Effect of led light application on mineral matter uptake, leaf nitrate and growth of plants (lettuce and pepper) in soilless agregate culture

This study was performed during early spring-summer and winter period of 2015-2016 by utilizing hydroponics technique in a non-heated glasshouse that belongs to Gaziosmanpaşa University Faculty of Agriculture. Whereas Funly F1 lettuce and Balca F1 pepper species were used as vegetal materials, 2:1 ratio cocopeat and perlite mixture was used as cultivation environment. According to the experiment design, experiment coincidence parcels were performed as 3-recurrences. In the experiment, the effects of different colored LED lights (blue, yellow, red, blue + yellow, blue + red, yellow + red, blue + yellow + red) additional to sunlight were examined. SMD strip LEDs with different colors were used as light source. The light practice does not affect on the plant diameter, plant lenght, SÇKM, pH, titered acid, vitamin C, and plant nutrient concentrations. Statistically significant difference occured in the yield of spring and winter curly leaf head salad. There was also an increase at 1% importance level in the light practices compared to the control. In the experiment, red and red blue light combinations had an increase of 1% in the curly leaf head salads and 5% in the pepper plants in the yield rate when it was compared to the control. Whereas the highest total plant head weight was 840 gr/piece in spring practice, and it was 732 gr/piece for the red light practices in winter practice. The highest total fruit yield for the pepper plant was 703.4 gr/plant in the blue light practice. Compared to the control, the amount of plant leaf nitrate for the light practices resulted in a decrease at 1% importance level in the curly leaf head salad and 5% in the pepper plant. When the results were compared with the control conditions, the lowest nitrate contents were obtained as 1764.5 mg NO3-kg- in spring practices, 1898.6 NO3-kg- in winter practices, and 75.4 NO3-kg- in pepper practices. More amount of nitrate was observed on the leaves of curly leaf head salad in winter practice compared to the one in spring. The amount of leaf nitrate decreased in the light practices compared to the control. As a result, the red and blue light practices and their combinations improved the amount of yield and plant growth by reducing nitrate content.