English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

PETRÁŠOVÁ, V., MARTINEC, J., POSPÍŠILOVÁ, Ľ.: Total carbon content and humic substances quality in selected subtypes of Cambisols. Acta univ. agric. et silvic. Mendel. Brun., 2009, LVII, No. 4, pp. 73–82 Cambisols cover an estimated 45% of agricultural soils in the Czech Republic. We aimed our work at stabile forms of organic carbon and humic substances quality in Cambisols under diff erent types of soil management (grassland and arable soil). Object of our study were the following subtypes of Cambisols: Eutric Cambisol (locality Vatín – arable soil), Eutric Cambisol (locality Vatín – grassland), Haplic Cambisol (locality Náměšť n/Oslavou – arable soil), Leptic Cambisol (locality Ocmanice – grassland), Haplic Cambisol (locality Nové Město na Moravě – arable soil), Haplic Cambisol (locality Přemyslov – Tři Kameny – grassland), Arenic Cambisol (locality Pocoucov – arable soil), Dystric Cambisol (locality Sněžné – arable soil), Dystric Cambisol (locality Velká Skrovnice – arable soil), Dystric Cambisol (locality Vojnův Městec – arable soil). Non-destructive spectroscopic methods such as UV-VIS spectroscopy, synchronous fl uorescence spectroscopy (SFS) and 13C NMR spectroscopy for humic substances (HS) quality assessment were used. Total organic carbon (TOC) content was determined by oxidimetric titration. Fractionation of HS was made by short fractionation method. Isolation of pure humic acids (HA) preparation was made according to the standard IHSS method. Results showed that TOC and humus content varied from 2.70 % (grassland) to 1.3 % (arable soil). Avera ge HS sum was 8.4 mg / kg in grassland and 6.4 mg / kg in arable soil. Average HA sum was 3.6 mg / kg in grassland and 3 mg / kg in arable soil. Fulvic acids (FA) content was 4.7 mg / kg in grassland and 3.7 mg / kg in arable soil. HS quality was low and very similar for all studied samples. HA/FA ratio low (< 1). HS absorbance in UV-VIS spectral range was low and similar in all studied samples. Higher absorption in this spectral range was closely connected with higher HS content. Also in 2D-synchronous fl uorescence scan spectra similar shape of spectral lines was detected. Relative fl uorescence intensity strongly depended on HA and FA content. Five main fl uorescence peaks for HA and FA presence at λex./ λem.: 468/488, 482/502, 450/470, 376/396, 340/360 at constant diff erence of Δλ=20 nm were measured. 13C NMR spectra of HA isolated from Eutric Cambisol showed low aromaticity degree and high content of aliphatic moieties. HA were young (= less aromatic compounds in HA molecule) and no diff erences in HA structure were detected to compare arable soil and grassland. humus fractionation, UV-VIS, SFS and 13CNMR spectroscopy, Cambisols Cambisols combine soils with at least an incipient subsurface soil formation. Transformation of pa rent material is evident from structure formation and mostly brownish discoloration, increasing clay percentage, and carbonate removal. Dynamic of soil carbon storage and release in this soil type is still poorly understood. Hayes et al. (1990) have summarized the role of organic matter in soils as follows: 1. formation and maintenance of a good structure; 2. improvement of water capacity; 3. retention in availa ble form of plant nutrients by cation-exchange processes; 4. slow release of nitrogen, sulphur, phosphorus and some trace elements; 5. transport of metals into plant roots; 6. stimulation of plant growth; 7. immobilization of some anthropogenic chemicals added to the soil; 8. soil buff ering capacity enhancement; 9. raising the soil temperature. The agronomic functions of the organic matter through its eff ect on 74 V. Petrášová, J. Martinec, Ľ. Pospíšilová the physical, chemical and biological properties of the soil directly involve environment itself. For these reasons it is important to be able to assess the presen ce and quality of soil organic matter (SOM) that reach soil. In general, soil organic carbon could be divided into two groups – stabile and labile organic carbon forms. Stabile forms of organic carbon are represented by total carbon content (TOC), humic substances (HS) sum, humic acids (HA) sum and fulvic acids (FA) sum. Labile forms are represented by dissolved organic carbon. The best analytical method for extraction, isolation and complete HS characterization is still being discussed. HS diff er in molecular weight, elemental composition, acidity and cation exchange ca paci ty. The humic acids fraction consist of hydroxyphenols, hydroxybenzoic acids, and others aromatic structures with linked peptides, amino compounds, and fatty acids. Fulvic acids are typically composed of a variety of phenolic and benzene carboxylic acids. Fulvic acid molecule held together by hydrogen bonds to form stable polymeric structures or by association with polysaccharides. The last also contain more oxygen, less carbon and more acidic functional groups, particularly – COOH to compare with HA. A diffi culty with HS chemical extraction is that they are tedious and labor intensive and not suitable for large numbers of samples. New approaches of spectrometry that include a wide varie ty of the spectroscopic techniques have been successfully applied (Peauvouri et al., 2002). Hayes (1985) and Stevenson (1982) showed that absorbance at wavelength 465 nm is equal to light absorption of components associated with the fi rst phases of humifi cation process (young humic substances). Light absorption at 665 nm is related to well humifi ed components. Low Q4/6 values (< 4) indicate high HS quality, which is known by Chernozems, usually. So that UV-VIS spectral lines and indexes (Q4/6) are frequently used for characterization HS quality, maturity and condensation degree. Synchronous fl uorescence spectra (SFS) performed the high resolution of spectral peaks. Miano and Senesi (1992) reported that the most effi cient fl uorophores are indicated to be variously substituted, condensed aromatic rings, and/or highly unsaturated aliphatic chains. Peuravuori et al. (2002) divided fl uorescence spectrum into several regions according to certain wavelengths and assumed that certain polycyclic contributors are responsible for humic fl uorescence properties. Humic substances fl uorescence spectroscopy is a sensitive method, with concentration interval in range from 1 to 100 mg / l at diff erent spectrofl uorimeters. Number of major fl uorescence peaks is equal to number of present fl uorophores in humic structure. Fluorescence spectroscopy can also diversify the presence of HA or FA, via SFS measurements. Short wavelengths of major fl uorescence peaks are typical for FA and long wavelengths for HA. Some of UV-VIS and SFS spectra of Czech soil humic acids samples were also considered by Pospíšilová et al. (2005, 2006, 2008). 13C – Nuclear Magnetic Resonance (NMR) is o en used for the elucidation of organic compounds and mixtures structure. We receive a specifi c piece of information on the chemical structures involving 13C atoms within a molecule. The carbon skeleton of HS is observed rather than the adjacent protons, allowing the functional groups to be detected. Carbon nuclei are spread over a wide range of chemical shi s that eff ectively separate signals even when carbons have only small diff erences in diverse structural environments (Simpson, 2002). Carbon structures are determined in relative terms from the chemical shi s that occur when energy is absorbed by a molecular spinning in a magnetic fi eld. Individual carbon types in molecule indicate structure, sorption capacity, binding properties and solution interactions of HS (Wilson, 1987 and Simpson, 2002). However, NMR analysis is not always accessible because it is very complex and expensive technique. We focused our work on stabile carbon forms in the soil. HS were isolated from selected subtypes of Cambisols and their quality was studied using nondestructive spectroscopic techniques including UVVIS, SFS and 13C NMR spectroscopy. MATERIAL AND METHODS Soil samples were collected from the top soil and following subtypes of Cambisols were studied: Eutric Cambisol (locality Vatín – arable soil), Eutric Cambisol (locality Vatín – grassland), Haplic Cambisol (locality Náměšť n/Oslavou – arable soil), Leptic Cambisol (locality Ocmanice – grassland), Haplic Cambisol (locality Nové Město na Moravě – arable soil), Haplic Cambisol (locality Přemyslov – Tři Kameny – grassland), Arenic Cambisol (locality Pocoucov – arable soil), Dystric Cambisol (locality Sněžné – arable soil), Dystric Cambisol (locality Velká Skrovnice – arable soil), Dystric Cambisol (locality Vojnův Městec – arable soil). Basic characteristics of studied subtypes are listed in Tab. I. Soil reaction was determined by potentiometric method. Texture was determined by pipette method. We analysed TOC content by oxidimetric method according to Nelson and Sommers (1982). Fractional composition of HS was determined as follows: 5g of air_dried soil sample sieved at mesh size of 1mm and extracted by a mixture (1:1, 0.1M NaOH + 0.1M Na4P2O7) for 24h. The sediment was separated by centrifugation at 2800g for 10min, washed with mixture and centrifuge again. Two individual washings were unifi ed with original supernatant, acidifi ed with concentrated H2SO4 to pH 1.5. We allowed to precipitate HA overnight. TOC content was estimated by titrimetric method in aliquot volumes (Podlešáková et al., 1992). Isolation of soil HA was made according to the standard international IHSS method (Hayes, 1985). 100g of air-dried soil sample, sieved at mesh size of 1mm, washed by 10 % HCl and stirred for 1–2 Total carbon content and humic substances quality in selected subtypes of Cambisols 75 hours (decalcination process). A er negative reaction for CO2, (detected by seeing no CO2), the soil rest was washed by 0.05 M HCl. A er negative reaction for Ca2+ (detected by ammonium oxalate), the soil rest was washed by distilled water. A er negative rea c tion for Cl ̄ (det