## 3 Results and Discussion  
Figure 4 illustrates the used LED lighting system, which is similar to the design of the street light, and presents an aerial photograph of the water bamboo field with the LED light switched on. Obvious  
Figure 3: New design of the LED module with different arrangements of red and blue LED bulbs, and the schematic of measurement of the red and blue light intensity corresponding to the distance. The ratio of red to blue LED bulbs inside the LED modules was 6:1. Figure 2: (a) LED lamp module and blue (\(\lambda_{\text{peak}}=460\) nm) and red (\(\lambda_{\text{peak}}=670\) nm) LED light spectrum. (b) Schematic of the area and observation section of the water bamboo field. color difference between the LED (pink area) and HPS (yellow) light exposure area can be observed. The farmers previously used two HPS lamps to prevent stunting disease, and we used eight LED lamps in the same field. Moreover, according to the farmers, the use of HPS lamp can indirectly damage the frog habitat and possibly other species present near the field because of its strong and shining light. The possible adverse effect of LEDs on the environment is under investigation. To evaluate the relationship between light intensity and growth of bamboo leaves, we measured the height of water bamboo leaves every week. Figure 5a presents the growth of water bamboo leaves measured after exposure to our LED lighting system for two weeks during the night. The exposure time during the night was approximately 10 hours. Several observation spots, namely A1, A5, A6, C1, D1, E1, F1, C6, D6, E6, and F6, near the ridge exhibited a slow growth rate. The coverage measurement of LEDs was completed using a spectrometer, and the results are shown in Figure 5b. Here, we used the unit of lux to represent the measuring of luminous flux (lum) per unit area (1 lux = 1 lum/m\({}^{2}\)). Different colors indicate different light intensity, and the corner area indicates weak light intensity. In the field, 80% of water bamboo received sufficient LED light exposure (the area corresponding to the value >5). However, the area with the value <5 might possibly experience stunting. To resolve the problem of the inhomogeneous coverage of the LED light, we used two LED lens designs, one was a 136 \(\times\) 78 LED lens design and the other was a 60 \(\times\) 60 LED lens design. The numbers represent the distribution patterns of the LED light. Figure 6a illustrates the distribution pattern of the 136 \(\times\) 78 lens design. Figure 6b presents the real measurement of light distribution in the direction vertical to the LED light module. The light intensity decreased with an increase in the distance. Studies have reported that the blue and red light exhibit the major wavelengths for the growth of plants. The use of the correct equipment to measure the LED light intensity is essential for determining the sufficient amount of the artificial light, especially LED light, for plant growth. Figure 6c presents the vertical distance dependent on the blue and red LED intensity in the unit of photosynthetic photon flux density (PPFD). Furthermore, the PPFD value measured using the blue and red LED light decreased with an increase in the distance and reached a value of 0.2 PPFD for the blue LED light at a vertical distance of 8 m. Figure 6d presents the distance-dependent light intensity in the PPFD unit measured in the horizontal direction. The light intensity decreased with increasing distance; however, in the horizontal direction, the coverage of LED light increased with an increase in the distance. The horizontal coverage changed from 5 to 7 m when the vertical distance  
Figure 4: (**a**) Zoom-in image of LED lamp constructed near the ridge. (**b**) Water bamboo field with eight LED lamps switched on. The HPS lamps were used in the other field. Inhomogeneity of light coverage was observed in both fields.