Jim Wills, Dave Lockwood, and Gary Honea

In 2003, the fourth year of this blueberry project, three aspects of the blueberry trials were considered; yield, canopy volume, and temperature/moisture beneath the row covering. The plot at MTES has the highest yield which was 9.2 lbs per plant from Tiftblue on black plus mulch row covering. The highest canopy volume occurred on the black plus mulch treatment at 57.1 cubic feet and the Tiftblue variety had the highest canopy volume with 68.3 cubic feet. The warmest temperatures at MTES occurred under the white treatment and at both HRES and PES the warmest temperatures occurred under the black treatment. The highest soil moisture at MTES and PES occurred under the black treatment while at HRES the highest soil moisture occurred under the bare plus 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 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.

Blueberry plots have been placed at three different experiment stations representing different geographical regions of the state; Plateau Experiment Station (PES) in Crossville, the Highland Rim Experiment Station (HRES) in Springfield, and the Middle Tennessee Experiment Station (MTES) in Spring Hill. At each location there were four replications of five treatments (row coverings); bare, bare plus mulch, black, black plus mulch, and white. Two varieties were grown in each treatment; Bluecrop (highbush)and Tiftblue (rabbiteye) plus individual variety pollinators. Temperature and moisture were measured beneath the plastic at each location. Yield was determined by picking berries from two representative plants of each variety in each treatment in each of the replications.

YieldHRES - An average production from an established plant would be about 12 to 15 lbs per plant; however, this is only the first year that berries have ben harvested for yield data. See Table 1 for yield by treatment, variety, and location and Table 2 for yield differences by variety and location. Tiftblue had the following yields by treatment: bare - 3.5, bare plus mulch - 5.1, black - 7.3, black plus mulch - 7.6, and white - 4.2. Black and black plus mulch had the highest yields and were statistically the same while the remaining three had the lower yields and were all statistically the same. Bluecrop had the following yields: bare - 1.1, bare plus mulch - 2.5, black - 2.0, black plus mulch - 2.4, and white - 2.8. All were statistically the same although white had the highest yield. Tiftblue had a statistically higher yield of 5.6 pounds per plant while Bluecrop had a yield of 2.2 pounds per plant.

MTES - Tiftblue had the following yields by treatment: bare - 4.1, bare plus mulch - 3.8, black - 9.1, black plus mulch - 9.2, and white - 5.3. Black and black plus mulch had the highest yields and were statistically the same while the remaining three had the lower yields and were all statistically the same. Bluecrop had the following yields: bare - 1.8, bare plus mulch - 1.6, black - 3.3, black plus mulch - 2.9, and white - 1.7. For both Tiftblue and Bluecrop black and black plus mulch had the highest yields and were statistically the same. The other three treatments in both varieties all had lower yields and were statistically the same. Tiftblue had a statistically higher yield of 6.3 pounds per plant while Bluecrop had a yield of 2.3 pounds per plant.

Table 1. Yield differences by treatment, variety and location - 2003

Note: Each column is a separate analysis, so letters cannot be compared between columns. Only within a column can letters be compared. Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

Table 2. Yield differences by variety and location - 2003.

Canopy volume in cubic feet per plant was estimated by treatment (both varieties considered together) and by variety (all treatments considered together). The analysis considered all three locations together. See Table 3 for canopy volume by treatment and year, Table 4 for canopy volume by variety and year, and Table 5 for canopy volume by location and year. For 2003 the volumes were as follows; black - 55.6, black plus mulch - 57.1, white - 37.9, bare plus mulch - 35.3, and bare - 23.7. Black and black plus mulch had the greatest canopy volumes and were statistically the same. White and bare plus mulch were in the mid range and were statistically the same. Bare was the lowest and was statistically different from the other two groups. Tiftblue overall had the highest canopy volume of 68.3 cubic feet, while bluecrop was statistically lower with 15.2 cubic feet. MTES had the highest canopy volume with 45.9 cubic feet which statisticall the same as the other two locations.

Table 3. Canopy volume by treatment and year.

Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

Table 4. Canopy volume by variety and year.

Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

Table 5. Canopy volume by location and year.

Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

HRES - Averages temperature and moisture measurements took into consideration the primary growing season portion of the year (April through October). See Table 6 for temperature beneath row covering by treatment and location and Table 7 for moisture beneath row covering by treatment and location. The temperature results in Centigrade are as follows; bare - 23.3, bare plus mulch - 23.1, black - 24.1, black plus mulch - 23.2, and white - 23.1. All were statistically the same except black which was warmer than the rest. Soil moisture was measured in centibars or kilopascals of matric potential. The results were: bare - minus 133.6, bare plus mulch - minus130.2, black - minus 136.9, black plus mulch - minus 154.2, and white - minus 152.1. Black plus mulch, which is the driest, and bare mulch are clearly statistically different while the other treatments are not clearly different (the more negative the value the drier the soil).

MTES - The temperature results in Centigrade are as follows; bare - 23.4, bare plus mulch - 23.8, black - 23.3, black plus mulch - 22.9, and white - 24.1. All were statistically the same except white which was warmer than the rest. The results were: bare - minus 33.0, bare plus mulch - minus 23.1, black - minus 21.4, black plus mulch - minus 24.3, and white - minus 24.4. Bare was the driest and was statistically different from all the others which were all wetter and were statistically the same.

PES - The temperature results in Centigrade are as follows; bare - 19.2, bare plus mulch - 19.1, black - 20.4, black plus mulch - 19.2, and white - 19.1. All were statistically the same except black which was warmer than the rest. The results of soil moisture were: bare - minus 27.4, bare plus mulch - minus 18.3, black - minus 14.9, black plus mulch - minus 16.3, and white - minus 22.7. Bare was the driest and was statistically different from all the others. Black and black plus mulch were slightly wetter and were statistically the same. Bare plus mulch and white were statistically intermediate between the other groups with white being almost as dry as bare.

Table 6. Soil temperature beneath row covering in degrees C by treatment and location - 2003.

Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

Table 7. Soil moisture in cb beneath the row coverings by treatment and location - 2003.

Means within a column followed by the same letter are not significantly different at the 0.05 lever of probability, Duncan’s multiple range tests.

HRES - For Tiftblue the row coverings of black and black plus mulch had the greatest yield and in Bluecrop yields for all coverings were the same. Tiftblue had greater yield than Bluecrop. Canopy volume, a measure of growth, considered both varieties together and was greatest for black and black plus mulch. Tiftblue had a greater canopy volume than Bluecrop. Temperature under the coverings was warmer for the black than for the others. Moisture was driest for the black plus mulch and bare plus mulch was the wettest.

MTES - For Tiftblue the row coverings of black and black plus mulch had the greatest yield and in Bluecrop yields for all coverings were the same. Tiftblue had greater yield than Bluecrop. Canopy volume, a measure of growth, considered both varieties together and was greatest for black and black plus mulch. Tiftblue had a greater canopy volume the Bluecrop. Temperature under the coverings was warmer for the white than for the others. Moisture was driest for the bare.

PES - Canopy volume, a measure of growth, considered both varieties together and was greatest for black and black plus mulch. Tiftblue had a greater canopy volume than Bluecrop. Temperature under the coverings was warmer for the black than for the others. Moisture was driest for the bare.

At this point in the trial, Tiftblue is the better choice in terms of plant growth and yield and black or black plus mulch is the best treatment for both Tiftblue and Bluecrop. The only anomaly is the "Bluecorp" yield on "white" at HRES, which ended up being statistically the same for all treatments. Otherwise, yield from "white" fell in the mid range when compared to the other treatments. There was a question of whether the white would increase production by delaying the time at which the plant would break dormancy to preclude cold weather damage early in the season. So far this phenomenon has not been seen. Moisture levels at both MTES and PES never dropped below recommended levels. Where soil moisture was adequate there is no clear correlation between the moisture or temperature and yield for any treatments. Where moisture levels were below desired 50 cb level due to irrigation management (HRES), yields for all treatments were generally lower. At HRES the black plus mulch and white seem to be the driest. Both treatments tend to deter moisture in the form of precipitation from soaking into the bed. The white beds were painted with latex paint and probably sealed many of the available opening in the ground cloth row covering. For the black plus mulch, the mulch formed a somewhat water repellent thatch to reduce infiltration into the bed.

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.