Climate smart agriculture impact on soil organic carbon stocks in Madagascar

Climate smart agriculture is presented as a solution to alleviate food insecurity, mitigate climate change and contribute to climate change adaptation. In Madagascar, different sustainable agricultural practices were implemented in the last 20 years by many non-governmental organizations in order to increase crop yields, maintain soil fertility and increase household income. These practices are conservation agriculture, agroforestry systems and the use of organic fertilizers as compost and manure. This study aimed to compare the soil organic carbon storage of some climate smart practices in the Malagasy context. The soil organic carbon stock of each practice, distributed in several sites among the island, was measured and compared with the traditional practices of each study site. For conservation agriculture, the differences in the soil organic carbon content varied from 0 to 1.82 MgC ha(-1) year(-1) when compared with traditional practices (tillage and crop residues exported). For agroforestry, a difference in the soil organic carbon content of 0.68 Mg Cha(-1) year(-1) was found when comparing with the slash and burn practices in the East Coast of Madagascar but no significant soil organic carbon content was found in the Malagasy Highlands. The use of organic fertilizers such as manure, compost and urban organic waste led to an increase of soil organic carbon of 0.16, 0.81 et 0.42 Mg Cha(-1) year(-1) respectively, but these increases were not significant due to the great variability of soil organic carbon values. Results confirm the capacity of some climate smart practices to store more carbon in the soil and hence to compensate for greenhouse gases emissions. However, the storage potentiality is quite different according to the practice and its spatial extent.