Response of Soil Greenhouse Gas Fluxes and Soil Properties to Nitrogen Fertilizer Rates under Camelina and Carinata Nonfood Oilseed Crops

Abstract

Camelina (Camelina sativa L.) and carinata (Brassica carinata) are nonfood oilseeds known for their potential as a promising biofuel feedstock; however, their associated greenhouse gas (GHG) emissions under different rates of nitrogen (N) fertilizer has not been well studied. This study was conducted to evaluate the impacts of N fertilization rates on selected soil properties and soil surface GHG fluxes from camelina and carinata fields in South Dakota, USA. The experimental design comprised of four N rates (0, 28, 56, 84 kg N ha−1) in 2014, 2015 and 2016, replicated four times. At harvesting, soil samples were collected in all years at both fields to measure pH, electric conductivity, total nitrogen, and soil organic carbon. The GHG fluxes were taken biweekly from 2014 to 2016 using a static chamber. Our results demonstrated that increasing N fertilization rates resulted in decreased soil pH in the carinata field in 2015 and increased soil organic carbon and electrical conductivity in the camelina field in 2014. Total nitrogen was not affected by N fertilization rates in all years. For the GHG gases, the CO2 and CH4 fluxes were not significantly influenced by the application of N fertilization rates in all years. However, the N2O flux significantly increased with the increasing of N fertilization rates at both fields in 2014 and 2015. In general, the effect of N fertilization rates on soil properties and GHG fluxes in both oilseed crops were similar. Data from this study showed minimal responses of soil properties to N fertilization rates. Increasing N fertilizer application in camelina and carinata crops resulted in higher N2O emissions. Therefore, improved application strategies for N fertilizer management in camelina and carinata crops need to be explored to avoid any negative environmental impacts.