Physico-chemical properties of hyperthermophilic composting from livestock manures and its effects on growth of Chinese cabbage

Abstract: In order to assess the feasibility of improving the composting efficiency of animal wastes by fast hyperthermophilic composting and to evaluate the effects of the hyperthermophilic compost application on crop growth, chicken manure (CM), pig manure (PM) and dairy manure (DM) mixed with rice husk were used as raw materials to study the physico-chemical properties of the feedstocks before and after the fast hyperthermophilic treatment (HPT) at 85 ℃ for 24 h. In addition, a pot experiment in greenhouse was carried out to study the effects of hyperthermophilic chicken manure compost application on the seed germination and growth of Chinese cabbage. The obtained results were listed as following. The population of fecal coliforms was significantly reduced by HPT and met the hygienic requirement for harmless disposal of animal manures. Dilution plate count showed that the numbers of the thermophilic microorganisms that could grow at 70 ℃ in the three kinds of animal manures were increased by two orders of magnitude using HPT. HPT significantly decreased the pH value of animal manure extracts. The contents of dissolved organic carbon (DOC) and total volatile fatty acids (TVFAs) were significantly increased after HPT. Compared with those in the raw materials, the contents of DOC in PM, DM and DM were increased by 46.5%, 22.9% and 42.6%, respectively, and contents of TVFAs were increased by 37.2%, 31.2% and 56.8%, respectively. The HPT had little effect on the total nitrogen, total phosphorus and total potassium contents in the three kinds of raw materials, but the contents of free amino acids were increased by 79.2%, 58.1% and 74.6%, and the humic substance contens were increased by 27.6%, 3.4%, 27.3% (P<0.001) in PM, DM and DM respectively. The contents of NH4 +-N were increased by 114.6% and 40.6% in CM and PM, so the seed germination index and emergence rate of Chinese cabbage treated by HPT products was reduced. Results from the pot experiment showed that the aboveground biomass of the Chinese cabbage treated by the hypothermophilic chicken manure were 20.4% and 51.9% higher than those treated by the pure inorganic fertilizers and those treated by the conventional organic fertilizer. In conclusion, it is feasible to improve the processing efficiency of animal manures by rapid thermophilic composting at 85 ℃ for 24 h. The obtained HPT product could be applied to the soil to reduce the use of inorganic N. However, the HTP products are not recommended to be used as nursery substrates, and a reasonable amount and the proper application method should be selected based on the soil and crop type.