Fulvic Acid Carbon Research Articles

Effects of chemical fertilizer with rice straw on the carbon compositions of tobacco-planting soil

This study explored the changes in carbon components of tobacco-planting soil by the application of rice straw as organic materials to replace chemical fertilizers partially. Flue-cured tobacco was applied to the soil as base fertilizer to investigate the mineralization of soil organic carbon during its growing period. At 0 d, the humic acid carbon (HA-C), humin carbon (HM-C), HU ratio, PQ value and HM-C/(HA-C + FA-C) are 31.67, 31.40, 60.05, 28.01 and 27.75%, respectively which is higher than those of chemical fertilizer alone. At 30 d, the humus carbon (HE-C), HA-C, and fulvic acid carbon (FA-C) were 29.41, 20.97 and 30.49%, respectively. At 90 d, the A2920/1630 values were 227.43 and 232.32% higher than chemical fertilizer. Application of rice straw and decomposed rice straw with less fertilizer can increase the content of soil organic matter, HA-C, HM-C and FA-C in the tobacco-planting soil. This method increases the content of aliphatic chain hydrocarbons and reduces the amount of aromatic carbon, thus increasing aliphatic properties and decreasing the aromatic properties of soil. The treatment with chemical fertilizer reduction with decomposed rice straw also accelerates the formation and accumulation of stable components such as humic acid and humin and significantly improves the humification of soil humus. Bangladesh J. Bot. 53(3): 811-822, 2024 (September) Special

Assessing the formation and stability of paddy soil aggregate driven by organic carbon and Fe/Al oxides in rice straw cyclic utilization strategies: Insight from a six-year field trial

Soil organic carbon (SOC) and iron/aluminum (Fe/Al) oxides are key cementing agents in driving soil aggregate formation, yet their direct effects and interactions on aggregate under long-term rice straw cyclic utilization (LSCU) in cold regions are still unclear. We compared chemical fertilizer (CF) with LSCU strategy: rice-straw (RS), biochar (RB), and biochar-based fertilizer (BF). We showed that the increase of macroaggregate (2–0.25 mm) is associated with SOC, dissolved organic carbon (DOC), humin carbon (HUC), amorphous and organic complexed Fe/Al oxides (Feo, Fep, Alo, Alp), and in each size of the aggregate, there exists an interaction between SOC (fractions) and Fe/Al oxides. Furthermore, aggregate stability was determined by Feo, Fep, and Alo. LSCU enhances macroaggregate and aggregate stability by increasing SOC and Fe/Al oxides in the bulk soil and aggregates, but there are differences among LSCU. In all treatments, RS had more DOC, fulvic acid carbon (FAC), humic acid carbon (HAC) and Fep; while RB had more SOC, HUC, free Fe/Al oxides (Fed, Ald), Feo, Alp; and BF had more Alo in bulk soil. Over the years, RS increased the DOC, FAC and HAC, whereas RB enhanced the stable SOC fractions (HUC) and promoted high reactive Fe/Al oxides formation (Feo, Fep, Alo), and BF increased DOC, Feo, Fep and Alo. Moreover, RB increases the direct pathway of SOC and Fe/Al oxides to aggregate, promoting aggregate formation. Our study provides new perspective on the mechanisms and promising practice for improving rice straw utilization efficiently, paddy soil fertility and productivity sustainably in cold regions.

The Content of Soil Glomalin Concerning Selected Indicators of Soil Fertility

The glomalin content is generally considered an indicator of the soil organic matter (SOM) quality. The content of easily extractable glomalin (EEG) and the total glomalin (TG) content was investigated across 71 different sites in the Czech Republic with arable soil and crop production (12 chernozems, 30 luvisols, 17 cambisols, and 12 fluvisols). The majority of the crops in the crop rotation were cereals (45.5%—mainly winter wheat, winter barley, and spring barley). The proportion of winter canola within the crop rotation was 15.9%. The contribution of other crops was substantially smaller (alfalfa, clover, potatoes, beet, silage maize, grain maize). The representation of crops in the crop rotation is standard for conventional farming in the Czech Republic. Based on the results of long-term field monitoring at 71 sites in different soil–climate conditions, we can state the following. The TG content was significantly correlated with the soil organic matter carbon content (CSOM), as well as another important indicator of SOM quality (humic and fulvic acid carbon content ratio—CHA/CFA). A significant and positive correlation was also determined for the TG and clay content (size < 0.002 mm), as well as particles smaller than 0.01 mm. The easily extractable glomalin content (EEG) did not differ based on the reference soil group (RSG). On the other hand, the total glomalin content (TG) was significantly higher in the chernozem RSG in comparison with other RSGs (luvisols, cambisols, fluvisols). There was no relationship between the pHCaCl2 and glomalin (EEG; TG). The same can be said about the relationship between glomalin (EEG; TG) and the bulk density and porosity. No link was established between the glomalin content (EEG; TG) and phosphorus plant-available content. There was no relationship between the amount of applied organic matter (carbon inputs) and the soil glomalin content (EEG; TG). This relationship was not influenced by the type of applied organic fertilizer. No significant relationship was found for either straw, manure, or compost. The data on the glomalin content are significantly influenced by the site (soil type and soil texture).

Organic fertilizer prepared by thermophilic aerobic fermentation technology enhanced soil humus and related soil enzyme activities

AbstractOrganic fertilizer (OF) prepared from chicken manure in a high‐temperature aerobic fermenter contains high levels of nitrogen, phosphorus and potassium. The effect of high‐nutrient OF substitution for chemical fertilizer (CF) on soil organic carbon stability is worth exploring. We used OF to replace CFs for supplying crops, and we set five OF replacement rates as 0, 25%, 50%, 75% and 100% in the black soil zone of Northeast China. We explored the variations in soil humus carbon contents, enzyme activities and nutrient contents (0–10 cm and 10–20 cm). Two‐way ANOVA results showed that interaction between soil depth and OF substitution significantly affected soil pH, total nitrogen, organic carbon, available potassium, water‐soluble carbon substance (WSSC) and activities of soil β‐galactosidase (β‐gal), N‐acetyl‐β‐D‐glucosaminidase (NAG) and cellobiohydrolase. The treatments of OF75 and OF100 increased soil pH, and the content of soil organic carbon, humic acid carbon (HAC), fulvic acid carbon (FAC), WSSC, total phosphorus, available phosphorus (AP), total potassium and available potassium was increased in OF75 and OF100 treatment. Treatments of OF75 and OF100 increased the tested soil enzyme activities except for oxidase activities of 0–10 cm soil layer. There was a positive correlation between HAC and AP contents, and a positive correlation between FAC and soil pH, total nitrogen and available potassium contents. The key influencing factors of soil FAC were the activities of NAG, α‐galactosidase and β‐gal. It can be concluded that OF substitution promoted soil humus carbon accumulation by affecting hydrolase activity related to carbon conversion.

Enhanced humification via lignocellulosic pretreatment in remediation of agricultural solid waste

Stover and manure are the main solid waste in agricultural industry. The generation of stover and manure could lead to serious environmental pollution if not handled properly. Composting is the potential greener solution to remediate and reduce agricultural solid waste, through which stover and manure could be remediated and converted into organic fertilizer, but the long composting period and low efficiency of humic substance production are the key constraints in such remediation approach. In this study, we explore the effect of lignocellulose selective removal on composting by performing chemical pretreatment on agricultural waste followed by utilization of biochar to assist in the remediation by co-composting treatment and reveal the impacts of different lignocellulose component on organic fertilizer production. Aiming to discover the key factors that influence humification during composting process and improve the composting quality as well as comprehensive utilization of agricultural solid waste. The results demonstrated that the removal of selective lignin or hemicellulose led to the shift of abundances lignocellulose-degrading bacteria, which in turn accelerated the degradation of lignocellulose by almost 51.2%. The process also facilitated the remediation of organic waste via humification and increased the humic acid level and HA/FA ratio in just 22 days. The richness of media relies on their lignocellulose content, which is negatively correlated with total nitrogen content, humic acid (HA) content, germination index (GI), and pH, but positively correlated with fulvic acid (FA) and total organic carbon (TOC). The work provides a potential cost effective and efficient framework for agricultural solid waste remediation and reduction.

Effects of slope aspect on soil aggregates humus on cut slopes in alpine areas of Southwest China

Large-scale road construction has resulted in bare cut slopes in alpine areas, leading to soil erosion and reduced fertility. Soil humus is the basis of soil fertility and an important carbon pool; it is affected by many factors. However, the effects of slope aspect on soil humus on cut slopes are still largely unclear. We studied the differences in the humus content in bulk soil and soil aggregates under four slope aspects (south-facing slope (SFS), west-facing slope (WFS), east-facing slope (EFS), and north-facing slope (NFS)) in alpine areas and analyzed the driving effects of soil physicochemical factors on humus distribution. The contents of fulvic acid carbon (FA-C), humic acid carbon (HA-C), humin carbon (HU-C), humus extractable carbon (HE-C) and total humus carbon (TH-C) differed among four slope aspects. Humus carbon did not differ among large macro-aggregates (LMA), small macro-aggregates (SMA) and micro-aggregates (MIA). Only the contents of humus carbon in silt + clay fraction (SCA) were significantly lower than those in the other soil aggregates for the NFS and EFS. Soil water content (SWC), soil organic matter (SOM), total nitrogen (TN), and available phosphorus (AP) were important soil physicochemical factors affecting the distribution of humus. Our results suggest a significant effect of slope aspect on the contents of humus carbon, and the silt + clay fraction had a weak ability to retain humus carbon. The study provides a theorical basis for future humus research and soil fertility management of cut slopes in alpine areas.

Characteristics and environmental significance of organic carbon deposition in Baiyangdian Lake, China, 1969–2020

Lake sediments provide a basis for ecological information that can reconstruct the history of a lake ecosystem and clarify the carbon sink process. We combined chronological information relating to sediment cores in Baiyangdian Lake with the history of human activities, to examine the influence of the natural environment and human activities on the humification of organic carbon. This analysis revealed the evolution of the ecological environment in the lake over the past 50 years. The results showed the average deposition rate of sediments to be 0.957 cm/a; with the total organic carbon and total nitrogen contents of sediments ranging from 14.32 to 333.19 g/kg and from 0.95 to 26.90 g/kg, respectively. The δ13C values ranged from −13.04 ‰ to −29.07 ‰, while the δ15N values ranged from −1.43 ‰ to 8.37 ‰. The fulvic acid carbon (FAC) content ranged from 0.52 g/kg to 14.21 g/kg, and the humic acid carbon (HAC) content ranged from 1.67 g/kg to 23.82 g/kg. The HAC/FAC value gradually increased as the sediment deepend. The results of each index in the sedimentary column, combined with the dating information, allowed us to conclude that, from 1969 to 1985, human activities had little effect on the lake, and the source of organic carbon and the humification process remained stable. During this period, the water purification function of the lake continued to improve. From 1985 to 2014, the surrounding economy developed rapidly, resulting in significant changes in the lake's ecological structure and the distribution of lake plants. Serious eutrophication occurred, leading to increased pollution Between 2014 and 2020, the lake protection measures implemented achieved initial positive results. During the period, the source of organic carbon and the humification process stabilized, eutrophication was alleviated, and the burial and fixation of organic carbon gradually reached a healthier state.

Content and Composition of Organic Matter in Some Sewage-Treated Fish Pond Soils in Relation to Productivity

The organic matter content and its composition in relation to primary productivity of soil in 12 sewage-treated fish ponds were studied. Organic carbon contents of the soils were fairly high, ranging between 1.02 and 3.85%. The amount of humus carbon, on an average, constituted 23.7% of the total organic carbon. The carbon content of humic and fulvic acids of the soils ranged from 0.066 to 0.222 and 0.210 to 0.560%, respectively, constituting, on an average, 27.7 and 72.3%, respectively, of the total humus carbon. Primary productivity of the pond was found to be significantly correlated with total organic carbon, humus carbon, and humic acid and fulvic acid carbon contents of the soils.

Carbon Stock, Carbon Fraction and Nitrogen Fraction of Soil Under Bamboo (Dendrocalamus asper Back.) and Non-Bamboo Vegetation

<span lang="EN-US">The type of vegetation and soil organic matter affect the carbon fraction, nitrogen fraction and soil carbon stocks that contribute to the global carbon cycle. Therefore, the calculation of the composition of the fractions in different land covers is very important as a potential indicator of the effect of land management practices on soil organic carbon dynamics and supports the reduction of carbon dioxide (CO<sub>2</sub>) and soil carbon storage. This research aimed to determine the composition of the carbon fraction, nitrogen fraction and soil carbon stock in different land cover. There were six types of land cover with vegetations of 10-year-old bamboo, 30-year-old bamboo, 50-year-old bamboo, bulrush, a mixture of brushwood and bulrush, and a mixture of <em>Albizia falcataria</em> and brushwood, each of which was sampled three times. Soil samples were used to determine microbial biomass, particulate organic, humic acid, fulvic acid and soil carbon stock. The six land cover types showed significant differences in all fractions and soil carbon stocks. Fifty-year-old bamboo vegetation has the highest carbon storage of 0.029 g g<sup>-1</sup> soil. The stable carbon fraction, in the form of humic acid and fulvic acid, in 50-year-old bamboo vegetation is more excellent than that in other vegetation. This study shows that 50-year-old bamboo vegetation has the potential to sequester carbon and store carbon in forms that decompose slowly, namely humic acid and fulvic acid, in the soil for a longer period.</span>

Latitudinal and Altitudinal Patterns and Influencing Factors of Soil Humus Carbon in the Low-Latitude Plateau Regions

The composition of forest soil organic matter is an important part of the global carbon cycle, which is effective by temperature and moisture. As we all know, the temperature and moisture in the low-latitude plateau regions are very sensitive to changes in latitude and altitude. However, the composition of soil organic matter response to changes in latitude and altitude in the low-latitude plateau regions is unknown. In this study, the effects of latitude (21–29° N) and altitude (500–4000 m) on soil organic carbon (SOC) and humic acid carbon (HAC), fulvic acid carbon (FAC), and humin carbon (HMC) in forest surface soil (0–10 cm) were investigated. The results showed that the contents of soil organic carbon and humus increased with the increase in altitude and latitude. The effect of altitude on the composition of organic matter was significant only at 23° N to 25° N. The composition of organic matter is not only regulated by mean annual temperature (MAT) and soil moisture content (SMC) but also affected by soil pH, carbon to nitrogen ratio (C/N), and powder. The soil surface layer (0–10 cm) carbon sequestration capacity in high-latitude and high-altitude areas is stronger than that in low-latitude and low-altitude areas. As a consequence, in today’s response to global climate change, the high carbon sequestration capacity of high latitude and high altitude areas should be given attention and protection.

Influence of fertilization and tillage systems on the humus condition of dark-grey podzolic soil

Topicality. Modern agricultural systems have an ambiguous effect on the humus condition of soils. The urgent task is to restore and preserve the fertility of the dark grey podzolic soil and increase the organic matter content in the agricultural system. Purpose. To determine changes in the humus condition of dark grey podzolic soil under sunflower under different tillage and fertilisation systems using crop rotation by-products. Materials and methods. In the long-term stationary experiment, the following tillage systems were used: ploughing at a depth of 25–27 cm, disking at 15–17 cm and disking at 10–12 cm. Ploughing under sunflower was carried out with plough PLN-3-35, disking – disc harrow AG-2.4-20. The fertilisation systems were as follows: 1) no by-products; 2) by-products; 3) N10 (ammonium nitrate) per 1 tonne of by-products. The humus content in the soil was determined according to the I.V. Tyurin’s method, the group composition of humus – according to method of M. M. Kononova and N. P. Bielchikova. Results. It was established that the highest humus content in the 0–20 cm layer of the soil under sunflower was 2.09 % for the variant with disking at a depth of 15–17 cm using by-products. On dark grey podzolic soil, humus accumulation is enhanced by disking at 15–17 cm and fertilisation with by-products and N10, which is accompanied by characteristic changes such as an increase in the total content of humic acids and non-hydrolysed residue in the humus group composition. The highest content of humic acids was 0.29–0.34 % in the plots with moldboardless tillage under different fertilisation systems. The lowest content of this important humus fraction was 0.23–0.25 % in the variant with different depth ploughing. In the variants with disking to a depth of 15–17 cm and 10–12 cm when using by-products with N10, the highest values of the ratio between carbon in humic acids and carbon in fulvic acids were 1.26 and 1.27, respectively. Conclusions. Application of moldboardless tillage, disking at a depth of 15–17 cm and fertilisation system with by-products + N10 contribute to the recovery of dark grey podzolic soil fertility and improvement of its humus condition. In Western Polissia of Ukraine, it is recommended to carry out disking at a depth of 15–17 cm with the use N10 per 1 ton of by-products in the fertilisation system for sunflower cultivation. Key words: humus, dark grey podzolic soil, fertilization system, humic acids, fulvic acids

Effects of Applying Different Organic Materials on Grain Yield and Soil Fertility in a Double-Season Rice Cropping System

Double-cropping rice cultivation reduces soil fertility, and the extensive use of chemical fertilizers has harmful effects on both the environment and grain yield. The application of organic materials could be used as a practical strategy to maintain soil fertility and improve grain yield in a double-season rice cropping system. For this purpose, field experiments with six growing seasons over three years, from 2016 to 2018, were conducted to assess the effects of five organic materials (biochar, Chinese milk vetch, rice straw, rapeseed cake fertilizer, and manure) on the grain yield and soil fertility, aiming to save about 25% of the chemical nitrogen (N) fertilizer required for all rice growing stages. The result showed that, compared with CK (the most common dose of fertilizer in this study region; 100% chemical fertilizer without organic fertilizer), the grain yield and soil fertility of double-cropped rice were increased after applying organic fertilizers for three consecutive years. Specifically, the CRC treatment (Chinese milk vetch (10.77 t ha−1 in fresh)/rice straw (26.51 t ha−1 in fresh) + 75% chemical fertilizer) showed significantly higher rates of effective panicles (4.65–10.92%) and annual grain yield (8.00–8.82%). The total N, total phosphorus (P), total potassium (K), alkaline N, and available P content in the CRC soil were significantly increased by 11.85%, 12.22%, 15.08%, 23.32%, and 41.04%, respectively, relative to CK. The decomposition of the applied Chinese milk vetch and rice straw combined with 75% chemical fertilizer resulted in more soil humus (9.50 g kg−1), humic acid (3.19 g kg−1), fulvic acid (3.26 g kg−1), and active organic carbon (5.78 g kg−1) and a significantly higher carbon pool management index (13.5%), as well as significantly higher soil urease activity (18.10%) and acid phosphatase activity (17.64%). Therefore, in this study, Chinese milk vetch (10.77 t ha−1 in fresh) in the early rice season/rice straw (26.51 t ha−1 fresh) in the late rice season + 75% chemical fertilizer treatment was the optimal dose for the double-season rice cropping system. It resulted in higher rice yields and has the potential to be used for more sustainable soil fertility.

Composition, distribution, and source of organic carbon in surface sediments of Erhai Lake, China

Lake sediment is an important organic carbon (OC) sink. Nevertheless, few studies have been conducted on sediment organic carbon (SOC) in lakes, and the effects of environmental variables on SOC pools remain poorly understood. We combined physicochemical and spectroscopic analyses to investigate the composition, distribution, and source of OC in surface sediments of Erhai Lake, southwest China, and explored the relationships between environmental variables and its SOC pool. The SOC pool consists of relatively high proportions of labile organic carbon fractions, mainly from algal production, which are rapidly decomposed and exhibit high turnover rates. The relative content of humus carbon ranges from 13.5 % to 20.5 %, with fulvic acid carbon predominating (average 52.95 %), indicating weak humification and a relatively active humus carbon pool. The dissolved organic matter in water column and sediments of Erhai Lake is largely influenced by endogenous production, with a great contribution from phytoplankton. Surface sediments contained more protein-like components than overlying waters (80.0 % vs. 63.0 %), attributed mainly to abundant algal deposition and intense bacterial metabolism. Among environmental variables, sediment chlorophyll a showed the strongest relationship with the SOC pool, and was associated with rapid decomposition and promotion of the humification process, which supported the conclusion that algae had an important influence on the SOC pool. The SOC pool in the southern region of the lake is mainly contributed by algae, other microorganisms, and sewage, exhibiting a greater potential to release organic matters into the water column. The center and northern SOC pools show relatively stable characteristics and stronger OC sink capacity, mainly because of the input of terrestrial refractory organic matters from runoff. Our data shed light on the OC storage mechanisms in the surface sediments of Erhai Lake and provide theoretical bases for enhancing the OC sink of sediments in the lake.

Качественный состав гумуса чернозема выщелоченного в севооборотах северной лесостепи Южного Урала

Abstract. The purpose of the research was to establish the degree of agrogenic impact on the qualitative composition of humus by monitoring the content of total carbon, humic and fulvic acid carbon in the arable soil layer of leached chernozem. A comparative assessment of the dynamics of the group composition of leached chernozem humus in the conditions of the northern forest-steppe of the Chelyabinsk region, in various crop rotations on two fertilization backgrounds P and NP was carried out. Methods. The research was carried out in a long-term field experiment from 1998 to 2021. The group composition of humus was determined in soil samples taken from each variant of the experiment every five years by the accelerated pyrophosphate method according to the scheme of I. V. Tyurin modified by V. V. Ponamareva and T. A. Plotnikova. Results. According to the results of our studies of the qualitative indicators of humus, it was found that slightly acidic soils of leached chernozem with prolonged application of mineral fertilizers in moderate doses were characterized by a dominant carbon content of humic acids (Cha), regardless of crop rotation options. It was found that the average ratio of the carbon content of humic acids to the carbon of fulvic acids against the background of P in the grain two-field crop rotation compared with the grain-pair four-field crop rotation is 25 % wider. With the permanent cultivation of spring wheat against the background of mineral nutrition NP, the ratio of carbon of humic acids to carbon of fulvic acids (Cha/Cfa) was on average 20.5 % wider during the research period, compared with the grain-steam four-field crop rotation, due to a decrease in the humification process. Strong correlations have been established between the total carbon content from the precipitation of the growing season against the background of P in the grain-pair four-field crop rotation and grain two-field. The scientific novelty lies in the study of the dynamics of changes in the orientation of the group composition of humus in different crop rotations, at different levels of fertilization and agrotechnologies of cultivation.

Combined management of olive mill wastewater and compost in olive grove: Effects on soil chemical properties at different layers depth

The effects of combined agronomic application of olive mill wastewater (OMW) with compost were evaluated in an olive field (Tunisia). Four treatments were used. The first plot was spread by 50 m3 ha−1 of OMW, the second treated with 5 T ha−1 of compost, the third amended by both (50 m3 ha−1 + 5 T ha−1), and the fourth, used as a control. After ten days of organic amendment, the soil upper layers presented the highest organic matter (OM), total nitrogen, available phosphorus, exchangeable potassium and sodium contents, with the highest values noted for the mixed treatment. Also, this treatment exhibited the most important soil phenolic concentrations accumulation. All organic fertilizing treatments produced significant increase in the total alkali-extractable humic carbon (HEC), humic acid carbon (HAC) and fulvic acid carbon (FAC) concentrations, especially with OMW and compost applied simultaneously.

Straw Strip Return Increases Soil Organic Carbon Sequestration by Optimizing Organic and Humus Carbon in Aggregates of Mollisols in Northeast China

In agroecosystems, effective straw return modes are one of the key practices for increasing soil fertility and carbon (C) availability. Although they improve soil quality, there is currently little information available regarding the influence of distinct straw return modes with respect to potential soil organic carbon (SOC) sequestration. In this study, we established a five-year (2015–2019) field experiment in Mollisols of Northeast China, which included four straw return modes, plow tillage with straw return as the control (PTS), rotary tillage with straw return (RTS), rotary tillage with straw strip return (RSS), and plow tillage with straw strip return (PSS), to investigate the impact on soil physicochemical properties, aggregates, and C sequestration. The results reveal that RSS effectively improved the soil physicochemical properties. Such responses increased the contents of SOC, fulvic acid carbon (FAC), and humin carbon (HMC) in all soil layers (0–30 cm). The proportion of macroaggregates was higher in RSS, whereas the proportion of silt/clay was the lowest at depths of 0–20 cm; consequently, the mean weight diameter (MWD) and geometric mean diameter (GMD) of RSS were higher at depths of 0–20 cm due to the improved physical soil structure. In the 0–10 cm and 20–30 cm layers, the highest humic acid carbon (HAC) concentrations associated with all aggregate sizes were found for RSS, in contrast to 10–20 cm, which had increased HMC. Structural equation modeling (SEM) revealed that C transformation was mainly mediated through silt/clay-associated FAC, HMC, and SOC, ultimately determining HAC (81%) and HMC (85%) as the primary humus fractions for SOC sequestration. Therefore, this study shows that RSS is the suitable straw return mode for effectively improving soil quality, aggregate stability, and C sequestration in Mollisols of Northeast China.

Influence of biochar on the sorption and leaching of thiamethoxan in soil

This study evaluated the long-term effect of biochar application on the sorption and desorption of thiamethoxam in a Haplic Plinthosol. The experiment was conducted in a randomized block design with combination of doses of mineral fertilizer NPK (0 and 300 kg·ha−1 formula 05-25-15) and biochar (0, 16 and 32 Mg ha−1). Deformed soil samples were collected in the field from the 0-0.10 m layer of all plots to determine the sorption and desorption of the thiamethoxam insecticide in the soil; fulvic acid (FA), humic acid (AH) and humin (HUM) carbon contents; and total organic carbon. The Batch slurry method was used to evaluate sorption and desorption. The Freundlich isotherm adequately described thiamethoxam sorption in all treatments. The application of biochar increased the sorption (Kfs) and decreased the desorption (Kfd) of thiamethoxam. The sorption intensity (1/n) showed reduction characteristics as the soil concentration of thiamethoxam increased. Biochar has a sorption effect on the soil through covalent bonds and H-bonds with the insecticide molecules, thereby indirectly increasing the sorption potential in the chemical fractions of the organic matter of soil. The application of 32 Mg ha−1 of biochar significantly reduced thiamethoxam in the soil solution. Altogether, the present study reveals that biochar application in soil is a promising tool for mitigating the contaminant potential of thiamethoxam in subsurface waters.

Fluorescence Spectroscopy and 13C NMR Spectroscopy Characteristics of HA in Black Soil at Different Corn Straw Returning Modes.

A three-year field experiment was conducted to analyze the effects of straw enrichment and deep incorporation on the humus composition and the structure of humic acid (HA) in black soil. The differences in the HA structure between different straw returning methods were detected by three-dimensional fluorescence spectroscopy and 13C NMR technology. The purpose of this paper is to provide a theoretical basis and data support for improving the straw returning system. Four different treatments, including no straw applied (CK), straw mulching (SCR), straw deep ploughing (MBR), and straw enrichment and deep incorporation (SEDI: harvested the corn straw from four rows together with a finger-plate rake and then crushed and buried them in one row in the 20∼40 cm deep level in the subsoil with a wind-driven input cylindrical plough), were used in this study. Our results showed that compared to CK treatment, SEDI significantly increased the contents of organic carbon (SOC), soil humic acid carbon (HAC), fulvic acid carbon (FAC), and humin C content (HM-C) in the subsurface soil layer by 27.47%, 34.33%, 19.66%, and 31.49%, respectively. Among all the straw returning treatments, SEDI treatment had the most significant effect in increasing the contents of HEC, HAC, and FAC. Straw returning not only reduced the degree of condensation and oxidation of the HA structure but also increased the proportion of alkyl C and enhanced the hydrophobicity of the HA structure in subsurface soil. Moreover, SEDI treatment significantly increased the proportion of aliphatic C/aromatic C of the HA structure in subsurface soil and improved the aliphatic property of HA, which had a significant effect on the HA structure compared to other treatments.

Effect of Food-fodder Farming on Sustainable Resources Use and Carbon Dynamics in Rainfed Semi-arid Tropics of India

ABSTRACT Soil organic carbon (SOC) is highly sensitive to land use change and helps in maintaining soil quality. Changes in soil fertility status, SOC dynamics, and carbon indices were studied in a four-year experiment with nine sets of food-fodder cropping systems (CS) and three resource conservation techniques like rainfed (RC1), life saving irrigation (RC2) and in-situ moisture conservation practices (RC3). Results showed that the CS5 [Tri-Specific Hybrid (TSH) + Desmanthus virgatus+ (Sorghum + Cowpea – Chickpea)] recorded the highest values 12.25 g kg−1, 41.5 mg kg−1, 3.5 g kg−1, 289.5 mg kg−1, 424.8 µg g−1 soil, 54.69% and 39.31% of total carbon (TC), hot water-soluble carbon (HWSC), particulate organic carbon (POC), labile carbon (LC), soil microbial biomass carbon (SMBC), humic acid carbon (HA-C) and fulvic acid carbon (FA-C), respectively. Among resources conservation practices, RC3 improved the SOC (56.16%) and other carbon fractions significantly as compared to RC1. Significant and positive correlations (P < 0.05) were found between carbon pools and available nutrients. The carbon management index (CMI) was also maximum (193) with CS5 and CS9 [TSH + Sesbania sesban+ (Sorghum + Cowpea – Barley)] and RC3 (232). Therefore, promoting cultivation of food-fodder system with in-situ moisture conservation practices is considered as sustainable management option for sequester more carbon, sustainability and soil quality in rainfed semi-arid ecosystem.

Distribution of polycyclic aromatic hydrocarbons (PAHs) in the bottom sediments of a dam reservoir, their interaction with organic matter and risk to benthic fauna

PurposeThe aims of the study were to investigate the interaction between fractions of organic matter and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments and to use mussels as passive biomonitors and consensus-based sediment quality guidelines for ecological risk assessment in sediments.MethodsBottom sediment samples were taken from 46 points located in the Rożnów reservoir (Poland). The sediment organic matter (SOM) characteristics included total carbon (TC), total organic carbon (TOC), humic acid carbon (Cha), fulvic acid carbon (Cfa), non-hydrolysing carbon (Cnh), and dissolved organic carbon (DOC). The extraction procedure was carried out in bottom sediments as well as in freeze-dried mussel tissue samples to directly determine the accumulation potential of PAHs to the living organisms in their natural environment.ResultsThe content of organic matter fractions was in the following order: Cfa (fulvic acid) > Cnh (non-hydrolysing carbon) > Cha (humic acid) > DOC (dissolved organic carbon). The mean ∑16PAHs (μg kg−1) concentration was 1755.2 ± 724 (total) and 256 ± 254 (bioavailable) in sediments and 1740 ± 72.2 in the mussel tissues. A significant positive correlation was found between the concentration of PAHs in the mussel tissues and the total and bioavailable concentration of PAHs in bottom sediments.ConclusionThe PAH concentration in bottom sediments depended on the stabile carbon forms Cnh. Principal component analysis (PCA) suggests that the fine fraction can significantly increase the bioavailability of PAHs and can be an important factor in the distribution of PAHs in the sediments.