# Use of PGPB in bio-fertilisation: preserving the soil microbiome and enhancing field production of alfalfa

## TL;DR

A biofertilizer with plant-growth-promoting bacteria improves alfalfa yield and soil health without harming microbial diversity.

## Contribution

A novel biofertilizer combining valorized horticultural waste and PGPB enhances forage quality and soil microbiome resilience.

## Key findings

- The biofertilizer increased biomass and redirected gains toward improved fiber digestibility or protein content.
- Soil microbial diversity was maintained with shifts toward taxa involved in organic matter degradation and nitrification.
- Inoculants persisted without displacing native genera and reduced soil susceptibility to β-lactam antibiotics.

## Abstract

Sustainable fodder production requires fertilisers that increase yield without compromising soil ecology. We tested whether a humic-rich biofertiliser derived from valorised horticultural waste (ORGAON® PK) could be enhanced with two genomically screened plant-growth-promoting bacteria (PGPB) in a field trial with Medicago sativa. The crude residue substantially increased biomass, and the addition of Bacillus sp. C1 or Pseudomonas sp. C2 further redirected these gains towards improved fibre digestibility or greater protein and energy content. Soil microbial diversity was maintained, although community composition shifted towards taxa involved in organic-matter degradation and nitrification. Both inoculants persisted without displacing dominant native genera, and biofertilised soils showed reduced susceptibility to β-lactam antibiotics. Overall, pairing OPK with targeted PGPB enhanced forage yield and quality while supporting microbiome resilience, highlighting a promising One-Health-aligned alternative to mineral fertilisers. Multi-season trials are now needed to validate broader applicability.

Biological assay infographic illustrating the use of P. agronomica and B. pretiosus for generating biofertilizer. The biofertilizer is applied to a field over five months under rainfed conditions. Results include improved plant nutrition, reduced antibiotic resistance, low impact on community metabolic diversity, and persistent strain presence in the rhizosphere. Conclusions highlight increased plant development and improved nutritional parameters, with minimal impact on community diversity and persistent strain efficacy in treated soils.