New irrigation-plant production system for water conservation in ornamental nurseries: Quantification and evaluation of irrigation, runoff, plant biomass, and irrigation efficiencies

A new irrigation/plant production system, Multi-Pot Box System (MPBS), was field-evaluated during the two growing seasons (summer and fall, 2001) for efficient use of irrigation and rainfall for container nursery plant production. The system was compared to the conventional system (CS) irrigated with overhead sprinklers. Viburnum odoratissimum (Ker-Gawl.) was grown as a test plant. The following treatments were imposed: (i) three white color MPBSs with side-mount water level switches installed at 0.01, 0.02, and 0.03 m from the bottom of the system reservoir, (ii) three black color MPBSs with level switches installed at the same depths as in the white MPBSs, and (iii) control (CS). The level switches controlled the water levels at pre-determined levels and triggered irrigations automatically at these threshold levels. The white and black MPBSs were very effective in increasing irrigation water use efficiencies (IWUE), rainfall harvesting, and plant biomass production as compared to the CS. For example, in the summer season, only about 30% of the plant water use in the MPBSs was supplied by irrigation water, thus, reducing irrigation requirements and resulting in high IWUE. The color of the MPBS had a significant effect on plant growth but no significant effect on irrigation demand or runoff. The water use efficiencies and plant biomass production of the white MPBS were significantly greater (p < 0.05) as compared to the black MPBS. The efficiencies and plant biomass production of the black MPBS were significantly greater than the CS. In the fall, the white and black MPBS with level switches installed at 0.01 m resulted in the lowest irrigation demands. In the summer, about half of the total rainfall (320 mm) was captured in the reservoir of the MPBSs. In the fall season, approximately 30% of the total rainfall (90 mm) was captured in both systems and later used by plants. At least 92% and 76% of water savings, relative to the CS, were achieved by using the white MPBS in the summer and fall, respectively. Results suggested that under these experimental and similar climatic conditions, the white MPBS is superior to the black MPBS and CS. The white MPBS presents a potential opportunity for an efficient irrigation and significant water savings for container-grown nurseries.