Insights into soil phosphorus bioavailability increase induced by periphytic biofilm decomposition: a comparison with straw decomposition

Abstract

Background and aims

In arable soil, the formation of occluded phosphate restricts the bioavailability of phosphorus (P). Straw incorporation effectively increases available P, but it stimulates CH₄ emission from paddy fields. Periphytic biofilms (PB), growing at soil-water interface, exert significant impacts on physical, chemical and biological characteristics of paddy soil. However, the effects of PB decomposition on P bioavailability remain unclear.

Methods

We conducted a microcosm experiment to explore the pathways how PB decomposition affected Olsen-P by comparing it with straw (ST) decomposition from perspectives of soil porosity, DOM compounds, reducing environment and microbial functions.

Results

Both PB and ST decomposition significantly increased soil Olsen-P concentration, but their pathways differed substantially. PB decomposition primarily enhanced Olsen-P by augmenting soil porosity, recalcitrant DOM compounds, bacterial species richness, bpp gene abundance, and facilitating Fe³⁺ reduction. Conversely, ST decomposition predominantly enhanced P bioavailability by augmenting soil reducibility.

Conclusion

PB biomass decomposition has more significant effects on soil Olsen-P than ST by influencing soil porosity, DOM, microbial community and reducing environment characteristics. These insights will offer valuable perspectives for leveraging PB biomass to improve soil P availability and reduce P input in paddy ecosystems.