# Smart Hydroponic Cultivation System for Lettuce
## 1 Introduction  
Agriculture is the set of human practices aimed at producing food, forage, fiber and other useful products through the management of plants and animals [1]. In a global context where the population exceeds 8 billion people and is projected to increase by another 2 billion by 2050, the United Nations [2] estimates that food production will need toincrease by 70%. This challenge requires a transformation in production and consumption methods, prioritizing sustainable agricultural practices that balance food demand with environmental conservation. Protected agriculture refers to the action of placing structures to protect crops, with the aim of obtaining a higher-quality harvest in less time or out of season [3]. Various techniques are used in this type of agriculture, including hydroponics. The Nutrient Film Technique (NFT) is a soilless hydroponic cultivation method that uses inclined structures through which a thin and continuous flow of nutrient solution circulates [4]. This technique ensures that plant roots are consistently exposed to both nutrients and oxygen, promoting efficient absorption [5]. NFT is notable for its high water and nutrient use efficiency compared to other hydroponic techniques [6], as well as its adaptability to controlled environments, enabling year-round crop production [7]. Several studies have shown that this technique can accelerate plant growth by 10% to 50% compared to traditional agricultural practices [8]. However, NFT presents limitations, such as vulnerability to power outages, unsuitability for long-cycle crops (longer than 50 days) and a high risk of rapid spread of root diseases [9]. Indoor agriculture, also known as indoor farming, takes place in spaces with regulated environmental conditions, where factors like air temperature can be adjusted. Sunlight is replaced by artificial illumination systems. A controlled environment with artificial light is called a plant factory, growth chamber or plant production unit [10]. The advantages of these systems are clear, as technological advancements allow crops to be produced year-round without relying on climate patterns [11]. Currently, the most common crops in these systems include leafy vegetables (lettuce, spinach, etc. ), tomatoes, cucumbers, berries and microgreens [12]. On the other hand, the Internet of Things (IoT) is a revolutionary technology that enables the interconnections between physical objects and the Internet, establishing continuous interaction between them [13]. In agriculture, the IoT refers to the integration of sensors, embedded devices, communication networks and digital platforms that allow for real-time data collection, analysis and monitoring. This enables automated control of various processes such as irrigation and fertilization, as well as data-driven decision-making, allowing for faster and more effective responses to adverse events, reducing resource waste and optimizing productivity [14]. However, the impact of IoT depends on proper implementation, technical feasibility and financial accessibility for end users [15]. Smart agriculture is based on the application of modern technologies to improve both the quantity and quality of the crops. This approach includes the use of tools such as IoT, databases, machine learning, cloud processing, machine-to-machine communication protocols, sensors, actuators and personal devices like phones and computers [16]. In [17], a smart agriculture framework is described as consisting of six layers. The first layer, or physical layer, contains a set of sensors, actuators and microcontrollers that collect and process data among the devices themselves. The second layer, or network layer, includes the Internet, Wi-Fi connections and wireless communication between devices. The third layer, or intermediate layer, is responsible for device management on the network, platform portability, security and authentication. The fourth layer, or service layer, provides cloud storage and software as a service for data management.