Using P‐Mobilization Traits in Modern Maize Varieties for Optimizing the P Fertiliser Use Efficiency of Struvite Under P Limitation: First Evidence From a Pot and Field Trial

Introduction Current recycling measures for closing the phosphorus (P) cycle are limited by the lower fertiliser use efficiencies of recycled products. Increasing P use efficiency (PUE) through maize genotype selection and management may offer a sustainable solution, but the potential of variety choice and its interaction with placed fertilisation for enhancing recycled fertilisers' efficiency remains unclear. Material and Methods Four maize genotypes differing in P efficiency were tested in a pot trial, where microbial P, phosphatase activity, and Olsen‐P were measured and their links to PUE were investigated. Three of these genotypes were examined in a two year field trial comparing two fertiliser types (diammonium phosphate (DAP); struvite) and application methods (broadcast vs. placed). Results Stabil showed higher microbial biomass P and LG_30258 higher phosphatase activity than other varieties. Although not significant, the PUE, expressed as biomass divided by fertilisation, varied among genotypes ( Amaroc 3.4 x higher than Ricardinio ). In the field, no genotype × management interaction was detected and genotypic differences became minimal ( LG_30258 1.4 x higher than Stabil ). Struvite performed comparably to DAP across both years, while fertiliser placement only increased biomass and P offtake in the drier year, 2022. P mobilisation traits could not predict PUE, however, P offtake in the pot and field trial followed the same ranking order as the P mobilization traits. Conclusion This study highlights that the slow‐release fertiliser, struvite, has a comparable fertiliser efficiency than DAP, and fertiliser placement can further enhance PUE in dry seasons, independent of the fertiliser source. Although slight genotypic variance in P mobilisation exists in modern maize varieties and can predict P responsiveness, the influence of genotype choice and management options appeared additive rather than synergistic since genotype x management interaction was not significant. Future research should further explore how to exploit synergies between genotypes, management, and fertilisers.