126-6 Mineralizable C and Nitrate Limitation On Nitrous Oxide from an Intensive Maize System: Interaction Between Cover Crop and Fertilizer Rate.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes
Monday, October 22, 2012: 2:30 PM
Duke Energy Convention Center, Room 204, Level 2
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David C. Mitchell, Michael J. Castellano, John E. Sawyer, Jose L. Pantoja and Fernando Miguez, Department of Agronomy, Iowa State University, Ames, IA
Use of cover crops has been proposed to reduce loss of nitrogen (N) from cereal production systems, including as nitrous oxide (N2O). This effect on N2O has been attributed to uptake of soil nitrate (NO3) by the cover crops. However, previous studies have not found consistent effects of cover crops on N2O emissions. It is necessary to examine the biochemical mechanisms by which cover crops affect N2O emissions. In a field study in central Iowa, we observed a winter rye (Secale cereale L.) cover crop in maize (Zea mays L.) to decrease N2O emissions only in unfertilized plots and to increase N2O emissions at 135 kg N fertilizer ha-1. The rye decreased soil NO3 concentrations at all N fertilizer rates but did not affect soil moisture. We incubated soils from this site at constant temperature and moisture in the laboratory and measured N2O production in the soils with and without addition of NO3 and glucose. Nitrate addition increased N2O production in unfertilized soils but had no effect in fertilized soils. Glucose addition increased N2O production at all fertilizer rates. These results show that soil NO3 concentration did not limit N2O production except in unfertilized soils. In fertilized soils, N2O production was limited by availability of mineralizable carbon (C). These results indicate that input of mineralizable C by cover crops may have increased N2O emissions in fertilized soils at this site. The effect of cover crops on mineralizable C availability should be considered in evaluations of their effect on N2O.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes