Issue link: http://read.dmtmag.com/i/72545
VINEYARD SOIL & CELLAR Zinc plays many important roles in enzymatic reactions involving plant development and hormonal regula- tion. Large applications of phospho- rous fertilizers to soil can induce zinc deficiency by decreasing the solubility of zinc in the soil. Zinc deficiency is common in weathered acidic and calcareous soils. Zinc is not very mobile in soil, so foliar applications are preferred; peak demand is from bud break through the end of shoot elongation. Magnesium is the central ele- ment in chlorophyll and is essential for chlorophyll development and photosynthesis, and therefore, chlo- rosis is the most obvious vis- ible symptom of magnesium deficiency. Magnesium is also critical in many enzymatic reac- tions. It should be supplied early in the vine-growth stage, when leaf development is at its maximum. Magnesium sprays in conjunction with zinc applica- tions can be particularly effec- tive in improving leaf area and function. Manganese and iron are nutrients where foliar applica- tions are less expensive, and as or more effective than soil applications. Manganese plays a role in many redox reactions and is an activator of many enzymatic processes associ- ated with nutrient uptake and mobility and nitrogen utiliza- tion. Its application during veg- etative and reproductive growth can improve vine health and leaf photo- synthetic function. Iron deficiency can negatively the early vegetative development of the vine can be a quick way to meet this demand and prevent further chlorosis. Calcium deficiency can lead to thinner cell walls, poor fruit integ- rity, berry splitting and susceptibility to diseases. Since calcium moves mostly through the xylem of the plant, soil-applied calcium moves from roots to leaves, and gets bound in leaves. Foliar applications of calcium to the clusters, during bloom and the early phase of berry growth characterized by cell divi- sion, can create firmer and more resilient berries. and micronutrients. Your supplier may have a blend to fit your pro- gram, particularly for enhancing set near bloom. ORGANIC OPTIONS There are many complex organic foliar nutrition products that are based on fish emulsion or seaweed extracts. They can contain micro- nutrients, and possibly macronutri- ents, and can supplement a broad nutrition program. It makes sense to use a reliable supplier and check the label for guaranteed ingredients. Silica sprays, certain formula- tions of which are used in Bio- dynamic vineyards, can help vines fight fungal diseases such as powdery mildew and improve light interception. Silicon is also associated with inducing systemic acquired resistance, and should not be relied upon for disease control, although it can supplement a disease-prevention program. Compost teas are water- Start with healthy compost when preparing com- post teas. impact the size of chloroplasts and protein content in chloroplasts. The demand for iron is particularly high during active meristematic growth and shoot elongation. Iron defi- ciency tends to be an issue in cal- careous soils, and symptoms of iron chlorosis are usually more preva- lent in spring, when shoot growth is rapid and bicarbonate concentra- tion in the soil solution buffers soil pH. Since the solubility of iron is pH-dependent, under alkaline and calcareous soils, inorganic iron avail- ability can fall below plant demand. Foliar applications in spring during WWW.VWM-ONLINE.COM Although potassium is a mac- ronutrient and deficiencies should mostly be corrected with soil appli- cations, a foliar application can quickly correct a deficiency and/ or be used to supplement a soil program. Potassium is required for protein synthesis and enzyme regulation; it also plays important functions in loading of sucrose to berries. Vines with potassium defi- ciency may experience lower rates of berry maturation as indicated by sugar accumulation. Late-season applications, post-set, of foliar potassium, such as with Agro-K's KDL, can improve sugar accumula- tion in berries. Foliar fertilizers are available in blends of micronutrients, and macro based compost extracts that, when made correctly, con- tain high levels of beneficial microbes and are reported by growers to have disease-sup- pressive abilities and improve overall plant health. It is impor- tant to start with healthy, qual- ity compost, and it likely will take time to refine your extrac- tion technique. If you choose to purchase microbial products, make note of their shelf life and storage conditions, as they become less active with age and improper storage. Minimal research has been done on foliar fertilizers in general, and even less on compost teas and other organic fertilizers. Also, there are many factors at play when gauging the response of the vines to an appli- cation, making it difficult to assess the efficacy of these products. It makes sense to know your vineyard, supplier and product manufacturer, and to set up trials in your own vine- yard if you have that capability. Comments? Please e-mail us at feedback@vwm-online.com. JULY - AUG 2012 VINEYARD & WINERY MANAGEMENT 41