Effects of Pig Manure and Its Organic Fertilizer Application on Archaea and Methane Emission in Paddy Fields

Paddy fields account for 10% of global CH4 emissions, and the application of manure may increase CH4 emissions. In this study, high-throughput sequencing technology was used to investigate the effects of manure application on CH4 emissions and methanogens in paddy soil. Three treatments were studied: a controlled treatment (CK), pig manure (PM), and organic fertilizer (OF). The results showed that the contents of Zn, Cr and Ni in paddy soil increased with the application of manure, but the contents of heavy metals gradually decreased with the growth of rice. The Shannon index and Ace index showed that the application of pig manure and organic fertilizer less affected the diversity and richness of soil Archaea. The results of community composition analysis showed that Methanobacterium, Methanobrevibacter, Methanosphaera, Methanosarcina and Rice_Cluster_I were the main methanogens in paddy soil after manure and organic fertilizer application. Soil environmental factors were changed after applied manure, among which total potassium (TK) and total nitrogen (TN) were the main environmental factors affecting methanogens in paddy soil. The changes of soil environmental factors affected the community composition of methanogens, and the increase of the relative abundance of methanogens maybe the main reason for the increase of CH4 emission flux. The relative abundance of methanogens and CH4 emission flux in paddy soil were increased by both pig manure and organic fertilizer application, and pig manure had a bigger impact than organic manure.