The effect of irrigation and nitrogen levels on morphological traits, yield and yield components of roselle (Hibiscus sabdariffa L.)

In order to study the effect of low irrigation and nitrogen fertilization on morphological traits, sepal yield, and yield components of Roselle (Hibiscus sabdariffa L.), an experiment was conducted as split plot design based on randomized complete blocks with three replications, at Saravan, Iran in 2010. In this research, irrigation was considered as main factor with three levels (irrigation after 60, 120 and 180 mm evaporation from pan class A) and nitrogen rate was considered as sub factor with four levels (0, 60, 120 and 180 kg N.ha-1). The results showed that irrigation and nitrogen levels had significant effect on plant height, stem diameter, fruit number per m2, sepal fresh and dry yield, and biological yield. However, sepal dry weight per single fruit and sepal harvest index per fruit were only affected by irrigation, and sepal harvest index per plant was only affected by nitrogen. The interaction effect between irrigation and nitrogen significantly affect the sepal fresh and dry yield. According to the means comparison, increasing of irrigation intervals from 60 to 180 mm evaporation reduced the plant height, stem diameter, fruit number per m2, sepal fresh and dry yield, biological yield, and sepal dry weight per single fruit to 48.1%, 31.8%, 41.3%, 58%, 54.9%, 67% and 22.7%, respectively. In addition, the increased use of nitrogen from 0 to 120 kg.ha-1 could increase the mentioned traits to 13.7%, 8.6%, 37.1%, 43.3%, 44.1%, 25.5%, and 5.7%, respectively. Overall, according to the results of current study, irrigation after 120 mm evaporation with 180 kg N. ha-1 treatmentcould be suggested for roselle cultivation in Saravan, Iran.