Soil Extracts Research Articles

Portable X‐ray fluorescence spectrometry accurately measures metal concentrations in aqueous Mehlich III soil extraction solutions

AbstractAccurate measurement of metal concentrations in soil and water is vital for healthy crop production and decision making for environmental surveys. While there are a multitude of laboratory‐based soil analysis methods, such as inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), flame emission spectrometry, and atomic absorption spectroscopy, most are time and resource intensive. Additionally, there is a lack of information for rapid analysis of elements for aqueous soil extractions. The goal of this research is to establish elemental correlations between portable X‐ray fluorescence (pXRF) measurements of Mehlich III soil extractions and traditional elemental measurements via ICP‐OES. We hypothesize that certain metals can be accurately measured in aqueous soil extraction solutions by pXRF to the same degree as they are measured by ICP‐OES. To test this hypothesis, Mehlich III and 2% nitric acid solutions with known elemental concentrations were analyzed via ICP‐OES and pXRF. Soil samples extracted using Mehlich III were compared between ICP‐OES and pXRF to verify correlations. High correlations were found for As, Ca, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, V, and Zn in both the Mehlich III and 2% nitric acid solutions at concentrations between 5 and 85 mg L−1. P, S, and Si did not show high correlations at concentrations <100 mg L−1. These results indicate that between 5 and 85 mg L−1, pXRF analysis of aqueous solutions and soil extractions is a reliable technique; however, at low concentrations (i.e., <5 mg L−1 for metals and <100 mg L−1 for P and S), pXRF is not well suited.

Serendipita indica: A Promising Biostimulant for Improving Growth, Nutrient Uptake, and Sugar Accumulation in Camellia oleifera

Serendipita indica is a very promising root-associated endophytic fungus that is widely used on various plants; however, whether it affects the growth and physiological activity of an oilseed crop (Camellia oleifera) under field conditions remains unclear. In this study, we analyzed the effects of S. indica inoculation on root colonization rate, growth rate, photosynthetic parameters, mineral element concentrations and related gene expression, and sugar concentrations and expression of their transporter genes in four-year-old C. oleifera trees in the field. The results showed that the root colonization rate of C. oleifera increased from 3.37% to 9.42% following being inoculated with S. indica. Inoculation with S. indica significantly increased the plant height (46.81%), net photosynthetic rate (69.16%), nitrogen balance index (14.44%), chlorophyll index (21.08%), leaf K (7.4%), leaf Ca (13.52%), root P (17.75%), root K (12.80%), soil NH4+-N (17.78%), available K (26.66%), Olsen-P (184.30%), easily extractable glomalin-related soil protein (39.26%), and soil organic carbon (16.25%) concentrations compared to the uninoculated treatment. Inoculation with S. indica also significantly up-regulated the expression of CoHKT1;1 and CoCAX1;2 in the leaves and roots and CoPht1;1, CoPht1;2, and CoPht1;3 in the leaves. Plants inoculated with S. indica also presented significantly higher leaf glucose, fructose, and sucrose concentrations, accompanied by up-regulated expression of CoSWEET2a, CoSWEET7, CoSWEET9b, CoSWEET17a, and CoSWEET17b. These results suggest that S. indica has significant potential as a biostimulant for enhancing the growth and nutritional profile of C. oleifera, thereby contributing to sustainable oilseed production.

Evaluation of impacts of biosolids application and drainage water management on soil N2O and CH4 emissions using the flux gradient method

Existing studies have shown contradictory findings with respect to whether biosolids applications on agricultural lands lead to intensification of soil greenhouse gas (GHG) emissions. Here, we describe the results of deployment of the micrometeorological flux gradient method to quantify post-biosolid soil emissions of nitrous oxide (N2O) and methane (CH4) on a farm with drainage water management (DWM) on the Eastern Shore of Maryland. The fluxes following biosolid additions to cornfields in 2020 were compared with fluxes from the same farm in 2018, when no fertilizer was applied to soybeans, and in 2019, when urea ammonium nitrate (UAN) was applied to corn. Extractable soil nitrate was highest following biosolids application, contributing to the highest N2O emissions in the growing season of 2020 compared to 2018 (no fertilizer) and 2019 (UAN). Other contributing factors include the low C:N ratio of the biosolids and the above average precipitation in 2020. In contrast, different fertilization regimes did not generate distinct differences for CH4 fluxes, which were very low in all three years. No statistically significant treatment effect of DWM was found for either N2O or CH4 during the peak emission period after biosolids application, which aligns with the result of our earlier research. Annualized estimated N2O emission factors (EFs) for biosolids addition were 5–6 % in the DWM and 3–4 % in the non-DWM fields, although this includes uncertainties associated with gap filling. These biosolids EFs are 2–3 times the N2O EF for synthetic fertilizer application at this same farm in 2019 (1–2.5 %) and 2–4 times the IPCC Tier 1 EF (1.6 %) for synthetic fertilizer, demonstrating the intensification effect of biosolids addition on soil N2O emissions for the cropland studied here.

Evolution of Cu and Zn speciation in agricultural soil amended by digested sludge over time and repeated crop growth

Metals such as Zn and Cu present in sewage sludge applied to agricultural land can accumulate in soils and potentially mobilise into crops. Sequential extractions and X-ray absorption spectroscopy results are presented that show the speciation changes of Cu and Zn sorbed to anaerobic digestion sludge after mixing with soils over three consecutive 6-week cropping cycles, with and without spring barley (Hordeum vulgare). Cu and Zn in digested sewage sludge are primarily in metal sulphide phases formed during anaerobic digestion. When Cu and Zn spiked sludge was mixed with the soil, about 40% of Cu(I)-S phases and all Zn(II)-S phases in the amended sludge were converted to other phases (mainly Cu(I)-O and outer sphere Zn(II)-O phases). Further transformations occurred over time, and with crop growth. After 18 weeks of crop growth, about 60% of Cu added as Cu(I)-S phases was converted to other phases, with an increase in organo-Cu(II) phases. As a result, Cu and Zn extractability in the sludge-amended soil decreased with time and crop growth. Over 18 weeks, the proportions of Cu and Zn in the exchangeable fraction decreased from 36% and 70%, respectively, in freshly amended soil, to 28% and 59% without crop growth, and to 24% and 53% with crop growth. Overall, while sewage sludge application to land will probably increase the overall metal concentrations, metal bioavailability tends to reduce over time. Therefore, safety assessments for sludge application in agriculture should be based on both metal concentrations present and their specific binding strength within the amended soil.

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

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

Effects of long-term nighttime warming on extractable soil element composition in a Mediterranean shrubland

Understanding the soil biogeochemical responses to increasing global warming in the near future is essential for improving our capacity to mitigate the impacts of climate change on highly vulnerable Mediterranean ecosystems. Previous studies have primarily focused on the effects of warming on various biogeochemical processes. However, there is limited knowledge about how the changes in water availability associated to high temperatures can alter the bioavailability and dynamics of soil elements, thereby impacting ecosystem productivity, species composition, and pollution through soil biogeochemical and hydrological processes. In this study, we investigated the effects of long-term nighttime warming on the extractable concentrations of organic carbon (EOC), total nitrogen (ETN), total phosphorus (ETP), and 17 mineral elements (arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), sulfur (S), strontium (Sr), vanadium (V), and zinc (Zn)) through environmental experiments in a semi-arid Mediterranean shrubland. We explored the potential biotic and abiotic mechanisms underlying the seasonal and long-term changes in extractable-mobilizable elemental composition and concentrations. Our findings revealed that prolonged warming led to higher mean annual soil temperature (with an average increase of 0.67 °C from 1999 to 2014), accumulation of soil organic matter (EOC) and extractable concentrations of soil elements (particularly increased ETP and extractable Ca, Mg, Cu, Sr, Mn, and As). These changes were attributed to uniformly higher activities of extracellular soil enzymes and/or lower plant photosynthetic and nutrient uptake capacity linked to more water deficit under warmer conditions. Seasonality unevenly altered element extractable concentrations, with soil microclimate (temperature and water content) and biological (soil microbial and plant) activity being the main drivers of this variability, thus influencing soil element composition. These results suggest significant fluctuations in the extractable concentrations of specific mineral elements in these soils, implying potential future variations in soil element composition as well as the loss of total element concentrations/contents in semi-arid Mediterranean ecosystems due to increasing warming. Therefore, these findings enhance our ability to predict ecosystem management strategies and mitigate the observed negative impacts on plant-soil systems and water quality in the context of climate change.

Method of rapid spectrophotometric determination of iron in dithionite extracts of soils

Amethod for the determination of dithionite iron for soil samples and fractions of the order of 20–25 mg with a spectrophotometric termination has been developed and optimized.Unlike the previously described methods, phenanthroline was used as a chromogen, which made it possible to simplify the analysis by eliminating the combustion stage.The procedure for processing samples with citrate-bicarbonate-dithionite extractant has been optimized.The repeatability and intra-laboratory reproducibility of the technique are investigated.Verification of the proposed methodology by comparison with the standard one showed good convergence of the results.

TWO-DIMENSIONAL ION CHROMATOGRAPHY TANDEM-MASS SPECTROMETRIC (2D-IC-MS/MS) METHOD FOR THE ANALYSIS OF PHOSPHORUS COMPOUNDS IN SOIL

Investigations into soil organic phosphorus (Po) dynamics are instrumental in understanding the transformations and processes responsible for ecosystem productivity. However, quantitative analysis of Po in a soil environment is extremely challenging due to low target analyte concentrations and matrix interferences with chromatography and analysis. Consequently, a two-dimensional ion chromatography-tandem mass spectrometric (2D-IC-MS/MS) method was developed to estimate soil Po concentrations. The first dimension diverted early eluting anions to waste while preconcentrating P compounds in a trap column, followed by chromatographic separation and detection in the second dimension. Detection was done using a mass spectrometer, and quantification was performed using the multiple reaction monitoring scan (MRM) method. The linear range of the studied P compounds, mostly nucleotides, was 0.05 – 50 ng/mL. Most P compounds were detected and quantified in calcareous subsoil samples in the concentration ranges 0.70 – 51.78 ng/g. The developed method achieved chromatographic separation that allowed unambiguous identification of isobars/isomers and isotopologues contributing to interferences in MS detection. However, improvements to the extraction method and post-clean-up procedures are required due to the complexity of soil extract composition, extreme matrix effect and/or loss of analyte during preconcentration. The method is ideal for simultaneously analyzing P compounds from environmental samples to elucidate key components of the soil P dynamics.

Assessing Micronutrients in Soil with a New Chemical Extractant Using Isotopic Dilution Techniques: Linkages to Labile Fractions in Soil

ABSTRACT With the purpose of economizing the routine soil testing for micronutrients and avoiding the use of multiple soil extraction procedures, a laboratory investigation was attempted to evaluate a new chemical extractant for assessing the availability of common micronutrients (Fe, Cu, Mn, Zn, Mo, and B) in soils of widely varying properties (n = 32). The new extractant designated as OM-MES-VERA# contained 0.01 M oxalic acid, 0.02 M maleic acid, 0.02 M 2-(N-Morpholino) ethane sulfonic acid (MES), 0.0025 M ethylene diamine tetraacetic acid di-sodium salt, 0.02 M acetic acid, and 0.1% polyacrylamide (final pH adjusted to 6.0). OM-MES-VERA extracted significantly higher amounts of micronutrient cations and B from soils compared to the conventional diethylene triamine pentaacetic acid (DTPA, pH 7.3) extractable micronutrient cations and hot water soluble B, respectively, but lesser amount of Mo compared to Mehlich-3 universal extractant. Soil test values by both OM-MES-VERA- and conventional extractants were correlated with soil properties. The labile (E and L) values of micronutrient cations and Mo estimated by isotopic dilution method, ammonium bicarbonate-DTPA, pH 7.6 extractable soil B (as an estimate of E for B) and B concentration in maize (as an estimate of L for B) were successfully regressed on soil test values of micronutrients by OM-MES-VERA and conventional soil extractants except in the case of DTPA (pH 7.3) for E-value of Fe and L-value of Mn. The OM-MES-VERA extractant can be considered to assess the availability of common micronutrients in soils of diverse soil properties.

Tracking atrazine degradation in soil combining 14C-mineralisation assays and compound-specific isotope analysis

The quantification of pesticide dissipation in agricultural soil is challenging. In this study, we investigated atrazine biodegradation in both liquid and soil experiments bioaugmented with distinct atrazine-degrading bacterial isolates. This was achieved by combining 14C-mineralisation assays and compound-specific isotope analysis of atrazine. In liquid experiments, the three bacterial isolates mineralised over 40% of atrazine, demonstrating their potential for extensive degradation. However, the kinetics of mineralisation and degradation varied among the isolates. Carbon stable isotope fractionation was similar for Pseudomonas isolates ADPT34 and ADP2T0, but slightly higher for Chelatobacter SR27. In soil experiments, atrazine primarily degraded into atrazine-desethyl, while atrazine-hydroxy was mainly observed in experiments with SR27. Atrazine mineralisation in soil by ADPT34 and SR27 exceeded 40%, whereas ADP2T0 exhibited a mineralisation rate of 10%. In experiments with ADPT34 and SR27, atrazine 14C-residues were predominantly found in the non-extractable fraction, whereas they accumulated in the extractable fraction in the experiment with ADP2T0. Compound-specific isotope analysis (CSIA) relies on changes of stable isotope ratios and holds potential to evaluate herbicide transformation in soil. CSIA of atrazine indicated atrazine biodegradation in water and solvent extractable soil fractions and varied between 29% and 52%, depending on the bacterial isolate. Despite atrazine degradation in both soil fractions, a significant portion of atrazine residues persisted, depending on the bacterial degrader, initial cell concentration, and mineralisation and degradation rates. Overall, our approach can aid in quantifying atrazine persistence and degradation in soil, and in optimizing bioaugmentation strategies for remediating soils contaminated with persistent herbicides.

Analysis of the Soil Fertility Condition in Jiliba Village, Ganjam District, Odisha

An assessment of soil fertility was conducted in Jiliba village, situated in the Bellaguntha block of Ganjam district in the North-Eastern agroclimatic zone of Odisha, India. Analysis of physical and chemical properties was conducted on soil samples obtained at a depth ranging from 0 to 15 cm. The findings indicate that the predominant soil texture in the hamlet under study consisted of sandy loam and clay loam. The soil hue ranged from Dark Grey at 10 years old to Yellowish brown at 10 years old. The pH of the soil varied from somewhat acidic (5.5-6) to neutral (6.5-7.5). The electrical conductivity of the whole research area remained uniformly below 0.74 dSm-1. Approximately 77.5% of the research region exhibited soil organic carbon (SOC) levels below 0.5%. The available nitrogen concentration was insufficient, varying from 87.8 to 150.5 kg/ha, indicating a possible requirement for nitrogen fertilization to adequately sustain crop development. The phosphorus content in Brays exhibited significant variation, ranging from 4.7 to 198.2 kg/ha, providing evidence of geographic heterogeneity in phosphorus availability throughout the hamlet. The soil potassium level exhibited significant variation, ranging from 54.6 to 435.6 kg/ha, potentially impacting the absorption of nutrients and the production of crops. The Nutrient Index readings for nitrogen (1.0) and phosphorus (1.32) were below expected levels, suggesting the necessity of implementing nutrient management strategies to enhance soil fertility. The potassium Nutrient Index value of 1.87 indicates a moderate level of potassium availability in comparison to nitrogen and phosphorus. The extractable soil sulphur from calcium chloride (CaCl2) ranged from 6.4 to 126.7 kg/ha, underscoring the significance of sulphur for crop fertilization. Modest variations in exchangeable calcium (Ca2+) and magnesium (Mg2+) levels suggest differences in soil cation exchange capacity and nutrient availability. The micronutrient levels exhibited variation, with copper (Cu) concentration ranging from 2.026 to 4.210 parts per million (ppm), zinc (Zn) concentration ranging from 0.736 to 4.440 ppm, manganese (Mn) concentration ranging from 19.0 to 79.0 ppm, and iron (Fe) concentration ranging from 44.36 to 160.64 ppm. The concentration of boron soluble in hot water varied from extremely low to medium (0.15 to 0.68 mg/kg), suggesting different degrees of boron accessibility for plant absorption. Finally, it is essential to fill the research gaps concerning soil fertility and nutrient dynamics in order to establish sustainable agricultural practices and guarantee food security in the region.

Elucidating the impact of environmental factors on the growth of Colletotrichum coccodes strains isolated from potato tubers in Great Britain

Black dot and silver scurf caused by Colletotrichum coccodes and Helminthosporium solani, respectively, are tuber blemish diseases affecting quality in the fresh and pre-pack potato industry. In the last 20 years, the importance of high-quality tuber appearance has increased considerably due to the growing demand for washed and pre-packed potatoes in the UK. Changing climate characterised by rising temperatures and wetter summers is a threat as this will favour the development of pathogens such as C. coccodes in the soil increasing the risk of food spoilage. Moreover, both diseases can develop not only in the field but also after harvest, with postharvest storage temperatures being a crucial factor in controlling fungal growth. Furthermore, anecdotal evidence showed differences on the aggressiveness of black dot depending on its origin (i.e. England and Scotland) on potato tubers. Silver scurf and black dot are difficult to differentiate as they present similar phenotypes characterised by silvery lesions making it challenging for managers to take the necessary corrective action during storage. Hence, the aim of this study was to give a general insight into the ecological conditions affecting the establishment of the causal agent of potato black dot in the field, and black dot and silver scurf during the supply chain. Therefore, invitro experiments were designed to study the growth rate and lag times simulating both scenarios respectively: on soil extract agar (SEA) media at different temperatures (4, 11, 15 °C) and matric potentials (control [unmodified] and − 1.4 MPa [modified]); and on natural potato dextrose agar (NPDA) for different temperatures (4, 11, 15 and 20 °C) at 99 % relative humidity (RH) for 25 days. When simulating the field environment, drier conditions (matric potential = −1.4 MPa) reduced fungal growth for both isolates by 0.1 cm day−1 at the temperature of 15 °C, suggesting temperature as the main limiting factor for the growth of C. coccodes in the soil. The causal agent of black dot exhibited a faster growth rate under retailer-like conditions (i.e., 15 °C) compared to H. solani. Understanding the environmental influence on both the pathogen and the crop is vital for proper disease management to help reduce food loss and waste.

Impact of Biotic and Abiotic Factors on Listeria monocytogenes, Salmonella enterica, and Enterohemorrhagic Escherichia coli in Agricultural Soil Extracts.

Outbreaks of Enterohemorrhagic Escherichia coli (EHEC), Salmonella enterica, and Listeria monocytogenes linked to fresh produce consumption pose significant food safety concerns. These pathogens can contaminate pre-harvest produce through various routes, including contaminated water. Soil physicochemical properties and flooding can influence pathogen survival in soils. We investigated survival of EHEC, S. enterica, and L. monocytogenes in soil extracts designed to represent soils with stagnant water. We hypothesized pathogen survival would be influenced by soil extract nutrient levels and the presence of native microbes. A chemical analysis revealed higher levels of total nitrogen, phosphorus, and carbon in high-nutrient soil extracts compared to low-nutrient extracts. Pathogen survival was enhanced in high-nutrient, sterile soil extracts, while the presence of native microbes reduced pathogen numbers. A microbiome analysis showed greater diversity in low-nutrient soil extracts, with distinct microbial compositions between extract types. Our findings highlight the importance of soil nutrient composition and microbial dynamics in influencing pathogen behavior. Given key soil parameters, a long short-term memory model (LSTM) effectively predicted pathogen survival. Integrating these factors can aid in developing predictive models for pathogen persistence in agricultural systems. Overall, our study contributes to understanding the complex interplay in agricultural ecosystems, facilitating informed decision-making for crop production and food safety enhancement.

Wide-energy programmable microwave plasma-ionization for high-coverage mass spectrometry analysis

Although numerous ambient ionization mass spectroscopy technologies have been developed over the past 20 years to address diverse analytical circumstances, a single-ion source technique that can handle all analyte types is still lacking. Here, a wide-energy programmable microwave plasma-ionization mass spectrometry (WPMPI-MS) system is presented, through which MS analysis can achieve high coverage of substances with various characteristics by digitally regulating the microwave energy. In addition, ionization energy can be rapidly scanned using programmable waveforms, enabling the simultaneous detection of biomolecules, heavy metals, non-polar molecules, etc., in seconds. WPMPI-MS performs well in analyzing real samples, rapidly analyzing nine toxicological standards in one drop of serum, and demonstrating good quantification and liquid chromatography coupling capability. The WPMPI-MS has also been used to detect soil extracts, solid pharmaceuticals, and landfill leachate, further demonstrating its robust analytical capabilities for real samples. The prospective uses of the technology in biological and chemical analysis are extensive, and it is anticipated to emerge as a viable alternative to commercially available ion sources.

Evaluation of five soil nutrient extraction methods for practical assessment of phosphorus and potassium availability for tomato (<i>Solanum lycopersicum</i>) fertilization in Andisols-Garut, Indonesia

Phosphorus and potassium are essential nutrients for plant growth and development. Plants will achieve optimum biomass and production if phosphorus and potassium needs are met through fertilization. Determining the availability of phosphorus and potassium in the soil is essential because it is related to decisions on phosphorus and potassium fertilizer rate recommendations. In this study, we evaluated 5 common phosphorus and potassium extraction methods by correlating the indicated soil nutrient levels to the relative biomass dry weight of tomato plants. The phosphorus and potassium extraction methods used were Mehlich-1, Bray-1, Morgan-Wolf, Ammonium acetate, and HCl-25%. Mean Root Error (MRE) and Root Mean Square Error (RMSE) were used to determine the precision of the linear regression equation model in predicting the relationship between phosphorus and potassium soil extraction methods and the relative biomass dry weight of tomato plants. The correlation of the soil extraction methods used in Andisols with the relative biomass dry weight of tomato was highly significant and very strong (r > 0.75) suggesting that Bray-1 was the best soil-phosphorus extraction method (P<sub>r</sub> = 0.88; P<sub>MRE</sub> = 0.10; P<sub>RMSE</sub> = 4.44), while HCl-25% was the most suitable for soil-potassium extraction (K<sub>r</sub> = 0.90; K<sub>MRE</sub> = 0.05; K<sub>RMSE</sub> = 2.95). The results of the two extraction methods will be used to determine the dosage of phosphorus and potassium fertilizers (<i>nutrient sufficiency approach</i>) for tomato plants grown in Andisols.

The soil sample conservation method and its potential impact on ammonium, nitrate and total mineral nitrogen measurements

Scientific literature for mineral soil nitrogen content (ammonium and nitrate) measurements usually differs regarding the chosen soil sample conservation method (fresh, frozen or air-dry) before soil extraction and analysis. In addition, most of the commonly used methodologies focus on the definition of the analysis processes, regardless of the previous sample conservation methodology. With the aim to fill this gap, we performed an analysis of the conservation method effect on the nitrate, and ammonium content in frozen or air-dried samples, comparing the results with direct fresh extraction. Moreover, the effects of additional soil parameters, such as soil texture, organic matter content or mineral nitrogen content range were also studied. The results showed that both, frozen and air drying soil samples, were capable of reliably preserving the N content of soil samples in most cases. However, some ammonium losses may occur in frozen samples when a high N content (>30 mg kg−1) is present. It was also observed that air-dried soil samples can reduce the soil nitrate and increase ammonium content in samples with a high N content. It was also observed that significant amounts of organic matter in soil can alter the mineral N measured depending on the conservation method chosen. On the other hand, the soil texture presented small effects on the mineral N measurements. In any case, a broader range of soils conditions (including i.e. pH or different natural organic matter content) should be further tested to confirm our findings.

Soil health indicators for predicting corn nitrogen requirement in long‐term cover cropping

AbstractEfforts to address economic and environmental concerns surrounding nitrogen (N) have motivated attempts to improve estimates of plant‐available N in soil. Several soil health indicators, including CO2 burst, permanganate oxidizable carbon (C) (POXC), and autoclaved‐citrate extractable (ACE) soil protein, assess labile C and N, and therefore may help to estimate soil N mineralization in long‐term cover cropping systems (>3 years). This study evaluated the relationship of CO2 burst, POXC, ACE‐soil protein, and pre‐sidedress nitrate test (PSNT) with agronomic optimum N rate (AONR) in corn (Zea mays L.). The study also looked at relationship between other soil test and corn yield parameters, relative yield (RY) and yield without N sidedress at 25 long‐term cover crop sites across Virginia. Results showed relatively weak correlations between AONR and CO2 burst, POXC, ACE‐soil protein, and NO3‐N (r = 0.00 to −0.48), which indicates that these soil health tests may not reliably predict soil N availability and corn yield. Corn yield with zero‐sidedress N rate had a negative relationship with cover crop C:N ratio (r = −0.66) and a positive relationship with cover crop N content (r = 0.59), and NO3‐N at pre‐planting (r = 0.54) and sidedress (PSNT) (r = 0.63). The PSNT showed a better relationship (r = 0.65) compared to 72‐h CO2 burst (r = 0.48) with RY. Soil health indicators (CO2 burst, POXC and ACE‐soil protein) resulted in a poor or no relationship with AONR. Our results indicate that the PSNT was a more reliable indicator of the sidedress N rate in corn.

Response of Arugula to Integrated Use of Biological, Inorganic, and Organic Fertilization.

This study evaluated the effects of solely and integrated application of inorganic (NPK), commercial organic (NC), and biological (MIX, mixed strains Ensifer meliloti and Azotobacter chroococcum) fertilizers on the chemical characteristics of arugula biomass and its yield, as well as changes in soil microbiological parameters after the experiment in relation to the control treatment (Ø). The experiment was performed in semi-controlled greenhouse conditions, in pots, from the 4th decade of March to the 2nd decade of September, in 2023, at three cutting times/swaths, during one agricultural season, with Vertisol soil. For soil characterization, the following parameters were analysed: granulometric composition using sieving and sedimentation procedure; soil acidity-potentiometrically; SOM-soil organic matter by Kotzmann method; total N using CNS analyser; available P-spectrophotometrically; available K-flame photometrically; total number of microorganisms on an agarized soil extract medium; fungi on a solid Czapek agar; actinomycetes on a solid Krasiljnikov agar with saccharose; Azotobacter spp. on a liquid Fyodorov medium with mannitol; ammonifiers on a liquid medium with asparagine; and dehydrogenase activity-spectrophotometrically. For plant characterization, the following parameters were determined: N and C, both on CNS analyser; P on spectrophotometer; K on flame photometer; air-dried yield biomass. A stimulative effect on all microbiological parameters was found in the treatment with integrated use of organic and biological fertilizer, except for fungi, which grew better in the treatments with separate inorganic and organic fertilizers. Generally, the stimulative impact on plant chemical parameters manifested in combined inorganic and biological, organic and biological, and inorganic and organic fertilization treatments, and was inhibited in treatment without fertilization, in all three swaths, which could also be stated for the plant yield. Positive influence of all fertilization treatments on chemical parameters was observed for the second swath in relation to the first and the third. The total yield in the NPK+MIX treatment was 121%, and in the NC+MIX treatment, it was 87% higher compared to the control (Ø). In general, integrated use of inorganic and biological, organic and biological, and inorganic and organic fertilizers, respectively, could be proposed as an optimal fertilization treatment in arugula cultivation.

Антибиотик ципрофлоксацин в водных и почвенных средах: реакция микроводорослей

Pharmaceuticals and antibiotics in the environment are of increasing concern due to the impact on representatives of all links in the food chain of natural ecosystems. The effect of the widespread antibiotic ciprofloxacin (Cip) on the green protococcal microalgae Scenedesmus quadricauda and Chlorella vulgaris in water and aqueous soil extracts (artificial standard soil, technosoil, soddy-podzolic soil) was studied in model experiments. Fluorescent parameters were assessed by two different methods (Fluorat 02-5M and Water-PAM devices). The phenomenon of hormesis was observed at low antibiotic concentrations of 5 and 10 mg/L. A decrease in the photosynthetic activity of algae was recorded at an increase of Cip content from 20 to 50 mg/L. A comparison was made of the median (average effective) concentration of the EC50 antibiotic, which suppresses the fluorescent characteristics of microalgae by 50% on 3 days of exposure in different media. The decrease in the toxicity of the studied dose of Cip (300 mg/L) in a number of studied objects can be represented as follows: water > technosoil > artificial standard soil > soddy-podzolic soil. It reflects the percentage of inhibition of the test function relative to the control (samples without antibiotic) by 91.5, 80.0, 62.5, and 60.0% respectively. In the soil matrix, the inhibitory effect of the antibiotic is less pronounced (by 10–30%), probably due to the protective properties of humic substances that adsorb the antibiotic or its metabolites.

Geochemical characteristics of saline soils formed during the recent retreat of the Caspian Sea

The objectives of this study are: 1- Determining geochemical characteristics and soil formation processes that lead to soil salinity. 2- To investigate the variability of soil properties across different geomorphic units. The coastal landforms of the Caspian Sea have experienced several seawater retreat and progress in recent decades, which has caused changes in terms of pedology and geomorphology. Routine soil properties, including soil cations and anions (Ca2+, Mg2+, Na+, K+, Cl-, SO42-, CO32–, and HCO3–), and total and available forms of some micro-elements (Fe, Mn, Zn, and Cu) of 136 samples collected from 0-20 cm of soils were analyzed according to standard methods. Mapping of the obtained results was done using inverse distance weighting (IDW) in ArcGIS 10.8. The results showed that although the main source of cations and anions in the soil solution is seawater, their concentration and changes in the soil solution are different depending on the processes carried out in soil. Mg2+, Na+, and Cl- were highly enriched in saturated soil extracts compared to seawater (261 %, 153 %, and 149 % respectively). While, K+ and Ca2+, increased by 81 % and 47 % accordingly, and HCO3– and SO42-, decreased by −56 % and −25 % due to precipitation of carbonate and gypsum in the soil. Total and available forms of micro-nutrients were high across the study area. The distribution pattern of the total micro-nutrients follows the type of landforms (affecting drainage condition) and their clay contents (mineralogical composition and abundance), however, the available form of micro-nutrients depends on soil moisture conditions and proximity or distance to the coastline. The results showed that the chemistry of seawater is the main factor controlling the chemical and physical properties of soils and their distribution patterns. The geochemical processes of soil formation cause special interactions between the components of soil solution, which leads to the removal of carbonate, bicarbonate, and sulfate from the soil solution and precipitation with calcium as calcium carbonate and calcium sulfate.