indicate the beginning of eluviation. The heterogeneity of the quarry surface (presence of highs and lows with a height difference of up to 2–6 m) contributes to the redistribution of moisture within the quarry and the appearance of areas with surface waterlogging. Under these conditions, the role of conservation of organic residues (peat formation) is enhanced, and gleyzation processes are activated. With an increase in the degree of surface waterlogging of soils, the soil acidity and the stocks of soil carbon and nitrogen increase, which is typical for an analogous series of background soils. The calculated rate of organic carbon accumulation in the soil layer of 0–20 cm in drained soils of the quarry is about 0.4 t/ha per year. In the waterlogged soils, it increases to 1.0–1.2 t/ha per year. The stocks of organic carbon in the upper 20 cm of the profile of young soils remain two–four times lower in comparison with the background native soils. [ABSTRACT FROM AUTHOR]

the complex mountainous environment, it is valuable to explore the variation rule of soil pH for accurately managing soil pH and the sustainable use of soil. In this study, we collected 394,736 field surface soil samples and recorded the paired environmental conditions in Guizhou Province. The spatial autocorrelation, semi-variance model and geographical detector were employed to analyze the spatial structure characteristics and distribution pattern of soil pH. The results showed that the surface soil pH varies from 3.11 to 8.99, with the variation coefficient of 17.14%. Soil pH shows a patchy mosaic distribution pattern. The structural factors of climate, parent material, and topography play a determinant role in controlling pH differentiation. Geo detector analysis showed that the explanatory power of environmental factors for the soil pH differentiation is in the order of parent rock (0.0976) > altitude (0.0144) > soil temperature regime (0.0112) > land use (0.00503) > soil moisture regime (0.000812). The reciprocal effect of parent rock and altitude is noticeable. [ABSTRACT FROM AUTHOR]

Background: Soil acidity, low soil nutrient status and low nitrogen fixing inoculants as a result of poor soil fertility management practices are the major constraints in soybean production in Assosa Zone, particularly in Assosa and Bambassi districts. Hence, this experiment was conducted to evaluate the effect of bio-, organic and inorganic NPSB fertilizers and lime on soil physico-chemical properties. Methods: During the period 2019-2020 factorial combinations of two bio-fertilizer inoculants [without bio-fertilizer (B1) and SB12 plus MAR1495 bio-fertilizer at their recommended rates of 500 g ha-1 (B2); two organic fertilizers without fresh cattle manure (M1) and fresh cattle manure at 10 t ha-1 (M2); two lime rates without lime (L1) and lime at 5 t ha-1 (L2); two inorganic NPSB fertilizers NPSB at 9.5-23-3.5-0.05 (F1) and NPSB at 19-46-7-0.1 (F2) at their recommended rates for soybean] were laid out in a randomized complete block design with three replications. Bulk density, pH, total nitrogen, available phosphorus, organic carbon and cation exchange capacity were collected and analyzed using SAS software version 9.1.3 and significant mean differences were separated using Duncan's multiple range test (DMRT). Result: Bulk density, pH, total nitrogen, available phosphorus, organic carbon and cation exchange capacity were highly affected (P<0.01) by the interactions of bio-, organic and inorganic fertilizers and lime. Finally, the interaction of SB12+MAR1495, 10 t/ha fresh cattie manure, 5 t/ha lime and NPSB at 19-46-7-0.1 improved the bulk density, pH, total nitrogen, available phosphorus, organic carbon and cation exchange capacity at both districts. [ABSTRACT FROM AUTHOR]

The central part of the country in the world classified Maize as their staple and essential crop, but this crop cannot cultivate appropriately in acidic soil. Thus, biochar, silicon and phosphorus observation can act as an agent to improve the growth of Maize in acidic soil. Additionally, biochar, well known for its alkaline properties, can reduce soil acidification and, at the same time, improve crop production. This low pH condition was caused by aluminium, manganese and low of phosphorus. Thus, silicon and phosphorus can improve crop productivity. Using biochar as a soil amendment raises the pH value, alone or in combination. Maize (Zea mays L.) and the acidity of the soil are much related to the application of biochar combined with silicon and phosphorus. Biochar simply can reduce exchangeable soil acidity, but when combined with silicon and phosphorus, it can have a greater influence on reducing soil Al toxicity. The importance of biochar with different rates combined with silicon and phosphorus to increase the pH of soil is still an inconsistent result by various studies. This review summarizes the properties of biochar, silicon and phosphorus and provides the scientific reference for its application to archive high yield of maize and reduce the acidification effect on soil. [ABSTRACT FROM AUTHOR]

Surface and subsurface acidity and soil compaction restrict root exploration and impair crop yields in agropastoral systems under no‐till. To support the development of surface and subsurface acidity correction methodologies that can decrease soil compaction in agropastoral systems under no‐till, this study tested the following hypotheses: (a) the incorporation of limestone with plowing and harrowing (conventional tillage) for surface and subsurface acidity correction decreases soil compaction in agropastoral systems under no‐till, (b) the subsurface application of hydrated lime with a shank subsoiler‐fertilizer (minimum tillage) for surface and subsurface acidity correction decreases soil compaction in agropastoral systems under no‐till, and (c) the surface application of Ca compounds (no tillage) for surface and subsurface acidity correction increases soil compaction in agropastoral systems under no‐till. In a field experiment in an agropastoral system under no‐till in an Arenic Hapludalf in Brazil, the abilities of three application management methodologies (no tillage, conventional tillage, and minimum tillage) for three Ca compounds (limestone, phosphogypsum, and hydrated lime) to ameliorate acidity in the surface and subsurface layers and decrease soil compaction were evaluated. The experimental design was a randomized complete block with four replications. The results support the following conclusions: (a) the incorporation of limestone with plowing and harrowing does not decrease soil compaction in agropastoral systems under no‐till; (b) the subsurface application of hydrated lime with a shank subsoiler‐fertilizer does not decrease soil compaction in agropastoral systems under no‐till; and (c) the surface application of limestone does not increase soil compaction in agropastoral systems under no‐till. Core Ideas: The incorporation of limestone with plowing and harrowing does not decrease soil compaction.The subsurface application of hydrated lime with a shank subsoiler‐fertilizer does not decrease soil compaction.The surface application of limestone does not increase soil compaction. [ABSTRACT FROM AUTHOR]

Soil exchangeable acidity (EA) is an indicator of aluminium toxicity potential in acidic soils. Predicting the distribution and dynamics of EA is needed for the identification and management of acidic soils. In this study, we used datasets of 355 pedons from across Ghana and the Cubist rule‐based algorithm to generate pedotransfer functions (PTFs) of EA. Eight soil properties (pH, organic carbon, calcium, sodium, magnesium, total exchangeable bases, cation exchange capacity [CEC] to clay ratio and soil depth) were used to predict EA. We first used the whole dataset to construct generic PTFs and then stratified the dataset based on World Reference Base‐Reference Soil Groups (WRB‐RSGs) to generate soil‐specific PTFs. Goodness‐of‐fit statistics comprising the root mean squared error (RMSE), Lin's concordance correlation coefficient (ρC$$ {\rho}_C $$) and coefficient of determination (R2) were used to evaluate the prediction accuracy and reliability of the developed PTF models on both calibration and validation datasets. The Fluvisols EA‐PTF exhibited lower performance metrics in the validation (RMSE = 0.17 cmolc kg−1, ρC$$ {\rho}_C $$ = 0.19, R2 = 0.24), whereas the EA‐PTFs for all other WRB‐RSGs and whole dataset had above‐average performance metrics in the validation (0.05 ≤ RMSE ≤ 0.97 cmolc kg−1; 0.34 ≤ ρC$$ {\rho}_C $$ ≤ 0.94; 0.52 ≤ R2 ≤ 0.96). Soil pH sufficed for predicting EA in soils with pH above 5.0, but in soils with a pH < 5.0, the levels of exchangeable bases (e.g., Na+, K+, Mg2+, Ca2+), CEC to clay ratio (CCR) and soil depth improved the prediction of EA. The developed EA‐PTFs are useful for estimating the missing values of EA in soil databases. [ABSTRACT FROM AUTHOR]

The productivity of soybean in Assosa Zone particularly in Assosa and Bambassi districts is very low due to poor soil fertility management practices which resulted in severe soil acidity and low N-fixing inoculant in the soil. Hence, this experiment was conducted during the main cropping season of 2019 and 2020 in Assosa and Bambassi districts to evaluate the effect of biofertilizers, lime, and inorganic NPSB fertilizers on nodulation, growth, and yield of soybean (Glycine max L. Merrill). Factorial combinations of four biofertilizer inoculants [without biofertilizer (B1), SB12 biofertilizer at the recommended rate of 500 g ha −1 (B2), MAR1495 biofertilizer at the recommended rate of 500 g ha−1 (B3) and SB12 plus MAR1495 biofertilizers at their recommended rates (B4); two lime rates named without lime (L1) and lime at 5 ton/ha (L2); two inorganic NPSB fertilizers NPSB at 9.5-23-3.5-0.05 (F1) and NPSB at 19-46-7-0.1 (F2) at their recommended rates for soybean] were laid out in a randomized complete block design (RCBD) with three replications. Effective nodules, leaf area index, and grain yield were collected and analyzed using SAS 9.1.3 version software. Results of the experiment showed that effective nodules per plant, leaf area index, and grain yield were affected by biofertilizers, lime, inorganic fertilizers, and their interactions significantly (p < 0.01) at both locations and years. Finally, the interaction of SB12 + MAR1495, lime at 5 t/ha and NPSB at 19-46-7-0.1, and the interaction of SB12, lime at 5 t/ha and NPSB at 19-46-7-0.1 gave the maximum grain yield at Assosa and Bambassi, respectively. [ABSTRACT FROM AUTHOR]

The presence of acidic soil in rural areas poses difficulties for agricultural production. One factor regulating soil pH is the overuse of inorganic fertilizer. The increased use of fertilizers in soybean production not only raises sustainability concerns but also contributes to soil acidity. Therefore, the use of organic fertilizer could offer a solution for addressing both issues related to soil acidity and sustainability. The purpose of this study was to investigate the manipulation of soil pH using organic fertilizer for soybean production under acidic stress. The planting medium, consisting of a mixture of topsoil, rice husk charcoal, and organic fertilizer (in a ratio of 2:1:1), was supplemented with 0.5 g of NPK fertilizer as a basal treatment in each planting medium. To regulate the soil acidity to pH 4, we added FeSO4 and allowed the mixture to incubate for 30 days. The results demonstrate that the application of three types of organic fertilizers chicken manure (P1), oil palm empty bunch fertilizer (P2), and vermicompost (P3) positively impacts the growth of three soybean varieties. The findings indicate that the application of P2 organic fertilizer can increase vegetative growth almost 50% in soybeans on acidic soil, including plant height, leaf count, and root length. Meanwhile, applying P3 organic fertilizer can boost reproductive growth responses in soybeans on acidic soil, such as pod number (from around 0-4 unit to 42-51 unit), grain number (from around 0-5 unit to 88-90 unit), and grain weight (from around 0-0.37 g to 12-25 g). Organic fertilizer has the potential to regulate soil pH, promoting higher yields of soybeans under acidic stress. [ABSTRACT FROM AUTHOR]

Biochar as a by-product of the carbonization of biomass has an inherent potential to modify acidic soils due to its alkaline nature. To explore the mechanism and effectiveness of biochar, a case study was conducted on severely acidic soils from six fields under tea cultivation in a subtropical zone, comparing rice husk biochars, in three rates (B5, B10, B15 t ha−1), and CaCO3 as conventional liming practice. The results showed increases in pH of 71.5%, 52.7%, 30.6%, and 29.7% in B15, B10, B5, and CaCO3-treated soils compared to the control. On average, B15 and B10 treatments resulted in the highest organic matter with 12.3% and 9.7%, respectively. B15, B10, B5, and CaCO3 caused increases of 196.6%, 173.4%, 129.7%, and 100.9% in base saturation compared to the control, respectively. Also, after the application of B15, B10, and B5 treatments, the effective cation exchange capacity increased by 191.4%, 112.1%, and 39.5%; however, the application of CaCO3 resulted in a 20.1% decrease. Overall, applying biochar on acidic soils provides adequate negative charges due to its well-extended specific surface area and pore volume, which cause the absorption of additional Al+, resulting in ameliorating soil pH. The application of proper biochar could notably be more effective in improving acidic soils than conventional practices such as the overuse of CaCO3. In this regard, evaluating various biochars in terms of feedstock, pyrolysis conditions, and modification scenarios merits in-depth research in future studies. [ABSTRACT FROM AUTHOR]

This study explored the mechanism of antimony (Sb) isotopic fractionation during chemical weathering and soil biogeochemical processes, which have important implications for Sb isotopic composition in the hydrosphere. We analyzed the major and trace element contents and Sb isotopic composition along an 8 m deep basalt weathering profile in the Huguangyan area of Guangdong Province, southern China. Mineral adsorption experiments were conducted to determine the mechanism of Sb isotopic fractionation in the weathering profile. The following minerals, α-FeOOH, γ-Fe 2 O 3 , β-MnO 2 , γ-Al 2 O 3 , montmorillonite-K10, and kaolinite-1A, preferentially adsorbed light Sb isotopes, and increased pH may lead to a lighter isotopic composition of adsorbed Sb. The positive values of τ Sb TiO 2 in the upper profile reflect exogenous Sb inputs, such as rainfall and litterfall. Accordingly, Sb isotopic fractionation is controlled by Sb adsorption onto organic matter and Fe (hydr)oxides in surface soil. At a depth of 1.8 m, Sb and other redox-sensitive elements, such as Fe, Mn, Ce, Co, Cr, and Mo, were distinctly enriched. Changes in the redox conditions result in strong Sb isotopic fractionation. In the middle layer (2–4 m), the combined effects of changes in organic matter content, soil pH, and weathering intensity explains the enrichment of light Sb isotopes. The bottom layer of the profile did not receive exogenous Sb and exhibited an Sb isotopic fractionation pattern similar to that of the basaltic bedrock. In the bottom layer, secondary Fe (hydr)oxides (e.g., goethite and hematite) preferentially adsorb the light Sb isotope (121Sb), whereas the heavy Sb isotope (123Sb) is released into the aquatic environment during intensive chemical weathering. [ABSTRACT FROM AUTHOR]

Even in peacetime, bad farming practices have degraded the soil but war has exacerbated the situation. To support comprehensive land rehabilitation, publicly available data are scrutinised to establish the composition of soils under shelling, bombing, missile strikes and pollution by fuels and lubricants. These data show that the content of various toxic substances exceeds permissible limits several-fold, and soil acidity is increased. Heavy contamination with fuels and lubricants changes the soil's chemical and physical properties, killing all but the most resilient flora and fauna. [ABSTRACT FROM AUTHOR]

The objectives of this research were: i) to study components of the internet of things (IoT) system to support community lime planting (CLP); in Maha Sarakham Province; ii) to develop IoT-CLP; and iii) to transfer IoT-CLP to the target community in Maha Sarakham Province. The research tools were: i) IoT-CLP system suitability assessment form; ii) IoT-CLP efficacy evaluation form; iii) a questionnaire to assess the effectiveness of the community lime planting; and iv) a survey of community satisfaction towards IoT-CLP. The research results showed that i) components of IoTCLP consist of: (1.1) data receivers: soil moisture, temperature, soil pH, fertilizer/nutrient; (1.2) control units: water supply, water spraying, soil pH control, and processing, fertilizer/nutrients; (1.3) operating systems: water supply, water spraying, soil pH communication and distribution system of fertilizer/soil nutrients water; (1.4) mobile application; ii) the effectiveness of IoT-CLP was evaluated at the highest level; and iii) the results of lime cultivation using IoT-CLP showed a higher yield than the traditional practices in terms of the amount of lime, size, and weight. The community was satisfied with IoT-CLP at the highest level. [ABSTRACT FROM AUTHOR]

Background: Soil pH is determined using a variety of methods. The key differences among them are the electrolytes and soil-tosuspension ratios. However, an optimal procedure tailored to a particular soil is required. This study, therefore, aimed to evaluate the effects of electrolytes and soil-to-suspension ratios on soil pH and to optimise pH measurement methods for acidic-coarsely textured soil. Methods: Varied standard electrolytes (water, 0.01 M CaCl2 and 1 M KCl) and soil-to-suspension ratios (1:1, 1:2.5 and 1:5 w/v) were used to measure the pH of thirty samples of acidic-coarsest textured soil. Result: Soil pH values were observed in the following order: water > 0.01 M CaCl2 > 1 M KCI. Higher soil pHs were a result of higher suspension volumes. The most optimal pH measurement method for an acidic-coarsely textured soil was obtained from the 1:2.5 soil-to-suspension ratio of 1 M KCl, which held the highest R2 (0.850), as well as the lowest root mean square error (RMSE) (0.010), indicating the most precise method. An alternative method suitable for a cost-saving laboratory was the 1:1 soilto-suspension ratio of 0.01 M CaCl2, which owned R2 of 0.766 and RMSE of 0.013, as its pH measurement was similar to those under the most optimal method. [ABSTRACT FROM AUTHOR]

Background and aims: Plant Ni uptake in aboveground biomass exceeding concentrations of 1000 μg g−1 in dry weight is defined as Ni hyperaccumulation. Whether hyperaccumulators are capable of mobilizing larger Ni pools than non-accumulators is still debated and rhizosphere processes are still largely unknown. The aim of this study was to investigate rhizosphere processes and possible Ni mobilization by the Ni hyperaccumulator Odontarrhena chalcidica and to test Ni uptake in relation to a soil Ni gradient. Methods: The Ni hyperaccumulator O. chalcidica was grown in a pot experiment on six soils showing a pseudo-total Ni and labile (DTPA-extractable) Ni gradient and on an additional soil showing high pseudo-total but low labile Ni. Soil pore water was sampled to monitor changes in soil solution ionome, pH, and dissolved organic carbon (DOC) along the experiment. Results: Results showed that Ni and Fe concentrations, pH as well as DOC concentrations in pore water were significantly increased by O. chalcidica compared to unplanted soils. A positive correlation between Ni in shoots and pseudo-total concentrations and pH in soil was observed, although plant Ni concentrations did not clearly show the same linear pattern with soil available Ni. Conclusions: This study shows a clear root-induced Ni and Fe mobilization in the rhizosphere of O. chalcidica and suggests a rhizosphere mechanism based on soil alkalinization and exudation of organic ligands. Furthermore, it was demonstrated that soil pH and pseudo-total Ni are better predictors of Ni plant uptake in O. chalcidica than labile soil Ni. [ABSTRACT FROM AUTHOR]

Background: Studying green manure decomposition in various returning methods can establish a scientific foundation for farmland nutrient management. Methods: In a rubber plantation on Hainan Island, China, utilized the nylon mesh bag method to imitate the decomposition of kudzu (whole plant, stem, and leaf) under two returning methods (mulching and burying) in two different sites (young and mature rubber plantations). The study examined the decomposition rate and nutrient release dynamics of kudzu, as well as the effects of kudzu reintroduction on several soil properties including soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), available phosphorus (AP), and enzyme activities. Results: Compared with mulching, the burying returning method significantly increased the kudzu decomposition rate and nutrient release proportions. After 270 days, more than 80% of the C, N, and P in different components of kudzu were released. The decomposition rate was found to be more affected by the initial soil factors than by the endogenous nutrients of kudzu. Compared with CK, all kudzu treatments led to significant increases in soil enzyme activities and soil pH, SOC, NO3−-N, and AP concentrations in two rubber plantations. The TN and NH4+-N concentrations were significantly increased in mature rubber plantations, while the TP was the opposite. Conclusion: The kudzu returned can effectively alleviate soil acidic, improve soil nutrient availability, regulating soil enzyme activities of the rubber plantation in the short-term. These results provide a scientific basis for the rational application of kudzu in rubber plantations. [ABSTRACT FROM AUTHOR]

Conventional aerobic methanotrophs oxidize methane (CH4) and covert CH4-derived carbon (C) into biomass at the oxic-anoxic interface of inundated rice paddy fields, playing indispensable role in mitigating greenhouse gas emissions and loss of organic C from methanogenesis. Two phylogenetically distinct groups of methanotrophs, type I (γ-proteobacteria) and type II (α-proteobacteria) methanotrophs, often co-exist in rice paddy soil and compete for CH4 biotransformation. Since these two methanotrophic groups also possess differential kinetics of CH4 oxidation and pathways of C assimilation, the consequence of their niche differentiation and metabolic differences in soil is expected to affect the CH4 oxidation rate and C conversion efficiency. Here, we examined the microbiology, chemistry, and CH4 metabolism in 24 geographically different paddy soils, covering four climate zones of eastern China. High-throughput sequencing of pmoA gene displayed a clear separation of in situ methanotrophic compositions between temperate (warm and mid-temperate) and warmer (subtropics and tropics) climate zones, likely driven by soil pH. Both methanotrophic groups were detected in soils but proportions of type I methanotrophs increased in temperate soils of higher pH (accounting for 76.1 ± 12.4% and 44.1 ± 14.8% in warm temperate and mid-temperate, respectively). Type II methanotrophs prevailed in warmer zones (accounting for 66.2 ± 21.6% and 70.5 ± 12.1% in tropics and subtropics, respectively) where soils were more acidic. Higher incorporation of 13C for synthesis in C14+C16 PLFAs (63.1–93.4% of total production of 13C-PLFAs) was found based on microcosm incubation, reflecting type I methanotrophs dominated the CH4 assimilation in paddy soils. Particularly, temperate soils with increased proportions of type I methanotrophs showed higher CH4 oxidation rate and C conversion efficiency. Collectively, this study depicts a continental-scale disparity of methanotrophic dynamics that tightly associates with consequence of niche differentiation of different types of methanotrophs and highlights the importance of microbiological control to maximize the rate and efficiency of methanotrophy. [ABSTRACT FROM AUTHOR]

Less attention was paid to the remediation of volatile organic compounds (VOCs) contaminated soil treated by thermal conduction heating (TCH) coupled with chemical oxidization. In this study, the lab-scale remediation experiments of trichloroethylene (TCE)-contaminated soil by TCH and TCH coupled with persulfate (TCH + PS) were performed to explore the influences of PS usage, temperature, reaction time, and the variation of soil properties. TCE was removed from contaminated soils using TCH with a temperature lower than boiling point, and the removal ratio of TCE reached 78.21% with a reaction time of 6h at 60 °C. In the TCH + PS treatments, the removal ratio increased to 87.60~99.50% when the PS dosage was increased from 7.0 mmol/kg to 17.5 mmol/kg at 60 °C. However, the usage efficiency of PS had no positive relationship with oxidant usage and temperature. The treatment with 14 mmol/kg PS after 3h at 50 °C had the highest PS usage ratio of 3.05. In addition, soil pH and soil organic matter (SOM) did not decrease significantly in the TCH-only treatment, while the content of SOM declined by almost 50% after the TCH + PS treatment. Overall, it was concluded that TCH + PS achieved higher removal efficiency, whereas TCH had less disturbance on soil pH and SOM. As such, the applicability of TCH-only or TCH + PS treatments is site-specific. [ABSTRACT FROM AUTHOR]