Nitrogen mineralization in a coarse soil of the semi-arid Pampas of Argentina

Use of the nitrogen balance sheet method as a fertilization strategy in the semi-arid Pampas of Argentina is restricted because of a lack of available information regarding nitrogen mineralization in its coarse soils. Our objective was to determine nitrogen mineralization during corn (Zea mays L.) and following wheat (Triticum aestivum L.) growing cycles under contrasting tillage systems in a representative soil of the region. Mineralized nitrogen from decomposing residues was estimated using the litter bag method and mineralization from soil organic matter using a mass balance approach. Soil water content was higher under no-till during the corn growing season and no differences were detected for wheat during this period. Soil temperature was practically not affected by tillage system. Biomass and nitrogen absorption were higher under no-till than under disk till in corn (p <= 0.05), as were nitrogen mineralization from residues and organic matter (p <= 0.05). In wheat, no differences in biomass, nitrogen absorption and mineralization were detected between treatments. Mineralization during crop growing cycles accounted for 44.8-67.5% of the absorbed nitrogen. Differences in nitrogen mineralization between tillage systems resulted from the greater water availability under no-till than under disk till during the summer.