Influence of low tunnels on strawberry production time and yield

This study was undertaken to force strawberry production season using low tunnels. The experiment was established at the Pure Horticultural Research Centre, Latvia (57°02'N; 22°52'E). Two types of tunnels were evaluated: 0.5 m high and 0.8 m wide tunnel with one layer of polyethylene film (150 µ) cover and 0.65 m high and 1.0 m wide tunnel with two layers of covers, where the upper layer was polyethylene film (150 µ) and lower layer was perforated film (40 µ, 500 holes m^-2). Two cultivars: 'Honeoye' and 'Darselect', were used in the trial. Plants were grown on two row beds mulched with black plastic. Drip irrigation was applied. The plant density was 3.9 plants m^-2. Covers were installed every year at beginning of vegetation and removed at the beginning of fruit harvesting. Split block design in four replicates was used in the trial. The evaluation was done for two growing seasons. Strawberry harvesting time, yield, fruit quality, spreading of pests and diseases were evaluated. The temperature on soil surface and in 15 cm depth was measured. The strawberry harvesting season was forced for 10 days when low tunnels were used in comparison to growing without covers. Both types of evaluated tunnels increased the amount of early yield and percentage of E and Class 1 fruits, but had no influence on total yield. However, the average fruit weight was lower in treatments with tunnels. Cultivar 'Honeoye' was more suitable for growing in low tunnels than cultivar 'Darselect' as it had earlier harvesting season, higher yield and better resistance to fruit rots.