Can microbial phosphorus mobilization be primed? Organic fertilisereffect on biological soil phosphorus cycling (PRIME-P)

To promote sustainable crop production, the use of synthetic mineral fertilisers must be reduced. Bio-based fertilisers (BBF) offer a sustainable alternative, but their adoption is hindered by a lack of understanding of their fertilising value and behaviour in soil. This is particularly crucial for phosphorus (P), a finite, non-renewable resource that limits crop productivity in 67% of soils worldwide and is subject to potential supplier monopolies.

The addition of BBF to soil introduces significant amounts of carbon (C) and nitrogen (N), which can greatly influence nutrient cycling driven by soil microorganisms. These microorganisms are key drivers of the P cycle, and their activity is often limited by the availability of C and N. Another source of C in soil is plant root activity, which continuously supplies a small amount of labile C during plant growth. Microbial communities may respond differently to this continuous C supply depending on previous C and N availability.

The overarching goal of the PRIME-P project is to achieve a mechanistic and dynamic understanding of soil P cycling mediated by microorganisms in relation to different forms of C and N introduced by BBF and plant roots. I propose using state-of-the-art approaches to evaluate the effects of BBF and root exudates on microbial P mobilisation. This will allow to address the following specific objectives:

• Identify how regulating soil nutrient balance can positively affect microbial-P processing for plants
• Determine how different BBF additions affect soil OM over time and influence microbial P mobilisation
• Assess whether rhizosphere P priming occurs in soils that have received BBF
• Enhance modelling capabilities for P derived from BBF

These objectives are fundamental for identifying more sustainable agricultural practices that promote nutrient circularity. They will address critical challenges in soil-plant-microorganism interactions, paving the way for scalable, bio-based solutions to sustainable soil fertility and beyond.