Impact of multiple soil microbial inoculants on biomass and biomass allocation on the legume crop field pea (Fabaceae: Pisum sativum L.)

Authors: GLOGOZA, BEN - North Dakota State University; ALDRICH-WOLFE, LAURA - North Dakota State University; Prasifka, Jarrad; PRISCHMANN-VOLDSETH, DEIRDRE - North Dakota State University

Submitted to: Journal of Sustainable Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2023
Publication Date: 7/13/2023
Citation: Glogoza, B., Aldrich-Wolfe, L., Prasifka, J.R., Prischmann-Voldseth, D.A. 2023. Impact of multiple soil microbial inoculants on biomass and biomass allocation on the legume crop field pea (Fabaceae: Pisum sativum L.). Journal of Sustainable Agriculture. 2(3):314-327. https://doi.org/10.1002/sae2.12060.
DOI: https://doi.org/10.1002/sae2.12060

Interpretive Summary: Microbes are too small to be seen without a microscope, but include many kinds of single-celled and multicellular organisms. Microbes can be harmful, but some kinds of microbes benefit plants by improving growth or plant defenses; these beneficial microbes are sold as formulated microbial inoculants (MI) to be applied to seeds. To understand the effects of MI on field peas, several commercially-available inoculants were tested in greenhouse and field conditions. In greenhouse tests, some treatments increased plant weight, but only during winter when conditions for plant growth were poor. In field tests, the MI that included mixed Bacillus bacteria increased growth of some plant parts, but not total plant weight or weight of seed pods. Across all tests, the mixed Bacillus inoculant appeared to have the most potential benefit, but the results seem to depend on the growing conditions and which aspect of plant growth (roots, green tissues, seeds) is measured.

Technical Abstract: Food production is a global challenge and there is considerable interest in manipulating the rhizobiome using microbial inoculants (MI) to support sustainable agriculture. However, MI and microbial consortia need to be evaluated under diverse environmental conditions, especially for nitrogen-fixing legume crops. We investigated how three commercially-available MI, alone and in combination (B5: five species of Bacillus bacteria, GP: four species of Trichoderma fungi, N2: Paenibacillus polymyxa bacteria), impacted field pea (Fabales: Fabaceae, Pisum sativum L.) in the greenhouse and a two-year field experiment. We found that effects of MI on plant parameters varied. In the greenhouse, two-week-old MI plants had lighter roots and total plant weight compared to non-inoculated controls, but weight of four-week-old MI plants was similar to or heavier than controls, with positive effects of MI only apparent when plants were grown in the winter and likely under greater stress. In the field, the mean percent of plant biomass allocated to the roots was highest in non-inoculated controls, and positive effects of B5 and N2 plants on shoots (and pod densities for B5) didn’t translate into differences in pod weight or total plant weight. In most cases MIX plants, inoculated with B5+GP+N2, performed similarly to those receiving a single inoculant, and percent root colonization by arbuscular mycorrhizal fungi was lower for MIX plants compared to B5 plants. Overall, B5 was the inoculant most often associated with increased biomass. This research underscores the need to consider environmental context and metrics important to agricultural production when evaluating MI.