Development and evaluation of an automated system for fertigation control in soilless tomato production

• A closed loop control system is proposed to prepare and manage nutrient solutions.
• The control strategy synchronizes nutrient solution demand and supply to plants.
• The plant water stress is minimized under high atmospheric demand conditions.
• The control system is effective in controlling leachate electrical conductivity.
• The developed control system enhances economy of fertilizer and water resources.

An automatic control system was developed for real time preparation and application of nutrient solution for soilless tomato production. The control strategy was based on transpiration estimates by the Penman–Monteith model and on leachate concentration by measurements of electrical conductivity. The performance of the fertigation system was evaluated during tomato cultivation in sand substrate under greenhouse conditions. The commercial crop yield was 4.74 kg m−2 and the average total soluble solids of tomato fruits was 4.50 °Brix. Water use efficiency for tomato crop cultivated with the developed control system was 17.94 kg m−3. To produce 1 kg of tomato fruits, 44.42 L of nutrient solution were necessary. The proposed system was efficient in adjusting the frequency of fertigation cycles and controlling the prepared nutrient solution concentration, minimizing environmental problems related to effluent disposal and contributing to economy of fertilizer and water resources.