RESPONSE OF ASIATIC LILY TO NUTRIENT SOLUTION RECYCLING IN A CLOSED SOILLESS CULTURE

The objective of this study was to evaluate growth and yield of Asiatic lily (Lilium × hybrida 'Zsa Zsa') in response to electrical conductivity (EC) of a circulating nutrient solution. Lily bulbs were planted in black tuff and grown under greenhouse conditions. The plants were fertigated starting with a fresh nutrient solution at 1.4 mS/cm. The drain solution was automatically recycled and mixed with the fresh solution to form the supply solution, which was recycled several times until its EC reached 1.6, 1.8, 2 or 2.2 mS/cm. The supply (recirculating) solution was then replaced with a fresh nutrient solution. This strategy was adopted until harvest (9 wk after shoot emergence). Results indicated that 1.6 mS/cm of the supply solution was superior to the other EC values with respect to growth and flowering. Stem height, shoot dry weight, and peduncle length decreased as EC increased up to 2 mS/cm, beyond which they did not change. A supply solution at 1.6 mS/cm exhibited the lowest pH and highest contents of P and K. As EC increased, concentrations of N, Na, Cl, Ca, Mg, Zn, and Mn in the supply solution increased. Over a period of 22 days of recirculation, pH and concentrations of N, Na, Cl, Ca, and Mg increased and those of P and K decreased with time. At harvest, the highest levels of P and Mo were detected in plants receiving a solution at 1.6 and 2.2 mS/cm, respectively. Furthermore, Cl concentration was higher in plants receiving a solution at 2-2.2 mS/cm compared with 1.6-1.8 mS/cm. Concentration of other nutrients in the leaves was not affected by EC.