Cyanobacteria-based soil amendments in the soil-plant system: Effects of inoculations on soil nutrient and microbial dynamics under spring wheat growth

Authors: ALVEREZ, ADRIANA - University Of Minnesota; Weyers, Sharon; GARDNER, ROBERT - University Of Minnesota

Submitted to: Algal Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2023
Publication Date: 1/1/2024
Citation: Alverez, A.L., Weyers, S.L., Gardner, R.D. 2024. Cyanobacteria-based soil amendments in the soil-plant system: Effects of inoculations on soil nutrient and microbial dynamics under spring wheat growth. Algal Research. 77. Article 103326. https://doi.org/10.1016/j.algal.2023.103326.
DOI: https://doi.org/10.1016/j.algal.2023.103326

Interpretive Summary: Cyanobacteria, nitrogen-fixing green microalgae, show promise as alternatives to chemical fertilizer that can enhance nutrient management and soil functions. ARS and University of Minnesota researchers in Morris, Minnesota, investigated the effects of Anabaena cylindrica and/or Chlamydomonas sp. inoculations on soil microbes, nutrient availability, and nitrogen uptake in spring wheat. Inoculations enhanced microbial biomass and activity and nitrogen and phosphorus availability. Equivalent grain yields were achieved when 75% of applied N was from the cyanobacteria with 25% from urea or 100% was from an cyanobacteria algal mixture compared to 100% from urea. However, the same grain protein levels were obtained if only 25% of the nitrogen applied came from the cyanobacteria. Additionally, increased soil mineral N at spring wheat harvest in inoculation treatments indicates timing of inoculations could be better optimized for plant uptake. These results can be used by researchers and policy makers to support the beneficial role of cyanobacteria-based inoculations as a renewable resource for improving soil quality and plant growth.

Technical Abstract: Cyanobacteria are promising alternatives to chemical fertilizers for nutrient management and preserving soil function. In this study, two pot experiments were conducted to evaluate the effects of inoculations with the cyanobacterium Anabaena cylindrica on an arable Mollisol from the U.S. Upper Midwest and growth of spring wheat. Experiment 1 evaluated surface soil nutrient and microbial dynamics at early stages of wheat development. Experiment 2 evaluated the potential of cyanobacteria-based inoculations (A. cylindrica and/or Chlamydomonas sp.) to replace urea and measured plant growth and soil parameters at three depths at harvest. Experiment 1 revealed inoculation increased surface soil soluble organic carbon (SolC), microbial biomass carbon (C), total nitrogen (N), mineral N, available phosphorus (P), and microbial activity. The N dynamics in soil with and without wheat and plant N uptake demonstrated that plants used N made available from inoculation. In Experiment 2, inoculation had greater effects on surface soil for SolC, microbial biomass C and N, mineral N, and available-P. Grain yield was not statistically different in treatments with 100% N from urea, 75% N from A. cylindrica or Chlamydomonas sp. plus 25% N-urea, and 100% N from an algal mixture. Equivalent grain protein was achieved only when 25% N from urea was replaced with N from A. cylindrica, highlighting the need for optimizing inoculation timing and plant N uptake. These results support the beneficial role of cyanobacteria-based inoculations for soil quality and plant growth, and as renewable resources for agricultural systems.