Development and evaluation of a DSS for drainage management in semi-closed hydroponic systems
The recycling of greenhouse effluents in soilless cultivation systems is environment-friendly, since the waste of water and the disposal of nutrients to the environment is drastically reduced or even eliminated. However, a long-term recycling of the effluents may result in accumulation of Na+ and Cl- in the recycled nutrient solution. The major aim of the present research was to test the performance of a Na+ mass balance model operating as part of a decision support system in a tomato crop grown in a closed-loop hydroponic system. Three treatments were compared: a completely open, a completely closed and a semi-closed hydroponic system during one experimental period lasting from October 2011 to January 2012. The fresh water used for the preparation of the nutrient solution contained 2 mM NaCl. During the total experimental period, the water uptake by the crop was relatively low, near to 130 L m-2, and thus, the concentration of Na+ in the closed system did not surpass the level of about 20 mM during the total experimental period. Comparison between measured and simulated Na+ values gave fair results. The system was efficient at minimizing the discharge of nutrient solution effluents in semi-closed hydroponic systems, thereby maximizing the water use efficiency.