Influence of increasing doses of stillage on the content of heavy metals in soil and plant products
The effects of increasing doses of distillery stillage on the yield of spring wheat and oats, the content of heavy metals in grain and light-gray forest light loamy soil was studied in greenhouse experiments, repeated in the time during 3 years. The features of stillage are the next: dry matter is 3.7 %; acidity pH is 4.3; the mass fraction of lead (calculated on dry substance) is 35 mg/kg, of cadmium is 8, of zinc is 36, of copper is 8, of chromium is 10, of nickel is 13, of manganese is 16, and of cobalt is 10 mg/kg. The application of stillage contributed to the increase in above-ground biomass and weight of grain of oats, with respect to the control variant, on 45.159 and 61.231 %, correspondingly, of spring wheat - on 38.53 and 49.73 %. A single application of a high dose of stillage had no impact on the total contents of metals in the soil. It was below the APC in all cases and below the background specified for soils of Nizhny Novgorod region in the majority of cases. The concentration of mobile forms of metals determined in acetate-ammonium buffer was also below the MAC. Application of stillage influenced the physicochemical properties of soil (рНКСІ decreased compared to the control by 0.5 units, hydrolytic acidity increased by 0.3 meq/100 g of soil, the degree of saturation by bases decreased by almost 4 %), which led to an increase in the degree of mobility (percentage of mobile forms of the total content) of cadmium and copper. With application of waste matter in a dose of 400 ml/pot the degree of copper mobility was 1.3 times higher than in the control. The degree of mobility of lead, zinc and nickel did not practically depend on stillage application. Despite the tendency of some increase in the level of accumulation of metals in grains under the action of stillage, their content in all cases was within the standard value and was weakly depended on the dose of stillage. The use of high doses of distillery stillage did not almost effect on sanitary and hygienic characteristics of the soil, and obtained crop production satisfied the safety criteria on the content of heavy metals.