Objectives We studied the dynamics of soil fertility and fungal community structure in yellow-brown paddy soil under long-term different fertilization measures, to scientifically clarify a pathway towards sustainable rice production.
Methods The long-term experiment of yellow-brown paddy soil, located in Wuhan, Hubei Province was established in 2005. There were five treatments: no fertilizer control (CK), N fertilizer (N), NPK fertilizers (NPK), organic manure (OM), NPK and organic manure (OMNPK). In 2020, soil samples at 0−20 cm depth were collected from the treatment plots to determine the nutrient contents and enzyme activities using standard procedures, and the fungal community structure using the Illumina MiSeq high-throughput sequencing, the FUNGuild and ecological network methods.
Results 1) N treatment reduced, NPK treatment maintained, while OM and OMNPK treatments significantly increased soil available nutrients compared with CK. OMNPK treatment significantly decreased the α-glucosidase and sulfatase activity, but increased β-cellobiase activity; OM and OMNPK increased leucine aminopeptidase activity but decreased glucosamine activity; whereas N and NPK treatments elicited opposite trends on these two enzymes. 2) N treatment significantly reduced, while NPK, and OM treatments increased fungal diversity. The LEfSe analysis showed that the differential species were Entrophospora genus and Sympoventuriaceae family in N treatment, were Microascales order and Microascaceae family in OMNPK treatment, and were Sphaeria, Pyronemataceae and Pseudaleuria genus in OM treatment. The redundancy analysis revealed that β-glucosidase, β-xylosidase, phosphatase, L-leucine aminopeptidase, N-acetyl-glucosaminidase, sulfase, and pH were important factors affecting soil fungal community structure. 3) Fertilization increased the relative abundance of pathotroph fungi and reduced that of saprotroph fungi. Compared with CK, the treatment N, NPK, OM and OMNPK increased the relative abundance of pathotroph fungi by 190.5%, 141.4%, 71.5% and 250.2%, decreased those of saprotroph fungi by 30.6%, 33.3%, 19.4% and 49.5%, increased those of symbiotroph fungi by 310.8%, 956.8%, 424.3%, and 435.1%. The abundance of animal pathogen was dominant in the pathotroph fungi, OMNPK, N, NPK, and OM treatments increased the animal pathotrogh abundance by 322%, 184%, 105% and 85%, compared to CK. N and NPK treatments also led to higher plant pathotrogh fungi than CK, while OMNPK and OM treatments did not. The OM and MNPK treatments increased the edge number, positive correlation number, average weight, graph density, network diameter, and connection components of the fungal network, and enhanced the complexity of the network.
Conclusions Long-term sole organic fertilizer application improved soil fertility, increased the diversity of fungal community and the complexity of species interaction, and reduced the abundance of pathological fungi. The combination of organic and inorganic fertilizers resulted in markedly higher effect, but also increased the potential risk of animal pathogen disease.
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