ANDREAS BUERKERT1, MAHER NAGIEB1, STEFAN SIEBERT1, A. AL-MASKRI2
1University of Kassel, Institute of Crop Science, Germany
2Sultan Qaboos University, Department of Agriculture, Al Khod, Oman
Little is known about nutrient fluxes as criteria to assess the sustainability of traditional irrigation agriculture in eastern Arabia. In this study GIS-based field research on terraced cropland and groves of date palm (Phoenix dactylifera L.) was conducted over two years in two mountain oases of northern Oman to determine their role as sinks for nitrogen (N), phosphorus (P) and potassium (K). At Balad Seet about 55% of the 385 fields received annual inputs of 100-500kg ha-1, 26% of 500-1400kg ha-1 and 19% that were left fallow did not receive any N. Phosphorus was applied annually at 1-90kg ha-1 on 46% of the fields, whereas 27% received 90-210kg ha-1. 27% of the fields received no K, while 32% obtained 1-300kg K ha-1 and the remaining ones up to 1400kg ha-1. At Maqta respective N-inputs were 61-277kg ha-1 in palm groves and 112-225kg ha-1 in wheat (Triticum sp.) fields, P inputs were 9-40kg ha-1 and 14-29kg ha-1, and K inputs 98-421kg ha-1 and 113-227kg ha-1. For cropland, partial oasis balances (comprising inputs of manure, mineral fertilizers, N2-fixation, irrigation water and outputs of harvested products) were with surpluses of 139 kg N, 41 kg P and 99 kg K in Balad Seet (totalling 4.6 ha) and of 135 kg N, 16 kg P and 57 kg K ha-1 in Maqta (0.4 ha) similar. This was despite the fact that N2-fixation by alfalfa (Medicago sativa L.), estimated at 480 kg ha-1 yr-1 with an average total dry matter of 22 t ha-1 contributed to the cropland N-balance only at the former site. Respective palm groves balances, in contrast, were with 313 kg N, 43 kg P and 191 kg K ha-1 (on 8.8 ha) and 83 kg N, 14 kg P and 85 kg K ha-1 (on 3.6 ha) remarkably different in both oases. This was mainly due to the recycling of nutrients in human faeces from the artificially high population at Balad Seet living largely on imported food.
Keywords: Animal manure, irrigation agriculture, N2-fixation, sustainability