Carbon Dioxide and Nitrous Oxide Emissions Impacted by Bioenergy Sorghum Management

Abstract

Modern bioenergy feedstocks, such as bioenergy sorghum [Sorghum bicolor (L.) Moench], are being developed to supply future cellulosic biofuel demands. How these cropping systems impact greenhouse gas (GHG) emission of CO2 and N2O from the soil is unknown and field research is necessary to elucidate the effects of agronomic management practices on soil trace gas emissions. We studied the effects of N fertilization (0 vs. 280 kg urea‐N ha−1), residue management (0 vs. 50% of sorghum biomass returned), crop sequence (corn [Zea mays L.]–sorghum vs. sorghum–sorghum), and their interactions on CO2 and N2O emissions from bioenergy production scenarios on a Weswood (fine‐silty, mixed, superactive, thermic Udifluventic Haplustept) silty clay loam soil in central Texas. Gas fluxes were measured approximately weekly throughout the 2010 and 2011 growing season and at a reduced rate during the fallow season with a photoacoustic gas analyzer integrated with a static chamber. Overall, CO2 and N2O fluxes were relatively higher than those observed by others in the United States despite drought conditions throughout much of 2010 and 2011. Highest emissions of both gases were observed during the growing season, often following a precipitation–irrigation event and shortly after N fertilization. Residue return increased cumulative CO2 emissions each year, probably due to increased heterotrophic microbial activity. Nitrogen addition significantly increased cumulative emissions of N2O both years but only impacted cumulative CO2 emissions in 2011. While crop rotation impacted biomass yield, it had no significant effect on cumulative CO2 or N2O emissions. Additional research is needed to identify the optimal N and residue application rates that provide high yields with minimal soil GHG emissions and aid in sustaining long‐term soil quality.

Dedicated Energy Crops and Crop Residues for Bioenergy Feedstocks in the Central and Eastern USA

“…This competition is intensified with the additional challenge of feeding an expected world population of 9 billion by the middle of this century [117,118]. One way to alleviate traditional versus bioenergy crop competition is to grow bioenergy crops during fallow periods that do not conflict with traditional crops.…”

The interaction of seasonal rainfall and nitrogen fertiliser rate on soil N2O emission, total N loss and crop yield of dryland sorghum and sunflower grown on sub-tropical Vertosols

“…Ramu et al (2012) reported greater N 2 O emissions from a welldrained Alfisol than from an adjacent poorly-drained Vertisol, demonstrating that factors other than drainage can affect cumulative N 2 O emitted. Soil N 2 O emissions from N-fertilised sorghum in tropical and sub-tropical regions have been reported from Oxisols (Mosier et al 1998;De Antoni Migliorati et al 2015) an Inceptisol (Storlien et al 2014), an Entisol (Welzmiller et al 2008) and an Alfisol (Ramu et al 2012), but only Ramu et al (2012) has documented N 2 O emissions from a Vertisol in central India. The potential for denitrification losses of N as N 2 O and N 2 is high, particularly if high intensity rainfall occurs early in the growing season (Schwenke et al 2015).…”

Sustainable production of sweet sorghum for biofuel production through conservation agriculture in South Africa

“…Conversely, the warm climate also increases soil GHG emissions (Xu & Luo, 2012). Therefore, production of biofuel crops will compromise the main goal of biofuel production if it increases the net GHG emissions (Storlien, Hons, Wight, & Heilman, 2014). Apart from the climate, soil GHG emissions are affected by different agronomic practices (Adviento-Borbe, Haddix, Binder, Walters, & Dobermann, 2007), such as tillage, crop rotation, fertilization, residues return, and irrigation.…”

“…Crop residue retention increased CO 2 emissions compared with treatments where residues are removed (Dendooven et al, 2012;Storlien et al, 2014). Storlien et al (2014) conducted a study using two levels of residue retention, 0% and 50%, along with fertilization under bioenergy sorghum production, and reported that 50% residue retention increased CO 2 by 12% compared with treatments without residue retention. Crop residues are a source of carbon which can increase microbial activities (Ussiri & Lal, 2009) and that is the reason why their retention increased CO 2 .…”