INCREASING WINTER STRAWBERRY PRODUCTION IN NORTH-CENTRAL FLORIDA USING PASSIVE VENTILATED GREENHOUSES AND HIGH PLANT DENSITIES

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Winter production of strawberry (Fragaria x ananassa Duch) under protected structures can give several advantages to producers over field production. The objective of this research was to determine how increasing plant densities (10.8, 11.7, 12.7, 14, 16.9, 18.3, 20, and 22 plants per m 2 ) of 'Sweet Charlie' strawberry grown in a passive ventilated greenhouse might improve yield Without adversely affecting fruit quality. Plant densities were derived with four between-row spacings (65, 60, 55, and 50 cm center-to-center) and two within-row spacings (17.5 cm and 35 cm plant-to-plant). Strawberry plants were grown in a 'Hanging Bed-Pack' trough system (Polygal Industries, Ramat Hashofet, Israel) that were suspended 1.8 m above the ground level and filled with 6.5 cm 2 sieved pinebark. Marketable yield per m 2 increased linearly with an increase in plant density throughout the season. Early yield per plant was not affected by plant density, however, total yield per plant decreased as plant density increased. Regardless of treatment, the average berry size for early and total yield was 20 g and more than 90 percent of the yield was marketable. A cost threshold was developed by comparing the value of higher early yields when prices are highest, to increased cost of plug transplants at high plant densities. A plant density of 16.9 plants per m 2 led to break-even yields while higher plant densities from 18.3 to 22 plants per m 2 led to increased profits. Thus, high plant populations were required to maximize profits from strawberries grown in passive ventilated greenhouses.