# Indigenous Bradyrhizobium strains enhance nodulation and yield of early maturing soybean in Belgium

## TL;DR

Belgian-native Bradyrhizobium strains improve early soybean growth and yield, potentially replacing commercial inoculants.

## Contribution

Identification of two indigenous Bradyrhizobium strains that outperform commercial inoculants in field trials.

## Key findings

- Indigenous Bradyrhizobium strains significantly improve chlorophyll content and grain yield in early maturing soybean.
- High-Throughput Field Phenotyping confirms strong correlations between rhizobial inoculation and plant vigor.
- Two indigenous strains perform comparably or better than commercial strains in field conditions.

## Abstract

The use of commercial inoculants in Northwestern European soybean cultivation often leads to inconsistent nodulation and yield performance. This study investigates four indigenous Bradyrhizobium strains isolated in Belgium, through a combination of controlled growth chamber experiments and multi-year, multi-location field trials. Results show that the indigenous strains can effectively nodulate early maturing soybean varieties (MG00-000) and significantly improve chlorophyll content and key agronomic traits, including shoot biomass, grain yield and protein content. While no significant differences between strains were detected in growth chamber experiments, field trials revealed variation in strain nodulation and yield characteristics, with two indigenous strains, 521_C7_N1.3 and 590_E5_N4.2, performing comparably or even superior to Bradyrhizobium strains of commercial inoculants (i.e. G49 and 532C). High-Throughput Field Phenotyping (HTFP) using drones confirms strong correlations between rhizobial inoculation and plant vigor throughout the growing season. This approach provided valuable temporal insights into plant growth dynamics and proved to be an effective complementary tool for assessing inoculant performance. Overall, the findings highlight the potential of indigenous Bradyrhizobium strains to enhance soybean productivity in Northwestern Europe, particularly under the climatic and soil conditions of Belgium.