Optimal Viticultural Systems Comparison

The 1995 season represents the initial year of data collection for this project. Viticulture production system treatments continue to be established. Treatments included in the study are conventional, biologically intensive, and organic production systems. Production systems are being evaluated for effects on soil microbiology, viticultural and enological performance, populations of destructive and beneficial arthropods, and economic performance. Experimental protocols for sampling and analysis of soil microbiology in the study were developed during 1995. Soil samples collected in August and in October 1995 were analyzed for physical properties (water content, dry mass, and water holding capacity) as well as for chemical parameters (pH and total nitrogen). In the realm of microbiology, samples were analyzed for soil dehydrogenase activity, actinomycete enumeration, and microbial biomass. In addition, soil samples from all treatment plots were analyzed for plant parasitic nematodes. Soil microbiological analysis suggested high activity in the conventional treatment, intermediate activity in the conventional treatment, and low activity in the biologically intensive plots. It should be noted that this data is the result of the first season of data collection and is only preliminary. Plant parasitic nematode populations were quite low and did not appear to be influenced by production system. Nutritional status of vines was adequate and was not influenced by production system. Initial yield, fruit composition, wine quality and dormant pruning weight data will be collected during the 1997 season. Population patterns of important arthropods were monitored at approximately two week intervals from June through October. Population densities were low due to the fairly sparse canopy in the young vineyard. However, the following beneficial insect predators were detected; lady beetles (Coleoptera: Coccinellidae), green lacewings (Neuroptera: Chrysopidae), minute pirate bugs (Hemiptera. Anthocoridae), rove beetles (Coleoptera: Staphylinidae), and hover flies (Diptera: Syrphidae). These data are preliminary and continued development of the vineyard will enhance our ability to detect treatment differences.

Response of Chardonnay Grapevines to Windbreaks in the Salinas Valley

A five year (1991-1995) study examined the effects of windbreaks on the vegetative and reproductive growth of Chardonnay grapevines grown in the Salinas Valley of California. Vines enclosed in open-top chambers constructed of 50%density shade cloth were compared to vines grown under ambient conditions. Treatments were replicated eight times using seven vine plots. Wind speed within the shelters was reduced approximately 50%compared to ambient wind, while the temperature, relative humidity, and light environment of sheltered and non-sheltered were similar. Marked differences in vine growth and productivity were observed between the treatments. Sheltered vines had significantly larger primary and lateral leaves, greater total leaf area, and increased pruning weights compared to control vines. During periods of high velocity winds, sheltered vines had lower midday leaf water potentials, and greater stomatal conductances and net C02 assimilation rates, than control vines. Over the five year period, wind shelters increased vine yield 15%compared to the control. Yield improvements were due to increased cluster numbers per vine, as well as greater cluster weights as a result of more berries per cluster. Despite greater crop loads, fruit from sheltered vines reached maturity on the same time or slightly ahead of fruit from control vines. Treatments were harvested at similar soluble solids levels, however, fruit from sheltered vines had lower titratable acidity and higher pH compared to the control. Sensory analyses performed on wines produced in 1991 and 1992 indicated no preference between the treatments.

The Effect of Application and Timing of Cryolite on Fluoride Levels in Red and White Wines

The main purpose of this experiment was to determine the level of fluoride in red and white wines from grapes sprayed with Cryolite at specific rates and application times. A four-year study at CSU Fresno has conclusively shown that Cryolite increases fluoride levels in red and white wines. From 1990 to 1993, many different rates and timing combinations were tried in order to clarify the role of Cryolite in wine fluoride. In 1993, a 6-pound full bloom rate was the basis for an application and timing trial tested on seven different vineyards in the San Joaquin Valley. The objective here was to determine the minimum Cryolite that would be efficacious and yet produce the lowest fluoride levels in wines. The experiment was conducted at 7 different vineyards in three general areas of the San Joaquin Valley. Zinfandel, Barbera, French Colombard, and Thompson Seedless varieties were studied (Table 1). At CSU Fresno, a replicated experiment was performed on Thompson Seedless, Zinfandel, and French Colombard. The treatment schedule is listed in Table 2. In addition, a second experiment focused on the role of surfactants with Cryolite on fluoride levels (Table 3). Treatments were applied at each vineyard using grower-supplied equipment; at CSU Fresno, applications were made with a single row over-the-vine boom sprayer. Insect populations were monitored frequently by growers and researchers during the growing season. No plots received applications of other non-fluoride containing products, but all other normal cultural practices were performed. At harvest, grapes from each treatment were made into wine. The wines were bottled and analyzed for fluoride by the Ion Selective Electrode method. The results from the 1993 research show that untreated grapes (Tl) had the lowest wine fluoride levels. In most cases, grapes treated at bloom and again 15 days later (T6) had the highest fluoride levels (Table 4). These results confirm earlier research that showed that wines which received Cryolite applications had significantly increased fluoride levels. The low rates applied at bloom, pre-bloom, and shatter caused small variations in fluoride levels, but the differences between treatments are very small. A replicated experiment at CSU Fresno showed no significant differences between any treatments (Table 5). In the surfactant study, applications of Cryolite with either a spreader or a sticker-spreader had no significant affect on wine fluoride levels. Most fluoride levels were exceptionally low in 1993, leading to the conclusion that the 6-pound full bloom rate will produce wine fluoride levels below the restrictive 1 ppm limit. Insect populations were monitored but counts remained low. No conclusions concerning efficacy can be made.

Influence of Windbreaks on the Vegetative and Reproductive Growth

A study was initiated in spring of 1991 to determine the effects of windbreaks on the vegetative and reproductive growth of Chardonnay grapevines in the Salinas Valley. Grapevines grown in artificial wind shelters were compared to grapevines exposed to ambient wind conditions (control). Wind speed was reduced by up to 50%within the shelters, depending upon ambient wind velocity. Marked differences in the vegetative and reproductive growth of sheltered and non-sheltered vines were observed in both seasons. Sheltered vines had significantly larger primary and lateral leaves, and greater primary and total leaf areas per vine. The specific weight (mg dry weight ? cm leaf area) of both primary and lateral leaves was greater for the control than for sheltered vines. The number of nodes per shoot was similar for both treatments, however, the internode length of sheltered vines was significantly greater than internode length of non-sheltered vines. Total yield per vine for the windbreak treatment was 10%greater than the control in 1991, and 20%greater than the control in 1992. Yield differences were a result of increased berry number per cluster and cluster weight in the windbreak treatment. Fruit from the treatments did not differ significantly in berry weight, soluble solids content, titratable acidity, or pH at harvest in either season. Stomatal conductance and carbon assimilation rate was slightly greater for sheltered vines than for unsheltered vines. The results indicate that windbreaks augment vine capacity by increasing total leaf area and magnifying cluster weight fruit via their effects on vegetative growth and cluster weight.

Influence of Windbreaks on the Vegetative and Reproductive Growth

Spring and summer months in the Salinas Valley are characterized by strong daily winds. It is widely held that vine growth and productivity in this region are reduced due to the presence of excessive wind. Chardonnay, the major wine grape cultivar of this region, appears to be particularly sensitive to excessive winds. Salinas Valley wine grape growers have recently expressed interest in the use of windbreaks to increase vegetative and reproductive growth. The long-term effects of windbreaks on vine vegetative growth, yield components, fruit composition, and wine quality have not been adequately investigated. A study was initiated in spring of 1991 to determine the effects of windbreaks on the vegetative and reproductive growth of Chardonnay grapevines in the Salinas Valley. Grapevines grown in artificial wind shelters were compared to grapevines exposed to ambient wind (control). Wind speed was reduced by up to 50%within the shelters, depending upon sensor distance above ground. Marked differences in the vegetative and reproductive growth of sheltered and non-sheltered vines were observed in both seasons. Sheltered vines had significantly larger primary and lateral leaves, and greater primary and total leaf areas compared to the control vines. The specific weight (mg dry weight-cm’2 leaf area) of both primary and lateral leaves was greater for the control than for sheltered vines. The number of nodes per shoot was similar for both treatments, however, the internode length of sheltered vines was significantly greater than the internode length of non-sheltered vines. The rate of shoot growth was also significantly greater for sheltered vines than for non-sheltered vines. Stomatal conductance and carbon assimilation rate were slightly greater for sheltered vines than for unsheltered vines, while no difference was found in leaf water potential between the treatments. Significant differences in vine yield components were not observed between the treatments in 1991. However, in 1992 cluster number, cluster weight, and fruit yield of sheltered vines was greater than for non-sheltered vines. Fruit and must composition were similar for both treatments. The results indicate that sheltered vines produced higher yields than non-sheltered vines due to their greater vegetative growth and vine capacity. Sensory evaluations of wines produced in 1991 and 1992 will be performed in the upcoming season.