Weather and Management Effects over Nine Years of Net Ecosystem Direct Greenhouse Gas Emissions from a Cropping System in the Red River Valley, Manitoba

Abstract:

Variation in weather and crop management practices strongly determines direct greenhouse gas emissions (CO2 and N2O) from agricultural crop land. Thus a long-term study was established to relate weather and management variations to direct emissions in the Northern Great Plains of Canada. Continuously emission determinations of CO2 and N2O were established at the Trace Gas Manitoba (TGAS-MAN) Long Term Greenhouse Gas Monitoring Site at Glenlea, Manitoba, using the flux gradient micrometeorlogical technique with a tunable diode laser analyzer. The soil is poorly drained clay in the Red River Valley. The field experiment consisted of four 4-hectare plots planted to corn in 2006 and faba bean in 2007. In 2008, grass-alfalfa forage was introduced to two plots (annual - perennial) and grown until 2011 whereas the other two plots (annual) were planted to annual crops: spring wheat, rapeseed, barley and spring wheat in 2008, 2009, 2010 and 2011, respectively. In late September of 2011 the grass-alfalfa forage was killed and in 2012, 2013 and 2014 all four plots were planted with corn, soybean and spring wheat, respectively. Management decisions increased emissions such as fertilizer N addition, and hay, straw and silage crop removal greatly increased emissions while choosing legume grain and perennial crops reduced emissions. Weather variation affecting seasonal and daily soil moisture, length of spring freeze-thaw period, and crop yield served to increase or decrease emissions. The variation in management and weather will be discussed in regards to impact on net emissions over the nine year study and answer if development of greenhouse gas neutral cropping systems is possible.