Sulphur status in agricultural soils determined using the Mehlich 3 method

Several sets of soil samples were chosen to demonstrate the applicability of the Mehlich 3 extractant for the determination of sulphur (S) in soils. Archived samples from 139 basal soil monitoring plots (BSMS) sampled in 1995 and 2013, samples from eleven long-term field trials sampled in 1981 and 2017, 1167 soil samples from the areas vulnerable to S losses and 720 samples from the non-vulnerable areas sampled in 2010 were chosen for the experiments. Mehlich 3 clearly showed a statistically highly significant decrease in the soil S content caused by reduction of SO2 emissions in the long-term field experiments from 33 mg/kg in 1981 to 8 mg/kg in 2017 for the median of the untreated controls. Similar results were obtained for BSMS samples, where an average decrease from 26 mg/kg in 1995 to 17 mg/kg in 2013 was found. Mehlich 3 also showed that more than 52% of samples from the areas vulnerable to S losses were in a very low content category in contrast to only 3% of soils from the other areas. Mehlich 3 clearly proved the capacity to distinguish changes in the content of soil S in all studied cases.