Soil organic carbon determines the quality, productivity and the sustainability of agricultural systems. Organic matter input and output are the processes that lead to the system's sustainability from the perspective of organic carbon balance. Soil and crop management systems influence the return of organic carbon to the irrigated rice field. This study aimed to evaluate the recovery of soil organic carbon of irrigated rice fields treated with organic and conventional managemet systems. The

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... y was conducted at Imogiri Bantul D.I. Yogyakarta Indonesia, to evaluate carbon dynamics (organic carbon inputs and losses) in irrigated rice fields under organic and conventional rice management systems. The organic rice management system in this study is defined as eliminating the use of agrochemical materials that are poisoning the environment and relying on the use of organic materials, while conventional rice systems are defined as relying on the use of agrochemical materials. The results showed that the Mentik Wangi organic rice produced 11.227 t.ha-1, while the conventional rice system produced 11.877 t.ha-1 dry biomass. The return of organic carbon were derived from organic fertilizer, rice stump and rice roots, while the carbon loss were caused by straw and grain removals. In the organic rice system, the total carbon input (recycled) was 7.161 t.ha-1, while the output (removal) was 6.194 t.ha-1, implying a sustainable system with a greather input than the output. On the contrary, in the conventional rice system, the total carbon input was 4.946 t.ha-1, while the loss was 6.931 t.ha-1, implying carbon deficits which my lead to unsustainability.