Straw and pig manure composting
The harvested rice straw was chopped into pieces approximately 2-6 cm in length. A leak-proof film was placed at the bottom of a foam box, followed by a -20 cm thick layer of chopped straw, loosely packed. Urea was used to adjust the C/N ratio by dissolving it in water and evenly sprinkling it over the surface of the material. Additional layers of rice straw and dry pig manure were added and treated in the same manner. The materials were layered until the pile formed a rectangular block measuring 72 cm in length, 52.8 cm in width, and 44 cm in height (approximately 11 kg). The moisture content was adjusted so that a small amount of water seeped from the bottom upon completion of the pile, indicating a moisture content of approximately 60%. The composting process was carried out under natural thermophilic conditions.Two experimental groups were established: one group (HDS group) was treated with 0.25 g of HDS dissolved in 500 mL of ultrapure water and evenly applied to the compost materials; the other group (CK group) received no HDS addition. Each group included three replicates. Composting was conducted in foam boxes over a period of 40 days. Manual turning was performed on days 1, 3, 5, 8, 12, 20, 30, and 40 to ensure adequate oxygen supply.The purpose is to reduce antibiotic resistance genes during the composting process