Potential of Mehlich 3 method for extracting plant available sulfur in the Czech agricultural soils

Abstract

Mehlich 3 is an extractant used worldwide for extracting bioavailable nutrients in soils; however, its extraction abilities for sulfur (S) are still not well described. The aim of this preliminary study was to compare the results of Mehlich 3 determined soil S fraction (S_M3) with the results of sulfur fractionation, mainly focusing on bioavailable S (S_av – sum of water-extractable (S_w) and adsorbed (S_ads) sulfur). Air dried soil samples from commonly used agricultural soils were chosen for the analyses. The following S fractions were determined: (i) S_w; (ii) S_ads; (iii) S_av; (iv) 1 mol/L HCl extractable (S_HCl); (v) estersulfate (S_es); (vi) organic (S_org) and (vii) total (S_tot). The median value of S_M3 (18.3 mg/kg) was similar to S_av (17.9 mg/kg). From the correlation and regression analysis it is clear that S_M3 results are in close relationship with S_av form. On the other hand, the relationships between S_M3 and organic S (including S_HCl) were very weak. Based on the obtained results it can be concluded that Mehlich 3 method has a good potential to determine bioavailable sulfur in commonly used agricultural soils. However, especially the plant response should be further studied to confirm this theory.