Jayesh B. Samtani, Hampton Roads Agricultural Research and Extension Center, School of Plant and Environmental Sciences, Virginia Tech

During the spring season, when the strawberry plants are in bloom and fruit, we occasionally hear some growers put down foliar nutrients to increase fruit sugar content using overhead spray nozzles. At the berry trade shows, we also encounter company representatives who support the use of supplementary nutrient products. However, there is no scientific information to support this practice for our climatic conditions and for our region that shows foliar nutrients are an important practice of increasing fruit yield or improving fruit quality parameters. To assist with answering this question, a field study was conducted over two growing seasons in a randomized, replicated design at the Hampton Roads Agricultural Research and Extension Center in Virginia Beach, VA. The objective of this study was to evaluate the effect of supplementary nutrients, in addition to standard fertigation practices, on fruit yield and quality for annual plasticulture strawberry production. First season treatments in the 2015-16 growing season included i) a root applied secondary macro and micronutrient mix (0-0-0) + foliar applied nutrient (6-4-3) ii) foliar applied nutrient (6-4-3) and iii) nontreated control. Additional treatments in the 2017-18 growing season included root applied micronutrient mix alone, and a foliar nutrient application of an OMRI certified cold processed sweetener. Treatments were replicated four times using ‘Chandler’ strawberry. Plugs in the root applied treatment were lightly dusted with the nutrient powder just prior to transplanting (Photo 1). Foliar nutrient was first sprayed at 30% bloom and every 7 to 14 days as frequent harvesting began using a three or two nozzle boom back-pack sprayer pressurized with CO2 gas. In the study, we found there were no significant differences among treatments for yield, fruit size, firmness or total soluble solids content. Based on our limited treatments and on a single strawberry variety, we do not recommend the use of supplementary foliar nutrients to growers without a good justification for making these applications. The leaf tissue sampling in spring and early summer will be a more reliable indicator for determining plant nutrient needs. Targeted application of specific macronutrients such as Calcium or Boron may be more effective based on the nutrient status of the plant as determined by reports of the plant tissue analysis. I also recently heard from a grower that he opted for the foliar nutrient application because the soils were too wet and he was afraid of promoting root rot conditions by injecting liquid fertilizers through drip application. Instantly I agreed with the grower that this might be a practice to adopt into strawberry production, in situations where field conditions remain wet for extended periods of time in the spring season.

Photo 1: Plugs in the root applied treatment were lightly dusted with the nutrient powder just prior to transplanting.
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