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 (SM3) with the results of sulfur fractionation, mainly focusing on bioavailable S (Sav - sum of water-extractable (Sw) and adsorbed (Sads) sulfur). Air dried soil samples from commonly used agricultural soils were chosen for the analyses. The following S fractions were determined: (i) Sw; (ii) Sads; (iii) Sav; (iv) 1 mol/L HCl extractable (SHCl); (v) estersulfate (Ses); (vi) organic (Sorg) and (vii) total (Stot). The median value of SM3 (18.3 mg/kg) was similar to Sav (17.9 mg/kg). From the correlation and regression analysis it is clear that SM3 results are in close relationship with Sav form. On the other hand, the relationships between SM3 and organic S (including SHCl) 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.

Keywords

• sulfur bioavailability
• macronutrient
• soil extractant
• soil testing
• soil tests comparison