Please visit our web site at: http://www.oardc.ohio-state.edu/grape

Reminder: Site Inspection for Vine Grant Program by Maurus Brown

The Vine Grant program provides a good incentive to grape growers to expand wine grape production in Ohio. To qualify for Vine Grants, growers must follow the program guidelines. As in the past, the Extension Viticulturist will conduct site evaluations and determine the overall qualifications of the applicant. Questions that relate to filling out the application can be directed to the Extension Viticulturist.

To maximize the success of this program, each grower is required to adequately prepare the vineyard site for planting wine grapes. Prior to establishing vines, a vineyard site evaluation must be conducted by the Extension Viticulturist to determine if the location is appropriate for growing wine grapes through several years of production. A pre-approval site inspection will help the grower and OGIC to determine the overall potential that each grower will have in raising grapes. Growers will also have to fill out a pre-approval form that describes their agricultural background and expertise in growing grapes or other fruit crops. A listing of available equipment is required to help evaluate the ability of each grape grower to maintain good viticultural practices. OGIC would like to have each acre established under the Ohio Vine Grant program to be fully productive for several years.

Upon completion of the pre-approval application, the applicant should return the completed forms directly to the OGIC. Each applicant will be responsible for contacting the Extension Viticulturist to set up a vineyard site inspection. The OSU Extension Viticulturist will be responsible for conducting appropriate on site inspections for pre-approval and follow up with additional visits to determine if grower has prepared, planted and maintained the vineyard in an appropriate manner. These evaluations will be conducted to assure that all guidelines of the grant program are met.

OGIC will be responsible for the pre-approval of growers, approve the final Vine Grant applications, and determine what dollar amount should be granted to each applicant.

Plant Tissue Testing for Grapevines by Maurus Brown

Leaf petiole analysis is important for monitoring nutrient deficiencies and diagnosing causes of abnormalities in grapevine growth and fruit development. By evaluating petioles of the grape leaf on a yearly basis you can help to determine what elements are lacking in the grapevine. For the best interpretation of results, leaf petioles should be sampled by variety over a 4 to 5 year period, which can help to establish a trend of nutrient levels in the vineyard. Grapevines are very adaptable and can grow on a wide range of soils, however, as with any crop, a vine does require a good fertility program to sustain top production. If a vine is stressed due to inadequate fertilizer, it does not produce high yields or good quality fruit.

Elements such as carbon (C), hydrogen (H), and oxygen (O) are readily available to plants through contact with air and water. Other macronutrients including nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) should be added to the soil/foliage on a need basis. There are distinct characteristics of plant reaction to nutrient deficiencies that include: N = general chlorosis of older leaves, poor vine vigor, low yields; P = poor berry set, redding of older leaves; K = chlorosis along the edge of leaves, poor vine vigor, and may be related to high Mg⁺⁺; Mg = yellowing along the edge of leaves, general chlorosis of older leaves, and may be due to excess K⁺. Macronutrients levels in grapes petioles are considered normal when N = 0.9-1.3 %, P = 0.16-0.29 %, K = 1.5-2.5 %, Ca = 1.2-1.8 %, and Mg = 0.26-0.45%.

Micronutrients boron (B), manganese (Mn), copper (Cu), and zinc (Zn) can be applied to deficient vines by spraying a liquid formula on the canopy at recommended rates during the growing season. A deficiency in B or Zn will cause poor fruit set in the form of shot berries. Low levels of Mn will appear as chlorosis of older leaves and Fe deficiency is a distinct chlorosis (bleached look) on younger leaves. Deficiencies in micronutrients can be corrected during the growing season in which petiole samples were taken. Micronutrient levels are considered adequate when Mn = 31-150 ppm, Fe = 31-50 ppm, Cu = 5-15 ppm, B = 25-50 ppm, and Zn = 30-50 ppm.

Samples (60 petioles) are generally taken annually from July 1 to August 30 for each variety. Do not mix varieties, each should be submitted for analysis separately. Be sure to gather your petiole samples in a random pattern in the to avoid potential bias in selecting leaves from only a few vines. Take petioles from leaves of the same maturity to assure consistency of plant samples. Try to select leaves that are fully expanded and mature, and care should be taken to not sample from older leaves that nearing senescence. Detach the leaf blade upon extraction from the plant, bundle petioles together, place in brown paper bag, and carefully label as to date, location, and variety sampled.

When submitting petiole samples for analysis, a grower must fill out a plant tissue analysis form, which instructs the individual processing your samples as to the type of test(s) you wish to have conducted. Information given by the grower will provide the type of crop, date planted, date sampled, soil type, soil moisture prior to sampling, soil pH, recent history of fertilizer and lime applications, and recent herbicide applications.

For additional information refer to the following OSU Extension bulletins, which can be obtain at your local county Extension office. See Table 1 for a listing of potential soil and plant tissue testing facilities. After the lab has completed your samples you may contact the Extension Viticulturist for assistance in evaluating results and determining what fertility program should be implemented.

Bulletin 815 Grapes – Production, Management, and Marketing

Bulletin 458 Fertilizing Fruit Crops

Bulletin 861 Midwest Small Fruit Pest Management Handbook

Bulletin 72 Ohio Agronomy Guide

- Brookside Labs, 308 S. Main St., New Knoxville, OH 45871, (419) 753-2448.
- CLC Labs, 325 Venture St., Westerville, OH 43081, (614) 888-1663.
- Calmar Lab, 130 S. State St., Westerville, OH 43081, (614) 523-1005.
- Na-Churs, 421 Leader St., Marion, OH 43302, (800) 622-4877.
- Spectrum Analytical Inc., P.O. Box 639, Washington Court House, OH 43160, (800) 321-1562.
- Agricultural Analytical Services Laboratory, Pennsylvania State University, University Park, PA 16802, (814) 863-0841.
- Darryle Warncke, Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824, (517) 355-0210.
- A & L Great Lakes Lab, 3505 Conestoga Drive, Fort Wayne, IN 46808, (219) 483-4759.

_______________________________________________________________________

You may also obtain additional information by accessing the web site: http://www.ag.ohio-state.edu/~agnatres/forms/soillabs.pdf.

Often producers are too busy to cluster thin near bloom, which is the suggested time. In order to have information and answer the question, "What will happen if I thin later?", we established a study beginning in 1996 to see the effects of not thinning and thinning at bloom or 2, 4, or 8 weeks after bloom. All vines were pruned to leave 50 buds per vine. The first year yield on thinned vines was 50% less than on unthinned vines, but in subsequent years the yield reduction due to thinning was 10-15%. Thinning generally increased cluster weight with the effect decreasing as thinning was delayed. In 1996, with a big difference in yield, all thinning treatments increased soluble solids, but in subsequent years with less difference in yield, the effect on soluble solids was small and often not significant. Generally, pH was increased by thinning and the effect increased as thinning was delayed. We are continuing this study this year, but early results indicate that the greatest effects of thinning occurred in the first year and thinning at bloom gave the most desirable results. As thinning was delayed, yield in subsequent years declined. However, effects on fruit quality due to different times of thinning were small. We have not had a severe cold event during this trial to see any effects on vine survival.

Malolactic Fermentation (NILF, often referred to as secondoy fermentation) is the conversion of the stronger, dicarboxylic malic to the weaker, monocarboxylic lactic acid and CO,. It is carried out by lactic acid bacteria (LAB, preferably Oenococcus-!@@ent) generally after the alcoholic fermentation (often referred to as primary fermentation). LAB use malic acid as energy source, but they can also utilize sugars, amino acids and phosphate containing compounds. MLF has two meanings: 1) the growth of LAB in wine and the associated flavor changes, and 2) the biochemical pathway of the utilization of malic acid. Malic acid is transported into the cell where it is decarboxylated (splitting off C02) to lactic acid by the malolactic enzyme. Lactic acid is then transported out of the cell. Since malic acid is weaker than lactic acid the acidity is lowered and the pH increased in the process. The CO., which can be noticed by the formation of rings of bubbles on the wine surface, is normally lost during subsequent rackings.

Malolactic fermentation is employed by winemakers to achieve the desired acid balance and flavor complexity in a wine. Lower acidity (softer, finer texture with a longer aftertaste) and increased mouthfeet (texture and length of aftertaste) are the main benefits in many white and red wines, but also in base wines of some styles of sparkling wines (addition of yeasty, toasty, nutty and oaky aromas). All malolactic starter cultures can provide these benefits, but they differ in how they affect a wine. Contrary to common belief fruitiness of wines is not necessarily destroyed by MLF, it can even be enhanced. During MLF vegetative aromas can be reduced which may unmask fruity, floral and spicy aromas. Fruity flavors can be increased through glycolytic side activities of LAB. On the other hand some strains produce strong buttery, yeasty, and sweaty aromas which can cover up fruity flavors. One of the compounds produced by LAB is diacetyl (buttery aroma). The amount produced depends on the strain and can therefore be influenced by the choice of bacteria. All LAB bacteria can also reduce diacetyl to acetoin which is flavorless at the concentrations found in wine. The reduction of diacetyl (and the buttery aroma) can therefore be increased by leaving the wine longer in contact with the bacteria. The addition of a fresh yeast culture also decreases the amount of diacetyl because the yeast reduces diacetyl to acetoin ("yeast fmwg"). Once the desired diacetyl concentration has been reached, the wine should be clarified (racked, filtration) and sulfited to avoid further microbial growth. The chemical nature of the yeasty, sweaty, "lactic" (sauerkraut?) and oaky aromas produced during MLF is not yet known. The softer, fmer texture and the longer aftertaste in MLF wines is caused by the lower acidity and the production of polysaccharides and possibly amino and nucleic acids. The glycerol content ("viscosity") however is not changed during MLF unless spoilage with Pediococcus and Lactobacillus occurs. MLF can also decrease astringency (gelatin index). In tanks it might decrease total phenols (as measured at 280nm), but could increase them in barrels due to extraction from the wood. Acetic acid is always produced during MLF (0.2-0.3 g/1), but is sensorially not noticeable at these concentrations. However the formation of esters of acetic and also lactic acid does have a sensory impact. Generally, MLF lowers the color intensity (more so in tanks than in barrels) and changes the hue (lower proportion of 520nm). Color can also be stabilized, particularly in barrels, due to tannin-anthocyanin condensation. In addition MLF increases polymerization of tannins and anthocyanins.

As a summary, the aroma and flavor characteristics of an MLF depend on the flavor precursors in wine derived from the grapes and the yeast, the type (strain) of bacteria used, the interaction with oak or a tank, and the activity of microflora following the MLF. The quality of an MLF and the length of its (positive) impact depend on the fruit (sound fruit -unbroken, without infection of spoilage yeast, bacteria and molds), good winery sanitation to avoid spoilage, post-MLF treatment (SO2, filtration), and the use of a sound and active starter culture.

Henick-Kling, Thomas, and Acree, Terry. 1998. Modification of Wine Flavor by Malolactic Fermentation. New York Wine Workshop. April 3-4. Geneva.

Riesen, Roland. 1992. Undesirable fermentation aromas. Proc. of the Wine Aroma Defects workshop. July. Corning, NY.

 

 

Often sorbic acid (potassium sorbate) is used to inhibit yeast growth in sweet table wines at 150 to 200 mg./L. On the other hand, sorbic acid does not control the growth of bacteria. When sulfur dioxide is too low to deter bacterial growth, certain malolactic bacteria can metabolize sorbic acid to yield a disagreeable odor (geranium-like) in wines. Also, it should be noted that sorbic acid may be detected at low levels. Using a trained taste panel, Ough and Ingraham (2) reported that the threshold for detecting sorbic acid in a Pinot noir wine was 135 mg./L. However, the panel was trained for this study to detect sorbic acid, and one panelist was very sensitive to sorbic acid. Before training panel, the individuals had difficulty detecting the odor or taste of sorbic acid in the wines. Ough (2) reported that wines treated with sorbic acid develop ethyl sorbate, which most people can not detect at levels normally present in wines.

The effectiveness of sorbic acid is related to the number of microorganisms found in wines. Heavy microbial counts may lower the sorbic acid content. Yeast and bacteria are capable of metabolizing sorbic acid; thus, reducing its ability to control spoilage. Therefore, it is important for the winemaker to use some common measures to control high cell counts such as, using clean and sound fruit, juice clarification, and wine filtration.

Another disadvantage of using sorbic in the form of potassium sorbate is that this salt contains a small amount of potassium, approximately 25% by weight. If sweet wines are not adequately stablized against potassium tartrate precipitation, an additional amount of potassium may cause tartrate crystals. The winemaker needs to make sure that the wine is thoroughly tested for tartrate formation prior to bottling.

Ough, C.S. 1987. Chemicals Used in Making Wine. C. & E.N.: Jan. 19-28.

Ough, C.S. and L.J. Ingraham. 1960. Use of sorbic acid and sulfur dioxide in sweet table wines. Am. J. Enol. Vitic. 11:117-122.

June 18-19, 1999 - Vintage Columbus, Dublin. Contact OWPA at phone: 440-466-4417 and e-mail: winchell@knownet.net for details.

June 28-July 2, 1999 - ASEV meeting. 50^th Annual Meeting, Reno, Nevada. Contact ASEV at phone: 530-753-3142, fax: 530-753-3318, or e-mail: asevdavis@aol.com for details.

July 14-17, 1999 - ASEV-ES meeting. Oak Symposium: Oak forests, wood selection, barrel manufacture, and winemaking. Contact Ellen Harkness at fax: 765-494-7953 for details.

July 27, 1999 – Southern Ohio Vineyard and Winery Tour. Tour will begin at Painter Fork Vineyard (Mark Nissel) in Clermont county, continue on to Kinkead Ridge Vineyard (Ron Barrett) in Brown county, and conclude with winery tour and dinner at Moyer’s Vineyard, Winery, and Restaurant in Adams county. For more details contact Maurus Brown at phone:330-263-3681 or e-mail: brown.989@osu.edu.

August 6-7, 1999 - Vintage Ohio, Lake Farmpark. Contact OWPA at phone: 440-466-4417 and e-mail: winchell@knownet.net for details.

January 16-20, 2000 - 5^th International Symposium on Cool Climate Viticulture and Enology, Melbourne, Australia. Contact the symposium secretary at ICMS Pty. Ltd., 84 Queensbridge St., Southbank, VIC 3006 Australia, and phone 61 3 9682 0244 or fax: 61 3 9682 0288 or web site: http://www.icms.com.au/coolclimate for details.

Any information provided in this newsletter regarding procedures, products or equipment are provided solely for informational purposes and are not intended for advertisement and endorsement of any procedures, products or equipment, nor criticism of procedures, products or equipment not mentioned. The authors, The Ohio State University, Ohio State University Extension, and Ohio Agricultural Research and Development Center assume no responsibility for the implementation of procedures, products or equipment mentioned in this publication. Readers should follow manufacturers label for specified directions and recommendations.