Table 1.
Synthetic view on the potential of microbial inoculants to steer biogeochemical processes in agroecosystems to tackle climate change (CC) challenges
| Type of inoculant | Object | Effect | Modified function(s) | Service regarding climate change (CC) | Demonstration of effectiveness | Examples of ref |
|---|---|---|---|---|---|---|
| N2O-reducing bacteria | Soil | Increased N2O reduction(A) | Decreased soil N2O emissions | CC mitigation through reduced GHG emissions | In soil microcosms and the field: N2O emissions diminished by 28%–189% | (Akiyama et al., 2016; Domeignoz-Horta et al., 2016) |
| Methanotrophs | Soil | Increased biological CH4 oxidation(A) | Decreased soil CH4 emissions and removal of CH4 from the atmosphere | CC mitigation through reduced GHG emissions | In paddy field: CH4 emissions diminished by 6.9%–12% | (Rani et al., 2021) |
| (Engineered) CO2-fixing microorganisms | Soil | Promoted microbial CO2 sequestration(A) | Reduced soil CO2 emissions | CC mitigation through reduced GHG emissions | In culture medium: the CO2 fixation rates achieved were comparable to the capacity of the autotrophic microbes | (Gong et al., 2015) |
| Microorganisms producing EPS-like compounds | Soil | The input of organic compounds like extracellular polymeric (EPS) substances into the soil(A) | Better soil aggregates formation and water-holding capacity | Better crop adaptation to drought/salinity and CC mitigation via better carbon (C) sequestration | In planted soil pots: dry matter yield of roots and shoots increased by 149%–527 and 85%–281% under drought stress | (Ashraf et al., 2004; Sandhya and Ali, 2015) |
| Plant Growth Promoting Rhizobacteria (PGPR) - general | Plant | Stimulated root growth and development(B) | Better water uptake by roots from deep soil layers and enhanced physiological traits of seedlings | Better crop adaptation to drought/salinity | In planted soil pots and the field: plant biomass increased vary from 11% to 87% | (Chandra et al., 2019; Silambarasan et al., 2019; Zhang et al., 2020) |
| PGPR - general | Plant | Increased whole plant biomass production(B) | Better plant carbon sequestration | CC mitigation via better carbon sequestration (if plant C is well managed) | In planted soil pots: plant growth and plant-derived C inputs to soil increased by an average of 42 and 91% under elevated CO2 | (Nie et al., 2015) |
| PGPR producing VOCs | Plant | Production of volatile organic compounds (VOCs)(B) | Better germination, higher plant activities of antioxidant defense enzymes | Better crop adaptation to drought/salinity | In planted soil pots: plant phytohormones increased by 49%–255%; the activities of antioxidant defense enzymes increased by 9%–70% | (Yasmin et al., 2020) |
| PGPR producing IAA | Plant | Production of phytohormone indole acetic acid (IAA)(B) | Adjustment of the timing of plant flowering | Better crop adaptation to CC via modulation of plant phenology | In planted soil pots: plant flowering time delayed by ∼3 days | (Lu et al., 2018) |
| Plant-nodulating rhizobia influencing interactions within the rhizosphere microbiome | Plant | Reshaped community interaction networks (though the same composition)(C) | Modified interactions between microbial populations change their ability to express the genes required to help plants tolerate stresses | Better crop adaptation to drought/salinity | In planted soil pots: the salt stress-induced loss of plant shoot weight diminished by 50% | (Benidire et al., 2020) |
| PGPR Azospirillum lipoferum | Plant | Increased nitrite reducer abundance (up to 60–90%) but only moderately increased abundances of N2O-reducers in sites with high C limitation; decreased nirS-denitrifier abundance (0 to -20%) and N2O reducer abundance (down to -20%) in sites with low C limitation(C) | Increased gross (up to +113%) and net (+37%) N2O production in sites with high C limitation; decreased gross and net N2O productions (-15 and -40%, respectively) in sites with low C limitation | Modification of CC mitigation through GHG emissions (on soils with a high C content, GHG emissions at the regional level can be increased by 2–5%) | In planted soil mesocosms and the field: variable outcomes in situ, from -6% to +25% | (Bounaffaa et al., 2018; Florio et al., 2017, 2019) |
We distinguish the effect directly linked to the inoculant (A) and cascading effect through plants (B) or native soil community (C).