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BUL296 Water Use in Establishment of Young Blueberry Plants 1 Dorota Z. Haman, Allen G. Smajstrla, Robert T. Pritchard, Fedro S. Zazueta and Paul M. Lyrene2 1. This document is BUL296, one of a series of the Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date August 1994. Reviewed December 2005. Visit the EDIS Web Site at http://edis.ifas.ufl.edu. 2. Dorota Z. Haman, Associate professor; Allen G. Smajstrla, Professor; Robert T. Pritchard, Graduate Research Assistant; Fedro S. Zaueta, professor, Agricultural and Biological Engineering Department; and Paul M. Lyrene, Professor, Horticultural Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean BLUEBERRY PRODUCTION IN FLORIDA Blueberries show great promise as a Florida fruit crop. Although blueberries are grown in many other states, Florida's climate allows fruit to reach maturity earlier, avoiding competition with growers in other states, thus commanding high prices. This advantage has been increased by the recent introduction of earlier-yielding highbush varieties. Currently, about 2,100 acres of blueberries are grown in Florida. This acreage is expected to expand as more growers take advantage of Florida's unique market window and new early-yielding blueberry varieties, and as existing growers expand their acreage. Presently, the blueberry acreage is evenly divided between rabbiteye and highbush varieties. However, for the last 10 years, new plantations have been almost exclusively planted to highbush varieties. Newly developed early ripening highbush varieties are of the greatest interest to Florida growers at this time. These varieties are lower yielding and much more difficult to grow than rabbiteye varieties, but the early ripening fruit brings high prices since it is the only blueberry available at this time. Before May 20, the average price is very high per pound. After June 1, the average price drops to around one dollar per pound. Highbush plants are more difficult to establish and have a shorter life expectancy than the rabbiteye varieties. They are also much more sensitive to water stress and they require frequent irrigation to grow and produce even when well established. Rabbiteye blueberries are native to Florida. These are relatively easy to grow and are considered the highest yielding type of blueberry for north Florida. The plants are more vigorous, longer living, higher yielding, and later ripening than the highbush variety. However, the rabbiteyes experience some problems with fruit setting due to pollination problems, thus yields do not always reach the expected levels. If pollination problems can be solved, it is very likely that rabbiteyes will again account for a significant percentage of new plantings since they are much easier to grow, and once established, live longer and have higher potential yields. During the establishment period the plants respond very well to irrigation; however, once well established, they are relatively insensitive to drought.
Water Use in Establishment of Young Blueberry Plants 2 In addition, rabbiteye blueberries can be mechanically harvested which results in a significant decrease in production cost. BLUEBERRY IRRIGATION The importance of irrigating young blueberry plants has been recognized for some time. In dry years, irrigation is very important during fruit formation. Berry size can be significantly increased in a dry year if irrigation is used to maintain moist soil conditions in the plant root zone. Sufficient moisture is not only critical during fruit production but is also important for the future of the plants since adequate irrigation during bud formation is critical for next year's crop (Lyrene and Crocker, 1991). Irrigation is critical to successful production in Florida because rainfall is typically low during the time of blueberry bud formation. Blueberries are often grown using organic mulches such as pine bark. The mulch provides protection against high temperatures, decreases evaporation from the soil, and with time, provides organic material to the soil. Organic mulches may also help reduce soil pH which is beneficial to the blueberry plant. Earlier research at the University of Florida demonstrated the importance of an organic mulch ground cover and precise irrigation scheduling on the growth of young rabbiteye and highbush blueberry plants (Haman et al., 1988). The recommendations presented in this publication were developed based on a three year experiment on water requirements for establishment of young blueberry plants which was conducted at the University of Florida. The project was partially funded by the St. Johns River and the Southwest Florida Water Management Districts. Both native rabbiteye and newly developed early-yielding highbush varieties were studied. Two-year old, container-grown plants were transplanted to the field at the beginning of 1991. The experiment ended in December 1993. Total water use (evapotranspiration) of the plants, irrigation requirements, crop yield, and vegetative plant growth were evaluated for the three years after transplanting. Three different threshold levels of soil water tension were evaluated for scheduling irrigations. The threshold soil tension were set at 10 centibars (cb), 15 cb, and 20 cb. In Florida, blueberries are usually grown on sandy soils with low water holding capacities and large pore spaces. Thus, water applications must be frequent and relatively small to avoid water losses from the root zone. This requires precise irrigation scheduling. Microirrigation, which was used in the experiment on establishment of blueberry plants, applies water directly to the crop root zone. The amount and placement of water can be precisely controlled with this system to minimize application losses. The microirrigation system was controlled using magnetic switching tensiometers (Smajstrla et al., 1988). With the microirrigation system used in this study, water was not applied to the grass alleyways between plant rows. Also, organic pine bark mulch minimized evaporation losses from the soil surface. Irrigation requirements would need to be adjusted for other plant sizes, irrigation systems and/or production practices. For example, a greater volume of water would be required with a sprinkler irrigation system because water would be applied to the entire soil surface rather than being limited to the mulched area near each plant. Figure 1 and Figure 2 present the cumulative irrigation for both varieties of blueberry during three years of the experiment. The significant increase in the slope of the lines during the last year of the experiment for all treatments (with exception of 20-cb highbush) reflects the higher water requirement of the larger plants and the lower rain contribution during that year. Figure 1. Cumulative irrigation over three years of the experiment for Rabbiteye blueberries.
Water Use in Establishment of Young Blueberry Plants 3 Figure 2. Cumulative irrigation over three years of the experiment for Highbush blueberries. YOUNG BLUEBERRY WATER USE Water use in gal/acre and inches/acre for the first three years after transplanting for both varieties of blueberries is presented in Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 The numbers were developed for different plant densities depending on the field spacing between the plants. These quantities are relatively small because they are specific for the young, small, microirrigated blueberry plants studied in this research. The portion of the water demand which must be supplied by irrigation depends on system efficiency and rainfall effectiveness and can be calculated using the water budget method. RESPONSE OF YOUNG BLUEBERRY PLANTS TO IRRIGATION Growth of blueberry plants was measured monthly. The volume of each plant canopy was calculated from three measurements: the height, the width along the plant row, and the width perpendicular to the row. Plant volumes increased each year for all treatments. Both plant size and rate of increase were greater for rabbiteye plants as compared to highbush plants. Among highbush plants only the 10-cb treatment showed significant growth, most of which occurred in the last year of the experiment. During 1993, the 10-cb plants grew almost 2 ft, while the 15-cb and 20-cb highbush plants showed very little increase in height in all three years due to water stress and poor establishment of the root system. Overall, the 10-cb treatment had the highest growth rate for both varieties. In 1993, the rate of growth for the 15-cb and 20-cb treatments was very small and significantly lower than the 10-cb treatment ( Figure 3 ). Figure 3. Blueberry growth during three years of the experiment. Rabbiteye plant heights increased mainly in the first year after transplanting (1991), especially in the 10-cb treatment. During that year, the 10-cb plants reached approximately 5 ft. The 15-cb and 20-cb treatments were slightly shorter and reached 5 ft at the end of the second year. By the end of 1993, the 10-cb rabbiteye treatment plants were approximately 6 ft tall with 15-cb slightly shorter at 5.6 ft and 20 cb at 5.3 ft. In 1991, following common practice for young plants to stimulate vegetative growth, the flowers were removed from the plants, preventing fruit from setting. This is reflected in the 1991 plant growth pattern. Most of the plants showed an increase in volume in all months until September. In 1992 and 1993, most of the increase in plant size occurred during the three months after fruit harvest. Little change in plant size occurred during the spring months as fruit was set and grew to maturity. Fruit production data were collected during the last two years of the research and are presented in Table 5 The two types of rabbiteye plants yielded differently and for this reason are presented separately.
Water Use in Establishment of Young Blueberry Plants 4 The fruit for all three cultivars matured at different times of the year, and yields varied as a function of time of harvest. In both years, yields were lowest for the early-producing Sharpblue (highbush) variety, largest for the late-producing Powderblue (rabbiteye) variety, and intermediate for the midseason rabbiteye variety, Premier. This is important since timing of harvest is critical to blueberry growers. Early-producing varieties are in great demand because early yields command much higher market prices. Sensitivity to water stress was greatest in the highbush variety. Both vegetative growth and yield were strongly dependent on irrigation. Only the well-watered (10 cb) treatment was well established and healthy at the end of three years. The plants in this treatment were much larger and produced significantly more berries. All rabbiteye plants were well established by the end of three years and there were only small differences between the water treatments. Figure 4 shows the annual distributions of monthly ET for the well-watered rabbiteye and highbush plants as a function of time during the first three years after transplanting. The ET pattern is consistent with the patterns of climate demand as measured by Penman ETo (reference evapotranspiration). In 1991 the peak monthly ET occurred in June. For all three years, the peak monthly ET for both varieties occurred in July. This closely follows the peak climate demand, and it is largely a result of levels of solar radiation and temperatures. Figure 4. Potential evapotransporation calculated from the Penman equation as compared to actual evapotranspiration of highbush and Rabbiteye blueberries. Evapotranspirational (ET) rates were larger for the rabbiteye plants as compared to the highbush plants. This difference was due to plant size and growth characteristics. The rabbiteye plants are more vigorous and rapidly-growing than the highbush plants. CONCLUSIONS AND RECOMMENDATIONS The establishment and water requirements of plants are strongly dependent on the blueberry variety. Two typical types of blueberry plants were evaluated in this experiment: rabbiteye, which is native to Florida, and highbush, which is an introduced variety. Growers are very interested in highbush plants due to their early ripening and the high prices which blueberries bring early in the year. The rabbiteye variety is easier to establish and easier to grow successfully under Florida conditions. Plants grow rapidly after transplanting, and were relatively insensitive to imposed water stresses up to 20 cb. As compared to highbush plants, rabbiteyes have a deeper root system which allows them to uptake water from a larger volume of soil, resulting in more efficient irrigation scheduling and fewer losses to deep percolation. At the end of the third year of this project, the establishment of rabbiteye blueberries was good under all treatments. There was only small visible difference among plants. As compared to rabbiteye, the highbush variety is much more difficult to establish and requires more precise water management. Plants exhibit high sensitivity to water stress and require frequent irrigation for good establishment. It takes longer for highbush plants to develop a root system. Most of the roots in this variety are located relatively close to the soil surface, which makes efficient irrigation scheduling more difficult. As a result, more water is lost to deep percolation. Well-watered highbush plants (10-cb treatment) were very well established at the end of the experiment. However, two drier treatments showed much less vegetative growth and much lower yields than the well-watered plants. It can be concluded that
Water Use in Establishment of Young Blueberry Plants 5 Table 5. Table 5. Blueberry yield in lbs/acre* as a function of the three irrigation levels during first two years of fruiting. Year Irrigation Treatment Rabbiteye Powderblue Rabbiteye Premier Highbush 1992 10 cb 7,760 3,680 3,080 15 cb6,2503,450 1,060 20 cb 8,310 3,360 520 1993 10 cb 5,590 4,690 2,200 15 cb5,2604,430 2,040 20 cb 5,890 3,710 820 Yield calculated based on plant density of 1000 plants /acre the establishment of highbush blueberries under Florida conditions will not be successful without irrigation, and that irrigations should be scheduled at 10 cb. REFERENCES Haman D.Z., A.G. Smajstrla and P.M. Lyrene. 1988. Blueberry response to irrigation and ground cover. Proc. Fla. State Hort. Soc. 101:235-238. Lyrene, P.M. and T.E. Crocker. 1986. Florida blueberry handbook. Circular 564. Univ. of Fla. Coop. Ext. Ser., Gainesville, FL. 15 pg. Lyrene P.M. and T.E. Crocker. 1991. Commercial blueberry production in Florida. SS-FRC-002. Univ. of Fla. Coop. Ext. Ser., Gainesville, FL. 49 Smajstrla A.G., D.Z. Haman and P.M. Lyrene. 1988. Use of tensiometers for blueberry irrigation scheduling. Proc. Fla. State Hort. Soc. 101:232-235.
Water Use in Establishment of Young Blueberry Plants 6 Table 1. Table 1. Water use in inches per acre per month as a function of density for rabbiteye blueberries. Density (plants/acre) 600 700 800 900 1000 1100 1200 Year 1 APR 0.2 0.3 0.3 0.3 0.4 0.4 0.4 MAY1.01.21.31.51.71.8 2.0 JUN188.8.131.52.12.32.5 2.8 JUL184.108.40.206.22.42.7 2.9 AUG220.127.116.11.12.32.6 2.8 SEP18.104.22.168.92.22.4 2.6 OCT22.214.171.124.61.82.0 2.2 NOV0.70.80.91.11.21.3 1.4 DEC 0.3 0.4 0.4 0.5 0.5 0.6 0.6 Year 2 JAN 0.3 0.4 0.4 0.5 0.5 0.6 0.6 FEB0.30.40.40.50.60.6 0.7 MAR0.50.60.70.80.91.0 1.1 APR126.96.36.199.71.92.1 2.3 MAY188.8.131.52.42.62.9 3.2 JUN184.108.40.206.42.73.0 3.2 JUL2.02.22.52.93.23.5 3.8 AUG1.91.72.02.22.52.7 3.0 SEP220.127.116.11.71.92.1 2.3 OCT0.91.11.21.41.51.7 1.8 NOV0.60.60.70.80.91.0 1.1 DEC 0.3 0.4 0.5 0.5 0.6 0.6 0.7 Year 3 JAN 0.3 0.4 0.5 0.5 0.6 0.6 0.7 FEB0.30.30.30.40.40.5 0.5 MAR0.40.40.50.50.60.6 0.7 APR18.104.22.168.92.12.3 2.5 MAY2.63.03.43.94.34.7 5.2 JUN22.214.171.124.34.85.3 5.8 JUL126.96.36.199.75.35.8 6.3 AUG188.8.131.52.65.15.6 6.1 SEP2.63.03.53.94.34.8 5.2 OCT184.108.40.206.71.92.1 2.3 NOV0.60.70.91.01.11.2 1.3 DEC 0.6 0.7 0.8 0.9 1.1 1.2 1.3 Data not available for first 3 months of the first year. Table 2. Table 2. Water use in inches per acre per month as a function of density for highbush blueberries. Density (plants/acre) 600 700 800 900 1000 1100 1200 Year 1 APR 0.3 0.4 0.4 0.5 0.5 0.6 0.6 MAY0.30.40.40.50.60.6 0.7 JUN0.70.91.01.11.21.4 1.5
Water Use in Establishment of Young Blueberry Plants 7 Table 2. JUL0.70.91.01.11.21.4 1.5 AUG0.70.81.01.11.21.3 1.4 SEP0.60.80.91.01.11.2 1.3 OCT0.50.60.70.80.90.9 1.0 NOV0.50.50.60.70.80.8 0.9 DEC 0.3 0.4 0.4 0.5 0.5 0.6 0.6 Year 2 JAN 0.4 0.4 0.5 0.6 0.6 0.7 0.7 FEB0.40.40.50.50.60.7 0.7 MAR0.40.50.60.60.70.8 0.8 APR0.50.60.70.80.80.9 1.0 MAY0.70.80.91.01.11.2 1.4 JUN0.91.01.11.31.41.6 1.7 JUL220.127.116.11.71.92.1 2.9 AUG18.104.22.168.71.92.1 2.2 SEP1.01.11.31.51.61.8 1.9 OCT0.81.01.11.31.41.5 1.7 NOV0.50.60.70.80.91.0 1.0 DEC 0.3 0.4 0.4 0.5 0.5 0.6 0.6 Year 3 JAN 0.2 0.2 0.2 0.2 0.2 0.3 0.3 FEB0.20.20.30.30.30.4 0.4 MAR0.30.40.40.50.606 0.7 APR1.01.21.41.61.71.9 2.1 MAY22.214.171.124.73.03.3 3.6 JUN2.02.42.73.03.43.7 4.0 JUL126.96.36.199.43.84.2 4.6 AUG188.8.131.52.23.63.9 4.3 SEP2.02.32.63.03.33.6 3.9 OCT184.108.40.206.82.02.2 2.4 NOV1.01.21.31.51.71.8 2.0 DEC 1.0 1.2 1.4 1.5 1.7 1.9 2.0 Data not available for first 3 months of the first year. Table 3. Table 3. Water use in gallons per acre per month as a function of density for rabbiteye blueberries. Density (plants/acre) 600 700 800 900 1000 1100 1200 Year 1 APR 5922 6908 7895 8882 9869 10856 11843 MAY272393177936379408594539849938 54478 JUN378134348549697559096212168333 74546 JUL393124586552417589696552172073 78625 AUG378654417650487567976310869419 75730 SEP350034083746671525045833864172 70006 OCT296413458139521444614940154341 59281 NOV189162206925221289743152734679 37832 DEC 8323 9710 11097 12485 13872 15259 16646 Year 2 JAN 8656 10098 11541 12984 14426 15869 17312 FEB89481043911931134221491316405 17896
Water Use in Establishment of Young Blueberry Plants 8 Table 3. MAR147451720219660221172457527032 29490 APR305063559040674457595084355927 61012 MAY429615012157281644417160178762 85922 JUN437665106058355656497234380238 87532 JUL518086044369078777128634794982 103616 AUG400514672653401600766675173426 80101 SEP310963627941462466455182757010 62193 OCT244922857432656367384082044902 48984 NOV148751735419833223122479127271 29750 DEC 9321 10874 12427 13981 15534 17088 18641 Year 3 JAN 9352 10910 12469 14028 15586 17145 18703 FEB670378208937100541117212289 13406 MAR95101109512680142651585017435 19020 APR335373978144717503065589661485 67075 MAY701348182393511105200116889128578 140267 JUN7835691415104475117534130593143653 156712 JUL8560399870114137128404142671156938 171205 AUG8279396592110391124190137989151788 165587 SEP707628255694350106144117937129731 141525 OCT314503669141933471755241657658 62899 NOV172352010822981258532872631598 34471 DEC 170069 19914 22789 25604 28449 31294 34138 Data not available for first 3 months of the first year. Table 4. Table 4. Water use in gallons per acre per month as a function of density for highbush blueberries. Density (plants/acre) 600 700 800 900 1000 1100 1200 Year 1 APR 8356 9749 11141 12534 13927 15319 16712 MAY88821036311843133231480416284 17765 JUN200352337426713300523339136730 40069 JUL201662352726888302493361036971 40332 AUG192452245325660288683207535283 38490 SEP174362034223248261532905931965 34871 OCT139491627318598209232324825572 27897 NOV123371439316449185052056122617 24673 DEC 8422 9825 11229 12633 14036 15440 16843 Year 2 JAN 9915 11567 13219 14872 16524 18177 19829 FEB95581115112744143371593017523 19116 MAR114041330515205171061900720907 22808 APR136651594218220204972277525052 27330 MAY183782144124504275663062933692 36755 JUN231372699330849341053856142417 46274 JUL309953616141327464935165956825 61991 AUG304213549140561456315070155772 60842 SEP263343072335112395024389148280 52669 OCT227402653030320341103790041690 45480 NOV141711653218894212562361825979 28341
Water Use in Establishment of Young Blueberry Plants 9 Table 4. DEC 8533 9956 11378 12800 14222 15645 17067 Year 3 JAN 3988 4652 5317 5981 6646 7311 7915 FEB513459906846770185579413 10268 MAR89941049311992134911499016489 17987 APR279823264537309419734663651300 55964 MAY490325720465976735488172089892 98064 JUN5479363925730578218991321100453 109585 JUL62157185168287693235103595113954 124314 AUG5822867933776388734397047106752 116457 SEP533556224771140800328892597817 106710 OCT320573740042743480855342858771 64114 NOV272553179836340408834542549968 54510 DEC 27722 32343 36963 41584 46204 50824 55445 Data not available for first 3 months of the first year. Table 6. Table 6. Water use per plant in gallons during first three years of blueberry establishment. Year 1 Year 2 Year 3 Month HB* RE* HB RE HB RE Jan 17 14 7 16 Feb--16159 11 Mar--191515 16 Apr1410235147 56 May1545317282 117 Jun3362397291 131 Jul34665286104 143 Aug3263516797 138 Sept2958445289 118 Oct2349384153 52 Nov2032242546 29 Dec 14 14 14 16 46 28 *HB-highbush RE-rabbiteye