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The response of the sugar beet to planned water stress and nitrogen treatment in a semiarid area of the Bekka plain in Lebanon Volume 13, issue 2, Juin 2002

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Authors
Institut de recherches agronomiques du Liban, Département d'irrigation et d'agrométéorologie, Tal Amara, PO Box 287, Zahlé, Liban.
  • Page(s) : 113-20
  • Published in: 2002

The response of sugar beet (Beta vulgaris) to planned water stress is the object of this study. The experiment consisted of two water regimes irrigated at 100% (I-100) and 60% (I-60) of field capacity. In each regime, four nitrogen treatments were applied in four replicates: N0 (no nitrogen), N1 (100 units/ha), N2 (180 units/ha) and N3 (260 units/ha). Plant growth, expressed as leaf area and dry matter, was found to be highly affected by both water stress and nitrogen application rate. The results showed that the growth of sugar beet was much lower in soils irrigated at 60% of field capacity than in soils irrigated at 100% of field capacity. The ratio of underground to aboveground dry matter increased gradually during the vegetative growth and higher values were obtained at root maturity. It was noticed that in this experiment, sugar beet yield was higher and sugar content was lower under the I-100 regime than under the I-60 regime. On the other hand, yield was strongly dependent of the level of nitrogen application. The results showed that the application of 260 units/ha of nitrogen fertilizer produced 223 tons/ha and 169 tons/ha at 100% and 60% of field capacity, respectively. Water use efficiency was also affected by the irrigation regime and was found to be higher under the I-60 regime than under the I-100 regime. Furthermore, water use efficiency seems to be dependent of the nitrogen application rate in each irrigation regime. Finally, nitrogen uptake was higher in those plants that were the most fertilized. Leaf nitrogen concentration was almost twice the amount in the roots. There were significant differences in nitrogen use efficiency among different treatments. Higher values were obtained in soils treated with a high rate of nitrogen application.