Electrophoretic subfractionation of low and high molecular weight humic acids fractions

Summary Soil humic acid was fractionated on a molecular weight basis either using Sephadex gel filtration or electrophoresis on a discontinuous polyacrylamide gel. Low and high molecular weight fractions obtained by these two methods were choosen for subsequent subfractionation using electrophoretic methods. The high and low molecular weight fractions yielded several subfractions after separation by isotachophoresis or isoelectric focusing. Components of the high molecular weight fractions occupied the upper portion of the mobility train; components of the low molecular weight fractions lead the mobility train. Adsorption by Sephadex was avoided by using 4M urea as an eluent. The elution of the humic substances adsorbed to the polyacrylamide gel matrix was achieved by using a 0.1M Tris –0.025M EDTA solution.     

Modelling the production and transport of dissolved organic carbon in forest soils

DyDOC describes soil carbon dynamics, with a focus on dissolved organic carbon (DOC). The model treats the soil as a three-horizon profile, and simulates metabolic carbon transformations, sorption reactions and water transport. Humic substances are partitioned into three fractions, one of which is immobile, while the other two (hydrophilic and hydrophobic) can pass into solution as DOC. DyDOC requires site-specific soil characteristics, and is driven by inputs of litter and water, and air and soil temperatures. The model operates on hourly and daily time steps, and can simulate carbon cycling over both long (hundreds-to-thousands of years) and short (daily) time scales. An important feature of DyDOC is the tracking of ¹⁴C, from its entry in litter to its loss as DO¹⁴C in drainage water, enabling information about C dynamics to be obtained from both long-term radioactive decay, and the characteristic ¹⁴C pulse caused by thermonuclear weapon testing during the 1960s ("bomb carbon"). Parameterisation is performed by assuming a current steady state. Values of a range of variables, including C pools, annual DOC fluxes, and ¹⁴C signals, are combined into objective functions for least-squares minimisation. DyDOC has been applied successfully to spruce forest sites at Birkenes (Norway) and Waldstein (Germany), and most of the parameters have similar values at the two sites. The results indicate that the supply of DOC from the surface soil horizon to percolating water depends upon the continual metabolic production of easily leached humic material. In contrast, concentrations and fluxes of DOC in the deeper soil horizons are controlled by sorption processes, involving comparatively large pools of leachable organic matter. Times to reach steady state are calculated to be several hundred years in the organic layer, and hundreds-to-thousands of years in the deeper mineral layers. It is estimated that DOC supplies 89% of the mineral soil carbon at Birkenes, and 73% at Waldstein. The model, parameterised with "steady state" data, simulates short-term variations in DOC concentrations and fluxes, and in DO¹⁴C, which are in approximate agreement with observations.     

Gel filtration and absorption spectroscopic investigations on humic substances from organic fertilizers

Summary Three organic fertilizers: a farmyard manure (FYM), humified poplar barks (PBF) and spruce barks (SBF) were investigated by means of chemical analysis and by the study of humic substances extracted by 0.1M sodium pyrophosphate (pH=10.0). The organic carbon content and the C/N ratio were higher in SBF, probably as a consequence of the short fermentation period (5 months). Yields of organic substances removed by three consecutive extractions with Na₄P₂O₇ solution were in the order: PBF>FYM>SBF. Nominal molecular weight distribution of total extracts was studied using Sephadex G type gels; TRIS buffer (pH=9.0) was the eluant, since the use of water produced complex gel-solute interactions. It was shown that SBF had a higher content of small size particles than the other two products which exhibited quite similar elution curves. Slopes of log A(absorbance)vs log plots and ratio of absorbances at 465 and 665 nm (E₄/E₆) of fractions containing particle of lower size were the steepest and the highest, respectively.     

Control of sclerotium of sunflower through organic amendments of soil

Summary Out of six organic materials used to amend the infested soil for the control of Sclerotium wilt of sunflower, oat straw followed by oil cakes such as castor andneem cakes significantly reduced the incidence of the disease when compared with non-amended soil. Rice-husk and sawdust did not show any consistent and definite trend in influencing the disease incidence.Publication No. 2041 under the Journal Series of the Experiment Station, G.B. Pant Univ. of Agri.^±Techn., Pantnagar, Nainital (U.P.). India.     

Nature and properties of humic acid prepared from different sources and its effect on nutrient availability

Summary Effect of sources, moisture levels and extractants on extraction, analytical properties, IR-spectra, macromolecular characteristics, interaction with cations and physiological properties of the extracted material (humic acid) were studied. Among the three variables, extractant influenced the degree of humification, IR-spectra, nature and properties of humic acids to a greater extent though the other two had significant contribution. Sodium pyrophosphate found to be an ideal extractant for humic acid. Reduced viscosity of humic acids increased with dilution particularly below 0.1 g/dl and decreased with increasing H⁺ concentration between pH 6.5 and 8.5 irrespective of source, moisture level and extractant. The amount of proton released and drop in initial pH of humic acids on addition of different metal ions indicated formation of mono-, di-hydroxy metal-HA complexes which broke down at pH 8.0 and above. HA-Fe²⁺ and HA-Cu²⁺ complexes were found to be most stable. Humic acids from different sources varied significantly in their effect on available nutrient status of soils though, the latter is main determining factor particularly for calcium and magnesium.     

土壤有机污染植物修复的机理与影响因素

在综述大量国内外文献的基础上,分析了土壤有机污染植物修复的机理,重点介绍了国内外在植物吸收转运、植物根际降解和植物修复模型的研究进展。同时,从污染物的物理化学性质、植物种类、土壤性质、共存有机物和气象条件5个方面分析了影响土壤有机污染植物修复的主要因素,并展望了该领域的研究方向：深化植物修复机理,完善植物修复模型。加强植物-微生物协同修复的机理研究和技术应用,利用表面活性剂提高植物修复效率,加强复合有机污染植物修复研究。     

Monthly variations of soluble P in a volcanic ash derived soil as affected by organic and mineral fertilizers

Summary The effect of organic amendments (cow manure and green manure) on monthly variations of soluble P in a volcanic-ash-derived soil was studied. Soluble P (Truog's method) showed minimums at the beginning of August and at the beginning of January. Cow manure produced a remarkable increase of soluble P and removed the January minimum. In soils treated with legume green manure, soluble SP markedly decreased during the first and second month. Data for organic P suggested that the summer decreases of soluble P were partly due to microbial immobilization. In soil treated with mineral fertilizers only, more than half of the P added as superphosphate was found as Al and Fe phosphate after one month. Organic amendments, especially cow manure, decreased the immobilization of superphosphate P.     

Investigation of luminescent banding in solid coral: the contribution of phosphorescence

This study investigates the nature and components of annual luminescent banding in massive Porites coral skeletons, with a view to refining the technique for using this banding to reconstruct past environmental conditions. Three-dimensional excitation-emission-matrix spectroscopy and optical fibre beam delivery have been used to investigate the luminescence properties of the bright and dull bands of solid coral. Six characteristic excitation/emission peaks have been identified: 280/450–600, 340/450, 370/470, 390/485, 420/505 and 450/530 nm. The first peak corresponds to protein-type fluorescence. The others are characteristic of humic acid luminescence. The difference in luminescence intensity between bright and dull bands has been quantified and characterised spectroscopically. The luminescence of the bright bands is up to 25% more intense than their neighbouring dull bands with the greatest increase in relative intensity in the long wavelength emission region, between 500 and 600 nm. The contribution of long-lived phosphorescence to the total luminescence intensity has been determined by time-resolved measurements on the 100 ms timescale. Both bright and dull bands show long-lived phosphorescence with decay times up to 1.5 s. This phosphorescence accounts for about 10% of the total luminescence intensity of bright bands. The difference in phosphorescence intensity between bright and dull bands is substantially greater than the difference in total luminescence intensity: the phosphorescence of bright bands is up to twice as intense as that of dull bands. This suggests that phosphorescence plays an important role in defining luminescent banding in coral. Furthermore, the large observable difference in phosphorescence between bright and dull bands indicates that measurement of phosphorescence profiles across growth bands in corals may prove to be a more sensitive indicator of past environmental conditions than measurements of total luminescence. Received: 18 March 1999 / Accepted: 20 December 1999     

Short-term dynamics of culturable bacteria in a soil amended with biotransformed dry olive residue

Dry olive residue (DOR) transformation by wood decomposing basidiomycetes (e.g. Coriolopsis floccosa) is a possible strategy for eliminating the liabilities related to the use of olive oil industry waste as an organic soil amendment. The effects of organic fertilization with DOR on the culturable soil microbiota are largely unknown. Therefore, the objectives of this study were to measure the short-term effects of DOR and C. floccosa-transformed DOR on the culturable bacterial soil community, while at the same time documenting the bacterial diversity of an agronomic soil in the southeastern Iberian Peninsula. The control soil was compared with the same soil treated with DOR and with C. floccosa-transformed DOR for 0, 30 and 60 days. Impact was measured from total viable cells and CFU counts, as well as the isolation and characterization of 900 strains by fatty acid methyl ester profiles and 16S rRNA partial sequencing. The bacterial diversity was distributed between Actinobacteria, Alphaproteobacteria, Gammaproteobacteria, Betaproteobacteria, Bacilli, Sphingobacteria and Cytophagia. Analysis of the treatments and controls demonstrated that soil amendment with untransformed DOR produced important changes in bacterial density and diversity. However, when C. floccosa-transformed DOR was applied, bacterial proliferation was observed but bacterial diversity was less affected, and the distribution of microorganisms was more similar to the unamended soil.     

Chemical characterization of two extracts used in the determination of available soil nitrogen

Summary Two soil extracts used for chemical indexes for N availability, 0.01M NaHCO₃ and boiling 0.01M CaCl₂, were analyzed in effort to learn more about the nature of the extracted organic matter (O.M.). The two extracts appeared to remove different fractions of the soil O.M. A study of five soils showed that the C/N value of the NaHCO₃ extract (following decarbonation) was significantly higher than that of the total soil O.M.; while the C/N value in the boiling CaCl₂ extract was not significantly different from that in the soil O.M. There was also significant variation in C/N values among soils for the boiling CaCl₂ extract. The extracts of three soils were analyzed for apparent molecular weight distribution using gel filtration and the results compared to those for base-extracted humic substances. Almost all the molecules in the extracts had apparent molecular weights less than 21,000 daltons while 21 to 47% of the humic substances from the same soils (extracted with 0.5M NaOH) had molecular weights greater than 21,000 daltons. In the boiling CaCl₂ extract, 78 to 87% of the humic substances had apparent molecular weights less than 1,000 daltons, whereas with the NaHCO₃ extract, 42 to 83% of the humic substances were in the 1,000 to 21,000 dalton range. Forty-three to 92% of the N extracted by the NaHCO₃ was in protein form, and 8 to 30% was ninhydrin-detectable. In the boiling CaCl₂ extract 25 to 30% of the extracted N was ninhydrin-detectable. For the same 10 soils, ninhydrin-detectable N values of the boiling CaCl₂ extract appeared closely related to greenhouse and field relative N uptake, while the ninhydrin-detectable N values of the NaHCO₃ extract appeared unrelated to both. The protein N and protein in plus ninhydrin-detectable N values of the NaHCO₃ extract were closely related to greenhouse relative N uptake only. The results of this study indicated that specific fractions of the soil O.M. were being extracted by the two solutions and that significant differences existed in the chemical nature of the two extracts. Paper No. 6175 of the J. Ser. of the Pennsylvania Agric. Exp. Stn. Authorized for publication Jan. 26, 1981.     

Minimizing phosphorus release from newly flooded organic soils amended with calcium silicate slag: a pilot study

A pilot study was conducted using commercially available forms of calcium silicate (CaSiO₃) slag as a soil amendment to reduce phosphorus (P) release from an organic soil after flooding. Broadcasting CaSiO₃ slag on top of the soil reduced the flux of soil P up to 84% compared to an unamended soil control. However, incorporation of CaSiO₃ slag into the soil was only minimally effective at reducing P release. These materials have a potential use in the construction of treatment wetlands in south Florida. Further work is needed to better define reaction mechanisms, investigate the long-term treatment efficacy of these materials and address other environmental questions concerning their use.     

集约高产农业生态系统有机物分解及土壤呼吸动态研究

以河北省吴桥县龙王河中心试区内的集约农业生态系统为例 ,借用生态学的方法 ,用网袋法测定了集约高产田 ( HYF)和中产田 ( MYF)小麦秸秆、小麦根、玉米秸秆和玉米根等 4种有机物的分解动态 ;用隔离罐 -碱液吸收法测定了土壤的呼吸动态 ;并以此推算了 2种农田土壤 C的矿化率和平衡系数 .结果表明 ,集约高产田的有机物分解与中产田没有明显区别 ,土壤呼吸量分别为 1 878.5和 1 72 5.7g CO2 ·m- 2 · a- 1.土壤 C的矿化率分别为 5.64%和 5.48% ,平衡系数分别为 1 .84和 1 .86,表明集约高产并没有降低土壤 C的正平衡     

施肥对雷竹林土壤活性有机碳的影响

采用重施肥料试验研究了不同重施肥习惯对雷竹林土壤碳库产生的影响,结果表明,各有机肥、化肥混合处理土壤总有机碳(TOC)、水溶性碳(WSOC)、微生物量碳(MBC)、矿化态碳(MC)及WSOC/TOC、MBC/TOC和MC/TOC均显著或极显著高于单施化肥各处理.3个有机肥、化肥混施处理中,随着有机肥用量减少,TOC、WSOC、MBC和MBC/TOC显著下降,有机肥用量减少一半,上述各类碳分别下降10.75%、12.02%、30.94%和22.61%.单施化肥处理中,氮素用量超过1009.5 kg·hm^-2·年^-1会使土壤WSOC、MBC、MBC/TOC明显降低.雷竹土壤TOC、WSOC、MBC和MC两两之间相关性均达显著或极显著水平,进一步通过6个处理变异系数分析发现,土壤MBC、MBC/TOC是衡量雷竹土壤碳库质量的最佳指标.     

有机胶结形成土壤团聚体的机理及理论模型

土壤团聚体是土壤结构的基本单位,其组成和稳定性直接影响土壤肥力和农作物的生长,对于有机质含量高的黑土,有机胶结物质是形成土壤团聚体的主要因素。在综合有机胶结剂和土壤团聚体的研究的基础上,阐述了有机胶结物质的特性,土壤生物和植物根系在土壤团聚体形成中的作用,土壤团聚体形成的机理及理论模型。