Use of Tensiometers for Blueberry Irrigation Scheduling
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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 switching tensiometers 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 an au 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.