Low Soil Organic Matter Content Research Articles

Carbon dioxide fluxes and the dominant role of vegetation in recently created and reference Gulf Coast marshes

AbstractCoastal wetlands are one of the most productive ecosystems on Earth with the capacity to sequester large amounts of carbon dioxide (CO2). Wetland loss due to anthropogenic and natural causes reduces the carbon (C) storage capacity and potentially releases previously fixed C in biomass and soil to the water column and atmosphere through decomposition. Coastal wetland restoration has the potential to mitigate some of the C losses depending on the balance of C fluxes. However, the role of vegetation and environmental conditions in governing rates of C accumulation in restoration sites is not well resolved. The purpose of this study was to examine seasonal C fluxes, specifically, gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE) of CO2 in unvegetated and vegetated (Spartina alterniflora) areas of a 2‐year old created marsh, and S. alterniflora and Spartina patens communities in a “natural” reference brackish marsh. S. alterniflora‐dominated areas were sinks for CO2 in both the newly created and reference marsh with an average CO2 uptake rate of 7.0 ± 1.0 μmol m−2 s−1. The unvegetated areas in the newly created marsh and S. patens areas in the reference marsh had approximately net neutral CO2 fluxes. S. alterniflora areas of the created marsh had similar carbon fluxes to that in the reference marsh, despite a much lower soil organic matter content. Because vegetation develops much faster than soil properties, restored marshes can be a C sink equivalent to natural marshes as soon as the marsh is vegetated. Ecosystem productivity and C assimilation in S. alterniflora areas of the reference marsh were enhanced by lower elevations (up to 6 cm) and higher soil bulk density (up to 0.28 g cm−3). At similar elevations, S. alterniflora in both the created and reference marshes was a greater C sink than S. patens areas of the reference marsh. Our findings illustrate that establishment of vegetation is critical to promoting C sink functions in created marshes and, notably, species do matter.

Impact of gradient zero-valent iron pollution from steel works on soil microaggregate geochemical processes and dissipative structures

Abstract: Zero-valent iron (ZVI) contamination from steel works poses significant threats to soil quality and ecosystem health, particularly affecting soil microaggregates, which are fundamental to soil structure and function. In this study, we systematically investigated the impact of gradient ZVI pollution on the organic geochemical environment of soil microaggregates around steel works located in the core water source area of the Middle Route of the South-to-North Water Diversion Project in China. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), were employed to comprehensively characterize the geochemical processes, mineralogy, and organic matter environment of soil microaggregates. The findings revealed that soils near the steel works were acidified and strongly oxidized, with heavy metal contents, particularly Fe, significantly decreasing with increasing distance from the steel works (Fe content decreased from 27,516.2 mg/kg to 23,492.6 mg/kg). The pH of soils near the steel works was lower, while oxidation-reduction potential (ORP) and electrical conductivity were higher. XPS analysis indicated a higher content of reactive oxygen species (ROS) near the steel works and significantly lower soil organic matter content. The iron valence distribution showed spatial differences, with higher Fe2⁺ content on the surface of soil microaggregates near the steel works and Fe³⁺ dominating in areas farther away. These results suggest an evolutionary sequence of ZVI from Fe (0) oxidation to Fe(II) and then to Fe(III). The formation of dissipative structures in soil microaggregates due to ZVI contamination significantly affects soil physicochemical properties and the organic environment. This study provides valuable insights into the multifaceted impacts of industrial activities on soil ecosystems and offers a scientific basis for soil conservation and remediation strategies.

Cultivated Land Quality Assessment and Obstacle Factors Diagnosis in Changtu County, Northeast China

ABSTRACTEffective evaluation of cultivated land quality is crucial for sustainable agricultural management. Existing research often focuses on regional scales and lacks sufficient detailed analysis of spatial distribution and limiting factors at localized scales. This study aims to select the key indicators to evaluate cultivated land quality and analyze their influence on cultivated land quality at the county level. Taking Changtu County as the research area, principal component analysis (PCA) was employed to identify the most effective Minimum Data Set (MDS) for evaluation, including cultivated layer thickness, soil organic matter (SOM), pH, bulk density (BD), and cultivated layer texture. Additionally, an obstacle degree model was used to analyze restricting factors and their degrees of impact. Results showed that the constructed MDS could replace all indicators for cultivated land quality evaluation. Quality was higher in central areas and lower in eastern and western regions. SOM content decreases with the decrease of quality grade, significantly affecting the quality distribution, and pH in the medium category (Grades III and VI) cultivated lands were lower compared to other categories. Low organic matter content and low pH levels were the main obstacles affecting cultivated land quality, with average obstacle degrees of 43.5% and 29.3%, respectively. Low SOM content significantly affected land quality, particularly in the western region, whereas acidic soils in the eastern region influenced quality grade distribution. Thus, strategies for pH control and SOM enhancement are essential for improving cultivated land quality. This study provides valuable insights into sustainable agriculture.

Meta-Analysis of the Effects of Straw Incorporation on Maize Yield and Water Use Efficiency in China under Different Production Conditions

Maize plays a crucial role in China’s grain production, with a cultivation area reaching 44.22 million hectares and an annual yield of 289 million tons in 2023. However, the challenge remains on how to further increase maize yield and water use efficiency (WUE) without adding to the environmental burden. To systematically evaluate the impact of straw incorporation under varying production conditions on maize yield and WUE, this study collected experimental data from multiple locations across China. A meta-analysis was conducted to compare the effects of straw incorporation versus no incorporation, and the main influencing factors were identified using correlation analysis and a random forest model. The results indicate that straw incorporation significantly enhances both maize yield and WUE, with the most pronounced improvements observed under conditions of an average growing season temperature of 19–23 °C, soil pH of 6.5–7.5, low initial soil organic matter content, and deep plowing for straw incorporation. Additionally, moderate nitrogen application rates and straw incorporation amounts (9000–15,000 kg·ha−2) also significantly boost maize yield and WUE. Field management practices and meteorological conditions are identified as the primary factors affecting maize yield and WUE under straw incorporation conditions. Therefore, straw incorporation stands out as an effective agricultural practice for achieving high maize yields and efficient resource utilization. The findings of this study provide valuable insights for global food security and the sustainable development of agriculture.

Assessing the potential of multi-source remote sensing data for cropland soil organic matter mapping in hilly and mountainous areas

Cropland soil organic matter (SOM) is recognized as a significant carbon reservoir in terrestrial ecosystems. Digital mapping of SOM in croplands is essential for comprehending the global carbon cycle. Accurately mapping cropland SOM using multi-source remote sensing data has been effectively incorporated into prediction models across various scales. However, the impact of multi-source remote sensing data on cropland SOM mapping outcomes in hilly and mountainous regions remains insufficiently understood. In this study, Jiangyou City, located in Sichuan Province, China, was chosen as a representative example of hilly and mountainous regions. Fifteen distinct feature combinations were devised using three remote sensing variables (Sentinel-1, Sentinel-2, and Landsat-8) along with DEM data. Feature selection was conducted using the Boruta algorithm. Subsequently, the RF, SVR, Cubist, and INLA-SPDE models were adopted to create spatially detailed distribution maps of cropland SOM for the region. Additionally, an uncertainty analysis was performed on the cropland SOM mapping results. The results indicate the following: (1) The INLA-SPDE model, which integrates both data information and spatial structure, achieves the highest accuracy and the less uncertainty in cropland SOM mapping, with an R2 of 0.647 and an RMSE of 4.227 g/kg. (2) Optical imagery is more important than SAR images, but their combination enhances model accuracy. Specifically, Sentinel-2 data has a significant impact cropland SOM prediction in hilly and mountainous areas, followed by Landsat-8 data. (3) The predicted spatial distribution patterns of cropland SOM by the four models show consistency, indicating lower SOM content in the southwest and higher SOM content in the central and northeast regions. This study provides valuable references for future large-scale and high-spatial cropland SOM prediction, highlighting the importance of spatial resolution for precise SOM prediction accuracy in hilly and mountainous regions.

Enhanced seasonality of the East Asian monsoon indicated by prevailing hydroxy-interlayered vermiculite formation since 1.8 Ma

The seasonality of the East Asian monsoon is characterized by the coexistence of warm and humid summers and cold and dry winters. However, the current understanding of when and why the seasonality of the East Asian monsoon occurs is poor. Hydroxy-interlayered vermiculite (HIV), which is formed under conditions of low soil organic matter content, pH values between 4.6 and 5.8, and oxidizing states with frequent wetting‒drying cycles, may serve as a potential indicator of monsoon seasonality variation. In this study, we present detailed mineralogical and micromorphological investigations of HIV collected from an eolian sequence on the Chinese Loess Plateau (CLP) to explore the evolution of East Asian monsoon seasonality. The mineralogical results deduced from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy show that a transition from chlorite to HIV occurred at ∼1.8 Ma. Moreover, the authigenic origin of HIV, as indicated by the presence of many neatly arranged flakes in the SEM images and the presence of irregularly interstratified chlorite-HIV observed via transmission electron microscopy (TEM), collectively imply that HIV is the weathering product of chlorite. This transition from chlorite to HIV generally reflects an increase in monsoon seasonality on the CLP since ∼1.8 Ma, which may be caused by the contemporaneous uplift of the northeastern Tibetan Plateau, or global cooling in combination with La Niña-like sea-air interactions. Our study suggests that the HIV serves as an effective index for monsoon seasonality reconstruction, thus providing a new insight into Asian monsoon dynamics.

Vermicompost and millicompost as a resource in sustainable agriculture in semiarid: decomposition, nutrient release, and microstructure under the action of nitrogen and organic-mineral fertilizers.

With the expansion of organic agriculture, research is needed to indicate economically and ecologically viable fertilizer options, especially in semiarid regions, with low soil organic matter and nitrogen content. In the Brazilian semiarid region, vermicomposts are widely used by farmers and are scientifically investigated; however, there is no information for millicompost, a new type of organic compound that has shown very promising results in other regions. Thus, this study aimed to analyze the decomposition rate, nutrient release, and microstructure evaluation of vermicomposts from different sources and of millicompost produced from plant residues, with the application of mineral nitrogen-urea and organo-mineral fertilizer in the Brazilian semiarid region. The experimental design was a randomized block in a 4 × 3 factorial scheme, with four replicates; four organic composts (millicompost, commercial vermicompost, vermicompost from bovine manure, vermicompost from goat manure); and three types of fertilization (without fertilizer, with mineral-urea and organo-mineral fertilizer). The organic composts were decomposed using litterbags at the soil surface. The variable's decomposition rate and the nutrient release were evaluated at six-time intervals (0, 30, 60, 90, 120, and 150days), and microstructure was evaluated at the beginning and the end of the experiment, with scanning electron microscopy (SEM). The highest decomposition was verified for commercial vermicompost rich in macro and micronutrients and with lower P contents. The lignin:N ratio and the initial P content were more important in the permanence of the organic compost in the field than the C:N ratio. Regardless of the organic composts, the use of urea as a mineral fertilizer stimulated decomposition more than the organo-mineral fertilizer. The initial composition of the nutrients was decisive in the dynamics of nutrient release, mass loss, and decomposition of C. There was no pattern in the release order of macronutrients. However, for the micronutrients, the release order was Cu > Fe > Mn, in all treatments. Microstructure analysis is a visual analysis where differences are detected through microphotographs and the biggest difference occurred with millicompost, which showed elongated fibers and fiber bundles, forming a relatively open structure characteristic of the presence of fulvic acid. However, the addition of organo-mineral fertilizer formed agglomerates in compacted micro-portions, helping the mineralization of C and N.

Peroxydisulfate-Driven Reductive Dechlorination as Affected by Soil Constituents: Free Radical Formation and Conversion.

We report a previously unrecognized but efficient reductive degradation pathway in peroxydisulfate (PDS)-driven soil remediation. With supplements of naturally occurring low-molecular-weight organic acids (LMWOAs) in anaerobic biochar-activated PDS systems, degradation rates of 12 γ-hexachlorocyclohexanes (HCH)-spiked soils boosted from 40% without LMWOAs to a maximum of 99% with 1 mM malic acid. Structural analysis revealed that an increase in α-hydroxyl groups and a diminution in pKa1 values of LMWOAs facilitated the formation of reductive carboxyl anion radicals (COO•-) via electrophilic attack by SO4•-/•OH. Furthermore, degradation kinetics were strongly correlated with soil organic matter (SOM) contents than iron minerals. Combining a newly developed in situ fluorescence detector of reductive radicals with quenching experiments, we showed that for soils with high, medium, and low SOM contents, dominant reactive species switched from singlet oxygen/semiquinone radicals to SO4•-/•OH and then to COO•- (contribution increased from 30.8 to 66.7%), yielding superior HCH degradation. Validation experiments using SOM model compounds highlighted critical roles of redox-active moieties, such as phenolic - OH and quinones, in radical formation and conversion. Our study provides insights into environmental behaviors related to radical activation of persulfate in a broader soil horizon and inspiration for more advanced reduction technologies.

Review of the Responses of Various Soil Amendments in Sandy Soils

The primary constraints with sandy soils are low soil organic matter content, poor nutrient availability, heavy losses of applied nutrients and lower water holding capacity. Improving the productivity of sandy soils, particularly in developing countries, could be a viable solution to food insecurity and poverty. Large extent of sandy soil is one of the major constraints for crop production in the Eastern Province of Sri Lanka. Meanwhile, various soil amendments can be applied to improve the performances of cropping systems in sandy soils. Nevertheless, a comprehensive knowledge on which soil amendment would work better across different scales is not well known. To address this knowledge gap, this review was conducted using published literature. Systematic review approach was adopted, and the data were extracted from 65 highly relevant papers. The data were analyzed to calculate the percentage changes on crop yields, soil organic matter and soil carbon, in response to the applications of different soil amendments. The review highlighted the potential of several soil amendments to improve the crop performances in sandy soils. Interestingly, rice straw biochar and the municipal solid waste compost have greatly increased crop yields especially in rice at the rate of 0.9% w/w and 3% w/w in soil weight basis, respectively. Highest improvement in soil organic matter and soil carbon was observed under the applications of compost and spent grain, respectively. Therefore, rice straw biochar and compost could be evaluated to improve the productivity of sandy soils, especially in the Eastern region of Sri Lanka. Although the spent grain was promising, the availability for large scale applications may be limited in Sri Lanka. Testing of these soil amendments would require long-term experiments incorporating different crops and cropping systems. 
 Keywords: Compost, Biochar, Sandy soil, Soil amendments

Methodology for Regional Soil Organic Matter Prediction with Spectroscopy: Optimal Sample Grouping, Input Variables, and Prediction Model

Soil organic matter (SOM) is an essential component of soil and is crucial for increasing agricultural production and soil fertility. The combination of hyperspectral remote sensing and deep learning can be used to predict the SOM content efficiently, rapidly, and cost-effectively on various scales. However, determining the optimal groups, inputs, and models for reducing the spatial heterogeneity of soil nutrients in large regions and to improve the accuracy of SOM prediction remains a challenge. Hyperspectral reflectance data from 1477 surface soil samples in Northeast China were utilized to evaluate three grouping methods (no groups (NG), traditional grouping (TG), and spectral grouping (SG)) and four inputs (raw reflectance (RR), continuum removal (CR), fractional-order differentiation (FOD), and spectral characteristic parameters (SCPs)). The SOM prediction accuracies of random forest (RF), convolutional neural network (CNN), and long short-term memory (LSTM) models were assessed. The results were as follows: (1) The highest accuracy was achieved using SG, SCPs, and the LSTM model, with a coefficient of determination (R2) of 0.82 and a root mean squared error (RMSE) of 0.69%. (2) The LSTM model exhibited the highest accuracy in SOM prediction (R2 = 0.82, RMSE = 0.89%), followed by the CNN model (R2 = 0.72, RMSE = 0.85%) and the RF model (R2 = 0.69, RMSE = 0.91%). (3) The SG provided higher SOM prediction accuracy than TG and NG. (4) The SCP-based prediction results were significantly better than those of the other inputs. The R2 of the SCP-based model was 0.27 higher and the RMSE was 0.40% lower than that of the RR-based model with NG. In addition, the LSTM model had higher prediction errors at low (0–2%) and high (8–10%) SOM contents, whereas the error was minimal at intermediate SOM contents (2–8%). The study results provide guidance for selecting grouping methods and approaches to improve the prediction accuracy of the SOM content and reduce the spatial heterogeneity of the SOM content in large regions.

Investigation of Soil Properties Effect on Crop Yield Performance

Soil nutrient is essential for crop growth. Spatial variability of nutrients will have occurred in numerous scales, between regions, a field, particularly in soil properties. A study was carried out to observe the yield performance in an agricultural plot at Semujuk Jasin, Melaka. Using management zone delineation, the area is divided into fifteen smaller 6.8-meter × 6.8-meter plots. A soil sample from each plot was tested in the laboratory to obtain the soil moisture, organic matter, pH level, Phosphorus, and Manganese content. Using ArcGIS software, the result is interpolated using the Kringging method, mapped, and then compared with the crop value from each. Plot A3 generated the lowest yield with a crop yield value of RM6.8. This plot also has the lowest soil moisture content, which is 6.452%. Plot A1 produces only RM65.2 for crop yield, although it has 21.505% soil moisture content, while plot C1 only produces RM47.4 for crop yield value, although it has a higher soil moisture content of 23.265%. Regarding the soil organic matter content for both plots, plot A1 has only 1.455% organic matter content, while plot C1 has lower soil organic matter content, which is 0.823%. Plot B2, with a low pH value (4.51), shows a poor performance of RM52.6 regarding satisfactory readings on other plots. From the analysis made based on the experiment result, the primary limiting factor affecting crop performance is soil moisture content. Soil pH value and Organic Matter also play an essential role in determining crop performance.

Gliricidia intercropping supports soil organic matter stabilization at Makoka Research Station, Malawi

Intercropping agriculture with legume trees is a promising strategy to improve soils with low soil organic matter (SOM) and nitrogen (N) contents, which is a common problem in many Southern African regions. Objective of this research was to explore long-term effects of legume-intercropping on SOM pools and soil fertility. We examined a maize-based cropping system with gliricidia (Gliricidia sepium) as intercropping legume tree on a Ferric Lixisol in Southern Malawi. The experimental trial at Makoka Research Station was in its 29th year of management with leaf biomass incorporated into the soil regularly. We determined concentrations of organic carbon (C) and N, exchangeable cations, and available phosphorus (P) of topsoil samples (0–20 cm). We used density fractionation of SOM to gain fractions that roughly approximate SOM pools with fast turnover (not associated to soil minerals), intermediate turnover (occluded within soil aggregates) and slow turnover (mineral associated SOM). We further determined water dispersible clay (WDC) and pedogenic oxides, as these are often involved in the C-stabilization process in tropical soils. Maize-gliricidia intercropping plots showed higher soil pH-values, and higher concentrations of exchangeable Mg and Ca than plots with maize monoculture. In addition, significantly higher contents of C (17.3 vs. 7.03 g kg−1) and N (1.51 vs. 0.7 g kg−1) were found at intercropping plots indicating a C-sequestration rate of 0.3 g C kg−1 a−1, while monoculture induced the loss of SOM with a rate of −0.1 g C kg−1 a−1. C and N contents doubled in pools with fast and with slow turnover and increased by >300% in SOM pool where C and N is bound in soil aggregates. Concomitantly, WDC was significantly lower in intercropping plots than in monoculture plots. Our data emphasize the fast turnover of SOM in subtropical soils and indicate that SOM in arable soils decreases continuously without suitable C-input strategy. Maize-gliricidia intercropping had positive effects on biomass production and C-input at Makoka Research Station and improved soil fertility. In addition, aggregate formation was enhanced and storage of SOM within aggregates and at mineral surfaces increased. Our results indicate a great potential of maize-gliricidia intercropping for improved C management in subtropical Lixisols. Intensive monitoring seems to be promising to validate and quantify the impacts of this measure.

Effects of soil amendments on soil acidity and crop yields in acidic soils: A world-wide meta-analysis

Soil amendments, including lime, biochar, industrial by-products, manure, and straw are used to alleviate soil acidification and improve crop productivity. Quantitative insight in the effect of these amendments on soil pH is limited, hampering their appropriate use. Until now, there is no comprehensive evaluation of the effects of soil amendments on soil acidity and yield, accounting for differences in soil properties. We synthesized 832 observations from 142 papers to explore the impact of these amendments on crop yield, soil pH and soil properties, focusing on acidic soils with a pH value below 6.5. Application of lime, biochar, by-products, manure, straw and combinations of them significantly increased soil pH by 15%, 12%, 15%, 13%, 5% and 17%, and increased crop yield by 29%, 57%, 50%, 55%, 9%, and 52%, respectively. The increase of soil pH was positively correlated with the increase in crop yield, but the relationship varied among crop types. The most substantial increases in soil pH and yield in response to soil amendments were found under long-term applications (>6 year) in strongly acidic (pH < 5.0) sandy soils with a low cation exchange capacity (CEC, <100 mmolc kg−1) and low soil organic matter content (SOM, <12 g kg−1). Most amendments increased soil CEC, SOM and base saturation (BS) and decreased soil bulk density (BD), but lime application increased soil BD (1%) induced by soil compaction. Soil pH and yield were positively correlated with CEC, SOM and BS, while yield declined when soils became compacted. Considering the impact of the amendments on soil pH, soil properties and crop yield as well as their costs, the addition of lime, manure and straw seem most appropriate in acidic soils with an initial pH range from <5.0, 5.0–6.0 and 6.0–6.5, respectively.

Factors affecting soil quality among smallholder macadamia farms in Malawi

Declining soil fertility limits smallholder macadamia productivity in Malawi. To reverse this trend, it is essential to apply organic and inorganic fertilisers in an efficient and effective manner. Yet, fertilizer recommendations for smallholder macadamia (Macadamia integrifolia) production in Malawi are not site-specific. Nutrient imbalances can occur if fertilisers are applied without a clear understanding of whether they are required or not. This may lead to yield losses, unnecessary costs, and other environmental issues associated with excess fertiliser application. To address this research need/ knowledge gap, our study examined the current soil fertility status among smallholder macadamia farms in Malawi. Specifically, the objective was to establish an evidence base for promoting soil fertility restoration interventions for smallholder macadamia production. One hundred and eighty nine soil samples at a depth of 0–15 cm were collected from sixty three smallholder macadamia farms belonging to the Highlands Macadamia Cooperative Union Limited members in central and southern Malawi. We found that the majority of the soils were sandy loams (52%), strongly acidic (mean pH ≤ 5.1), and deficient in essential nutrients required for the healthy growth of macadamia. The soils had an average low cation exchange capacity of 1.67 cmol ( +) kg−1, which is inadequate for macadamia cultivation. More than half of the sampled soils had very low organic matter content (≤ 1%). The low soil organic matter content, coupled with the sandy texture and high acidity, contributed to the observed low concentrations of essential nutrients and cation exchange capacity. Poor agronomic practices and inherent soil characteristics are responsible for this low soil fertility. Altogether, our findings underscore the urgent need to identify and implement more sustainable and effective soil nutrient management practices that help to improve the soil fertility of macadamia farms under smallholder systems.

Disentangling drivers of soil organic carbon storage in deltaic rice paddies from the Ebro Delta

Paddy farming can potentially sequester carbon. However, agricultural practices may alter the stability of the soil organic carbon (SOC) stocks and thereby increase carbon mobilization in the topsoil and subsoil. We hypothesize that both agricultural practices and soil physical–chemical characteristics, mostly those related to the type of the parental soil where the paddy is established, play an important role in SOC stabilization and sequestration. To test this, we profiled the biochemical characteristics of soil organic matter (SOM) and the SOC concentrations in sediment cores of 10 rice fields from the Ebro Delta (Northeast Spain) representing former reclaimed habitats (i.e., peatlands, meadows, coastal lagoons, riverbanks and salt marshes). The effects of physical–chemical soil properties on SOM content were tested with Generalized Linear Models and the best models were selected using information-theoretic approach. The optical characteristics of SOM extracts were analyzed by UV–Visible and fluorescence spectrophotometry, and six fluorescence components were identified by Parallel Factor Analysis (PARAFAC). Higher clay and lower sand content explained the greater SOM presence in topsoil while higher clay content and salinity prevailed as the main explanatory factors in the subsoil showing a positive correlation with SOM content. The results revealed a correlated gradient of SOM quantity and quality where in SOM-rich soils both the aromaticity and the humification degree were higher while in soils with lower SOM content it was fresher and more microbially derived. Current agricultural practices favored SOM humification in the topsoil while the variability in SOM quality in subsoil is attributed to the combination of soil physical–chemical characteristics (pH, conductivity and clay content) and the previous habitat’s influence. This study represents a comprehensive empirical analysis on the carbon stocks in rice fields and the identification of soil physical–chemical factors, related to prior land uses, favoring soil carbon accumulation. These results may have major implications in decision-making process for climate change mitigation in vulnerable Mediterranean coastal paddies.

Role of Rice Husk Biochar in Improving Soil Physical Properties of ex Gold-Mined Soil

Mining causes destructive soil properties, especially soil texture, water retention, and transmission. Applying biochar is the best way to improve soil physical properties. A glasshouse experiment was conducted to evaluate the role of biochar on soil physical properties based on a Completely Randomized Design (CRD) with four replicates. The research comprised six treatments (0, 4, 8, 12, 16, 20 t biochar ha-1). The results showed that the ex-gold-mined soil had coarse soil texture (sandy loam), high Bulk Density (BD) (1.43 g cm-3), low Total Soil Pores (TSP) (46.45%), low soil organic matter (SOM) content (1.27 %), very fast hydraulic conductivity (198.8 cm h-1). After biochar incubation, SOM increased (to 3.11%), soil BD decreased (to 1.16 g cm-3), TSP increased (to 54.17 %), water retention increased (at pF 1.0, 2.0, 2.54, and 4.2), plant available water (PAW) increased (into 8.33 %), and hydraulic conductivity decreased (into 24.70 cm h-1). However, applying 20 t biochar ha-1 still needs to bring the soil physical properties of the ex-gold-mined soil back into suitable soil for farming land.

Urbanization associated changes in biogeochemical cycles.

Urbanization associated changes in biogeochemical cycles.

Identification of factors controlling heavy metals/metalloid distribution in agricultural soils using multi-source data

Understanding the factors that controlling the agricultural soil heavy metals/metalloids distribution is vital for cropland soil remediation and management. For this objective, 227 agricultural soils were sampled in the Guanzhong Plain, China, to measure the concentration of five heavy metals (Pb, Cd, Ni, Zn, and Cu) and one metalloid (As) by X-ray fluorescence spectrometer, meanwhile, 24 possible influencing factors to agricultural soil heavy metals/metalloid distribution were collected and grouped into three categories. A sequential multivariate statistical analysis was carried out to provide insight into the controlling factors of soil heavy metals/metalloid distribution, then stepwise multiple linear regression (SMLR) and partial least squares regression (PLS) were used to predict heavy metals/metalloid concentrations in agricultural soil based on the result of soil heavy metals/metalloid controlling factors identification. The results demonstrated the types of soil and land use did not have a substantial effect on soil heavy metals/metalloid distribution, except Zn and Cu. The soil properties category played a major role in influencing the soil heavy metals/metalloid concentration. The concentrations of Mn and Fe, which are the main constitute elements of soil inorganic colloid, were the most significant factors, followed by the concentrations of P, K and Ca. Soil pH and soil organic matter (SOM) content, which are often considered as important factors for soil heavy metals/metalloid distribution, were not important in the present study. The SMLR was more effective than the PLS for predicting soil heavy metals/metalloid content. The results of this study enlighten that future soil heavy metals/metalloid contamination treatment in regions with high pH and low SOM content should concentrate on inorganic colloid particles, which have strong adsorption capacity for soil heavy metals/metalloid and are environmentally friendly. Moreover, the combination of successive multivariate statistical analysis and SMLR provide an effective tool to predict and monitor agricultural soil heavy metals/metalloid distribution, and facilitate the improvement of environmental and territorial management.

Integrated use of organic amendments increased mungbean (Vigna radiata (L.) Wilczek) yield and its components compared to inorganic fertilizers

AbstractRainfall variability, low soil organic matter content, and costly inorganic fertilizers are the major agricultural constraints in Sub‐Saharan Africa. Integrated use of compost and manure is essential for sustaining soil fertility and increasing crop productivity. This study was conducted to evaluate the combined effects of compost and animal manure on mungbean growth and yield. The 12 treatments consisted of control, recommended dose of nitrogen, phosphorus, and potassium (NPK), 5 ton ha−1 of compost, 10 ton ha−1 of poultry, 10 ton ha−1 of cattle, and 10 ton ha−1 of sheep manure, and six combinations of organic amendments with 50% of their applied rate alone. These treatments were laid out in a randomized complete block design with six replications. Application of cattle manure at 10 ton ha−1 significantly increased mungbean seed yield by 66% and 84% compared to the recommended rate of NPK and control treatments, respectively. Similar observations were made on stem diameter, total pod weight, and number of seeds per pod. Plants amended with compost had the highest number of ramifications and number of pods than NPK fertilized plants, which recorded (9±) ramifications and (27±) pods per plant. On average, integrated use of 5 ton ha−1 of poultry manure + 5 ton ha−1 of cattle manure had the highest soil plant analysis development values, though not significantly different from NPK fertilizers. These results suggest that application of organic amendments could be an alternative to costly and inaccessible inorganic fertilizers for improving mungbean productivity under low‐input agriculture systems.

Amelioration of dry land suboptimal using biochar and compost to improve soil physical properties and soybean yield

The primary constraint of suboptimal soils under wet tropical regions, besides their low pH, is their low soil organic matter (SOM) content. This research aimed to improve the soil properties of dry land suboptimal and the yield of soybeans by applying biochar and compost. This research was carried out to investigate the effects of coconut shell biochar (B) and Leucaena compost (C) applied alone (at a rate of 10 ton.ha-1) or in combination (5 B: 10 C; 10 B: 15 C each. thus 10 1 B: 10 C) on soil physicochemical properties, growth, and yield of Soybean on Ultisols in Jambi Province. Biochar and compost applied alone or in combination significantly increased soil organic matter (SOM), total porosity (TP), and Aeration Pore (AP); decreased bulk density (BD) and low drainage pore (LDP). Also, combined application and single application biochar or compost to impact beneficially on soil water retention and available water (AW). Additionally, combined application and single application biochar or compost additions increased components of yield as a number of pods of soybean. The study showed that biochar applied alone or in combination with compost offers the potential to enhance soil quality and improve soybean yield.