DETERMINATION OF TEMPERATURE INCREASE AND LETTUCE (LACTUCA SATIVA L-DUNA) YIELD IN LOW TUNNELS WITH DIFFERENT PLASTIC COVER MATERIALS INSTALLED IN HIGH-TUNNEL

Low tunnels installed in high tunnels are preferred by producers in winter conditions for earliness, yield increase and increase of root quality. The objective of this study was to determine yield and quality parameters, temperature changes inside high and low tunnels as well as root zone temperature changes, solar radiation changes inside the tunnel. The experimental site was located at the University of Suleyman Demirel in Isparta, Turkey. It was conducted from 28 October to 28 January, 2015-2016. Three different polyethylene cover materials and control parcel have been tested. The lettuce (Lactuca sativa L. Duna) crop was transplanted before tunnel installed. The yield, quality and leaf nutrient contents of the harvested plants were examined. The light transmittance of the newly tested bubble cover material is lower in comparison with the traditional cover material. High tunnel temperatures were measured lower in comparison with outdoor temperature values at night, however; temperature values inside the low tunnels were measured higher than outdoor temperatures at night time. High tunnel soil temperature was measured to be about 5 degrees C higher than the outdoor environment especially in January, while the low tunnel root zone temperature values were measured to be about 7.5 degrees C higher. About 3 times greater yield increase was attained in low tunnel cultivation in comparison with high tunnel cultivation. It was determined as a result of the examination of tunnel and root zone temperature values that the newly tested applications (Big bubble, Small bubble) generally yielded successful results in the study.