Impacts of 49-51 years of fertilization and crop rotation on growing season nitrous oxide emissions, nitrogen uptake and corn yields

A field study was established in 1959 to evaluate the effects of fertilization and crop rotation on crop yields, soil and environmental quality on a Brookston clay loam. There were two fertilizer treatments (fertilized and not-fertilized) and six cropping treatments including continuous corn (CC), continuous Kentucky bluegrass sod and a 4-yr rotation of corn-oat-alfalfa-alfalfa with each phase present each year. We measured N2O emissions, inorganic N and plant N uptake over three growing seasons (2007-2009) in the corn phase. Nitrous oxide emissions varied over the 3 yr as a result of the seasonal variation in precipitation quantity, intensity and timing and differences in crop growth and N uptake. Fertilized CC lost, on average, 7.36 kg N ha(-1) by N2O emissions, whereas the not-fertilized CC lost only 0.51 kg N ha(-1). Fertilized rotation corn (RC) lost 6.46 kg N ha(-1), which was 12% lower than fertilized CC. The not-fertilized RC, on the other hand, emitted about half as much N2O (2.95 kg N ha(-1)) as the fertilized RC. Fertilized RC had corn grain yields that averaged 10.0 t ha(-1) over the 3 yr followed by fertilized CC at 5.48 t ha(-1). Not-fertilized RC corn had yields that were 61% lower (3.93 t ha(-1)) than fertilized RC, whereas the not-fertilized CC had yields that were 75% lower (1.39 t ha(-1)) than fertilized CC. Nitrous oxide emissions were found to be dramatically affected by long-term management practices and crop rotation had lower emissions in the corn phase of the rotation even though the N input from fertilizer addition and legume N fixation was greater. These N2O emission and yield results were due to both factors that are traditionally used to describe these processes as well as long-term soil quality factors, which were created by the long-term management (i.e., soil organic carbon, soil physical parameters such as bulk density, and porosity, soil fauna and microflora) and that influenced crop growth, N uptake and soil water contents.