ON ISSUE OF CLARIFYING THE METHOD FOR DETERMINING THE ECOLOGICALLY PERMISSIBLE APPLICATION RATE OF ORGANIC FERTILIZER

Purpose: to clarify the method for determining the ecologically permissible application rate of sewage sludge (hereinafter referred to as SWS) or fertilizers made from them using mathematical tools. Materials and methods. The data obtained from studying the effects of SWS application from municipal treatment facilities in representative cities of Rostov Region, both in different doses and mixtures, are used. The research method involves analyzing the accepted method for determining the application rates of SWS and fertilizers based on them according to GOST R 17.4.3.07-2001, data from field studies by the authors and other Russian scientists. Results. The specific application rates according to the formulas recommended by GOST R 17.4.3.07-2001 for SWS from sewage treatment facilities in town Novocherkassk amounted to 613.61 t/ha, and in town Novoshakhtinsk – 277.47 t/ha. It is clear that the specific application rate of several hundred tons per hectare is exaggerated, as evidenced by field studies conducted both by the authors themselves and by other scientists. To increase the accuracy of determining a single dose of sludge application, the mobile forms of heavy metals and adjustment of the total dose based on the environmental indicators of WWS are proposed to be taken into account. The calculation of sludge application rates from sludge maps of representative cities, which made it possible to justify the feasibility of the proposed clarifications, are presented. According to the proposed methodology, the specific application rates for WWS in towns Novocherkassk and Novoshakhtinsk were obtained at 66.38 and 52.32 t/ha, respectively. Conclusions. The proposed clarifications make it possible to obtain the most probable value when determining the application rate of sewage sludge, which will ensure the environmental safety of the fertilizers in question for the greatest number of environmentally significant indicators, including mobile forms of heavy metals.