Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: Weekly collection of leachate from lysimeters continued during the current reporting period to determine ET for mature blueberry plants grown on pine bark beds and in pine bark incorporated soil. For each soil type two irrigation schedules were used: 1) irrigation once per day in the absence of rain; and 2) irrigation twice per day in the absence of rain. The same amount of water per day was applied to all treatments. Weekly values of plant water use (ET) were averaged to determine monthly ET values. On March 6, 2012 a grower field day was conducted at the research site and preliminary results were discussed. PARTICIPANTS: Eric Ostmark - field techician. Maintained equipment and planting site. Tyler Austin - part-time employee. Collected lysimeter data. TARGET AUDIENCES: A blueberry grower field day was conducted at the experimental site on March 6, 2012. Preliminary results were discussed. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results were similar to those presented during the previous year in that there was a rapid increase in water use during foliation (spring) and a relatively high water demand during the later stages of berry development. Water demand was reduced during the period immediately following summer pruning which removed a significant amount of leaf canopy after which there was a steady increase in water use throughout the summer. The greatest plant water demand was during late summer (August and September). Plant water use steadily declined during the onset of fall and winter. Our previous estimates of blueberry plant water use in Florida were reaffirmed to be in excess of 2 gallons per plant per day during peak water demand periods for a mature southern highbush blueberry plant. No differences between the soil treatments, or the once per day verses twice per day irrigation schedules, were observed.
Publications
- No publications reported this period
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: New lysimeter testing began in 2010 but was interrupted by numerous freeze protection events during the winter and spring when large amounts of water were applied to the field and overtopping and temporary flooding of lysimeters occurred. A total of 32.3 inches of water was applied to the blueberry field either as overhead irrigation or rainfall during the February/March time frame. The wick-assisted drainage system was not able to drain rapidly enough under these conditions and overtopping and temporary flooding of the lysimeters occurred which prevented preliminary testing of lysimeters during this period. In mid-March, water was extracted from the flooded lysimeters and two the eight wicks were removed from each lysimeter and replaced with 2-inch well screens cut longitudinally and glued to the base plate above the drain pipe. Three to four inches of pea gravel and 3 inches of builders' sand were applied above the well screens before the soil was repacked. After installation of the well screens, the lysimeters appeared to drain properly and lysimeter testing resumed in late March, 2010. Beginning in April, weekly and monthly plant water use was determined. Water use increased from April to May which coincided with the harvest period of 2010. Moreover a weekly increase in plant water use beginning in mid-May and peaking in late May coincided directly with the major period of fruit harvest in 2010. Summer pruning removed approximately 30 to 40% of the existing foliage and was done in early June and appeared to be responsible for the decline in plant water use observed in June. Monthly averages of daily plant water use increased from June through August and then declined rapidly through the fall and winter. The highest daily plant water use was over 2 gallons/day in August. The lowest water use period was in January when temperatures were the lowest for the year and few leaves were present on blueberry plants. PARTICIPANTS: Paul Miller - field technician. Maintained equipment and planting. Assisted in data collection. Luis Mejia - graduate student. Assisted with data collection and analysis. TARGET AUDIENCES: Information on this project was reported at the Florida Blueberry Growers Association meeting in October, 2010. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Estimates of yearly water use for bearing southern highbush blueberry plants in Florida were calculated. Annual per plant water use was determined t be approximately 658 gallons in 2010/2011. Annual water use (ET)of a mature southern highbush blueberry planting with a density of 1452 plants/acre was determined to be approximately 757,214 gallons per acre during the same period.
Publications
- Dourte, D.R., D.Z. Haman and J.G. Williamson. 2010. Crop water requirements of mature southern highbush blueberries. International Journal of Fruit Science. 10(3): 235-248.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Blueberry root systems in pine bark culture are confined to the pine bark layer. As such, plants have low soil water reserves available for plant uptake. Where possible, pulsing low volume irrigation systems multiple times per day may be beneficial in pine bark culture during periods of high water demand. New lysimeters were designed during 2008-09 and installation was begun at the PSREU site in Citra, Fla., where testing is underway. The new lysimeters are wick-assisted drainage type. Irrigation, precipitation, and soil moisture content are measured and ET crop is calculated as the difference between water applied to the lysimeter (irrigation plus precipitation) and water collected from the drainage apparatus plus an estimate of water stored in the soil contained in the lysimeter. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: New lysimeters (wick-assisted drainage type) were designed and built during 2008-09 for use at the PSREU in Citra, Fla. The new lysimeter is designed to prevent loss of water from surface or subsurface flows which is believed to have resulted inflated estimates for ETc and Kc with the original lysimeter.
Impacts
Lysimeters were redesigned during 2008-09 at the PSREU in Citra, Fla. where microsprinkler irrigation is used. Infiltration rates from microsprinkler irrigation were much higher (about 5x) than for overhead irrigation used at the IGAP site. Water was lost from surface or subsurface flows resulting in inflated estimates for ETc and Kc (about twice that of the commercial field in IGAP where overhead irrigation was used). The new lysimeters are designed to prevent water loss from surface or subsurface water flows. Eight of the 12 lysimeters were installed during December 2009. The remaining four lysimeters will be installed during 2010. Testing of the installed lysimeters began in December, 2009. Lysimeters were installed in two soil management systems: 1) pine bark beds; and 2) pine bark incorporated soils. Two irrigation treatments are used in each soil management system where supplemental irrigation is applied once or twice daily in the absence of rainfall.
Publications
- No publications reported this period
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Blueberry root systems in pine bark culture are confined to the pine bark layer. As such, plants have low soil water reserves available for plant uptake. Our preliminary finds suggests that commercial blueberries grown in pine bark culture are often over-irrigated at intervals that are too infrequent. More frequent irrigations of shorter duration may relieve moisture stress and use less water. Where possible, pulsing low volume irrigation systems multiple times per day may be beneficial in pine bark culture during periods of high water demand. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: A new lysimeter design will be used beginning in 2009 at the PSREU in Citra, Fla. where microirrigation is used. Infiltration rates from microirrigation were much higher than from overhead irrigation used at the IGAP site. Water was lost from surface or subsurface flows resulting in inflated estimates for ETc and Kc (about twice that of the commercial field in IGAP). The new lysimeter design will prevent water loss from surface or subsurface water flows and prevent loss from overtopping.
Impacts
Crop evapotranspiration (ETc) was measured for the 2007 - 2008 year at the commercial blueberry planting in Island Grove, Fla. Seasonal responses to water use occurred with generally higher water use during periods of active growth and warm temperatures. The current lysimeter design appeared to function in the commercial field where overhead irrigation was used and water application/infiltration rates were relatively slow (6.4 mm/hr). However, the high ETc and Kc values observed in 2007 at the Plant Science Research and Education Unit (PSREU) in Citra, Fla. where irrigation infiltration rates from micro-sprinklers were about 5 times greater (33.4 mm/hr)than with overhead sprinklers were a concern. The conclusion is that water was lost from the system when microsprinkler irrigation was used and infiltration rates were high, resulting in inflated estimates of ETc and Kc. A new lysimeter has been designed which will prevent loss of water from surface or subsurface flow and from overtopping of lysimeters. The new lysimeters will be installed during 2009 at the PSREU in Citra, Fla.
Publications
- Dourte, D.R. 2007. Crop Water Requirements and irrigation management of Southern Highbush Blueberries. Master of Science Thesis. University of Florida.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Preliminary results for crop evapotranspiration (ETc) and crop coefficients (Kc) were determined for 08/01/06 through 06/01/07 at the commercial blueberry planting in Island Grove, Fla. Seasonal and physiological responses for ETc were observed. The seasonal effects were most noticeably in late fall as crop water use declined with falling ETo values. Kc values were also low in June following summer pruning which removes a large portion of the existing leaf canopy. As shoots re-grow in response to summer pruning, Kc values increase in July and August. By August, there was considerable young, immature, foliage present. Although stomatal conductance was not measured, these immature leaves probably had limited stomatal control which resulted in high Kc values in August. Higher than usual cuticular transpiration from immature leaves may also be partially responsible for the large Kc values observed in August. During September, the foliage matured, stomatal control increased, and Kc values declined. A large Kc value was observed in April, 2007, and was probably due to the rapid growth rate of berries just prior to harvest. April was the primary month for fruit harvest. Blueberries are known to undergo a rapid growth phase just prior to fruit maturity. The photosynthetic response to the high sink demand of rapidly growing fruit likely resulted in the transpiration increase observed on bearing plants during April. ETc and Kc values for young plants at the Plant Science Research and Education Unit (PSREU) in Citra, Fla. were determined. ETc and Kc values were larger than expected and are difficult to explain with certainty. There was a high correlation between ETc and applied water, (r = 0.998). This supports the conclusion that some water was probably lost from the system and included in the calculations of ETc. Application rates were about 5 times greater for micro-sprinklers at PSREU compared to the overhead sprinklers at the IGAP experiment (33.4 mm/hour compared to 6.4 mm/hour). The rapid application rate of water to the relatively small surface area of irrigated soil probably allowed for some surface and subsurface lateral movement of water out of the lysimeter area in the micro-sprinkler irrigated field. Additionally, the dry soil in between rows of micro-irrigation may have facilitated lateral movement of water out into the dryer soil between the irrigated rows. Neither of these processes would have occurred in the overhead irrigated field where irrigation was evenly applied to the entire field at a much slower application rate. At present, this appears to be the most plausible explanation for the observed differences in Kc between the two sites. . Work is underway to identify and correct the source of high ETc values observed in 2007 at PSREU. Preliminary results have been reported that the Florida Blueberry Growers' Association Field Day. PARTICIPANTS: Paul Miller - field technician. Maintained equipment and planting. Collected and processed data. Bradley Ferguson - graduate student. Collected and processed data. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Lysimeters at the PSREU site in Citra, Fla. are being redesigned. The current design is not adequate for micro-spinkler irrigated plants do to the high application rate of water and loss of water by runoff and/or subsurface lateral movement. A new lysimeter design has been developed and will be tested in 2008.
Impacts
Blueberry root systems in pine bark culture are largely confined to the pine bark layer. As such, plants have low soil water reserves available for plant uptake. Our preliminary finds suggests that commercial blueberries grown in pine bark culture are commonly over-irrigated at intervals that are too infrequent. More frequent irrigations of shorter duration may relieve moisture stress and use less water.
Publications
- No publications reported this period
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Progress 10/01/05 to 09/30/06
Outputs
Experiment 1 This experiment is located on a commercial blueberry farm and compares grower-controlled irrigation management with shorter, daily timer-controlled schedules. Lysimeters were used to facilitate a water balance and the determination of crop ET. Eight mature southern highbush plants were removed from rows with minimal root system disruption, extraction being aided by large, wooden transplanting trays that were inserted below the root zone and used to lift and move the plants. Movement of the plants was required for installation of lysimeters below plants. There are four lysimeter plants in an area of grower-controlled irrigation and four lysimeter plants in an area of researcher-controlled irrigation on the same commercial farm. Excavation for lysimeter sites was done to situate the lysimeters at a depth of 12 inches (from soil surface to lysimeter rim). Soil removal and repacking into lysimeters was done in a manner that minimized soil layer disruptions. A
plastic well screen, with attached vacuum tube, was installed in the bottom of each lysimeter, covered with coarse sand, and the lysimeters were repacked with soil in the appropriate soil-type order. The mature plants were transplanted above the lysimeters in the pine bark culture that they were removed from. Plants were selectively hand pruned to minimize any transplant shock that may have occurred. Irrigation system was tested for rate and uniformity of water application. An on-site weather station records weather data (temperature, radiation, humidity, precipitation and wind velocity). The water balance is performed on a weekly basis. Water that percolates below plant root zones is collected by the lysimeter and extracted with a vacuum pump that connects to the tube from the well screens. With lysimeters to measure deep percolation water, all water balance terms will be measured (neglecting advective flows), enabling determination of ET of mature blueberry plants. Expriment 2.
Located at a research farm in north-central Florida, these lysimeter specifications and installation methods are the same as described in Experiment 1 above. Eighteen lysimeters were installed (three for each soil/irrigation combination). Four additional plots of each soil/irrigation combination will be used to access treatment effects on plant growth and development. Eighteen-month old plants were transplanted in single rows with 10 ft. between rows and 3 feet between plants within rows. Experimental plots consist of 4 plants, two guard plants on either end and 2 center plants used for data collection. Overhead irrigation is provided for initial plant establishment and freeze protection. Risers are spaced 40 feet by 40 feet and provide 100 percent overlap of water distribution. Pressure is regulated to 60 psi and Rainbird PWSH sprinkler heads with 9/16 in. nozzles are used. The field was transferred from overhead to micro-sprinkler irrigation after plant establishment. The
micro-irrigation system consists of 6 separate zones (one zone per soil/irrigation treatment). Each plant is watered by two semi-circle nozzles one on each side of the plant.
Impacts
Results from the experiments described above will determine water use requirements for blueberries grown in pine bark culture in Florida. Information on water use and requirements for optimum growth should result in more efficient irrigation practices by growers and reduced water consumption by the industry.
Publications
- No publications reported this period
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