Quantifying Soil Greenhouse Gas Emissions And Soil Carbon Storage To Determine Best Management Practices In Agroecosystems

Intensive agriculture, coupled with an increase in nitrogen fertilizer use, has contributed significantly to the elevation of atmospheric greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Rising GHG emissions usually mean a decrease in soil carbon. Currently, soil C is twice that of all standing crop biomass, making it an extremely important player in the C cycle. Fortunately, agricultural management practices have the potential to reduce agricultural GHG emissions whilst increasing soil C. Management practices that impact GHG emissions and soil C include various tillage practices, different N fertilization amounts and treatments (synthetic N, cattle manure, or a combination of both), the use of cover crops, aeration, and water levels. Employing agricultural best management practices (BMPs) can assist in the mitigation and sequestration of CO2, N2O and soil C. Measuring soil carbon storage and GHG emissions and using them as metrics to evaluate BMPs are vital in understanding agriculture\u27s role in climate change. The objective of this research was to quantify soil carbon and CO2 and N2O emissions in agroecosystems (dairy, crop, and meat producing farms) under differing management practices. Three farms were selected for intensive GHG emissions sampling: Shelburne Farm in Shelburne, VT, a dairy in North Williston, VT, and Borderview Farm in Alburgh, VT. At each site, I collected data on GHG (CO2 and N2O) emissions and soil carbon and nitrogen storage to a depth of 1 meter. Soil emissions of CO2 and N2O were taken once every two weeks (on average) from June 2015 through November, 2015 using static flux chambers and a model 1412 Infrared Photoacoustic Spectroscopy (PAS) gas analyzer (Innova Air Tech Instruments, Ballerup, Denmark). Fluxes were measured on 17 dates at Shelburne Farms, 13 dates at the Williston site, and 13 dates in the MINT trial. Gas samples were taken at fixed intervals over a 10-14 minute time frame, with samples normally taken every one or two minutes. I also measured soil carbon to a depth of 1m in six BMPs at Borderview Farm. Overall, I found that manure injection increased N2O and CO2 emissions, but decreased soil C storage at depth. Tillage had little to no impact on N2O emissions, except at Shelburne Farms, where aeration tillage decreased N2O emissions (marginally significant, P \u3c 0.1). No-till did, however, decrease CO2 emissions relative to other conservation tillage practices (strip and vertical tillage) but we were unable to detect a significant change in soil C due to tillage practices. At Borderview farm, N2O emissions increased with soil NO3 and soil moisture, while CO2 emissions increased with soil temperature and nitrate. At Williston, CO2 emissions only increased with temperature; at Shelburne CO2 emissions increased with nitrate. N2O fluxes at Shelburne and Williston were not associated with any of the measured covariates

Effects of Irrigation and Manure Additions on Soil Nitrous Oxide Emissions in No-Tillage, Continuous Corn System

With human population projection estimates pointing to nine billion by year 2050, the importance of maintaining Earth’s basic ecosystem services has quickly become increasingly important. Supporting this expanding population with enough food, fiber, and fuel has intensified demands on agricultural land and other natural resources (Haile-Mariam et al., 2008). Intensive agriculture, coupled with an increase in nitrogen (N) fertilizer use, has contributed significantly to the elevation of atmospheric greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)(Haile-Mariam et al., 2008). These three GHGs differ noticeably in their atmospheric concentrations, residence time in the atmosphere, and global warming potential (GWP) (Leibig et al., 2012). Of the three GHGs, N2O is present in the lowest atmospheric concentrations but has the greatest GWP, at 298 times that of CO2 (IPCC, 2007; NOAA, 2011). The objective of this research is to characterize soil N2O emissions following one irrigation event at full irrigation or deficit irrigation rates in a continuous corn, no-tillage (till) system under different N fertilization treatments (commercial N, cattle manure). Full irrigation is defined as the amount of water needed to meet 100% of a plant’s water needs, and the deficit irrigation rate used here represents 60% of full irrigation. Employing best management practices (BMPs), as it pertains to agricultural irrigation levels, is important in assisting in the mitigation of the GHGs listed

Benefits and tradeoffs of reduced tillage and manure application methods in a Zea mays silage system

A critical question is whether there are agricultural management practices that can attain the multiple management goals of increasing yields, preventing nutrient losses, and suppressing greenhouse gas (GHG) emissions. No‐till and manure application methods, such as manure injection, can enhance nutrient retention, but both may also enhance emissions of nitrous oxide (N2O), a powerful GHG. We assessed differences in soil N2O and carbon dioxide (CO2) emissions, nitrate and ammonium retention, and crop yield and protein content under combinations of vertical‐till, no‐till, manure injection, and manure broadcast without incorporation in a corn (Zea mays L.) silage system. During the growing seasons of 2015–2017, GHG emissions and soil mineral nitrogen (N) were measured every other week or more frequently after management events. Crop yield and protein content were measured annually at harvest. No‐till reduced CO2 emissions but had no impact on N2O emissions relative to vertical‐till. Manure injection increased N2O and CO2 emissions, with the magnitude of this effect being greatest for 1 mo post‐application. Manure injection also increased soil ammonium and nitrate but did not increase yield or crop quality relative to broadcast application. Similarly, tillage did not affect crop yield or protein content. Despite the tradeoffs between mineral N retention and elevated GHG emissions, manure injection in no‐till systems benefits farmers by reducing soil carbon losses as CO2, retaining mineral N, and maintaining crop yields and quality