Location: Adaptive Cropping Systems LaboratoryTitle: Relationship of strawberry yield factors with microclimate under open and covered raised-bed production
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2017
Publication Date: 11/1/2017
Citation: Condori, B., Fleisher, D.H., Lewers, K.S. 2017. Relationship of strawberry yield factors with microclimate under open and covered raised-bed production. Transactions of the ASABE. 60(5):511-1525.
Interpretive Summary: Strawberries are economically valuable to farmers and are so popular with consumers that they expect to be able to buy strawberries all year long. In much of the US, traditional strawberries produce fruit only three to four weeks a year. To produce strawberry fruit for several months, farmers need to use a different kind of repeat-fruiting strawberry variety that fruits nearly all year long, and they need to grow them in a novel way that helps protect them from mid-summer outdoor conditions. Repeat-fruiting strawberries were grown in fields in two similar but slightly different ways (in raised beds and in raised beds under low tunnels) that were used to determine how day length, brightness, soil moisture, humidity and temperature affected strawberry yield. Higher temperatures found under low tunnels, especially in early spring and late fall, were responsible for much longer harvest seasons. Strawberry yield increased as light increased. They also increased with warmer temperatures up to about 28 degrees-Celsius, above which yields dropped due to excessive heat. A mathematical model was used to describe this relationship and showed that yields were more strongly associated with soil, as opposed to air temperatures. Growers will benefit from finding ways to keep the soil in the raised beds cool and maximizing the amount of light. This information will be useful to strawberry farmers and to scientists studying ways to help farmers increase the length of the strawberry season to match consumer demand.
Technical Abstract: The fresh strawberry (Fragaria ×ananassa Duchesne ex Rozier) market in the United States (U.S.) Mid-Atlantic region is primarily dependent on production from just two states. Local production is limited to a single cultivar and a three to five week harvest window and is insufficient to meet the region’s demand during periods of low yields from other locations. The adoption of repeat-fruiting cultivars may address these issues, but production systems suited to meet their cultural needs must be evaluated. The relationship between yields from five repeat-fruiting genotypes grown in either uncovered (open) or plastic covered (tunnel) raised bed systems and associated micro-climate factors was assessed from data collected over a three year period at the USDA-ARS facilities in Beltsville, Maryland. Average in-season yields were 40 percent, and berry numbers 150 percent, higher for production in tunnel versus open beds when averaged across all genotypes, years, and harvests. This yield difference was attributed to warmer temperatures (T) in the tunnel system that enabled extension of growing seasons, and higher light use efficiency. T and solar radiation accounted for over 41 percent of the variance between yield and all measured micro-climatic factors across all genotypes. Differences between tunnel and open systems for maximum 24-h temperatures averaged 3.5, 1.6, and 0.8 degrees-Celsius higher at air, crown, and bed positions, and daily photosynthetically active radiation was 34 percent lower. A 4-week period between floral initiation and fruit maturity was estimated as representative of the floral development period and used as a basis for obtaining cardinal temperatures at air (Ta), crown (Tc), and bed (Tb) positions. The optimum T averaged 26.8, 28.6, and 27.9 degrees-Celsius at the Ta, Tc, and Tb respectively. Yields were positively correlated with daily light integral below this T threshold, and higher slopes were observed for tunnel production. This relationship was shown to apply equally well to open and tunnel system production, especially when data at the crown position were used, and can be utilized for production system design and subsequent management during the growing season.