Higher Soil Organic Matter Research Articles

The activity and functions of soil microbial communities in the Finnish sub-Arctic vary across vegetation types.

Due to climate change, increased microbial activity in high-latitude soils may lead to higher greenhouse gas (GHG) emissions. However, microbial GHG production and consumption mechanisms in tundra soils are not thoroughly understood. To investigate how the diversity and functional potential of bacterial and archaeal communities vary across vegetation types and soil layers, we analyzed 116 soil metatranscriptomes from 73 sites in the Finnish sub-Arctic. Meadow soils were characterized by higher pH and lower soil organic matter (SOM) and carbon/nitrogen ratio. By contrast, dwarf shrub-dominated ecosystems had higher SOM and lower pH. Although Actinobacteria, Acidobacteria, Alphaproteobacteria and Planctomycetes were dominant in all communities, there were significant differences at the genus level between vegetation types; plant polymer-degrading groups were more active in shrub-dominated soils than in meadows. Given that climate-change scenarios predict the expansion of shrubs at high latitudes, our results indicate that tundra soil microbial communities harbor potential decomposers of increased plant litter, which may affect the rate of carbon turnover in tundra soils. Additionally, transcripts of methanotrophs were detected in the mineral layer of all soils, which may moderate methane fluxes. This study provides new insights into possible shifts in tundra microbial diversity and activity due to climate change.

High initial soil organic matter level combined with aboveground plant residues increased microbial carbon use efficiency but accelerated soil priming effect

High initial soil organic matter level combined with aboveground plant residues increased microbial carbon use efficiency but accelerated soil priming effect

Sustainable intensification of agriculture improves soil nitrogen in the Argentinean Humid Pampas

AbstractIn the Argentinean Humid Pampas, intensification practices like crop rotation, cover crops (CC), and fertilization can improve soil N balance. This study aimed to assess how intensification practices affect soil organic N (Norg), Norg in the particulate fraction (PF‐Norg), and N mineralized during a short‐term (7 d) anaerobic incubation (aN) in a 4‐yr experiment with soybean [Glycine max (L.) Merr.]‐based crop sequences. At two sites differing in initial soil organic matter (SOM), five crop sequences were evaluated: continuous soybean (Sb); continuous soybean fertilized with P and sulfur (S; Sbf); CC/PS‐fertilized soybean (Sbf/CC); N‐fertilized CC/PS‐fertilized soybean (Sbf/CCf); NPS‐fertilized crop rotation (Rot). In addition, at one site we evaluated the C and N accumulation in CC dry matter, CC inclusion effect on soil inorganic N dynamics, and C and N content in soybean grain and shoots. At Site 1 (low SOM), Norg and PF‐Norg increased in intensified sequences as compared with Sb and Sbf, whereas no differences among treatments were detected at Site 2 (high SOM). Also, an increase in aN was observed in intensified treatments at both sites. At Site 2, soil sampling took place at soybean sowing and harvest during two growing seasons. At soybean sowing, Sb and Sbf presented ∼30 kg NO3−–N ha−1 more than intensified sequences, whereas at soybean harvest this trend was the opposite. In the fallow, CC captured N, minimizing N leaching without affecting N accumulation in soybean. Our results indicate that intensification in soybean‐based sequences improves soil N balances.

Evaluating the particle densities of subarctic soils using pedotransfer functions and vis–NIR spectroscopy

AbstractThe particle density (ρs) is a fundamental physical property needed for calculating the soil porosity and phase distributions. While ρs is often estimated using soil organic matter (SOM) content and particle size distribution, the specific densities of each soil component remain unclear in a subarctic agricultural setting. This study aimed to evaluate the ρs of soils from Southwest Greenland using a three‐compartment model (3CM) based on the mixing ratio of SOM derived from loss‐on‐ignition, mineral particles <20 μm (FC), and mineral particles ≥20 μm (CC). We further evaluated the accuracy of the 3CM against pedotransfer functions (PTFs) and visible near‐infrared (vis–NIR) spectroscopic models. A total of 324 soil samples from 16 Greenlandic agricultural fields were investigated, covering a wide range in SOM content (0.021–0.602 kg kg–1) and clay content (0.020–0.185 kg kg–1). Despite their high SOM content, the Greenlandic soils exhibited relatively high ρs (1.936–3.044 Mg m–3), which together with a large SOM/organic carbon ratio of 2.16 indicated a high SOM density of 1.493 Mg m–3. The 3CM fit on all soils indicated FC and CC densities of 3.047 and 2.713 Mg m–3, respectively, while a subset of soils (n = 203) from the same geological setting resulted in FC and CC densities of 2.738 and 2.731 Mg m–3. Prediction accuracy of the 3CM (RMSE = 0.067 Mg m–3) was similar to PTFs (RMSE = 0.068–0.070 Mg m–3) and better than vis–NIR spectroscopic models (RMSE = 0.091 Mg m–3).

Carbon pathways in aggregates and density fractions in Mollisols under water and straw management: Evidence from 13C natural abundance

Mollisols have a high potential to mitigate climate change and play an important role in the global carbon (C) cycle due to their inherently high soil organic matter (SOM). However, little is known about the mechanism of C stabilization in Mollisols, especially subjected to different management effects. To trace C stabilization between aggregates and SOM density fractions in Mollisols, soil samples were collected from different experimental plots: controlled irrigation + rice (Oryza sativa L.) straw removal (CI), flooded irrigation + rice straw removal (FI), controlled irrigation + rice straw return (CI-SR), and flooded irrigation + rice straw return (FI-SR). Each soil sample was separated into three aggregate size classes (>250 μm, 53–250 μm, and <53 μm), then each class individually subjected to density fractionation to obtain free and occluded light fractions (fLF and oLF), as well as dense and mineral-heavy fractions (DF and MF). The overall C content and 13C abundance of fractions were measured to interpret C transfer and accumulation among aggregate and density fractions. The highest increase in the soil organic C (9.27–24.88%) was observed in CI-SR compared with the other treatments. Irrigation and straw return primarily affected C accumulation within macroaggregates and the MF, which were the dominant forms in the aggregates and density fractions, respectively. An enrichment in δ13C was found from macroaggregates to silt + clay, and from light to heavy fractions, indicating that Mollisols macroaggregates and light fractions acted as the source or initial store of plant residues, and that the C in the silt + clay class and heaviest fraction contained more microbially-transformed C than did the macroaggregates and light fractions. A detailed scheme of C transfer within aggregates and SOM fractions based on the δ13C natural abundance revealed the following general sequence: free light → occluded light → dense → mineral fractions, concurring with results reported at upland sites. There is a greater probability of C transfer between SOM density fractions under CI. This contrasted with the results that CI decreases the possibility of C exchange between aggregates than FI, which indicates differences in the C stabilization processes between no-flooded and flooded conditions of Mollisols. In addition, straw returning can reduce the possibility of C exchange both between and within aggregates, which plays a significant role in maintaining the stability of the Mollisols carbon cycle. The present study provides further detailed insights into the C stabilizing mechanisms in Mollisols which depend on management (straw, water status). This finding is conducive to the sustainable use and management of Mollisols toward maintaining or increasing C stock and in realizing the objective of C-neutral agriculture.

Soil and climate effects on winter wine produced under the tropical environmental conditions of southeastern Brazil

Southeastern Brazil is an emergent region in terms of the production of high-quality fine wines. To contribute to typicity assessment, the soils (morphology, mineralogy, chemical and physical analyses), parent material (geologic maps and portable X-ray fluorescence spectrometry) and climate (temperature and precipitation) were characterized in seven vineyards located in the state of Minas Gerais and São Paulo, Brazil, by carrying out state-of-the-art terroir analysis and assessing the environmental variations of the study sites. A soil profile was described and sampled in the central part of each vineyard. Principal Component Analysis (PCA) biplots were used to analyze the relationships between these factors and the composition of wines (2016, 2017 and 2018 harvests) produced from Syrah in commercial vineyards in different municipalities of Três Corações (TC), Cordislândia (COR), Andradas (AND), São Sebastião do Paraíso (SSP), Três Pontas (TP), Espírito Santo do Pinhal (PIN) and Itobí (ITO). The vineyards were grouped according to soil and climate characteristics. Group A was composed of COR, AND and PIN vineyards, which exhibited the highest correlation with soil Al3+ content and accumulated rainfall. The group’s wines had the lowest ash alkalinity, total polyphenol index (TPI) and pH values and the highest fixed acidity. Group B consisted of the TP and TC vineyards, which had the highest soil organic matter and boron contents and the highest thermal amplitude with similar values (15.4 °C in TC and 15.2 °C in TP); their wines showed average composition. Group C comprised ITO alone, which was characterized by the shallowest and least developed soils. Its wine had the highest flavonol content and high dry extract, color intensity, TPI, alcohol content and sugar values. Group D contained the SSP vineyard, in which the soil subsurface horizons were correlated with the highest wine pH. Late harvest in this vineyard caused the most dehydration of grapes and consequent concentration of most wine compounds (human effect on terroir). The terroir information produced in this study adds substantial value to the wines produced under the tropical environmental conditions of southeastern Brazil, for which such studies are very rare. By characterizing the natural factors (soil, soil parent material and climate) and human factors (vineyard management and wine characteristics) related to terroir, this study can also provide historical information about the wine from this emergent region (the historical factors). In addition, its results can be used to guide producers in their choice of vineyard cultivation sites according to preference in wine composition.

Growth of soil microbes is not limited by the availability of nitrogen and phosphorus in a Mediterranean oak-savanna

The environmental conditions under which the availability of inorganic nutrients such as nitrogen (N) and phosphorus (P) influence soil microbial growth are poorly understood, especially with regards to how fertilization changes specific aspects of microbial growth such as carbon-use efficiency (CUE). Microbial CUE is the fraction of C converted into biomass out of all C taken in and plays a critical role in global C budgets. Using the 18O labeled water method we tested short vs. long-term effects of N and/or P fertilization on microbial growth, CUE, and C, N, and P-acquiring enzyme activities in two soils from an oak-savanna, which differ in their soil organic matter (SOM) content. We hypothesized that soils with more SOM (from under tree canopies) would have higher microbial growth rates than soils with less SOM (from open grassland), and that microbial growth and CUE would increase with fertilization. We further hypothesized that these increases would be associated with a decrease in enzyme activity and a shift towards older SOM substrates in the short-term, in contrast to substrates from recently fixed C resulting from increased plant productivity in the long-term. We found that nutrient additions did not affect microbial growth or CUE in the relatively high SOM habitat on either time scale. In contrast, the low SOM habitat had lower growth and CUE when single nutrients were added, with significantly reduced growth when P alone was added, but was unchanged when N and P were added together. Our results show that short-term, stoichiometric imbalances can reduce microbial growth and that microbial growth at this site is limited not by nutrients but by the amount of C available to soil microbes.

TRACE METAL LEVELS OF SOIL-GROWN AMARANTHS ON MUNICIPAL SOLID WASTE DRAINAGE OF WUKARI METROPOLIS

Soil metal levels of municipal solid waste (MSW) drainage and morphological traits of Amaranthus spp growing in the natural drainage of Wukari Metropolis was investigated as an ecological monitoring data survey and food chain contamination assessment. Selected morphological traits, physico-chemical parameters and the status of selected trace metal (Cr, Cu, Ni, Pb, Zn) levels of the municipal solid waste drainage used for dry season cultivation of Amaranthus spp were determined according to standard analytical procedures. Results reveals a significant soil Pb and Cr levels in the MSW drainage arising from traffic density fallouts. A higher soil organic matter content, slightly acidic pH and CEC of MSW drainage indicate the suitability of MSW drainage for Amaranths cultivation as reveals in the selected morphological traits which agrees with the findings of other works. This reflect high microbial activity in the compositing of MSW in the drainage. Trace metal levels were below the Joint WHO/FAO Codex Alimentarius permissible limits (Pb = 2mg/kg; Cr = 1.30mg/kg; Cu = 10mg/kg; Zn = 5mg/kg) but higher for Cr and Pb revealing the close proximity of study area to high traffic density of the Katsina –Ala – Jalingo Highway. Dry season irrigation farming of vegetables should be far from high traffic density. Natural treatment of MSW and subsequent utilization of drainages or dumpsites for dry season vegetable farming is environmentally-friendly than the application of inorganic fertilizers that pollute agricultural soils, groundwater surface waters and the soil ecosystem.&#x0D; &#x0D; Keywords - Municipal Solid Waste, Drainage, Dumpsite, Trace Metals, Amaranths,&#x0D;

Correlation of Organic Carbon Content of Soil on Paddy Productivity: A Case Study

Soil fertility is one of the important factors controlling yield of the crops. Macronutrients (N, P, K and S) are important soil elements which control its fertility. Soil characterization in relation to evaluation of fertility status of the soils of an area or region is an important aspect in context of sustainable agriculture production. A high SOM (Soil Organic Matter) content provides nutrients to plants and improves water availability, both of which enhances soil fertility and ultimately improve food productivity. Since 2017 ARF with support of NABARD has been conducting trials on 300 acres of agriculture land of villages of district Sonipat, Haryana using hydroponically grown Paddy nursery. A study was carried out on randomly selected 50 acres of land to see the effect of SOC (Soil Organic Carbon) and N (Nitrogen) content on the yield in hydroponically grown paddy.

Global analysis of nitrogen fertilization effects on grain zinc and iron of major cereal crops.

Human zinc (Zn) and iron (Fe) deficiencies can partly be alleviated by enhancing cereal concentrations of these micronutrients. Soil nitrogen (N) levels codetermine cereal grain yields and Zn and Fe nutrition of plants and grains. Grain Zn and Fe concentrations have been reported to be affected by both yield dilution and enhanced acquisition and grain allocation of Zn and Fe. A global meta-analysis of 100 publications concerning wheat, maize, and rice providing 785 records of Zn and 506 records of Fe allowed us to assess their relative importance and quantify the concentrations and bioavailability of Zn and Fe in major cereal grains over a wide range of N fertilization levels. Compared with the no N controls, N application significantly increased grain Zn and Fe concentrations in all crops except maize Zn. The increase in grain protein concentration correlated positively with the increases in Zn and Fe concentrations in all cereals except Zn in maize. In rice, the grain Zn and Fe concentration increase was independent of the rate of N applied. Grain concentrations of Zn and Fe in wheat and Fe in maize were positively correlated with N rate but were only higher than those in the controls above 40–60 kg N ha−1. At lower N rates, the dilution effect was thus stronger than the enhancement effect. N supply had a larger effect on Zn and Fe concentrations in loamy textured soils or at lower soil available N and phosphorus (P), or higher soil organic matter and available Zn contents or with P and Zn fertilization, but the effect sizes differed among crops. Reductions in phytic acid concentration after N fertilization occurred in wheat, potentially improving micronutrient bioavailability. Thus, our findings indicate that N fertilization could be managed in ways that simultaneously support high grain yields and enhance nutritional quality for major cereals.

Effect of Organic and Conventional Cereal Production Methods on Fusarium Head Blight and Mycotoxin Contamination Levels

Fusarium mycotoxins in cereals constitute major problems for animal and human health worldwide. A range of plant pathogenic Fusarium species that can infect cereal plants in the field are considered the most important source of mycotoxins, such as deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin, and HT-2 toxin, in small-grain cereal crops in temperate climates. In this article, we (i) critically review the available knowledge on the impact of contrasting production systems (organic versus conventional) and specific agronomic parameters on the occurrence and concentrations of DON, ZEA, and T-2/HT-2 in small-grain cereals (wheat, oats, barley, and rye), and (ii) discuss Fusarium mycotoxin risks in the context of the need to develop more sustainable cereal production systems. Overall, the available evidence from studies of acceptable scientific quality suggests that the incidence and concentrations of Fusarium mycotoxin are lower in organic compared with conventional cereals. Specifically, 24 comparisons showed lower mycotoxin levels in organic production, 16 detected no significant difference, and only 2 showed higher levels in organic production. When the mean concentrations from all studies were compared, conventionally produced cereals had 62%, 110%, and 180% higher concentrations of DON, ZEA, and T-2/HT-2, respectively, than organic cereals. Overall, published studies on the effects of specific agronomic practices on mycotoxin levels suggest that diverse crop rotations and high soil organic matter content/biological activity are associated with a lower risk of Fusarium mycotoxin contamination, whereas (i) high mineral nitrogen fertiliser inputs, (ii) some fungicides and herbicides, and (iii) minimum or no tillage may increase the risks of Fusarium mycotoxin contamination in cereals. The management of Fusarium head blight and mycotoxins, therefore, requires a preventative, integrated, holistic agronomic approach.

ANALYTICAL STUDY ON SOIL FERTILITY STATUS ALONG WITH ELEVATION GRADIENT AND DEPTH OF CHITWAN–MUSTANG TRACK, NEPAL

The distribution of soil properties under different elevations and soil depths was evaluated by taking soil samples from peripheral agricultural land of Chitwan to the Mustang roadway track with the integrated use of the Geographical Information System (GIS). Soil organic matter (SOM), total nitrogen (N), available phosphorous (P2O5), available potassium (K2O), and soil ph. were determined on 10 samples each from 0-15 cm and 15-30 cm soil depths of each categorical elevation (194-604 masl, 604-1399 masl, 1300-2846 masl) were analyzed (Total 60 samples). The highest SOM (4.21%) was recorded at surface soil (0-15 cm) of elevation 1300-2846 masl. The highest total nitrogen (0.245%) was also found at the surface layer of elevation 1300-2846 masl. Phosphorous and Potassium were highest at the surface layer of elevation 1300-2846 masl. The available nutrients Nitrogen, Phosphorous, and Potassium were medium in range and decrease with the increase in depth, which might be due to in-situ in a corporation of leaf litters, residue, etc. as well as applied manure on the surface. In general, the study result revealed altitude did not impose any significant effect in aggravating soil reaction and phosphorous. Whereas soil depth affected significantly not only ph. but also SOM and available potassium. Thus, the study concludes the increasing trend of primary nutrients with increasing elevation and decreases with increasing depth.

Optimization of Reclamation Measures in a Mining Area by Analysis of Variations in Soil Nutrient Grades under Different Types of Land Usage—A Case Study of Pingshuo Coal Mine, China

The development of reclaimed mine soils is normally spatially heterogeneous, making the fine management and utilization of reclaimed mined lands difficult. Soil nutrient grading can provide a scientific basis for the precise regulation of soil nutrients, but few related studies are available in reclaimed mined areas. This study aimed to quantify the spatiotemporal variations in soil nutrient grades under different land-use types in a reclaimed mined area on the Loess Plateau, China. The study area was graded by four soil nutrients (soil available potassium (SAK), soil available phosphorus (SAP), soil total nitrogen (STN), and soil organic matter (SOM)), and the variation features of soil nutrient grades in the initial stage of reclamation under four land-use types (i.e., cultivated land, grassland, forestland, and barren land) were systematically characterized by geostatistical analysis, pedodiversity analysis, and correspondence analysis. The results show that during the initial five years after reclamation, the soil nutrient grades of most reclaimed areas increased from Grade V and VI to Grade I–IV, while the improvements were significantly heterogeneous. Notably, the four land-use types had distinct variation characteristics. The barren land had the lowest SAP level, whereas it had the highest proportion, and medium–high grades of SAK, STN, and SOM (88.3, 100.0, and 100.0%, respectively). In terms of quantitative structure, it had the lowest richness index (S′, 2.5) and Shannon’s entropy index (H′, 0.7) and the highest evenness index (E′, 0.8). These results suggest that the barren land had relatively high and balanced nutrients, with the highest homogeneity among the four land-use types. The grassland had considerable improvement in all nutrients (especially SAP; 95.6% of the area had high SAP grades); however, its improvement was the most heterogeneous (S′ = 4.5, E′ = 0.7). As the second-most heterogeneous land-use type (S′ = 4.0, E′ = 0.8), the forestland had relatively low STN, SAP, and SAK levels due to high nutrient uptake and storage by tree species, but it had the highest proportion of area that reached high SOM grades (36.4%) and medium to high SOM grades (100.0%) due to its high community productivity. The cultivated land, which received fertilization for an additional three years, was the most imbalanced in terms of nutrients. It had the highest proportion of area that reached high SAP grades (98.0%); in contrast, its area proportions of low-grade SAK and SOM (69.0 and 32.9%, respectively) were the highest among the four land-use types. Based on the above comprehensive characterization of soil nutrient grade variation, guidance was given for fine management of reclaimed mined land and the optimization of reclamation measures.

Engineered resistance and risk assessment associated with insecticidal and weeds resistant transgenic cotton using wister rat model

Stacking multiple genes into cotton crop to cop up multiple biotic stresses such as insects and weeds is a promising tool to save crop from losses. Transgenic cotton variety, VH-289, with double Bt and cp4EPSPS genes under the control of 35S promoter was used for the expression analyses and biosafety studies. The transgenic cotton plants were screened through PCR amplification of fragments, 1.7 kb for Cry1Ac, 582 bp for Cry2A and 250 bp for cp4EPSPS; which confirmed the presence of all genes transformed in transgenic cotton. The Cry1Ac + Cry2A and cp4EPSPS proteins were quantified through ELISA in transgenic cotton plants. The Glyphosate assay performed by spraying 1900 mL per acre of glyphosate Roundup further confirmed complete survival of transgenic cotton plants as compared to the non-transgenic cotton plants and all weeds. Similarly, insect infestation data determined that almost 99% insect mortality was observed in controlled field grown transgenic cotton plants as compared to the non-transgenic control plants. Evaluation of effect of temperature and soil nutrients availability on transgene expression in cotton plants was done at two different cotton growing regions, Multan and Lahore, Pakistan and results suggested that despite of higher temperature in Multan field, an increased level of Cry and cp4EPSPS proteins was recorded due to higher soil organic matter availability compared to Lahore field. Before commercialization of any transgenic variety its biosafety study is mandatory so, a 90 days biosafety study of the transgenic cotton plants with 40% transgenic cottonseeds in standard diet showed no harmful effect on wister rat model when studied for liver function, renal function and serum electrolyte.

Long-Term Impacts of Different Cropping Patterns on Soil Physico-Chemical Properties and Enzyme Activities in the Low Land Plain of North China

Various cropping patterns are extensively used on the North China Plain, which greatly alter various soil properties. Although these soil properties respond differently to the different cropping patterns, little is known about the possible effects of cropping patterns on desalinized soils. To assess the effects of the different cropping patterns on soil properties and enzyme activities, a long-term field experiment was conducted at the Nanpi Agro-Ecological Station in Hebei Province, China. The cropping patterns under study were the single-cropping patterns of winter wheat (Triticum aestivum L.), spring maize (Zea mays), and spring cotton (Gossypium hirsutum), and the double-cropping pattern of winter wheat–summer maize (WW–SM), which is the predominant cropping pattern on the North China Plain. Soil samples were collected at a depth of 0–100 cm, depending on the soil properties. Our results indicated that soil available phosphorous (P) and available potassium (K) concentrations at 0–20 cm were greater than those of the subsurfaces. Soil organic matter declined with depth, and WW–SM had the highest amount in the deep levels. The WW–SM cropping pattern also generally showed greater levels of enzyme activities than did the single-cropping patterns, proving that diverse crops can enhance enzyme activities. Soil pH generally increased with depth despite there being no significant differences between the cropping patterns. No significant effects were observed on soil electrical conductivity (EC). However, EC generally increased with depth in spring cotton and winter wheat and declined in spring maize and WW–SM. Winter wheat had a significant aggregate size (&lt;0.053 mm) at 20–40 cm depth and generally showed the lowest amount of nutrients. This study suggests that a fallow period allows the soil to regenerate its structure, whereas WW–SM enhances high soil organic matter in the deep soil layers and promotes increased soil enzyme activities. This indicates that crop rotation could sustainably exploit soil resources without reducing fertility over a long period. There is a need to incorporate different soil management practices for single-cropping patterns to increase their productivity, especially in spring maize, whose organic matter declined the most. Our results also show a need to diversify to different crop rotations to utilize their benefits and enhance soil productivity while increasing crop output.

Fate of contaminants of emerging concern in the reclaimed wastewater-soil-plant continuum

Reclaimed wastewater irrigation, a common agricultural practice in water-scarce regions, chronically exposes the agricultural environment to a wide range of contaminants of emerging concern (CECs) including pharmaceuticals and personal care products. Here we provide new data and insights into the processes governing the translocation of CECs in the irrigation water-soil-plant continuum based on a comprehensive dataset from 445 commercial fields irrigated with reclaimed wastewater. We report on CEC exposures in irrigation water, soils, and edible produce (leafy greens, carrots, potatoes, bananas, tomatoes, avocados, and citrus fruits). Our data show that CEC concentrations in irrigation water and their physiochemical properties (mainly charge and lipophilicity) are the main factors governing their translocation and accumulation in the soil-plant continuum. CECs exhibiting the highest detection frequency in plants (lamotrigine, venlafaxine, and carbamazepine) showed a reduction in their leaf accumulation factor with increasing soil organic matter content. The higher soil organic matter likely reduced the available CEC concentration in the soil solution due to soil-CEC interactions, leading to reduced uptake. Interestingly, the concentration of carbamazepine in the leaves showed a saturation-like trend when plotted against its concentration in the soils. This probably resulted from steady-state conditions when uptake equals in-planta decomposition. Our data indicate that due to continuous reclaimed wastewater irrigation, the soil acts as a sink for CECs. CECs in the soil reservoir can be desorbed into the soil solution during the rainy season and be taken up by rain-fed crops.

Mapping atrazine persistence in soils of central Argentina using INLA

The length of time an herbicide remains in soils can be used as an indicator for diffuse pollution assessment. Atrazine, a residual herbicide with a wide range of reported environmental impacts, has been extensively applied in agricultural soils cultivated with gramineous crops. While atrazine persistence in soils has been widely studied by quantifying half-life from experimental dissipation curves, the spatial variability of half-life at the landscape scale has not been sufficiently explored. The objectives of this work were to estimate atrazine dissipation in a variety of soils and to map its spatial variability by modelling half-life as a function of environmental variables. Based on laboratory determination and environmental data, atrazine dissipation in soils was mapped across the territory of Córdoba province, central Argentina. First, we determined the dissipation parameters of atrazine under a variety of environmental conditions in 60 sites. Second, we fitted a Bayesian hierarchical model for the estimated atrazine half-lives, considering a soil site-specific property (soil organic carbon, SOC) and land use (gramineous crop, non-gramineous crop, pasture, and forest) as covariates. We used Integrated Nested Laplace Approximation and stochastic partial differential equations to model the spatial dependence on random effects. The results suggest that atrazine half-life can be spatially predicted by SOC and land use. Atrazine dissipation was faster in sites with previous gramineous crops and high soil organic matter. The digital map allowed us to quantify the environmental variability of atrazine dissipation in Córdoba (3.2–99.5 days). The modelling strategy might be applied to other herbicide compounds by selecting proper environmental covariates.

Quantitative relationship between earthworms’ sensitivity to organic pollutants and the contaminants’ degradation in soil: A meta-analysis

Using earthworms to remove soil organic pollutants is a common bioremediation method. However, it remains challenging to evaluate and predict their effect on removing soil organic pollutants based on earthworm toxicology and pollutant degradation rates. Peer-reviewed journal articles on ecotoxicology and bioremediation from the years 1974–2020 (cutoff date September 2020) were selected for meta-analysis to quantify the effect size of earthworms on organic pollutant degradation. The meta-analysis shows that the average effect size of earthworms on organic pollutant degradation is 128.5% (p < 0.05). Soils with high soil organic matter or clay textures are more conducive to earthworm-mediated removal of organic pollutants. Structural equation modeling reveals that earthworms’ sensitivity to contaminant exposure may be a greater limiting factor on pollutant degradation than environmental factors. In addition, the quantitative relationship existed between LC50 and the pollutants’ degradation that an elevated LC50 threshold resulted in at least 1.5 times increase in the pollutants’ degradation size. This correlation was dually confirmed via meta-analysis and the validation trial. The results of this study contribute to a more profound understanding of the potential to use earthworms to mitigate organic pollution in soils and develop earthworm-based soil remediation techniques on a global scale.

Plant organic matter inputs exert a strong control on soil organic matter decomposition in a thawing permafrost peatland

Peatlands are climate critical carbon (C) reservoirs that could become a C source under continued warming. A strong relationship between plant tissue chemistry and the soil organic matter (SOM) that fuels C gas emissions is inferred, but rarely examined at the molecular level. Here we compared Fourier transform infrared (FT-IR) spectroscopy measurements of solid phase functionalities in plants and SOM to ultra-high-resolution mass spectrometric analyses of plant and SOM water extracts across a palsa-bog-fen thaw and moisture gradient in an Arctic peatland. From these analyses we calculated the C oxidation state (NOSC), a measure which can be used to assess organic matter quality. Palsa plant extracts had the highest NOSC, indicating high quality, whereas extracts of Sphagnum, which dominated the bog, had the lowest NOSC. The percentage of plant compounds that are less bioavailable and accumulate in the peat, increases from palsa (25%) to fen (41%) to bog (47%), reflecting the pattern of percent Sphagnum cover. The pattern of NOSC in the plant extracts was consistent with the high number of consumed compounds in the palsa and low number of consumed compounds in the bog. However, in the FT-IR analysis of the solid phase bog peat, carbohydrate content was high implying high quality SOM. We explain this discrepancy as the result of low solubilization of bog SOM facilitated by the low pH in the bog which makes the solid phase carbohydrates less available to microbial decomposition. Plant-associated condensed aromatics, tannins, and lignin-like compounds declined in the unsaturated palsa peat indicating decomposition, but lignin-like compounds accumulated in the bog and fen peat where decomposition was presumably inhibited by the anaerobic conditions. A molecular-level comparison of the aboveground C sources and peat SOM demonstrates that climate-associated vegetation shifts in peatlands are important controls on the mechanisms underlying changing C gas emissions.

Development of a new model for health assessment in agroecosystems.

Healthy agroecosystems provide a range of ecosystem services, and the lack of information about the importance of their health degree leads to the unsustainability of these agroecosystems. To assess the health status of agroecosystems, a model was developed using spatial analysis-based procedures in Geographic Information System (GIS) media, surveyed data, and field monitoring at Gorgan University of Agricultural Sciences and Natural Resources. Initially, a survey-based study was conducted in 50 barley fields of Bandar-e-Torkaman County, north of Iran, during the 2016-2017years. Then, the health index maps were provided by spatial analysis-based functions in GIS media. For accurate estimation of health status in barley agroecosystems, some meteorological variables were layered. Finally, the health status of the agroecosystems was determined based on six indices, including pesticides consumption rate, chemical fertilizers consumption rate, crop yield, and cultivar type, soil organic matter, and biodiversity indices. When all the layers overlaid, only 12% of the surveyed agroecosystems were located in the healthy class. The use of proper tillage methods, the appropriate weed control operations, the optimum consumption of high-quality pesticides, high soil organic matter, and grain yield > 2.6 ton ha-1 were the main reasons for obtaining of health degree in these agroecosystems. In contrast, the consumption of low-quality pesticides, the use of inappropriate tillage tools and machinery, the little knowledge of the farmers about the optimum rates and consumption methods of pesticides and chemical fertilizers, and resistance of some weeds to herbicides were identified as the most essential reasons for non-health status in the most surveyed barley agroecosystems.