FIELD: plant growing and agricultural chemistry. SUBSTANCE: method involves treating plants with composition comprising base additives containing preparation produced by sequential extraction of Mortierella exigua micromycet biomass by non-polar extracting agent in above-critical state, water, alkali, water, acid, water alkali, and water, with following joining of first extract with solid residue; treating plants with composition used in an amount of 0.1-20 mg/hectare of plantation or 0.5- 10,000 mg/t of seeding material at the rate of total content of chitosan, arachidonic acid and eicosapentaenic acid. EFFECT: reduced accumulation of toxic substances in agricultural crops and in soil, inhibited migration of toxic substances, as well as stress effect of toxic substances upon agricultural crops. 3 cl, 3 tbl, 5 ex
