SHAMA DAWELBEIT1, CHRISTIAN RICHTER2
1Agricultural Research Corporation (ARC), Land and Water Research Center, Sudan
2University of Kassel, Institute of Crop Science, Witzenhausen, Germany
Onion (Allium cepa L.) belongs to the most cultivated vegetable crops in Sudan. Farmers grow it mainly in the Gezira area, using Nile water for surface irrigation, and nitrogen as mineral fertiliser. Due to high pH values of Gezira Vertisols (7.5-8), a lot of the applied nitrogen gets lost by NH3-volatisation, and also due to run off and leaching as a consequence of irregular irrigation. To minimise these nitrogen losses, we should develop better systems, to establish an ecological and sustainable agriculture. Therefore, we carried out field experiments using soluble fertiliser (same amount of N as in the traditional system) together with the irrigation water. We compared this ``fertigation'' system with the traditional separate system of irrigation and fertiliser broadcasting, using three steps of nitrogen (0 N, 1 N and 2 N, 1 N = 43kg N ha-1) on the Gezira research farm, near Wad Medani, in two seasons, in a complete randomised block design with 4 replicates. In other parts of the world, fertigation is common either using sprinkler or drip irrigation. As these irrigation methods are not available in Sudan, we used the existing surface irrigation, but with a special device for calculation of the exact amount of soluble fertiliser and water needed for each sub-plot. At harvest, weight and number of large, medium, small, double and rotten onions were recorded.
Results indicate that added nitrogen in any form increased the yield significantly compared to the 0 N-treatment. In the first season, compared to ``normal'' irrigation with fertiliser broadcasting, fertigation resulted in higher weight and number of large, medium and double onions. Under these conditions, 1 N gave the highest yield of the large and medium ones. In the second season, fertigation resulted in higher weight and number of small, and in higher weight of medium and double onions.
It can be concluded that there are beneficial effects of the fertigation system via surface irrigation on onion production in the Gezira area. Further trials should show whether the proposed system can be useful also for other crops.
Keywords: Fertigation, nitrogen, onion, Sudan