Producing strawberries in high tunnels has been researched, by fall planting and following the annual plasticulture system. Yield increases over field plantings was modest (typically 25%) and being 2-3 weeks earlier. A significant detraction to this system is the length of time the crop is in the ground, 8 or 9 months.
A research program at Kansas State University tried a different approach, just outside of KC (Olathe Horticulture Research and Extension Center). Day neutral cultivars were planted early in the spring and fruited through the summer. The research yielded some potential, which this article will summarize. Cary Rivard* is a professor at KSU and the lead researcher was Kelly Gude**.
A prior study had indicated that day neutral strawberries could be profitable if yields of 0.75 to 1.25 pounds per plant were achieved at a market price of $2-4 per pound. This study occurred with high tunnel trials during 2014 and 2015 using six cultivars: Albion, Evie 2, Monterey, Portola, San Andreas, and Seascape (Nourse Farms, South Deerfield, MA). They were planted with bare root plants in early to mid-April (earlier would be OK, but obtaining the plants can be an issue). Beds were spaced 5 foot apart and there were two rows per bed, one foot between rows and the plants spaced one foot apart (staggered). A typical 30 x 100 ft high tunnel would have 1200 plants. A yield goal of 1 lb per plant at $3 per pound would return $3600. Not the return possible with tomatoes, but a potential alternative to give a high tunnel and its soil a break from tomatoes.
Pre-plant fertilizer was 30lb/N acre and plants were fertigated 9 or 10 times. Shade cloth (30%) was applied in mid-May. Evaporative cooling was used with sprinklers on some plots for about the hottest two months, whenever temperatures reached 85 F, in which the plants were sprinkled for 5 minutes. The mature fruit (90% to 100% red) was harvested twice weekly for total and marketable (fruit with no defects) fruit yield. The plants flushed with production into early, mid and late season periods, typically being May/June, July to mid-August, and mid-August to early October, respectively. Total yield was 1 pound per plant in 2014 and ¾ pound per plant in 2015. (A later planting in 2015 was cited as a likely factor, and March planting should be considered if planting material is available. Additionally, the 2014 plants were first put in plug trays with potting mix, as the ground was still froze. By the time they were planted they had rooted in and leafed out; this 'jump start' may have benefitted the yield.).
Marketable fruit was 80 to 89%. The mid-season yields were greatest and early or late season yields varied with cultivar, but were similar when averaged. Largest berry size was in early season. Evaporative cooling had no measurable benefit. The top three cultivars both years were Portola, Evie 2, and Seascape. Typical berry size was 10 grams (45 berries per pound). Sweetness was assessed (Brix), but was not presented in the research report (HortTechnology, April 2018). Contact James Quinn if you would like the complete report.
* Associate Professor, Extension Specialist & Director of K-State Research & Extension Center, Olathe.
** Article reviewed by Kelly Gude.
REVISED: February 21, 2017