Agro-Environmental Rationale of Sewage Sludge Processing and Application

Abstract

Conservation agriculture is becoming a priority for Ukraine as well as for many countries of the world. It is a known fact that high content of heavy metals in the soil impairs fertility and carries the risk of crops translocation. An agroecological effect of obtaining and applying organic-mineral fertilizers has been insufficiently studied so far. The purpose of the work is to determine possibilities to produce new organic-mineral fertilizers based on sewage sludge with enhanced adsorbing properties, to establish their agroecological efficiency. Methods. Field, laboratory-analytical, statistical-mathematical. Results. From the agroecological point of view, the production process of organic-mineral fertilizers based on the sewage sludge of Kharkiv is justified. It allows us to expand functional capabilities of reagents, enhancing adsorbing properties of heavy metals. It is proved the advantage of organic-mineral fertilizers over the traditional ones on chernozem typical. After fertilization, the content of total carbon in the soil increased, the content of humic acids increased by 1,5 – 2,8 times, fulvic acids – by 1,1 – 1,7 times, the total sum of humic substances – by 1,3 – 2,1 times compared with no fertilizer option. It is established that application of organic-mineral fertilizers promotes blocking of heavy metals in soil and prevents translocation to plant. Maximum yields of corn were obtained after the local application of granular organic-mineral fertilizers – the yield increase was 41% compared to the control, after introduction of bulk fertilizers – 32% compared to the control. Profit was $ 23 -36 per hectare. Conclusions. The process of organic-mineral fertilizers production on the basis of sewage sludge in Kharkiv is substantiated from the agro-ecological point of view. Agroecological and agrochemical efficacy of sewage sludge use as compared to organic and mineral fertilizers applied in equivalent doses separately was established on the typical heavy loam chernozem. After introduction of organic-mineral fertilizers based on sewage sludge a significant increase in the concentration of trace elements and heavy metals was found in the black soil but these indicators did not exceed the established maximum permissible concentrations. The implementation of the proposed technology will reduce bioavailability of heavy metals and their mobility in the soil which, in turn, impedes their accumulation in products. It is expected to increase soil fertility, crop yields and obtain environmentally friendly and safe products due to the stable composition of innovative fertilizers.