Nutrient dynamics of organo-mineral fertilisers in spring wheat at various growth stages: proof of concept study on implications for application timing

Introduction Organo-mineral fertilisers (OMFs) offer a promising strategy to recycle organic waste streams while reducing reliance on mineral fertilisers. However current fertiliser recommendations are only for mineral fertilisers, and OMF applications are being used following this which is not ideal. Nutrient release from OMFs is very different from mineral fertilisers with the latter having more readily available forms to meet crops demands. If we wish to fully optimise OMF use, bespoke fertiliser recommendation is necessary to validate its efficacy.The objective of this proof-of-concept pot experiment is to evaluate timing of nutrient release dynamics from straw- and digestate-based OMF formulations across five key spring wheat growth stages, examining their effects on soil nutrient availability, biomass accumulation, and grain yield under controlled glasshouse conditions. Methods This study involved a full randomised pot study using one OMF formulation derived from straw and two from digestate applied at early tillering and stem elongation. Pots were sampled at five different growth stages to form tillering to harvest to assess nutrient release profile. Results Nutrient availability varies according to both OMF formulation and crop growth stage; digestate-based OMF2 and OMF3 generally maintained greater availability of several nutrients during active crop growth than the straw-based OMF1. Across multiple nutrients, stem elongation emerged as the most responsive growth stage, with marked increases in plant-available nutrient concentrations coinciding with rapid biomass accumulation. Although final grain yield did not differ significantly among treatments, OMF application maintained crop productivity without evidence of yield reduction. Discussion These findings demonstrate that OMF composition influences both the timing and magnitude of nutrient availability, and that formulations with equivalent total N content can exhibit different nutrient-availability patterns during crop development. Shifting the first OMF application towards late tillering/early stem elongation may improve synchronisation between nutrient availability and crop demand. Overall, this study provides a proof of concept evidence highlighting the importance of feedstock selection and application timing in optimising the agronomic performance of OMF for future field trials.