Development of a water flow and nutrients concentration simulation model for cascade hydroponic systems

In a cascade hydroponic (CasH) system, the used nutrient solution drained from a primary crop is directed to a secondary crop, enhancing resource-use efficiency while minimising waste. Nevertheless, the inevitably increased EC of the drain solution requires salinity-tolerant crops. However, one of the biggest challenges in this case in recycling the drain solution in those systems is the estimation of nutrients concentration in the drain nutrient solution at each stage of the cascade system, and the salinity management in the system. Monitoring nutrients concentration in the nutrient solution, at frequent intervals and at various positions is an option but it requires a significant number of samples to be analyzed. To facilitate the practical application of drain nutrient solution management, a simulation model of nutrients concentration in a cascade system has been developed. The system has been built to simulate the nutrient flow in a series of three crops: a primary, a secondary and a tertiary crop. The drain nutrient solution from the primary crop is used to fertigate the secondary crop while the drain solution from the secondary crop is used to fertigate the tertiary crop. After validation, the model will be used for different case studies of cascade crops. This work presents the development of the model and makes a preliminary presentation of a case study with tomato used as primary crop and parsley as secondary crop. The model allows the use of different amount of drain solution mixed with fresh solution or water in order to cover the actual needs of each crop. Based on the scenarios considered, the nutrients concentration at the different system positions were studied.