James B. Wills, Jr., Charles A. Mullins, Dave Lockwood, Dennis Deyton, Gary Honea, and

R. Allen Straw

Although the blueberry plants are not yet mature enough for production, mortality rate and growth were evaluated at all four locations in the fall of 2001. Temperature and moisture conditions beneath the various treatments of bed covering were recorded throughout the year at the Knoxville site. Mortality was determined at the end of the first growing season and growth was evaluated at the end of the second growing season. In the first year when the plants were getting established, mortality was greatest for plants grown on the bare ground and bare ground with mulch. In the second year substantial growth occurred. Tiftblue, the rabbiteye variety, demonstrated the greatest average growth. The highest temperature was under the black mulch and the highest soil moisture was under the black mulch.

There is growing interest in producing blueberries across the state of Tennessee. Blueberry consumption has not been as high in Tennessee as in some northern states. However, with the influx of people from northern areas into Tennessee who bring with them a taste for blueberries as well a Tennessee natives who are finding out about the many good qualitites of the blueberry that relate to health, the potential for increasing blueberry production is very good. Two of the basic types of blueberries are the Highbush and the Rabbiteye. Research was needed to evaluate at least one variety of each type and to evaluate various production systems for a period of five to ten years.

Two varieties of blueberries were selected for the trial that were expected to do well in Tennessee. The Rabbiteye variety selected was Tifblue and the Highbush variety was Bluecrop. The Bluecrop plants were obtained from a Michigan nursery and had a ball root system. Its selected pollinator was Duke. The Tiftblue were obtained from a nursery in North Carolina and were bare root. Its selected pollinator was Centura. The experimental design was randomized complete block with a split plot factorial arrangement of treatments. There were five treatments: raised bed with no mulch, raised bed with sawdust mulch, raised bed with black woven polyethylene ground cover, raised bed with black woven polyethylene ground cover and sawdust on top, and raised bed with black woven polyethylene ground cover painted white. All treatments were on raised six inch beds four to five feet wide with trickle irrigation and the capability to fertigate through that irrigation system. The five treatments were replicated four times. Pollinators were placed in border rows on each side of the plots, at one end of each treatment rows and approximately midway down the row of each treatment. Each treatment row consisted of five plants of each variety and two pollinators for a total of 12 plants. Research blueberry plots were placed at four UT experiment stations: Knoxville Experiment Station, Plateau Experiment Station, Highland Rim Experiment Station, and the Middle Tennessee Experiment Station. Plots at each station were basically the same with minor variations commensurate with the limits of the individual locations. At each location a total of 240 record plants were transplanted with additional plants in the borders and for replacement of mortalities. The plot at the Knoxville Experiment Station were instrumented to record temperature and moisture at 12-13 cm ( 5 in ). The goal was to evaluate survivability and productivity of the two varieties under the five different treatment systems. The plants were transplanted in late February and early March of 2000 after sawdust mulch was worked into the soil and sulfur added to bring the pH into the desired 5.2 to 5.5 range.

Since production is not expected until after approximately three years only survivability, canopy growth, and temperature and moisture will be addressed. The mortality at each of the four experiment stations is presented in Table 1 - 4. Canopy volume results are presented in Table 5 - 7 and do not include information from the Knoxville Experiment Station. Temperature and moisture results for the Knoxville Experiment Station are presented in Table 8.

After the first year of growth the highest mortality occurred for the bare soil treatment which was the control against which the other treatments were compared. The bare plus mulch treatment was better than the bare but was typically worse that the treatments using black, black plus mulch, and white.

Canopy volume was determined by taking two photographs of two plants of each variety representing average growth for each treatment in each replication. The photographs were taken from the front and side of each plant. A background of a known sized grid was used for each photograph. Average width, average depth, and height were determined and used to determine average volume of each plant. Table 5 presents the results by location. The Middle Tennessee Experiment station had the highest canopy volume at 6.59 cubic feet. Each location was statistically different. Table 6 gives the results by variety with Tifblue, the rabbiteye variety, having the greatest canopy volume of 6.09 cubit feet. The average canopy volume for the two varieties were statistically different. Table 7 shows the results by treatment. The bare treatment was statistically different from the rest of the treatments and had the lowest canopy volume of 2.23 cubit feet. Data from all three of the experiment stations were used in the statistical analyses.

The instrumented plot at the Knoxville Experiment Station provided average temperature and moisture at a depth of five inches in the raised bed. Mean yearly temperature varied from a low of 15.9 degrees C for bare to a high of 17.0 degrees C for the black. These two were statistically different from each other, and were also different from the remaining three treatments, black plus mulch, black, and white, which were statistically the same.

For the moisture measurements the wettest treatments were black plus mulch and white which were statistically the same. Bare plus mulch and black were slightly drier and were statistically

the same. Bare ground was the driest at -14.1 cb and was statistically different from the other treatments.

Table 1. Mortality at HRES, Crossville, 2000

Table 2. Mortality at KES, Knoxville, 2000

Table 3. Mortality at PES, Crossville, 2000

Table 4. Mortality at MTES, Spring Hill, 2000.

Table 5. Canopy volume results by location.

Table 6. Canopy volume results by variety.

Table 7. Canopy volume results by treatment.

Table 8. Temperature and moisture results at the Knoxville Experiment Station.

Email all comments and suggestions to ghonea@utk.edu
Copyright © 1999 by The University of Tennessee. All rights reserved.

This research represents one season's data and does not constitute recommendations.  After sufficient data is collected over the appropriate number of seasons, final recommendations will be made through research and extension publications.