Time based changings on some physical and mechanical properties of different polyethylene coverings used as greenhouse covering material and ligth transmittance effect on crop growing under Antalya conditions

In this study, some physical and mechanical properties changings during the useful life of greenhouse covering materials for 24 months produced by CO-EX technology with multi-layered CO-EX UV+IR+EVA and UV+IR+EVA+AF additives was investigated and the effect of light transmissions on crop growing. This experiment was conducted at Akdeniz University Agricultural Faculty Research and Application Field during the time of 2011-2013 years. Four model greenhouses which has 20 m2 (4x5 m) floor area were used. As physical properties, global radiation and photosynthetically active radiation (PAR) transmittance of greenhouse covering materials were determined. Two different greenhouse covering materials were examined with two replications as four model greenhouses from November 2011 to November 2013. 06:00-18:00 time period in five open sky days was considered for determination of greenhouse covering materials global radiation and photosynthetically active radiation (PAR) transmittance as monthly. Global radiation and PAR transmittance of plastic films were determined by inside and outside radiation ratio. Greenhouse covering material mechanical specifications such as impact resistance, tensile strength and elongation at break were determined according to TSE standarts in the labortory of IMECE Plastic Inc.. Tomato growing was realized during 2 years (2011-2012 and 2012-1013 fall and spring seasons) for determining the effect of global radiation tranmittance on crop growing. Daily mean global radiation (W m-2) received by crops were determined during each growing period. Furthermore, crops were selected in each greenhouse as 6 replicated and the crops were monitored 15 days intervals. Vegetative growing parameters (crop height, body thickness, leaf number), yield and fruit quality parameters (average fruit weight and size, EC and pH of fruit juice, water soluble dry matter) were measured. In this research, greenhouse environment conditions were also investigated. The temperature and relative humidity were measured along 24 hours at selected open sky days for global radiation and PAR measurements. Initial global radiation transmittance of CO-EX UV+IR+EVA added PE and CO-EX UV+IR+EVA+AF added PE greenhouse covering materials were determined as 92.7% and 83.6%, respectively. The plastic films of type UV+IR+EVA and UV+IR+EVA+AF had losses of global radiation transmission of 7.3 % and 13.2 % at the end of the useful life, respectively. Initial PAR transmittance of CO-EX UV+IR+EVA added PE and CO-EX UV+IR+EVA+AF added PE greenhouse covering materials were determined as 80.1% and 83%, respectively. The plastic films of type UV+IR+EVA and UV+IR+EVA+AF had losses of PAR transmission of 11.2 % and 14.0 % at the end of useful life, respectively. Initial impact resistance of CO-EX UV+IR+EVA added PE and CO-EX UV+IR+EVA+AF added PE greenhouse covering materials were determined as 1161.4 g and 1164.1 g, respectively. These values were determined as 632.5 g and 713.0 g after 24 months. As a result, impact resistance of the plastic films reduced as 45.5 % and 38.8 %, respectively. Initial tensile strength at machine direction (MD) of CO-EX UV+IR+EVA added PE and CO-EX UV+IR+EVA+AF added PE greenhouse covering materials were determined as 21.2 N mm-2 and 18.9 N mm-2, respectively. These values were determined as 20.5 N mm-2 and 17.3 N mm-2 after 24 months. As a result, tensile strength at MD of the plastic films reduced as 3.3 % and 8.5 %, respectively. Initial tensile strength at transverse direction (TD) of CO-EX UV+IR+EVA added PE and CO-EX UV+IR+EVA+AF added PE greenhouse covering materials were measured as 17.6 N mm-2 and 20.7 N mm-2, respectively. These values were determined as 16.9 N mm-2 and 16.7 N mm-2 after 24 months. As a result, tensile strength at TD of the plastic films reduced as 4.0 % and 19.3 %, respectively. Greenhouses inside and outside temperatures and relative humidiy values were changed in suitable levels for crop growing during experiment. CO-EX UV+IR+EVA and UV+IR+EVA+AF added PE films global radiation tranmittance did not effect on vegetative growing, yield and fruit quality as statistically.