fable 5. Mean taste ratings of 'Stover' and 'Suwannee' in the years with (Table 3). The edibility of the bunch grape cultivars 'Or under-ripe fruit (July 8, 10, and 11) with years with ripe fruit (July 13 to 25). F U X lando Seedless', 'Conquistador', 'Liberty', 'Stover', and 'Suwannee' were preferred, with 'Daytona' and 'Norris' in

July 8, 10, 11 13 to 25 termediate, and 'Blanc Du Bois', 'Roucaneuf, 'Blue Lake', 'MissBlue', and 'MidSouth' of inferior fresh fruit flavor Mean Mean Mean Mean and texture (Table 4). of of of of Means Modes Means Modes Literature Cited

Stover 4.38 4.0 5.25 5.4 Suwannee 4.08 4.0 5.07 4.6 1. Baldwin, J. G. 1964. The relation between weather and fruitfulness of the Sultana vine. Austr. J. Agric. Res. 15:920-928. 2. Burgess, J. 1986. Florida wine varieties: Now and in the future, p. Length of time in cold storage was also a factor where 93-97. In: M. C. Halbrooks (ed.). Proc. First Greater Grapes Symp., Univ. of Florida, Gainesville. it was measured for 'Stover' grape. Fruit of 'Stover' picked 3. Carroll, D. E. and J. E. Marcy. 1982. Chemical and physical changes fresh just before the taste panel was compared with one- during maturation of muscadine grapes (Vitis rotundifolia). Amer. J. week cold-stored fruit of the same cultivars in 1969. Fresh Enol. Vitic. 33(3): 168-172. picked fruit was rated 6.39 (mode of 8) and stored fruit 4. Guilfat-Reich, S. and B. Safran. 1971. Indices of maturity for table grapes as determined by variety. Amer. J. Enol. Vitic. 22(1): 13-18. was 4.39 (mode of 2). This may also reflect the effects of 5. Halbrooks, M. C. and J. A. Mortensen. 1989. Origin and significance riper fruit where picked fresh than where stored. of Florida hybrid bunch grapes and rootstocks. HortScience 24(in The relative sequence of cultivars in the tasting also press). influenced ratings. In 1970, 'Stover' sampled after 'Blue 6. Kliewer, W. M. 1973. Berry composition of Vitis vinifera cultivars as Lake' was rated 5.65 compared to 4.18 when tasted after influenced by photo- and nycto-temperatures during maturation. J. Amer. Soc. Hort. Sci. 98(2): 153-159. Fla. D4-176. Usually the first cultivar tasted in the taste 7. Mortensen, J. A. 1983. 'Suwannee' and 'Conquistador' grapes panel received higher ratings than the same cultivar later HortScience 18:767-769. in the same series (e.g., Fla. D5-21 bunch grape was rated 8. Mortensen, J. A. 1988. 'Blanc Du Bois' grape. HortScience 23:418- 4.2 at the first slot and 3.4 at the 13th position in the 1968 419. 9. Mortensen, J. A., L. H. Stover, and C. F. Balerdi. 1977. Sources of panel). The ranking of 'Hunt' muscadine is in doubt as it resistance to Pierce's disease in Vitis.]. Amer. Soc. Hort. Sci. 102*695- was only tasted one year and that year it was the first entry 697. sampled. 10. Sims, C. A. and M. C. Halbrooks. 1986. Quality comparison of'Or Results of the taste panels indicate good consumer ac lando Seedless' with 'Thompson Seedless' grapes. Proc. Fla. State ceptability of muscadine cultivars Try', 'Magnolia', 'Sugar- Hort. Soc. 99:193-194. 11. Steel, R. G.D. and J. H. Torrie. 1960. Principles and Procedures of gate', 'Hunt', 'Triumph', 'Welder', 'Dixie', 'Watergate', Statistics. McGraw-Hill Book Company, Inc. 'Nesbitt', 'Magoon', 'Albemarle', and 'Summit', while 12. Winkler, A. J. and W. 0. Williams. 1939. The heat required to bring excluding muscadine cultivars 'Dixiered', 'Pride', 'Noble', Tokay grapes to maturity. Proc. Amer. Soc. Hort. Sci. 37:650-652. 'Sterling', 'Thomas', 'Redgate', and 'Nevermiss'. Cultivars 13. Winkler, A. J. and W. 0. Williams. 1945. Starch and sugars of Vitis vinifera. Jour. Plant Physiol. 20:412-432. 'Higgins', 'Carlos', 'Cowart', 'Chief, 'Jumbo', and 'South 14. Winkler, A. J. 1974. General Viticulture. Univ. Calif. Press. Berkeley, land' were considered intermediate quality level by tasters CA. 7

Proc. Fla. State Hort. Soc. 101:232-235. 1988.

USE OF TENSIOMETERS FOR BLUEBERRY IRRIGATION SCHEDULING

A.G. Smajstrla, D. Z. Haman Abstract. Magnetic switchingtensiometers were used to au University of Florida, IFAS tomatically schedule drip irrigation of blueberries (Vaccinium Agricultural Engineering Dept. ashei Reade and Vaccinium corymbosum L). Irrigations were Gainesville, FL 32611 scheduled at 10, 16, and 25 kPa soil water tensions on mulched and bare soil. This research demonstrated that irriga P. M. Lyrene tion of blueberries can effectively be scheduled using anau University of Florida, IFAS tomated tensiometer-controlled irrigation system. To reduce Fruit Crops Dept. drainage losses, irrigations were scheduled to apply small, Gainesville, FL 32611 frequent pulses of water. Plant growth and water use were greatest with mulched as opposed to bare soil production sys Additional index words, drip irrigation, soil water tension, tems. Greatest growth and water use occurred when irriga water potential,irrigation controllers, automated irrigation tions were scheduled at 10 kPa soil water tensions, and when scheduling. tensiometers were placed at depths of 8 and 22 cm below the surface as opposed to 15 and 30 cm. However, the amount of drainage that occurred at the 10 kPa level may indicate Florida Agricultural Experiment Station Journal Series No. 9544. Mention of trade names is for information only and does not imply en that the optimum soil water tension falls between the 10 and dorsement of specific products or the exclusion of other similar products. 16 kPa levels studied.

232 Proc. Fla. State Hort. Soc. 101: 1988. Blueberries are becoming an increasingly popular read and inspected three times a week when other field Florida crop. An important reason for this is their profit data were collected. They were serviced only as needed, ability. Favorable climatic conditions allow the fruit to based on air accumulations in the instruments. reach markets when prices are high. From transplanting through April, 1988, tensiometers In Florida, irrigation is an important production prac were installed at depths of 15 and 30 cm in each bank. tice because blueberries are not drought tolerant (5). Typ From May through October, 1988, tensiometers were ical Florida sandy soils have very low water-holding placed shallower at 8 and 22 cm. The four tensiometers capacities, and rainfall is not always timely. Render and for each treatment were wired in parallel so that a criticaJJy Brightwell (3) reported that blueberries require one to two low soil water tension measured by any one tensiometer inches of rain or irrigation per week during the growing would initiate an irrigation. season. Ballinger (1) recommended that irrigations be Irrigation timer-controllers were used to schedule irri scheduled when 30% to 50% of the available water remains gations at a predetermined time of day and for a predeter in the root zone. Haman et al. (2) reported additional de mined duration. The timers were set to permit irrigations tails on blueberry production in Florida. at a maximum frequency of once per day, when initiated No information was found on the use of tensiometers by the tensiometers. Durations were set at 15 min, which for automatic irrigation scheduling of blueberries under applied 6 L per plant at each irrigation. Timers were set humid climate conditions typical of Florida. Therefore, the to irrigate all treatments between 3:00 and 4:30 pm, im objectives of this research were to develop and evaluate an mediately following the peak water use times of day. automated tensiometer-based drip irrigation scheduling system for growth of young blueberries in Florida, and to Results and Discussion determine the effects of tensiometer placement and water tension settings on the operation of the automated irriga The automatic tensiometer-controlled irrigation system tion system. worked well throughout the 15 month data collection period. There were no equipment failures that resulted in loss of data or improper scheduling of irrigations. On two Materials and Methods occasions, three tensiometers per treatment functioned This study was conducted in a field lysimeter system at normally while the fourth failed to function because it was the IFAS Irrigation Research and Education Park in not properly sealed after it was serviced. Because the ten Gainesville, FL. Two-year-old container-grown Sharpblue siometers were wired in parallel, the irrigation control sys (highbush), and Beckyblue and Climax (rabbi teye) tem continued to function properly even though some of blueberry plants were used in this work. Two blueberry the tensiometers were disabled. This wiring arrangement plants were grown in each of 24 lysimeters, a total of 48 is recommended rather than wiring in series because paral plants. The lysimeter system was equipped with rain shel lel wiring permits the irrigation system to continue to oper ters that automatically covered the crop during rainfall. ate unless all of the tensiometers are disabled. Also, the use Thus all water that the crop received was applied through of several tensiometers for each irrigated zone (four total, the irrigation system. Details of the lysimeter construction two at each depth, in this research) is recommended for and characteristics were given by Smajstrla (6). crops such as blueberries which are very sensitive to water Blueberries were grown following typical Florida pro stress. This arrangement compensates for variability be duction practices (4). Treatments consisted of irrigation at tween sensor locations in the root zone by scheduling irri soil water tensions of 10, 16, and 25 kPa for pine bark gations based on the driest part of the root zone. mulched and bare soil ground covers (M10, Ml6, M25, The use of the deionized water - sodium hypochlorite and BIO, B16, B25, respectively). Details of production tensiometer solution effectively prevented organic growths management and data collection for this research project in the tensiometers. The plexiglass tensiometer tubes re were reported by Haman et al. (2). mained clear and easy to inspect for air bubbles. The com Plants were transplanted on 15 April 1987. The exist mon problems of bacterial growth and depostion of slime ing sprinkler irrigation system was used for plant establish on the ceramic cups were also avoided by the use of this ment until drip irrigation treatments were initiated on 15 solution. As a result, tensiometers responded rapidly July 1987. Data reported here were collected through 31 throughout the treatment period. They did not experience September 1988. a reduction in response time after being in the field for A point-source drip irrigation system was used. Three several months as often occurs when tensiometers are used 8-liter per hour (Lph) drip emitters were installed on each with untreated water under Florida climatic conditions. plant. Emitters were placed at the base and at 30 cm on Irrigation volumes applied were predetermined by al each side of the plant. In this arrangement, the emitter lowing the controllers to operate for only 15 minutes per wetting patterns overlapped at each irrigation. irrigation. With three emitters per plant, this applied 6 L Magnetic switching tensiometers were used to schedule per plant at each irrigation. This application was repeated irrigations at soil water tensions of 10, 16, and 25 kPa. Two each day if the soil was sufficiently dry. These small vol banks of tensiometers were installed for each soil water umes and high frequencies were necessary because of the tension treatment, and two tensiometers were installed in shallow root zone of blueberries in this production system. each bank. Tensiometers were positioned 15 to 20 cm from Fig. 1 shows the total irrigation volumes applied and the plants, well within the wetting patterns of the drip drainage volumes from the lysimeters during the 15 emitters. months of this study. Largest irrigation volumes were The fluid used in the tensiometers was deionized water applied at the 10 kPa (M10 and B10) water tension treat treated with 10 ml of 5.25% liquid sodium hypochlorite ments, and volumes decreased with increasing tensions. per liter to prevent organic growths. Tensiometers were Also, larger volumes were applied for the mulched (M10,

Proc. Fla. State Hort. Soc. 101: 1988. 233 IRRIGATION AND DRAINAGE ers were located at depths of 15 and 30 cm. Drainage data JUL. 1987 - APR. 19 are only shown for August, 1987 through April, 1988 be cause all treatments had large drainage volumes in July resulting from the frequent sprinkler irrigations used for establishment of the plants. Fig. 3 shows data for the sec ond time period of May, 1988 through September, 1988 when tensiometers were located at 8 and 22 cm depths. Fig. 2 shows that drainage ranged from 13% to 28% of the irrigation volumes applied, depending on the soil water tension and ground cover treatments. The 25 kPa treat ment drainage losses were smallest because of the small volumes of irrigation applied at this water tension and the limited downward movement of water because of the rela tively dry soil. The mulched 10 kPa treatment lost only 21% of the irrigation water to drainage, despite the application of more than twice as much water as any of the other treat M10 M16 M25 B1O ments. This occurred because of the rapid and vigorous TREATMENT V7\ IRRIGATION growth of these plants, which made them very effective in intercepting and using the relatively large amounts of Fig. 1. Irrigation and drainage volume totals and the percentage of water applied. irrigation lost to drainage for the 15 month project duration. The largest percentage drainage losses ranged from 27% to 28% of the irrigation applications for the M16, M16, and M25) as compared to the bare soil (BIO, B16, BIO, and B16 treatments. These losses occurred because and B25) treatments. Plant growth patterns closely fol these plants did not grow as rapidly as the M10 plants, lowed these irrigation patterns (2). thus they were less effective in extracting the water The volumes of water that drained to the bottoms of applied. the lysimeters (1.8 m depth) were extracted and measured. Fig. 3 demonstrates that the percent of irrigation water These volumes and the percentage of irrigation water lost lost to drainage was affected by the depth of tensiometer to drainage are shown in Fig. 1. Even with the small (6 L) placement. The mulched treatment irrigation amounts in volumes applied at each irrigation, some drainage oc creased as a result of placing the tensiometers shallower. curred for all irrigation treatments. In general, the larger This was caused by more frequent irrigations in response drainage amounts occurred in the wetter (10 and 16 kPa to more rapid soil drying as a result of root activity in this soil water tension) treatments. This occurred because the zone. wetter soils permitted greater downward water movement Despite the increased irrigation that resulted from shal due to gravity. lower placement of the tensiometers, the percentage of Fig. 2 and 3 show irrigation and drainage volumes and water lost to drainage was decreased to 8% for the Ml6 the percentage of irrigation lost to drainage for the time treatment and to only 3% for the M25 treatment. This was periods corresponding to the two sets of tensiometer attributed to the fact that plant root development in depths studied. The first time period (Fig. 2) was July, creased with increased growth, and the increased root 1987 through April, 1988. During this time the tensiomet- growth enabled these plants to more effectively extract the

IRRIGATION AND DRAINAGE IRRIGATION AND DRAINAGE

TOTALS: JUL. 1987 - SEP. 1 MAY. 1988 - SEP. 1988

600 - % /A / / 500 - i yA //, % /A 200 - A 27% 'A / / A

z . 100 - //, i I // VAX A A / y 8% / / ^ 20% \/An* vrzx 20% 0 - A =s=n 1 M10 M16 M25 B10

TREATMENT |W| DRAINAGE Vr7\ IRRIGATION |\\| DRAINAGE

Fig. 2. Irrigation and drainage volumes measured and the percentage Fig. 3. Irrigation and drainage volumes measured and the percentage of irrigation lost to drainage with tensiometers at 15 and 30 cm depths. of irrigation lost to drainage with tensiometers at 8 and 22 cm depths.

234 Proc. Fla. State Hort. Soc. 101: 1988. small amounts applied at each irrigation. However, these occurred because the reduced plant sizes also reduced the treatments suffered growth reduction as compared to effectiveness of the plant root systems in extracting soil those in M10 as a result of water stress (2). water. The M10 treatment plants apparently did not suffer water stress. The drainage percentage increased from 21% Literature Cited to 27% as a result of shallower placement of the tensiomet- ers. These results suggest that this treatment was over-irri 1. Ballinger, W. E. 1966. Soil management, nutrition, and fertilizer prac gated, and that the over-irrigation was increased by shal tices in blueberry culture. In: Eck, P. and N. F. Childers. Blueberry culture. Rutgers Univ. Press. New Jersey. lower tensiometer placement. Future research should be 2. Haman, D. Z., A. G. Smajstrla, and P. M. Lyrene. 1988. Effects of directed toward studies of irrigation response in the 10 to irrigation and ground cover on growth of blueberries. Proc. Fla. State 16 kPa range and toward studies of the effects of smaller Hort. Soc. 101:this volume. applications per irrigation as means of reducing drainage 3. Render, W. J. and W. T. Brightwell. 1966. Environmental relation ships in blueberry culture. In: Eck, P. and N. F. Childers. Blueberry losses. culture. Rutgers Univ. Press. New Jersey. Fig. 3 also shows that approximately 20% of the irriga 4. Lyrene, P. M. and T. E. Crocker. 1984. Florida blueberry handbook. tion water applied was lost to drainage for all three bare Ext. Cir. 564. IFAS, Univ. Fla., Gainesville, FL. soil treatments. This drainage occurred despite the fact 5. Scott, D. H., A. D. Draper, and G. M. Darrow. 1978. Commercial that the irrigation amounts applied were small with respect blueberry growing. Farmer's Bui. 2254. USDA-SEA, Washington, D. C. to those of the mulched treatments. However, plant 6. Smajstrla, A. G. 1985. A field lysimeter system for crop water use and growth was much reduced as compared to that of the water stress studies in humid regions. Soil and Crop Sci. Soc. Fla. Proc. mulched treatments (2), and apparently the drainage losses 44:53-59.

Proc. Fla. State Hort. Soc. 101:235-238. 1988.

BLUEBERRY RESPONSE TO IRRIGATION AND GROUND COVER

D. Z. Haman University of Florida, IFAS Dept. of Agricultural Engineering increases quantity and improves quality of fruit. Newly Gainesville, FL 32611 planted or container grown blueberries are drought-sensi tive, and irrigation is essential for successful establishment A. G. Smajstrla and subsequent growth of young blueberry plants 4, 11). University of Florida, IFAS Blueberries are not drought tolerant (9) and irrigated Dept. of Agricultural Engineering plants have higher survival rate, greater vigor, greater Gainesville, FL 32611 plant height and more fruit per plant than non-irrigated plants (11). During productive years adequate water sup P. M. Lyrene ply increases total yield and individual berry weight (1). It University of Florida, IFAS has been found that an increase in the number of flowers Dept. of Fruit Crops per stem (3, 12) is correlated with the avoidance of water Gainesville, FL 32611 stress during bud formation. Render and Brightwell (6) reported that blueberries require 1 to 2 inches of rain or Additional index words. Micro-irrigation, mulch, tensio- irrigation per week. Ballinger (2) recommended that an meters, irrigation scheduling. irrigation should be applied when 30% to 50% of the avail able water remains in the root zone. At the same time, Abstract. Results of a study of blueberry growth during the blueberries are sensitive to excess water and require good first year after transplanting are presented. Two-year-old con drainage (5). tainer-grown Sharpblue ( Vaccinium Corymbosum L), Becky- Two types of blueberries are grown in Florida: high- blue and Climax ( Vaccinium ashei Reade) blueberry plants bush and rabbiteye. Highbush blueberries are less vigor were grown in a field lysimeter system at Gainesville. Treat ous, lower in yield, and more prone to frost damage, but ments consisted of irrigation at —10, —16, or —25 kPa soil they ripen 3 to 4 weeks before the earliest-ripening rab- water potentials and pine bark mulch versus no-mulch ground biteyes planted at the same location. Due to this early ri cover. pening, their production is potentially very profitable in The greatest growth occurred on the —10 kPa mulched Florida (7). The rabbiteye blueberry is native to northeast treatment for all varieties of blueberry. Mulched plants under Florida and is considered to be the world's highest-yielding all treatments performed significantly better than unmulched and most vigorous cultivated blueberry species (7, 8). How plants. Growth of Beckyblue and Climax varieties was ever, rabbiteye varieties ripen a few weeks later than high- superior to that of the Sharpblue variety for the above condi bush varieties, when prices are considerably lower. No tions. studies which reported the effects of irrigation scheduling or the effectiveness of mulch as a production practice on It has been demonstrated that irrigation is essential for the growth of young blueberry plants were found in the the establishment of young blueberry plants and that it literature. The objectives of this research were to deter mine the effects of (1) irrigation scheduling and (2) mulch Florida Agr. Experiment Station Journal Series No. 9519. on growth of young blueberry plants.

Proc. Fla. State Hort. Soc. 101: 1988. 235