Separating Weather and Management Effects on Nitrous Oxide Emissions for a Cropping System in Manitoba
Separating Weather and Management Effects on Nitrous Oxide Emissions for a Cropping System in Manitoba
Previously Published Material: At AGU 2014 San Francisco initial idea of partitioning weather and management effects and preliminary results were presented in an oral presentation. We have extended the analysis to all of 2014 and used more appropriate multivariate approaches than at the preliminary result presentation. We will also present more mechanistic relationships of management effects on emissions. The previous presentation presented more "associative" relations.
Abstract ID#: 35260
English Abstract:
Weather and crop management practices strongly determine N2O emissions from cropped land. We report here the results of a long-term study examining weather and management variations on N2O emissions at the Trace Gas Manitoba Long-Term Greenhouse Gas Research Site near Winnipeg in the Red River Valley, Manitoba. N2O emissions and CO2 exchange, using the flux gradient technique and a tunable diode laser analysis system, as well as meteorological, soil conditions and crop yields were monitored 2006 to 2014. The soil is poorly drained clay, high in soil organic matter. The site was managed as four, 4-hectare plots planted to corn in 2006 and faba bean in 2007. In 2008, grass-alfalfa was introduced to two plots (annual, perennial) and grown until 2011 whereas the other two plots (annual) were planted to annual crops 2008-2011. In late summer 2011, grass-alfalfa was terminated and 2012-2014 all four plots were planted to annual crops. N2O emissions were limited to several weeks following fertilizer addition at planting in spring and for several days during soil thaw in April. Weather (meteorological and associated soil conditions) and management (agronomic practices and associated soil conditions, CO2 exchanges, and yields) effects on cumulative N2O emissions were partitioned using univariate and multivariate statistical approaches. Weather conditions influenced the expression of management effects on N2O emissions. The duration of frozen conditions over winter resulted in nitrate concentration at thaw determining the amount of N2O emissions at that time. The consistent occurrence of early summer rains resulted in emissions at this time if fertilizer N had been applied at planting. In conclusion, weather conditions determined the potential for N2O emissions but management practices such as choice of crop (leguminous or not) and fertilizer application rate determined the expression of N2O emissions.