The SCM Winegrowers Association kicked off the 2017 Winegrower Meeting Series with special guest and Australian agronomist Mark Bingham of SJB AG-Nutri. Mark led an entertaining as well as in depth discussion on nutrient demands of premium wine grapes in California and specifically the Santa Cruz Mountains ecosystem. The focus was on early season nutrient and micronutrient requirements and deficiencies common to our area. The early season demands of the vine are crucial to meet and understand in order to best support a healthy, optimal fruit set on your premium vines.
Mark started out with an in depth look at zinc and boron. Timing is everything with these two micronutrients. Initial applications of plant available zinc should start when shoots are 4-6” out. Many people apply this common foliar too late. Depending on the formulation of the product quantities of zinc are hard to overdo. Growers should focus on getting the product on newly formed flower buds. Later season applications can support vine immunity but will have far less influence on fruit formation and set in the current season.
Boron is another essential micronutrient for best fruit set and healthy seed formation. This mineral can be very mobile in the soil. Regular seasonal soil applications aided by plentiful rain can greatly aid uptake and mobilization of this crucial element. Most soils in the Santa Cruz Mountains are deficient in Boron and will benefit from a regular soil amendment program that includes it. In addition regular applications of small amounts of foliar Boron will enhance cluster formation and set in the current season. It is very important to be aware of Boron levels in the vineyard before starting a serious amendment program as Boron is one of the few nutrients that can be toxic and cause growth deformity at high dose. Small amounts of Boron included in a sound early season micronutrient foliar program is almost always beneficial to set. Refer to prior season petiole test records to be sure of your vineyard’s Boron status before starting a serious supplement program.
An essential factor to understand when dealing with vine nutrition is that individual nutrients almost never act alone in their effect on vine growth, fruit set and maturation. For example Calcium and Boron are tied together. Calcium levels rise in plant tissue when the right ratio of Boron is present. Calcium is an essential element related to plant immunity and resistance to fungal disease pressure. Calcium supports the integrity of the cell walls in the leaves. Thicker cells provide better fungal disease resistance as the hyphae of the fungal spores have greater difficulty penetrating deeper cell tissue. Calcium is not particularly mobile in the vine. It preferentially goes to newly formed leaves and is slow to move throughout the plant. Frequent foliar applications can be very beneficial to supporting disease resistance.
Vines that are waterlogged often cannot access Nitrogen and Zinc. The formation and proper maturation of anthocyanins can be linked to adequate micronutrient status in the vines. Sunlight plays another key role here. Excessive levels of Nitrogen can lead to not only too much vigor but can also detract from color in more ways than excessive shading alone. Fruit set is enhanced by proper timing and application of Zinc and Boron and by adequate levels of Calcium and Molybdenum as well. Copper, Iron and Magnesium all play a part in vine immunity as well as support general balanced growth and fruit maturity. Vines under less stress at set are more adaptable to environmental pressure.
Potassium plays a role in reducing Magnesium levels. This information can be useful in cases of either excessive or deficient soils and amendment needs. Magnesium is very mobile and drives the vine sometimes at the expense of proper uptake of other essential minerals.
2017 is starting off as a relatively cool and wet year. Additional feeding of foliar NPK in trace amounts may be advised to provide adequate early season support if roots are in cold or excessively wet soils or getting off to a slow start. Sodium Molybdate as a soil supplement may be appropriate for vineyard soils with a history of shatter in wet springs.
There was an excellent discussion of the various chemical formulations of nutrient products available in the market. Very generally oxides and sulfates are designed for soil or fertigation applications. Chelates are intended for foliar use though can be effective in protecting nutrients that are soil and water applied. LIgnosulfonates are a chelated material that provide excellent protection and binding properties for nutrients thus enhancing uptake and absorption.
One should not rely completely on the foliar program. When it comes to nutrient uptake, soils do 90% of the work and the leaves do 10% of the work. Foliars provide a short term fix and are best combined with a long term soil amendment program that focuses on biodiversity and soil health. Products bound with lignans double as excellent adjuvants as they have excellent binding properties.
These are just a few of the many aspects of vine nutrition and especially early season uptake discussed during our meeting. Growers were treated to an intimate informational session. Attendees eagerly participated in a free exchange of give and take questions specific to their vineyards and winemaking experiences.
In addition all enjoyed an informal sharing and tasting of samples from the 2013 and 2015 vintages. These were deliberately chosen as a point of discussion and comparison from two radically different growing seasons.
Thank you to everyone who attended. We look forward to seeing you at the next meeting. Happy fruit set!
SCMWA Board Member at Large and Grower Coordinator