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Mineral-associated soil organic matter (MAOM) is seen as the key to soil carbon sequestration, but its stability often varies with types of exogenous organic materials. Fulvic acid and manure are ones of the exogenous organic materials used for the improvement of degraded soil. However, little is known about if and how fulvic acid and manure affect the stability of MAOM. Using a field experiment of four fertilization treatments (no fertilization, mineral fertilizers, fulvic acid, and manure) and a comprehensive meta-analysis using relevant studies published prior to January 2020, we investigated effects of exogenous fulvic acid and manure applications on four MAOM stability indexes: association intensity, humus stabilization index, iron oxide complex coefficient, and aluminum oxide complex coefficient. Exogenous fulvic acid and manure applications increased soil organic carbon fractions by 26.04-48.47%, MAOM stability by 12.26-387.41%, and complexed iron/aluminum contents by 16.12-20.01%. Fulvic acid application increased MAOM stability by promoting mineral oxide complexation by 20.33% and manure application improved MAOM stability via increasing humus stabilization by 21-25%. Association intensity was positively correlated with contents of soil carbon fractions and the metal oxide complex coefficients were positively correlated with iron/aluminum oxide contents. Moreover, stable-humus exerted significantly positive direct and indirect effects on association intensity and humus stabilization index, while amorphous iron/aluminum content had significantly negative influences on metal oxide complex coefficients. The meta-analysis verified that long-term fulvic acid application improved MAOM stability more so than manure application in acidic soils. We recommend that strategies aiming to prevent land degradation should focus on the potential of fulvic acid as a soil amendment because it can significantly increase MAOM stability.

The straight head disease of rice is one of the main problems limiting rice production. Arsenic (As) methylation in paddy soils is considered to be highly related to the occurrence of the straight head disease. As a typical field practice, rice fields are usually drained during the late tillering stage and the mid-late grain filling stage. Nevertheless, the key influencing factors on the As methylation efficiency during paddy soil drying remain unclear. In this study, an indoor cultivation experiment was set up to simulate the drying process of paddy soil. Two As-contaminated soils collected from Xingren (XR) in Guizhou province and Nandan (ND) in Guangxi province were used as test soils. Each soil was treated with the addition of rice straw (RS) and without rice straw (CK). With the drying of paddy soil (0, 24, 36, 48, and 60 h), the changes in soil Eh, pH, total organic carbon (TOC), and As chemical species in the porewater were determined. The abundance of the As methylation functional gene (

In this study, a newly synthesized sepiolite-supported nanoscale zero-valent iron (S-nZVI) adsorbent was tested for the efficient removal of As(III) and As(V) in aqueous solution. Compared with ZVI nanoparticles, the As(III) and As(V) adsorption abilities of S-nZVI were substantially enhanced to 165.86 mg/g and 95.76 mg/g, respectively, owing to the good dispersion of nZVI on sepiolite. The results showed that the adsorption kinetics were well fitted with the pseudo-second-order model, and the adsorption isotherms were fitted with the Freundlich model, denoting a multilayer chemical adsorption process. The increase in the initial solution pH of the solution inhibited As(III) and As(V) adsorption, but a weaker influence on As(III) than As(V) adsorption was observed with increasing pH. Additionally, the presence of SO42− and NO3− ions had no pronounced effect on As(III) and As(V) removal, while PO43− and humic acid (HA) significantly restrained the As(III) and As(V) adsorption ability, and Mg2+/Ca2+ promoted the As(V) adsorption efficiency. Spectral analysis showed that As(III) and As(V) formed inner-sphere complexes on S-nZVI. As(III) oxidation and As(V) reduction occurred with the adsorption process on S-nZVI. Overall, the study demonstrated a potential adsorbent, S-nZVI, for the efficient removal of As(III) and As(V) from contaminated water.

Mineral-organic associations (MOAs) are the basic structural units of soil aggregates and are important reservoirs of nutrients for plants and soil microorganisms, determining the soil structure and fertility. However, the influence of exogenous dissolved organic matter (DOM) chemistry on the stability of MOAs is rarely reported. We first characterized different exogenous DOM through elemental analysis and spectroscopy analysis technologies. Then, a chamber incubation experiment was conducted with DOM addition concentration at 3 g C kg−1 red soil. Principal component analysis, redundancy analysis, and the partial least squares path model were used to better understand the effect of exogenous DOM chemistry on the stability of MOAs. The addition of DOM into the red soil significantly increased not only the organic carbon both in the bulk soil and the soil heavy fraction, but also the soil combined humus and the soil mineral-organic compound quantity. Moreover, the rice straw-derived DOM had the best effect on improving the soil mineral-organic compound quantity/degree (additional), followed by the animal-derived DOM, while the fulvic acid increased it the least. The ratios of elements (C/N ratio, O/C ratio, and H/C ratio), aromaticity (SUVA254), and phenolic C content of exogenous DOM had positively significant contributions to the stability of MOAs. The rice straw-derived DOM had the greatest enhancement on the stability of the MOAs for its higher C/N ratio and phenolic groups content, so the exogenous DOM characteristics could be as an indicator in predicting the stability of the MOAs and evaluating the soil fertility.

This study was aimed at evaluating the effect of manure fertilization on organo-mineral complexes based on unfertilized (CK) and 5-year manure fertilization (M) in red soils (ultisols). Sequential density fractionation was adopted to obtain particular organic matter (POM, 2.6 (MOM> 2.6)), which were demineralized by hydrofluoric acid (HF). The HF-dissolved organic carbon (OC) was identified as mineral bound OC, and was characterized by comparing the band area of Fourier transform infrared spectroscopy before and after 10% HF demineralization. Manure fertilization significantly increased the OC and nitrogen contents of bulk soil, POM, MOM1.8–2.2, and MOM2.2–2.6, but did not affect MOM> 2.6. About 82.9–86.1% soil OC was retained by MOM1.8–2.2 and MOM2.2–2.6 dominated with iron (Fe) and aluminum oxides and phyllosilicates, in which HF-dissolved OC was significantly positively correlated with poorly crystalline (Feo) (R2 = 0.61, P 2.6 was composed of aromatic C, amide N, and polysaccharides, not being affected by fertilization. Our results suggested that manure fertilization promotes organo-mineral association, particularly for aromatic compound-Fe complexes, contributing to OC preservation in red soils.

Application of organic amendments is an effective approach for improving soil organic carbon and soil fertility. To investigate the effects of different organic amendments on soil organic carbon and its labile fraction content, a batch of incubation experiments was conducted on the fluvo-aquic soil in Dongting Lake region, Hunan Province. There were six treatments, including soil amended with rice straw, soil amended with Chinese milk vetch, soil amended with bio-organic fertilizer, soil amended with pig manure, and soil amended with rice straw-derived biochar, with unamended soil as control. Each treatment had the same amount of carbon input. After 180 days of incubation, application of organic amendments increased soil labile organic carbon content. Application of bio-organic fertilizer, pig manure and rice straw-derived biochar significantly increased soil organic carbon content by 26.1%, 9.7% and 30.7%, respectively. There was no significant change in soil organic carbon content in rice straw and Chinese milk vetch treatments which were more favourable to the accumulation of soil dissolved organic carbon and microbial biomass carbon. Pig manure was more favourable to the accumulation of soil dissolved organic carbon. Bio-organic fertili-zer could benefit the accumulation of soil microbial biomass carbon and readily oxidizable organic carbon. Rice straw-derived biochar could promote the accumulation of soil microbial biomass carbon and light fraction organic carbon. Compared with rice straw, soil carbon pool management index was increased by 31.8%, 111.6%, 62.2% and 50.7% in Chinese milk vetch, bio-organic fertilizer, pig manure and rice straw-derived biochar treatments, respectively. The performance of bio-organic fertilizer, pig manure, and rice straw biochar was better than rice straw and Chinese milk vetch from the perspective of soil carbon sequestration and soil carbon pool management index.有机物料还田是提升农田土壤有机碳、培肥土壤的重要措施。为探讨不同有机物料的还田效果,采用室外培养方法,研究了在等碳输入条件下,施用水稻秸秆、紫云英、生物有机肥、猪粪和水稻秸秆生物炭对洞庭湖双季稻区潮土有机碳和活性有机碳组分含量的影响。结果表明: 经过180 d的培养试验,与不施用有机物料相比,施用有机物料提高了土壤活性有机碳含量。生物有机肥、猪粪和水稻秸秆生物炭处理分别使土壤有机碳含量显著提升了26.1%、9.7%和30.7%,水稻秸秆和紫云英对土壤有机碳含量的提升效应在试验期间并不显著。水稻秸秆和紫云英还田更有利于土壤可溶性有机碳和微生物生物量碳的积累,猪粪更有利于土壤可溶性有机碳的积累,生物有机肥更有利于土壤微生物生物量碳和易氧化有机碳的积累,水稻秸秆生物炭则更有利于土壤微生物生物量碳和轻组有机碳的积累。与水稻秸秆还田相比,紫云英、生物有机肥、猪粪和水稻秸秆生物炭还田使土壤碳库管理指数分别提高了31.8%、111.6%、62.2%和50.7%。从土壤固碳和土壤碳库管理指数来看,生物有机肥、猪粪和水稻秸秆生物炭的还田效果优于水稻秸秆和紫云英还田。.

Dissolved inorganic nitrogen (DIN) adsorbed onto soil colloids plays an important role in soil N leaching, but previous studies have not clearly defined the mechanisms of this process in paddy soils under organic fertilization. In this study, we investigated how ongoing fertilization can change soil DIN leaching via affects on soil-surface electrochemical properties and physical properties, and the main influences of soil properties on DIN leaching were characterized. Five fertilization regimes applied during a 5-year field experiment were employed to study this mechanism, i.e., no fertilizer, chemical fertilizer, chemical fertilizer plus hog manure, hog manure, and chemical fertilizer plus oil cake. Increasing levels of applied manure decreased DIN leaching from the soil profile, especially for NH4+, the main form of DIN in the leachate and soil. Compared to chemical fertilizer, organic fertilization changed the surface electrochemical and physical properties more effectively with regards to decreased soil bulk density (9.84–20.49 %, P

Nitrifiers and denitrifiers are the key drivers of N cycling in paddy soil. Little is known about the effects of different fertilization methods, especially side bar fertilization, on the community of nitrifiers and denitrifiers in paddy soils. Here we assess the relationships between soil physicochemical properties, denitrification and nitrification activities, and the underlying microbial communities in a surface layer of paddy field soil treated with different fertilization methods. Soil was unfertilized (control), treated with conventional chemical fertilizer (CF), CF plus pig manure (MC), or slow-release fertilizer (SR), or by slow-release side bar fertilization (SB). Soil was sampled after one season of early and late rice growth. We determined soil physicochemical properties, potential nitrification rates (PNR), and denitrification enzyme activities (DEA). Ammonia-oxidizing archaeal (AOA) and bacterial (AOB) communities were assessed via their ammonia monooxygenase (amoA) genes, and denitrifiers via nitrite reductases (nirK and nirS) and nitrous oxide reductase (nosZ). Quantitative PCR was used to assess gene abundance, terminal restriction fragment polymorphism (T-RFLP) to investigate fertilization effects on microbial communities, and clone library sequencing and phylogenetic analysis to explore the taxonomic diversity of the nitrifiers and denitrifiers. Fertilization significantly increased the amount of NH4 +-N in the soil of SB and MC treatments, whereas MC lowered the NO3 −-N level. DEA was higher for MC and CF than the other treatments. The PNR in MC-treated soil was significantly lower than that in CF-treated soil. There were no significant differences in AOA and nirS copy numbers; however, nirK and nosZ copy numbers were higher for MC compared with CF. The number of AOA terminal restriction fragments (TRFs) increased significantly with N addition and reached the highest level for SB, whereas the number of AOB TRFs did not change significantly between treatments. Similarly, the number of nirK TRFs increased under fertilization, with the highest number obtained for SR; however, no significant change was observed for nirS and nosZ TRFs across different treatments, except for their relative abundance. All AOA amoA genotypes were in archaeal group 1.1b, whereas 95% AOB were in Nitrosospira cluster 3a. More than 40% of nirS OTUs were affiliated with Herbaspirillum, a key N-cycle player in this paddy soil. The SB and MC treatments had significant effects on soil N, DEA, and PNR levels, and affected the community of N-functional microbes. SB in combination with pig manure would contribute to the improvement of paddy soil fertility.

The article “Organic carbon preservation promoted by aromatic compound-iron complexes through manure fertilization in red soil”, written by Yunjie Wen et al., was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 12 September 2020 with open access.

One CuII complex, [Cu2(L)(pp)2(CH3OH)(ClO4)0.5]2(ClO4)·H2O (1), with mixed xanthene-9-carboxylate (L) and 3-(2-pyridyl)pyrazole (Hpp) ligands, was synthesized and characterized by single-crystal X-ray diffraction analysis. Complex 1 has a tetranuclear gridlike structure, which is further interlinked via intermolecular O–H···O and C–H···O hydrogen-bonding and π···π interactions to generate a 3-D supramolecular framework. The magnetic property of 1 was investigated, which exhibits strong antiferromagnetic interaction. The best agreement between simulated and experimental data was obtained for J1 = 275 cm−1, J2 = 150 cm−1, and g = 2.27.

Two new metal–organic frameworks (MOFs), namely [Zn2(L) (bpy)0.5(OH)]∞ (1) and {[Ni2(L)(bpy)(OH)(H2O)]·2H2O}∞ (2) (L = biphenyl-3,3′,5-tricarboxylate and bpy = 4,4′-bipyridine), have been prepared and structurally characterized. In 1, the eight-nuclear Zn8(μ2-OH)4(COO)12 secondary building units (SBUs) are linked by neighboring ones through L and bpy ligands to result in a (3,16)-connected three-dimensional (3D) network with the point symbol of (424.544.640.78.84)(43)4. Complex 2 is constructed from Ni–O–C 1D rod-shaped SBUs and organic linkers to lead to the formation of a (3,4)-connected 3D network with the point symbol of (42.6.83)2(83).

One new 3-D open lanthanide–organic framework {[La2(L)1.5(H2O)4]∙2.75H2O}∞ (1) (L = benzene-1,2,3,4-tetracarboxylate) was synthesized and characterized by elemental analyses, IR spectrum, and single-crystal X-ray diffraction, respectively. Notably, 1,2-naphthalenedicarboxylic anhydride can be turned into benzene-1,2,3,4-tetracarboxylate (L) ligand upon an in situ reaction process under hydrothermal conditions. L ligand exhibited two different types of carboxyl coordination modes in 1, and bridged the lanthanum atoms to form a 2-D bilayer and then a 3-D open framework with (4,5,6)-connected (42.84) (32.44.52.62)4(32.45.53.64.7)2 topology. Moreover, luminescent properties of 1 have also been investigated.

This work presents a mesoporous Dy(III) metal-organic framework with two types of void cages (diameters: 4.4 and 2.8 nm), which can efficiently adsorb a variety of chemical pollutants, including toxic metals, iodine, and formaldehyde.

Hydrothermal reaction of ZnII salt with cyanuric acid (H3CA) and 1,2,4-triazole (Htz) yields a unique coordination polymer [Zn9(CA)2(μ3-tz)3(μ2-OH)6(μ3-OH)3]n (1), which displays a 3-D (3,18)-connected topological network based on a new type of {Zn18} double-stranded metallacrown.

Five new Cu(ii) complexes have been prepared by employing 2,3-naphthalenedicarboxylic acid (H2ndc) and different N-donor co-ligands, namely, [Cu(ndc)(H2O)]n (1), [Cu(ndc)(H2O)2]n (2), {[Cu1.5(ndc)(OH)(H2O)2]·2.5H2O}n (3), {[Cu(ndc)(phen)(H2O)]·CH3OH}n (4) (phen = 1,10-phenanthroline), and {[Cu2(H0.5ndc)2(4bpy)3](ClO4)·2H2O}n (5) (4bpy = 4,4′-bipyridine). Complex 1 displays a two-dimensional (2D) (4,6)-connected (32.44)2(34.42.64.75)(34.43.64.74) coordination network. Complex 2 shows a 2D 3-connected hcb network which is further interlinked via the interlayered C–H⋯π interactions to result in a three-dimensional (3D) supramolecular network. Complex 3 is a one-dimensional (1D) coordination chain which is further interlinked by the C–H⋯π and π⋯π interactions to lead to the formation of the final 3D supramolecular network. When the N-donor co-ligands phen and 4,4′-bipyridine (4bpy) were introduced, the 1D complex 4 and the 4-connected sql layered complex 5 were constructed, respectively. The final supramolecular frameworks of 4 (2D) and 5 (3D) are extended by hydrogen-bonding and C–H⋯π interactions. The structural diversity of the complexes was triggered by different reaction conditions and N-donor co-ligands. Moreover, the magnetic properties of the complexes have also been investigated and discussed.