Fertilisers with a replacement of P and K sources by others of bio-based origin and supplemented with microbial plant biostimulants: agronomic performance in field trials and effect in soil microbiome diversity
The European Union Farm to Fork strategy faces two major challenges for agriculture: efficient nutrient recycling strategies to promote a bio-based Circular Economy and a 25% reduction in the use of conventional inputs, including fertilisers and pesticides. To address the first challenge, this work tested the partial substitution of raw materials for the production of mineral fertilisers by others of bio-based origin to produce granular bio-based mineral fertilisers (BBMF), as well as the use of granular organic-mineral fertilisers (OMF). The research gap to cover was the unvalidated BBMF nutrient release in fields, untested MPB-fertiliser interactions. The trials were conducted on large plots (1296 m 2 per treatment and replicate). Four BBMF trials (2 in Spain, wheat; 2 in Portugal, maize) and 2 OMF trials (Spain, wheat) during 2021/2022 and 2022/2023. To address the second challenge of reducing the dose of conventional fertiliser, the addition of Plant Growth Promoting Rhizobacteria (PGPR) as microbial plant biostimulants (MPB) to the granular BBMF and OMF was tested in the same fields. Our results indicate that, in terms of crop yield, conventional fertiliser can be replaced by BBMF supplemented with MPB at a reduced dose of 75% of the traditional one. The reduced dose of BBMF+MPB resulted in an increase in yield compared to the conventional mineral fertiliser in all trials. Also, the use of OMF+MPB increased (6% to 11%.) the yield obtained with OMF alone at the same rate. Soil microbiome biodiversity is a key parameter linked to soil quality and the use of BBMF+MPB and OMF+MPB respects the biodiversity of the soil microbiome (evaluated using a metataxonomic approach), as no reduction in biodiversity parameters was observed and, in several cases, an increase. Thus, the use of BBMF+MPB and OMF+MPB allows the reduction of fertilisers, improving soil quality and crop yields, supporting the principles of the circular economy and promoting sustainable agricultural practices.