Bacterial inoculants for rice: effects on nutrient uptake and growth promotion

Abstract

Beneficial soil bacteria are able to colonize plant root systems promoting plant growth and increasing crop yield and nutrient uptake through a variety of mechanisms. These bacteria can be an alternative to chemical fertilizers without productivity loss. The objectives of this study were to test bacterial inoculants for their ability to promote nutrient uptake and/or plant growth of rice plants subjected to different rates of chemical fertilizer, and to determine whether inoculants could be an alternative to nitrogen fertilizers. To test the interaction between putatively beneficial bacteria and rice plants, field experiments were conducted with two isolates: AC32 (Herbaspirillum sp.) and UR51 (Rhizobium sp.), and different nitrogen fertilization conditions (0%, 50%, and 100% of urea). Satisfactory results were obtained in relation to the nutrient uptake by plants inoculated with both isolates, principally when the recommended amount of nitrogen fertilizer was 50% reduced. These bacterial strains were unable to increase plant growth and grain yield when plants were subjected to the high level of fertilization. This study indicated that the tested inoculant formulations can provide essential nutrients to plants, especially when the levels of nitrogen fertilizers are reduced.

Keywords:

• plant growth-promoting bacteria
• inoculant
• nitrogen fertilizer
• nutrient uptake
• Oryza sativa

Acknowledgements

The authors express their special thanks to the company Bioagro Indústria e Comércio Agropecuário Ltda (Santa Maria, Brazil) involved in the production of peat inoculant.

Additional information

Funding

This work was financed by grants and fellowships from the Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS/Brazil); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq/Brazil); and INCT da Fixação Biológica do Nitrogênio (Brazil).