Abstract
In this study, we determined whether inoculating sorghum (Sorghum bicolor (L.) Moench cv. NK-3657) seedlings with a vesicular arbuscular mycorrhizal (VAM) fungus (Schenck and Smith) would enhance plant yield under drought conditions.
Seven-day-old seedlings were inoculated with the fungus and irrigated to field capacity for an additional 7 days. Daily irrigation treatments of I1 (dry, -0.56 to -1.4 MPa), I2 (moderately dry, -0.15 to -0.48 MPa), and I3 (wet, -0.03 to -0.06 MPa) were then imposed with a line-source sprinkler.
Under moderately dry soil conditions, growth, photosynthetic rate, and stomatal conductance of G. intraradices-colonized sorghum plants were significantly greater than in uncolonized plants. Results indicate that the VAM fungus enhanced yield of sorghum plants under drought conditions.
Why This Research Matters
This study demonstrates one of the core benefits of mycorrhizal inoculation: drought resistance. When water is limited, plants with established mycorrhizal networks are better equipped to maintain photosynthesis, stomatal function, and yield. This has important implications for agriculture in water-stressed regions.
Big Foot Mycorrhizae products contain Glomus intraradices (now classified as Rhizophagus irregularis) — the same species studied here — along with additional endomycorrhizal species for broad-spectrum coverage across plant types and conditions.
Implications for Dryland and Row Crop Farmers
Sorghum is a model crop for dryland agriculture — it's already bred for drought tolerance, which makes this finding especially meaningful. Even in a crop selected for water efficiency, mycorrhizal inoculation produced significantly better results under moderately dry conditions. The improvement in stomatal conductance in particular points to a mechanism: mycorrhizal plants are better able to regulate water loss while keeping photosynthesis running, rather than simply shutting down under stress.
For farmers and growers dealing with variable rainfall, this research supports a simple decision: inoculate at seeding. The cost of inoculant is negligible compared to the yield risk from a mid-season drought, and the insurance value compounds over multiple seasons as the fungal network matures in the soil.
Key practical points from this study:
- Inoculate seedlings early — the 7-day pre-treatment gave the fungi time to colonize before drought was imposed. Early establishment is the key to maximizing benefit.
- Benefits are greatest at moderate drought, not severe. Moderately dry conditions (I2 in this study) showed the clearest advantage. This aligns with real-world conditions where irrigation is being rationed or rainfall is below average.
- The same fungal species is in Big Foot. Rhizophagus irregularis (formerly G. intraradices) is one of the most widely studied AMF species and is a primary component of Big Foot Mycorrhizae products.
The same fungi. Proven in the field.
Big Foot contains Rhizophagus irregularis and multiple endomycorrhizal species — for broad drought protection across crops.
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