Overview/Theory
As concerns about global climate change have increased, the need to assess the relative contribution of agricultural soils to greenhouse gas (GHG) emissions has grown in importance. The GHG issue has become of increasing concern as researchers strive for sustainable methods to produce biomass crops for biofuel production. The production of these gases is highly dependent on soil properties and plant-microbe interactions occurring below ground. Interestingly, not all cropping systems contribute equally to the production of greenhouse gases. There is some evidence suggesting that perennial systems may contribute less to GHG emissions than annual systems. Also, it is known that management practices like nitrogen fertilization can have a large impact on GHG’s, especially nitrous oxide (N2O), which produces around 300 times the warming effect of carbon dioxide (CO2). Topographic position can also play a large role in GHG emissions. Greater emission of N2O has been found under corn in cultivated floodplains largely due to environmental factors such as greater amounts of organic matter and soil moisture. Methane (CH4) is usually produced from waterlogged soils, but can actually be consumed in drier upland soils. However, the consumption of methane can be greatly inhibited by nitrogen fertilization. The combination of varying cropping systems and landscape positions at Landscape Biomass Project at Uthe Farm allows us to analyze the interactive effect of management and landscape on the production of greenhouse gases.
Approach
At the Landscape Biomass Project we are interested in measuring emissions of CH4, CO2, and N2O from soil under different biomass cropping systems across an agricultural landscape. We are looking at two annual systems (corn on corn and a double crop of sorghum and triticale) along with a perennial monoculture (switchgrass). Gas measurements are taken within these cropping systems at three different topographic positions: an upland position (summit), and two lower positions (backslope and toeslope). Sampling occurs several times through the growing season to capture gases generated by soil microbes and CO2 produced through plant root respiration.
