Modeling Yield of 'Chandler' and 'Camarosa' as a Function of Accumulated Fall Growing Degree Days and Practical Row Cover Intervention Strategies

Floating row covers have been used by strawberry growers across the Eastern United States to moderate microclimate conditions to buffer environmental extremes.  Frost and freeze protection have been common uses to provide modest protection of flowers during bloom and protect crown tissue from winter injury in colder climates. Recently, interest in using row covers to enhance fall, plant growth and development have increased to allow producers in the mid-south to grow cultivars that are less adapted to regional climate although possess superior fruit quality (appearance and firmness).  Planting date is one of the primary factors that influence yield and productivity of plasticulture strawberries; however, growers often experience yield fluctuations with 'Camarosa' despite planting on optimum dates. Conversely, 'Chandler' tends to reliably produce adequate yields across diverse years and locations. An analysis of the past 10 years of North Carolina’s yield statistics in conjunction with meteorological data, demonstrated that a significant amount of variation (63%) in yields could be explained by the average fall growing conditions across the state. This modeling approach corroborated previous research conducted in the late 1990s in the Tidewater region of North Carolina which reported significant economic benefits associated with an early November row cover application during the first 2 weeks of November.  However, recommendations for fall row cover strategies based on the crop’s temperature requirements to accomplish yield optimization and stabilization were lacking.  For the last 3 strawberry seasons we have explored the potential of utilizing floating row covers to enhance floral initiation and differentiation in the late fall in three diverse locations in North Carolina (Mountains, Piedmont, and Coastal Plain). Strawberry cultivars, Chandler and Camarosa, were treated with various planting dates and row cover application treatments based on daily high temperatures (18°C, 15°C, 12°C and untreated controls) within each location.  Our results show that fall applications before temperatures dropped below an average daily high of 18°F can result in a 14% increase in yield compared to the uncovered treatments. The row cover by planting date interaction showed that all 3 planting dates responded positively to early applications and produced an average increase in yield of 16% or 3,360 kg/ha.  We have developed a model that describes the yield of 'Chandler' and 'Camarosa' as a function of accumulated heat units during the fall growing period.  This model can be used to help guide when and if row cover deployment is necessary to achieve maximum yield potential.