Carbon and nutrient balances in three mountain oases in Northern Oman

Carbon (C) and nitrogen (N) fluxes of two cropping systems in three mountain oases of Al Jabal Al-Akhdar mountains of northern Oman were determined in 2008/09 and 2009/10. These comprised garlic at Ash Sharayjah (1,900 m asl) and Masayrat (1,030 m asl), pomegranate in Ash Sharayjah and Qasha’ (1,640 m asl), and date palm groves at Masayrat. Goat manure was applied to garlic fields at 47 and 40 t dry matter (DM) ha-1 at Ash Sharayjah and 42 and 37 t DM ha-1 at Masayrat. Pomegranates at Ash Sharayjah and Qasha’ received cattle dairy manure at 66 and 60 t DM ha^-1 yr^-1. Annual total gaseous C losses varied from 20.9 to 61.2 t C ha^-1 to which CH4-C contributed 2%. Total annual C surpluses were 12.5 t ha^-1 in garlic fields at Ash Sharayjah, while C deficits of -5.5 t ha^-1 were obtained at Masayrat. Annual C surpluses in pomegranate and date palm were 16.7, 7.5, and 1.7 t ha^-1 in Ash Sharayjah, Qasha’, and Masayrat. Date palm groves had total annual N surpluses of 1857 kg N ha^-1 while pomegranate fields at Ash Sharayjah and Qasha’ had annual surpluses of 1414 and 1500 kg N ha^-1.