# Smart Hydroponic Cultivation System for Lettuce
## 2 Materials and Methods
### Monitoring and Control System
Figure 11 shows the daily behavior of air temperature and RH throughout the experiment. The air temperature averaged \(23\pm 3\)\({}^{\circ}\)C, while the RH averaged \(65\pm 5\%\)HR. Figure 11: Daily behavior of air temperature and RH recorded inside the plant growth chamber using the smart agriculture system during the cultivation experiment. Figure 10: (**a**) Responsive web application that enables real-time monitoring through intuitive graphics. (**b**) Android mobile application with the same functionality, optimized for small-screen devices. The behavior of \(CO_{2}\) within the plant growth chamber is shown in Figure 5:0 The daily average concentration was approximately 347 ppm, which is lower than the expected ambient average of 420 ppm [43]. This difference is attributed to the photosynthetic activity of the plants within the enclosed environment. The presence of users inside the growth chamber influences \(CO_{2}\) concentration due to human respiration. Days with higher human activity correlate with elevated values in the graph, demonstrating a direct impact of human presence on the controlled environment. ### Video Monitoring

The combination of control technologies and IoT-based environmental monitoring, along with the video surveillance system within the plant growth chamber, provides comprehensive oversight of the cultivation environment. This enhances security, improves response efficiency in case of system failures and ultimately drives higher productivity and sustainability. Figure 13 presents a view of the implemented video monitoring system, displaying the operational status of the full-spectrum LED lamps and the condition of the hydroponic channels. Figure 5:1 Average daily behavior of \(CO_{2}\) levels recorded inside the plant growth chamber using the smart agriculture system during the cultivation experiment. Figure 5:2 View of the surveillance camera implemented inside the plant growth chamber. The image shows the operational state of the full-spectrum LED lamps and the condition of the NFT hydroponic channels with plants in the development phase. ### Case Study Results: Nutrient Solution Behavior

Figure 14 illustrates the behavior of the physicochemical variables measured during the experiment. The pH level remained between 5.4 and 6.6 across the three treatments, averaging 6.11 for T100, 6.04 for T75 and 6.14 for T50. The average EC for T100 during the experiment was 2003.84 \(\upmu\)S cm\({}^{-1}\), ranging between 1850 and 2300 \(\upmu\)S cm\({}^{-1}\); for T75, the average conductivity was 1589.15 \(\upmu\)S cm\({}^{-1}\) fluctuating between 1399 and 1740 \(\upmu\)S cm\({}^{-1}\); finally, T50 had an average conductivity of 1195.46 \(\upmu\)S cm\({}^{-1}\), with a minimum value of 1039 \(\upmu\)S cm\({}^{-1}\) and a maximum of 1286 \(\upmu\)S cm\({}^{-1}\). Since the experiment was conducted in a controlled environment, the recorded temperature of the nutrient solution showed very similar behavior across the three treatments throughout the experiment. ### Case Study Results: Statistical Analysis of Lettuce Phenotypic Variables

Lettuce is one of the most important vegetables grown in protected agriculture and is consumed in large quantities worldwide in salad preparation due to its phytontrient content, which provides health benefits for humans [44]. For this reason, various technologies have been developed to monitor its growth under different cultivation techniques [45]. The combination of the controlled-environment chamber and the implemented NFT hydroponic technique resulted in a positive effect on the development of the harvested lettuces, as shown in Figure 5:3 This figure illustrates the cultivation experiment three days before harvest, revealing that the lettuces grown across all three treatments exhibited uniform growth. Table 3 presents the results obtained from the lettuce cultivation experiment.