# HydroLab: A Module for the Investigation of Fertigation Strategies in Hydroponics
## 3 HydroLab
### HydroLab Architecture  
In this section, the framework previously illustrated is instantiated through implementation technologies. Furthermore, its sensors and control architecture are presented. The objective of HydroLab is to develop fertigation strategies for hydroponics. In order to facilitate statistical analysis, the same strategy is applied to groups of crops. The module consists of two rows of plants, with each row containing eight plants (Figure 2). However, it may be scaled up to accommodate larger crop groups. On each row, two slabs with substrates are positioned on an inverted gutter structure equipped with lateral drain channels, as illustrated in Figure 3. The slope of the gutter is adjusted using suspensions to facilitate the drainage flow into a cistern located at the end of the structure. Each slab accommodates four plants, which are supplied with nutrients through spaghetti tubes connected to the main distribution line. Pressure compensating (PCJ CNL of 4 L/h) ([[https://www.netafim.com/en/products-and-solutions/product-offering/drip-irrigation-products/PCJ-online/](https://www.netafim.com/en/products-and-solutions/product-offering/drip-irrigation-products/PCJ-online/)]([https://www.netafim.com/en/products-and-solutions/product-offering/drip-irrigation-products/PCJ-online/](https://www.netafim.com/en/products-and-solutions/product-offering/drip-irrigation-products/PCJ-online/)) (accessed on 18 July 2023)) emitters are utilized to ensure precise and uniform irrigation for the plants [24]. These emitters include anti-draining features to prevent fluid leakage after pump shutdown, as well as self-compensating capabilities to maintain a consistent solution flow despite changes in line pressure. An SFDP1-011-070-21 ([[http://www.seaflo.com/en-us/product/detail/1070.html](http://www.seaflo.com/en-us/product/detail/1070.html)]([http://www.seaflo.com/en-us/product/detail/1070.html](http://www.seaflo.com/en-us/product/detail/1070.html)) (accessed on 18 July 2023)) diaphragm pump is used to deliver the nutrient solution to the emitters in conjunction with a solenoid valve. This pump is chosen for its ability to handle chemical solutions within the acceptable pH range of 5 to 10. Drops are injected into the substrate  
Figure 1: P&ID diagram of HydroLab: T320 denotes the nutrient solution tank, C300 denotes the air compressor, V410 and V420 denote the solenoid valves, P410 and P420 denote the diaphragm pumps, F410 and F420 denote the mesh filters, and T410 and T420 denote the two crop samples. using vertical stakes connected to the spaghetti tubes. Lastly, the EcoPlus HGC728459 ([[https://www.hawthornegc.com/shop/product/ecolplus-commercial-air-pumps](https://www.hawthornegc.com/shop/product/ecolplus-commercial-air-pumps)]([https://www.hawthornegc.com/shop/product/ecolplus-commercial-air-pumps](https://www.hawthornegc.com/shop/product/ecolplus-commercial-air-pumps)) (accessed on 18 July 2023)) compressor is employed to mix the solution before fertigation. The sensors and control architecture of HydroLab are depicted in Figure 4. These components support the decision-making process concerning fertigation and are integrated with Internet of Things (IoT) technologies to facilitate remote monitoring and control of the system. Various sensors can be strategically placed based on specific experimental requirements. In particular, a pyranometer is utilized, as the case study described in Section 4 involves a comparison between a time-based strategy and solar radiation-based fertigation strategy. However, further sensors can be installed in the future (such as capacitance probes) to test fertirrigation based on the VWC [25; 26]. Next, the different elements are illustrated.