Fate of carbon and nitrogen from plant residue decomposition in a calcareous soil

Carbon and nitrogen transformations in soil are microbially mediated processes that are functionally related. The fate of C and N was monitored in a clay-textured soil (Typic Haplocambid) which was either unamended (control) or amended with various plant materials at the rate of 10 g residue C/kg soil. To evaluate C mineralization, soils were incubated for 46 days under aerobic conditions. Nitrogen mineralization/immobilization was evaluated at the end of eight-week incubation experiment. All CO 2 evolution data conformed well to a first-order kinetic model, C m = C 0 (1 – e –Kt ). The product of K and C 0 (KC 0 ) was significantly correlated with some chemical and biochemical properties of the plant residues, including N concentration (r = 0.83, P < 0.001), C:N (r = –0.64, P < 0.05) and lignin: N (r = –0.81, P < 0.001). Among the plant residue composition characteristics, N concentration (r = 0.96, P < 0.001), C:N (r = –0.69, P < 0.01) and lignin:N (r = –0.68, P < 0.01) were significantly correlated with the net rates of N mineralization/immobilization (N m/i ).