Durner discusses supplemental lighting with strawberries
HERSHEY, Pa. — During the recent Mid-Atlantic Fruit and Vegetable Convention, Dr. Edward F. Durner, of Rutgers University, related his experiments with supplemental field lighting.
Using Albion strawberry plants this past season, he evaluated his alternative to greenhouse conditioning.
He explained that current recommendations for off-season long-day strawberry cultivar production is the use of dormant, cold-stored crowns planted directly in the field as early in spring as possible.
Planting before May 1 is a goal.
Wet and cold field conditions in the eastern United States often preclude early planting.
However, plugs can be produced in the greenhouse from dormant crowns, and then planted when the field conditions are more favorable.
Unfortunately, later planting typically reduces yields.
Durner noted that photoperiod and nitrogen conditioning may enhance flowering and off-season fall field production in long-day cultivars.
The level of success depends on plug size and the field planting date.
Elevated nitrogen during floral initiation enhances and accelerates flowering.
The response to conditioning is only four weeks afterward, and the cultivars respond with enhanced precocity and inflorescence with the elevated nitrogen.
Consequently, the yield reduction of later plantings, such as July 22, can be alleviated with photoperiod and nitrogen conditioning.
However, earlier plantings, such as June 2 and June 22, do not benefit from conditioning.
While larger plugs are often more productive than smaller ones, fewer are produced per area.
Hence, smaller plugs are often used.
Also, smaller plugs of long-day cultivars are typically less precocious and productive due to a short-day response that is imposed by the higher plant density during propagation.
But conditioning will enhance smaller plug precocity and early fall production.
Durner’s greenhouse conditioning alternative trial last season showed promise.
He supplemented field lighting in an Albion patch with inexpensive holiday light strings.
That approach eliminated greenhouse plug production with concomitant conditioning with photoperiod and nitrogen. (The ‘plugs’ are actually potted dormant crowns).
The plants were lit with the supplemental light strings daily for 15 minutes every hour from 7 p.m. to 7 a.m. for 28 days in July or for 28 days in August.
Flowering and fruiting were measured to determine whether either or both treatments enhanced long-day flowering.
The supplemental lighting did enhance both flowering and fruiting.
Durner indicated he would provide growers with more details on this alternative conditioning approach if they were interested in trying it.
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