Many are familiar with the symbiotic association of mycorrhizal fungi and plants. So, does turf need mycorrhizal fungi applications too? There’s a movement in the turf care industry marketing the potential benefits of mycorrhizal fungi applications in turf. Therefore, it’s important to ask: Where are mycorrhizal fungi applications most effective? Do we NEED this product on turf? Are there better alternatives to get the effects of mycorrhizal fungi?
I’m here to dig into this topic and contend that encouraging azotobacter bacteria is more beneficial to turf growth.
There are two major groups of mycorrhizal fungi: endomycorrhizal and ectomycorrhizal fungi.
- Endomycorrhiza fungi—specifically arbuscular mycorrhizal (AM)—fungi are the most prevalent in soils. They form structures within the plant roots.
- Ectomycorrhiza fungi—are found to grow between the plant root cells without penetrating them.
Many people believe encouraging, and even introducing mycorrhizal fungi, can benefit the diversity of soil biology. This is especially important in landscapes that include higher orders of plants. Higher order plants include: trees, shrubs and other herbaceous plants.
However, grasses are a rather simple plant. In addition, fungi like more acidic soil than turf grass does. Therefore, when growing grass, encouraging the proliferation of azotobacter bacteria would create a more suitable environment for both.
Azotobacter bacteria are more conducive to environments that grow turf. In addition, azotobacter bacteria do not require a symbiotic relationship with superior plants, yet are able to confer many of the same benefits as mycorrhizal fungi.
Qualities of azotobacter bacteria:
- They are nitrogen-fixing bacteria with the ability to also provide phosphorous to the plant.
- This bacteria relies on oxygen, as such they are most prevalent in soils that exhibit good tilth. (Hennig, 2015, p. 116)
- They are attracted to, and colonize fine root hairs of the plant (Hennig, 2015, p. 116). Therefore, encouraging the development of a healthy root system rather than forced above ground shoot growth as occurs with the application of water-soluble nitrogen through the use of synthetic fertilizer is key.
- Azotobacter are fussy eaters, requiring “easily broken-down substances…and avoid those that are difficult to decompose.” (Hennig, 2015, p. 117)
How to encourage azotobacter bacteria:
- Correct pH
- Reduce compaction – mechanically aerate when necessary
- Provide easily digestible food sources – high quality organic fertilizer
- Encourage the building of humus in the soil
- Avoid synthetic fertilizers with their water-soluble mineral salts
There you have it folks: mycorrhizal fungi has its place…but it’s not in turf.
To read more about the relationships between soil, plants, and other organisms, check out Hennig’s book “Secrets of Fertile Soils”.
Hennig, E. (2015). “Secrets of Fertile Soils: Humus as the Guardian of the Fundamentals of Natural Life”. Acres U.S.A., Greeley, CO.