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- Author or Editor: E. Williams x
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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.
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.
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.
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.
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.
Soil-water repellency is often a problem for turfgrass grown on sand soils. Wetting agents used to alleviate repellency often provide mixed results. We evaluated AquagroL and an experimental material (ACA 864) at 0, 7, 14, and 21ml/m2 applied monthly to tifgreen bermuda grown on a soil-water repellent Margate fine sand over 6 months. Alleviation of repellency was based upon water drop penetration time (WDPT). Wetting agents did not effect turf quality, cover, or discoloration. Wetting agents did not reduce repellency 1 month after initial application. At 2 months, ACA 864 at 21ml/m2 significantly reduced WDPT. With repeat applications, lower rates of ACA 864 provided reductions in WDPT similar to the highest rate of ACA 864, suggesting an additive effect over time. There was a decline in WDPT for all wetting agent treatments, except the control, over time. Repellency decreased with soil depth, and repeat wetting agent application reduced WDPT at lesser depth.
Abstract
Cytokinins applied to axillary buds of apple shoots overcame apical dominance. Axillary buds on actively growing apple shoots produced spurs and lateral branches when treated with cytokinins. Buds on shoots that had not received sufficient chilling to break rest were also induced to grow with cytokinins.
Abstract
The chemical 2,3,5-triiodobenzoic acid (TIBA 1,2) has been reported by workers in the United States (1,2,3,4,8) and other countries (6,7) to influence flower bud initiation and branch angle of apple trees. This report describes injury to fruits and pedicels of Golden Delicious and to foliage of Golden Delicious, Delicious and Winesap apple trees from the application of 25 ppm TIBA about 4 weeks after bloom in North Central Washington.
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.
Ferry-Morse Seed Company is trying to market worm castings to their customers. Murray State University was asked to compare different percentages of worm castings for use with both bedding plants/vegetables and houseplants. Recommended application rates for worm castings was not to exceed 30%. Two plants were chosen to represent the plant categories deemed important to the consumer: tomato (Lycopersicon esculentum `Rutgers') and spider plant (Chlorophytum comosum). Treatment percentages for worm castings were 0% for a control and 10%, 20%, and 30% were incorporated into a soilless media substrate. Treatment 1 consisted of worm castings/soilless media alone and Treatment 2 consisted of worm castings/soilless media with the addition of Peters Professional All-Purpose 20–20–20 fertilizer at 100 ppm nitrogen. Tomatoes were grown from seed and the spider plant propagules were harvested from greenhouse stock plants and sized into small, medium, and large depending on weight. Tomatoes were harvested at 6 weeks and spider plants at 10 weeks. All tomatoes in Treatment 1 had poor visual consumer quality. Visual quality for Treatment 2 tomatoes was best in 20% and 30%. No significant differences were found in Treatment 1 regarding shoot and root weights. Treatment 2 showed significant differences in dry and fresh weight between the control and 20% and 30%. There were visual quality differences with spider plants in Treatment 2 and also significant differences in shoot and root weights between control and all percentages of worm castings in Treatment 2. Based on plant performances, a recommendation to Ferry-Morse Seed Company was to market worm castings in conjunction with a regular fertilizer schedule for maximum plant quality.