Dataset - Potential of Mehlich 3 method for estimating plant available sulfur
The aim of this research is to compare the results of M3 estimated sulfur with the different sulfur fractions in the set of soil samples taken up from the sites with wide range of pH values as well as the sulfur contents. Due to the using of correlation analysis will be possible to estimate the sulfur form, which is in the closest relation to M3 method. Based on the results will be possible to predict potentioal of M3 to estimate plant available S. The study of the set of 98 samples from different commonly used agricultural soils showed that S content estimated with M3 method closely corresponds with the amounts of bioavailable S fractions. That was confirmed with both, correlation and regression analyses as well as the fact that relations between SM3 and organic S fractions were very weak. M3 can be also evaluated as a suitable extractant for bioavailable sulfur for the commonly used arable soils. To confirm this preliminary study, further research of SM3 and S content and uptake by different plant species is needed.
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Different soil sulfur forms were estimated as following: for the contents of Sw, Sads and SHCl - fractionation after Morche (2008) was used. For the SHI, the method after Shan and Chen (1995 modified by Morche, 2008) Stot content was determined in the digests obtained by the following decomposition procedure: Aliquots (0.5 g) of soil samples were decomposed with a mixture of 8 ml concentrated nitric acid, 5 ml of hydrochloric acid, and 2 ml of concentrated hydrofluoric acid. The mixture was heated in an Ethos 1 (MLS GmbH, Germany) microwave assisted wet digestion system for 33 min at 210 °C. After cooling, the digest was quantitatively transferred in Teflon® vessel and evaporated to dryness at 160 °C. The digest was then dissolved in a 3 ml nitric and hydrochloric acid mixture (1:3), transferred into a glass tube, filled up by deionized water and measured. The certified reference material RM 7003 Loam was applied for the quality assurance of analytical data. For the comparison with other fractions, M3 extraction (Mehlich, 1984) was used to obtain SM3, The concentrations of S in soil digests and extracts were determined using optical emission spectroscopy with inductively coupled plasma (ICP-OES) with axial plasma configuration, Varian, VistaPro, equipped with autosampler SPS-5 (Australia). Operating measurement wavelength for ICP-OES was 180.7 nm for S. Measurement conditions were: power 1.2 kW, plasma flow 15.0 L min-1, auxiliary flow 0.75 L min-1, nebulizer flow 0.9 L min-1. The content of Sav was calculated as the sum of Sw and Sads, the content of Ses sulfur as Ses = SHI – Sav and the approximate content of Sorg as Sorg = Stot – (Sav + SHCl), respectively.