Responses of soil carbon, nitrogen, microbial activity, bacterial community composition and grain yield to farmyard manure amendments in a rainfed agriculture (Paddy) system of Himalaya

The impact of farmyard manure (FYM) amendment (15, 30 and 60 Mg ha−1) on the changes of carbon content, nitrogen content, microbial activity, bacterial community composition and grain yield were investigated in a traditional rainfed agriculture (Oryza sativa L.) system of the Himalaya. Our results showed that carbon (5 to 16%) and nitrogen (37 to 55%) contents were reduced significantly at the end of the paddy cropping season; while the C:N values (46 to 90%) and microbial activity (66 to 122%) were increased significantly at the end of the paddy cropping season as compared to sowing season in the soil amended with FYM. The grain yield of paddy increases significantly with increasing rates of FYM. We found the highest abundance of copiotrophs (Proteobacteria and Firmicutes) in the soil amended with different rates FYM at the end of the paddy cropping season. Differences in soil bacterial communities are associated with different amendment rates of FYM, suggesting that higher FYM amendment rates could change the bacterial community compositions which have an adverse impact on soil carbon and nitrogen contents at the end of the paddy cropping season in the rainfed agriculture system of the Himalaya.