Growth of Rice Seedlings for Manual Transplanting by Hydroponics Using Coconut Coir as Culture Medium

抄録

Rice seedlings were hydroponically grown using coconut coir as culture medium for manual transplanting in the tropics. When the rice seedlings were grown on coir saturated culture solution with a nutrient concentration 5-, 10-, 15- and 20-fold that of a standard culture solution for rice, the values of the shoot and root dry weight were higher of the 10-fold concentration than at the other concentrations of the solution at 20 days after sowing (DAS). The dry weight volumes of the plant parts of the seedlings grown on coir saturated with the 10-fold concentration (CH) solution were similar to or even higher than those of the seedlings grown in soil medium (SM) at 11 DAS. The dry weight increases in CH, however, became less appreciable than that in SM thereafter, and the dry weight values of the shoots and roots in CH were lower than those in SM after 19 DAS. The CH seedlings had more primary roots but fewer branch roots, resulting in a lower value of the total root length than that SM for the seedlings at 19 DAS. Moreover, the contents of chlorophyll and proteins in the leaf blades of the CH seedlings were lower than those of the SM seedlings during this period. Growth analysis indicated that the lower crop growth rate of the CH seedlings from 23 to 27 DAS was ascribed to the lower value of the leaf dry weight and lower net assimilation rate than those of the SM seedlings. Measurement of the photosynthetic rate supported the results of growth analysis. These results suggest that although rice seedlings can be hydroponically grown on coir media, their characteristics are inferior to those of the seedlings grown in soil.