Mitigating Cold and Warm Season Nitrogen Losses from Corn Systems

Tim Griffis

Our research has shown that 35% of annual nitrous oxide (N2O) emissions in Minnesota occur during the spring freeze-thaw period. Large nitrous oxide emissions from the freeze-thaw period have also been reported at numerous cold season locations globally, and can account for up to 70% of annual emissions. Our group has also shown that warmer temperatures enhance reactive nitrogen (N) losses because (de)nitrification is temperature dependent. Here, we propose to extend our mesocosm experimental approach and analyses to probe two key questions:

1) How do spring freeze-thaw cycles influence reactive N losses? and

2) Can we mitigate reactive N losses caused by warmer temperatures?

We propose to assess if using winter rye cover cropping and enhanced efficiency fertilizers (EEFs) are effective and practical strategies for reducing reactive N losses during the spring freeze-thaw period and warmer growing seasons, while maintaining high corn yields in Minnesota. A winter rye cover crop is expected to reduce excess soil nitrate and will act as a thermal mulch, thereby reducing soil temperature amplitude and the number of freeze/thaw cycles during spring. This is expected to reduce reactive N losses. The use of EEFs is expected to inhibit reactive N losses, but we are concerned that warming temperatures will reduce their effectiveness.