Vineyard Nutrient Management Dr. Terry Bates (10/31/01) Adapted from: http://lenewa.netsync.net/public/Bates/NutrientRec.htm Vineyard fertility management is part of an overall vineyard management program where nutrient supply (soil availability, soil pH), nutrient demand (vine vigor, crop load), and nutrient uptake (root growth, rootstock) interact. In addition to the gaseous elements of carbon, hydrogen, and oxygen, grapevines require several essential mineral elements to grow and produce fruit (Table 1). Although the mineral elements are needed in different quantities, each one plays an essential role in completing the vine's life cycle. Most vineyard soils in New York and Pennsylvania contain sufficient amounts of most of these elements; however, they may not always be readily available. It is the grower's objective: 1. to increase the availability of naturally occurring soil nutrients and 2. to supplement deficient nutrients when needed. The intention of this paper on vineyard nutrient management is not to identify each essential element and its role in vine function. Rather, the goal is to characterize common conditions that cause low or imbalanced nutrient availability, identify petiole values that indicate a nutrient disorder, and provide recommendations for avoiding or correcting vineyard nutrient disorders. Table 1. The 13 essential mineral nutrients required by grapevines and the amounts required each season by 3-year-old Concord grapevines as determined by destructive harvesting at the Cornell Vineyard Laboratory, Fredonia, NY. Mature Concord vines would require significantly more of each element. For example, Michigan research indicates that mature Concord requires approximately 70 pounds nitrogen per acre. Element

Symbol

Nitrogen Potassium Calcium Phosphorus Magnesium Sulfur Iron Manganese Copper Zinc Molybdenum Chlorine Boron

N K Ca P Mg S Fe Mn Cu Zn Mo Cl B

Pounds/Acre used Concord 36.7 31.2 18.6 7.2 5.7 not measured 0.7 0.7 0.7 0.2 not measured not measured 0.1

by

3-year-old

Nitrogen and Organic Matter: Eastern US trials investigating nitrogen fertilizer and organic matter effects on the growth and production of American grape varieties date back to the 1890’s. Holladay in Virginia; Partridge, Kenworthy and Larson in Michigan; Holland in Ohio; Fleming in Pennsylvania; Childs in West Virginia; Upshall in Ontario; as well as Gladwin, Shaulis, and Kimbal in New York conducted similar nutrition field trials through the late 1960’s (for a review see J. Cook, 1966). Although the results from these fertilizer trials were often conflicting based on location, variety, soil characteristics, soil organic matter, or production level, some general themes emerge regarding vine nitrogen nutrition. 1) When low soil nitrogen is the limiting factor to vine growth and production by inhibiting canopy fill (sunlight interception) and chlorophyll production (photosynthetic capacity), the addition of nitrogen fertilizer improves vine growth and production. This makes common sense but the same statement is not necessarily true for other nutrients under certain soil conditions. 2) When nitrogen is not limiting, the addition of nitrogen fertilizer can be detrimental to quality fruit production. Excessive nitrogen through either organic or inorganic sources can produce vines that are overly vigorous, which leads to internal canopy shading, reduction in fruit quality, and reduced bud fruitfulness. In addition, excessive nitrogen leaching into water sources can be hazardous to the environment. 3) The major nitrogen source for vine uptake comes from the natural decomposition of organic matter in the soil and nitrogen fertilizers are supplemental to this. Additional organic matter can improve soil physical properties, increase water-holding capacity, and improve soil exchange capacity through the production of humus. In many of the early nitrogen studies, organic matter in the form of hay, grape pomace, or farm yard manure was equal to or better than inorganic nitrogen fertilizers in improving the long term grapevine nitrogen status. Table 2. Mean vine size and yield of Catawba grapes as affected by nitrogen and straw treatments from 1946-1951. Both nitrogen fertilization and addition of straw to the vineyard floor were needed to achieve greater vine size and yield in this vineyard plot. Reproduced from Shaulis (1956). Annual Treatment Actual N straw (lbs./acre) 0 32 64 32 64

pruning weight (tons/acre) (pounds/vine) 0 1.0 0 1.2 0 1.6 2.5 2.1 2.5 2.0

Yield

% soluble solids (pounds/vine) (obrix) 5.9 19.5 8.6 19.2 11.3 18.4 16.6 17.7 16.8 17.7

Determining the Need for Nitrogen Fertilization: Bloomtime petiole samples from the most recently mature leaf in Concord are directly related to vine size, percent trellis fill, and production. In 1956, Shaulis and Kimbal showed "that the nitrogen content of the leaf blade is more than twice that of the petioles; that the nitrogen percentage decreases as the season advances; that the basal leaves contain less nitrogen than younger leaves; and that a wide difference in potassium concentration does not affect the nitrogen percentage." Tissue nitrogen concentration is high during the spring and quickly decreases during the period of rapid vine and shoot growth (Figure 1). Shaulis and Kimbal showed that bloomtime petiole samples for nitrogen were more closely correlated with vine production than samples in July or August. However, the rapid decline in tissue nitrogen through the bloom period makes designating recommended tissue values problematic. Shaulis and Kimbal add, "With the knowledge that the nitrogen analysis-vine growth relationship is not precise, one is certain that, for late-June petiole samples, a nitrogen percentage less than 1.5 is almost always associated with low vine vigor; and that values over 2.0 are almost always associated with high vine vigor." Despite the relationship between bloom nitrogen samples and vine growth, bloom tissue samples are not widely used in New York, for several reasons. 1) Fall petiole samples are recommended for determining deficiency of other nutrients, especially potassium. 2) Maintenance nitrogen applications are used in many New York vineyards despite either quantitative (petiole values) or qualitative (canopy fill) analysis. 3) Observations of vine growth, leaf color, and trellis fill are arguably as accurate as bloomtime tissue samples given the rapid flux of tissue nitrogen concentration during bloom. Figure 1. The growing season pattern of petiole nitrogen concentration in Concord. Rapid vine growth during the bloom period is matched by rapid reduction in shoot tissue nitrogen concentration. Although bloom petiole samples are superior to fall petiole samples in indicating Concord nitrogen status, the rapid change during bloom makes sampling problematic.

SOIL pH AND NUTRIENT AVAILABILITY One of the objectives in vineyard nutrient management is to improve mineral nutrient availability of naturally occurring elements in the high-rainfall generallyacidic soils of the eastern US. Soil pH has a dramatic effect on the availability of several essential nutrients for grape production. Low soil pH (pH 5.0 or lower),

which is characteristic of Lake Erie regional soils and some Finger Lakes soils, affects nutrient availability and root growth. As the soil pH decreases from 5 to 3.5, aluminum solubility increases and it is the free and exchangeable aluminum ions that affect nutrient availability and root growth (Figure 2A). High free aluminum precipitates phosphorus out of the soil solution, making it unavailable to the plant, and exchangeable aluminum displaces calcium and magnesium, decreasing their availability. Aluminum toxicity can also affect root growth by inhibiting cell division in the root apical meristem. High pH soils, either natural limestone based soils or soils amended through the application of lime, present a different set of nutritional circumstances for grapevine roots. As the soil pH increases from 5 to 8, aluminum insolubility removes it from the playing field which alleviates some of the phosphorus problems and increases the availability of calcium and magnesium (Figure 3A and B). However, iron also precipitates out of the soil solution limiting its availability (Figure 2B).

Figure 2A and B. The effect of soil pH on the availability of aluminum (A) and iron (B) in Lake Erie region vineyards. As the soil pH decreases aluminum and iron availability increase, causing decreased availability of other essential nutrients and restricting root growth.

Figure 3A and B. The effect of soil pH on magnesium (A) and calcium (B) availability in Lake Erie region vineyards. The shaded area represents recommended soil concentrations for Mg and Ca. Each point represents an individual grower vineyard and may have been subject to any number of fertilizer management practices. It is important to illustrate the effect of soil pH on soil Mg, whether a naturally high lime soil or one amended with either calcitic or dolomitic limestone.

Acid Soils and Phosphorus Deficiency. In the eastern US, grapevine phosphorus deficiency is rare if not unknown in vineyards where the soil pH is above 5.0 and soil aluminum is below 150-200 ppm. In labrusca fertilizer trials in Michigan, phosphorus fertilizer improved the cover crop growth but did not necessarily improve grapevine growth. In a 1945 Concord vineyard survey in Ohio, Beattie and Forshey reported that the higher producing vineyards tended to have July petiole values above 0.14% P. Shaulis and Kimbal (1956) reported no response of Concord grapevines to phosphorus fertilizer despite fall petiole values as low as 0.08-0.14%. These observations led to the notion that phosphorus is of minor importance to labrusca production and that tissue samples are not reliable in diagnosing phosphorus deficiency. Recent research on the response of Concord to soil pH in Fredonia, N.Y. showed a reduction in root and shoot growth as the soil pH dropped below 5.0. High aluminum availability below pH 5.0 precipitated phosphorus making it unavailable to the plant and restricted root growth. The reduction in vine size as the soil pH dropped corresponded to a decrease in tissue phosphorus below 0.14% (Figure 4). However, it can also be argued that the root restriction in acid soils itself inhibits adequate uptake of water and other essential nutrients leading to a reduction in vine size well before measured phosphorus deficiency. Nutrition research in California indicates that phosphorus deficiency in grapevines may inhibit the movement of magnesium from roots to shoots

causing magnesium deficiency leaf symptoms. Therefore, grapevine phosphorus deficiency may be more prevalent than once thought and may show up as a reduction in vine size and an increase in magnesium deficiency.

Figure 4. The effect of soil pH on tissue aluminum, iron, and phosphorus in young Concord. As the soil pH drops below 5.0, tissue Al and Fe increase while tissue P and vine size decrease.

Other nutrient deficiencies and toxicities can be associated with 'acid injury' in hybrid and vinifera varieties. In addition to phosphorus deficiency, magnesium deficiency has been reported on acid soils especially where potassium fertilizer has been applied. As with aluminum and iron, other micronutrient metals such as manganese and copper can reach high levels in the soil and could potentially cause toxicity symptoms in some grape varieties. Applying Lime to Adjust Soil pH. Soil pH is very important in adjusting nutrient availability and lime is a powerful tool in adjusting soil pH. However, lime has low soil mobility which makes deep soil pH adjustment difficult in established vineyards. The best time to apply lime and adjust soil pH is before the vineyard is planted. In pre-plant application, lime can be incorporated deep into the soil in order to adjust the pH as far into the potential rooting zone as possible. After planting, deep incorporation of any soil amendment will come at the expense of cutting perennial roots. The calcium of calcitic limestone and the calcium and magnesium of dolomitic limestone have higher mobility in the soil. Applying excessive amounts of limestone to established vineyards can increase calcium and magnesium in the entire root zone while only adjusting the soil pH in the upper soil layer. This can cause further nutrient imbalances with potassium (see potassium section). Therefore, we recommend applying limestone in existing vineyards at no more than 3 tons/acre in any single year. Can a vineyard be productive without optimum soil pH? Since changing soil pH deep in the soil profile in established vineyards is difficult, grape production on soils with sub-optimum pH and nutrient availability is a reality. It is under these situations that vineyard nutrient management is more intensive. Regular soil and petiole testing, applying fertilizers other than just nitrogen, and foliar nutrient sprays can make up for less than optimum nutrient availability. Adding organic matter and controlling weed competition in the vineyard can help make up for restricted root growth, improve soil moisture, and supply micronutrients to the roots.

POTASSIUM The most common nutrient disorder found in eastern US vineyards is potassium deficiency. Consequently, much research has focused on understanding vine potassium requirements, identifying the factors that lead to deficiency, measuring deficiency symptoms, and alleviating the disorder in the vineyard. Sampling: Soil vs. Tissue, Spring vs. Fall, Leaf vs. Petiole. Soil testing is a tool for monitoring soil pH and estimating nutrient availability. For example, soil tests are valuable in calculating the lime requirement for acid soils. Since grapevine root systems can be spreading and/or relatively deep, tissue sampling is an effective tool in determining the nutrient status of the vine. Soil and tissue tests measure different aspects of vineyard nutrient status. Therefore, the most powerful information for the grower is obtained when soil and tissue samples are used in conjunction with, and not isolated from, each other. In regards to tissue sampling, bloomtime petiole samples have been shown to be superior to fall samples in determining vine nitrogen status. However, interpreting bloomtime nitrogen samples can be problematic (see nitrogen section). Potassium presents a different situation in that values from soil samples are often not correlated with values from tissue samples, and fall samples can be used to diagnose potassium deficiency, eliminating the problems of bloomtime sampling. Leaf tissue and petiole tissue have different potassium concentration patterns during the season. Furthermore, leaf position on a shoot will influence seasonal potassium concentration patterns (Figure 5). Therefore, if tissue samples are going to be consistently and accurately interpreted for the purpose of making fertilizer recommendations, a standard tissue sample is needed so that standard nutrient concentration values can be used for interpretation. For example, a standard recommended potassium concentration for veraison petioles will not be applicable for a grower that sampled leaves or petioles at bloom. In California, a standard set of values have been established for bloomtime petiole samples. In New York, the recommendation for tissue sampling is to collect petioles, 60-70 days after bloom (near veraison), on the most recently mature leaf. It appears this timing/tissue decision was based on practical issues. Tissue potassium concentrations are more stable near veraison, there is less vineyard activity and more time for tissue sampling near veraison, and petioles are an easy standard sample to collect. Today, the most important practical reason for the New York fall petiole recommendation is that there are standard nutrient values established and available for vineyard nutrient diagnosis.

Figure 5. Seasonal patterns in tissue potassium concentrations from sufficient (+K) and deficient (-K) Concord. Patterns are different depending on tissue and location on the shoot. The current standard for K is to collect petiole tissue 6070 days after bloom from the most recently mature leaf. Shaulis and Kimbal reported visual potassium deficiency if fall petiole values were 0.5% or lower. In high production Concord vineyards with a high K requirement, fall petiole values closer to 2.0% are recommended. Interpreting Potassium Deficiency. Several factors can contribute to potassium deficiency in the vineyard. Often, a single factor may reduce tissue potassium concentrations but it may take several factors in combination to cause full deficiency symptoms, which can make interpreting and alleviating potassium deficiency difficult. Magnesium Competition. There is a negative, non-linear relationship between potassium and magnesium fall-petiole concentrations (Figure 6). In general, as one goes up the other goes down, and finding a balance between the two is the key to preventing deficiency of either one. Natural soil pH and the adjustment of soil pH with limestone has a large effect on the K/Mg balance (Figure 7). At low soil pH, magnesium availability can be low (Figure 3A) and the addition of potassium fertilizer to a low pH soil can help induce magnesium deficiency. In high pH soils, either naturally high limestone soils or soils adjusted with lime, magnesium availability can be high and will compete with potassium in root uptake. It is important to note that soil pH itself has a big effect on magnesium availability and not necessarily how the soil pH was achieved (Figure 3A). The choice to adjust soil pH with dolomitic (high Mg) limestone instead of calcitic limestone has an additional, but smaller, effect on magnesium availability.

Figure 6. The relationship between tissue potassium and tissue magnesium in fall petiole samples taken from Lake Erie grower vineyards. In general, the tissue concentration of one decreases as the tissue concentration of the other increases.

In mature vineyards where limestone treatments cannot be incorporated deeply, the issue of soil pH adjustment and soil magnesium adjustment can be separate issues because of their relative mobility in the soil (as discussed in the lime section). From 1958 to 1968, a Concord nutrition study in Pennsylvania showed that dolomitic limestone treatments only changed the soil pH in the upper 3 inches of soil where the limestone was incorporated, and very little soil pH change was recorded below the 6 inch soil depth. However, dolomitic limestone increased soil magnesium to a 12 inch depth, the deepest measurement taken.

Figure 7. The effect of soil pH on shoot tissue potassium and magnesium concentrations of young (non-bearing) Concord. Magnesium availability increases with soil pH and competes with vine potassium uptake.

The increase in magnesium decreased the concentration of petiole potassium to the point of visual potassium deficiency and vine size reduction in some years. Root Restriction. In general, anything that restricts grapevine root growth decreases the uptake of potassium and increases the risk of potassium deficiency. Drought, overcropping, shallow-rooting, phylloxera, etc. restrict root growth and nutrient uptake. In many of these cases, grapevines do not respond to the addition of potassium fertilizer. Drought. In addition to restricting root growth, drought is particularly damaging because of the low mobility of potassium in dry soils. Conservative vineyard water management (irrigation, mulch, reduced weed competition) can decrease drought-induced potassium deficiency. Crop. Grape berries have a relatively high potassium requirement, especially in the post-veraison period. When the potassium supply from root uptake is

insufficient for fruit demand, potassium will remobilize from the vine to the fruit and may cause leaf potassium deficiency symptoms. In combination, the greatest potassium deficiency risk comes in a dry year in a vineyard with a large crop load, poor weed management, and after an application of dolomitic limestone. A potassium nutrition strategy that appears to be successful in high production Concord vineyards is to maintain fall petiole potassium values near 2%, a concentration well above the 0.5% deficiency mark. The idea is to increase vine potassium to the point that it can withstand a high crop load in a dry year.

MICRONUTRIENT METALS: ZINC, IRON, MANGANESE, AND COPPER Micronutrient metal availability also changes with soil pH (a redundant theme) and often follows the pattern seen in Figure 2. In general, availability is high in acid soils and low in alkaline soils. High availability at low soil pH can cause direct toxicity symptoms on the vine or cause indirect deficiency of another element. For example, high availability of zinc and iron will fix phosphorus and decrease its availability for root uptake. In contrast, low availability of these nutrients at high soil pH can cause deficiency. Zinc deficiency is common in California vineyards with sandy, high pH soils. Iron deficiency is common in Washington Concord vineyards where the soil is neutral to slightly alkaline. High soil phosphorus and waterlogging both additionally limit iron availability under these conditions and increase the potential for the disorder. In general, toxicities of these elements can be avoided through soil pH adjustment. Deficiencies can be eliminated through the use of foliar sprays, stimulating root growth, and the addition of organic matter. Iron nutrition is partially responsible for the different soil pH recommendations between vinifera and labrusca. In theory, grape varieties native to acid soils (labrusca) are not efficient in acquiring iron because of high iron availability in low soil pH. Therefore, they are more susceptible to iron deficiency as iron availability decreases at high soil pH. In contrast, varieties native to calcareous soils (vinifera) are more iron efficient and are less susceptible to iron deficiency at high soil pH. However, they are also less tolerant of acid soil conditions. Therefore, a soil pH of 5.5 is recommended for labrusca and a soil pH of 6.5 is recommended for vinifera in New York.

BORON Boron has a narrow range between deficiency and toxicity and the conditions that control boron availability are slightly different than the other nutrients. Boron availability does change with soil pH, where boron is absorbed by clay particles at higher soil pH. However, the movement of boron with water has a larger

effect on its availability. Boron is readily leached from soils under high rainfall conditions and drought sharply decreases boron mobility and availability. Boron deficiency has received recent attention in New York because of its possible relationship to fruit set disorder. Low boron reduces pollen germination and pollen tube growth, which reduces fruit set. Since foliar symptoms generally do not show up until late spring or early summer, fruit set problems may occur prior to foliar symptoms. Boron can be applied as a foliar spray or to the vineyard floor. Care must be taken to follow the recommended rates because excess rates can cause toxicity. Boron toxicity symptoms are marginal or tip chlorosis and/or necrosis (leaf burn), which illustrates the movement of boron with water in the xylem.

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Skinner, P.W. and M.A. Matthews. 1990. A novel interaction of magnesium translocation with the supply of phosphorus to roots of grapevine (Vitis vinifera L.). Plant, Cell and Environment. 13:821-826. Taiz, L. and E. Zeiger. 1991. Plant Physiology. Benjamin/Cummings Pub. Co., Inc. Redwood City, CA. Winkler, A.J., J.A. Cook, W.M. Kliewer and L.A. Lider. 1974. General Viticulture. University of California Press. Berkeley.