Carbon Content Research Articles

Sugarcane biomass-derived biochar for soil quality enhancement in sugarcane-growing soil

This study explored the barrel technique for biochar production, comparing it with laboratory-prepared biochar by evaluating the effect on sugarcane-growing soil quality. Different sugarcane biomass (bagasse, trash, and mini mill waste) derived biochar was prepared using a muffle furnace at three different temperatures (300, 450, and 600 °C) and with the barrel technique. Biochar was characterized by yield, pH, electrical conductivity (EC), proximate and ultimate analysis, scanning electron microscopy (SEM) analysis, and Fourier-transform infrared spectroscopy (FT-IR) characterization. A pot experiment was conducted with soil amendments with biochar (bagasse biochar pyrolyzed at 450 °C–BBC-450 and bagasse biochar prepared from barrel technique–BBC-BT) at a 2.5% (w/w) rate. The initial, 45-day, and 90-day soil samples were analyzed by selected soil chemical and physical parameters. The soil quality index of the 90-day soil samples was determined. Sugarcane biomass-derived biochar was rich in carbon content (64.68%–85.43%). Biochar amendment led to significant enhancements in soil pH, EC, organic carbon (OC), water holding capacity, total N, available P and Zn, and exchangeable K, Ca, and Mg. The results of the 90-day soil samples indicated an increase in soil OC by 1.22% due to both biochar amendments relative to the controls. Available P increased by 2.59% in BBC-BT amended soil and by 23.05% in BBC-450 amended soil. The EC increment due to soil amendments with BBC-BT and BBC-450 was 33.33% and 16.67%, respectively, in the 90-day soil samples. The highest soil quality index was observed in BBC-BT. It can be concluded that BBC-BT enhances the soil quality of sugarcane-growing soil, and the barrel technique could serve as a viable option for small-scale farmers and for domestic use in producing biochar.Graphical

Boron Behaviors in Upland Humid Tropical Soils: A Case of Plant-Available Implication for Cassava

ABSTRACT Understanding the role of soil boron (B) through its reaction, mobility, and availability could provide effective B nutritional management for a cassava crop (Manihot esculenta crantz). This study investigated a soil B status suitable method for making B fertilizer recommendation through determining the B sorption index and the chemical fractionation of soil B and available B in soils, using single extractants in 11 benchmark soils intensively cultivated for cassava in northeast, Thailand. All soils studied were considered low B-sorbed soils that were equally well described using either Langmuir or Freundlich models, with respective adsorption capacities of 2.00–17.22 mg kg−1 and 0.91–4.31 L mg−1. The B desorption index exhibited hysteresis desorption behavior for all soils. Boron adsorption by the soils significantly showed a positive correlation (>0.75, p ≤ .01) with organic carbon, silt, amorphous aluminum, and silicon contents. Of the total B, the native B pool in the soils was mostly in the residual fraction, contributing 70–80%, while the readily soluble fraction contributed only 0.07–0.59%. Among the soil extractants tested, only hot CaCl2 and NH4OAc adequately assessed soil B availability for cassava, while they were less extractability to extract B from total B. Chemical fractions of B could all be used for available B assessment for cassava with a residual B fraction being superior, although this was unlikely to contribute significantly to plant-available B in the short term, but it was a potential B reserve that could maintain adequate B status in the long term throughout the cassava growing period.

The microbial mechanism of maize residue decomposition under different temperature and moisture regimes in a Solonchak

Soil salinization becomes serious under climate change and human activities. Although the residue decomposition contributes lots to soil carbon storage and fertility, the decomposition process and microbial mechanisms on saline-alkali soils are still vague facing climate change. We measured the mass loss of residue (0, 4, 8, 15, 30, 60 and 90 days), CO2 emission (every two days), and the microbial community structure (0, 4, 15 and 90 days) by using the litter bag method, gas chromatography and high-throughput sequencing technology during the residue decomposition (90 days) in a saline-alkali soil from the Tarim River Basin, China under various temperatures (15 °C, 25 °C, 35 °C) and soil moisture levels (20%, 40%, 60% water holding capacity). The decomposition stage consisted of fast (0–15 days) and slow periods (15–90 days). Using the double exponential equation, the decomposition rates of labile and recalcitrant components, the labile component and cumulative CO2 emissions increased faster with increased moisture than with temperature. The Q10 was greater at 15–25 °C than at 25–35 °C, which increased with the increased soil moisture in the leaf but with decreased soil moisture in the stem at 15–25 °C. Proteobacteria increased from 0 to 15 days on leaves (25–43%) and stems (25–29%) and showed no changes thereafter. Proteobacteria increased with increased soil moisture but decreased temperature. Actinomycetes was the opposite and more abundant on the stem than on the leaf. Bacteroidetes increased after 15 days and increased with increased soil moisture. Firmicutes were the main bacterial groups at 0–15 days, but decreased at 15–90 days (leaf: 44 − 15%, stem: 49 − 13%). In conclusion, warming, especially 15–25 °C, contributes to the decomposition of stems and wetting, especially 20-40% WHC, contributes to that of leaves within the first 15 days, afterwards wetting played an important role. Our results could also provide the adopting strategies for residue return to increase the soil carbon content while decreasing CO2 emissions facing climate change.

Endpoint carbon content and temperature prediction model in BOF steelmaking based on posterior probability and intra-cluster feature weight online dynamic feature selection

Abstract A posterior probability and intra-cluster feature weight online dynamic feature selection algorithm is proposed to address the issues of high dimensionality and high volatility of data in the basic oxygen furnace (BOF) steelmaking production process. First, a genetic algorithm with fixed feature space dimensions is introduced, which narrows the solution space by predefining the number of selected features, thereby enhancing the stability of feature selection. Second, the posterior probability of samples and intra-cluster feature weights are used to weigh and calculate the feature importance of the current sample, obtaining the optimal features that align with the current operating conditions. Finally, the dynamically selected features are used in a regression model to predict the carbon content and temperature of the BOF steelmaking process data. Simulations of actual BOF steelmaking process data showed that the prediction accuracy was 86% within a carbon content error range of 0.02, and 88% within a temperature error range of 10°C.

Assessing biochar's impact on greenhouse gas emissions, microbial biomass, and enzyme activities in agricultural soils through meta-analysis and machine learning.

The role of biochar in reducing greenhouse gas (GHG) emissions and improving soil health is a topic of extensive research, yet its effects remain debated. Conflicting evidence exists regarding biochar's impact on soil microbial-mediated emissions with respect to different GHGs. This study systematically examines these divergent perspectives, aiming to investigate biochar's influence on GHG emissions and soil health in agricultural soils. The meta-analysis includes 2594 paired observations from 157 studies conducted between 2000 and 2024. It was found that biochar increased the presence of amoA and nosZ genes by 39.4% and 41.7%, respectively, while reducing the abundance of the nirS gene by 17.8%. This led to a 13.1% decrease in N2O emissions. Nitrous emissions were positively associated with mean annual temperature and biochar's pyrolysis temperature and dosage while inversely related to soil pH, nitrogen fertilisation rate, and biochar pH and carbon content. Biochar also regulated enzyme activity related to the nutrient cycle and increased microbial biomass carbon, nitrogen, and phosphorus by 16.6%, 23.9%, and 50.2%, respectively, leading to changes in microbial community diversity. These changes contributed to a reduction in CO2 and CH4 emissions, particularly when biochar and nitrogen fertiliser were applied at doses below 21.4tha-1 and 242.5kgha-1, as predicted by machine learning models. This study offers an overview of the positive impact of biochar amendments on soil GHG emissions mitigation. The key predictive factors identified could help optimise biochar production and targeted amendments, potentially improving soil health and achieving carbon neutrality in agroecosystems.

Time and climate roles in driving soil carbon distribution and stability in particulate and mineral-associated organic matter pools.

Understanding the accumulation and stability of soil organic matter (SOM) pools as a function of time (i.e., soil age) and climate (i.e., precipitation and temperature) represents a crucial challenge. This study aims at investigating the effect of both climate and time on SOM distribution into particulate and mineral-associated organic matter (POM and MAOM, respectively), using two chronosequences located along a climate gradient. The contribution of POM and MAOM to soil organic carbon (SOC) storage differs between the climo-chronosequences and with depth. The ratio between MAOM and POM pools (MAOM/POM) ranges from 0.9 to 2.0 and from 1.4 to 3.5 in the wetter and cooler and in the drier and warmer chronosequence, respectively. Regardless of the chronosequence, the MAOM/POM ratio increases with depth, highlighting a more important role of the mineral-associated fraction in carbon storage in deeper soils. The concentration of organic carbon in mineral-associated (MAOC) and particulate (POC) pools along the soil profile in the wetter and cooler chronosequence is 2× and 3× higher, respectively, than in soils from the drier and warmer one. In particular, in the wetter and cooler chronosequence, MAOC and POC concentrations decrease with soil age. In the drier and warmer chronosequence, only POC concentration decreases with soil age, whereas MAOC concentration generally increases. The thermal stability of the MAOM fraction increases with soil age and depth only in the drier and warmer climatic conditions, whereas no differences with depth occur in the wetter and cooler chronosequence. Furthermore, the MAOM energy density decreases with soil depth and age in both chronosequences. Independently of the chronosequence, POM represents the most labile pool with higher energy density. In conclusion, time and climate play a different role in SOC distribution between the pools and on their relative stability. Soil age drives MAOM stability in drier and warmer conditions, whereas a wetter and cooler climate determines a higher SOC accumulation in both pools, although these greater carbon stocks are negatively correlated with their stability.

Nanoscale Pore Evolution of Terrestrial Shale with Thermal Maturation Level Increase Induced by Hydrous Pyrolysis

A series of terrestrial shale samples with different thermal maturities were subjected to hydrous artificial pyrolysis to study the evolution of terrestrial shale pores. The original shale was obtained from the terrestrial interval of a core sample, the total organic carbon (TOC) content was 8.34 wt%, and the vitrinite reflectance (Ro) was 5.31%. The original shale core was cut into eight parts, which were heated at temperatures of 300, 350, 400, 420, 450, 500, 550, and 600 °C to obtain samples with different thermal maturities. The pore size distribution (PSD), pore volume (PV), specific surface area (SSA), and pore types were investigated via CO2 and N2 adsorption tests and field emission scanning electron microscopy (FE-SEM). Many organic matter (OM) pores and mineral pores were observed via FE-SEM with increasing thermal maturity. The total PV and SSA increased until the sample reached 500 °C and then decreased, and the mesopore volume followed this trend. The micropore volume first decreased, increased until the sample reached 500 °C, and then decreased; the macropore volume increased to a peak in the sample pyrolyzed at 420 °C and then remained stable. Pores with sizes ranging from 10 to 30 nm were the predominant contributors to the shale pore volume. The SSA was affected by pores with diameters less than 20 nm, which accounted for approximately 54% of the SSA. The rate of OM conversion influenced pore creation.

Boron fertilization in a boreal Norway spruce forest: long-lasting effects on growth and nutrition

Abstract Background and aims Boron (B) deficiency is widespread in boreal forests, but it can be prevented by fertilization. As B deficiency reduces root growth, it may affect the uptake of other nutrients. We assessed the persistence of the effects of a one-time B application on growth and nutrition of Norway spruce (Picea abies). Methods A single-tree B-fertilization experiment was established in a highly productive stand in eastern Finland in 2000 and followed until 2018. The applied B dose was 2 kg ha−1. Results After 19 growing seasons, height growth was higher in B-fertilized trees and the effect was not waning. Diameter growth was not affected. The mean needle-B concentration without B fertilizer was 1.7 mg kg−1 and with B-fertilizer, 4.8 mg kg−1. Boron-fertilized trees had higher foliar aluminium (Al), carbon (C), copper (Cu) and sulfur (S) concentrations, and lower soluble silicon (Si). Conclusions The positive B effect on growth persisted after 19 years. Boron concentrations remained higher in fertilized trees, although lower than at the early stages of the experiment. Boron fertilization maintained Cu and S levels above deficiency limits. The small but consistent change in C indicates a change in needle compounds. Increased Al may result from reduced Si accumulation, as Al co-deposition with Si alleviates Al toxicity. Further studies are required to optimize B-fertilization practices and to elucidate the mechanisms behind the effects on height growth and the levels of other elements. A combination of soluble and sparingly soluble fertilizers could further increase the duration of the effect.

Changes in leaf functional traits of Phoebe chekiangensis underplanted in moso bamboo forests with different densities

Leaf functional traits are sensitive to environmental changes, and are a current hotspot in ecology. The objective of this study was to explore the changes in leaf functional traits of Phoebe chekiangensis underplanted in moso bamboo forests with different densities. Leaf functional traits of Phoebe chekiangensis were determined, and their relationships were also investigated. Results showed that leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC) increased with the increase of bamboo forest density, while leaf thickness (LT), leaf mass per unit area (LMA), and leaf tissue density (LTD) decreased. Chlorophyll a (Ca) concentration decreased with the increase of bamboo forest density, while chlorophyll b (Cb), total chlorophyll (Ca+Cb), and total carotenoids (Car) concentrations increased. Ca/Cb decreased, while Car/(Ca+Cb) remained unchanged. Leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations increased with the increase of bamboo forest density. However, C/N decreased, and it was significantly higher at 1350 ind·ha−1 than that of 2250 ind·ha−1. Significant correlations among some leaf functional traits were found. In conclusion, leaf functional traits of Phoebe chekiangensis could make up for the deficiency of light through certain trait variations and trait combinations, and better adapt to the environment.

Biochar and bentonite application improves aeolian sandy soil health and enhances soil carbon sequestration and emission reduction potential

Aeolian sandy soil is barren and readily leads to low fertilizer utilization rates and yields. Therefore, it is imperative to improve the water and fertilizer retention capacity of these soils. In this paper, three kinds of biochar (rice husk, corn stalk, and bamboo charcoal) and bentonite were used as amendments in the first year of the experiment. In the second year, only corn stalk biochar was applied. The effects of biochar and bentonite on the physicochemical and biological characteristics of aeolian sandy soil and corn agronomic traits were studied through a 2-year field experiment, and the carbon sequestration and emission reduction potential of biochar in aeolian sandy soil were explored. The results showed that the input of biochar and bentonite effectively improved water content and reduced soil bulk density. Compared with the same treatment in the first year, the content of water-stable aggregates with particle sizes greater than 0.25 mm, mean weight diameter and geometric mean diameter of the corn stalk biochar mixed with bentonite treatment significantly increased in the second year. Biochar and bentonite significantly increased the soil organic matter content, pH, cation exchange capacity (CEC) and available nitrogen, phosphorus and potassium contents, and CEC increased by 150.4%. Soil available phosphorus increased 2.6 times compared with that of the fertilizer treatment. Soil alkali-hydrolyzable nitrogen content increased by 211.5%, respectively. The plant height, leaf area index and ground dry matter mass also increased significantly, and the corn yield increased by 36.6% in response to the mixed application of 1.9 t/hm2 corn stalk biochar and 12 t/hm2 bentonite. The contents of urease, sucrase and catalase increased first and then decreased with crop growth through the jointing, silking and maturity stages. The microbial carbon content increased 2.4 times in the second year when corn stalk biochar was applied compared with that in the first year. The carbon sequestration potential of biochar application was equivalent to offsetting CO2 emissions by approximately 100 million tons per year of the study.

The Promotion of Dark Septate Endophytes on the Performance and Active Ingredients Accumulation of Dendranthema morifolium Under Cd Stress

Dark septate endophytes (DSE) may facilitate plant growth and stress tolerance in stressful ecosystems. However, little is known about the response of medicinal plants to DSE, especially under heavy metal stress. This study aimed to investigate how DSE affects the growth of Dendranthema morifolium in medicinal plants under cadmium (Cd) stress. In this investigation, the sterile and non-sterile inoculations were carried out to evaluate the effect of three DSE strains on D. morifolium stressed with Cd. For the root, DSE15 sterile or non-sterile inoculation resulted in enhanced root biomass, root volume, the Cd content of roots, and the indoleacetic acid (IAA) levels in D. morifolium under Cd stress. DSE7 non-sterile inoculation significantly enhanced the Cd content of roots at 1 and 5 mg Cd/kg soil. Regarding impact stems and leaves, under sterile conditions, DSE7 and DSE15 effectively regulated the shoot biomass, plant height, chlorophyll level, and superoxide dismutase (SOD) content. Under sterile conditions, DSE15 positively influenced shoot biomass and plant height, while DSE7 had no significant effect on them when subjected to Cd stress. For effects on flowers under non-sterile conditions, DSE7 and DSE15 significantly increased the flower biomass under Cd stress, while DSE7 reduced the Cd transfer coefficient of flowers at 1 and 5 mg Cd/kg soil. Importantly, at 1 mg Cd/kg soil, DSE7 and DSE15 non-sterile inoculations promoted the 1, 5-dicaffeoylquinic acid content by 18.29% and 21.70%. The interaction between DSE and soil factors revealed that DSE species had significant effects on soil organic carbon and available nitrogen in D. morifolium non-sterile soil. The DSE15 inoculation enhanced soil organic carbon content, while the inoculation of DSE7 and DSE15 reduced soil available nitrogen content under Cd stress. These results contribute to a better understanding of DSE-plant interactions in habitats contaminated by heavy metals and demonstrate the potential utility of DSE strains for cultivating medicinal plants.

Zootechnical and Municipal Solid Waste Digestates: Effects on Soil Nitrogen Mineralization and Kinetics

Soil fertilization with fertilizers derived from renewable sources is a topic of great interest in terms of the sustainable management of organic waste. To optimize the management of nitrogen supplied to the soil with digestates, it is necessary to deepen knowledge on the process of mineralization of organic nitrogen over time. In this research, a laboratory incubation system was utilized to study the impact of various digestate sources on nitrogen mineralization processes in soils and nitrogen mineralization kinetics. Six types of digestates of different origins and composition were administered to soil and the soil samples were placed under controlled conditions. The release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during a 12-week period of incubation. The nonlinear regression technique was used to fit the cumulative leaching of total N to the Stanford and Smith first-order kinetic model during the incubation period. The results showed that the differences between digestates, nitrogen and organic carbon concentration, and C/N ratio influenced both ammonification and nitrification processes in the soil and the nitrogen mineralization kinetics. The processing of the statistical data highlighted that the potentially mineralizable nitrogen (MPN) followed first-order kinetics.

Pollution of the Main Components of the Natural Environment of the Most Developed Part of the Southwestern Coast of Lake Baikal (within the Baikal Municipal Formation)

The data of landscape-geochemical studies of the main components of the environment (snow, surface water, soils and vegetation) near the sedimentation ponds of the industrial site of the former Baikal pulp and paper mill, Baikalsk, at the mouth of the Kharlakta and Babkha rivers on the southwestern coast of Lake Baikal are presented. Increased content of heavy (HM) and alkaline-earth metals, SO42–, NO3–, NH4+, PO43– was detected in the snow near the Baikalsk town, exceeding background readings. Concentrations of F–, NO3–, NH4+, Pb, Mo, Mn, Zn, Sr and V in surface waters of local lake shore sites exceed sanitary and hygienic norms. Soil contamination with HM in the recreational and industrial zone located on the shore of Lake Baikal has been revealed. Correlations between the concentrations of macro- and microelements in soils and their indicators such as the content of organic carbon and physical clay fraction have been established, which indicates the presence of biogeochemical barriers on which Na, Ni, Cu, Zn, Sr, Co accumulate in values above the background readings and MAC.

Evaluation of Upper Paleozoic source rocks in the southeastern margin of the Ordos Basin

IntroductionThe Yanchang gas field in the southeastern Ordos Basin is an important region for natural gas exploration due to the presence of Upper Paleozoic coal-bearing source rocks. This study systematically evaluates these source rocks in terms of organic matter abundance, type, and thermal maturity to assess their hydrocarbon generation potential.MethodsOrganic geochemical analyses were performed to determine the total organic carbon (TOC) content, kerogen type, and thermal maturity of the source rocks. The Benxi and Taiyuan Formations were specifically targeted for detailed evaluation. Kerogen maceral analysis was used to classify organic matter types, while thermal maturity was assessed through vitrinite reflectance (Ro) values.ResultsThe results indicate that the Upper Paleozoic source rocks exhibit high TOC content, with the Benxi and Taiyuan Formations showing excellent hydrocarbon generation potential. Kerogen maceral analysis identified predominantly Type III (humic) kerogen with some Type II2 (humic-sapropelic) components, suggesting a strong capacity for gas generation. Thermal maturity analysis revealed that the source rocks have reached the overmature dry gas stage, signifying advanced thermal evolution.DiscussionThe findings highlight the central and southern parts of the Yanchang gas field as promising exploration targets, characterized by high TOC content, favorable kerogen type indices, and high Ro values. These features collectively demonstrate the significant hydrocarbon generation potential of the Upper Paleozoic source rocks.ConclusionThe Upper Paleozoic coal-bearing source rocks in the Yanchang gas field represent a highly prospective target for natural gas exploration, particularly in regions with favorable organic geochemical properties.

Tidal Effects on Dissolved Organic Matter Dynamics in a Brackish Water Front Adjacent to Yangtze River Estuary

A brackish water front, where river water meets seawater, is a hotspot for biogeochemical processes. In this study, we examined the quantity and composition of dissolved organic matter (DOM) over a 24 h tidal cycle at a brackish water front near the Yangtze River estuary. Utilizing elemental analysis, fluorescence and ultraviolet spectroscopy, and ultra-high-resolution mass spectrometry, we observed rapid fluctuations in DOM throughout the tidal cycle. The dissolved organic carbon (DOC) and total nitrogen (TN) concentrations ranged from 0.70 to 1.5 mg/L and 0.43 to 0.94 mg/L, respectively. Water samples during low tide exhibited a higher fractional abundance of CHON (17.2 ± 0.1% vs. 14.6 ± 0.4%), CHOS (14.6 ± 4.5% vs. 9.1 ± 3.1%), and CHONS (1.6 ± 0.5% vs. 0.5 ± 0.3%) formulas, and a higher aromatization and average molecular weight, which is consistent with a stronger terrestrial influence. In contrast, at high tide, the water samples contained a greater abundance of CHO compounds (75.7 ± 3.8% vs. 66.5 ± 4.1%), a humic-like fluorescent C1 component, and carboxyl-rich alicyclic molecules (CRAMs), indicating a greater release of refractory DOM from resuspended sediments. However, variations in the DOC concentrations and several optical spectral parameters did not correlate with the changes in the salinity and tidal height. The results of the principal component analysis revealed different controls on specific fractions of DOM that are related to variable DOM sources or biogeochemical processes. The complexity of DOM dynamics underscores the necessity of elucidating DOM compositions at varying levels to enhance our understanding of carbon cycling in estuarine and coastal ecosystems.

In Situ Characterization of Dust Storms and Their Snow‐Darkening Effect Over Himalayas

AbstractIn this study, we used satellite observations to identify 10 typical dust‐loading events over the Indian Himalayas. Next, the aerosol microphysical and optical properties during these identified dust storms are characterized using cotemporal in situ measurements over Mukteshwar, a representative site in Indian Himalayas. Relative to the background values, the mass of coarse particles (size range between 2.5 and 10 μm) and the extinction coefficient were found to be enhanced by 400% (from 24 ± 15 to 98 ± 40 μg/m3) and 175% (from 89 ± 57 Mm−1 to 156 ± 79 Mm−1), respectively, during these premonsoonal dust‐loading events. Moreover, based on the air mass trajectory, these dust storms can be categorized into two categories: (a) mineral dust events (MDEs), which involve long‐range transported dust plumes traversing through the lower troposphere to reach the Himalayas and (b) polluted dust events (PDEs), which involve short‐range transported dust plumes originating from the arid western regions of the Indian subcontinent and traveling within the heavily polluted boundary layer of the Gangetic plains before reaching the Himalayas. Interestingly, compared to the background, the SSA and AAE decrease during PDEs but increase during MDEs. More importantly, we observe a twofold increase in black carbon concentrations and the aerosol absorption coefficient (relative to the background values) during the PDEs with negligible changes during MDEs. Consequently, the aerosol‐induced snow albedo reduction (SAR) also doubles during MDEs and PDEs relative to background conditions. Thus, our findings provide robust observational evidence of substantial dust‐induced snow and glacier melting over the Himalayas.

Improving the hydrological consistency of a process-based solute-transport model by simultaneous calibration of streamflow and stream concentrations

Abstract. The consistency of hydrological models, i.e. their ability to reproduce observed system dynamics, needs to be improved to increase their predictive power. As using streamflow data alone to calibrate models is not sufficient to constrain them and render them consistent, other strategies must be considered, in particular using additional types of data. The aim of this study was to test whether simultaneous calibration of dissolved organic carbon (DOC) and nitrate (NO3-) concentrations along with streamflow improved the hydrological consistency of a parsimonious solute-transport model. A multi-objective approach with four calibration scenarios was used to evaluate the model's predictions for an intensive agricultural headwater catchment. After calibration, the model reasonably simultaneously reproduced the dynamics of discharge and DOC and NO3- concentrations in the stream of the headwater catchment from 2008–2016. Evaluation using independent datasets indicated that the model usually reproduced dynamics of groundwater level and soil moisture in upslope and riparian zones correctly for all calibration scenarios. Using daily stream concentrations of DOC and NO3- along with streamflow to calibrate the model did not improve its ability to predict streamflow for calibration or evaluation periods. The approach significantly improved the representation of groundwater storage and to a lesser extent soil moisture in the upslope zone but not in the riparian zone. Parameter uncertainty decreased when the model was calibrated using solute concentrations, except for parameters related to fast and slow reservoir flow. This study shows the added value of using multiple types of data along with streamflow, in particular DOC and NO3- concentrations, to constrain hydrological models to improve representation of internal hydrological states and flows. With the increasing availability of solute data from catchment monitoring, this approach provides an objective way to improve the consistency of hydrological models that can be used with confidence to evaluate scenarios.

Integrating green manure and fertilizer reduction strategies to enhance soil carbon sequestration and crop yield: evidence from a two-season pot experiment

The excessive use of chemical fertilizers in agricultural production has led to diminishing returns, necessitating alternative methods to enhance soil fertility and reduce fertilizer dependency. One promising approach is the integration of leguminous green manure, which improves soil structure, enhances nutrient cycling, and supports sustainable farming practices. However, the application of green manure in systems with continuous fertilizer reduction remains underexplored. This study addresses this gap by investigating the effects of reducing nitrogen and phosphorus fertilizers (N-P) by up to 24% in conjunction with multiple cropping of soybean green manure on soil fertility, organic carbon fractions, and wheat yield. The research employed a pot experiment conducted over two wheat-growing seasons (March 2021 to July 2022) at an experimental station in Baoji, China. Treatments included CK (control, no fertilizer), CF (conventional fertilizer), and reduced N-P fertilizer applications by 6% (RF6), 12% (RF12), 18% (RF18), and 24% (RF24). Key findings revealed that RF12 had no significant impact on wheat grain yield compared to CF. The incorporation of soybean green manure significantly improved soil alkaline nitrogen by 22.3% and available phosphorus by 30.7%, while high-labile organic carbon (H-LOC) and microbial biomass carbon (MBC) increased by 34.5 and 29.6%, respectively. Additionally, a notable increase of 12.4% in soil organic carbon content was observed, suggesting enhanced carbon sequestration potential. This study provides valuable insights into sustainable agricultural practices by demonstrating that incorporating leguminous green manure alongside moderate fertilizer reduction can maintain crop yield, improve soil nutrient availability, and increase organic carbon content, thus supporting reduced reliance on chemical fertilizers and promoting long-term soil fertility and carbon sequestration.

Optimizing Temperature and Time for Producing Coconut Shell Activated Charcoal to Reduce Free Fatty Acids in Used Cooking Oil

Activated charcoal is a type of carbon that has a high capacity to absorb anions, cations, and molecules in both organic and inorganic compounds, whether in solutions or gases. This research aims to determine the effect of temperature variation and carbonization time on optimizing the production of activated charcoal from coconut shells as an environmentally friendly solution to reduce the acid value in used cooking oil. The activated charcoal production process in this study uses carbonization with temperature variations of 200°C, 250°C, 300°C, and 350°C, and carbonization times of 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours. The best results for activated charcoal are obtained at 350°C and 3 hours, with moisture content of 0.811%, volatile matter of 5.926%, ash content of 1%, and other parameters that meet the Indonesian National Standard (SNI) for activated charcoal, such as fixed carbon content, iodine absorption capacity in accordance with SNI-06-3730-1995, and an acid value that also meets the standard (SNI 01-3741-2013).

Relationships Between Soil Respiration and Crop Productivity in Different Crop Fields

ABSTRACT Investigating the seasonal variations in soil respiration in different crop fields and their relationships with crop productivity is crucial to understanding the key biotic controls of soil respiration. A field experiment was performed during the 2020‒2021 winter wheat‒soybean, canola‒maize and broad bean‒sweet potato growing seasons. The seasonal variations in soil respiration, soil temperature and moisture were measured. The variables that were associated with crop productivity were also determined. The results showed that crop types significantly (p < .05) affected the mean seasonal soil respiration. Most variables that were associated with crop productivity exhibited obvious seasonal variation patterns. The soil temperature, moisture and crop productivity comprehensively influenced the soil respiration, and models based on these potential controlling factors explained 45.7%‒59.2% (R 2 = 0.457‒0.592) of the variation in soil respiration in the different crop rotation fields. A model based on the mean seasonal soil temperature, moisture, leaf area index, and root carbon content explained 68.3% (R 2 = 0.683) of the variation in the mean seasonal soil respiration across the different crop fields. We demonstrated the potential of effectively characterizing the variations in soil respiration in agroecosystems using temperature, moisture and crop productivity.