Search

Abstract: Amino sugars have been used as biomarker to indicate microorganism contribution to soil organic matter turnover and sequestration. However, there is no direct gas chromatograph mass spectrometry (GC/MS) approach to assess microbial synthesis of amino sugars in soil. We developed a novel method which combines laboratory incubation of substrate containing 15N or 13C and a GC/MS technique to trace 15N or 13C isotope changes in three amino sugars, glucosamine, galactosamine, and muramic acid. Sample preparation followed the procedure of Zhang and Amelung (1996) [Zhang, X., Amelung, W., 1996. Gas chromatographic determination of muramic acid, glucosamine, galactosamine, and mannosamine in soils. Soil Biology and Biochemistry 28, 1201–1206.]. The GC/MS determination was conducted using a full scan mode with both electronic ionization (EI) and chemical ionization (CI) sources. The CI source was suitable for all of the three amino sugars, while the EI source was not applicable to muramic acid due to its low sensitivity in the determination as well as low concentration of muramic acid in soil. The enrichment of 15N or 13C in amino sugars during incubation was estimated by calculating the atom percentage excess (APE). 15N incorporation was evaluated according to fragment (F) abundance ratio of mass F+1 to F, whilst 13C incorporation was estimated according to the ratio of mass F+n to F (n is skeleton carbon number in the fragment). This novel method was assessed by using two soil samples (a Kandiudult and a Udoll) incubated with either 15N-amonium or U-13C-glucose. The results indicate that the GC/MS determination is reproducible, thus this technique is useful in detecting the microbial synthesis of amino sugars in soil, and especially it should be possible when looking at the position or how much labeled carbon and nitrogen atoms have been incorporated. [Copyright &y& Elsevier]

Introduction: While no tillage (NT) can significantly influence soil structure stratification compared to conventional tillage (CT), a comprehensive understanding of the degree of root trait plasticity and trade-offs of lateral roots of crops at various growth stages along a deep soil profile in response to NT remains elusive. This knowledge gap is important for understanding soil resource acquisition strategies and yield of crops., Methods: We systematically investigated the traits of lateral roots at jointing and flowering stages in a long-term (12 years) experiment in Northeast China where maize ( Zea mays ) has been continuously planted under CT and NT with or without maize residue mulch on soil surface. We also measured soil penetration resistance and bulk density., Results: Soil penetration resistance was reduced at the jointing stage, and was increased at the flowering stage under NT especially at a depth of 10 - 40 cm. Root length density decreased under NT across the two growth stages by on average 22%. In contrast, specific root length and diameter showed greater plasticity, ranging from -14% to 20% and from -11% to 8%, respectively, relative to those under CT., Discussion: These responses could be attributed to changes in root length proportions with different diameters associated with differences in soil penetration resistance between tillage practices. The negative relationships between root traits were stronger under CT than NT, and became weaker from the jointing stage to the flowering stage. To the best of our knowledge, for the first time, our study provides empirical evidence for pivotal root trait plasticity and trade-offs across growth stages as key indicators of changes in soil structure and resources in response to NT. These insights contribute to a better understanding of soil resource acquisition strategies of crops under NT., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yin, Lv, Wang and Xie.)

Conservation tillage is widely used in farmland management for soil carbon sequestration, but it can also lead to potential emissions of nitrous oxide (N 2 O). Therefore, our study is aimed to investigate the effects of 15 years of no-tillage combined with four straw mulching levels of 0 % (NT0), 33 % (NT33), 67 % (NT67), and 100 % (NT100) compared to ridge tillage (RT) on the rates of N 2 O and N 2 emissions and the respective contributions of four microbial pathways to N 2 O emissions. The incubation experiments were conducted at two different moisture levels (55 % and 100 % WFPS) by using dicyandiamide inhibition and 15 N-labeling techniques. Soil samples were collected from the 0-20 cm and 20-40 cm soil depths across three maize growth stages: seedling, jointing, and maturity. Our results showed that conservation tillage significantly decreased the N 2 O + N 2 emission at 55 % WFPS, but it has a reverse influence in N 2 O + N 2 emission at 100 % WFPS. The proportion of N 2 O in gaseous N loss were higher at 100 % WFPS than at 55 % WFPS. Among the four microbial pathways for N 2 O emissions, autotrophic nitrification was the dominant pathway 55 %WFPS. The contribution of autotrophic nitrification remarkably decreased, co-denitrification and denitrification increased at 100 %WFPS. Overall, at 100 % WFPS, N 2 O emissions from all major microbial pathways were positively correlated with GWC, temperature, TC, TN, NH 4 + -N, and NO 3 - -N, but negatively correlated with soil pH and C/N ratios. Our results suggest that long-term conservation tillage increases N 2 O and N 2 emissions from the soil under water-saturated conditions by regulating soil nutrient levels, soil moisture, and microbial pathways. Therefore, we should consider the impact of conservation tillage on N 2 O emission risk when we attach importance to the role of conservation tillage in improving soil quality and increasing crop yields., Competing Interests: Declaration of competing interest No conflict of interest exits in the submission of this manuscript., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Exogenous carbon turnover within soil food web is important in determining the trade-offs between soil organic carbon (SOC) storage and carbon emission. However, it remains largely unknown how soil food web influences carbon sequestration through mediating the dual roles of microbes as decomposers and contributors, hindering our ability to develop policies for soil carbon management. Here, we conducted a 13 C-labeled straw experiment to demonstrate how soil food web regulated the residing microbes to influence the soil carbon transformation and stabilization process after 11 years of no-tillage. Our work demonstrated that soil fauna, as a "temporary storage container," indirectly influenced the SOC transformation processes and mediated the SOC sequestration through feeding on soil microbes. Soil biota communities acted as both drivers of and contributors to SOC cycling, with 32.0% of exogenous carbon being stabilizing in the form of microbial necromass as "new" carbon. Additionally, the proportion of mineral-associated organic carbon and particulate organic carbon showed that the "renewal effect" driven by the soil food web promoted the SOC to be more stable. Our study clearly illustrated that soil food web regulated the turnover of exogenous carbon inputs by and mediated soil carbon sequestration through microbial necromass accumulation., (© 2023 John Wiley & Sons Ltd.)

Ship recognition using synthetic aperture radar (SAR) images has important applications in the military and civilian fields. Aiming at the problems of the many model parameters and high-energy losses in the traditional deep learning methods for the target recognition in the SAR images, this study has proposed a high-efficiency and low-energy ship recognition strategy based on the spiking neural network (SNN) in the SAR images. First, the visual attention mechanism is used to extract the visual saliency map from the SAR image, and then the Poisson encoder is used to encode it into a spike train, which can suppress the background noise while retaining the visual saliency feature of the SAR image. Besides, an SNN model integrating the time-series information is constructed by combining the leaked and integrated firing spiking neurons with the convolutional neural network (CNN), which can use the firing frequency of the spiking neurons to realize the ship recognition in SAR images. Finally, to solve the problem that SNN model is difficult to train, the arctangent function is used as the surrogate gradient function of the spike emission function during the backpropagation. Hence, applying this backpropagation method to the training process can optimize the SNN model. The experimental results show the following: (1) the proposed strategy can more accurately recognize the ship in the SAR image, and the F1 score can reach 98.55%, which has a better recognition performance than the other traditional deep learning methods; (2) the proposed strategy has the least amount of model parameters (only 3.11MB), which is far less than the model parameters of the other traditional deep learning methods; (3) the proposed strategy has fewer operations (only 17.97M) and can reach 1/30 time of operands of the other traditional deep learning methods, which shows the high efficiency of the proposed strategy using the spike emission signals; (4) the proposed strategy has the energy loss of 1.38 × 10 -6 J, which can achieve the low energy advantage of nearly three orders of the magnitude compared to the other traditional deep learning methods, indicating that the proposed strategy has a significant energy efficiency., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Xie, Jiang, Hu, Wu, Wang and Xie.)

Currently, global agricultural development is in a critical period, as it contends with a growing population, degraded farmland, and serious environmental issues. Although low-disturbance practices are recommended to improve soil health, it is unclear whether such practices benefit critical deep soil functioning. Here, we compared the soil bacterial communities and physicochemical parameters across 3-m deep soil profiles in a Mollisol of Northeast China at the end of the dormant season after 10 years of farming under conventional tillage without stover mulching (CT), no-tillage without stover mulching (NTNS), and no-tillage with stover mulching (NTSM). We found that low-disturbance practices (NTNS and NTSM), compared with CT, evidently promoted soil bacterial species richness and diversity and enriched potential metabolic diversity. When compared to the bacterial communities in CT, the vertical dissimilarity of bacterial communities in NTNS decreased, while that in NTSM increased, indicating that no-tillage alone homogenized the composition of the bacterial community through soil depth profiles, but straw mulching enhanced the uniqueness of community composition at each layer. In comparison to CT, no-tillage with stover mulching significantly increased the soil water content and root-associated organic carbon (SEOC), and decreased soil pH. Mineral nitrogen declined with depth to 60 cm and then increased to its maximum at 250-300 cm under CT and at 120-150 cm under NTNS and NTSM. More mineral nitrogen at 0-150 cm under low-disturbance practices would provide more available nitrogen for crops in the coming growing season, while the accumulated nitrogen at 150-300 cm under CT may leach into the groundwater. Taken together, our results show that low-disturbance practices can regenerate whole-soil bacterial diversity and potential function, and promote water retention and nitrogen holding capacity within the root zone, thus reducing the dose of nitrogen fertilizer and mitigating nitrogen contamination to deep groundwater, ultimately contributing to agricultural sustainability in Mollisol regions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Terrestrial species are predicted to migrate northward under global warming conditions, yet little is known about the direction and magnitude of change in microbial distribution patterns. In this continental-scale study with more than 1600 forest soil samples, we verify the existence of core microbiota and lump them into a manageable number of eco-clusters based on microbial habitat preferences. By projecting the abundance differences of eco-clusters between future and current climatic conditions, we observed the potential warming-driven migration of the core microbiota under warming, partially verified by a field warming experiment at Southwest China. Specifically, the species that favor low pH are potentially expanding and moving northward to medium-latitudes (25°-45°N), potentially implying that warm temperate forest would be under threat of soil acidification with warming. The eco-cluster of high-pH with high-annual mean temperature (AMT) experienced significant abundance increases at middle- (35°-45°N) to high-latitudes (> 45°N), especially under Representative Concentration Pathway (RCP) 8.5, likely resulting in northward expansion. Furthermore, the eco-cluster that favors low-soil organic carbon (SOC) was projected to increase under warming scenarios at low-latitudes (< 25°N), potentially an indicator of SOC storage accumulation in warmer areas. Meanwhile, at high-latitudes (> 45°N) the changes in relative abundance of this eco-cluster is inversely related with the temperature variation trends, suggesting microbes-mediated soil organic carbon changes are more responsive to temperature variation in colder areas. These results have vital implications for the migration direction of microbial communities and its potential ecological consequences in future warming scenarios., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2021 Science China Press. Published by Elsevier B.V. All rights reserved.)

Determination of amino acids by mass spectrometry (MS) is an important technique to investigate soil nitrogen transformation and cycling as amino acids being the major nitrogen-containing compounds in soil organic matter. However, researchers have long faced a critical problem in coupling an efficient separation technique to a sensitive MS detection system simultaneously. In this context, we established a new method of liquid chromatography coupled to mass spectrometry based on the 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatization method for convenient and accurate quantification of amino acids in soil samples. Baseline separation of 17 amino acid AQC-derivatives was achieved on an XTerra(R) MS C(18) column using ammonium formate as a mobile phase modifier. The concentration of ammonium formate and the pH of the mobile phase were optimized in order to obtain sensitive MS signals. The response curves were linear over the range of 50-800 micromol L(-1) amino acids. The detection limits were 0.20-0.60 pmol microL(-1) on column and 0.07-0.24 microg g(-1) soil under the optimized conditions. The method has been applied successfully for the first time to determine amino acids in 4 types of soil samples, in which 15 amino acids were quantified by MS detector but methionine and cystine were below the detection limits. Both the recovery and the precision were satisfactory. Hence, this proposed technique shows a potential for the identification of amino acids in soil as well as tracing the transformation of soil amino acids with isotope dilution technique in nitrogen cycling investigation.

Soil carbohydrates are the important component of soil organic matter, and play an important role in soil aggregation formation. Their hydrolysis methods involve sulfur acid (H2SO4), hydrochloric acid (HCl), and trifluoroacetic acid (TFA) hydrolysis, and their determination methods include colorimetry, gas-liquid chromatography (GLC) , high performance liquid chromatography (HPLC), and high performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). This paper summarized the methods of carbohydrates' hydrolysis, purification and detection, with focus on the derived methods of GLC, and briefly introduced the indication functions of carbohydrates in soil organic matter turnover.

Using encapsulation techniques to coat easily soluble fertilizers is an important way to improve fertilizer use efficiency while reduce environmental hazards. Based on a wide range of literature collection on coated fertilizer research, the theories, processes, and characters of nutrient controlled-release from coated fertilizer were discussed, and the factors affecting nutrient controlled-release and the mathematical simulations on it were reviewed. The main tendencies related to this research in China were also put forward.

In modern study of soil organic matter, many new quantificational indexes and relevant testing methods, e.g., DOC, WSOC, HWC, ROC, MBC, MBN, PMC, PMN, Glu, Gla, Man, Mur, delta 13C, and CPMI, came forth with deepening study. Because they are disorderly and unsystematic, it is necessary to clarify these indexes. This paper summarized their origin, concept, and testing method, which is of significance in the modern study of soil organic matter.

The effects of applying nitrogen fertilizer in ploughed furrow at different stages on dry matter production and yield of rice were studied in a field experiment in 1999. The results showed that applying N fertilizer at booting stage (BS) had better effects on dry weight (2.9 g.hill-1) of leaf, stem and whole plant than at panicle primordia formation stage (PPFS), tillering stage (TS) and regular N fertilization (RF). Meanwhile, the dry weight of leaf and sheath as well as the leaf area index (LAI, 8.9) could be maintained at a high level for a relative long time in BS treatment, compared with PPFS, TS and RF treatments. Similar phenomenon was observed in the growth velocity (0.73 g.d-1.hill-1) of stem and whole plant, and the dry weight (10434 kg.hm-2) of seed. The grain yield of rice followed the sequence of BS > or = PPFS > TS > or = RF. Thus, the optimum stage of applying N fertilizer in ploughed furrow was the booting stage.