فرزانه ریگی

Roselle (Hibiscus sabdariffa L.) is a medicinal plant and belongs to the family Malvaceae, short day plant, self-pollination, one year old or a few years old in the warm and indigenous climate of Africa. The main objective in crop management is to maximize light gain by crop canopy. Nitrogen is the first element that has a shortage in arid and semi-arid regions. Considering that agriculture in the Sistan region is associated with unfavorable environmental factors such as water shortages and nutrients in the soil, and severe 120-day winds. The aim of this research was to investigate the planting direction for determining the most suitable planting direction, optimal use of chemical fertilizers and determining their best application time for the medicinal plant of Roselle under Sistan climate conditions.

A split plot experiment was conducted in a randomized complete block design with three replications at the Research Institute of Zabol University during growing season of 2016-2017. Treatments experiment included two levels of planting directions two levels (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 subsidiary agent. Ecological parameters such as light, temperature and soil moisture at the end of flowering stage and organic matter, nitrogen and soil carbon were measured after plant harvest. The morphological characteristics were measured at the end of the growth season at the end of the complete inspection of the Sepals. Data were averaged for each sample (measured for 5 samples), with variance and mean computation. The mean test was performed using a 5% mean field test and a knowledge Duncan multiple test. Statistical data analysis was performed using SAS software version 9.1.

The results showed that the effect of planting directions and split of nitrogen fertilizer on traits stem height, stem diameter, number of lateral branch, number of boll, economical yield, sepals dry weight, harvest  index was significant. Except for the number of lateral branches, all morphological traits measured for north-south planting directions were the highest. The highest economical yield was 644 kg.ha-1 the biological yield of 9352 kg.ha-1and the harvest index of 6.39 kg.ha-1were obtained from treatment (1/3 four leaf stage, 1/3 stem elongation, 1/3 flowering stage) The results of correlation coefficients between morphological and ecological traits showed that the highest correlation (0.96) (0.91) was found between the number of flower bowls with economic performance and between stem diameter and economic performance, which was positive and very significant. Thereafter, there was the highest correlation (-0.85) between biological yield and soil organic matter (after plant harvest), which was negative and very significant.

The results showed that planting directions north-south enjoying the better of ecological agents increase the yield and sepals been in medicinal plant Roselle, Also with nitrogen fertilizer management in such a way that soil nitrogen availability is more adapted to the sensitive times of the need for Roselle, It can be used with a nitrogen split application in order to increase the yield of Roselle, Application of treatment (1/3 four leaf stage, 1/3 stem elongation, 1/3 Flowering stage), which is simultaneously with the plant's sensitive vegetative and reproductive stages is recommended. Therefore, the use of chemical fertilizers as a split, while lead to reducing consumption and increasing the efficiency of chemical fertilizers in order to achieve sustainable agriculture and environmental protection is recommended.

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.