As many tobacco and traditional row crop growers are looking for ways to supplement farm income, vegetables and small fruits are receiving much attention. Due to the potential returns/A, annual plasticulture strawberries have received significant attention. However, the annual plasticulture strawberry production system is still considered marginal for use in much of the Mid-South. Therefore, an experiment was conducted to evaluate yield, berry size, and maturity date of ‘Chandler’ strawberries grown on black and white plastic mulch, with and without row covers at the University of Tennessee Plateau Experiment Station located near Crossville, TN.

Plants grown on black plastic mulch tended to produce higher yields than plants grown on white plastic mulch. The plants grown on black plastic mulch also produced fruit earlier than plants grown on white plastic mulch. The use of row cover also influenced maturity. Plants that were covered in January began producing berries earlier than plants that were covered in March or never covered at all. Plants that were covered in March produced berries earlier than plants that never received row covers. Plants grown on white plastic mulch that were never covered produced larger berries than plants grown using any other treatment combination. It appears that the use of row covers and white plastic mulch could be used to spread the harvest season in annual plasticulture strawberry production. The use of row covers in conjunction with black plastic mulch could start production 1 week earlier than "normal". The use of white plastic mulch could delay maturity, extending the season a week later in the summer. However, the later maturing treatments also tended to concentrate their production into a shorter harvest window.

With the present state and uncertain future of the tobacco industry, many growers are looking to vegetable and small fruit enterprises to augment farm incomes. Even traditional row crop farmers are looking to these enterprises to generate some profit. Among the most lucrative of these enterprises is annual plasticulture strawberries, which can produce potential gross returns of over $20,000/A. However, this production system requires significant investments of capital, labor, and management. Establishment of the crop requires an investment of $4,000 to $6,000/A in the fall before the crop will be harvested the following spring. Total production costs will range in the neighborhood of $10,000 to $12,000/A.

Much of the information and technology for this production system originated in other areas of the country. Therefore there has been concerns about the applicability to Tennessee growing conditions. For example, the industry began more than 20 years ago in California. Florida producers were able to make some modifications and utilize the technology. North Carolina Researchers began working with the system in the early 1980's, and have developed a significant industry in the Coastal Plain and Piedmont areas. Charlie O’Dell has worked over the last 10 years adapting the system to the higher elevations of Virginia. However, the system is still considered marginal for use in the Mid-South (Kentucky, Tennessee, and higher elevations of Virginia). One of the concerns of this production system has been related to winter temperature extremes. The varieties used in this production system were bred in California and Florida, where the climate is very tempered. Prolonged periods of temperatures below 10EF have been found to damage crowns of these varieties. Therefore, crop or row covers have been utilized to protect the plants during the winter months. Row covers have also been utilized to buffer plants against sudden temperature drops, as well as additional protection during freeze events. However, warm spells in late winter, while the row cover is still applied, has resulted in early flower development, resulting in the necessity to begin frost protection earlier than desired. Therefore, in 1999 through 2000, the yield, berry size and maturity date of ‘Chandler’ strawberries was compared on black and white plastic, with and without row covers at the University of Tennessee Plateau Experiment Station located near Crossville, TN.

The plot area had been used for snap bean tillage research earlier in the season. Due to poor stands, the test had been abandoned; therefore the entire area was mowed in preparation for use. To conserve moisture, the plot area was not plowed until the day before fumigation of the plots. The entire area was moldboard plowed at a depth of 6 to 8 inches on September 2, 1999. The soil was disked early on the morning of September 3. Two hundred lb/A of 15-15-15 and 300 lb/A of 0-46-0 were broadcast and incorporated with a rototiller the same day. All beds were fumigated with methyl bromide / chloropicrin 67:33 (MB 67:33) at 400 lb/A. The MB 67:33 was injected 7 inches deep during bed formation, and covered immediately with plastic mulch film. Half of the field was covered with black plastic mulch and the other half was covered with white plastic mulch. Holes were punched in the plastic mulch on September 20, 1999, 1 inch of water was applied through the trickle irrigation system on September 22, and ‘Chandler’ strawberry transplants were set on September 25. An additional inch of water was applied on October 3, and 0.5 inches was applied on each of October 27 and 28.

Covertran® crop covers (0.5 oz/yard²), to promote plant development and aid in freeze protection, were applied on January 15 and March 11, 2000. Another row on each color plastic was never covered. Overhead irrigation was utilized for frost / freeze protection during March and April. Ten lb/A of both calcium nitrate and potassium nitrate were applied through the trickle irrigation system on April 7, 20, and 27 in 0.25 inches of water, and on May 5 and 15 in 0.5 inches of water. A total of 50 lb/A N was applied in the spring. Elevate at 0.75 lb ai/A was applied for Botrytis control and Danitol at 0.2 lb ai/A was applied for spittle bug control on April 29. Harvest began on April 25 and continued every 2 to 3 days until May 30, for a total of 16 harvests. Berries from each harvest were counted and weighed. Experimental design was a randomized complete block with 4 replications. All data were analyzed using ANOVA procedures, and means of dependent variables found to be significant at the 0.05 level of probability were separated using Student Newman Keuls mean separation technique.

Overall the season was mild, therefore the plants that were transplanted a week to 10 days later than recommended, developed and yielded quite well. The plants grown on black plastic mulch tended to yield more than plants grown on white plastic mulch (Table 1). Plants grown on white plastic mulch that were covered with a row cover in January produced significantly lower yields than all other treatment combinations. Applying a row cover in March appeared to lower yields of plants on the black plastic mulch and increase the yield of plants on white plastic mulch. Some preliminary temperature data suggests that the temperatures were warmer under the black plastic mulch than under the white plastic mulch. These warmer temperatures may have been beneficial, especially since the plants were set later than generally recommended. Plants grown on white plastic mulch tended to produce larger berries than plants grown on black plastic mulch. Plants grown on the treatment of white plastic mulch that never received row cover produced larger berries than plants grown under any other treatment combination. Plants on the black plastic mulch produced more berries, therefore those plants might have benefitted from additional N to maintain fruit size.

Plants grown on black plastic mulch that received row cover in January produced fruit first (Figure 1). The plants grown on black plastic mulch receiving row cover in March were 3 to 5 days later in maturity, while the plants grown on black plastic mulch that were never covered were 6 to 8 days later in maturity. The plants grown on the white plastic mulch showed a similar pattern of maturity. However, the plants on white plastic mulch were also 2 to 3 days later in maturity than plants on black plastic mulch receiving the same row cover treatment.

The berries harvested from plants grown on black plastic mulch receiving row cover in January were larger at first harvest than berries from plants grown using any other treatment combination (Figure 2). Berries from plants grown on black or white plastic mulch without cover and white plastic mulch receiving cover in March tended to increase in size for the first 10 days, then begin to decrease in size. Berries from plants grown on the white plastic mulch without cover maintained better size over the course of the season. This may be related to the fact that these plants produced fewer total fruit, or that spring fertilizer applications were more timely for these later maturing plants.

It appears that the use of row covers and white plastic mulch could be used to spread the harvest season in annual plasticulture strawberry production. The use of row covers in conjunction with black plastic mulch could start production 1 week earlier than "normal". The use of white plastic mulch could delay maturity, extending the season a week later in the summer. However, the later maturing treatments also tended to concentrate their production into a shorter harvest window.

Table 1. Yield and average berry weight of ‘Chandler’ strawberries grown on black and white plastic mulch, with and without row covers at The University of Tennessee, Plateau Experiment Station, Crossville, 1999-2000.

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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.