Effects of prolonged flooding on the cycling of dissolved inorganic carbon in Plinthosols

NATALIA BENINI SILVA, ALFREDO BORGES DE-CAMPOS

Abstract


Cultivation of flooded rice has developed in wetlands of the Cerrado Biome as a result of the expansion of the Brazilian agricultural frontier. Changes in soil moisture content due to agricultural practices associated with flood irrigation may induce geochemical transformations in the soil. The present study aimed at investigating the effect of flood irrigation on inorganic carbon cycling through the determination of dissolved inorganic carbon (DIC) concentrations in soil solution. Incubation experiments under anoxic and reducing conditions were carried out in laboratory with samples of horizons A, AB, Bf1 and Bf2 of Plinthosols profiles from areas under 18 and 28-year of flood irrigation and natural area of the Irrigation Project Luiz Alves do Araguaia, GO, Brazil. Soil samples under flooding were incubated for 1, 7, 15, 30, 60 and 120 days to simulate the effect of prolonged flooding and after incubation the liquid fraction was analyzed for DIC. Statistical analyses of variance and linear regression as well as means compared by Student’s t-test at 5% probability were carried out on the data. Higher concentrations of DIC were found in the A horizon (up to 37.2 mg/L) from soil profiles under agricultural cultivation, which may be associated with liming or desorption processes of carbon species. Statistical analyses showed that DIC concentration correlated with soil electrical conductivity and Eh. It is concluded that solubilization of inorganic carbon is favored by flood irrigation, especially in Plinthosols that have received liming, as well as by the reducing state of the soil and higher concentrations of ions in solution.


Keywords


Geochemistry; Plinthosols; Flood irrigation; Dissolved inorganic carbon.

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DOI: http://dx.doi.org/10.21715/GB2358-2812.2018321088

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