Conclusions
Studies have shown a positive and strong arnica's reaction to humic acids application in the formof leonardite contained in PowhumusWSG 85 preparation on sandy soil.
A significant increment of flowering stems’number and inflorescences per plant along with increased leonardite doses (from 2 to 6 kg∙ha−1) was observed.
As a consequence raw material yield's increment was obtained.
Regardless of dose, leonardite application positively influenced enzymes’ activity catalyzing the transformation of the most important soil organic matter processes.
In response to higher leonardite application doses (4 and 6 kg∙ha−1) dehydrogenase's activity was approximately 2-fold greater, acid phosphatase, urease and protease approximately 1.5-fold greater than in soil without fertilization, which was related to both the amount of carbon
substrates available for microorganisms, enzymes, and favorable changes in soil pH.
Especially wide range of dehydrogenases’ enzyme activity indicates the usefulness of this group of enzymes to assess soil environment changes under the influence of tillage system.