Dynamics of Soil Carbon and Nitrogen from a Perennial Bioenergy Cropping System.

The purpose of this research was to study perennial energy cropping system with energy cane (Saccharum spp.) and elephant grass (Pennisetum purpureum (L.) Schum.) on marginal lands and analyze the soil organic carbon and nitrogen dynamics with nitrogen (N) fertilizer applications and winter cover crops. Data was collected for four years (2011-2014) from Fort Valley State University, GA research plots. The treatments consisted of two perennial grasses, one winter cover crop (clover) and three N fertilization rates (0,100 and 200 Kg N/ha) with four replications. Soil Samples were collected from two depths (0-15 and 15-30 cm) and were analyzed for soil organic carbon (SOC) and total soil total nitrogen (STN). The average SOC and STN were found higher in soil with elephant grass (14.24 mg C/ha and 1.502 mg N/ha) than energy cane (13.53 mg C/ha and 1.442 mg N/ha). Soil surface depth (0-15 cm) has higher SOC and STN compared to subsurface (15-30 cm).  Winter cover crop (clover) is found to be significant in both carbon sequestration and nitrogen fixation compared to control (no cover). The application of nitrogen fertilizers (100 kg and 200 kg N/ha) was not statistically different with no fertilizer, both for soil organic carbon and soil total nitrogen. Soil organic carbon (SOC) was higher in second (2012) and third year (2013) of planting in comparison to the establishment year (2011), which significantly decreased in fourth year (2014) and was found statistically non-significant with establishment year. Soil total nitrogen is significantly higher in second, third and fourth year compared to establishment year. It is concluded that growing perennial bioenergy crops sequesters significant organic carbon and fixes nitrogen into soil. Planting winter leguminous cover crops is beneficial for higher carbon sequestration and nitrogen fixation on soil whereas the effect of applying inorganic N fertilizer needs further evaluation.