Soil Extracts Research Articles

Increasing phosphorus fertilizer value of recycled iron phosphates by prolonged flooding and organic matter addition

Iron (Fe) minerals are commonly used to remove phosphorus (P) from waste streams, producing P-loaded Fe(III) oxides or Fe(II) phosphate minerals (e.g., vivianite). These minerals may be used as fertilizers to enhance P circularity if solubilized in soil. Here, we tested the P fertilizer value of recycled Fe phosphates (FePs) in a pot trial and in an incubation experiment, hypothesizing that P release from FePs is possible under Fe(III)-reducing conditions. First, a pot trial was set up with rice (Oryza sativa) in all combinations of soil flooding or not, three P-deficient soils (acid, neutral, and calcareous), and six FePs (three Fe(III)Ps and three Fe(II)Ps) referenced to triple superphosphate (TSP) or zero amendments. Shoot P uptake responded to TSP application in all treatments but only marginally to FePs. The redox potential did not decrease to -200 mV by flooding for a brief period (13 d) during the pot trial. A longer incubation experiment (60 d) was performed, including a treatment of glutamate addition to stimulate reductive conditions, and P availability was assessed with CaCl2 extraction of soils. Glutamate addition and/or longer incubation lowered soil redox potential to < -100 mV. On the longer term, Fe(III) minerals released P, and adequate P was reached in the calcareous soil and in the neutral soil amended with Fe(III)P-sludge. It can be concluded that prolonged soil flooding and organic matter addition can enhance the P fertilizer efficiency of FePs. Additionally, application of FeP in powder form may enhance P availability.

Effects of varying amounts of different biochars on mercury methylation in paddy soils and methylmercury accumulation in rice (Oryza sativa L.)

There is growing evidence for the potential of biochars (BCs) in remediating mercury-contaminated paddy soils, but the high doses commonly used in laboratory studies discourage BC application in practice. To address these difficulties, we compared the effects of varying amounts of BCs from different sources on the formation of methylmercury (MeHg) in soil and its accumulation in rice through microcosm and pot experiments. The addition of a wide range of added doses (0.3, 0.6, 1, 2, 4 and 5 %, w/w) of BCs derived from different biomass feedstocks (i.e., corn stalk, wheat straw, bamboo, oak and poplar) significantly decreased the fraction of ammonium thiosulfate ((NH4)2S2O3)-extractable MeHg in the soil, although the MeHg contents varied with BC types and doses during soil incubation. However, the extractable MeHg in the soil did not continuously decrease with increasing BC doses, especially at doses of >1 %, resulting in limited further reductions. Moreover, a relatively low application rate (0.3–0.6 %, w/w) of BCs (i.e., corn stalk, wheat straw and bamboo-derived BC), especially of bamboo-derived BCs, significantly decreased the MeHg levels (42–76 %) in rice grains (brown rice). Meanwhile, the extractable soil MeHg decreased (57–85 %), although the MeHg in the soil varied under BC amendment during rice cultivation. These results provide further evidence that applying BC produced from different raw carbon materials (e.g., lignocellulosic biomass) could effectively reduce MeHg accumulation in rice grains, possibly due to MeHg bioavailability reduction in the soil. Our results suggest the possibility of mitigating MeHg accumulation in rice with a low dose of BCs, with great potential for use in remediating moderately contaminated paddy soils.

Saline–Alkaline Characteristics during Desalination Process and Nitrogen Input Regulation in Reclaimed Tidal Flat Soils

Coastal salt-affected soils account for a large area all around the world. Soil salinity and pH are two important parameters affecting soil quality. Investigating the correlation of electrical conductivity (EC) and pH at different soil depths in saline soil was useful for quickly assessing the saline–alkaline characteristics. During the natural desalination process in the field area of reclaimed lands, the phenomena of pH increase and nitrogen accumulation may occur. A field sampling experiment was conducted in slightly saline soil affected by natural desalination and newly reclaimed heavily saline soil. A series of soil–water ratio extracts consisting of 1:2.5, 1:5, 1:10, 1:20, and 1:40 was designed to measure the EC and pH for simulating the saline–alkaline characteristics during the soil desalination process. Meanwhile, for reasonable utilization of the naturally ameliorated slightly saline soil which consists of a high content of nitrogen, a plastic mulching (PM) accompanied with nitrogen (N) fertilizer addition experiment in maize cultivation plots was designed. Results showed that a significant correlation of EC and/or pH existed in all ratios of soil extracts, and the slightly saline soil had a higher nitrogen content (1.06 g kg−1). The EC was negatively correlated with pH at a depth of 0~100 cm in the coastal saline soil, which indicated the increase of pH value and alkalization during its natural desalination. Furthermore, PM treatments showed no significant difference with N treatments in soil bulk density and soil water content in the slightly saline soil. The PM and N treatments obtained similar grain yield, which was between 6.2 and 6.5 t ha−1. The soil salinity decreased in all treatments and the harvest index was largest in PM treated plots. Our study was beneficial for rapidly monitoring saline–alkaline characteristics and sustainable utilization of coastal saline soil resources. In addition, we should focus far more on pH improvement during the desalination process and rational utilization of chemical fertilizer for obtaining sustainable benefits in the coastal saline soil.

The Effect of Tillage Method on the Nutrient Regime of Soil during the Growing of Trifolium pratense

Abstract The article presents the results of studying the influence of tillage methods on the number of bacteria and fungi in the arable soil layer, nutrient indicators, and, consequently, the yield of Trifolium pratense. The purpose of the study is to determine how tillage affects the feeding regime and yield of Trifolium pratense. The research was conducted at the experimental field of the Educational and Scientific Research Center of Lviv National Environmental University. For the study of microorganisms in the arocenosis of meadow clover, soil samples were taken using a cylindrical drill from arable (0–20 cm) and sub-soil (20–40 cm) layers with an average weight of an individual sample of 300 g. For microbiological analysis, average samples from five individual samples were prepared. The isolation of the main agronomically useful groups of microorganisms from the soil was carried out by the method of microbiological sowing of soil extracts on solid nutrient media: for fungi – wort-agar, for bacteria – meat-peptone agar (MPA). The dilution of the soil extract for fungi and bacteria was, respectively, 1 : 1000; 1 : 100000. Microbiological seeding was performed in triplicate. The calculation of the total number of microorganisms in the soil was carried out by Tepper´s method. The yield of crops and the results of laboratory studies were processed by the method of variance analysis. The application of a tiered tillage allowed to increase the yield of Trifolium pratense green mass by 4.5 t·ha−1 (+17.0%) compared to the control (conventional plowing). It is established that tier ploughing with the PYA-4-40 plough promotes uniform distribution of nutrients in the arable soil layer and formation of homogeneous soil fertility. In such a soil environment, much more favorable conditions are created for the development of microflora and more intensive microbiological processes compared to the options of chisel and conventional (control) tillage, and, consequently, the formation of high yields of green Trifolium pratense.

Determination of 15 carbonyl compounds in soil using improved solid phase extraction-high performance liquid chromatography

An improved solid phase extraction (SPE)-high performance liquid chromatography method was established to determine 15 carbonyl compounds, namely, formaldehyde (FOR), acetaldehyde (ACETA), acrolein (ACR), acetone (ACETO), propionaldehyde (PRO), crotonaldehyde (CRO), butyraldehyde (BUT), benzaldehyde (BEN), isovaleraldehyde (ISO), n-valeraldehyde (VAL), o-methylbenzaldehyde (o-TOL), m-methylbenzaldehyde (m-TOL), p-methylbenzaldehyde (p-TOL), n-hexanal (HEX), and 2,5-dimethylbenzaldehyde (DIM), in soil. The soil was ultrasonically extracted with acetonitrile, and the extracted samples were derivatized with 2,4-dinitrophenylhydrazine (2,4-DNPH) to generate stable hydrazone compounds. The derivatized solutions were cleaned using an SPE cartridge (Welchrom® BRP) packed with N-vinylpyrrolidone/divinylbenzene copolymer. Separation was performed on an Ultimate® XB-C18 column (250 mm×4.6 mm, 5 μm), isocratic elution was performed with acetonitrile-water (65∶35, v/v) as the mobile phase, and detection was performed at a wavelength of 360 nm. The 15 carbonyl compounds in the soil were then quantified using an external standard method. The proposed method improves the sample processing method described in the environmental standard HJ 997-2018: Soil and sediment-Determination of carbonyl compounds-High performance liquid chromatography. A series of experiments revealed the following optimal conditions for soil extraction: acetonitrile as the extraction solvent, extraction temperature of 30 ℃, and extraction time of 10 min. The results showed that the purification effect of the BRP cartridge was significantly better than that of the conventional silica-based C18 cartridge. The 15 carbonyl compounds showed good linearities, and all correlation coefficients were above 0.996. The recoveries ranged from 84.6% to 115.9%, the relative standard deviations (RSDs) ranged from 0.2% to 5.1%, and the detection limits were 0.02-0.06 mg/L. The method is simple, sensitive, and suitable for the accurate quantitative analysis of the 15 carbonyl compounds in soil specified in HJ 997-2018. Thus, the improved method provides reliable technical support for studying the residual status and environmental behavior of carbonyl compounds in soil.

PHYTOREMEDIATION OF ACENAPHTHENE (ACN), NAPHTHALENE (NAP) AND PHENANTHRENE (PHE) CONTAMINATED SOIL USING Gardenia Jasminoides PLANT

In this study, greenhouse pots experiment was conducted to determine the phytoremediation potential of the Gardenia jasminoides plant. The plant was transplanted into 4.0 kg soil spiked with three different concentrations of the polycyclic aromatic hydrocarbons (PAHs); 1600 mg Acenaphthene (ACN), 2000 mg naphthalene (NAP) and 2400 mg phenanthrene (PHE) respectively. The Plant was allowed to grow under greenhouse conditions in triplicates with sufficient watering for ten weeks in pots containing soil contaminated with the three PAHs and control. At the end of the experiment, the levels of PAHs in the extracts of soil, roots and shoots were analyzed using high performance liquid chromatography system from Shimadzu equipped with a UV-VIS detector (SPD-20-AV). The results showed that, bioconcentration factor (BCF) values in control Experiment are 0.74 for ACN, 0.57 and 1.64 for NAP which is greater than one. Translocation factors (TF) values in control experiment are 1.23 for ACN, 1.0 for PHE and 1.20 for NAP. BCF values are greater than one at all the three different spiked experiment, 8.66 for ACN, 2.30 for PHE and 4.31 for NAP. The results also showed that the Plant was able to remove NAP with TF=2.32, ACN with TF=2.94 and PHE with TF=3.62 from contaminated soils. High values of one and above for the BCF and TF indicates high accumulation of the PAHs in the shoots of the plant. The plant may therefore be best described as phytoextractor of naphthalene, acenaphthene and phenanthrene in the soil.

Cover crop effects on infiltration, aggregate stability, and water retention in the Lower Mississippi River Valley

AbstractCover crops are widely considered to improve soil health in the form of erosion control, organic matter additions, and improving water‐holding capacity. Despite the generally well‐documented benefits, cover crops remain under‐studied in the Lower Mississippi River Valley (LMRV), an area historically dominated by intensive cultivated agriculture, with soils prone to erosion, and where the need for irrigation has led to unsustainable aquifer withdrawals. The objective of this study was to evaluate cover crop (with cover crops [CC] and without cover crops [NCC]) effects on near‐surface soil physical, chemical, and hydraulic properties. Soil sample collection and in situ measurements were conducted, once per site, between May 2018 and May 2019 across four locations within the LMRV portion of eastern Arkansas. Overall and steady‐state infiltration rates were unaffected (p &gt; .05) by cover‐crop treatment. Across all locations, extractable soil Na content in the top 10 cm was greater (p ≤ .05) with NCC (31.6 kg ha−1) compared with CC (21.6 kg ha−1). Averaged across treatment and soil depth (0 to 5 and 5 to 10 cm), water‐stable aggregate concentration in the 0.25‐ to 0.5‐ (0.101 g g−1) was 1.5 times greater (p ≤ .05) than that in the 1.0‐ to 2.0‐mm size class (0.068 g g−1). Though many soil properties did not significantly differ between CC treatments due to their collective variations, results of this study demonstrate the wide‐spread implications of CC use on physical, chemical, and hydraulic properties across a region.

Trace metal uptake in forage systems receiving long‐term applications of alum‐treated or untreated poultry litter

AbstractTreating poultry litter with alum (Al2[SO4]3·14H2O) is a commonly used best management strategy for reducing ammonia (NH3) volatilization and phosphorus (P) runoff and leaching. However, little is known about how this amendment affects trace metal availability and uptake by forages, as well as potential issues with phytotoxicity, toxicity to grazing animals, and overall yield. The objective of this study was to determine longitudinal effects of alum‐treated poultry litter, untreated litter, ammonium nitrate, and an unfertilized control on trace metal (As, Cu, Se, and Zn) and S concentrations and uptake by tall fescue (Festuca arundinacea Schreb.), yield, as well as availability in soil over 20 years. Greater (p &lt; 0.05) Mehlich‐3 extractable soil As and subsequent forage As uptake occurred with alum beyond the 6.72 Mg ha−1 rate; however, forage As concentrations were not affected by alum. Forage yields were greater with alum‐treated and untreated litters than with ammonium nitrate applied at the same N rate. Treating litter with alum generally did not improve tall fescue yields, except at the lowest litter rate (2.24 Mg ha−1). Alum treatment of poultry litter has been shown to be a cost‐effective best management practice that reduces ammonia volatilization, which improves air quality and poultry production, while reducing P and heavy metal runoff and ultimately improving water quality. Given that trace metal and S concentrations in forages were all in the normal ranges, treating poultry litter with alum does not pose issues with respect to metal phytotoxicity and/or toxicity to grazing animals.

Extraction of active, contaminant degrading enzymes from soil

Soil microorganisms play critical roles in the degradation of micro-and nano-pollutants, and the corresponding proteins and enzymes play roles in pollutant recognition, transportation, and degradation. Our ability to study these pathways from soil samples is often complicated by the complex processes involved in extracting proteins from soil matrices. This study aimed to develop a new protein soil extraction protocol that yielded active, intracellular enzymes from the perchlorate degradation pathway, particularly perchlorate reductase. An indirect method, which focused on first separating the cells from the soil matrix, followed by cell lysis and enzyme extraction, was evaluated. The optimized indirect method achieved a final extraction efficiency of the active enzyme and total protein of 15.7 % and 3.3 %, respectively. The final step of separating enzymes from residual soil components resulted in the highest activity and protein losses of 67.7 % ± 14.8 % and 91.8 % ± 1.8 %, respectively. Five buffers, each at different concentrations (0.01 M, 0.05 M, and 0.1 M), were tested to enhance enzyme extraction efficiency. The best extractant requires careful consideration between the highest activity and the quality of the recovered enzymes. Coextraction of humic substances could be minimized by using 0.1 M as compared to 0.01 M and 0.05 M of sodium pyrophosphate; however, this resulted in less recovered activity compared to lower extractant concentrations.

A simple tool to assess the effect of water-soluble soil pollutants on enzyme activity in human whole blood samples using WST-1 assay

Hazardous compounds accumulated in soil affect soil quality. Here we show that WST-1 can be used for evaluation of the effect of water soil extracts on enzyme activity in human whole-blood samples. Soil samples from the Shumen Plateau Nature Park (NP) and the City Park in Shumen (SCP) were studied. We observed significant differences between control and treated whole-blood samples. These results indicated that soil water extracts affected normal metabolic activity. In conclusion, the WST-1 assay can be used for biomonitoring soil quality. The presence of harmful water-soluble compounds in tested soils may pose a risk to ecosystems and human health.

A New Method for the Quantitative Determination of Sulfate Ions in Aqueous Extracts from Soils and in Aqueous Media, and Analytical Equipment for Its Implementation

A method and the necessary analytical equipment for the mass quantitative determination of sulfate ions in aqueous extracts from soils and in aqueous media is proposed, consisting in the fact that a known amount of 2-aqueous barium chloride with hydrogen chloride is added to the aliquot of the analyzed sample in the form of an aqueous solution. The resulting insoluble barium sulfate compound reduces the initial concentration of barium chloride. The amount of barium chloride remaining in the solution is determined on the specially designed flame spectrophotometric analyzer. This allows you to calculate the amount of sulfate ions associated with barium, which is automatically performed by the device program. The range of reliably determined concentrations of sulfate ions by the proposed method in water samples ranged from 10 to 100 mg/dm³. The range of reliably determined concentrations of sulfate ions in aqueous extracts from soils ranged from 0.2 to 2.4 C_(1/2SO4) mol/dm³ (from 10 to 115 mg/dm³). Higher concentrations of sulfate ions must be diluted multiple times with distilled water. The method makes it possible to determine the concentration of sulfate ions in aqueous soil extracts, freshwater reservoirs and rivers, underground sources, tap water, sediments contaminated with sulfuric acid emissions from industrial enterprises. The method is quite simple, accurate and productive. The method is certified by the State Ural Research Institute of Metrology (MVI-66373620-007-2018) and approved by the Federal Agency for technical regulation and Metrology (Rosstandart), as a standard method under No. 253.0080/RA. RU.311866/2019. Patent No. 2681855 of the Russian Federal Service for Intellectual Property with priority dated September 15, 2017 was obtained for the method for determining sulfur in the form of a sulfate ion in an aqueous extract from soils and the equipment necessary for this. Detailed methods for determining sulfate ions in these objects are published in the open press in the book: "Determination of agrochemical and chemical parameters of soils, plants and aquatic environments using flow-decade analysis technology" edited by Academician of the Russian Academy of Sciences R. F. Baibekov.

An identified agronomic interpretation for potassium permanganate oxidizable carbon

AbstractThe absence of clear empirical relationships between soil health and agronomic outcomes remains an obstacle to widespread adoption of soil health assessments in row crop systems. The objectives of this research were to (1) determine whether soil health indicators are connected to corn (Zea mays L.) productivity and (2) establish interpretive benchmarks for soil health indicators in Missouri. The objectives were accomplished by collecting corn grain yield at 446 monitoring sites (37 m2) in 84 commercial production fields in 2018–2020. Soil health and soil fertility samples were collected prior to planting at each site. These data, along with site‐specific soil and weather data, were modeled using traditional stepwise regression and nonparametric random forest (RF) and conditional inference forest (CIF) approaches. Root‐mean‐square errors were similar (1.4–1.5 Mg ha−1) with distinct R2 improvements over stepwise regression for both CIF (R2 = 0.45) and RF (R2 = 0.46) algorithms. Only seasonal rainfall and potassium permanganate oxidizable carbon (POXC) were included as top factors governing grain productivity in each model approach, thus demonstrating a regionally robust empirical relationship between POXC and grain productivity. Partial dependency analysis and two decision tree approaches identified 415 mg POXC kg−1 as a threshold for maximum grain productivity, providing a framework for regional interpretation of on‐farm soil health assessments. Little evidence was found connecting grain productivity with autoclaved citrate extractable protein and soil respiration. These findings underscore the power of POXC as an emerging soil health indicator to assess and quantify soil management effects on grain productivity.

Isolation and screening of Thermoactinomycetaceae family members as an extremophilic poor investigated and promising natural source of antimicrobial substances.

Recent evidences have shown that methicillin-resistant Staphylococcus aureus (MRSA) can cause severe infections and is resistant to almost all commercially available antibiotics. Therefore, screening unknown sources of biological compounds such as the Thermoactinomycetaceae family as extremophilic bacteria may be helpful to find new antimicrobial agents. Various samples were collected from different ecosystems, including desert, volcano, compost, and forest. They were cultured on Soil extract agar and Water agar. The antimicrobial activity of the isolates was evaluated using agar overlay and well diffusion methods. Members of the Thermoactinomycetaceae family were selected for further study: Their ability to grow at different temperatures, NaCl concentrations, and pH values, enzyme production ability, antimicrobial secondary screening, fractionation of their supernatants and so on. According to molecular identification of active isolates against MRSA, three strains, including Laceyella sacchari UTMC 2705, Thermoactinomyces sp. UTMC 2721, and Laceyella sp. UTMC 2731, belonged to Thermoactinomycetaceae were identified. The minimum inhibitory concentrations of their extracts were tested against some pathogenic bacteria, showing their antimicrobial activity with a broad spectrum. The results of TLC bioautography of the extracts showed that the most active fractions were semi-polar. Also, the results of HPLC analysis showed the existence of several UV-active compounds in their extracts. The present study highlighted the importance and potential of Thermoactinomycetaceae members as a less-known source of antibiotics against pathogenic bacteria.

Sampling terrigenous diffuse sources in watercourse: Influence of land use and hydrological conditions on dissolved organic matter characteristics

Diffuse and point sources of dissolved organic matter (DOM) in streams influence its composition, interactions and fate in the aquatic ecosystem. These inputs can be very numerous at the scale of a watershed, and their identification remains a challenge, especially for diffuse sources related to land use. The complexity of the transfer mechanisms and the reactivity of DOM throughout the soil-water column continuum raise questions about the sampling of diffuse sources in watercourses. To answer this issue, we compared the characteristics of soil-extracted DOM influenced by a particular land use (homogenous sub-catchment of forest and vineyard) and DOM collected from the watercourse adjacent to the soil samples. A 28-day incubation experiment of soil extracts was designed to remove the labile fraction of DOM. During the first 3 days, between 40 and 70 % of the DOC mass was lost for both types of soils. A set of optical indicators (UV–Visible, EEM fluorescence and HPSEC/UV-fluorescence) showed that the labile fraction was mostly composed by low (<1 kDa) and high (>10 kDa) protein-like molecules. At the end of the incubation, soil-extracted DOM was mainly composed of medium molecules (1–10 kDa) associated to terrigenous humic-like compounds. Its optical and size molecular signature tended towards that in the adjacent watercourses and was specific to land use. However, the characteristics of DOM in watercourses was also influenced by the hydrological conditions, probably due to a transfer of top soil DOM during high water periods and both deep soil and autochthonous DOM during low water periods. These results were obtained by a set of indicators, including novel ones derived from HPSEC/UV-fluorescence. Finally, this study demonstrated that it is possible to sample the DOM representative of a land use directly in the river downstream of the homogeneous sub-basin by multiplying the samples during contrasting hydrological conditions.

Use of untargeted metabolomics to analyse changes in extractable soil organic matter in response to long-term fertilisation

Use of untargeted metabolomics to analyse changes in extractable soil organic matter in response to long-term fertilisation

A subcritical water extract of soil grown Zingiber officinale Roscoe: Comparative analysis of antioxidant and anti-inflammatory effects and evaluation of bioactive metabolites.

Introduction: Ginger (Zingiber officinale Roscoe) can scavenge free radicals, which cause oxidative damage and inflamm-ageing. This study aimed to evaluate the antioxidant and anti-inflammatory effects of soil ginger's sub-critical water extracts (SWE) on different ages of Sprague Dawley (SD) rats. The antioxidant properties and yield of SWE of soil- and soilless-grown ginger (soil ginger and soilless ginger will be used throughout the passage) were compared and evaluated. Methods: Three (young), nine (adult), and twenty-one (old) months old SD rats were subjected to oral gavage treatments with either distilled water or the SWE of soil ginger at a concentration of 200 mg/kg body weight (BW) for three months. Results: Soil ginger was found to yield 46% more extract than soilless ginger. While [6]-shogaol was more prevalent in soilless ginger, and [6]-gingerol concentration was higher in soil ginger (p < 0.05). Interestingly, soil ginger exhibited higher antioxidant activities than soilless ginger by using 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assay. With ginger treatment, a reduced levels of tumour necrosis factor-α (TNF-α) and C-reactive protein (CRP) but not interleukin-6 (IL-6) were observed in young rats. In all ages of SD rats, ginger treatment boosted catalase activity while lowering malondialdehyde (MDA). Reduction of urine 15-isoprostane F2t in young rats, creatine kinase-MM (CK-MM) in adult and old rats and lipid peroxidation (LPO) in young and adult rats were also observed. Discussion: The findings confirmed that the SWE of both soil and soilless grown ginger possessed antioxidant activities. Soil ginger produced a higher yield of extracts with a more prominent antioxidant activity. The SWE of soil ginger treatment on the different ages of SD rats ameliorates oxidative stress and inflammation responses. This could serve as the basis for developing a nutraceutical that can be used as a therapeutic intervention for ageing-related diseases.

Chemical processes and sustainability of rice-shrimp farming on saline acid sulfate soils in mekong delta

In the history of rice-shrimp farming (RSF) in the Mekong Delta, in saline acid sulfate soils (ASS), RSF has proved its sustainability as there is no long-term accumulation of acidity and salinity that adversely affect RSF production. However, the soil processes involved in this phenomenon are not well understood. This study aimed to determine the significant changes in soil and water chemical indicators associated with soil processes during different stages of RSF. Sampling was conducted in six stages to determine the pH and electrical conductivity (EC) of canal and field water, and the pHe, ECe, and sodium-soluble saturated extract (Na-sol) of surface soil (surS) and subsurface soil (subS) in the low-salinity area (LSA) and high salinity area (HSA) of Bac Lieu province. Putative exchange (exch.) Na+ hydrolysis occurs at the beginning of the rainy season when excess salts are leached. This drastically increases the pH of the field water by 0.6 pH units, from 8.2 to 8.8 in stages 1 to 2, respectively. Putative sulfurization has been shown to occur in subS in both LSAs and HSAs, with a significant decrease of 0.5 pH units from stages 4 to 5, leading to a decrease in the Na-sol of subS through exch. Na+ transformation. Simultaneously, with active soil preparation and liming for RSF, chemical processes such as exch. Na+ hydrolysis, sulfurization, and Na+ transformation are the main factors promoting exch. Na+ desorption, which help to reduce the long-term build-up of salinity and acidity that adversely affect RSF production. Although gypsum is considered an effective material in improving saline soils, in Vietnam, gypsum is the liming material of CaSO4; however, it is not commonly used in agriculture because of its high cost. By using CaCO3 or dolomite as a liming material in saline ASS, the dissolution of lime by sulfuric acid can provide a good opportunity for soil improvement and rice growth in RSF.

Plant Parasitic Nematode Identification in Complex Samples with Deep Learning.

Plant parasitic nematodes are significant contributors to yield loss worldwide, causing devastating losses to every crop species, in every climate. Mitigating these losses requires swift and informed management strategies, centered on identification and quantification of field populations. Current plant parasitic nematode identification methods rely heavily on manual analyses of microscope images by a highly trained nematologist. This mode is not only expensive and time consuming, but often excludes the possibility of widely sharing and disseminating results to inform regional trends and potential emergent issues. This work presents a new public dataset containing annotated images of plant parasitic nematodes from heterologous soil extractions. This dataset serves to propagate new automated methodologies or speedier plant parasitic nematode identification using multiple deep learning object detection models and offers a path towards widely shared tools, results, and meta-analyses.

Assessment of some extractable macro and micro-nutrients along with multivariate analysis of their spatial distribution in soils of Haridwar district of Uttarakhand

An investigation was carried out to analyze the general soil properties and extractable macro- (N, P, K, Ca, Mg, S) and micro-nutrients (Zn, Cu, Fe, Mn, B, Mo) in the soils of Haridwar district and the relationships between general soil properties and soil extractable nutrients. Surface (0-15 cm) soil samples (n=300) were taken from the all six developmental blocks of Haridwar district. The ranges for general properties were: sandy loam to sandy clay loam texture, 5.18-8.31 soil pH and 0.074-0.731 dSm-1 electrical conductivity (EC) (1:2 soil-water suspension) and 1.49-9.84 g kg-1 soil organic carbon content. The amount of alkaline KMnO4 extractable N in these soils ranged from 105.0-290.05 kg ha-1 while Olsen’s or Bray’s extractable P content ranged from 5.88-67.42 kg ha-1. Neutral 1 N ammonium acetate extractable K, Ca and Mg varied from 89.6-548.8 kg ha-1, 1102 - 4359 mg kg-1 soil and 30-1002 mg kg-1 soil, respectively. Calcium chloride (0.15 percent) extractable S ranged from 5.3-29.4 mg kg-1 soil. The contents of DTPA extractable Zn, Cu, Fe, and Mn were 0.13-9.14 mg kg-1 soil, 0.01-1.8 mg kg-1 soil, 1.26-61.77 mg kg-1 soil and 0.66-41.87 mg kg-1 soil, respectively. Hot water-soluble B ranged from 0.31-1.19 mg kg-1 soil and ammonium oxalate (pH 3.3) extractable Mo varied from 0.25-1.59 mg kg-1 soil. The nutrient index (N.I.) computed for different extractable soil nutrients for the entire district of Haridwar showed that the overall the district was low in N, medium in K S, Zn and high in all other nutrients (P, Ca, Mg, Cu, Fe, Mn, B and Mo).

Accurate Detection of Cd2+ and Pb2+ Concentrations in Soils by Stripping Voltammetry Peak Areas under the Mutual Interference of Multiple Heavy Metals

The accurate detection of Cd2+ and Pb2+ in soils by square-wave anodic stripping voltammetry (SWASV) faces great challenges because the interaction between multiple heavy metal ions (HMIs) interferes seriously with their SWASV signals. To detect Cd2+ and Pb2+ by SWASV with high accuracy, an overlooked but informative signal, i.e., stripping current peak area, was employed and combined with chemometric methods to suppress the above mutual interference. An easy-to-prepare electrode, i.e., in-site electroplating bismuth film modified glassy carbon electrode, was used to sense the multiple HMIs. Two machine learning algorithms, including SVR and PLSR, were used to establish the detection models of Cd2+ and Pb2+. In addition, this study developed a homemade algorithm to automatically acquire the stripping peak heights and stripping peak areas of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+, which acted as the inputs of machine learning models. Then, the detection performance of various SVR and PLSR models were compared based on the R2 and RMSE values of the validation dataset. Results showed that the SVR detection models established by the algorithmically acquired peak areas presented the best stability and accuracy for detecting both Cd2+ and Pb2+ concentrations under the existence of Zn2+ and Cu2+. The R2 and RMSE values of the SVR models built using the peak heights of HMIs acquired by electrochemical workstation control software (Imanu-SVR) were 0.7650 and 5.3916 μg/L for Cd2+, and 0.8791 and 20.0015 μg/L for Pb2+, respectively; the R2 and RMSE values of the SVR models built using the peak area automatically acquired by the developed algorithm (Aalgo-SVR) were 0.9204 and 2.9906 μg/L for Cd2+, and 0.9756 and 13.1574 μg/L for Pb2+, respectively. More importantly, the detection results of the proposed method in real soil extracts for Cd2+ and Pb2+ concentrations were close to those of ICP-MS, verifying its practicability. This study provides a new solution for the accurate detection of targeted heavy metals under the co-existence of multiple HMIs by the SWASV method.