Phosphorus is a major plant nutrient constraint. However, most mineral P in soils is not available for the plant root despite the high content of total P. Mineralization of organic P by phosphatases via hydrolyze ester-phosphate bonds in phosphoester can compensate P limitation in soil.

However, phoD as the key gene encoding alkaline phosphomonoesterase, its role in the regulation of soil P turnover remains poorly understood.

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences (CAS) and their collaborators from Germany and Italy collected P-poor paddy soil. Half of the soil was fertilized by KH₂PO₄ (120 kg ha^-1) (P80) and the other half was used as control (P0). 500 g P0 or P80 soil was evenly packed in the nylon bag placed in the center of a pot and was taken as rhizosphere soil. The space between the pot and nylon bag was filled with another 500 same soil to obtain non-rhizosphere bulk soil. 

Then, 22-day-old rice seedlings were planted in the center of 24 pots (12 for each P80 and P0 respectively). Half of them were subject to continuous flooding, while the other half to drying-rewetting cycles.

The researchers found significantly phoD abundance higher in P0 treatments than in P80 treatments, which was negatively correlated with soil P availability during the 42 days of rice growth.

Compared with P80, network revealed stronger competition among phoD-harboring microorganisms in non-fertilized soil.

They found the high abundance of phoD gene found in P0 treatment to the growth of rare operational taxonomic units (OTUs) affiliated to Actinobacteria and Cyanobacteria. Beside on the relationship between phoD abundance of individual OTUs and soil P fractions, they suggested that organic P was mineralized by phoD-harboring microorganisms under P-poor condition and immobilized in biomass under p-enrich condition.

The study, published in Soil Biology and Biochemistry, was supported by the National Natural Science Foundation of China and the Youth Innovation Team Project of ISA, CAS.

Contact: GE Tida 

E-mail: gtd@isa.ac.cn 

Institute of Subtropical Agriculture, Chinese Academy of Sciences