Enhancement of soil phosphorus mineralization and phosphorus availability by labile carbon in organic amendments through boosting copiotrophic phosphatase-producing bacteria

Abstract

Background and aims

The mobilization of “legacy phosphorus (P)” in agricultural soils could be enhanced through organic material amendment, thereby increasing soil P availability and diminishing the reliance on chemical P fertilizers. This study aimed to elucidate the relationships between these enhancement effects, the decomposition of carbon (C) fractions, and the activation of P fractions.

Methods

Six organic materials differing in C quality and P content were added in a well-fertilized upland Ultisol at a rate of 10 g C kg^–1, followed by a pot experiment with maize (Zea mays L.) cultivation. The relationships between plant P uptake, variations in soil C and P fraction contents, phosphatase activity, and phosphatase-producing bacterial community were investigated.

Results

Compared to the non-addition control, the organic material amendments significantly increased plant P uptake by 66.2%–164%. The decrease in inorganic P in all treatments was far lower than plant P uptake. The decrease in organic P, but not inorganic P, was significantly and positively related to plant P uptake, irrespective of the differences in the amounts of P and its fractions introduced by organic materials among the treatments. Despite contrasting C decomposition patterns among the treatments, only the net decomposition of labile C, O-alkyl C, and di-O-alkyl C were significantly and positively related to plant P uptake. Soil acid and alkaline phosphatase activities both significantly increased during plant growth and were strongly influenced by soil C quality, C fraction contents, and the abundance of copiotrophic phosphatase-producing bacteria, particularly the keystone taxon belonging to Klebsiella.

Conclusion

The findings of our study collectively suggest that the enhanced plant-available P under organic material amendment in the “legacy P”-containing soil is primarily due to the labile C-induced acceleration of P mineralization, irrespective of the material P properties. This acceleration is associated with the proliferation of copiotrophic phosphatase-producing bacteria regulated by labile C inputs to soil rather than P inputs.