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

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.

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.

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.

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.