Agroecological features of mercury and arsenic behavior in the soil – plant system as a result of the use of organic fertilizers

The improper use of liquid livestock waste as fertilizers can lead to an increase in the content of mobile forms of heavy metals and metalloids in the soil. The purpose of the study is to examine the features of the behavior of Hg and As in the "soil – plant" system and an ecological and agrochemical assessment of the use of a liquid fraction of pig manure as an organic fertilizer. We carried out a field experiment in the subzone of the southern forest-steppe of the Omsk region on meadow-chernozem soil. We studied the effect and two years of aftereffect of organic fertilizer on the yield of a variety of spring soft wheat “In memory of Aziev”, as well as the behavior of mercury and arsenic in the soil-plant system. The predecessor of spring wheat was peas. It was established that the optimal dose of the liquid fraction of pig manure in meadow-chernozem soil for spring wheat was 200 t/ha. Both the action and the aftereffect in this variant resulted in the highest yield increase. However, the introduction of pig manure leads to an increase in the content of Hg and As in the soil both in the year of action and in the coming years of aftereffect. The application of fertilizers at a dose of 300 t/ha per year leads to an increase in the gross mercury content by 1.36 times, and arsenic by 1.1 times. This is accompanied by an increase in the content of these elements in all organs of wheat (root, straw, grain) during the growing season and harvest. The distribution of elements by wheat organs both in the control and in the soil using fertilizer is as follows: roots > straw > grain. The roots are a protective barrier that prevents the entry and accumulation of metals in the generative organs. The removal of elements with grain in the year of action and the next two years of aftereffect does not exceed 0.01 % of their gross content in the soil and 15 % of the amount received with organic fertilizer. It is proposed to calculate the accumulation coefficient of Hg and As, taking into account the entire group of mobile forms of compounds of these elements in the soil.