University of Maine Cooperative Extension agriculture research faculty collaborated with a local organic grower and the USDA-ARS Reasearch Center in Wyndmoor, PA to evaluate the potential of mycorrhizal fungi, to boost yields in field grown leeks using both a commercially available mycorhhizal innocula and a “farm raised” mycorrhizal innocula. The farm raised innoculum was produced using a technique developed at the Wyndmoor, PA research facility, and both the farm raised and the commercial mychorrhizal fungi innocula treatments were compared to a control treatment using no mycorrhizal innocula. The study was conducted at both the Highmoor Farm Experimental Horticultural Research Station in Monmouth, Maine and at Wolf Pine Farm, an organic CSA Farm located in Alfred, Maine. Leeks were chosen for this study in 2010 for their low pest profile, market value, and ease of harvest and data collection.
Data collected in the 2010 leek study at both farm sites indicated that the leeks treated with the “farm raised” mycorhizal innocula yielded more than 20 percent higher by weight than the control, uninoculated leeks (see Table 1). Yields from the leeks treated with the commercial innocula did not yield significantly different from the control.
- Table 1. Mean Wt. in grams of leeks at harvest from each of the three treatments, data from both farm sites combined.
Mycorrhizal fungi have long been demonstrated to enhance crops’ ability to mobilize and take up soil nutrients, particularly phosphorus, aid in water uptake and reduce disease pressures. However they have not been used extensively in vegetable crop production. In recent years commercially raised innocula has started to become more widely avaiable and some farmers are beginning to adopt their use, though potential benefits are not well documented.
Evaluate whether innoculating leeks with mycorrhizal fungi at the time of seeding in flats would lead to an increase in yield, using two sources of innocula, farm raised, commercially produced, and comparing them to a control (uninoculated) at two farm sites, Wolf Pine Farm in Alfred, ME and Highmoor Farm Experimental Station in Monmouth, Maine. These objectives were completed during a successful 2010 field studies at both farms.
Performance Targets Achieved:
• On Farm Production of Mycorrhizal Fungi Innocula using technique developed by USDA-ARS Research Station in Wyndmoor, PA
• Leeks grown in seedling flats with three treatments: 1. Farm Raised Innocula; 2. Commercially Produced Innocula: 3. Control (no innocula)
• Field Planting in Randomized Complete Blocks experimental using standard agricultural practices for each farm (conventional at Highmoor Farm and organic at Wolf Pine).
• Data collected at harvest included weight of rinsed leeks, length, diameter, and evaluation of disease.
• Data analyzed
The project had two phases.
Phase 1: On-Farm Mycorrhizal Production: Conducted during the 2009 growing season to produce an on-farm source of mycorrhizal fungi to be used in the field study during the 2010 growing season. In June of 2009, bahiagrass (Paspalum notatum Flugge) seedling plugs from the ARS research center colonized by Glomus claroideum; Glomus mosseae; or Glomus intraradices; and non-mycorrhizal (15 plants each) were shipped to University of Maine Cooperative Extension, York County for planting on-farm in a greenhouse at Wolf Pine Farm in Alfred, ME. The inoculated bahiagrass plants which are excellent colonizers of mycorrhizal fungi were grown in 7 gallon grow bags containing 9 parts vermiculite to 1 part compost through the fall when until they winter killed. Bahiagrass seedlings which were not inoculated were also grown simultaneously with the inoculated plants, to serve as a control study and for an additional treatment using a commercial inoculant(See Photo). Soil media from the grow bags was sent to the ARS research station to document colonization and spores/gram concentration. In 2010 the soil media from the bags of the three species was mixed together to create a blend of all three species of mycorrhizae. The inoculum free bahiagrass grow bag medium was also stored for use in 2010.
Phase 2: Leek Mycorrhizae Field Study:
Soil Media. Living Acres, NP Mix soil less medium was used at each farm location.
Treatment 1 – Mycorrhizal On Farm Inoculum: The soil media described above was mixed 9 parts media to 1 part of the compost/vermiculite mix containing the on-farm produced mycorrhizal fungi inoculum. Leeks, variety Pandora were seeded in the greenhouse at each farm location on June 2, into the described media, in standard trays with 72 1-inch cells per flat (See Photo).
Treatment 2 – Mycorrhizal: The soil media described above was mixed 9 parts media to 1 part of the compost/vermiculite mix from the non-inoculated bahiagrass plants, and mixed with the commercially produced inoculum, Myco Grow. The commercial Myco Grow inoculum was prepared by mixing according to instructions, 1 oz. per 12 gallons of water and was watered in after seeding the trays.
Treatment 3 – Control: The soil media described above was mixed 9 parts media to 1 part of the compost/vermiculite mix from the non-inoculated bahiagrass plants.
The seedlings were watered in a greenhouse at each of the two farm locations as needed and supplemental fertilizer was added via watering once weekly with BioGrow, a low phosphorus certified organic fertilizer, to avoid inhibiting mycorrhizae colonization (N-P-K analysis: 2 % N – 0.1% P – 6.6% K).
Field Experimental Design: On July 12, the inoculated and control seedlings were planted in the field at each farm location using standard farm field practices including pre-plant additions of (Wolf Pine farm) organic fertilizers such as rock phosphate and fish meal, and (Highmoor farm) a complete commercial fertilizer blend, per soil test recommendations. At the same time the plants were being set out in the field, root samples from additional plants from the same treatments were taken and sent to the ARS for analysis to document adequate colonization of the leek plant roots. The field research plots were planted in a randomized split block experimental design with 15 plants per replication of each treatment for total of 45 plants per replication. There were 6 replicate blocks at each of the two farm sites. The plants were spaced at 6-inch intervals in the row with 18 inches between rows and the plants were weeded and fertilized according to standard farm practices.
During the growing season the plants were visually monitored for growth and any incidence of pathology. At Wolf Pine Farm Alternaria porri (Purple blotch) damage was noted in early August and confirmed by the University of Maine Pest Management Lab. Minor thrip damage was also noted and confirmed by our pest management lab.
The leeks were harvested on November 12 and 18 at Highmoor and Wolf Pine Farms respectively. Data was be collected from the middle 9 plants in each of the 6 replicate blocks, graded as # 1 for market, # 2 for non market home use and # 3 for culls, and pre-trimming weight per plant was noted. A statistical data analysis was performed to determine if there are significant differences between treatments.
Data collected in the 2010 leek study at both farm sites indicated that the leeks treated with the “farm raised” mycorhizal innocula yielded more than 20 percent higher by weight than the control, uninoculated leeks (see table). Yields from the leeks treated with the commercial innocula did not yield significantly different from the control.
Table 1. Mean Wt. in grams of leeks at harvest from each of the three treatments, data from both farm sites combined.
Mean Wt. in Grams of the Three Treatments – Both Farms Combined
Treatment Mean Wt. in Grams LSD, P = 05*
1. Farm Raised Innocula 9.2470 A*
2. Commercial Innocula 7.7373 AB
3. Control (no innocula) 7.0300 B*
* indicates statistical significance, A is different from B, P value less than .05.
Leeks treated with our farm-raised “home grown” inoculum produced 21% higher yields than either the control or the commercial inoculant used. The fact that the MycoGrow commercial inoculum used as directed, did not produce any difference in yield, and that at the time of planting in the field showed 0 colonization by mycorrhizae on the roots of this treatment in analysis at the ARS lab, suggests that additional commercial mycorrhizal fungi inoculums available on the market should be evaluated. Are farmers that are spending money to purchase commercially raised inoculums getting results? Are there commercially available inoculants that work better than others?
Also of interest for further studies would to develop a method to make the farm raised “home grown” inoculum from the bahiagrass available for farmers. In this study we were able to grow our own since we had access to the pre-inoculated seedlings from the ARS Research Station in Pennsylvania. The ARS lab was also able to assure that we had adequate spore levels in our inoculum raised on the farm. In a subsequent study it would be interesting to set up the ability at the University of Maine to pre-inoculate bahiagrass seedlings and make these available to farmers to grow there own source of inoculum.
It should also be noted that this data is from only one year’s field study. The experiment is being repeated in 2011 at Highmoor Farm comparing the farm-raised inoculum to two different sources of commercial inoculum. Should we get a similar result in 2011, this would warrant further study as suggested above.
Education & Outreach Activities and Participation Summary
Reporting on findings at MOFGA Common Ground Fair (September 2010), York County Farmers Network Meeting, December, 2010, Master Gardener Volunteers, April, 2010. Will report on final study after 2011 field data analyzed at NE Fruit and Vegetable Growers Northeast Regional Meeting.