Response of two sweet fennel varieties to plant density and fertilization with different nitrogen sources

ABSTRACT

Two fennel [Poeniculum vulgare Mill.] varieties, Dulce and Azoricum, were field grown for fruits and oil production to select the most productive variety and the most suitable source of N fertilizers in fields supplemented with cattle manure, calcium superphosphate and potassium sulfate during preparation. Seeds of Dulce and Azoricum [sweet fennel] were sown in trays filled with a mixture of peatmoss and vermiculite [11 volme]. Forty days old seedlings were transplanted in the open field at 20, 30, 40 and 50 cm apart in rows 60 cm width. Plants were then grown without [control] or with further N fertilization of different chemical sources, Ammonium sulfate [AS], ammonium nitrate [AN] and urea were applied at rate of 70 kg N/feddan. With exception oil content, fennel plants of Azoricum proved to be superior in growth parameters and yields of fruits and oil of Dulce when grown under Egyptian environmental condition. Chemical fertilization with different N sources are surpassed organic fertilization [control] alone. Except fruits number, ammonium nitrate [AN] significantly increased fennel growth parameters and yields of fruits and oil in comparison with ammonium sulfate [AS] and urea in the two seasons. Wider spacing significantly increased growth parameters, except plant height, which decreased by increasing planting distance over 20 cm. As well as, yields of fruits and oil are decreased at 40 and 50 cm spacing, the highest values were obtained with 30 or 20 cm, respectively. Concerning of interaction between all treatments, ammonium nitrate significantly increased growth parameters and yields of fruits and oil in comparison with other fertilization treatments in both varieties and all planting distance during two seasons. Azoricum plants which received ammonium nitrate and planted at 30 cm gave the highest yields of fruits and oil. The extracted fruit volatile oil of planting distance at 20 cm was GLC analyzed for identifying its constituents in both tested varieties. Seventeen compounds were identified in both Dulce and Azoricum varieties. The major oil constituents of variety Dulce were trans-anethole, methyl chavicol and P-anisaldehyde, while methyl chavicol, trans-anethole and fenchone were the major compounds in Azoricum plants. The different nitrogen sources had a great effect on the oil constituents. Chemical fertilization of different N sources affected on Anethole [trans] in both varieties. Methyl chavicol fluctuated in Azoricumas and decreased in Dulce as a result of applied chemical fertilization