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Strawberry Fields Forever

Posted Jul. 31, 1999

In Oklahoma, strawberries have traditionally been a popular fruit for fresh use and freezing. Unfortunately, local production of this crop meets only a small percentage of this consumption.

Currently, the majority of production in Oklahoma consists of matted row culture. The matted row system consists of rows 12 to 24 inches wide that are allowed to fill in or be renewed with runner plants. Traditionally, plantings are established in the early spring. Flowers are removed the year of planting to allow plants to use food reserves for top and root growth. In the matted row system, growers strive for three to four profitable crops from a single planting.

The annual system is a high-density system that grows strawberries as annuals. This planting consists of closely spaced plants in double or triple rows planted on raised beds covered with black plastic mulch and equipped with drip irrigation. Freshly dug plants or plugs (small container grown plants) are planted in late summer and removed after spring harvest.

The advantages of plasticulture are uniform plant stands unaffected by summer diseases, drought or weed competition; earlier fruit harvest; larger berry size; and shorter turnaround time from planting through harvest (eight months). One acre of strawberry plasticulture can produce the equivalent of 2.5 acres of matted row production. The disadvantages of the plasticulture system include higher initial cost and greater management skill.

To demonstrate the potential of strawberry plasticulture, we established a 30-ft. by 60-ft. plot of "Allstar" strawberry plants during late summer of 1998 at our Headquarters Farm Horticulture Center. The plot consisted of 12 40-inch by 30-ft. permanent beds on 5-ft. centers. Prior to planting, all beds received a preplant fertilizer treatment based on a soil test. After installing drip irrigation, each was covered with 1.25-mil. black plastic mulch. On September 14, holes were cut in the mulch with the end of a bulb planter. Strawberry plug transplants were set in beds on a 12-inch by 12-inch spacing, three rows per bed, for a total plant population of 1,080.

Due to extremely high temperature at planting, the plot was sprinkle irrigated three to four times a day for several weeks. These 15-20 minute waterings proved effective in cooling plastic and reducing the amount of wilting.

The first of many weekly nitrogen fertigations (application of fertilizer via the irrigation system) occurred September 29. Nitrogen (N) was applied in the form of 34-0-0 or 21-0-0 at the rate of 8 lbs. N/acre. The final fertigation of 1998 occurred November 24.

One of the advantages of growing on black plastic mulch is the growth-enhancing characteristic it provides due to soil warming. This was clearly evident during the month of November as plants continued to grow rapidly despite cooler air temperatures. This additional fall growth translates into greater yield potential the following spring.

Sporadic death of the outer (older) leaves occurred as the result of freezing temperatures during the first two weeks of 1999. These low temperatures, some in the teens, did not appear to adversely affect flowering and fruiting.

Plants initiated flowering around the first of March. A freeze event on March 15 resulted in some early fruit loss in addition to a high incidence of malformed fruit.

Fertigation was reinitiated on March 16 and continued through harvest. Irrigation scheduling was based on irrometer readings.

Harvest began April 9 and concluded May 21. Peak harvest occurred on April 30. A total of 1,282 lbs. of berries were harvested from the 1,800 square feet. Unfortunately only 63%, 807 lbs. (3/4lb./plant), were judged marketable. Marketable fruit weight averaged 0.36 oz/berry. Thirty-seven percent (475 lbs.) of fruit were culled, primarily due to small size.

Noble Research Institute employees who helped harvest the crop were favorably impressed with the appearance and flavor of the crop. The only negative comment pertained to berry size. No doubt consumers have grown accustomed to the large California berries common to supermarket produce sections.

Prices obtained by growers will vary depending on marketing method and availability. Early season berries sold at a local farmers market brought as much as $3.50/lb during the month of April. One local grower consistently sold his "pick-your-own" crop for $2.00/lb.

Based on this initial trial, we are very encouraged with the potential of strawberry plasticulture in the Oklahoma-Texas region. Obviously, additional varieties need to be screened for their adaptability to our climate. Growers in North Carolina are consistently obtaining marketable yields equivalent to 1 lb./plant growing the variety "Chandler." This variety along with others developed specifically for plasticulture will be evaluated at a later date. Another short-term objective will be to develop a budget for a small-scale commercial strawberry enterprise utilizing a tractorpowered bedder and plastic mulch layer.

Enough chit-chat! It's lunch time and we're having strawberries and cream for dessert. See you later.

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