A PRECISE IRRIGATION SYSTEM WITH AN ARRAY OF NOZZLES FOR PLUG TRANSPLANT PRODUCTION

摘要

A precise irrigation system with a 6 × 12 array of needle-like nozzles was developed for plug transplant production using 72-cell plug trays. When a command for irrigation is given to the system, all of the nozzles are directly inserted into the corresponding cells at the same time to discharge a predetermined amount of water or nutrient solution. The amount of irrigated water from each nozzle (Q) can be controlled by adjusting the discharge time to keep the solenoid valve open (T) and by discharge pressure (P). The objectives of the present study were: (1) to obtain quantitative data for the control of Q, and (2) to examine the performance of the system during a plug transplant production period of 20 days. By adjusting T of each nozzle individually and P, a uniform distribution of Q was achieved over the tray. Consequently, a high value of Christiansen coefficient of uniformity was obtained (97.2% to 98.4%). During the plug transplant production period, the volumetric water content in each cell could be controlled by using the system without any growth deterioration of the transplants owing to the root damage caused by the nozzle insertion into the substrate. These results demonstrate that this system is feasible for precise irrigation management of plug transplant production