Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Larry E. Williams x
Clear All Modify Search

A study was conducted to determine the effects of crop removal on gas exchange parameters of `Thompson Seedless' grapevines grown in the San Joaquin Valley of California. Vines were either irrigated at full ET or not irrigated throughout the growing season. Clusters were removed subsequent to veraison, when the fruit soluble solids were ≈15° Brix. Reductions in leaf net CO2 assimilation rate (A) were measured within 1 day of fruit removal for both irrigation treatments and remained such until the end of the experiment. The greatest reduction in A due to crop removal on a diurnal basis was with the non-irrigated vines between 0800 and 1000 hr. The reduction in A subsequent to crop removal was not the result of an accumulation of either starch or sugars in leaf tissue. The greater reduction in A of non-irrigated vines after fruit removal may have been due to the lack of strong, alternate sinks as vegetative growth was minimal due to water stress during the experimental period.

Free access

A weighing lysimeter (with a soil container 2 m wide, 4 m long and 2 m deep) was installed at the University of California's Kearney Ag Center in 1987. Diurnal, daily and seasonal vine water use has been measured yearly since then. Vine water use was 350, 400 and 580 mm the first, second and third years after planting. respectively. Vine water use (from budbreak to October 31) the subsequent four years averaged 815 mm per year. Reference crop ET (ETo) averaged 1172 mm (from budbreak to October 31) over the course of the study. Diurnal vine water use was highly correlated with the diurnal course of solar radiation. Maximum ET averaged 50 L vine-1 day-1 during the middle part of the growing season. Experimental vines surrounding the lysimeter were irrigated at various fractions (from 0 to 140% in increments of 20%) of vine water was measured with the weighing lysimeter. Maximum yields were obtained with the 80% irrigation treatment This study demonstrated the deleterious effects of both over and under irrigation on yield of grapevines.

Free access

Entire Thompson Seedless grapevines (to include the root system) were harvested at regular intervals over a two year period. Dry matter, soluble carbohydrates, N and K were quantified on an individual organ basis for each date. The pattern of dry matter partitioning to the roots and trunk were similar from one year to the next. Decreases in dry weight in the roots and trunk were accompained by decreases in soluble carbohydrates. The concentration of K in the roots remained almost constant over the two year period while that of N fluctuated from less than 1% (dry wt basis) to more than 2.5% depending on the time of the year. The dynamics of N and K within the trunk on a concentration or content (g vine-1) basis were similar to one another. N and K were remobilized from the trunk early in the growing while only N was remobilized from the root system. Remobilization of N from the roots took place from berry set until harvest.

Free access

Abstract

Data were collected over 3 years to provide detailed information on growth and development of ‘Thompson Seedless’ grapevines used for raisin production. Leaf area and leaf, shoot, and cluster dry weights were measured throughout the growing season. Results were plotted against growing degree days (GDDs), using a minimum temperature threshold of 10°C, after budbreak. There was a linear increase in leaf area and vegetative dry matter from about 200 to 1000 GDDs after budbreak. Cluster dry weight increased linearly from 750 GDDs after budbreak until harvest. While shoot numbers per vine increased 70% from 1983 to 1985, there was not a similiar increase in the amount of dry matter per vine. Weight per unit leaf area (WL) increased from ≈ 40 g·m-2 early in the season to >65 g·m-2 90 days after fruit harvest. Results indicate that vines in this vineyard maintained a constant growth pattern year after year when growth was plotted vs. growing degree days.

Open Access

Abstract

Nitrogen content and concentration were determined on field-grown ‘Thompson Seedless’ grapevines in the San Joaquin Valley of California. Individual vine replicates were harvested throughout the growing season over a 3-year period. There was a linear increase in vine N content from budbreak to 1000 growing degree days (GDDs) later. During this time, the accumulation of N was primarily in the stems and leaves. Subsequent to 1000 GDDs, the increase in vine N was due to the accumulation of N in the clusters. Throughout the season, N concentration in all vine parts decreased. The increase in cluster N content did not appear to occur at the expense of N remobilization from the vegetative structures measured in this study. On a single date, the N concentration of leaves varied throughout the canopy—the outer layer of leaves contained 3.2% N, while leaves in the interior of vine contained 2.4% N. The loss of N from the vine through leaf fall and cane pruning was about 20 and 15 g, respectively. The data were similiar from year to year with regards to both N concentration and content in leaves, stems, and clusters when plotted vs. GDDs. The approximate requirement of N for current season’s growth of ‘Thompson Seedless’ grapevines used for raisin production was 75 g/vine, or 84 kg·ha-1.

Open Access

An ongoing study measuring grapevine (Vitis vinifera L., cv. Thompson Seedless) water use with a weighing lysimeter is being used to develop a model to simulate vine water use on both a diurnal and seasonal basis. A method to calculate the aerodynamic resistance (ra) of the vines was first determined. Subsequently, a model to predict canopy resistance (rc based solely upon intercepted photon flux density (PFD) was developed. The modeled values of ra and rcwere substituted into a resistance-energy balance equation to predict vine ET. The modeled parameters were validated against diurnal measurements of ET from the lysimeter. The greatest difference between modeled and measured rc occurred prior to 1000 h and subsequent to 1500 h each day. The model overestimated vine ET by 14 and 23% on 16 and 24 June, 1992, respectively. Ambient temperature and vapor pressure deficit were greater on 24 June than on 16 June. Refinements in calculating PFD interception by the vine's canopy early and late in the day and incorporating the effects of other environmental factors on grape stomatal conductance should improve the predictive capabilities of the model.

Free access

Leaf area development and canopy structure are important characteristics affecting yield and fruit quality of grapevines. Trellising systems and wide row spacing are common viticultural practices that violate key assumptions of currently available indirect methods of leaf area determination. We have developed a protocol for using a commercially available instrument to determine leaf area index (LAI) indirectly in a trellised vineyard. From knowledge of plant spacing, leaf area per vine can be calculated as required. A derived calibration equation resulted in a near 1:1 relationship (y = 0.00 + 1.00 X; r2 = 0.998) between actual and indirectly determined LAI over a range of LAI induced by irrigation treatments. The protocol involved covering 75% of the sensor with a manufacturer-supplied field of view delimiter and masking data from the outer three (of five) concentric radiation sensors. The protocol could form the basis for a general measurement technique, but may require local calibration.

Free access

A study was conducted to determine the effects of various cultural practices on enhancing earlier and more uniform budbreak of Perlette grapevines grown in the Coachella Valley of California. Post-harvest irrigation treatments were imposed approximately July 1 for three consecutive years. This included cut-off dates (Sept 15 and Nov 15) and various irrigation amounts based upon a standard treatment in which continued vegetative growth was inhibited. The application of hydrogen cyanamide or lack of also was included in the experimental design. In 1989 and 1990, the early irrigation cutoff date resulted in earlier dates of budbreak compared to the late cutoff. Vines irrigated with the most water had delayed budbreak compared with those irrigated with less. There were significant (p < 0.05) interactions between irrigation amounts and cyanamide applications. The results indicate that the amount and timing of post-harvest irrigations in conjunction with cyanamide will promote earlier and more uniform budbreak of vines grown in the desert.

Free access

A study was conducted to determine the effects of various cultural practices on enhancing earlier and more uniform budbreak of Perlette grapevines grown in the Coachella Valley of California. Post-harvest irrigation treatments were imposed approximately July 1 for three consecutive years. This included cut-off dates (Sept 15 and Nov 15) and various irrigation amounts based upon a standard treatment in which continued vegetative growth was inhibited. The application of hydrogen cyanamide or lack of also was included in the experimental design. In 1989 and 1990, the early irrigation cutoff date resulted in earlier dates of budbreak compared to the late cutoff. Vines irrigated with the most water had delayed budbreak compared with those irrigated with less. There were significant (p < 0.05) interactions between irrigation amounts and cyanamide applications. The results indicate that the amount and timing of post-harvest irrigations in conjunction with cyanamide will promote earlier and more uniform budbreak of vines grown in the desert.

Free access

Uniform nursery stock of five almond cultivars (Prunus dulcis Mill., cv Nonpareil, Mission, Carmel, Butte, and Sonora) propagated on peach (P. domestica L. Batsch.) rootstock were planted in open-top fumigation chambers on 19 April 1989 at the University of California's Kearney Ag Center located in the San Joaquin Valley of California. The trees were exposed to three atmospheric ozone partial pressures (charcoal filtered air, ambient air, or ambient air+ozone) from 1 June to 2 November 1989. The mean 12-h (0800-2000 h) ozone partial pressure measured in the open-top chambers during the experimental period averaged 0.038, 0.060, and 0.112 μPa Pa-1 ozone in the charcoal filtered, ambient, and ambient+ ozone treatments, respectively. Leaf net CO2 assimilation and cross-sectional area growth of Nonpareil trees were reduced by increasing atmospheric ozone partial pressures, but Mission trees were unaffected. Foliage of Nonpareil almond abscised prematurely in the ambient and ambient+ozone treatments. The susceptibility of the Butte, Carmel, and Sonora almond cultivars to ozone was intermediate between the Nonpareil and Mission cultivars.

Free access