Objective This study aimed to explore the response of soil microbial communities in purple soil paddy fields to long-term phosphorus (P) fertilizer omission, to provide a scientific basis for the rational application of P fertilizer.

Method Based on the long-term located experiment of purple soil, two main treatment groups (lack of P fertilizer and application of P fertilizer) were selected in this study. The main treatment group of lack of P fertilizer included three sub-treatments: single application of chemical nitrogen fertilizer (N), application of chemical nitrogen and potassium fertilizer (NK) and rice straw returning (MS). The main treatment group of applying P fertilizer included three sub-treatments: NPK balanced fertilization (NPK), NPK balanced fertilization + straw returning (NPK + MS), high NPK balanced fertilization (1.5 times balanced fertilization) + straw returning (1.5NPK + MS). The effects of P fertilizer deficiency on soil microbial community structure characteristics were clarified by analyzing soil physical and chemical properties and richness, diversity and community composition of bacteria, archaea and fungi in purple paddy soil of Southwest China.

Result Different fertilization treatments had no significant effect on soil pH, total potassium and available nitrogen content, but the content of total P and available P in the soil treated with P fertilizer was 0.6 ~ 2 times and 5.2 ~ 196 times that of the treatment without P fertilizer, respectively. The relative abundance and diversity indices of soil bacteria and archaea increased significantly by 2.2% - 11.3% under the treatment of P fertilizer deficiency, while there was no significant difference in the relative abundance and diversity index of fungi between the two treatments of P fertilizer deficiency and P fertilizer application. Redundancy analysis showed that the absence of P fertilizer significantly reduced soil available P and increased soil C/P ratio, resulting in significant changes in soil fungal community structure. For example, the relative abundance of Basidiomycota, Glomeromycota and Methanocellales increased by 184.6%, 274.6% and 100.0%, respectively, and the relative abundance of Ascomycota decreased by 20.3%.

Conclusion Long-term P fertilizer deficiency in purple soil leads to P deficiency, which increases the richness and diversity of bacteria and archaea in soil and changes the structure of fungal community.