Abstract
We studied the effect of the diffence between periodic renewal of whole nutrient solution at intervals of twenty days versus non-renewal while adding water and fertilizer based on electric conductivity (EC) level in NFT on the composition of solution, tomato growth and yield in each cropping type. In non-renewal treatment, slow increase of Ca and Mg, decrease of P over cultivation, and decrease of K during the fruit development stage were observed in both cropping types. Fruit yield was increased with non-renewal treatment compared to that with renewal treatment in semi-forcing culture. While in retarding culture, since the EC value rose to 3.0 dS/m with non-renewal treatment, there were no significant differences in fruit yield between treatments.
Provided that the concentration of each element was within the range found in this experiment, fruit yield was not decrease with non-renewal of the solution. Renewal of the whole solution was not necessary.
