# Smart Hydroponic Cultivation System for Lettuce
## 2 Materials and Methods
### Monitoring and Control System
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Treatment** & **Carbohydrates** & **Proteins** & **Fats** & **Humidity** & **Fiber** & **Ascorbic** & **Potassium** & **Phosphorus** & **Iron** & **Sodium** & **Magnesium** & **Zinc** \\  & **(g)** & **(g)** & **(g)** & **(g)** & **(g)** & **acid (ug)** & **(ug)** & **(ug)** & **(ug)** & **(ug)** & **(ug)** & **(ug)** \\ \hline T50 & 2.95 \(\pm\) 0.15 a & 0.59 \(\pm\) & 0.10 \(\pm\) & 96.36 \(\pm\) & 1.97 \(\pm\) & 9.97 \(\pm\) & 283.13 \(\pm\) & 22.00 \(\pm\) & 0.29 \(\pm\) & 5.71 \(\pm\) & 0.05 \(\pm\) \\  & 0.05 a & 0.01 a & 0.11 a & 0.04 a & 0.33 a & 48.9 a & 2.11 \(\pm\) & 0.07 a & 0.16 a & 0.06 a \\ \hline T75 & 3.02 \(\pm\) 0.09 a & 0.86 \(\pm\) & 0.13 \(\pm\) & 95.98 \(\pm\) & 2.18 \(\pm\) & 10.68 \(\pm\) & 242.64 \(\pm\) & 24.49 \(\pm\) & 0.34 \(\pm\) & 6.54 \(\pm\) & 11.01 \(\pm\) 0.50 a & 0.16 \(\pm\) \\  & 0.09 a & 0.02 a & 0.08 a & 0.09 a & 0.41 ab & 1.27 ab & 1.45 a & 0.07 a & 0.32 ab & 0.03 b \\ \hline T100 & 3.26 \(\pm\) 0.23 a & 1.29 \(\pm\) & 0.17 \(\pm\) & 95.27 \(\pm\) & 2.05 \(\pm\) & 11.01 \(\pm\) & 247.57 \(\pm\) & 28.83 \(\pm\) & 0.39 \(\pm\) & 6.77 \(\pm\) & 11.32 \(\pm\) 0.51 a & 0.26 \(\pm\) \\  & 0.20 b & 0.05 a & 0.44 b & 0.28 a & 0.22 b & 0.09 b & 0.10 b & 0.07 a & 0.51 b & 11.32 \(\pm\) 0.51 a & 0.03 c \\ \hline \hline \end{tabular} Different letters represent significant differences between treatments (\(p<0.05\)).

\end{table} 
Table 4: Means and standard deviations (\(\pm\)SD) of the biochemical variables per 100 g of lettuce obtained from the experimental treatments. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Nutrients** & **T50 (g)** & **T75 (g)** & **T100 (g)** & **Iceberg Lettuce USDA (g)** \\ \hline Carbohydrates & 2.95 & 3.02 & 3.26 & 3.37 \\ \hline Proteins & 0.59 & 0.86 & 1.29 & 0.74 \\ \hline Fats & 0.10 & 0.13 & 0.17 & 0.07 \\ \hline Moisture & 96.36 & 95.98 & 95.27 & 95.5 \\ \hline Fiber & 1.97 & 2.18 & 2.05 & 1.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Means of biochemical variables in 100 g of lettuce obtained in the experiment treatments. operation during the defined photoperiod. Hydraulic pumps, used to recirculate the nutrient solution, consumed 13% (1.78 kWh), while ultrasonic humidifiers represented the lowest energy consumption at 6% (0.83 kWh). On average, the system consumes 0.46 kWh per plant per day. To estimate daily energy costs, several factors must be considered such as geographical location, the type of contract with the electricity provider and the time of year. Based on the location of the system during the case study and referencing the current average residential electricity rate of $0.058 USD/kWh, the average daily energy cost for operating the proposed system was calculated at $0.80 USD, which corresponds to an approximate expenditure of $0.027 USD per plant. ## 4 Discussion

The purpose of a plant growth chamber is to create controlled environmental conditions that favor the growth and productivity of agricultural crops. Developing such structures requires appropriate infrastructure that ensures the maintenance of ideal conditions, as well as the implementation of an environmental monitoring and control system. In this project, the smart monitoring and control system proved effective by providing real-time data on environmental conditions, thus ensuring a favorable environment for the development of hydroponic crops. The implementation of the NFT hydroponic technique within the growth chamber proved beneficial for the year-round cultivation of lettuce, as it created favorable environmental conditions regardless of the season. This favored uniform plant growth, as no significant differences were observed in the phenotypic characteristics of the harvested lettuce, including chlorophyll content. However, the proximal analyses revealed significant differences between treatments, particularly in protein, Sodium, Potassium and Zinc content.