Response of surface GHG fluxes to long-term manure and inorganic fertilizer application in corn and soybean rotation.

This study was conducted to investigate the impacts of dairy manure and inorganic fertilizer on soil surface greenhouse gases (GHG) [carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)] fluxes from soils managed under corn (Zea mays L.)-soybean (Glycine max L.) rotation. The experiment was established on a silty loam soil, and the treatments included three manure application rates [phosphorus based recommended rate (low manure, LM), nitrogen based recommended rate (medium manure, MM) and two times recommended nitrogen rate (high manure, HM)], two inorganic fertilizer levels [recommended fertilizer (medium fertilizer, MF) and high rate of fertilizer (HF)], and control (CK) replicated four times. Soil GHG fluxes were monitored once a week during the growing season for 2015 and 2016. Data from this study showed that there were not any significant impacts from manure and inorganic fertilizer applications on the annual CH4 fluxes in 2015 and 2016. However, annual soil surface CO2 fluxes were increased by manure treatments compared to inorganic fertilizer treatments in both the years. In contrast, manure treatments decreased N2O fluxes, but significantly increased net GWP than the fertilizer treatments in 2016. In general, higher manure and fertilizer rates resulted in higher annual GHG emissions compared to lower manure and fertilizer rates in both years. Data from this study showed that HF application in crops can be detrimental for the environment by emitting higher GHG emissions, therefore, improved application strategies for manure and fertilizer management need to be explored to avoid any negative environmental impacts.