How Much Mycorrhizal Fungi to Use: Complete Soil Application Guide

The amount of mycorrhizal fungi you need to use largely comes down to whether you are using dry or wet application methods. We’ve selected several brands to illustrate the appropriate rates, and you can infer how much you need to apply in your use case. 

All information about a particular brand’s fungi can be found on their website. We are republishing here for user convenience. 

By Application Type

Dry media applications –  The mycorrhizal fungi are applied in a dry or powdered format directly to the soil. We consider this less ideal, as the roots will have to grow into the spores, leaving many spores unused.

Wet media applications – This is where mycorrhizal fungi are applied while in a mixed liquid state. 

Wet Application

MycoMaxx Garden

Mycorrhizal spores are microbes which means very, very small so one or two squirts from a spray bottle is all it takes. When you mix with water and spray the seed or roots these spores will have to opportunity to go into the roots immediately or when the seed germinates giving them the best opportunity for colonization.  

MycoMaxx Garden comes in 2 oz packets. This 2 oz packet is mixed with 1 quart of water. This is designed to cover 100 square feet of garden. 

Q: Do application rates vary with cuttings & starts, veggie transplants, etc.?

Doesn’t matter what you are treating as long as you are spraying directly on the root area.

Dry Application

If your brand of mycorrhizal fungi tells you to mix with growing media, you will need to follow the application rate on your brand’s packaging. 

Dynomyco

https://www.dynomyco.com

With the initial planting of seeds, clones, or seedlings, use 1 tsp. per pint of growing media. Mix uniformly into the growing media before planting. When transplanting into larger containers, apply 1 tsp. per gallon either mixed in growing media or spread in the bottom and sides of the planting hole.

WOW Wallace Organic Wonder 

https://wallacewow.com

Mycorrhizal inoculants must be applied on or near newly developing roots. 

Potting Soil, Soil Amendments and Coco:

Mix 1 pound per 4 cu. ft, 8 pounds per cu yard, or 20 pounds per 70 cu ft (1 pallet) thoroughly into the medium assuring that an abundant amount is present in the root zone. Be sure to add 1-2 teaspoons per plant site in addition to your amending process.

Broadcast and incorporate by tilling or hand mixing into the soil with the seed.

Application rates also vary depending on the situation. See their website for all information. 

Willis Orchards

https://www.willisorchards.com/product/mycorrhizal-fungi

Mix into the backfill when transplanting trees and shrubs. Follow application rates based on the diameter of the planting hole, or on stem capier according to the chart below. Mix the product in a ring-shaped volume of soil around the upper portion of the root ball, extending from the soil surface to a depth of about 8 inches and extending from the root ball outward about 8 inches. See inside pail for detailed application instructions

Rates: 

• Per foot of rot ball diameter – use one 3-ounce packet
• Per caliper inch – use one 3-ounce packet

Supplementary Best Practices

• Always apply to roots – this applies to either dry or wet applications. This maximizes the likelihood of colonization and allows the fungi to establish symbiotic relationships with the plant.
• Avoid using high-phosphorus fertilizers – high levels of phosphorus can inhibit the development of mycorrhizal fungi, so it’s best to avoid these fertilizers for several weeks after the application.
• Check your expiration dates – manufacturers will display an expiration date on the packaging. Be sure to check this! 
• Apply fungi during cooler times of day – To prevent stress on both the plants and fungi, apply during early morning or late evening hours, especially in hot climates.

Conclusion

The amount of mycorrhizal fungi to apply depends on whether you’re using a dry or wet application method. Make sure to follow the manufacturer’s guidelines found on your packaging. Remember that these fungi are powerful tools in promoting healthy, resilient root systems. Happy gardening!