Optimizing Irrigation Schedule to Maximize Water Use Efficiency of Hibiscus sabdariffa under Shalatien Conditions

Abstract

A substantial experiment was conducted throughout two consecutive growing seasons of 2005/2006 and 2006/2007 at the experimental station of Shalatien, South - east of Egypt to elucidate the optimizing irrigation schedule to maximize water use efficiency of Roselle, Hibiscus sabdariffa., under moisture stress. This work was accomplished by designing 75 experimental units with split plot design. The main plots for five irrigation water quantities, (i.e. Q , Q , Q , Q and Q ) and the sub-main plots for the three plant densities, i.e. 1234 5 28000, 56000 and 84000 plants/fed. as D , D and D respectively. The variables studied were distributed in five 12 3 replicates. Soil of the location is sandy calcareous; Lithic torripsamnents and Typic torripsamnents; where CaCO content is more than 7%. Water use efficiency, water economy under drip irrigation system was 3 calculated and irrigation schedules were estimated. The achieved result could be summarized as follows: 1- A positive correlation responses between branch number and decreasing plant densities. 2- The heaviest densities and irrigation water schedule (Q ) produced the shortest plants. 2 3- The highest Fresh and dry Sepal yields, Kg/fed; (for the three plant densities, respectively i.e. 2234, 2920 kg/fed and 444, 510 kg/fed); were associated with Q D treatment, in the two successive seasons. 31 4- A highly significant increase of Fresh and dry weight of different plant organs per plant and the whole plant which tended to increase with D under Q treatment. So, it could be observed that, the most effective 13 treatment on increasing the fresh and dry weight of leaves, stems, roots and whole plant, gm/ plant was Q D , which they increased significantly in both seasons. 31 5- The number of fruits per plant significantly increased by decreasing plant densities, the highest number 8- The highest values were associated with Q D treatment for the two consecutive growing seasons, i.e., 11 1.44, 1.57 kg/m and 0.79, 0.86 kg/m for WUE and Weco, respectively and 1.83 for crop coefficient. While 33 the lowest values were associated with Q D treatment, i.e., 0.31, 0.32 kg/m and 0.22, 0.23 kg/m for WUE 53 33