Grape Grower's Notebook March 9, 2000

Organic Vineyard Soil Nutrients

Plant tissue analysis (leaf petiole testing) of samples from established vineyards will tell you everything you need to know about the needs of your vines. The fees for these tests are very significant (Penn State charges $18 per variety). Soil testing should be done in conjunction with site selection, and, unless you are performing it yourself to save money, should be replaced with tissue analysis as the vineyard matures.

Mycorrhiza

Visit our new page on this subject, use the links, and obtain a good grounding (no pun) before you plant.

Fertilizing

Applying fertilizer in the first season of a new vineyard is not recommended. You don't want a lazy root system on your vines and artificially high rates of growth from excess nitrogen will lessen the chances for a vine to make it through its first winter.

Fertilizing the second year is an option, and should be practiced conservatively.

In fact, application of fertilizer throughout the life of the vineyard is a lesson in moderation. Vine mortality in abandoned vineyards is usually not caused by nutrient deficiency. Excessive fertilizer applications in well-tended vineyards frequently is a powerful contributor to the death of the plant. In certain climates with certain varieties, fertilizer as a source of nitrogen is not applied.

Where there is a need for nitrogen supplements in a vineyard, natural sources are preferred. It is a mistake to transfer lawn care practices to your vines (see Grapevine Troubleshooting/Soil Nutrient and Mineral Content on the Home Page). Urea (ammonium nitrate) as a source of nitrogen is ideal for a vineyard. About one cup per vine should be worked into the soil, or put into holes made with a dibble three of four inches around the trunk. Application on the soil surface will result in the material being broken down by the sun and the release of the nitrogen as a gas (there goes your money). Where tests indicate that nitrogen is low, two applications, one at bud swell and another at berry set are recommended.

Animal manure is just as useful in a vineyard as anywhere else. The problem arises in controlling rate of and timing of application. It can be hazardous to have vines taking up nitrogen late in the season, remaining green instead of "hardening off" into woody canes and ultimately getting zapped by cold weather. The rate of breakdown of manure is a bit too indefinite for a vineyard. Seeking advice based upon experience is a good idea, and that's no bull.

Another drawback of using field manure, is the very good possibility that you will bring a substantial red mite population into your vineyard.

Your plant tissue lab may recommend supplementation of soil trace elements such as boron and manganese. Good links to grapevine nutrition documents may be found on the links page at the end of this section.

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