Fractions of Ni, Pb, Cr, and Their Impact on Enzyme Activities of Arable Land Cultivated by the Simplified Method

Total metal content is not representing its availability and thus does not provide the details about potential environmental hazards, including the impact on soil enzyme activities. To understand metal availability, chemical fractions must be considered. The goal of this study was to evaluate the influence of Ni, Cr, and Pb fractions on the enzymatic activity of soils cultivated by the simplified method, which is rare not only in Poland. The percentage of studied metals in fractions was determined according to the Community Bureau of Reference (BCR) method. Four fractions were extracted: acid soluble and exchangeable (F1), reducible (F2), oxidizable (F3), and residual (F4). The highest Ni and Cr percentages were noted in fraction F4, and for Pb, they were noted in fraction F2. The smallest Ni and Pb percentages were observed in fraction F1 (most mobile) and for Cr, they were observed in fraction F2. In soil samples collected in spring, the significant relationship was stated between F1/Ni/dehydrogenase, F2/Pb/dehydrogenase, and F2/Pb/urease. Such dependence occurred between F1/Ni/phosphatase and F4/Ni/urease during summer as well as between F1/Ni/phosphatase and F4/Ni/dehydrogenase in autumn. F1/Pb caused a drop in phosphatase activity, whereas F4/Cr influenced its increase. The study results indicated that metal fractions influenced phosphatase activity the most, while protease activity in the soil was not affected.

Automated summary

The study aimed to evaluate the influence of Ni, Cr, and Pb fractions on soil enzymatic activity in soil samples cultivated using a simplified method. Chemical fractions were considered, with significant relationships found between specific metal fractions and enzyme activities, particularly phosphatase activity. The results suggest that metal fractions have a varying impact on soil enzyme activities, with phosphatase activity being the most influenced.