One way of recycling agricultural organic waste is the biotechnology of worms’ cultivation. Сulturing of worms (growing hybrid California red worms) provides worms biomass – a valuable supplement to the diets of farm animals, and organic fertilizer – biohumus. In addition it resolves biotechnology environmental issues in agricultural ecosystems.

As a result of recycling organic waste into biomass worms collect macro- and micronutrients as feed additive. With the increase of mineral elements in the substrate increases their content in biomass wormculture.

The issue on correction of substrate mineral composition remains unexplored and the indicators for wormculture biomass growth under different iron concentrations for the worms nutrient medium were not determined.

So, given the above, the study of the effect of different iron concentrations in the substrate on the growth and development of Californian worms is important and promising area of research.

The number of heavy metals in the substrate depends on wormculture development and accumulation of biomass and the goal of research was to establish the effect of different concentrations of iron in the composition of the substrate to increase wormculture biomass.

Experiments were conducted in the vivarium conditions of Bila Tserkva national agrarian university on hybrid California red worms. Iron sulfate was added into the culture medium for wormculture (fermented cattle manure and straw cereals) for all experimental group-beds.

In  the І experimental bed the iron sulphate metal content was reduced to concentration of 10917,4 mg/kg. The substrate of the ІІ and the ІІІ experimental beds contained iron, respectively 14077,3 and 17024,1 mg/kg. With the introduction of metal salt to the fourth experimental bed the substrate contained iron at 20742,1 mg/kg.

The iron salt was not used in the control variant. The background concentration of metal was at 7723,4 mg/kg substrate. The iron content in the substrate for worms was determined by atomic absorption spectrophotometry on the instrument AAS-30.

It was found that 90 days growing of hybrid California red worms on the substrate with different iron concentrations the quantity and weight of wormculture was built up differently. The background concentration of iron (test bed) the number of gender-age worms in the sample was 40,0 units. A slight iron increase in the І and the II experimental beds had positive impact on the number of mature individuals in the sample but the difference was not significant.

Increasing the concentration of iron in the composition of the substrate by 2,2 and 2,6 times (III and IV experimental beds) accompanied by a tendency to reduce the number of mature individuals. The index was lower, respectively by 5,0 % and
10,0 % as compared with the control.

It was established that higher iron doses in the substrate negatively influenced on the mass of mature worms. In the IV experimental bed the adult worms weight was lower than in the control by 11,8 % (p≤0,05).

Adding iron sulfate affected the worms breeding. During 90 days study of the explored factor in the І bed it showed a stimulating effect on the formation of cocoons and forming worms. Number of individuals who have not reached puberty was higher than in the control by 4,3 % (p≤0,05).

The increasing iron content in the substrate has reduced the number of young individuals. We discovered possible worms number decline in the IV experimental bed. The difference from the control was 5,6 %.

High doses of iron, in addition to reducing the number of young worms, caused a reduction in their weight. Thus, the wormculture weight of III and IV experimental beds was smaller, respectively by 13,8 % (p≤0,05) and 23,3 % (p≤0,01) as compared to control ones.

Thus, different iron concentrations in the substrate exhibits its properties as metal-biotics and as metal-toxicant in relation to wormculture. High iron doses in the form of sulfate negatively affect the quantity and mass growth of California red worms. The explanation for this may be the fact that iron in form of sulfate is easily transformed from substrate into the worms body, accumulates and shows toxicity.

Key words: wormculture, California hybrid red worms, substrate, ferrum, iron sulfate, feed additive.