OPTIMIZING STRAWBERRY PRODUCTION AND FRUIT QUALITY WITH USE OF PROTECTED CULTURE IN SOUTHERN CALIFORNIA

In southern California, strawberry fruit produced from December to March has the greatest market value, but meteorological conditions during this period are often suboptimal for strawberry growth and fruiting. During a four-year period (2002-2005), we determined yield performance for ‘Camarosa’ and ‘Ventana’ cultivars using open field (OF) and protected culture (PC; i.e., Spanish tunnel) production. Tunnels were 3.7 m high, 4.9 m wide (covering three planting beds), and 24 or 36 m in length, and constructed with steel arcs attached to vertical Y-posts. Plastic films were placed over the tunnels at anthesis (late November) and sides were constantly open to a height of 1.2 m. Yield performance of plants grown on black and clear polyethylene bed mulches (PBM) was determined in both production systems, and PAR (photosynthetically active radiation), UV transmissivity and yield performance were compared using two different tunnel films. Compared to OF, the use of PC resulted in consistently greater ambient and soil temperatures, while relative humidity in PC was greater during the day but lower at night with no dew. In both systems, growth and yield were maximized with use of clear PBM due to higher soil temperatures. Early season yield (to March 15) varied by year, and was 1.7- to 1.9-fold greater for PC compared to OF. Total yield (to May 1 or June 1) varied by year and was 1.1- to 1.2-fold greater for PC compared to OF. One tunnel film blocked more UV and PAR than the other, but differences in yield and fruit quality between films were small and inconsistent. Compared to OF, PC resulted in enhanced early-season fruit quality (size, appearance), while late season PC fruit quality was maintained by removing tunnel covers by early March to avoid high temperatures. Results demonstrate that with proper management PC can result in increased yield and fruit quality in California strawberries.