الفهرس 
Introduction
I. Effect of Sowing DateOnly 14 pages are availabe for public view
 |  | from | 145 |  |  |
| | | from | 145 | | |
Abstract
This investigation was conducted during two successive seasons of 2004 and 2005 in a private Farm at Dar El-Salam, Sohage Governorate to study the influences of different sowing dates and mineral and bio N and / or p fertilization treatments on the vegetative growth, yield and chemical constituents of two cultivars of roselle , Hibiscus sabdariffa, L. plants, namely Sabahia 17 and Sudany under the conditions of Sohage governorate. Therefore, two field experiments were carried out. The first experiment aimed to explore the optimum sowing date of the two aforementioned, cultivars of roselle , (February 15th, March 1st, March 15th and April, 1st).
While, the second one was executed to study the response of Hibiscus sabdariffa cv. Sabahia 17 to supplement with 25, 50 and 75% of the recommended dose of mineral N and / or P fertilization in combination with bio fertilizers i.e. biogein (containing N fixing bacteria) and / or phosphorein (containing P dissolving bacteria) in terms of vegetative growth, yield and chemical composition.
The most important results of each one of both two experiments could be summarized as follows: -
I- First experiment:
Response of roselle , cultivars i.e. Sabahia 17 and Sudany to four sowing dates (February 15th, March, 1st, March, 15th and April, 1st).
I-a- Effact of cultivars:
I-a-1-Vegetative growth traits:
No significant differences between the two tested cultivars (Sabahia 17 and Sudany) were detected concerning their vegetative growth traits namely plant height, stem diameter, branch number / plant, as well as, herb fresh and dry weight / plant in the two experimental seasons, except that cultivar Sudany plants were significantly taller and heavier (dry weight) than Sabahia 17 plants in the second season.
I-a-2-Yield and yield components:
Roselle cv. Sabahia 17 plant had significant higher number of fruits / plant in the two experimental seasons than those of cultivar Sudany, while, no significant differences between both two examined cultivars, concerning, sepals fresh weight/ plant, dry weight of sepals per plant, per plot and per feddan, as well as, seed yield per plant and per feddan in the two growing seasons ware noticed.
I-a-3-Chemical composition:
• Anthocyanin pigment percentage was higher in the sepals of cultivar Sudany than those of cultivar Sabahia 17 plants, in this regard the difference between the two cultivars was significant in the two seasons. On the other hand, Acidity % was significantly higher in the sepals of Sabahia 17 than those of Sudany in both two seasons.
• The contents of the photosynthetic pigments (chlorophyll a, b and carotenoids) were higher in the fresh leaves of cultivar Sabahia 17 than those of cultivar Sudany in the first and second seasons. In this regard, differences between the two cultivars were significant in the first season concerning chlorophyll a and in the second one regarding the three pigments.
I-b- Effect of sowing dates:
I-b-1-vegetative growth traits:
Roselle plants sown on April 1st were significantly taller than those grown on February 15th ,in the second place came plants grown on March 15th then, March 1st. On the contrary, stems of plants grown on February, 15th were the thickest followed by those grown on March, 1st or March, 15th compared with those planted on April, 1st which gave the thinnest stems in both growing seasons.
Roselle plants grown on March 15th and March 1st had the highest branch number and heaviest fresh and dry weights of herb/ plant in comparison with other sowing dates i.e. Feb, 15th and April, 1st.
I-b-2-Yield and yield components:
Sowing date on March, 15th followed by March, 1st resulted significantly in higher fruits number / plant, heavier fresh higher fruits weight / plant, heavier sepals dry weights per plant, per plot and per feddan, as well as, higher seed yield per plant and per feddan than those of plants sown on Feb., 15th or April, 1st in the first and second experimental seasons.
I-B-3-Chemical composition:
Anthocyanin pigment and acidity % in the sepals were higher due to sowing roselle plants on March, 15th followed by March, 1st than those sown on Feb., 15th or April, 1st in the two seasons Chlorophyll a, b and carotenoids contents in the fresh leaves of roselle were higher as a result of sowing roselle plants on March, 15th and March, 1st than sowing the plants on Feb., 15th or April, 1st in the two growing seasons.
I-c-Effect of the interaction between cultivars and sowing dates:
The interaction treatments had, in most cases, insignificant effect on vegetative growth, yield and yield components and chemical constituents of Hibiscus sabdariffa cvs. Sabahia 17 and Sudany plants in the two experimental seasons, except that significant influence of the interaction was found on plant height and carotenoids content in the second season and on sepals fresh weight / plant and anthocyanin pigments in the first season.
Generally, it could be noticed that sowing the two cultivars of roselle plants on March, 15th followed by March, 1st enhanced vegetative growth, yield and chemical composition than other sowing dates.
II- Second Experimental:
Effect of some bio and chemical fertilization treatments on growth, yield and chemical composition of Hibiscus sabdariffa L. cv. Sabahia17. plants
II-a-Vegetative growth traits:
All vegetative traits namely, plant height, stem diameter, and branch number, as well as, herb fresh and dry weight / plant of roselle plants were significantly affected by bio and chemical fertilization treatments in the two experimental seasons. Supplying roselle plants with 75% and 50% of the recommended mineral N and / or P fertilization dose in combination with, phosphorein or the mixture of both biofertilizers increased, all vegetative growth parameters compared to the control treatment. In this concern, fertilizing roselle plants with 75% of the recommended dose of mineral NP fertilization in combination with the mixtur of biogein + phosphorein gave the highest values of vegetative growth aspects.
II-b-Yield and yield components:
Generally, number of fruits / plant, sepals fresh weight / plants, sepals dry weight / plants. per plot and per fed. and seeds dry weight / plant and per fed. of roselle plants were augmented due to fertilization with 75% and 50% of the recommended mineral NP fertilization dose with the mixture of bio fertilization (Biogein + phosphorein), followed by 75% of the recommended dose of mineral P fertilization in combination with phosphorein. Supplying roselle plants with 75% of the recommended mineral NP fertilization dose with the mixture of bio fertilization (Biogein + Phosphorein) was the best treatment to improve yield components.
II-c-Chemical composition
The most effective bio and chemical fertilization treatments which gave the highest contents of the anthocyanin pigments in the dry sepals of roselle plants were 75% and 50% of the recommended mineral NP fertilization dose in combination with the mixture of biogein + Phosphorein followed by 75% of the recommended mineral P fertilization dose combined with Phosphorein.
Generally, acidity % in the dry sepals of roselle plants were augmented due to fertilization with 75% and 50% of the recommended mineral NP fertilization dose combined with the mixture of bio fertilization (Biogein + Phosphorein), followed by 25% of the recommended mineral NP fertilization dose with the mixture of bio fertilization (Biogein + Phosphorein), which gave the highest acidity percentage.
The most effective bio and chemical fertilization treatments which gave the highest contents of the three photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) in the fresh leaves of roselle plants were in descending order, 75% of mineral NP fertilization dose + the mixture of biogein and phosphorein, and 75% of mineral P fertilization dose + phosphorein.
Plants received 75% or 50% of the recommended mineral NP fertilization dose in combination with the mixture of biogein + phosphorein produced the highest N and P percentage and content in dry herb of roselle plants, followed by the plants which supplied by 75% of the recommended mineral P fertilization dose combined with phosphorein.
RECOMMENDATIONS
From obtained data regarding the first experiment, it could be recommended to sowing cultivar Sabahia 17 or cultivar Sudany of roselle plants on March 15th to promote their vegetative growth and enhanced the sepals yield and chemical constituents (anthocyanin and acidity) under Sohage Governorate conditions.
Concerning the second experiment, it could be concluded that fertilization roselle plants cv. Sabahia 17 with 75% followed by 50% of the recommended dose of mineral NP fertilization in combination with biofertilizers (biogein + phosphorein) resulted in promoting vegetative growth and stimulation the yield and improving the chemical constituents. In most cases, no significant difference between 75% or 50% of the recommended dose of mineral NP fertilization. Therefore, it is recommended, economically and environmentally, to fertilize roselle , Hibiscus sadbariffa L, plants cv. Sabahia 17 with 50% of the recommended dose of mineral NP fertilization (100kg/ fed. ammonium nitrate, 33.5 % N + 75 Kg/ fed calcium super phosphate, 15.5%P2O5 +75Kg/ fed. of potassium sulphat, 48% K2O) in combination with a mixture of biogein + phosphorein in order to enhance the vegetative growth and promote the yield components (dry sepals and dry seeds), as well as, improve chemical composition (anthocyanin pigments and acidity) of roselle plants cv. Sabahia 17 under the conditions of Sohage and upper Egypt governorates.