Vine Nutrition

Question 1

Definition of a nutrient

Answer 1

A mineral, which is absorbed by the plant either through the roots (most common) or the leaves. For a vine to absorb a nutrient it has to be dissolved in water.

Question 2

Primary and secondary (macro and micro) nutrients

Answer 2

Primary macronutrients: NPK (nitrogen, phosphorous, potassium), sulfur, calcium, magnesium

Secondary micronutrients: boron, zinc, iron, manganese, chlorine

Note: carbon, hydrogen, and oxygen are also macronutrients but because they are derived from air and water they are not typically discussed in terms of viticultural applications.

Question 3

Nitrogen

Answer 3

Importance: an essential component of cell material including cell walls and DNA

Deficiency:
….Visual signs of deficiency: chlorosis (yellowing of the canopy) of all leaves and low vigor (shorter and fewer shoots) even when water is abundant.
- if there isn’t enough, the vine won’t grow because it can’t produce more tissue
- Not enough canopy development to support the ripening of fruit (sugars are produced in the leaves via photosynthesis)
- Decrease of chlorophyll production results in chlorosis which decreases sugar production

Excess:
…Visual signs of excess: high vigor (tall shoots, lots of laterals) and dark green canopies. Fruit quality mostly considered to be lower.
- if there is too much the vine prioritizes vegetative growth instead of sexual (fruit) growth, results in overly vigorous vines, decreased fruit quality (lower sugar, too much acid, lower phenolics in reds), delayed maturation of fruit
- too much N causes a bypass of the anthocyanin production pathway (lower color development)

Note: Both excess and deficiency are common. Excess is considered the bigger issue for growers who prioritize wine quality.

Note: also plays an important role in fermentation dynamics and yeast health. Must is checked for YAN and typically adjusted with Fermaid and DAP.

Question 4

Phosphorous

Answer 4

Importance:

• Phosphorous is important for energy storage and transport (through ATP) and photosynthesis.
• It’s an important component of DNA and RNA.

Deficiency:
….Visual signs of deficiency: It causes a spotted discoloration near the leaf margin that looks similar to redblotch in red grapes (it looks sort of tie-dyed).
- Reduces yields by decreasing fruit set and # of clusters per vine.

Note: Deficiency is relatively rare (older text say this is never observed) but observed on very acidic or very basic soils. Under these conditions, phosphorous forms insoluble complexes which are trapped in the soil and the vine can’t take it up. I’ve seen deficiency on volcanic soils on Howell Mountain in Napa Valley. Phosphorous is a huge pain on organic vineyards as it isn’t very water soluble, so once the vineyard is established, you must fertilize each vine individually (dig a hole at the base of every vine and add bonemeal).

Excess: Not really a problem except that it may induce other nutritional deficiencies.

Question 5

Potassium

Answer 5

Importance: Potassium is abundant in grapes and every year at harvest large amounts leave the vineyard system. Thus, large amounts must be added back.

Functions:

• Potassium maintains cell structure by increasing cells’ osmotic pressure.
• It’s involved with stomatal function and helps the vine regulate water use.
• It is involved with ripening dynamics including sugar transport into the grapes as well as deacidification after veraison. K+ exchanges with H+ in the berries, and H+ is transported out of the berry, lowering the pH of the fruit.

Deficiency:
….Visual signs of deficiency: Causes leaf yellowing or reddening (for white and red, respectively) and the leaves may look burned or “cupped”.
- Results in higher acidity in the fruit and can cause low yields and uneven ripening.

Excess:

• Results in lower acidity in the fruit.
• Can induce other nutritional deficiencies.

Question 6

pH and nutrients

Answer 6

pH impacts nutrient availability in the soil.

Too low, defined as below 6.4
- Lower bioavailability of phosphorus, magnesium, calcium (they complex with other molecules and can’t be utilized)

Too high, defined as above 8
- Lower bioavailability of iron, manganese, boron, copper, and zinc

Native American vines and hybrids more pH tolerant
- range: ** - **

Question 7

Testing for nutrition

Answer 7

• infrared:
• aerial photography:
• neutron probes:
• soil testing
• petiole sampling

Question 8

Magnesium

Answer 8

Importance: Mg is a key component of chlorophyll

Deficiency:

• in conjunction with N, deficiency can result in low vigor and the inability to ripen fruit due to low sugar production in leaves
• Similar effect to N, delayed ripening of fruit

Excess:
- serpentine soils, as in the Mayacamas mountains

Question 9

pH and nutrients

Answer 9

pH impacts nutrient availability in the soil.

Too low, defined as below 6.4
- Lower bioavailability of phosphorus, magnesium, calcium (they complex with other molecules and can’t be utilized)

Too high, defined as above 8
- Lower bioavailability of iron, manganese, boron, copper, and zinc

Native American vines and hybrids more pH tolerant
- range: ** - **

The pH of agricultural soils decreases naturally over time due to several practices including tillage, fertilization with ammonium nitrate, and removal of cations from the vineyard through pruning and harvest. Low pH induces other nutrient deficiencies as well as aluminum toxicity and can be corrected through liming (the addition of calcium hydroxide, calcium oxide, or dolomite).

Question 10

Examples

Answer 10

NAPA VALLEY:
- The first thing Kelly Maher does when checking out a new site is dig a soil pit and check soil pH. At Dunn the soils are 4.2 which is LOW (common with volcanic or rhyolitic soils). Phosphorous unavailable below pH 4.8