Soil Retention Research Articles

Desulfurization steel slag improves the saline-sodic soil quality by replacing sodium ions and affecting soil pore structure

Flue gas desulfurization steel slag (DS), a solid waste produced by coal power plants and steelworks, was proposed as an amendment for the remediation of saline-sodic soil. A pot experiment including three dosages of DS alone (1%, 5%, 10% w/w) and their combination with fulvic acid (FA, 1%, w/w) was conducted to evaluate the potentials of DS as an amendment and to explore remediation mechanism of DS combined with FA on saline-sodic soil. The soil salinity, nutrition, pore structure, water retention, consistency, and desiccation cracking of DS and FA-amended soils were determined. Application of DS resulted in a significant reduction of pH, sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) of saline-sodic soil. The DS amendment significantly increased the 6–15 μm pore volume of soil. The combination application of DS and FA showed better effect than the DS alone. The DS amendments at 5% and 10% significantly increased the field water capacity, permanent wilting point, and available water content of the soil, whereas significantly decreased the plastic limit, liquid limit, and plastic index. The DS alone and combined with FA could effectively control the development of desiccation cracking, reduced significantly the crack area density and average width of cracks of the soil. Consequently, the improvement of alkalinity and soil physical properties by DS amendment significantly increased the yield of alfalfa grown on saline-sodic soil. The remarkable improvement of physical properties of saline-sodic soil contributed to the decrease of SAR and ESP by the Ca2+ in DS replacing the Na + at soil colloid sites. Our results suggested that DS amendments alone or combined with fulvic acid have great potential as saline-alkali soil amendment.

Understanding the balance between soil conservation and soil water storage capacity during the process of vegetation restoration in semi‐arid watersheds in the Loess Plateau, China

AbstractIn the Loess Plateau, gaining insights into the water storage and soil retention functions of diverse vegetation types, especially, in the semi‐arid watersheds is crucial for identifying the key factors necessary to ensure sustainable development and achieve land degradation neutrality. In this study, five different land use types such as forest, shrub, artificial grass, and natural grasslands were surveyed from 2014 to 2020. Meanwhile, bare land was also used as a control plot. The trade‐off between erosion mitigation and water consumption indicator was quantified based on the ecosystem services perspective benefits. Our results showed that there are significant differences among different land use types (p < 0.05): natural grassland > shrubs > artificial grassland > forests. Vegetation restoration was able to change the soil particle size distribution, increasing clay and silt content, and decreasing sand particles. During the growing season, surface soil water storage decreased in all land use types coinciding with the higher decrease in the control plot. The change in surface water storage in the forest was the most stable, with a decrease of 0.13 mm. The trade‐off between erosion mitigation and water consumption indicator was less than 0 for all vegetation types, which indicates a synergistic effect on soil conservation and water storage benefit. Our results demonstrated that shrubs can register the most balanced benefit of water storage and soil preservation. This is a solid basis for the selection of specific vegetation types and the optimization of the watershed landscape in the middle reaches of the Yellow River, characterized by vulnerable areas due to aridification.

Study on the impact of vegetation change on ecosystem services in the Loess Plateau, China

Vegetation change has a non-negligible role in the impact of ecosystem services (ESs). Quantitative assessment of vegetation ecosystem services is the basis for sustainable regional development. Using the Chinese Loess Plateau (LP) as the study area, this study firstly analysed the spatial and temporal characteristics of vegetation change and used a Geodetector model to reveal the driving mechanism. Next, this study applied the InVEST model to quantitatively assess the four services of carbon storage, habitat quality, soil conservation and water yield, and explored the vegetation ecosystem service balance through vegetation type transfer. The results showed that (1) there was a trend towards an increase in the area of all vegetation types, with sparse vegetation being the most pronounced. Areas of damaged vegetation were concentrated in urban and peripheral areas, as well as wasteland and bare ground. (2) Annual precipitation, soil types and cumulative afforestation area ratio were the main drivers of vegetation change on the LP. (3) Restoration of woodland enhanced carbon storage, habitat quality and soil retention services for vegetation on the LP, while water yield decreased by 31.66%. The restoration of vegetation area did not enhance all ecosystem services. This study may provide a reference and basis for the sustainable management of regional ecosystems.

Effectiveness of protected areas in the Three-river Source Region of the Tibetan Plateau for biodiversity and ecosystem services

Protected areas are widely recognized as crucial for biodiversity conservation and ecosystem service maintenance. In recent decades, countries worldwide have made great progress in expanding the scope of protected areas. However, the evaluation of conservation effectiveness is insufficient due to limited resource inputs. In this study, we assessed the nature reserves’ effectiveness in conserving biodiversity and ecosystem services for the Three-river Source of the Tibetan Plateau in China over the past 20 years at multiple scales. Our findings revealed substantial improvements in biodiversity value, habitat quality, water retention carbon storage, and a slight decline in soil retention. Furthermore, implementing conservation measures within the nature reserves has resulted in better ecological conditions than areas outside. In terms of the different protection zones within the nature reserves, the core areas showed the highest improvement in ecological conditions, followed by the buffer areas and experimental areas. These results indicate a positive influence of ecological projects on conservation objectives. Additionally, the study indicated the effectiveness of more stringent conservation management. Limiting human activities and taking measures to protect soil retention in the Three-river nature reserves is urgent.

Scenario modeling of ecosystem service trade-offs and bundles in a semi-arid valley basin

Amidst the rapid urbanization process, substantial transformations have emerged within ecosystem services, exerting profound ramifications on the sustainability of ecosystems. Nevertheless, an existing dearth persists in delineating the intricate interplay of trade-offs and synergies, as well as ecosystem services bundles under diverse future scenarios. This study harnesses the Convolutional neural network-Long and short-term memory-Cellular automata model to prognosticate and dissect the temporal and spatial dynamics of four distinct ecosystem services (soil retention, water yield, carbon storage, and habitat quality) across the semi-arid valley city of Lanzhou from 2000 to 2030 under multiple scenarios. The SPSS model methodically quantifies the intricate trade-offs and synergies interwoven among these services, while cluster analysis reveals ecosystem services bundles across varying scales. Notably, (1) convolutional neural network-long and short-term memory-cellular automata model demonstrates remarkable proficiency in accurately forecasting land use, boasting an elevated precision level of 0.93. (2) The trajectories of carbon storage and water yield demonstrate a diminishing pattern between 2000 and 2020, against the ascending trends observed in soil retention and habitat quality. Within the ecological priority scenario for 2030, water yield experiences a sluggish decrease, while the abatement of soil retention, carbon storage, and habitat quality degradation is maximized. (3) The trade-offs (3 pairs) and synergies (3 pairs) among ecosystem services within the study locale exhibit a state of relative equilibrium. Noteworthy among these interactions is the prominent trade-off correlation (−0.101) between soil conservation and carbon storage within the city priority scenario. (4) Four discernible ecosystem services bundles manifest at the grid scale from 2000 to2030. Conversely, three bundles at the county scale in 2000, eventually decrease to two bundles between 2010 and 2030, hinting at a diminishing trend concerning the number of ecosystem services bundles as spatial scales coarsen. Furthermore, whereby these bundles progressively aggregate spatially over time.

Spatial and temporal driving mechanisms of ecosystem service trade-off/synergy in national key urban agglomerations: A case study of the Yangtze River Delta urban agglomeration in China

Clarifying the ecosystem service (ES) trade-off/synergy is a prerequisite for scientific implementation and optimization of integrated ecological system management strategies, especially in highly urbanized areas with declining eco-environmental carrying capacity. This study took China's Yangtze River Delta urban agglomeration (YRDUA) as an example. First, we used a pixel-by-pixel analysis based on dynamic spatial correlation to quantify the trade-off/synergy among the 6 primary ESs' change amounts from 2005 to 2020 (habitat quality, soil retention, carbon sequestration, water yield, food production, leisure and recreation). Then, we integrated the multiple ES trade-off/synergy and explored their driving factors by spatial cluster analysis and geographically and temporally weighted regression (GTWR). The results showed synergy between supporting and regulating services predominated while regulating services were mostly trade-offs with regulating and cultural services. The trade-off/synergy of the 15 ES functional pairs within YRDUA can be downscaled into 4 ES trade-off and synergy bundles. Furthermore, the climate drivers (annual highest temperature (TH), annual total precipitation (PRE), annual total solar radiation (SRT)) significantly influenced the spatial heterogeneity of the 6 ESs in the YRDUA. The socio-economic drivers (night light index (NLI), gross domestic product (GDP)) and land use drivers (proportion of arable land (ALP), proportion of construction land (CLP), proportion of woodland (WLP)) had a more remarkable power of explanation for the ES temporal variation and ES trade-off/synergy. YRDUA and other urban agglomerations can use the study's findings to develop differentiated integrated ecological management strategies.

Influence of SOM Composition, Clay Minerals, and pH on 2,4-D and MCPA Retention in Peri-Urban Soils

The use of ionic herbicides in urban and peri-urban areas has serious environmental and health consequences due to their common overapplication and mobility in the soil profile. The specific objective of this study was to evaluate the influence of soil organic matter (SOM) fractions and clay minerals on the retention of 2,4-D and MCPA on loamy sand and loam topsoil materials under the pH range of 3–7. The results obtained indicate their weak, unfavorable, and physical sorption, presumably governed by partitioning. 2,4-D exhibited high affinity for polar SOM fractions as well as to kaolinite and montmorillonite, both present in the studied peri-urban soils. MCPA sorption was mainly related to soil fulvic (FA) and humic acid (HA) content; however, the pesticide was sorbed to a lesser extent than 2,4-D due to its great water solubility. This was reflected in MCPA’s low Koc values (41.33 and 84.21), indicating its very high mobility and leachability in the studied soils. Meanwhile, 2,4-D was moderately mobile in sandy soil while classified as a non-leacher in the loam topsoil material. Both herbicides were preferably retained at a low soil pH (3–4), which, together with soil amendment with exogenous, well-humified organic matter, could minimize the potential health and environmental risks of their application.

Integrating the impacts of vegetation coverage on ecosystem services to determine ecological restoration targets for adaptive management on the Loess Plateau, China

AbstractAchieving sustainable resource management is essential to address the rising demand for ecosystem services. The absence of targeted vegetation restoration based on ecological function positioning has, nevertheless, made it challenging to effectively combat the ecological decline. This study attempted to classify four dominant ecological function areas based on the assessment of water conservation, soil retention, habitat quality, and food supply and determined the vegetation coverage threshold by exploring the trade‐offs among ecosystem services and constraint effects between ecosystem services and vegetation coverage. The results highlighted the impacts of ecosystem services on vegetation coverage across the years 1990, 2000, 2010, and 2020 and established differentiated ecological restoration targets. The optimal vegetation coverage in the water conservation area was found to be 58%–63%, in the soil retention area was 52%–56%, in the food supply area was 34%–40%, and in the habitat quality area was 65%–70%. Finally, the study identified the subwatersheds with reasonable vegetation coverage, excessive restoration, and those that failed to reach the optimal vegetation coverage to develop targeted restoration strategies for each subwatershed according to its unique vegetation conditions. This study provides valuable insights into the specification of differentiated vegetation coverage targets and serves as a useful tool for more effective ecosystem planning and management.

Co-application of biochar and organic amendments on soil greenhouse gas emissions: A meta-analysis

Biochar has been shown to reduce soil greenhouse gas (GHG) and increase nutrient retention in soil; however, the interaction between biochar and organic amendments on GHG emissions remain largely unclear. In this study, we collected 162 two-factor observations to explore how biochar and organic amendments jointly affect soil GHG emissions. Our results showed that biochar addition significantly increased soil CO2 emission by 8.62 %, but reduced CH4 and N2O emissions by 27.0 % and 23.9 %, respectively. Meanwhile, organic amendments and the co-application with biochar resulted in an increase of global warming potential based on the 100-year time horizon (GWP100) by an average of 18.3 % and 26.1 %. More importantly, the interactive effect of biochar and organic amendments on CO2 emission was antagonistic (the combined effect was weaker than the sum of their individual effects), while additive on CH4 and N2O emissions. Additionally, our results suggested that when biochar is co-applied with organic amendments, soil GHG emissions were largely influenced by soil initial total carbon, soil texture, and biochar feedstocks. Our work highlights the important interactive effects of biochar and organic amendments on soil GHG emissions, and provides new insights for promoting ecosystem sustainability as well as mitigating future climate change.

Optimization of tropical rainforest ecosystem management: implications from the responses of ecosystem service values to landscape pattern changes in Hainan Tropical Rainforest National Park, China, over the past 40 years

Exploring the comprehensive impact of landscape pattern changes on regional ecosystem service values (ESVs) over a long time series is significant for optimizing ecosystem management. This study took Hainan Tropical Rainforest National Park (HTRNP) as a case and first assessed its five vital ecosystem services (ESs): water supply (WS), water purification (WP), carbon storage (CS), soil retention (SR), and habitat quality (HQ). Based on the ESs assessment results, we further calculated their ESVs and quantified the responses of ESVs to landscape pattern changes during 1980–2020. The results revealed that: (1) Forestland is the basal landscape type of HTRNP. Landscape patterns changed significantly after 2000; the proportion of both cultivated land and grassland decreased, while the proportion of forestland, water, and construction land increased; with the areas and landscape dominance of both forestland and water increased, the agglomeration and connectivity of the overall landscape increased and its homogenization decreased. (2) WS, WP, CS, and SR services tended to weaken, and HQ service tended to strengthen. The spatial heterogeneities of WS and SR changed significantly over time. WS, HQ, SR, and CS are the main contributors to the total ESV. During 1980–2020, the four ESVs of WS, WP, SR, and CS showed a decreasing trend; HQ’s ESV tended to increase, and the total ESV tended to decrease. (3) The increase of areas and dominance in forestland and water was the main reason that HQ’s ESV tended to increase, and WP’s ESV and CS’s ESV tended to decrease. The construction land scale was relatively small, so its impacts on ESVs were limited. The responses of both WS’s ESV and SR’s ESV to landscape pattern changes were insignificant due to the impacts of topographic and climatic factors. The study results provide a reference for managing and optimizing HTRNP’s ecosystem to improve its integrated benefits of crucial ESs.

Effects of saline water on soil properties and red radish growth in saline soil as a function of co-applying wood chips biochar with chemical fertilizers

BackgroundCurrently, using unconventional water sources in agriculture has become necessary to face overpopulation worldwide. Therefore, a pot experiment was carried out to evaluate the effects of irrigation with saline water in the presence of co-applied wood chips biochar (WCB) with chemical fertilizers on physicochemical properties and nutrient availability as well as growth parameters, and yield of red radish (Raphanus sativus L.) grown in the saline sandy soil.MethodsThe WCB was added to the saline sandy soil at levels of 0 (control), 2.5, and 5% w/w. Then, this soil was cultivated by red radish plants and irrigated with saline water (5 dS m− 1). This experiment was performed in a randomized complete block design with three replicates.ResultsCompared with the control treatment, WCB treatments increased significantly soil water holding capacity by 34.8% and 73.2% for levels of 2.5 and 5%, respectively. Soil pH decreased significantly in all WCB treatments. The relative increase in the total available nitrogen over the control was 30.1 and 103.5% for 2.5 and 5% wood chips biochar, respectively. Compared to the control, applying WCB at 2.5% led to an increase in the fresh root weight of red radish plants by 142.7%, while 5% caused a decrease in the fresh root weight of red radish plants by 29.4%.ConclusionRecently, WCB represents an interesting approach to the rehabilitation of saline soils and the management of using saline water sources. It is recommended that combined application of WCB at a level of 2.5% with chemical fertilizers in order to improve red radish growth and nutrient retention in the saline sandy soil which preserves the ecosystem as well as increases productivity leading to the reduction of costs.

Matching ecosystem services supply and demand in China's urban agglomerations for multiple-scale management

The unprecedented urbanization rate has profoundly impacted ecosystem functions and increased the demand for ecosystem services. Moving towards sustainable cities requires an insightful understanding of ecosystem services supply and demand (ESSD). However, most ESSD studies ignore the spillover effects of ecosystem services, hindering sustainable urban agglomeration (UA) development from multiple spatial scale perspectives. This study evaluated the supply, demand, and sustainability of urban ecosystem services, including food production, water retention, soil retention, and carbon sequestration, by considering 19 UAs in China (including 236 cities). The results showed that the supply and demand of urban ecosystem services increased from 2000 to 2020, together with spatial heterogeneity. A decrease in the sustainability of food production was observed at medium UAs. Large UAs can achieve sustainability of all studied ecosystem services at both the UAs' and national scales. However, the medium UAs in the northwest were unsustainable regarding water retention and carbon sequestration at the UAs’ scale. Land use/land cover (LULC) change was the key factor in ESSD change, followed by population. Finally, policy implications were proposed, including bringing ESSD into land use decision-making, reducing ecosystem service demand, implementing targeted restoration, and multiple-scale management.

Deciphering the impact of wind erosion on ecosystem services: An integrated framework for assessment and spatiotemporal analysis in arid regions

Wind erosion, a crucial disruptor of ecosystem health and stability, especially in arid regions, remains unincorporated in extensively utilized ecosystem services (ESs) quantification models such as InVEST. This neglect results in a gap: the profound influence of wind erosion on ESs remains largely underexplored and unquantified. Moreover, current models predominantly concentrate on individual ESs, thus bypassing the necessary comprehensive evaluation of various ESs' developmental status. To address this gap, we propose a systematic framework based on the Distance between Indices of Simulation and Observation (DISO), which integrates the Revised Wind Erosion Equation (RWEQ) and key modules of the InVEST model to derive a Comprehensive Ecosystem Services Assessment Index (CESAI) for arid regions. We evaluated five ESs, including water yield, soil retention, sand fixation (measured by wind erosion), carbon storage, and habitat quality. To further investigate the influence of each ES on the comprehensive assessment, we employed a suite of statistical methods, including independent samples t-tests and a generalized additive model (GAM), to elucidate the complex relationships and significant effects of wind erosion on the CESAI. The results of the t-tests and GAM highlighted the significant influence of wind erosion, which demonstrated the highest edf-value (2.000) and the highest F-value (1039.6, p < 0.001). Spatiotemporal dynamics show that ES functionality in Uzbekistan has deteriorated from 1992 to 2020, a trend starkly exemplified by the severe harm inflicted by the Aral Sea crisis. Drawing upon the DISO concept, we have innovatively designed a framework that steers the CESAI index, a comprehensive instrument for evaluating ESs. Beyond providing a holistic perspective on ESs assessments, this framework also deciphers the multifaceted interplay within ecosystems through statistical dissection of each service's influence. Collectively, our findings deepen the understanding of ESs dynamics, shedding light on the crucial role of wind erosion within arid ecosystem service assessments.

Chloride and phosphorus retention and release in soils surrounding a salt-contaminated lake in West Michigan

Salinization in freshwater ecosystems has become an increasingly prevalent issue. Past studies indicate that increased salinity levels in lakes can impact biota, stimulate internal nutrient loading, and prevent seasonal turnover, potentially resulting in impairment to the lake ecosystem. Salt retention in soils and groundwater causes elevated salt concentrations in fresh water long after road salt was applied. We examined salt retention and release in soils collected near the tributaries flowing into and out of a salt-impacted urban lake. We distributed each soil sample into plastic trays and exposed them to three treatments, conducted in series: (1) non salt-contaminated water as a conditioning rinse; (2) salt-contaminated water to mimic salt de-icer runoff; and (3) non salt-contaminated water to determine salt release. We measured retention of chloride from each soil sample based on how much chloride was measured in water draining the soil (effluent). We observed considerable variability among sites presumably because of soil heterogeneity, although overall the soils in our study area retained a modest amount of chloride (mean of ∼29 mg/L) from simulated salt runoff events, even at short exposure times (<30 min). In addition, some soils released chloride following a relatively salt-free rinsing event. There was an overall positive relationship between percent soil organic matter and Cl- retention. We also measured the impact of chloride on bioavailable phosphorus concentration in the effluent, which was relatively modest and variable. Soil total phosphorus had a strong positive correlation with %SOM. Our results suggest that in addition to direct runoff of salt de-icers from roads to lakes, soil retention can also serve as a chloride source that can be released over time, resulting in a delayed impact to aquatic ecosystems.

Prediction of Cu(II) retention, sorption mechanism and biochar effect in tropical soil

The sorption behavior of potentially toxic metals in soils influences their spread to other environmental compartments and their bioavailability to life forms. The present study evaluated the sorption of Cu(II) ions in two representative soils from Yala and Tindinyo regions along River Yala in Lake Victoria basin, Kenya. The sorption experiments were carried out in single component solution systems using the batch technique. The equilibrium data was modeled using Henry’s isotherm model and four two-parameter isotherm models. Freundlich and bi-phasic Henry’s isotherm models best described the data, while both negative constants for Langmuir and Elovich necessitated rejection of the models. The y-intercept values for Henry’s monophasic fitting were negative, but the corresponding soil solution values of 0.43 μg/mL and 0.45 μg/mL for the Yala and Tindinyo soils, respectively, were taken as the background Cu(II) solution levels. We propose that in cases where the y-intercepts are negative, the bi-phasic Henry’s model can be used to predict a soil’s critical retention limit for a given pollutant, while the corresponding soil solution amount gives the permissible level in the soil solution. Using bi-phasic Henry’s model, the critical Cu(II) retention limits were determined as 300.11 μg/g and 301.48 μg/g for Yala and Tindinyo soils, respectively. The corresponding soil solution amounts were 3.47 μg/mL and 3.36 μg/mL for Yala and Tindinyo soils, respectively. The background and equilibrium soil solutions were below and above the WHO limit of 2 μg/mL for drinking water, respectively, while the sorbed amount was above the WHO limit of 36 μg/g soil. These findings indicate that a contaminant in soil may not pose any toxicity risk unless its concentration exceeds the critical retention limit, and that a pollutant’s toxicity is dependent on the soil solution amount rather than the total amount in soil. Dissolved organic carbon was more dominant than clay fractions in influencing the degree of sorption in both soils. Surface complexation between Cu(II) ions and carboxylic functional groups is hypothesized as a plausible sorption mechanism. Immobilization of Cu(II) in soil was significantly increased by amendment with fish-scales-derived biochar which, therefore, has promising potential application in mitigating environmental contamination by metals.

Characteristics of Organic Manures and Its Effect on Physical Properties of Soil in Pearl Millet

Organic manures are rich source of nutrients such as nitrogen, phosphorus, and potassium, as well as micronutrients such as calcium, magnesium, and sulfur, which are essential for plants. It also contains organic matter that improves soil structure, water-holding capacity, and aeration. The study focused on evaluating two types of organic manures, i.e. Farmyard manure (FYM) and vermicompost. Results showed that vermicompost had higher nutrient content them FYM. A field experiment was conducted during kharif season 2018 at Agronomy farm, S.K.N. College of Agriculture Jobner (Rajasthan). The design of experiment was factorial randomized block design with three replications. The experiment comprised five treatments of organic manures (Control, vermicompost @ 2.5 t ha-1, vermicompost @ 5 t ha-1, FYM @ 5 t ha-1 and FYM @ 10 t ha-1) and four treatments of fertility levels (Control, 50 per cent RDF (recommended dose of fertilizer), 75 per cent RDF and 100 per cent RDF). The variety used for experiment was RHB-173 of pearl millet. Results showed that the application of FYM @ 10 t ha -1 significantly decreased the bulk density and increased the saturated hydraulic conductivity over control. The maximum water retention of soil (12.86 per cent and 3.28 per cent) at 33kPa and 1500 kPa were recorded under the treatment vermicompost @ 5 t ha-1 being at par with FYM @ 10 t ha -1. Thus, addition of FYM @ 10 t ha -1 improves the physical soil properties.

Elastic Gauge Wheel with Irregular Cavity for Improving Seed Furrow Structure and Seeding Quality

The traditional gauge wheel has poor performance in reducing the adhesion to soil and constructing seed furrow, which results in lower seeding quality of the planter. To reduce the adhesion of the gauge wheel to the soil and build a well-structured seed furrow, an elastic gauge wheel with soil retention groove and irregular cavity was designed in this study. The soil retention groove built ridges on both sides of the seed furrow and avoided the gauge wheel compacting the seed furrow sidewalls. The irregular cavity increased the elasticity of the gauge wheel and allowed the wheel to squeeze the soil on both sides of the seed furrow, which reduced the soil adhesion of the wheel and built stable ridges. Soil moisture content was chosen as the experimental factor for comparative tests to evaluate the soil adhesion and the constructed seed furrow of the gauge wheel with an irregular cavity and the traditional gauge wheel. The experimental results showed that the viscosity reduction rate of the gauge wheel with the irregular cavity was not less than 12.61%. Compared with the traditional gauge wheel, the seed furrow constructed by the irregular cavity gauge wheel had ridges on both sides and less backfill soil, and the soil compaction of sidewalls decreased by 18.16%. The field experiment was designed using the Box–Behnken design. The working speed, downforce, and planting depth were taken as experimental factors, and the soil adhesion of the gauge wheel and the consistency of planting depth were taken as evaluation indicators. The optimal operating parameters of planter obtained by Design-Expert 8.0.6 software were as follows: the working speed was 8 km·h−1, the downforce was 844 N, and the planting depth was 65 mm. The verification test of the optimal operating parameters showed that the soil adhesion mass of the gauge wheel was 123.65 g and the coefficient of variation of the planting depth was 5.35%. This study provides a reference for the mechanized construction method of seed furrow by precision planter and the structural design and performance optimization of gauge wheels.

Soil Organic Matter Composition and pH as Factors Affecting Retention of Carbaryl, Carbofuran and Metolachlor in Soil.

The majority of studies concerning the environmental behavior of hydrophobic pollutants in soil consider soil organic matter (SOM) content as a main factor influencing chemical retention, whereas the composition of SOM and its individual fraction share are often neglected. In the present paper, carbaryl, carbofuran and metolachlor retention by loamy sand and loam topsoil materials is compared and referred to humic acids (CHA) and the residual carbon (CR) content of SOM. Additionally, the sorption-desorption behavior of agrochemicals in soils was tested at a pH of three to seven. Calculated isothermal parameters point to favorable, spontaneous and physical pesticide sorption. Groundwater ubiquity score (GUS) indexes confirmed the low leaching ability of metolachlor on soils and moderate of carbofuran. The high affinity of carbaryl to CR may explain its pronounced sorption in loam soil and the lowest percolation potential. Carbofuran retention in soils was associated with montmorillonite (Mt) and CR fractions. Meanwhile, metolachlor uptake was related to humic acid and Mt content of the soils. Lower pH enhanced retention of the agrochemicals, except for carbaryl sorption in sandy loam soil. Results of this study highlight that SOM composition and mutual share of individual organic carbon fractions alongside pH may play a crucial role in predicting non-ionic pesticide behavior in soil.

Adsorption behavior of benzene on clay mineral surfaces at different temperatures and air humidity based on molecular simulation

Benzene poses a severe threat to human health due to its prevalence and carcinogenicity. The adsorption behavior of benzene on clay mineral surfaces is significant to its migration and retention in soils. Therefore, it is crucial to understand the mechanism of benzene adsorption behavior under different environmental conditions. In this study, a series of Grand Monte Carlo (GCMC) simulations were performed to obtain benzene isotherms on clay under various temperatures and air humidity. The adsorption mechanisms were investigated via analysis of the distribution of interaction energy, density, and orientation of adsorbed benzene and water. Results show that benzene form multiple layers on mineral surfaces, and surfaces have a great impact on the first layer of adsorbed benzene. The impedance effect of temperature on benzene adsorption is attributed to the temperature-dependent chemical potential of benzene, but not the interaction between benzene and surfaces, which is slightly temperature-reliant. Humidity shows different inhibition effects on benzene adsorption due to different surface hydration behavior and competitive adsorption between water and benzene. Benzene tends to be adsorbed on hollow sites on kaolinite surfaces, which is the same as water. The surface cations on montmorillonite and mica are significant to benzene and water adsorption, and their density distribution causes different competitive adsorption behavior.

Long-term retention of carbon from litter decay in diverse agricultural soils in Canada and New Zealand

Identifying the primary regulators of plant litter decay in agricultural soils is important for understanding ecosystem function now and for managing post-harvest litter in a warmer world. We conducted a litter decay study at 11 sites in Canada and New Zealand with diverse soils and climates. We incorporated 13C-labelled barley litter into the surface 10 cm of soil and monitored amount remaining over 8–10 years; at five sites litter was also applied to the soil surface to simulate no-tillage. Our objectives were to evaluate litter decay as influenced by soil type, tillage practice, and environmental conditions, and quantify the most important factors controlling C retention in soil. Loss of C via decomposition occurred quickly – more than half was lost within 1 year and only about 5–12% remained at the end of the experiment. A double exponential decay model, based on temperature and developed from the first 5 years of the study, accurately described litter decay, but only after re-tuning using measurements from the full experimental period. Including precipitation in the model further improved its fit. Soil properties exerted minimal discernible influence on the amount of litter C remaining, implying that properties such as the amount and surface area of clay minerals, were less important than climate in limiting litter decay or enhancing retention of C in soil. Comparison of litter application treatments showed that no-till slowed decay of plant litter, but only for a short time (∼1 yr) and only in environments with a mean annual precipitation of <1000 mm. These findings have implications for the role of soils in climate mitigation. If only 10% of added plant litter C remains in soil beyond a few years, regardless of climate, residue placement, or soil type, then rates of soil gain are limited without substantive increases in residue inputs.