The role of Ca-organic interactions in soil aggregate stability .I. Laboratory studies with glucose ¹⁴C, CaCO₃ and CaSO₄.2.H₂O

Abstract

14C-glucose with or without CaCO3 or CaS04.2H2O was incubated in a leached fine sandy loam under controlled temperature and humidity for 120 days. The addition of CaSO4.2H2O decreased the release of 14CO2, compared with soil with 14C-glucose and CaCO3 and 14C-glucose only. Addition of CaCO3 initially stimulated release of 14CO2 but subsequently the release of 14CO2 was inhibited compared with treatments with no calcium additions. Addition of both CaSO4.2H20 and CaCO3 resulted in more residual 14C in the soil at the end of the incubation period than in the control soil to which no calcium was added. The addition of CaSO4.2H2O and CaCO3 led to increases in water-stable aggregates 50-250 µm diameter, and decreased the amount of dispersible clay. In the presence of calcium and glucose, the stabilization of aggregates >1000µm occurred and they persisted for a longer time than when no additions of calcium were made.