Loss of nitrogen by denitrification.

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Nitrogen fertilizers are crucial for agriculture but can lead to environmental losses.
• Gaseous nitrogen loss from soils occurs primarily through denitrification.
• Understanding the factors influencing denitrification pathways is vital for nitrogen management.

Purpose of the Study:

• To investigate the gaseous forms of nitrogen lost from different fertilizers under varying soil conditions.
• To elucidate the role of denitrification in determining the composition of gaseous nitrogen emissions.
• To identify factors affecting the reduction pathways of nitrogen oxides during microbial dissimilation.

Main Methods:

• Experimental analysis of nitrogen loss from ammonium sulfate, calcium nitrate, and sodium nitrite fertilizers.
• Controlled incubation of soil samples under varying conditions (e.g., anaerobic, pH, presence of glucose).
• Measurement and identification of gaseous nitrogen products (N2O, N2, NO).

Main Results:

• Nitrogen loss from ammonium sulfate and calcium nitrate primarily yielded nitrous oxide (N2O) and molecular nitrogen (N2).
• Sodium nitrite resulted in nitric oxide (NO) release.
• Anaerobic conditions with neutral pH and glucose favored reduced nitrogen gases (N2O, N2).
• Conditions unfavorable for denitrification led to the predominance of nitrogen oxides.
• Nitrogen oxides were intermediates, reduced to N2O and N2 via microbial dissimilation, influenced by pH, aeration, and energy sources.

Conclusions:

• Denitrification conditions significantly control the quantity and form of gaseous nitrogen loss from fertilizers.
• The specific nitrogen fertilizer influences the primary gaseous products.
• Microbial dissimilation of nitrogen oxides is a key process in nitrogen cycling, with N2O often being an intermediate.
• Optimizing soil conditions can mitigate undesirable nitrogen losses and enhance nitrogen use efficiency.