Soil pH and Mineral Nutrition of Vitis vinifera Varieties
© Copyright 2000 Robert Pool
In what way do Vitis vinifera varieties differ from Native American or Hybrid grape varieties in their nutritional requirements?
There are several important differences between the way that a typical Native American variety (Vitis labrusca) and a typical European variety (V. vinifera) respond to different soils. The home range of V. labrusca is New England, an area dominated by acid soils formed from granite rocks. Most plants do not thrive in soils below pH 5.6, but V. labrusca based varieties can tolerate somewhat more acidic (< pH 5.6) soils. Conversely labrusca vines are more sensitive to high soil pH-induced leaf chlorosis (Fe deficiency) than vinifera vines. However, the chlorotic leaves have the same or even higher Fe concentration than green leaves, but the physiologically active Fe concentration is lower. This suggests that either Fe transport or its conversion into a physiologically active form in labrusca is not as efficient as in vinifera.
When we established a test planting of V. vinifera varieties in an excellent Concord (V. labrusca) soil, the vinifera did not thrive. Vinifera leaves showed various growth abnormalities and symptoms associated with mineral nutrient imbalances such as magnesium and phosphorous deficiency symptoms and those of manganese and iron toxicities.
The picture above at right shows a Vitis vinifera vine growing in an acid soil on Long Island New York and displaying the characteristics of "Sauerschaden". The yellow chlorosis is caused by low magnesium and calcium concentration. The red flecking is associated with low phosphorus and the marginal necrosis has been ascribed to toxic accumulations of iron and/or manganese. Such vines produce fruit with very high fruit potassium concentration which produce high pH unstable wines. V. labrusca, which is somewhat more tolerant of acidic soils, may not show the visual symptoms of Sauerschaden, but the tissue nutrient levels are impacted nonetheless.
A literature search revealed that these symptoms had been well described in the Moselle area where the condition was called Sauerschaden or acid sickness. Hybrid varieties behave as hybrids would be expected to behave. Some are as sensitive to high or low soil pH as are their parents. Others are intermediate in sensitivity.
The Essential Elements:
To function, grapevines need light energy and a proper supply of the following elements.
Carbon, hydrogen and oxygen are supplied from the air and water. The other elements are called mineral or fertilizer elements and must be obtained from the soil.
In spite of the difference between grape species in adaptation to different soils, healthy plants of the various species attain very similar concentrations of mineral nutrients in their tissues, and studies have shown that the leaf or petiole mineral element concentration associated with deficiency or toxicity symptoms is also very similar among species.
Remember the supply of mineral nutrients available in the soil will depend upon several factors:
As indicated above, soil pH is a critical factor in New York vineyards. The soil pH is determined by the proportion of acidic (hydrogen and aluminum) and basic (primarily magnesium and calcium) elements in the soil. Most soils in New York date from the last advance of the glaciers. Their composition is a reflection of the rocks that made up the glacial till or the outwash materials that form the sub-soils.
Except for the Adirondack region, most bedrocks of New York were laid down under deep or shallow seas. Deep seas were cold and sediments accumulated as mud or sand deposits which became shale or sandstone when compressed. Warm seas encouraged the growth of animal and plant life and resulted in reef formation. These became limestone. The Onondaga escarpment is an important feature of New York State (see gold band in figure above). It is the remains of a former reef; among other things it provides the hard capstone over which the Niagara River flows to form Niagara Falls.
The primary vineyard soils of New York had one of three origins.
1. Glacial outwash: The melting glaciers meant higher lake levels and tremendous water flows in rivers. This resulted in stranded beaches and sand bars which form the gravel soils along Lake Erie, various bands of gravel soils along the Finger Lakes and the silt/loams of Long Island.
2. Lake deposits: Finer mineral particles did not settle out along the margin of bodies of water, but were swept into the glacial lakes where they settled as deposits of finely divided material which became silts and clays.
3. Limestone: Portions of the limestone escarpment were carried south by the glacier and smeared over the northern Finger Lakes. The soils which developed from this parental material have higher pH. In general, the subsoil pH is high at the north end of the Finger Lakes and decreases in pH as one travels south. The acid gravel, sand and shale along Lake Erie and the southern Finger Lakes proved to be well fitted to Native American grapes and the New York industry developed in those regions. An increase in V. vinifera production has encouraged vineyard establishment at the northern ends of the Finger Lakes.
These associations can be clearly seen in the general soil map of New York, above. It indicates soils with limestone as greenish, those from acid shale and sandstones as pink to red. Yellows indicate the glacial outwash soils and blues show the lake deposited soils. These can be compared to the production regions, see map below.
Cations are positively charged ions. Soil pH is a measure of the concentration of hydrogen ions. This figure shows that at low soil pH Aluminum ions make up a large fraction of the cations. As soil pH approaches 4.5, exchangeable Aluminum ions per se, disappear, and above pH 6 there are few Aluminum ions potentially available.
The table below reports data from a Bordeaux study on the affects of Aluminum ions on growth of Cabernet Sauvignon (V. vinifera) grapevines. Note that only 10 ppm (mg/l) in solution reduced vine growth almost in half. The aluminum ions are not absorbed by the roots, and they do not enter the vine. Aluminum ions directly inhibit root growth. Thus aluminum toxicity cannot be detected from petiole mineral element analysis. Vine roots must be inspected.
The table below shows that the addition of lime to an acid soil raises the pH and decreases aluminum availability.
Copper becomes more available at low pH. For world viticulture, copper toxicity is most commonly associated with long term application of copper fungicides to acid soils. This is one reason that a dependence on copper fungicides to control disease is undesirable.
Other Effects of Soil pH
Mineral Element Deficiencies: Other elements become less available at low soil pH including:
1. Nitrogen: Primarily because soil bacteria, which release nitrogen from organic matter, grow poorly in low pH conditions.
2. Calcium: Critical tissue concentrations for Ca++ in healthy soils have not been established, but acid soils are, by definition, low in Ca.
3. Magnesium deficiency symptoms are common in vines growing in acid soils. The use of lime will make the natural Ca and Mg already in the soil more available for plant uptake. The carbonate in lime does 95% of the job of raising soil pH. The Ca (in calcitic lime) OR the Ca/Mg (in dolomitic lime) are just carrier ions and have a much lower relative effect as fertilizers. Mg deficiency is often related to rachis necrosis which has been observed in Long Island and Chautauqua counties.
4. Manganese deficiency has sometimes been observed on high lime soils in the Finger Lakes. French/American hybrid varieties are more sensitive.
5. Phosphorous becomes insoluble at low pH. Very few studies have shown a benefit from fertilization with P. Raising the soil pH makes P available and also can correct other mineral nutrient availability problems cited herein.
6. Potassium availability is theoretically reduced at low pH; however, vines growing in acid soils tend to have excessive K in the foliage and fruit. The high fruit K concentration results in high pH musts which produce unbalanced, unstable wines.
Note that soil pH affects the availability of many mineral elements. A pH of 6 to 7 ensures a good supply of most elements. The exceptions are Fe, Mn, Zn, Cu and Co. Most plants have developed means to solubilize these elements at moderate pH values. Native American Grapevines are an exception in that physiologically active iron is less available when soil pH is above 6. Vines growing in low pH soil can be expected to show deficiencies of Ca, Mg, P and K.
Correcting Acidic Soils
The pH and the cation exchange capacity (CEC) of the soil are used to calculate the amount of limestone needed to change the pH of a particular soil. These values are obtained from standard soil tests. Because grapevines require a balance between calcium, magnesium and potassium, the best method of amelioration is to raise the soil pH using limestone (dolomitic or calcitic) which will make the magnesium and calcium ions found in the soil more available to the plant. Because of reduced K availability, potassium may need to be added simultaneously. The fineness of the lime is also important. Finely divided limestone will exert its effect much more quickly than more coarsely ground material.
Because root growth is inhibited by low soil pH, rooting depth may be determined by the depth to which the soil pH has been altered. Research in other places suggests that deep incorporation of limestone before planting can be very beneficial. Our experience is that surface applied limestone will alter subsoil pH, but only after several years. Deep injection of limestone to existing vineyards has been proposed, but to my knowledge, has not yet been shown to be beneficial.
New York Experience with Acidic Soils
In regional tests of vinifera varieties across NY, we found an association between the soils in the area where a variety originated and a European variety's tolerance to acid soil conditions in New York. Specifically, Bordeaux varieties (gravelly, acid soils are found in Bordeaux) showed fewer nutrient imbalance symptoms than varieties which, in Europe, are grown in moderate to high lime soils (Germany, Champagne and Burgundy varieties). However, this tolerance is only relative. Tolerant vines grew better than non-tolerant, but still produced musts with excessive K and pH.
Vines growing on Elvira (an acid tolerant native variety) and 5C produced fewer symptoms, while C. 3309 and MgT 101-14 produced most symptoms. However, growth and winter survival were reduced by low soil pH regardless of rootstock. A rootstock designed to be more tolerant of acid soils, Gravesac, has been bred by the French national agricultural research station in Bordeaux (INRA station at Pont-de-la-Maye). It may soon be available commercially in the US.
Vinifera varieties are less tolerant of low pH soil than are American varieties. Vinifera vines growing in acid soil show poor growth, low winter hardiness and leaf symptoms of nutrient imbalance. They produce musts high in K and pH. Although limited tolerance to low soil pH has been established for some varieties and rootstocks, correcting the soil pH with limestone is the best long term solution. The best time to do this correction is before the vineyard is planted. In such cases, deep incorporation should be considered.
© Cornell University, Department of Horticulture.