Question

Balance between nitrogen mineralization and nitrogen immobilization

Answer 1

The effect of increasing available soil N (soil + fertilizer) on apparent N mineralization and residues decomposition under different tillage systems was evaluated in a maize crop (Zea mays L.) in the Pampean Region of Argentina. A wide range of N soil + fertilizer was generated by differential N fertilization (16 to 342 kg N/ha) and total crop N uptake, grain yield and N liberated during residues decomposition were determined. These variables were integrated in a N budget and apparent N mineralization from humic substances estimated. Grain yield and N uptake were closely related to N soil + fertilizer. The increase of N soil + fertilizer had a depression effect on apparent N mineralization from humic substances, but stimulated residues decomposition. Soil humic substances acted as a source or sink of N, depending on the level of N soil + fertilizer in the system, meanwhile residue decomposition was always a source of N for the crop and liberated about 18 kg N/ha. Tillage system did not affect N absorbed by the crop, grain yield, residues decomposition and apparent N mineralization. The interaction between N soil + fertilizer and mineralization of N from soil organic components must be included in the N balance equation for determining more precise N doses in maize crops under a Pampean scenario