Effect of irrigation levels and planting date on yield and water use efficiency of Hibiscus sabdariffa L.

Nowadays, changes in cultivation pattern towards drought resistant species are proposed as a solution to tackle drought. To study the effect of irrigation levels and planting date on yield and water use efficiency of Hibiscus sabdariffa L., an experiment was conducted in the research field of agriculture college of Islamic Azad University of Birjand during 2010-2011. Three levels of irrigation (20, 60 and 100 percent evapotranspiration of source plant) as main plots and different planting dates (May 10th, June 1th and June 20th) as sub plots were studied in a split plot experiment with three replications in a randomized complete blocks design. The results indicated that different irrigation levels and planting dates had significant effects on number of flowers per square meter, dry and fresh weight of flowers, total biomass yield and water use efficiency (flower and biomass). The highest number of flowers per square meter (62.42), flower fresh weight (62.50 grams per square meter), flower dry weight (10.30 grams per square meter), total biomass yield (150.3 grams per square meter), water use efficiency of flowers (0.024 gram per) and water use efficiency of biomass (0.532 gram per liter) were obtained from the first planting date i.e. May 10th. Also, the highest number of flowers per square meter (55.88), flower fresh weight (72.40 grams per square meter), flower dry weight (11.46 grams per square meter), biomass yield (142.5 grams per square meter), water use efficiency of flower (0.042 gram per liter) and water use efficiency of biomass (0.897 gram per liter) were recorded for the irrigation level of 20 percent evapotranspiration of the source plant. Irrigation levels and planting dates had no significant effect on flower harvest index. The interaction effect of irrigation levels and planting dates was significant on flower dry and fresh weight, total biomass yield and water use efficiency (flower and biomass). The highest values of these traits were obtained at planting date of 10 May and irrigation level of 20 percent evapotranspiration of source plant. Generally, with regard to the early cold fall and long growth period of Hibiscus sabdariffa, its plantation is not recommended in Birjand climate. According to the results of this experiment, water requirement of this plant was low.