Issue link: http://read.dmtmag.com/i/72545
VINEYARD SOIL & CELLAR er than during the day when the stomata are usually open. Therefore, foliar sprays applied at night should be more effective than those applied during the day. As well, sprays applied during the day dry out more quickly and therefore have lower rates of mobility and uptake. Coverage of the underside of the leaves is still essen- tial, as the hydrophilic pore density is higher surround- ing the stomata. FOLIAR FERTILIZER MENU Boron is a micronutrient where foliar applications are Uptake rates for foliar fertilizer are influenced by many factors, such as the time of application, mineral nutrient concentration and the age of the leaves. Foliar fertilizer uptake rates are influenced by many factors, including the mineral nutrient concentration, the valence of the ions applied, and the ambient tem- perature, as well as plant-based factors including the thickness of the cuticle wall, the age of the leaves, and the nutrient status of the vine. Younger leaves tend to absorb foliar fertilizers better, and this can be contrib- uted in part to their thinner cuticle as well as higher metabolic activity. Also, plants that are deficient in nutrients tend to uptake these nutrients at higher rates than plants that are not deficient. Since the plant's demand for macronutrients, nitro- gen, phosphorous and potassium is generally higher than the demand for micronutrients, it may make sense for macronutrients to be applied in larger quan- tities primarily through soil-applied methods, as foliar methods are less effective when large quantities are needed. Foliar application of macronutrients can be considered as a supplement to soil-applied macronutri- ents or in cases where soil application is not feasible. For the most part, it makes sense for foliar fertilization strategies to focus on micronutrients. Timing of application should coincide with the demand for the nutrient in the vine. Although vine nutrition programs should respond to the needs of the vineyard, there may be demand for nutrient applica- tions prior to receiving the results of tissue analysis. By analyzing plant tissues every year, and soil analy- sis every few years, a grower begins to understand the needs of his or her vines, and some applications can be made predictively based on these continual demands. 40 VINEYARD & WINERY MANAGEMENT JULY - AUG 2012 All Vineyard Repair Materials in stock! Your Source for All Vineyard Trellis Supplies Repair Clamps Ocloc Post • Grapestakes LARGEST MANUFACTURER of superior grapestakes nationwide! • Erosion Control Materials Your solution to broken metal & wood posts • Crossarms • Wire • Fencing • Gripples • Crimp Sleeves • Wire Vices • T-Posts • End Posts 800.423.8016 | www.JimsSupply.com WWW.VWM-ONLINE.COM often sensible, since the range between deficiency and toxicity of boron is narrow, and foliar applications are more targeted and precise than soil applications. Since boron deficiency prevents the normal development of pollen tubes and reduces fruit set, foliar sprays of boron have been shown to increase fruit set. Boron deficien- cy can also affect leaf photosynthetic area, since it has regulatory roles in carbohydrate synthesis and trans- port, and cell division. The peak demand for boron is throughout bloom, although vines with significant boron deficiencies may experience stunted growth and would benefit from a foliar application earlier in the season. Molybdenum is also implicated in improving set, especially in varieties prone to shatter such as malbec and merlot. Molybdenum is associated with pollen tube growth, ovule penetration and fertilization of the grape flower. Plant requirements for molyb- denum are very low, so foliar applications are appropriate to supply this micronutrient. Application immediately prior to and in the early stages of bloom have improved set and increased yield. Foliar applications of zinc can not only improve set, but also vascular structure, leaf area and photosyn- thetic capacity, especially in zinc-deficient vineyards.