典型土壤动物体表形态减粘脱土的初步研究

土壤动物的不粘土特性,对于地面机械减粘脱土的仿生研究具有重要意义。本文利用实体显微镜和扫描电镜对典型土壤动物穿山甲、蝼蛄、蚂蚁和蜣螂等的体表形态进行了观察研究。结果表明,上述土壤动物具有类似波纹状的体表结构,并用波形表面模型进行了减粘脱土的机理分析。     

土壤粘附仿生研究(二) 典型土壤动物体表形态减粘脱土的初步研究

土壤动物的不粘土特性,对于地面机械减粘脱土的仿生研究具有重要意义。本文利用实体显微镜和扫描电镜对典型土壤动物穿山甲、蝼蛄、蚂蚁和蜣螂等的体表形态进行了观察研究。结果表明,上述土壤动物具有类似波纹状的体表结构,并用波形表面模型进行了减粘脱土的机理分析。     

土壤动物减粘脱土规律初步分析

在土壤中生活的许多动物经过亿万年的进化优化,具有减粘脱土的特殊功能。本文对七种典型土壤动物进行了实际观察和体表测试分析,初步探讨了土壤动物的减粘脱土规律,并对地面机械仿生减粘脱土研究提出了初步设想。     

蚯蚓体表液的组成及其减粘脱土机理分析

蚯蚓的体表液利于减粘脱土。本文利用现代测试仪器,结合生物化学分析技术,研究了蚯蚓体表液和泥鳅分泌液的组成;并应用土壤力学和生物化学等方面的理论,初步探讨了蚯蚓体表液减粘脱土的机理。     

非光滑表面电渗轮脚减粘脱土的试验研究

非光滑表面电渗方法是有效解决土壤对地面机械触土部件粘附问题的较好方法之一。应用这一方法,研制了非光滑表面电渗轮脚,并进行了减粘脱土试验。试验表明,非光滑表面电渗轮脚具有良好的减粘脱土效果,并可提高牵引力和驱动效率。     

非光滑表面电渗减粘脱土原理的试验研究

在土壤动物减粘脱土机理研究的基础上,提出了一种有效解决土壤对地面机械触土部件粘附问题的新方法—非光滑表面电渗减粘降阻技术,并对其减粘脱土效应及规律作了基础性研究,同时设计并优化了非光滑表面电渗极板面积。     

柔性非光滑减粘脱附的自卸车模型试验研究

在柔性非光滑典型生物体表的仿生研究基础上，提出了一种自卸车装卸粘性土时解决其减粘脱附问题的新方法—柔性仿生减粘技术，对其减粘脱附作用进行了模型试验研究，优选了柔性仿生减粘技术方案，为在自卸车上的应用试验奠定了基础。     

地面机械减粘脱土方法的研究

本文综合论述了国内外关于地面机械减粘脱土的方法,并在分类评述的基础上,提出了今后发展方向。     

犁壁材料表面特性与土壤粘附间的关系

选取机引犁壁和畜力犁壁，研究其表面特性与土壤粘附间的内在联系。首次将材料的土壤粘附特性与表面电化学现象联系起来，从理论与试验的结合上证明提高材料的耐蚀性有利于金属材料表面减粘脱土，为触土部件的材料选取、成分优化以及铁基减粘材料的研制提供了简捷有效的参考指标和理论依据     

蚯蚓体表液收取方法的初步研究——地面机械减粘脱土仿生研究之一

蚯蚓是一种典型的土壤动物,在土壤中生活而很少粘土。它的体表有一薄层多组分混合的液体,对减粘脱土起一定作用,但由于量少且难于收取,给仿生减粘研究,带来较大困难。经初步探索,本文首次提出利用电刺激法、转移法和浸泡法,可有效收取到足量的体表液,为研究蚯蚓体表液创造了良好的基础条件。     

Rapid and sensitive quantification of amino acids in soil extracts by capillary electrophoresis with laser-induced fluorescence

A growing body of research is arguing that amino acids are key components of the soil nitrogen cycle. For example, we now know that many plants can take up intact amino acids, even in competition with soil microbes. Our growing recognition of the importance of amino acids is not matched by knowledge of the amounts and type of amino acids in the soil, certainly not in comparison with our encyclopaedic knowledge of inorganic N. The primary reason that less is known about amino acids than inorganic N is that measuring the amounts of individual amino acids with conventional chromatographic techniques is slow and typically requires extensive sample clean-up if KCl extracts are analysed. The aim of this study was to develop capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) as a more rapid alternative for measuring individual amino acids in KCl extracts of soil. The CE-LIF method separated 17 common amino acids within 12 min, with detection limits between 7 and 250 nM. One molar KCl extracts could be analysed without any sample clean-up or de-salting, and spike and recovery tests indicated that the complex matrix of soil extracts did not affect quantification. Further evidence of the suitability and robustness of the method came from the repeated analysis (n=5) of the same soil KCl extract. The relative standard deviation of migration times for replicate analyses were <0.2% while relative standard deviations for peak areas were <5%. To demonstrate application of the CE-LIF method to real world problems it was used to analyse amino acids in 1 M KCl extracts from a sub-alpine grassland and a Eucalyptus regnans forest. The most abundant amino acids were Ala, Gly and Arg. Other amino acids present at smaller concentrations or in a minority of samples were Asn, Cit, GABA, Glu, His, Phe, Leu, and Lys. The proposed CE-LIF method offers significant advantages over chromatographic methods via its rapidity, reproducibility and, most importantly, its ability to analyse crude KCl extracts.     

Amino acids in Quaternary soil horizons from southwest Poland

Aminostratigraphy has proved to be a useful approach for dating fossils from the Quaternary. In these studies the amino acids in Quaternary soil formations were determined in an attempt to establish their stratigraphical relationships and relative ages. The sampling sites are in the southwest of Poland, in the Trzebnickie Hills. Three samples of fossil soils and two of recent soils were analysed. The absolute age of the soil samples was estimated by radiocarbon dating. We found that the total amount of amino acids decreased with the increasing age of soil. The smallest amounts of amino acids were found in the oldest fossil soil of Denekamp (Vistulian) age dated 29 600 ± 760 years bp . A sample of recent loess soil contained the most total amino acids, whereas the fossil soil of Lower Atlantic age, dated 3540 ± 230 years bp , was intermediate in respect of the total amount of amino acids, oxidation state and degree of biochemical transformation. Neutral amino acids formed a majority of all the amino acids studied. The method we describe could be useful in relative chronostratigraphical identification of fossil soils.     

Amino Acids, Total Organic and Inorganic Nitrogen in Forest Floor Soil Solution at Low and High Nitrogen Input

It is now widely accepted that many plants and mycorrhizal fungi have the ability to take up organic nitrogen (N) in the form of amino acids, although the importance of this uptake in the field is less clear. In the laboratory it has been shown that uptake affinity and uptake kinetics of ammonium and some amino acids are comparable. The relative uptake of either N form from the soil solution would thus be related to the relative concentration in the soil solution accessed by roots. We sampled soil solution from the F- and H-layers under a Spruce stand in a fertilisation experiment in Flakaliden, northern Sweden. Tension lysimeters were installed in plots receiving irrigation (I) or irrigation plus liquid fertilisation (IL). The soil solution samples were analysed for ammonium, nitrate, free amino acids, hydrolysable amino acids, total organic N and total organic C. In I plots the concentrations of both ammonium and free amino acids were very low with no obvious dominance of either form. In IL plots inorganic N concentrations were higher and amino acid concentrations were lower compared to I plots, and thus the inorganic N dominated over amino acids. There was no difference in H-layer ammonium concentration between I and IL plots despite the high N addition rate on the soil surface during nights of sampling. The lower amino acid concentrations in IL plots might be an effect of a decreased proteolytic activity due to the documented shift in mycorrhizal fungi species composition at the site.     

A comparative study on the chemical composition of humic acids from forest soil,agricultural soil and lignite deposit: Bound lipid,carbohydrate and amino acid distributions

Base- and acid-hydrolysable fractions of humic acids (HAs) isolated from a forest soil, an agricultural soil and a lignite deposit were analysed, and comparisons were made between the base hydrolysable lipid (bound lipid), carbohydrate and amino acid signatures of the different humic acids.Bound lipids differ depending on the humic acid origin. Their composition were rather similar for the two soil humic acids, with three main lipid classes identified: (i) aliphatic components, (ii) aromatic components and (iii) sterols and triterpenols. The aliphatic subfraction was the most abundant and consisted predominantly of cutin- and suberin-derived moieties some of which could be clearly related to the vegetation. A minor bacterial input was indicated by the presence of short chain α- and β-hydroxyalkanoic acids. Aromatic subfraction contributed to a low amount to the total base hydrolysates and consisted mainly of lignin-derived methoxyphenols. Present in trace amounts, sterols and triterpenols are mainly of higher plant origin. The base hydrolysate from lignite humic acid markedly differs. Bound lipids released from lignite HA comprised almost exclusively aliphatic components, largely dominated by long chain alkanoic acids. Lignin-derived moieties, hardly detected, consisted solely of vanillic and 4-hydroxybenzoic acids indicating a much higher degree of lignin alteration in lignite humic acid. Sterols and triterpenols were absent.Although the composition of monosaccharides released upon acid hydrolysis was rather uniform irrespective of the humic acid origin, the distribution changed with the degree of humification of the HAs. Ratios of (Galactose+Mannose) to (Xylose+Arabinose) increased from soil to lignite humic acids. The high values of the ratios indicate that carbohydrates are primarily of microbial origin.In all humic acids neutral and acidic protein amino acids dominated. Non protein amino acids were only minor components consisting mainly of hydroxy proline and ornithine. The amino acid distributions of both soil HAs were similar. The amino acid distribution of lignite HA resembled that of soil HAs except for the following differences: (1) the absence of hydroxy proline and the greater abundance of ornithine suggesting a higher microbial contribution to the amino acids as the degree of humification increases, (2) the higher contribution of polar amino acids suggesting a preferential preservation of these amino acids possibly by interaction with the humic acid surface through hydrogen bonds.     

Differentiating the mineralization dynamics of the originally present and newly synthesized amino acids in soil amended with available carbon and nitrogen substrates

Newly synthesized amino acids are the principle compounds created after inorganic nitrogen (N) is rapidly immobilized into microbial tissues. However, little is known about the mineralization kinetics of these newly synthesized amino acids compared to the amino acids originally present in the soil, and how substrate availability controls their mineralization. With ¹⁵N isotope tracing, the newly synthesized (¹⁵N-labeled) amino acids can be differentiated from the amino acids originally present (unlabeled) in soil, making it possible to evaluate the mineralization of the newly synthesized amino acids in tandem with the original amino acids. As amino acids can serve as both N and carbon (C) sources for microorganisms, the mineralization dynamics of amino acids may be manipulated by the availability of extraneous C and N. In this study, an aerobic 30-week intermittent leaching experiment was conducted, using glucose as C source and (¹⁴NH₄)₂SO₄ as N source, following separate additions to soil. The newly synthesized amino acids were determined by an isotope-based high performance liquid chromatography/mass spectrometry (HPLC/MS). The newly synthesized soil amino acids mineralized faster than the original ones, which indicated more rapid cycling of N in the newly synthesized soil amino acids pool. Glucose addition significantly decreased the mineralization of both the newly synthesized and the original amino acids. However, when inorganic N was abundant, the newly synthesized amino acids decomposed rapidly, and preferentially as a C source and energy, while N addition inhibited the mineralization of the original amino acids in the soil. We conclude that the presence of readily degradable C (e.g. glucose) and inorganic N controls the mineralization of newly synthesized and original amino acid pools in soil differently, which is a crucial mechanism in adjusting the N supply and sequestration processes in soil ecosystems.     

Plant species affect the concentration of free sugars and free amino acids in different types of soil

Substantial amounts of low molecular weight organic compounds (LMWs) such as sugars and amino acids are transferred from plant roots into soil. These substances are released due to decomposition processes or leaching (exudation). Afterwards they can be metabolized by soil microorganisms into different compounds, or they can be partially re‐absorbed by the plants. The aim of this study was to clarify the influence of five wild plant species on the composition and pool sizes of LMWs extractable from three different soils. Four of the five species caused significant changes in soil LMW pools. In Chernozem, the sugar concentrations of soil with plants were up to 60 % higher than those of the bulk reference soil, and amino acids increased by as much as 207 %. The relative abundance of free amino acids in roots did not correlate with the relative abundance of amino acids in soil after six weeks of plant growth. The relative abundance of soil amino acids, that increased after plant growth, was strongly dependent on the type of soil and on the plant species present. We suggest that rather than rhizodeposition being dependent on soil type, it reflects differential microbial metabolization of amino acids in the respective soils.     

Control of amino acid mineralization and microbial metabolism by temperature

Amino acids constitute a major reserve of soil organic-N and studies demonstrating direct uptake of amino acids by plants has indicated that understanding their bioavailability and fate in soil is important to understanding terrestrial N cycling. The aim of this study was to determine the effects of temperature and sorption on the mineralisation of three amino acids (glycine, lysine glutamate) in soil. Amino acid sorption followed the series lysine>glycine>glutamate, whereas mineralisation rate followed the series glutamate>glycine>lysine. These observations support the concept that sorption reduces the bioavailability of amino acids to the soil microbial population. Although the amino acids were used preferentially for making new biomass rather than respiration, differences were apparent between the individual amino acids with microbial assimilation efficiency (biomass production) following the series, lysine>glycine>glutamate. Our results suggest divergences in the uptake and metabolism of the individual amino acids with a rapid mineralisation of amino acids which readily enter general metabolic cycles (e.g. glutamate) compared to the amino acids which typically form the terminus of metabolic pathways (e.g. lysine). Temperature significantly affected the rate of amino acid mineralisation which increased up to 30°C (Q₁₀=2.0) followed by a decline as the temperature approached 40°C. Rapid mineralisation occurred even at very low temperatures (1°C). Amino acid mineralisation across three experimental soil treatments followed the trend acidified>control>eroded soil. In summary, the results indicate that mineralisation is highly amino acid species dependent, has a mesophilic optimum, is retarded by sorption and is most rapid in soils which are not degraded.     

Nitrogen compounds in soil solutions of agricultural land

Plants are capable of taking up nitrogen (N) in both organic and inorganic forms, so the concentrations and relative proportions of different N forms in soils are likely to be important determinants of their N nutrition. Therefore, there is a need for greater knowledge of the N profiles of soils. In the study presented here we examined the potential plant-available N in soils from four sites with various agricultural histories (one recently fertilized), using small tension lysimeters to collect free and bound amino acids and inorganic N forms in solution, with minimal soil disturbance and with intact plants present. Subsequent analysis showed that concentrations of free amino acids ranged from 0.1 to 12.7 μM, whereas concentrations of bound amino acids were on average 50 times higher, and higher than ammonium and nitrate concentrations in all three unfertilized soils. In contrast, nitrate strongly dominated in the fertilized soil. Bound amino acids are likely to represent a potential replenishment pool for free amino acids, so the abundance and rate at which amino acid-containing substances are depolymerized might be important determinants of the availability of free amino acids. Our results highlight the need for further research on the liberation of free amino acids from polymers in agricultural soil, and the importance of bound amino acids as N sources for plants.     

玉米不同生长时期土壤氨基酸氮的动态特征

氨基酸在土壤氮素循环及作物养分供给中既扮演着库的角色又起着源的作用。本文通过田间试验研究肥料施用及肥料与秸秆配施后土壤氨基酸在玉米不同生长时期的数量变化,探讨了土壤氨基酸的可利用性及其动态特征。研究发现,在玉米需氮高峰期,耕层土壤,尤其是10～20 cm层次的氨基酸氮含量降低以部分满足植物的氮素需求;在玉米成熟期,土壤氨基酸含量又有所回升。秸秆配施增加了土壤氨基酸氮的含量,从而提高了土壤持续供氮能力。     

Free and HF-HO-extractable amino acids determined by high performance liquid chromatography in a loamy sand soil

Summary Amino acids were extracted from fertility plots of a loamy sand soil with 0.05 M HF-HCl and with a 10% ethanol solution (free amino acids) and analysed by reverse-phase high performance liquid chromatography (HPLC). The total quantities of amino-N compounds analysed were 4.4 g/g soil for the acid treatment and 22.6 g/g soil for the 10% ethanol extract. Glycine and glutamic acid were the most abundant of 15 amino-N compounds in the HF-HCl extracts, whereas glutamic acid and ornithine + NH⁺ ₄ were found in the highest concentration in the 10% ethanol extracts. The HF-HCI pretreatment is used to increase the efficiency of the extraction of soil organic matter. Although this pretreatment removed some amino acids, the acids extract less than 1% of the total amino-N content of the crude soil extracts. The pretreatment, therefore, was not overly destructive. Comparisons between the amino acids extracted from the fertility plots were not conclusive, except for glycine, which was greater in concentration in the higher fertilizer N plots of the same crop rotation.