Change in the chemical composition of the solid fraction of manure during composting

The aim of the study is to evaluate the transformation processes of the solid fraction of cattle manure during its accelerated composting. The studies were conducted in a laboratory experiment with the solid fraction of manure obtained using the ST-1200 screw press separator. Humus was added to the solid frac-tion of manure as an additional substrate. The experiment was carried out according to the following scheme: 1 – humus (H); 2 – solid fraction of manure (SFM); 3 – P + SFM (1 : 1); 4 – P + SFM (1 : 2); 5 – P + SFM (2 : 1). Composting was carried out for two months in a closed-type device with periodic me-chanical aeration of composts (once every 7 days). Addition of humus to the solid fraction of manure in different proportions reliably decreased the temperature of the substrates by an average of 1 °C and signi-ficantly reduced the humidity of the composted mass to 69–77%. The reaction of the medium of the solid fraction of manure after separation was estimated at 7.7 pH units. As the compost matured, it increased to 8.0 pH units in all experimental variants. In all variants of the experiment, a decrease in organic carbon by 17–23 was noted. When composting the solid fraction of cattle manure, an increase in the content of total nitrogen by 50 % and total phosphorus by 124 % was found on the 61st day. When adding humus to the solid fraction of manure in a ratio of 1 : 2 and 2 : 1, the maximum increase in Ntotal was noted, amounting to 89–100 % of the initial level. The provision of substrates with mobile phosphorus and potassium after composting increased by 2–3 times.