Nucleic acids are a major pool of hydrolyzable organic phosphorus in arable organic soils of Southern Ontario, Canada

Soil organic phosphorus (P-o) that is hydrolyzed by phosphatases into inorganic phosphate is a source of phosphorus (P) for agricultural crops. However, the hydrolysis of P-o compounds is contingent on their chemical form and stabilization in the soil matrix. We quantified three hydrolyzable P-o pools (simple phosphomonoesters, phospholipids, and nucleic acids) by adding substrate-specific phosphatases to Hedley sequentially fractionated extracts from three organic soils cultivated with carrots in Southern Ontario, Canada. We observed that most of the molybdate-unreactive P was hydrolyzable in the deionized water, 0.5 mol L-1 NaHCO3, and 0.1 mol L-1 NaOH P pools (67-92%) and accounted for 14-254 kg P ha(-1) in these arable organic soils. Nucleic acids represented 79% of the hydrolyzable P-o in these soils but were mostly found in the 0.1 mol L-1 NaOH P pool (89%), suggesting that this P-o form is bound to the soil matrix, probably to organic complexes based on the strong association between nucleic acids and total organic C (rho = 0.805). Therefore, we propose that nucleic acids are a major hydrolyzable P-o pool that are stabilized by the organic C contained in the organic soils of this study. This P-o compound class should be considered in the P-o biogeochemical cycle of these soils.

Automated summary

The study found that the majority of potential phosphorus in these organic soils can be hydrolyzed, with nucleic acids being the most abundant, mainly present in the 0.1 mol L-1 NaOH P pool. This form of organic phosphorus may be bound to the soil matrix, stabilized by organic carbon.