Impact of Fertilization and Crop Rotation on Nitrous Oxide Emissions From Agricultural Soils.

A long-term study was established in 1959 to investigate the effects of fertilization and crop rotation on crop productivity, soil and environmental quality.  Treatments included both fertilized and non-fertilized continuous corn and rotation corn (corn-oats-alfalfa-alfalfa) with all phases of the rotation present each year. Nitrous oxide emissions were measured in the continuous corn treatments as well as in the corn phase of the rotation treatments on a weekly basis from April to October in each of 3 years.  Ancillary data including soil temperature, water content and soil inorganic N levels were also obtained.  On average, fertilized continuous corn had 27% greater nitrous oxide emissions (7.00 kg N/ha) than the corn phase of fertilized rotation corn (5.49 kg N/ha) and 19 times greater emissions than non-fertilized continuous corn (0.36 kg N/ha).  However, the temporal dynamics of the nitrous oxide emissions varied with treatment.  Fertilized rotation corn had greater emissions at the beginning of the growing season whereas it had lower emissions at the end of the growing season compared to fertilized continuous corn. Fertilized rotation corn improved soil structure and aeration and enhanced evapotranspiration which minimized the frequency of anaerobic events. Nutrient uptake and corn grain yields were highest with the fertilized rotation corn treatment and lowest with the non-fertilized continuous corn. Although nitrous oxide emissions were low with non-fertilized continuous corn, the grain yields for this treatment were very low and not sustainable.