Proximal sensing provides clean, fast, and accurate quality control of organic and mineral fertilizers

Farms use large quantities of fertilizers from many sources, making quality control a challenging task, as the traditional wet-chemistry analyses are expensive, time consuming and not environmentally-friendly. As an alternative, this work proposes the use of portable X-ray fluorescence (pXRF) spectrometry and machine learning algorithms for rapid and low-cost estimation of macro and micronutrient contents in mineral and organic fertilizers. Four machine learning algorithms were tested. Whole (i.e., as delivered by the manufacturer) (CP) and ground (AQ) samples (429 in total) were analyzed to test the effect of fertilizer granulometry in prediction performance. Model validation indicated highly accurate predictions of macro (N: R2 = 0.92; P: 0.97; K: 0.99; Ca: 0.94, Mg: 0.98; S: 0.96) and micronutrients (B: 0.99; Cu: 0.99; Fe: 0.98; Mn: 0.91; Zn: 0.94) for both organic and mineral fertilizers. RPD values ranged from 2.31 to 9.23 for AQ samples, and Random Forest and Cubist Regression were the algorithms with the best performances. Even samples analyzed as they were received from the manufacturer (i.e., no grinding) provided accurate predictions, which accelerate the confirmation of nutrient contents contained in fertilizers. Results demonstrated the potential of pXRF data coupled with machine learning algorithms to assess nutrient composition in both mineral and organic fertilizers with high accuracy, allowing for clean, fast and accurate quality control. Sensor-driven quality assessment of fertilizers improves soil and plant health, crop management efficiency and food security with a reduced environmental footprint.

Trends in soil organic matter and topsoil thickness under regenerative practices at the University of Washington student farm

Conventional methods of agriculture, especially tillage, are often accompanied by soil degradation in the form of erosion and organic matter depletion. Regenerative agricultural methods seek to repair soil ecosystems by building topsoil and soil organic matter (SOM), decreasing reliance on chemical fertilizers and increasing both water retention capacity and the diversity and quantity of soil microbial and fungal communities. The University of Washington (UW) student farm is an organic and regeneratively managed site on the UW Seattle campus. Over the past 20 years the farm gradually expanded so locations on the farm encompass both unimproved topsoil and soils managed regeneratively for periods of 5 to 20 years. This arrangement allows a time-trend analysis of soil development under regenerative methods. Measurements of topsoil thickness (defined as the distance from the ground surface to the base of the soil A horizon) and organic matter content were collected across 14 distinct plots on the farm to quantify trends over time and estimate net change in SOM (and soil organic carbon, or SOC). While SOM content weakly increased by 0.5% per year, topsoil thickness exhibited a significant linear increase of 0.86 cm per year. Over a twenty-year period under the management practices of the UW Farm total organic carbon storage in soils, determined using topsoil thickness, density, and SOC content, increased by between 4 and 14 t ha-1 yr-1. The general increases in topsoil thickness, SOM content, and total soil carbon demonstrate the potential of soil-health-focused practices to help maintain a productive and efficient urban growing space.

Integration of biochar with nitrogen in acidic soil: A strategy to sequester carbon and improve the yield of stevia via altering soil properties and nutrient recycling

The health of agroecosystems is subsiding unremittingly, and the over-use of chemical fertilizers is one of the key reasons. It is hypothesized that integrating biochar, a carbon (C)-rich product, would be an effective approach to reducing the uses of synthetic fertilizers and securing crop productivity through improving soil properties and nutrient cycling. The bamboo biochar at different quantities (4-12 Mg ha-1) and combinations with chemical fertilizers were tested in stevia (Stevia rebaudiana) farming in silty clay acidic soil. The integration of biochar at 8 Mg ha-1 with 100% nitrogen (N), phosphorus (P), and potassium (K) produced statistically (p ≤ 0.05) higher leaf area index, dry leaf yield, and steviol glycosides yield by about 18.0-33.0, 25.8-44.9, and 20.5-59.4%, respectively, compared with the 100% NPK via improving soil physicochemical properties. Soil bulk density was reduced by 5-8% with biochar at ≥ 8 Mg ha-1, indicating the soil porosity was increased by altering the soil macrostructure. The soil pH was significantly (p ≤ 0.05) augmented with the addition of biochar alone or in the combination of N because of the alkaline nature of the used biochar (pH = 9.65). Furthermore, integrating biochar at 8 Mg ha-1 with 100% NPK increased 22.7% soil organic C compared with the sole 100% NPK. The priming effect of applied N activates soil microorganisms to mineralize the stable C. Our results satisfy the hypothesis that adding bamboo biochar would be a novel strategy for sustaining productivity by altering soil physicochemical properties.

Towards a farmer-feasible soil health assessment that is globally applicable

Globally, agriculture has had a significant and often detrimental impact on soil. The continued capacity of soil to function as a living ecosystem that sustains microbes, plants, and animals (including humans), its metaphorical health, is of vital importance across geographic scales. Healthy soil underpins food production and ecosystem resilience against a changing climate. This paper focuses on assessing soil health, an area of increasing interest for farming communities, researchers, industry and policy-makers. Without accessible and reliable soil assessment, any management and interventions to improve soil health are likely to be sub-optimal. Here we explore available soil health assessments (SHAs) that may be feasible for farmers of varying income levels and suitable for broad geographic application. Whilst there is a range of existing approaches to SHA, we find that no one framework currently meets these broad aims. Firstly, reliance on expensive and logistically complex laboratory methods reduces viability and accessibility for many farmers. Secondly, lack of defined indicator baselines and associated thresholds or gradients for soil health prevents the assessment of soil measurements against achieving optima for a given set of local soil-climate conditions. Since soils vary greatly, these baselines and thresholds must be defined considering the local biogeographic context; it is inappropriate to simply transfer calibrated information between contexts. These shortcomings demand progress towards a feasible, globally applicable and context-relevant SHA framework. The most feasible SHAs we identified were developed locally in conjunction with farmers, who have been repeatedly found to assess the health of their soils accurately, often using relatively simple, observable indications. To progress, we propose assessment of which indicators add information to a SHA in local contexts, with a focus on sufficiency, to reduce data burden. Provision of a standardised protocol for measurement and sampling that considers the reliability and accuracy of different methods would also be extremely valuable. For greatest impact, future work should be taken forward through a cross-industry collaborative approach involving researchers, businesses, policy makers, and, above all, farmers, who are both experts and users.

Kadam P, Siddiqui MH, Gaafar ARZ, Atikur Rahman M. Conservation tillage and fertiliser management strategies impact on basmati rice (Oryza sativa L): crop performance, crop water productivity, nutrient uptake and fertility status of the soil under rice-wheat cropping system

Background

The sustainability of paddy production systems in South Asia has recently been affected by a decline in soil health and excessive water usage. As a response to the global energy crisis, escalating costs of synthetic fertilisers, and growing environmental concerns, the utilization of organic plant-nutrient sources has gained considerable attention. Emerging adaptation technologies, including conservation tillage and innovative approaches to fertilizer management, present practical choices that can significantly contribute to the long-term preservation of soil fertility.

Methods

The two year-long field experiment was completed in sandy loam soil during rainy (Kharif) seasons in 2019 and 2020 at the crop research centre farm of Sardar Vallabhbhai Patel University of Agricultural & Technology, Meerut, Uttar Pradesh to analyze the impacts of different tillage establishment of the crop and its methodologies as well as integrated nutritional management approaches on rice growth, yield, productivity of water, nutrient uptake, and fertility status of soil under a rice-wheat rotation system. The experiment was set up in a factorial randomized block design and replicated three times in a semi-arid subtropical environment.

Results

The conventionally transplanted rice puddled (CT-TPR) grew substantially better taller plants, and higher dry matter buildup leads to increased yields than transplanted rice under raised wide bed (WBed-TPR). WBed-TPR plots had more tillers, LAI, CGR, RGR, and yield characteristics of the rice in two year study. CT-TPR increased grain yield by 4.39 and 4.03% over WBed-TPR in 2019 and 2020, while WBed-TPR produced the highest water productivity (0.44 kg m-3) than CT-TPR, respectively. The 100% RDF+ ZnSO4 25 kg ha-1 + FYM (5 t ha-1) + PSB (5 kg ha-1) + Azotobacter 20 kg ha-1 (N6) treatment outperformed the other fertiliser management practices in terms of crop growth parameters, yields of grain (4,903 and 5,018 kg ha-1), nutrient uptake and NPK availability, organic soil carbon. Among the fertilizer management practices, with the direct applications of the recommended dose of fertilizer (RDF), farm yard manure (FYM), phosphate solubilizing bacteria (PSB), Azatobactor and zinc worked synergistically and increased grain yields by 53.4, 51.3, 47.9 and 46.2% over their respective control treatment.

Conclusions

To enhance rice productivity and promote soil health, the study suggests that adopting conservation tillage-based establishment practices and implementing effective fertilizer management techniques could serve as practical alternatives. It is concluded that the rice yield was improved by the inclusive use of inorganic fertiliser and organic manure (FYM). Additionally, the study observed that the combination of conventional puddled transplanted rice (CT-TPR) and N6 nitrogen application resulted in enhanced rice crop productivity and improved soil health.

Effects of microplastics exposure on soil inorganic nitrogen: A comprehensive synthesis

Microplastics, a growing environmental concern, impact soil inorganic nitrogen (N) transformation, specifically affecting water-extractable nitrate N (NO3--N) and ammonium N (NH4+-N). However, inconsistencies among relevant findings necessitate a systematic analysis. Accordingly, the present meta-analysis addresses these discrepancies by evaluating the effects of microplastics on soil inorganic N and identifying key influencing factors. Our meta-analysis of 216 paired observations from 47 studies demonstrates microplastics exposure causes an overall significant reduction of 7.89% in soil NO3--N concentration, but has no significant impact on NH4+-N concentration. Subgroup analysis further revealed effects of microplastics on soil inorganic N were modulated by microplastics characteristics, experimental conditions (exposure time, experimental temperature, plant effects), and soil properties (soil texture, initial soil pH, initial soil organic carbon, soil total N concentration). We found that microplastics exposure above 27 ℃ enhances soil NO3--N concentration, a finding linked to specific soil properties and conditions, underscoring the impacts of global warming. Importantly, the microplastics polymer type was the most influential predictor of effects on soil NO3--N concentration, while soil NH4+-N concentration was primarily affected by soil texture and microplastics type. These findings illuminate the complex effects of microplastics on soil inorganic N, informing soil management amid increasing microplastics pollution.

Linking above and belowground carbon sequestration, soil organic matter properties, and soil health in Brazilian Atlantic Forest restoration

Forest restoration mitigates climate change by removing CO2 and storing C in terrestrial ecosystems. However, incomplete information on C storage in restored tropical forests often fails to capture the ecosystem's holistic C dynamics. This study provides an integrated assessment of C storage in above to belowground subsystems, its consequences for greenhouse gas (GHG) fluxes, and the quantity, quality, and origin of soil organic matter (SOM) in restored Atlantic forests in Brazil. Relations between SOM properties and soil health indicators were also explored. We examined two restorations using tree planting ('active restoration'): an 8-year-old forest with green manure and native trees planted in two rounds, and a 15-year-old forest with native-planted trees in one round without green manure. Restorations were compared to reformed pasture and primary forest sites. We measured C storage in soil layers (0-10, 10-20, and 20-30 cm), litter, and plants. GHG emissions were assessed using CH4 and CO2 fluxes. SOM quantity was evaluated using C and N, quality using humification index (HLIFS), and origin using δ13C and δ15N. Nine soil health indicators were interrelated with SOM attributes. The primary forest presented the highest C stocks (107.7 Mg C ha-1), followed by 15- and 8-year-old restorations and pasture with 69.8, 55.5, and 41.8 Mg C ha-1, respectively. Soil C stocks from restorations and pasture were 20% lower than primary forest. However, 8- and 15-year-old restorations stored 12.3 and 28.3 Mg ha-1 more aboveground C than pasture. The younger forest had δ13C and δ15N values of 2.1 and 1.7‰, respectively, lower than the 15-year-old forest, indicating more C derived from C3 plants and biological N fixation. Both restorations and pasture had at least 34% higher HLIFS in deeper soil layers (10-30 cm) than primary forest, indicating a lack of labile SOM. Native and 15-year-old forests exhibited higher soil methane influx (141.1 and 61.9 μg m-2 h-1). Forests outperformed pasture in most soil health indicators, with 69% of their variance explained by SOM properties. However, SOM quantity and quality regeneration in both restorations approached the pristine forest state only in the top 10 cm layer, while deeper soil retained agricultural degradation legacies. In conclusion, active restoration of the Atlantic Forest is a superior approach compared to pasture reform for GHG mitigation. Nonetheless, the development of restoration techniques to facilitate labile C input into deeper soil layers (>10 cm) is needed to further improve soil multifunctionality and long-term C storage.

An innovative risk evaluation method on soil pathogens in urban-rural ecosystem

The presence and reproduction of pathogens in soil environment have significant negative impacts on soil security and human health in urban-rural ecosystem. Rapid urbanization has dramatically changed the land use, soil ecosystems, and the presence of pathogens in soil environment, however, the risk associated with soil pathogens remains unknown. Identifying the potential risk of pathogens in soils in urban-rural ecosystem has become an urgent issue. In this study, we established a risk evaluation method for soil pathogens based on analytic hierarchy process and entropy methods to quantitatively estimate the potential risk of soil pathogens to children and adults in urban-rural ecosystem. The abundance and species number of soil pathogens, network structure of soil microbial community, and human exposure factors were considered with 12 indicators to establish the risk evaluation system. The results revealed that 19 potential pathogenic bacteria were detected in soils within a typical urban-rural ecosystem. Substantial differences were observed in both abundance and species of soil pathogens as well as network structure of soil microbial community from urban to rural areas. Urban areas exhibited relatively lower levels of soil pathogenic abundance, but the microbial network was considerably unstable. Rural areas supported relatively higher levels of soil pathogenic abundance and stable microbial networks. Notably, peri-urban areas showed relatively unstable microbial networks alongside higher levels of soil pathogenic abundance compared to other areas. The risk evaluation of soil pathogens for both adults and children showed that peri-urban areas presented the highest potential risk, with children being more susceptible than adults to threats posed by soil pathogens in both urban and peri-urban areas. The established evaluation system provides an innovative approach for quantifying risk of soil pathogens at regional scale and can be used as a reference for preventing soil pathogens contamination and enhancing soil health in areas with intense human activities.

Alternative ground covers and strip-tilling in CBD hemp production

OBJECTIVE

Little research has been done on managing soil health for large-scale, outdoor hemp production, contributing to the possible overuse of black plastic for weed suppression. Our experiment aimed to understand the performance of alternative ground covers including forage crops and hay as well as a less disruptive tilling method called strip-tilling compared to black plastic.

RESULTS

Yield and soil health data were taken from three experimental plantings from two different outdoor CBD hemp farms in Vermont, USA. We find that hay may be a competitive alternative to black plastic in terms of producing heavier plants. Our research also found that clover seed and hay are both more cost-effective options than black plastic which may sway some farmers to adopt these alternative ground cover options.

Hybrid Whale Archimedes Optimization-based MLPNN model for soil nutrient classification and pH prediction

Soil fertility and environmental factors play an important role in improving productivity and cropland quality in the agricultural sector. A new prediction and classification model for the potential of soil nutrients and hydrogen (pH) levels is proposed. The proposed model, Hybrid Whale Archimedes Optimization-based Multilayer Perceptron Neural Network (HWAO-MLPNN), is utilized for soil features classification of pH levels, and the soils are collected from the villages such as phosphorous (P), organic carbon (OC), boron (B), and potassium (K). The village-wise soil fertility prediction and classification model aims to improve soil health, reduce harmful fertilizer usage, enhance environmental quality, and achieve more profits. The proposed model combines the Multilayer Perceptron Neural Network (MLPNN) model and the Hybrid Whale Archimedes Optimization (HWAO) algorithm to enhance the classification performance on the validation data. The Marathwada dataset is selected to validate the soil nutrient prediction and classification model, and various measuring units such as cross-validation accuracy, Area Under Curve (AUC), accuracy, Mean Squared Error (MSE), G-mean, precision, specificity, and sensitivity are used for evaluation. The comparative study of this paper shows that the proposed HWAO-MLPNN achieved more classification accuracy of 98.1%, cross-validation accuracy of 98.3% for pH classification, and cross-validation accuracy of 97.9% for soil nutrient classification. The proposed model can be utilized to accurately classify soil nutrients and pH levels, which can have a significant impact on improving soil health, reducing harmful fertilizer usage, enhancing environmental quality, and ultimately increasing profitability in the agricultural sector.

Global rainfall erosivity database (GloREDa) and monthly R-factor data at 1 km spatial resolution

Here, we present and release the Global Rainfall Erosivity Database (GloREDa), a multi-source platform containing rainfall erosivity values for almost 4000 stations globally. The database was compiled through a global collaboration between a network of researchers, meteorological services and environmental organisations from 65 countries. GloREDa is the first open access database of rainfall erosivity (R-factor) based on hourly and sub-hourly rainfall records at a global scale. This database is now stored and accessible for download in the long-term European Soil Data Centre (ESDAC) repository of the European Commission's Joint Research Centre. This will ensure the further development of the database with insertions of new records, maintenance of the data and provision of a helpdesk. In addition to the annual erosivity data, this release also includes the mean monthly erosivity data for 94% of the GloREDa stations. Based on these mean monthly R-factor values, we predict the global monthly erosivity datasets at 1 km resolution using the ensemble machine learning approach (ML) as implemented in the mlr package for R. The produced monthly raster data (GeoTIFF format) may be useful for soil erosion prediction modelling, sediment distribution analysis, climate change predictions, flood, and natural disaster assessments and can be valuable inputs for Land and Earth Systems modelling.

Will the aging products of soil-reinforcement fibers stress plant growth and soil health?

Soil-reinforcement fibers are widely used for soil remediation and erosion prevention in ecologically vulnerable regions with sparse vegetation coverage and are incorporated into the soil for prolonged periods. However, the potential risks posed by aging fiber materials to soil health and plant growth have been largely neglected. This study explored the effects of aging solutions for polyethylene terephthalate (PET), coir, and carbon fibers on the physiological characteristics and vegetation coverage of ryegrass, as well as soil properties. Results indicated that PET and carbon fibers decreased ryegrass density and inhibited chlorophyll synthesis. All three fiber aging solutions aggravated leaf peroxidation, as represented by a sharp increase in the malondialdehyde (MDA) content. Leaf peroxidase activities improved, whereas the ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities under the carbon fiber treatment were significantly lower than those under the PET and coir fiber treatments. The three fiber aging solutions significantly reduced soil H2O2 activity, improved soil leucine aminopeptidase (LAP) activity. Besides, coir fiber aging solution improved soil hemicellulose (CB) activity significantly. Aging solutions of PET and coir fibers increased the number of soil bacterial colonies, while the carbon fiber aging solution increased the number of soil actinomyces colonies. Overall, our findings demonstrate that fiber aging solutions decrease plant density, cause leaf damage, and alter soil characteristics in the short term. However, these solutions have minimal impact on soil health. The coir fiber aging solution has minimal effects on plant growth and soil properties, and is still a viable alternative to traditional non-degradable soil-reinforcing fibers.

Biochar as a carbonaceous material to enhance soil quality in drylands ecosystems: A review

Drylands are fragile environments that should be carefully managed to improve their quality and functions to achieve sustainable development. Their major problems involve low availability of nutrients and soil organic carbon content. Biochar effect on soil is a joint response of micro to nano sized biochar and soil characteristics. In this review, we attempt to carry out a critical analysis of biochar application to enhance dryland soil quality. Correlating the effects identified from its soil application, we explored the subjects that remains open in the literature. The relation of composition-structure-properties of biochar vary among pyrolysis parameters and biomass sources. Limitations in soil physical quality in drylands, such as low water-holding capacity, can be alleviated by applying biochar at a rate of 10 Mg ha-1 also resulting in beneficial effects on soil aggregation, improved soil porosity, and reduced bulk density. Biochar addition can contribute to the rehabilitation of saline soils, by releasing cations able to displaces sodium in the exchange complex. However, the recovery process of salt-affected soils might be accelerated by the association of biochar with another soil conditioners. This is a promising strategy especially considering the biochar alkalinity and variability in nutrients bioavailability to improve soil fertilization. Further, while higher biochar application rate (>20 Mg ha-1) might change soil C dynamics, a combination of biochar and nitrogen fertilizer can increase microbial biomass carbon in dryland systems. Other aspect of biochar soil application is the economic viability of scale-up production, which is mainly associate to pyrolysis process being biochar production the costliest stage. Nevertheless, the supplying of feedstock might also represent a great input on biochar final costs. Therefore, biochar-based technology is a big opportunity to improve fragile environments such as drylands, integrating sustainable technologies with regional development. Considering the specificity of application area, it might be a model of sustainable agricultural practices protecting the environment in a bioeconomic perspective.

Dynamic response of microbial communities to thermally remediated oil-bearing drilling waste in wheat soil

The primary objective of our study was to mix thermally remediated oil-bearing drilling waste (TRODW) with farmland soil during wheat planting and explore the response of microbial phospholipid fatty acid (PLFA) communities as well as the feasibility of returning TRODW to farmland. Based on environmental protection requirements and the dynamic response of wheat soil, this paper not only provides a method combining multiple models for mutual verification but also provides valuable and exploratory information for the remediation and reuse of oily solid waste. Our research found that salt damage mainly originated from sodium ions and chloride ions that inhibited the development of microbial PLFA communities in the treated soils at the initial stage. When salt damage declined, TRODW improved the levels of phosphorus, potassium, hydrolysable nitrogen and soil moisture, increasing the soil health status and promoting the development of microbial PLFA communities even when the addition ratio reached 10%. Moreover, the influences of petroleum hydrocarbons and heavy metal ions on microbial PLFA community development were not significant. Therefore, when salt damage is controlled effectively and the oil content in TRODW is no more than 3‰, it is potentially feasible to return TRODW to farmland.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review)

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

Lignite bioorganic fertilizer enhanced microbial co-occurrence network stability and plant-microbe interactions in saline-sodic soil

Lignite-converted bioorganic fertilizer substantially improves soil physiochemical properties, but little is known about how lignite bioorganic fertilizer (LBF) affects soil microbial communities and how the changed microbial communities impact their stability, functions, and crop growth in saline-sodic soil. Therefore, a two-year field experiment was conducted in saline-sodic soil in the upper Yellow River basin, Northwest China. Three treatments, i.e., the control treatment without organic fertilizer (CK), the farmyard manure treatment (FYM) amended with 21 t ha^-1 (same as local farmers) sheep manure, and the LBF treatment amended with the optimal rate of LBF (3.0 and 4.5 t ha^-1), were designed in this study. The results showed that after two years of application of LBF and FYM, the percentage of aggregate destruction (PAD) was significantly reduced by 14.4 % and 9.4 %, respectively, while the saturated hydraulic conductivity (K_s) was obviously increased by 114.4 % and 99.7 %, respectively. The LBF treatment significantly increased the contributions of nestedness to total dissimilarity by 101.4 % and 156.2 % in bacterial and fungal communities, respectively. LBF contributed to the shift from stochasticity to variable selection in the assembly of the fungal community. The LBF treatment enriched the bacterial classes of Gammaproteobacteria, Gemmatimonadetes, and Methylomirabilia and fungal classes of Glomeromycetes and GS13, which were mainly driven by PAD and K_s. Additionally, the LBF treatment significantly increased the robustness and positive cohesions and decreased the vulnerability of the bacterial co-occurrence networks in both 2019 and 2020 in comparison with the CK treatment, indicating that the LBF treatment increased stability of bacterial community. The relative abundance of chemoheterotrophy and arbuscular mycorrhizae in the LBF treatment were 89.6 % and 854.4 % higher than those in the CK treatment, respectively, showing that the LBF enhanced sunflower-microbe interactions. The FYM treatment improved the functions mainly regarding sulfur respiration and hydrocarbon degradation by 309.7 % and 212.8 % in comparison with the CK treatment, respectively. The core rhizomicrobiomes in the LBF treatment showed strong positive connections with the stabilities of both bacterial and fungal co-occurrence networks, as well as the relative abundance and potential functions of chemoheterotrophy and arbuscular mycorrhizae. These factors were also linked to the growth of sunflowers. This study reveals that the LBF improved sunflower growth due to enhance microbial community stability and sunflower-microbe interactions through altering core rhizomicrobiomes in saline-sodic farmland.

Biochar addition increased soil bacterial diversity and richness: Large-scale evidence of field experiments

Biochar plays a crucial role in enhancing soil ecological functions and productivity, and mitigating environmental pollution. Despite the available studies conducted through high-throughput sequencing to understand the effects of biochar on soil bacterial diversity and richness, a comprehensive understanding remains elusive. Our global meta-analysis addresses this knowledge gap, incorporating 473 pairs of observations from 84 studies to assess soil bacterial diversity and richness response to biochar addition. We found that biochar application increased bacterial Shannon and Chao1 indices by 0.99 % and 6.45 % respectively. However, these positive effects were context-dependent, especially concerning bacterial diversity. Through aggregated boosted trees analysis, we determined that soil characteristics (including soil organic carbon and nitrogen contents, soil pH, and soil texture) had a more significant influence than biochar properties, experimental conditions, or climatic factors on soil bacterial diversity and richness post biochar addition. In particular, the soil carbon to nitrogen ratio stood out as the leading factor influencing the bacterial Shannon and Chao1 indices following biochar addition. Our findings offer new insights into biochar's influence on soil bacterial activity, taking into account biochar-mediated spatiotemporal variation. This information is pivotal for optimizing biochar characteristics and application to improve soil biological health.

Heavy metal effects on multitrophic level microbial communities and insights for ecological restoration of an abandoned electroplating factory site

The response of soil microbes to heavy metal pollution provides a metric to evaluate the soil health and ecological risks associated with heavy metal contamination. However, a multitrophic level perspective of how soil microbial communities and their functions respond to long-term exposure of multiple heavy metals remains unclear. Herein, we examined variations in soil microbial (including protists and bacteria) diversity, functional guilds and interactions along a pronounced metal pollution gradient in a field surrounding an abandoned electroplating factory. Given the stressful soil environment resulting from extremely high heavy metal concentrations and low nutrients, beta diversity of protist increased, but that of bacteria decreased, at high versus low pollution sites. Additionally, the bacteria community showed low functional diversity and redundancy at the highly polluted sites. We further identified indicative genus and "generalists" in response to heavy metal pollution. Predatory protists in Cercozoa were the most sensitive protist taxa with respect to heavy metal pollution, whereas photosynthetic protists showed a tolerance for metal pollution and nutrient deficiency. The complexity of ecological networks increased, but the communication among the modules disappeared with increasing metal pollution levels. Subnetworks of tolerant bacteria displaying functional versatility (Blastococcus, Agromyces and Opitutus) and photosynthetic protists (microalgae) became more complex with increasing metal pollution levels, indicating their potential for use in bioremediation and restoration of abandoned industrial sites contaminated by heavy metals.

Changes in the health of metal-contaminated soil before and after stabilization and solidification

Stabilization is popularly employed to remediate metal-contaminated soils. It involves the absorption and precipitation of heavy metals to reduce their solubility, movement characteristics, or risk and toxicity. This study aimed to conduct a soil health assessment to determine changes in the health of metal-contaminated soil before and after the application of five stabilizers (acid mine drainage sludge (AMDS), coal mine drainage sludge (CMDS), steel slag, lime, and cement). Soil health assessment, including three soil functions, namely soil productivity, soil stability, and soil biodiversity, evaluated the physical, chemical, and biological indicators (total 16 indicators). Soil health index (SHI) of soil function was calculated by multiplying each indicator score by the weighting factor of each indicator. Total SHI was obtained by summing the three soil-function SHI. Total SHI of the stabilized and test soils followed the order as control soil (1.90) > heavy metal-contaminated soil (1.55) > CMDS-stabilized soil (1.29) > steel slag-stabilized soil (1.29) > AMDS-stabilized soil (1.26) > cement-stabilized soil (0.74) > lime-stabilized soil (0.67). Total SHI of the initial heavy metal-contaminated soil was evaluated as 'normal', before the stabilizer was applied; however, most of the stabilized soils became 'bad' after application of the stabilizers. Furthermore, soils stabilized by cement and lime showed very poor soil health. The results implied that changes in physical and chemical soil properties occurred due to the disturbance caused by the mixing of stabilizers, and ions eluted from the stabilizers could deteriorate soil health further. The findings indicated that soil treated with stabilizers is not suitable for agricultural purposes. Overall, the study suggested that stabilized soil from metal-contaminated sites should be covered with clean soil or monitored for some time before deciding its future agricultural use.

The role of land use, management, and microbial diversity depletion on glyphosate biodegradation in tropical soils

Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10^-1) and thousandfold (D3 = 10^-3) dilutions] impacted soil enzyme activities (β-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher β-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.

The Social Factors Influencing Cover Crop Adoption in the Midwest: A Controlled Comparison

Increased funding and resources have become available in recent years for agricultural producers to plant cover crops to improve soil health and prevent nutrient loss and erosion; however, cover crop adoption remains relatively low and has been uneven across different Midwestern counties. This study employed a controlled comparison method to investigate the social factors affecting cover crop adoption in Iowa, Illinois, and Indiana. In each state, the authors compared pairs of neighboring counties, where one county was a relatively higher adopter and the other was a lower adopter of cover crops, while controlling for variations in climate conditions. Results show that there were multiple factors explaining the difference in cover crop adoption among county pairs. Social factors included attitudes toward cover crops; conservation agency influence; presence of cover crop experts, advocates, and/or entrepreneurs; and collaboration between agencies and the private sector. Other important factors included topography, cattle raising, organic production, and local incentive-based programs. Among these, collaborations between agencies and the private sector played the most important role in explaining why some counties had higher rates of cover crop adoption compared to their neighbors.

Cropping System Diversification Influences Soil Microbial Diversity in Subtropical Dryland Farming Systems

Conventional dryland cropping systems are characterised by low crop diversity and frequent fallows. This has significant impacts on soil microbes that underpin soil function. Diversifying crop rotations can potentially counter these effects; however, limited data exists on the impacts of diversified crop rotations on soil microbes in drylands. Using phylogenetic marker gene sequencing, we characterised soil microbial diversity in conventional and diversified dryland crop rotations in subtropical Australia. This included winter and summer dominant rotations. Conventional systems were cereal-dominant with a crop-fallow rotation. Diversified systems included greater crop diversity, double crops, cover crops, and a multi-year ley pasture. In summer rotations with increased crop diversity and cover crops, bacterial and fungal richness increased, and distinct communities were formed compared to fallow land. Often, these community shifts were associated with greater soil organic carbon (SOC) and nitrogen. All winter rotations had distinct fungal communities and ley pasture resulted in greater fungal diversity compared to other rotations. No effects of the winter rotations were evident on bacterial communities. Our results show that diversification of dryland crop rotations leads to significant shifts in soil microbial communities in both winter and summer cropping systems. Both summer and winter rotations incorporating cover crops and ley pasture had greater soil respiration and nitrogen, indicating increases in soil fertility. These rotations may offer an alternative to conventional crop-fallow rotations to counter ongoing declines in soil health.

Digital mapping of the soil available water capacity: tool for the resilience of agricultural systems to climate change

Soil available water capacity (AWC) is a key function for human survival and well-being. However, its direct measurement is laborious and spatial interpretation is complex. Digital soil mapping (DSM) techniques emerge as an alternative to spatial modeling of soil properties. DSM techniques commonly apply machine learning (ML) models, with a high level of complexity. In this context, we aimed to perform a digital mapping of soil AWC and interpret the results of the Random Forest (RF) algorithm and, in a case study, to show that digital AWC maps can support agricultural planning in response to the local effects of climate change. To do so, we divided this research into two approaches: In the first approach, we showed a DSM using 1857 sample points in a southeastern region of Brazil with laboratory-determined soil attributes, together with a pedotransfer function (PTF), remote sensing and DSM techniques. In the second approach, the constructed AWC digital soil map and weather station data were used to calculate climatological soil water balances for the periods between 1917-1946 and 1991-2020. The result showed the selection of covariates using Shapley values as a criterion contributed to the parsimony of the model, obtaining goodness-of-fit metrics of R² 0.72, RMSE 16.72 mm m^-1, CCC 0.83, and Bias of 0.53 over the validation set. The highest contributing covariates for soil AWC prediction were the Landsat multitemporal images with bare soil pixels, mean diurnal, and annual temperature range. Under the current climate conditions, soil available water content (AW) increased during the dry period (April to August). May had the highest increase in AW (∼17 mm m^-1) and decrease in September (∼14 mm m^-1). The used methodology provides support for AWC modeling at 30 m resolution, as well as insight into the adaptation of crop growth periods to the effects of climate change.

Land use modification causes slow, but predictable, change in soil microbial community composition and functional potential

BACKGROUND

Bacterial communities are critical to ecosystem functioning and sensitive to their surrounding physiochemical environment. However, the impact of land use change on microbial communities remains understudied. We used 16S rRNA gene amplicon sequencing and shotgun metagenomics to assess soil microbial communities' taxonomic and functional responses to land use change. We compared data from long-term grassland, exotic forest and horticulture reference sites to data from sites that transitioned from (i) Grassland to exotic forest or horticulture and from (ii) Exotic forest to grassland.

RESULTS

Community taxonomic and functional profiles of the transitional sites significantly differed from those within reference sites representing both their historic and current land uses (P < 0.001). The bacterial communities in sites that transitioned more recently were compositionally more similar to those representing their historic land uses. In contrast, the composition of communities from sites exposed to older conversion events had shifted towards the compositions at reference sites representing their current land use.

CONCLUSIONS

Our study indicates that microbial communities respond in a somewhat predictable way after a land use conversion event by shifting from communities reflecting their former land use towards those reflecting their current land use. Our findings help us to better understand the legacy effects of land use change on soil microbial communities and implications for their role in soil health and ecosystem functioning. Understanding the responsiveness of microbial communities to environmental disturbances will aid us in incorporating biotic variables into soil health monitoring techniques in the future.

Soil health and management matters: A survey of field tree nursery producers

Extensive calls for increased tree planning worldwide are highlighting the need for management changes in the field tree nursery sector. Healthy soil is the foundation for sustainable agricultural systems, and best practices for soil management confer tangible benefits to producers as well as broader system-wide benefits. However, field tree producers lack the foundational resources needed to implement, manage, and evaluate soil health practices within their operations. Furthermore, tree producers are unique in that their primary product is central to the sustainable development of urban spaces and are facing increased demand for high-quality trees. There is subsequently a two-pronged need. First, a greater understanding of the key objectives, opportunities, and challenges driving soil management in tree production is required to support the development of specified practices, within the sector. Second, a greater characterization of the short- and long-term value of trees is required to incentivize the soil health practices that will support resilience in tree production systems. The study characterizes the soil health and management practices implemented in Ontario by field tree nursery producers. A questionnaire was administered in the summer of 2020 to Ontario tree nursery producers within the Landscape Ontario Horticultural Trades Association (N = 29). Responding producers provided insight into soil management practices, opportunities and challenges. Tree nursery producers expressed a need for resources to support cover crop usage and comprehensive soil testing to improve tree performance. Reflection on current soil management challenges and opportunities highlights the benefits of considering soil management as one aspect within the broader social-ecological system.