Soil testing of your site, including a nematode count, should take place well before the time you order plants. Later, plant tissue analysis is easier and more accurate.
Grapevines are not very demanding upon nutrient supply. But nutrient imbalance can cause long term problems and have an adverse impact on the economic success of the vineyard. It is a mistake to assume that your lawn, garden or field crop nutrition expertise and the products you use for these endeavors are directly transferrable to your vineyard. Granted, grapevines, grass and tomatoes need nitrogen, phosphorous and potassium, but for grapevines, depending on your soil conditions, nitrogen only or no added nutrients may be just the ticket.
The suggestions made here have been drawn from the school of hard knocks, and counter opinions are probably available by the carload. Regardless of what people tell you, however, there is no substitute for soil testing, plant tissue analysis and your own research.
First, don't put nutrients in the planting hole or around first year vines. The use of rooting aids is fine on cuttings, but nutrients can actually be detrimental to infant root systems.
Second, nitrogen "slow release" products should not be used in a vineyard. If used, these products may cause vines to take up nitrogen late in the season causing shoots to remain green too long. This condition increases the possibility of weather damage to renewal canes, spurs and buds for the following season.
Third, application of the other minerals in typical chemical fertilizer products, phosphorous and potassium, should not be arbitrary. Although used in large quantities by grapevines, these minerals should be in balance with the soil conditions and vine variety. Excess fixed potassium in soil, for example, shows up in leaf disorder which is almost identical to the symptoms of postassium deficiency (see picture in the Rogues Gallery). Some varieties may have high or low potassium levels without showing any recognizable symptoms. Only soil or plant tissue testing will tell the true story. Application of potassium to soils already containing high levels may contribute to other mineral problems such as magnesium deficiency. Excess phosphorous can result in zinc and iron deficiency which results in poor crop yield.
Finally, attempting to change soil pH with lime in an existing vineyard is probably a waste of money. Soil pH should be adjusted before a vineyard is planted. Although grapevines and lawns are very comfortable with the same pH levels (6.8-7.0), even with clear cultivation, lime will not penetrate to the root levels of mature grapevines and influence the soil surrounding the roots.
Soil testing should be conducted on potential vineyard sites and corrections should be made for grapevines. If you live in a viticultural district, that may mean that your county extension agent is the only source of advice you will need. But absent local knowledge, it may mean that you will have to do your own research and seek the advice of other experts. In no case should you spend money and act on the counsel of someone who doesn't know anything about grape growing. A book such as the following can sometimes provide you with all you need to know when used in conjunction with a soil test.
Once you have plants in the ground, we recommend switching from soil analysis to plant tissue (leaf petiole) analysis. The first one or two years you may coast on the results of your pre-vineyard soil analysis. In year three, you should probably test at bloom time. Some deficiencies, if corrected at that time, will benefit the plants immediately and, if they are bearing their first reduced crop, adjustment may be important. Our leaf petioles go to Penn State at $18.00 per variety. At that rate, unless you have a one variety vineyard, analysis every two years sounds like a good idea. A late season analysis (after veraison) is the only way you can detect potassium deficiency or excess.
See below for a few links to good on-line grapevine nutrient sites.
|Mid-Atlantic Wine Grape Grower's Guide, Chapter 9 (pdf)|
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