Pol. J. Environ. Stud. Vol. 31, No. 2 (2022), 1637-1644 Original Research Dynamic Changes of Humic Acids in Chicken Manure Composting Xing Han1#, Shichao Liu1,2#, Zhonglei Xie3, Xiulan Ma1, Yujun Wang1*, Chang Peng4** 1College of Resources and Environmental, Jilin Agricultural University, 130118 Changchun, China