Abstract
The objective of the present study was to obtain basic data regarding the NFT system with nutrient cooling during summer. Thermal and flowing aspects in the growth of petty tomato cultivated in channels with different NFT solution cooling method and thus, with different solution temperature were described.
Temperature of nutrient solutions cooled using refrigerator could be maintained close to the setting temperature (22°C) while that cooled by means of cool ground water was some degrees higher than that level of temperature during hot weather. When the cooling systems was not be operated during hot weather, the nutrient solutions reached temperatures of about 32°C.
Temperature distribution in tomato crop was measured. Results showed that the temperature difference between tomato crop cultivated in NFT system with solution cooling using refrigerator and that using cool ground water was 2-3°C and 7-8°C (maximum) in root and stem, respectively.
It was sunny days with very high air temperature inside the greenhouse during early period of growth. The flow rate of nutrient solutions was maintained at 3 liters per minute. Under such conditions, the solution temperature increased 1°C (maximum) when it flowed in cultivation channel for a 10 m distance. Heat gained by the nutrient solutions when it flowed in the cultivation channel under such conditions was about 0.21 kW.
The stage and condition of growth of tomato root was described using the resistance coefficient of solution flow in the cultivation channels. Furthermore, the resistance coefficient was described using the Manning's equation.
