Measurement and simulation of nitrous oxide fluxes from perennial forage grasses and annual crops amended with pig manure and inorganic fertilizer

Crop and nutrient management on agricultural soils are essential considerations for mitigating greenhouse gas emissions in our environment. This thesis aimed to simulate and compare nitrous oxide (N2O) fluxes from perennial forage grasses (FPP) and annual crops (ANN) amended with solid pig manure (SPM), liquid pig manure (LPM) and inorganic urea fertilizer (FER). Two field studies were carried out at different sites Carman and Carberry, Manitoba, Canada. At Carman, N2O fluxes were monitored from FPP following its termination and restoration. At the Carberry, N2O fluxes were measured from LPM applied to soil annually at a rate of 56,000 L ha-1, FER applied at the equivalent rate as total available N from the LPM and un-amended control (CON) plots. At Carberry, in 2011 and 2014 when applied manure N was low, emission factor and emission intensity from LPM was one-half of that from FER. At Carman, the result showed that the termination of perennial forage grasses in combination with applied manure leads to increased soil nitrogen content and N2O fluxes. However, when FPP were replanted in 2014, N2O emission from FPP was 30% less than that from ANN treatments. The data from the Carman site were used to evaluate the performance of the DeNitrification-DeComposition (DNDC) model to predict soil moisture and N2O fluxes. The DNDC model output compared well with the field observed values on the ANN (cumulative N2O flux and daily soil moisture Nash–Sutcliffe efficiency (NSE) > 0.7) but not on the FPP (cumulative N2O flux and daily soil moisture NSE < 0.2). In spite of the wide use of the DNDC model, some routines in the model still needs work as seen on the FPP. In conclusion, perennial forage grass planted in rotation with annual crops can provide N saving benefits, but the N would be lost when the forage grasses are converted to annual cropland. Also, LPM can provide nutrient to crop more efficiently than FER, as less N2O was emitted to produce a unit grain of wheat, but the