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Carbon and nitrogen mineralization during decomposition of crop residues in a calcareous soil

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Publication date: October 2014
Source:Geoderma, Volumes 230–231
Author(s): J. Moreno-Cornejo , R. Zornoza , A. Faz
The present work was aimed at evaluating, under laboratory conditions, the medium-term influence of pepper residues applied at different rates (2, 3 and 5gkg1) on carbon and nitrogen cycles in an agricultural soil. The cumulative quantities of CO2–C that evolved from the pepper residue mineralization were fitted to a first-order kinetic model. These values are equivalent to ~30% of the organic carbon added for all doses, with similar mineralization constant rate (~0.09days1). Net ammonification followed the same pattern in all doses indicating a net loss of NH4 +–N by nitrification or immobilization. Net nitrification followed a different pattern depending on the dose. Final positive values were observed for the two highest doses, but when 2gkg1 was applied, net nitrification was always negative, suggesting net immobilization of N. The net N mineralization was −3.1, 13.7 and 56.7mgkg1 for doses 2, 3 and 5gkg1, respectively. Thus, the addition of pepper residues at low doses produced a net N immobilization in soil. This trend may indicate that N is likely a limiting factor for microbial growth. The activities of soil enzymes involved in C and N cycles responded differently according to the dose, indicating that only the highest dose would increase the capacity of soil to perform useful ecosystem functions. These results highlight the importance of dose when applying pepper residues, since doses <5gkg1 do not easily release available N for plant growth in the loamy calcareous soil used for this experiment.


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