Biological products improved tomato crop growth and altered soil nutrient levels without changing microbial community composition

Abstract Background and aims Alternatives to synthetic fertilisers for field-grown crops are needed to increase crop production. This study investigated the application of three commercial biological products, Popul8 (microbial), Eco-Humate (organic-acid) and Eco-Vital® (fish + seaweed) to field-grown tomatoes and their impact on crop growth, soil properties, and the microbiome. Methods Field trials were conducted at two farms in the 2022/2023 (Trial 1) and 2023/2024 (Trial 2) tomato cropping seasons during the Western Australian summer. Biological products were applied concurrently with synthetic fertiliser at one farm (conventional), while the second farm had only the products applied (non-conventional). Crop biomass, yield, and soil physicochemical properties were measured. DNA from rhizosphere and bulk soil samples was sequenced to assess bacterial and fungal communities. Results Crop biomass and yield were generally higher in biological product-treated plots at both farms, possibly due to changes in soil nutrient levels. The rhizosphere and bulk soil microbial community composition differed significantly between Trials 1 and 2 at both farms. Biological products did not change the community composition in any trial; however, relative abundances of some beneficial microbes, such as Rhodotorula were increased. Conclusion The findings suggest that the biological products used in this study could be an alternative to synthetic fertilisers, and this may have a positive impact on tomato crop production. Product application to the same plot and over multiple seasons in a standard crop rotation is expected to have a more substantial impact on bacterial and fungal communities, to advance microbiome-mediated sustainable crop production.