Vertical distribution of soil properties and organic carbon under different land use systems in saline soils of Bangladesh

Abstract

Abstract This study has been conducted to investigate the impact on different land-use on soil organic carbon stock and selected soil properties in soil profiles; along with a preponderance of SOC into different pools of oxidizability with depth increment; under different land-use systems in saline soil and to screen out which land practices are best for soil carbon storage. Soil samples were collected at 0–15, 15–30, 30–45, 45–60, 60–75, 75–90, and >90\xa0cm depths by the opening pit in three different locations under different cropping patterns (Rice-vegetable, Rice-fallow, and Rice-shrimp) with three replicates, then analyzed. Results showed that the SOC content and SOC stock significantly (p\xa0≤\xa00.05) increased with depth increments in Rice-vegetables land-use system while it decreased with depth in the Rice-fallow system. At the greater depth of >90\xa0cm, SOC stock has been found highest which is true for both Rice-vegetables (3375 t C/ha) and the Rice-shrimp system (2268 t C/ha). But the greater depth of the Rice-fallow system contains the least amount (296.4 t C/ha). Also, textural analysis of soil showed that the soils from each cropping system were dominant in silt particles. It is found that both clay and silt particles had accumulated at a lower depth in all of the cropping systems which was also significant (p\xa0≤\xa00.05) along soil profile may be due to the puddling and tillage operations for rice cultivation. Higher content of CaCO3 was obtained under both Rice-vegetable and Rice-fallow land-use systems (5.19%) at 75–90\xa0cm and 60-75 cm depth, respectively which may be attributed to the process of calcium leaching and subsequently precipitated as CaCO3 at a lower profile. An increase in depth, active pools of carbon decreased significantly (p\xa0≤\xa00.05) in Rice-vegetables, Rice-shrimp and Rice-fallow land-use system till from 30 to 45\xa0cm, 30 to 90\xa0cm, and 45 to 90\xa0cm respectively which is an early indicator of soil quality. The highest (5.1\xa0g\xa0C/kg) and lowest (0.2\xa0g\xa0C/kg) amount of very labile fraction was obtained under Rice-vegetable and Rice-shrimp system at 75–90\xa0cm and 0–15\xa0cm depth, respectively. By contrast, passive pools of carbon and its recalcitrant nature increased significantly (p\xa0≤\xa00.05) with depth for Rice-vegetable and Rice-shrimp land-use systems.