Response of microbial community diversity and subsoil properties to cow manure amendment in mollisols

Subsoil fertilization can help agricultural sustainability, but this is not a widely adopted practice. Here, we conducted a pot experiment to study the response of microbial community diversity and topsoil/subsoil properties to cow manure amendment. Our results show that amending subsoil with cow manure (SM) increased available phosphorus (AP) and humic acid (HA) content and the ratio of humic acid to fulvic acid (HA/FA) by 22.2%, 17.7%, and 49.3%, respectively, relative to manure-amended topsoil (TM) (p < 0.05). SM was also more favorable for organic matter degradation and had 61.9%, 21.7%, and 85.3% higher relative abundances of the bacterial phyla Bacteroidetes and Actinobacteria and the order Cytophagales, respectively, relative to the TM treatment (p < 0.05). Compared with that of unamended subsoil (S), the Chao1 index, operational taxonomic units, and Shannon index of fungi were increased but bacterial diversity was decreased by SM treatment (p < 0.05). The only significant difference of the TM-treated soil with the unamended topsoil (T) was a lower bacterial Shannon index (p < 0.05). In conclusion, soil physicochemical properties and subsoil microbial communities were sensitive to cow manure amendment, which has the potential to improve the productivity of subsoils.