# HydroLab: A Module for the Investigation of Fertigation Strategies in Hydroponics
## 1 Introduction  
The agriculture industry currently faces a significant and unprecedented challenge: the efficient and timely production of food to meet the needs of a rapidly growing global population. According to the Food and Agriculture Organization (FAO) of the United Nations, the year 2050 is projected to be a pivotal year with profound global implications since the human population is anticipated to reach 9.73 billion individuals, with approximately 75% residing in urban areas [1]. Meeting the _nutritional demands_ of this growing population will require significant increases in food production, estimated at approximately 70% compared to 2007 levels [2]. These challenges are compounded by a variety of factors, including resource constraints, environmental concerns, and supply chain inefficiencies. The _Green Revolution_ is one of the most significant events in agriculture history, marked by a series of research, development, and technology transfer initiatives aimed at bolstering industrialized agricultural production [3]. These initiatives focused on cultivating high-yield crop varieties, expanding fertigation infrastructure, and disseminating hybrid seeds that exhibited enhanced productivity. However, intensified soil utilization and increased reliance on fertigation were crucial factors that posed some of the most pressing challenges to agriculture during this time [3]. While the initiatives addressed the immediate needs, they had adverse repercussions, such as soil degradation, salinization of irrigated areas, overexploitation of groundwater resources, deforestation, greenhouse gas emissions, the exacerbation of the greenhouse effect, and contamination of water bodies with nitrates [4]. The long-term consequences of these actions have become increasingly apparent in previous years and different approaches must be investigated toward food security. _Hydroponics_ has gained popularity as it represents an environmentally friendly option that offers higher crop yields and improved quality [5]. Studies have indicated that the global hydroponic market is projected to experience significant growth, with an anticipated annual growth rate of 20.7% from 2021 to 2028, reaching a value of 9.8 billion [6]. This agricultural practice eliminates the need for soil and holds promise as a viable solution to the challenges facing traditional agriculture [2]. In hydroponics, plants are cultivated in natural or artificial substrates that facilitate the efficient uptake of nutrients from a carefully prepared nutrient solution. This method can address issues related to substandard crop quality and quantity, soil contamination, and the limited availability of arable land and water resources in traditional agriculture [7]. Despite these benefits, hydroponics still faces significant challenges, such as the optimization of fertigation strategies [8], particularly when considering different crops, varieties, and growing conditions [9; 10]. _Fertigation_ involves the injection of fertilizers into an irrigation system and it is the most critical activity in hydroponics. For instance, a high salt content in the nutrient solution generates osmotic pressure values that prevent the absorption of nutrients, while low content affects plant growth and productivity [11]. In some cases, frequent fertigation may be necessary due to the restricted root volume of the plants [12], but too frequent fertigation increases the moisture content in the root zone, reducing the oxygen availability to plants [13]. Moreover, fertigation requirements vary based on numerous factors such as plant species, cultivar, growth stage, utilized substrate, season, and climate conditions. Due to the lack of standard knowledge and the complexity of the problem, test benches are fundamental for investigating effective fertigation strategies.