IMPACT OF FERTILIZERS FROM SEWAGE SLUDGE ON AGROECOLOGICAL SOIL INDICATORS

Abstract

Purpose: to assess the effect of fertilizers from sewage sludge (SWS) of the Kadamovskie sewage treatment plants (STP) on agroecological soil indicators. Materials and methods. In a field experiment on a site located in Rostov region, the soil characteristics after growing winter wheat against the background of fertilizers based on SWS were studied. Soil fertility was assessed in the basis of crop yield, humus content, nutrients, salts and exchangeable bases. The content of acid-soluble and mobile forms of heavy metals was monitored as environmental indicators, the mobility coefficient of metals and the coefficient of soil protective properties were determined. Results. An increase in solid residue was noted in the variants with the SWS application in quantities of 30 t/ha by 5–10 %, which is estimated as insignificant, and in the variant with the sludge application at a maximum dose of 98 t/ha – by more than 30 %, which may indicate an excessive intake of salts with fertilizer. An increase in the phosphorus content in the arable soil layer was observed in all variants of applying litter chicken manure. The best response of winter wheat was obtained with a fertilization mixture of OSW with litter chicken manure. When OSW was applied in the amount of 98 t/ha, an increase in potassium, nitrogen, humus and solid sediment in the soil was noted. The latter indicates an increase in the salt content. An increase in mobile forms of nickel and cadmium was observed, especially in variants with the application of a mixture of OSW with granulated poultry manure. In all variants, the content of heavy metals of both forms did not exceed the sanitary and hygienic standards for soils. Conclusions. The best indicators of the agroecological soil state were observed when applying fertilizers from a mixture of wastewater sludge and litter chicken manure (2:1), which contributed to obtaining one of the best average yields of winter wheat over three years – 74.74 c/ha, which is 19.4 % higher than the control.