Metagenomic insights into the effects of organic and inorganic agricultural managements on soil phosphorus cycling

Microbes play important roles in regulating soil phosphorus (P) cycling in agroecosystems. However, little is known about how P-cycling microbes respond to organic and inorganic agricultural managements in terms of their functional and phylogenetic traits. Here, metagenomics was used to determine effects of P-cycling functional genes and taxa on soil P availability in a forage (Broussonetia papyrifera) monoculture ecosystem under organic (inoculating arbuscular mycohrrizal fungi (AMF) and intercropping legume (Medicago sativa)) and inorganic (adding chemical nitrogen (N) and P fertilizers) managements. The results showed that soil available P (AP) in plots with both legume and AMF addition was increased by 54.3 % compared with the control and was1.6–2.4 times higher than in plots with N or P fertilization. The abundance of ppa involved in inorganic-P solubilization was significantly increased after adding both legume and AMF compared with P-addition treatment. Soil alkaline phosphatase activity increased with P fertilizer addition and was positively correlated with soil AP. The abundances of phoA and phnI involved in organic-P mineralization were significantly higher under P fertilization treatment than under N fertilization treatment. Soil total N and AP were the key drivers on interactions among P-transportation genes, organic-P mineralization genes and taxa related to P-transportation. Overall, organic agricultural management increases soil P availability by increasing the potential of inorganic-P solubilization, while inorganic agricultural management regulates P availability via altering the potential of organic-P mineralization. These findings could provide a better understanding of the mechanisms that drive soil P availability under organic and inorganic agricultural managements.