Diurnal Greenhouse Gas Emissions Under Different Carbon and Nitrogen Input from Cover Crops.

Agricultural systems are under continuous pressure for reducing greenhouse gas (GHG) emission without compromise crop productivity. The impact of organic crop production that uses animal manure as a nutrient source on GHG emission remains uncertain. In this study, we are investigating soil GHG emissions from a field transitioning from a grassland into an organic grain production system (corn/sorghum/soybeans) near College Station, TX. Changes in nitrogen (N) and carbon (C) inputs due to tillage practices (Conventional- and no-tillage) and cover crops were investigated as part of this study. Carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) emissions were continuously measured using eight automated soil chambers at 30-minute intervals. The chambers were connected to an integrated gas analyzer system that connected a LI-COR 8100A (LI-COR Biosciences, Lincoln, NE, USA) CO₂ analyzer with a Picarro G2508 gas concentration analyzer (Picarro Inc., Santa Clara, CA, USA) in parallel. Dissolved soil organic C and N, nitrate-N (NO₃^--N) and ammoniacal-N (NH₄⁺-N) were correlated to GHG emissions. Our hypothesis is that conventional tillage that incorporates plant residues, can increase organic matter decomposition and therefore, increasing GHG emissions compared to no-tillage systems. The results from this project are significant in determining GHG emissions in organic cropping systems that have been poorly studied. It will also provide insights of the environmental factors driving GHG emission in diurnal and seasonal time-scales that will help in improving estimations of C and N fluxes from agricultural systems. Further results will be presented at the conference.