Volume 2 Issue 1
Authors: R. A. Bustomi Rosadi; Masateru Senge; Diding Suhandy; Ahmad Tusi
Abstract: The objective of this research was to investigate the effect of EC (electric conductivity) levels of nutrient solution on the growth and yield of tomatoes under the hydroponic system. This research was conducted in a plastic house on the experimental farm of Lampung University, Lampung in Indonesia from April to July 2009. The EC treatments to nutrient solutions were S1 (1 dSm<sup>-1</sup>), S2 (2 dSm<sup>-1</sup>), S3 (3 dSm<sup>-1</sup>), S4 (4 dSm<sup>-1</sup>), and S5 (5 dSm<sup>-1</sup>) arranged in a completely randomized design with four replications. The results showed that the highest yield was under S3 (120.8 g/plant), followed by S2 (96.6 g/plant), S1 (89.7 g/plant), S4 (88.4 g/plant), and S5 (75.5 g/plant). The yields of tomato responded to EC levels of nutrient solution in the two ranges of lower and higher EC than 3 dSm<sup>-1</sup>. The yield increased as EC of nutrient solution increased from 0 to 3 dSm<sup>-1</sup> probably, due to increase of nutrients. On the other hand, the yield decreased as the EC of nutrient solution increased from 3 to 5 dSm<sup>-1</sup> probably, due to increase of water stress. So, it can be concluded that the salinity threshold of the tomatoes was 3 dSm<sup>-1</sup>. On the other hand, the highest SSC (soluble solid content) was recorded under S5 (7.34 brix), followed by S4 (6.93 brix), S3 (6.44 brix), S2 (6.26 brix), and S1 (6.11 brix). It means that the S5 treatment was the best quality. Among the range of treatments, treatment S3 (3 dSm<sup>-1</sup>) gave the highest yield, but lower SSC than S4 (4 dmS<sup>-1</sup>) and S5 (5 dSm<sup>-1</sup>).
Keywords: Salinity; Hydroponics; Deep flow techniques; Tomato; Water stress
Authors: Ahmad Taghizadeh; Adel Hosainpour; Ali Motevali; Hosain Darvishi
Abstract: The tomato (Lycopersicum esculentum) juice was condensate in a laboratory scale ohmic heater at different voltage gradients of 6, 8, 10, 12 and 14 V/cm. The condensation data were fitted to three mathematical models, Page, Logarithmic, and Midilli models. The results showed that voltage gradient significantly influenced the total heating time and energy efficiency of ohmic processing. Three statistical tools were used to quantify the goodness of fitting: the coefficient of determination (R2), the reduced chi-square (χ2) and root mean square error (RMSE). Although the Midilli model showed the best fit, the Page model was selected, since it had almost a similar performance but the model is simpler with two parameters instead of four. Increasing the voltage gradient resulted in a considerable increase in average energy efficiency and it was in the range of 50.91 to 75.44 %.
Keywords: Ohmic Heating, Modeling, Energy Efficiency, Tomato Juice