Comparative Study of Soil Surface Greenhouse Gas Fluxes from Energy Cane and Napier Grass Fields in Relation to Soil Temperature, Soil Moisture and Nitrogen Amendments.

Perennial grasses like energy cane (Saccharum spp) and napier grass (Pennisetum purpureum (L.) Schum.) are lignocellulosic bioenergy crops and are considered potential alternatives for sustainable bioethanol production. While it is important to establish a high biomass production system with low inputs it is important to study greenhouse gas fluxes to assess the environmental impacts of one over other. There are limited studies on the emission of greenhouse gases like nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) from these crops. Current study was conducted at Fort Valley State University Research Farm, Fort Valley, GA from 2011 to 2014 with weekly record of soil temperature (ST), soil moisture (SM) and fluxes from energy cane and napier grass fields. The nitrogen (N) was amended with leguminous cover crop clover (Trifolium incarnatum L.) and inorganic N fertilizers (0, 100 and 200 kg N ha^-1). The data showed that there was no significant difference among two crops for individual fluxes of CO₂, N₂O and CH₄ (p≤ 0.05). Energy cane N₂O flux rate was significantly affected by ST, SM, as well as N amendments. The CO₂ flux showed significant relationship with ST and SM, whereas the CH₄ flux was significant only in response to ST. The N₂O flux from napier grass field was found to have significant response only with N amendments. The CO₂ flux showed significant response to ST and SM while CH₄ flux showed significant response only with ST. The result of analysis satisfied the hypothesis that fluxes from two crops did not vary, however could not satisfy the hypothesis that all the factors (ST, SM and N) were equally responsible for CO₂, N₂O and CH₄ fluxes.