Microbial inoculants were applied to the soil and foliage of wine grape vineyards in an attempt to decrease the use of, or decrease the damage caused by the use of copper as a fungicide.

A 2-year program was implemented using compost, compost tea, and endomycorrhizal (VAM) spores. The copper usage was reduced by 37.5% and the soil friability was noticeably improved. During the same period, lime and sulfur in the spray schedule were eliminated.

The microbial inoculants were successfully applied to the vineyard by using a newly purchased low impact spray machine, and an aerobic compost tea machine to maximize the effectiveness of the inoculants. The results of laboratory analysis of soil and foliar samples document that noticeable improvements occurred in the soil structure as well as in vine health.

Objectives/Performance Targets

The primary objective of this research was to document the effectiveness of microbial inoculants on reducing caustic spray materials, increasing vine grape yield, increasing grape fruit quality (Brix), reducing pest and disease incidence, and increasing quality of microfauna in the soil, while sharing the results and methods of applying compost teas or other inoculants to plant and soil with other interested growers.

Accomplishments/Milestones

In the second year, the four original test plots continued to receive the microbial inoculant applications set up in the first year, but at a less frequent interval (every two weeks or compost tea instead of weekly). At the end of the season, soil samples were sent in to Soil Foodweb, Inc. for analysis. The results were compared to the original soil microbial tests to determine progress in soil structure. Vine health, brix levels, fruit disease and foliage disease levels were also monitored.

Results of the first year’s experiments were posted on Maple Ridge Vineyards’ website, and were also posted and discussed on the "Organic Viticulture" discussion group. Private tours were given at Maple Ridge Vineyard throughout the two-year period, and many questions were answered via phone from interested callers. Maple Ridge Vineyard’s brochures that are distributed to the general public contain a short summary of the project.

We have worked with OARDC and Ohio State University’s Ashtabula Grape Research branch to answer questions from new growers about organic viticulture and the inoculant program.

Impacts and outcomes

Improved soil structure continued to be the most observable difference in test plot #1. This experiment applied compost tea to the soil and foliage of mature Chardonnay grapevines. Aerobic compost tea, brewed in either the KIS or EPM compost tea brewer was made from the humus of rotted stumps collected from an undisturbed area of mature hardwood trees at the back of the Maple Ridge Vineyard property. Compost from on-site, humic acid, kelp, and fish hydrolysate were also used in the tea recipe. The teas were tested by Soil Foodweb, Inc to be sure they contained the proper microbial content. Teas were applied weekly the first year and biweekly the second year. Improve soil friability was observed during weeding and tillage operations. Besides the ease of passing a subsoiler, noted the first year, hilling up vines in the fall was easier because the soil would "crumble" into place instead of "clump".

This can also be noted on the soil foodweb analysis. MRV’s active fungal biomass increased from 104 ug/g to 192 ug/g. Total fungal biomass increased from 179 ug/g to 376 ug/g. This caused the active fungal to active bacterial biomass to increase from 1.17 to 2.39, placing it in the range of soil aggregate structure required for deciduous trees or vine crops. The old range was suitable for grassland. See the Foodweb Analysis chart.

The Chardonnay fruit crop maintained a consistent 2ton/acre yield with very "clean" disease free fruit. There were no sulfer or lime-sulfer applications as a powdery mildew fungicide in 2005. The tea application kept powdery mildew at 0%. Five sprays of copper were applied to control black rot in 2005, eight sprays in 2004 (plus some sulfer and lime-sulfer in the spring). Black rot (Gwinardia bidwellii) remained < 2% incidence both years in control rows and tea rows even with the decrease in copper applications. A neighboring Chardonnay vineyard receiving no sprays of any kind suffered a 99% loss of fruit to disease in 2004, and 75% in 2005.

Downy mildew, a foliar disease, was well controlled in 2004. The last copper spray was on August 2, two sprays of compost tea and two foliar sprays of calcium were applied after that. Downy was not as well controlled in 2005. The last copper spray was July 17th, two more foliar tea sprays, and two foliar calcium and potassium sprays were applied after that. The difference between the control rows and tea treated rows in terms of disease was unobservable. Dr. Elaine Ingham of Soil Foodweb, Inc. has suggested that this may be due to the proximity of the treated and untreated rows. Apparently, microbes like to migrate.

MRV’s organically certified fruit has fewer incidences of botrytis, brown rot, and grape berry moth damage than the conventionally farmed grapes in our area. Our distal foliage, however, usually shows 20-30% higher incidence of disease. This may be due to the decrease in frequency of sprays in the month of August, and requires more research.

The tea treated rows continued to have 0.5-degree higher brix at harvest a difference of about 2.5% in the final sugar content. There were no insect problems or phyloxera in 2005.

In experiment #2 the new Chardonnay vines with tea treatment continued to be 25% taller and some had fruit this year. The control rows did not.

Experiment #3 with new Pinot Noir vines inoculated with VAM at planting continued to be 25-50% taller than the new vines that were not inoculated.

Experiment #4 inoculated mature vines at Markko vineyard with VAM. Although the soil analysis showed these vines went from 0% colonization to 4% colonization of their roots, there were no other measurable differences. Colonization should be 40-80% to be most effective. There might be more effective ways to inoculate mature vines than what was used in this experiment. At MRV colonization of the mature vines flectuates, but never came into the good range.

A commercial liquid compost inoculant was purchased and one application applied to the Tarsitano vineyard. There were no measurable differences. These products are fairly expensive and probably require multiple applications.Wines made from the tea sprayed grapes at MRV continued to need fewer nutrients at fermentation than the conventional grown grapes MRV used to make wine. This was discussed with other vintners at the Terre Madre conference in Turin, Italy in 2004.

Conclusion

Compost tea can improve the soil structure. Maple Ridge Vineyard started with a compacted hard to work clay soil. After two years of compost tea applications, the fungal communities, which give soil its structure, were 100% higher. Ciliates indicating that the soil is anaerobic and compacted went from a high level to 0.

The application of VAM at planting time improved new plant growth in height by 25 to 50% in these experiments. This is an inexpensive and easy to apply inoculation at planting time.