Evaluation of the Effect of Nitrogen Fertilizer Splitting and Planting Directions on Biochemical Characteristics and Yield of Roselle (Hibiscus sabdariffa L. (

Roselle (Hibiscus sabdariffa L.) is one of the important medicinal and industrial herbs in tropical and semi-tropical regions, which, in addition to multiple drugs use. The quality and quantity of the active ingredient of medicinal plants are affected by the applied crop. Light is recognized as one of the most important factors in competition in ecosystems. Nitrogen is the first element that has a shortage in arid and semi-arid areas due to lack of soil organic matter.  Since the use of maximum environmental capacity and the most suitable growing conditions in order to increase the quantitative and qualitative yield and maximize productivity, it is important for agricultural management. The aim of this research was to investigate different cultivars to determine the most suitable culture for planting, optimum use of chemical fertilizers and determine their best time for increasing the quantitative and qualitative yield under Zabol climatic conditions. A split-plot experiment was conducted in a randomized complete block design with three replications at the Research Institute of Zabol University during the growing season of 2016-2017. Treatments experiment included two levels of planting directions (North-South, East-West) as the main plot and the split of nitrogen fertilizer from the source of urea in four levels (1/3 per planting, 1/3 four-leaf stage, 1/3 stem elongation; 1/2 post planting, 1/2 four-leaf stage; 1/2 four-leaf stage, 1/2 stem elongation; 1/3 four-leaf stage, 1/3 stem elongation, 1/3 flowering stage) as a sub-plot. Ecological parameters such as light, at the end of the flowering stage, Biochemical characteristics and yield were measured at the end of the growing season. Analysis of variance done by software SAS ver. 9.1 and comparison of means treatment by Duncan test at 0.05 level.  The results of the analysis of variance showed that the interaction of planting directions and nitrogen fertilizer split exception for the traits vitamin c, for all traits measured is very significant. Based on the results of the comparison of means treatments showed that all traits had the highest amount in the planting directions (north-south). The highest dry sepal yield (784 kg.ha-1) and anthocyanin (2.98 mg.g-1) were obtained from north-south planting. The correct timing of fertilizer use is more important than the total amount of fertilizer used. Split timing of nitrogen application for the use of 1/3 four-leaf stage, 1/3 stem elongation stage, 1/3 flowering stage, increased the qualitative and functional characteristics of roselle. The effect of Interaction planting direction and splitting of fertilizer was significant on carotenoid, the highest of carotenoid was obtained at north-south with an application nitrogen fertilizer at 1/3 four-leaf stage, 1/3 stem elongation, 1/3 Flowering stage (0.36 mg.g-1).   In general, the results of this research showed that for planting directions North-South, using better ecological factors such as light, temperature, nutrients, and followed by application of nitrogen fertilizer, split in four-leaf stage, stem elongation, flowering Improvement of growth, an increase of yield and quality of sepal in the Roselle plant. Since nitrogen is one of the most effective elements in increasing the quality yield of medicinal plants, optimum management of nitrogen as a split application at times that are more adapted to the critical stages of the plant's needs. It is recommended to achieve sustainable agriculture and environmental protection.