Typical Agricultural Soils Research Articles

Biogeographic distribution, assembly processes and potential nutrient cycling functions of myxobacteria communities in typical agricultural soils in China

Predatory myxobacteria are important soil micropredators with the potential to regulate soil microbial community structure and ecosystem function. However, the biogeographic distribution patterns, assembly processes, and potential nutrient cycling functions of myxobacteria communities in typical agricultural soils in China are still poorly understood. High-throughput sequencing, phylogenetic zero modeling, and the multi-nutrient cycling index were used to assess the biogeographic distribution, assembly processes, and soil ecosystem functions of predation myxobacteria communities in typical agricultural soils of six long-term fertilization ecological experimental stations. The results demonstrated a hump-shaped distribution of myxobacteria α-diversity along the latitudinal gradient and significant differences in myxobacteria β-diversity in typical agricultural soils (P < 0.05). Bacterial richness, soil organic carbon, and pH were the most important predictors of myxobacteria α-diversity, whereas geographic factors and soil pH were the most significant ecological predictors of myxobacteria β-diversity. Myxobacteria community assembly is dominated by deterministic processes, especially homogeneous selection, primarily driven by soil pH and bacterial richness. In addition, we revealed the ecological significance of myxobacteria communities in typical agricultural soil microbial networks and the potential link between myxobacteria communities and soil nutrient cycling. These findings enhance our understanding of the biogeographic distribution, community assembly, ecological predictors, and relationships with soil nutrient cycling of myxobacteria communities in typical agricultural soils, paving the way for a more predictive understanding of the effect of predatory myxobacteria communities on soil ecosystem function, which is essential for the development of sustainable agriculture.

Identification of antibiotic resistant bacteria communities and a GeoChip based study of resistome in Fusarium wilt diseased and healthy soil

Soil plays a crucial role as a significant reservoir for antibiotic resistance genes (ARGs). Despite the extensive research conducted in this area, there remains a need for further investigation, particularly concerning diverse types of agricultural soil. This comprehensive study examined Fusarium wilt diseased and healthy soil samples to investigate the spectrum of ARGs and identify bacteria potentially harboring these genes. The level of antibiotic resistance (AR) in the two soil types was detected by using culture plate counts (PC). We quantified and identified antibiotic resistant bacteria (ARB) against nine antibiotics. From the PC results, the relative number of ARB (number of ARB/total number culturable bacteria) resistant to erythromycin, lincomycin, sulfonamides, streptomycin sulfate, kanamycin, and enrofloxacin in the diseased soil was significantly higher than that in the healthy soil (One-way ANOVA, p < 0.01). The GeoChip (version 5.0) was employed to identify ARGs and antibiotic biosynthetic genes (ABGs). Interestingly, despite the presence of similar ARGs in both soil types, the Fusarium wilt diseased soil demonstrated a significantly elevated abundance of the tetracycline (tetX) resistance gene compared to the healthy soil. A robust correlation (r ≥ 0.8) between multidrug efflux pumps and ARGs indicates that natural antibiotics as selective pressures for transportation mechanisms. Our analysis identified diverse ARB phylotypes and multiple ARGs in both soil types. Incorporating these soil types into ARGs risk assessments and relevant monitoring is essential for a comprehensive understanding of AR dynamics in various environments.

Molecular weight of dissolved organic matter determines its interactions with microbes and its assembly processes in soils

Dissolved organic matter (DOM) is involved in numerous biogeochemical processes, and its molecular weight affects many of these processes through its bioavailability and sorptive capacity. However, it remains unknown to what extent the molecular weight of DOM mediates its dynamics, for example, influencing its role in DOM-microbe interactions and the processes determining the compositional assembly of DOM. To address this issue, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and high-throughput sequencing were applied to investigate how the molecular weight of DOM was associated with its dynamics in two typical agricultural soils with different fertility. Our results showed that low-molecular-weight DOM had lower biological stability and a higher transformation potential. Analysis of the DOM-microbe co-occurrence network showed that low-molecular-weight DOM displayed tighter interactions with a diversity of microbes, while high-molecular-weight DOM interacted with only a few microbes. Ecological null models revealed that the compositional assembly of low-molecular-weight DOM, but not high-molecular-weight DOM, was more controlled by deterministic processes. Taken together, our results demonstrate the fundamental role the molecular weight of DOM plays in determining biological stability, transformation potential, interactions with microbes, and assembly mechanisms of DOM in agricultural soils. This work provides the foundation for general principles explaining complex dynamics of DOM in natural ecosystems, highlighting that using theories and concepts in metacommunity ecology, such as community diversity and assembly mechanisms, may open a new avenue to understand DOM dynamics from a macro perspective.

Hydrolytic Behavior of Novel Pesticide Broflanilide and Its Dissipative Properties in Different Types of Soils.

All pesticides are toxic by nature and pose short- or long-term safety risks to human or the environment, especially when they were used extensively and absence of safety measures. As a new insecticidal active compound with a novel mechanism of action, there is a serious inadequate of information on the hydrolytic behavior of broflanilide in the aqueous environment, as well as its degradation pattern in agricultural soils. In particular, the effects of temperature and pH of the aqueous environment on its hydrolytic behaviors and the dissipation pattern in different types of agricultural soils were still in a dark box. And the further understanding and insights into this insecticidal active ingredient were being deeply conditioned by these doubts. The hydrolysis behavior of broflanilide and the dissipation pattern in soil were systematically investigated by constructing hydrolysis systems with different temperatures and pH values, and conducting spiking experiments in different types of agricultural soil in the laboratory. The obtained results showed that the longest hydrolysis half-life of 10mg/L broflanilide at 25°C was 43.32h (in pH 4.0 buffer), while it was only 12.84h in pH 9.0 buffer. In pH 7.0 buffer, the hydrolysis rate of broflanilide exhibited a significant temperature dependence, as shown by the fact that for every 10°C increase in the system temperature, the corresponding hydrolysis rate will increase about 1.5 times. The dissipation experiments in soils showed that broflanilide was most rapidly dissipated in fluvo-aquic soil (half-life of 1.94days), followed by lime concretion black soil (half-life of 2.53days) and cinnamon soil (half-life of 3.11days), and slower in paddy soil (half-life of 4.03days). It was indicated that broflanilide was a readily degradable pesticide in both aqueous environment and agricultural soil, and it was significantly affected by the temperature and pH of the system.

Simultaneous determination of the nematicide fluensulfone and its two major metabolites in soils by ultra-high performance liquid chromatography-tandem mass spectrometry

A fast and sensitive method for simultaneously detecting nonfumigant nematicide fluensulfone (FSF) and its two major metabolites [3,4,4-trifluorobut-3-ene-1-sulfonic acid (BSA) and 5‑chloro-1,3-thiazole-2-sulfonic acid (TSA)] in different types of agricultural soils (black soil, krasnozem, sierozem) was established and validated through ultra-high performance liquid chromatography-tandem mass spectrometry. The samples were prepared by a modified quick, easy, cheap, effective, rugged, and safe method. The soil samples were firstly extracted with acetonitrile/water (4/1) and then purified with multi-walled carbon nanotubes (MWCNTs). Parameters influencing purification efficiency and recoveries, such as the type and the amount of sorbent were evaluated and compared. The overall average recoveries of three target analytes in soils were in the range of 73.1%-113.9% and the relative standard deviations (including intra-day and inter-day precision) were less than 12.7%. The limit of quantification was 5 μg/kg for all three compounds. The established method was successfully applied to examine the degradation of FSF and the formation of its two major metabolites in three different types of soil, indicating its efficacy in investigating the environmental behavior of FSF in agricultural soil system

Sorption in soils and bioaccumulation potential of 2,2′-DiBBPA

2,2′-Dibromobisphenol A (2,2′-DiBBPA) is frequently detected in the environment. However, the mobility of 2,2′-DiBBPA in the soil environment is poorly understood. The present study examined the effects of soil components such as the NaClO-resistant fraction, dithionite-citrate-bicarbonate -demineralized fraction, humin fraction, black carbon, DOC-removed fraction, exogenous dissolved organic carbon and heavy metal cations on the adsorption of 2,2′-DiBBPA on several types of agricultural soils. The adsorption isotherms on soils and soil components were well fitted to the linear isotherm equation. 2,2′-DiBBPA sorption onto soils was dominated by soil organic matter content (SOM) and affected by exogenous dissolved organic carbon. Linear regression relationships between adsorption capacity (Kd) and soil characteristics were evaluated to predict partitioning of 2,2′-DiBBPA. Black carbon played a predominant role in the adsorption of 2,2′-DiBBPA. Heavy metal ions significantly inhibited the adsorptive behavior of 2,2′-DiBBPA under alkaline conditions. Semiempirical linear relationships were observed between biota-sediment accumulation factors (1.18–2.47)/logarithm of bioconcentration factors (BCFs, 2.49–2.52) of 2,2′-DiBBPA in lugworms and Kd. These results allow for the prediction of the bioaccumulation of 2,2′-DiBBPA in other soils. Furthermore, values of log BCF > 1.0 indicate the preferential bioaccumulation of 2,2′-DiBBPA in biota. These data are of significance for understanding the migration of 2,2′-DiBBPA in agricultural soils and bioaccumulation in organisms.

Home-based microbial solution to boost crop growth in low-fertility soil.

Soil microbial inoculants are expected to boost crop productivity under climate change and soil degradation. However, the efficiency of native vs commercialized microbial inoculants in soils with different fertility and impacts on resident microbial communities remain unclear. We investigated the differential plant growth responses to native synthetic microbial community (SynCom) and commercial plant growth-promoting rhizobacteria (PGPR). We quantified the microbial colonization and dynamic of niche structure to emphasize the home-field advantages for native microbial inoculants. A native SynCom of 21 bacterial strains, originating from three typical agricultural soils, conferred a special advantage in promotingmaize growth under low-fertility conditions. The root : shoot ratio of fresh weight increased by 78-121% with SynCom but only 23-86% with PGPRs. This phenotype correlated with the potential robust colonization of SynCom and positive interactions with the resident community. Niche breadth analysis revealed that SynCom inoculation induced a neutral disturbance to the niche structure. However, even PGPRs failed to colonize the natural soil, they decreased niche breadth and increased niche overlap by 59.2-62.4%, exacerbating competition. These results suggest that the home-field advantage of native microbes may serve as a basis for engineering crop microbiomes to support food production in widely distributed poor soils.

Soil adsorption and transport of lead in the presence of perovskite solar cell-derived organic cations

Perovskite photovoltaics offer a highly efficient and low-cost solar energy harvesting technology. However, the presence of lead (Pb) cations in photovoltaic halide perovskite (HaPs) materials is concerning, and quantifying the environmental hazard of accidental Pb2+ leaching into the soil is crucial for assessing the sustainability of this technology. Pb2+ from inorganic salts was previously found to remain in the upper soil layers due to adsorption. However, Pb-HaPs contain additional organic and inorganic cations, and competitive cation adsorption may affect Pb2+ retention in soils. Therefore, we measured, analyzed by simulations and report the depths to which Pb2+ from HaPs penetrates into 3 types of agricultural soil. Most of the HaP-leached Pb2+ is found to be retained already in the first cm of the soil columns, and subsequent rain events do not induce Pb2+ penetration below the first few cm of soil surface. Surprisingly, organic co-cations from the dissolved HaP are found to enhance the Pb2+ adsorption capacity in clay-rich soil, compared to non-HaP-based Pb2+ sources. Our results imply that installation over soil types with improved Pb2+ adsorption, and removal of only the contaminated topsoil, are sufficient means to prevent ground water contamination by HaP-leached Pb2+.

The effects of phosphate and pH on arsenate adsorption on allophanic Andosols in Miyazaki

ABSTRACT Arsenic (As) contamination in agricultural soils is a serious problem. The mobility and bioavailability of As in agricultural soil are mainly controlled by phosphate and pH. Although there is a potential risk of soil contamination in Japan by geogenic As distributed along the volcanic front, few studies have investigated arsenate adsorption on Andosols, a typical agricultural soil in Japan. In this study, we evaluated the effects of phosphate and pH on arsenate adsorption on allophanic Andosols. The adsorption isotherms of Andosols for arsenate and phosphate were determined in batch experiments at different phosphate concentrations and pH. In addition, following the competitive adsorption experiment of arsenate and phosphate, we determined three fractions of the adsorbed arsenate by sequential extraction as easily soluble As fraction (F1; 0.01 mol L−1 NaNO3 extraction), specifically adsorbed As and As mainly bound to poorly crystalline materials (F2; 0.2 mol L−1 NH4-oxalate buffer extraction), and As mainly bound to crystalline materials (F3; 0.2 mol L−1 NH4-oxalate buffer+0.1 mol L−1 ascorbic acid extraction). Andosols adsorbed~96.0% arsenate and~98.3% phosphate at the initial arsenate concentration of 214 µmol L−1 and phosphate concentration of 323 µmol L−1, respectively in each single-anion system. The maximum arsenate adsorption on the Andosols occurred at an equilibrium pH of~3.8 and it decreased with further increasing or decreasing equilibrium pH. Upon 300 µmol L−1 of arsenate addition, the Andosols adsorbed 98.6, 99.4, 91.0, and 65.8% of arsenate at an equilibrium pH of 3.0, 3.8, 6.2, and 7.6, respectively. The effect of pH was incorporated into the parameter of the modified Freundlich model for arsenate adsorption on Andosols. The competitive adsorption experiment results indicated a greater affinity of phosphate than arsenate for Andosols. Sequential extraction revealed that competition with phosphate not only decreased the amount of adsorbed arsenate, but also increased the amount of arsenate in F1, which is mobile and readily available to plants. Thus, phosphate fertilization can increase the mobility and bioavailability of arsenate in agricultural soils.

Effects of land use on the distribution of soil microplastics in the Lihe River watershed, China

Soil contamination by microplastics (MPs) has gained widespread attention, whose fate may be influenced by land use types. The effects of land use types and the intensity of human activities on the distribution and sources of soil MPs at the watershed scale are unclear. In this study, 62 surface soil sites in representing five land use types (urban, tea garden, dryland, paddy field and woodland) and 8 freshwater sediment sites were investigated in the Lihe River watershed. MPs were detected in all samples, and the average abundance of soil and sediments was 401.85 ± 214.02 and 222.13 ± 54.66 items/kg, respectively. The soil MPs abundance followed the sequence: urban > paddy field > dryland > tea garden > woodland. Soil MP distribution and MP communities were significant different (p < 0.05) among land use types. The similarity of MP community highly correlated with geographic distance, and woodlands and freshwater sediments may be a potential fate for MPs in the Lihe River watershed. Soil clay, pH, and bulk density significantly correlated with MP abundance and fragment shape (p < 0.05). The positive correlation between population density, Total- Point of Interest (POI) and MP diversity indicates the importance of intensity of human activities in exacerbating soil MP pollution (p < 0.001). Plastic waste sources accounted for 65.12%, 58.60%, 48.15% and 25.35% of MPs in urban, tea garden, dryland and paddy field soils, respectively. Differences in the intensity of agricultural activities and cropping patterns were associated with different percentages of mulching film sources in the three types of agricultural soils. This study provides new ideas for the quantitative analysis of soil MP sources in different land use types.

Natural soils in OECD 222 testing — influence of soil water and soil properties on earthworm reproduction toxicity of carbendazim

Soil sorption properties can influence the bioavailability of substances and consequently the toxicity for soil organisms. Current standardised laboratory testing for the exposure assessment of pesticides to soil organisms uses OECD artificial soil that does not reflect the high variation in chemical-physical soil properties found in natural agroecosystems. According to guideline OECD 222, earthworm reproduction tests with Eisenia fetida and the pesticide carbendazim were performed in four natural soils and OECD artificial soil. By using pF 1.6, which ensures a uniformity in actual soil water availability, the control reproduction performance of E. fetida in all natural soils was at the same level as OECD artificial soil. In a principle component analysis, the variation in toxicity between the tested soils was attributable to a combination of two soil properties, namely total organic carbon content (TOC) and pH. The largest difference of 4.9-fold was found between the typical agricultural Luvisol with 1.03% TOC and pH 6.2 (EC10: 0.17 (0.12–0.21) mg a.i. kg−1 sdw, EC50: 0.36 (0.31–0.40) mg a.i. kg−1 sdw) and OECD artificial soil with 4.11% TOC and pH 5.6 (EC10: 0.84 (0.72–0.92) mg a.i. kg−1 sdw, EC50: 1.07 (0.99–1.15) mg a.i. kg−1 sdw). The use of typical agricultural soils in standardised laboratory earthworm testing was successfully established with using the measure pF for soil moisture adjustment. It provides a more application-oriented approach and could serve as a new tool to refine the environmental risk assessment at lower tier testing or in an intermediate tier based approach.

Adsorption and degradation of neonicotinoid insecticides in agricultural soils.

The adsorption and degradation of seven commercially available neonicotinoid insecticides in four types of agricultural soils from three states (Mississippi, Arkansas, and Tennessee) in the USA were studied. The adsorptions of all the neonicotinoids fit a linear isotherm. The adsorption distribution coefficients (Kd) were found to be below 2.0 L/kg for all the neonicotinoids in all the soils from Mississippi and Arkansas. Only in the Tennessee soilsamples, the Kd ranged from 0.96 to 4.21 L/kg. These low values indicate a low affinity and high mobility of these insecticides in the soils. The soil organic carbon-water partitioning coefficient Koc ranged from 349 to 2569 L/kg. These Kd values showed strong positive correlations with organic carbon content of the soils. The calculated Gibbs energy change (ΔG) of these insecticides in all the soils ranged from - 14.6 to - 19.5kJ/mol, indicating that physical process was dominant in the adsorptions. The degradations of all these neonicotinoids in the soils followed a first-order kinetics with half-lives ranging from 33 to 305days. The order of the insecticides with decreasing degradation rate is as follows: clothianidin > thiamethoxam > imidacloprid > acetamiprid > dinotefuran > thiacloprid > nitenpyram. The moisture content, clay content, and cation exchange capacity showed positive effects on the degradation rate of all the neonicotinoids. The Groundwater Ubiquity Score (GUS) calculated from the adsorption distribution coefficient, organic content, and half-life indicates that, except for thiacloprid, all the neonicotinoids in all the soils are possible leachers, having potentials to permeate into and through groundwater zones.

Effects of irrigation on the fate of microplastics in typical agricultural soil and freshwater environments in the upper irrigation area of the Yellow River

Agricultural activities are among the most significant sources of microplastics (MPs) in water. However, few studies have explored the effect of irrigation on the fate of MPs in agricultural systems. This study investigated the distribution of MPs in agricultural soil, surface water, and sediment of adjacent rivers, as well as the “MP communities” in various environments before and after irrigation in a typical agricultural irrigation area of the Yellow River. MPs were detected in all of the examined sites. The number of MPs in surface water and sediment increased after irrigation, whereas those in the surface soil of croplands decreased. In the vertical direction, irrigation accelerated the migration of MPs (< 100 µm) deep into the soil. The vertical mobility of fibers in soil was faster than that of other types of MPs. Moreover, irrigation decreased the correlation between soil properties and MPs in soils. MP community analysis indicated that irrigation enhanced the differences between MP communities among adjacent environments. Collectively, our findings confirmed that river water irrigation caused secondary MP pollution in the soil environment and accelerated MP pollution in deep soil. Therefore, this study provides a theoretical basis for the development of strategies for MP pollution control in agricultural soil.

A wide foodomics approach coupled with metagenomics elucidates the environmental signature of potatoes

The term "terroir" has been widely employed to link differential geographic phenotypes with sensorial signatures of agricultural food products, influenced by agricultural practices, soil type, and climate. Nowadays, the geographical indications labeling has been developed to safeguard the quality of plant-derived food that is linked to a certain terroir and is generally considered as an indication of superior organoleptic properties. As the dynamics of agroecosystems are highly intricate, consisting of tangled networks of interactions between plants, microorganisms, and the surrounding environment, the recognition of the key molecular components of terroir fingerprinting remains a great challenge to protect both the origin and the safety of food commodities. Furthermore, the contribution of microbiome as a potential driver of the terroir signature has been underestimated. Herein, we present a first comprehensive view of the multi-omic landscape related to transcriptome, proteome, epigenome, and metagenome of the popular Protected Geographical Indication potatoes of Naxos.

Speciation of Zn and Cd in sierozem soil, northwest China: bulk EXAFS and micro synchrotron X-ray fluorescence.

Previous research studies have confirmed that Zn and Cd are the most predominant heavy metals in the Baiyin district, Gansu province, China. Furthermore, the speciation of Zn and Cd is a key factor in controlling the mobility, bioavailability, and toxicity of metals in Zn/Cd co-contaminated soil. In this study, the speciation of Zn and Cd in different types of agricultural soils including the Yellow River irrigated soil (s3) and sewage irrigated soil (s1 and s2) was investigated and compared by a combination of sequential extraction, bulk X-ray absorption fine structure (XAFS), and micro-X-ray fluorescence (μ-XRF) techniques. The results of the speciation quantified by XAFS were in general agreement with those obtained by sequential extraction, and the combination of both approaches allowed a reliable description of Zn/Cd speciation in soil. The speciation of Zn in the s1 soil exposed around the smelter was similar to speciation of Zn in the sewage irrigated s2 soil. In both soils, Zn was predominantly present as Zn-Al LDH (31-36%), Zn adsorbed on calcite (37-47%), and primary minerals (14-18% sphalerite and 9% franklinite). In contrast, the proportions of organic Zn (23%) and Zn-Al LDH (53%) were significantly higher in the Yellow River irrigated s3 soil, while that of Zn-calcite (24%) was lower. This indicated that Zn in s3 was less mobile and bioavailable than that in s1 and s2 soils. The content of bioavailable Zn in s3 was much lower than the background value and Zn did not pose a threat to the Yellow River irrigated soil. In addition, Cd was strongly correlated with Zn content and exhibited a simpler speciation. Cd adsorbed on illite and calcite was found as the major species in both soil types, posing higher migration and toxicity to the environment. Our study reported the speciation and correlation of Zn/Cd in sierozem soil for the first time and provided a significant theoretical basis for remediation actions to minimize Zn/Cd risks.

Syringic acid from rice roots inhibits soil nitrification and N2O emission under red and paddy soils but not a calcareous soil.

Syringic acid (SA) is a novel biological nitrification inhibitor (BNIs) discovered in rice root exudates with significant inhibition of Nitrosomonas strains. However, the inhibitory effect of SA on nitrification and nitrous oxide (N2O) emissions in different soils and the environmental factors controlling the degree of inhibition have not been studied. Using 14-day microcosm incubation, we investigated the effects of different concentrations of SA on nitrification activity, abundance of ammonia-oxidizing microorganisms, and N2O emissions in three typical agricultural soils. The nitrification inhibitory efficacy of SA was strongest in acidic red soil, followed by weakly acidic paddy soil, with no significant effect in an alkaline calcareous soil. Potential nitrification activity (PNA) were also greatly reduced by SA additions in paddy and red soil. Pearson correlation analysis showed that the inhibitory efficacy of SA might be negatively correlated with soil pH and positively correlated with clay percentage. SA treatments significantly reduced N2O emissions by 69.1-79.3% from paddy soil and by 40.8%-46.4% from red soil, respectively, but no effect was recorded in the calcareous soil. SA addition possessed dual inhibition of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) abundance in paddy and red soil. Structural equation modelling revealed that soil ammonium (NH4 +) and dissolved organic carbon content (DOC) were the key variables explaining AOA and AOB abundance and subsequent N2O emissions. Our results support the potential for the use of the BNI SA in mitigating N2O emissions and enhancing N utilization in red and paddy soils.

Degradation of Kresoxim-Methyl in Different Soils: Kinetics, Identification of Transformation Products, and Pathways Using High-Resolution-Mass-Spectrometry-Based Suspect and Non-Target Screening Approaches

This study investigated the degradation of strobilurin fungicide kresoxim-methyl (KM) in three typical agricultural soils from China by aerobic and anaerobic degradation experiments, focusing on degradation kinetics of KM, identification of transformation products (TPs), and prediction of toxicity end points via in silico approaches. KM showed a pronounced biphasic degradation in different soils and could rapidly degrade, with DT50 of <3 days. Four TPs were identified by high-resolution mass spectrometry (HRMS), and three of them have never been reported before. Possible degradation pathways of KM in soil were proposed, including hydrolysis, oxidation, and reduction, and the main mechanism involved in the biodegradation of KM was the hydrolysis of methyl ester regardless of aerobic or anaerobic conditions. The results of toxicity evaluation indicated that some TPs are more toxic than KM and may have a developmental toxicity and mutagenicity, and further risk assessment should be carried out.

Combination of3D Fluorescence/PARAFAC and UV-Vis Absorption for the Characterization of Agricultural Soils from Morocco.

The present study, combining UV-Visible absorption and 3D fluorescence supported by PARAFAC chemometric analysis, focused on the characterization of soil water extractable organic matter (WEOM) in the zone of Doukkala located near the Atlantic coast of Morocco. The extracts, in water, of a set of 30 samples covering the four main types of agricultural soils in the region (commonly labeled Tirs, Faid, Hamri and R'mel) were investigated. [Formula: see text] and [Formula: see text] absorbance ratios [Formula: see text] and [Formula: see text] spectral slopes, along with their ratios[Formula: see text], as well as the fluorescence [Formula: see text] and humification [Formula: see text] indices were calculated and interpreted. In the four soil types, these parameters revealed, on the one hand, organic materials of terrigenous origin with some biological component, and showed, on the other hand, that these materials are in similar stages of humification with an important humic character. In all the soils investigated, 3D fluorescence crossed with PARAFAC chemometrics highlighted the absence of any protein component and revealed the prevalence of the fulvic acids fraction in the organic matter humic material.

Statistical analysis of nitrogen use efficiency in Northeast China using multiple linear regression and Random Forest

Understanding the spatial-temporal dynamics of crop nitrogen (N) use efficiency (NUE) and the relationship with explanatory environmental variables can support land-use management and policymaking. Nevertheless, the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched. In this study, stepwise multiple linear regression (SMLR) and Random Forest (RF) were used to evaluate the spatial and temporal variation of NUE indicators (i.e., partial factor productivity of N (PFPN); partial nutrient balance of N (PNBN)) at county scale in Northeast China (Heilongjiang, Liaoning and Jilin provinces) from 1990 to 2015. Explanatory variables included agricultural management practices, topography, climate, economy, soil and crop types. Results revealed that the PFPN was higher in the northern parts and lower in the center of the Northeast China and PNBN increased from southern to northern parts during the 1990–2015 period. The NUE indicators decreased with time in most counties during the study period. The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFPN, and 0.67 and 0.89 for PNBN, respectively. The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model. The planting area index of vegetables and beans, soil clay content, saturated water content, enhanced vegetation index in November & December, soil bulk density, and annual minimum temperature were the main explanatory variables for both NUE indicators. This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR. This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development, ensuring food security, alleviating environmental degradation and increasing farmer's profitability.

Polyester microplastic fibers affect soil physical properties and erosion as a function of soil type

Abstract. Microplastics are recognized as a factor of global change contaminating many environmental compartments. Agricultural soils are very likely to receive microplastic contamination and are of particular concern due to their role in food production. Microplastic fibers have already been shown to be able to affect soil properties, but their effect on different soil types is poorly understood. Moreover, limited information is available on how the presence of this pollutant can affect soil water erosion processes, which are extremely important issues in many environments. In the light of this, we performed two experiments (carried out on a microscale) to investigate how the presence of polyester microplastic fibers affects soil physical and hydrological parameters and processes such as aggregate formation and soil erosion in three different agricultural soil types (a Vertisol, an Entisol, and an Alfisol). Our data show that the effects of polyester microplastic fibers on soil physical parameters and erosion are strongly dependent on soil type. We found that microplastic fiber contamination can affect soil bulk density, capacitive indicators of soil physical quality, and decrease the formation of new aggregates (labile in the incubation period applied in our experiments) but did not affect their stability in water. However, we found that polyester microplastic fibers reduced soil loss and sediment concentration, especially in the most erodible soils. In this paper, we provide some hypotheses, but certainly future data are still needed to confirm or disprove our hypotheses. Overall, our results highlight the importance of broadly exploring soil properties, such as texture, mineralogy, organic carbon content, etc., to better understand how the various soil types respond to microplastic fiber contamination.