Nitrous oxide emissions during establishment of eight alternative cellulosic bioenergy cropping systems in the North Central United States

Abstract

Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land-use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N 2 O emissions and potential environmental drivers of these fluxes from a three-year establishment-phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn-soybean-canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three-year N 2 O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N 2 O-N ha À1 yr À1 for the annuals with continuous corn > corn-soybean-canola rotation and 1.1 to 6.3 kg N 2 O-N ha À1 yr À1 for perennials. Nitrous oxide peak fluxes typically were associated with precipitation events that closely followed fertilization. Bayesian modeling of N 2 O fluxes based on measured environmental factors explained 33% of variability across all systems. Models trained on single systems performed well in most monocultures (e.g., R 2 = 0.52 for poplar) but notably worse in polycultures (e.g., R 2 = 0.17 for early successional, R 2 = 0.06 for restored prairie), indicating that simulation models that include N 2 O emissions should be parameterized specific to particular plant communities. Our results indicate that perennial bioenergy crops in their establishment phase emit less N 2 O than annual crops, especially when not fertilized. These findings should be considered further alongside yield and other metrics contributing to important ecosystem services.

Intercropping with Switchgrass Improves Net Greenhouse Gas Balance in Hybrid Poplar Plantations on a Sand Soil

“…§ Compares the values between sampling time 1 (April to June) and time 2 (July to Sep) at P < 0.05. Growing season emission factors (N EF ) were similar for IC and SM which is consistent with the findings of others (Evers et al, 2010;Nikiema et al, 2011;Schmer et al, 2012;Wile et al, 2014;Oates et al, 2016). In 2012 when fertilization began N EF for the IC and SM averaged 0.4% (0.90 kg fertilizer N ha -1 ), then increased significantly to 0.87 and 1.74% (2.0 and 3.9 kg fertilizer N ha -1 ) in 2013 then declined to 0.75% (1.7 kg fertilizer N ha -1 ) in 2014 for the growing season.…”

“…Adler et al (2007) reported soil N 2 O emissions are the largest source of greenhouse gas emissions associated with bioenergy crop production. Oates et al (2016) found N 2 O emissions from annual crops (corn, Zea mays L.; soybean, Glycine max L. Merr.…”

Inhibition of microbial biofuel production in drought-stressed switchgrass hydrolysate

“…Switchgrass was sourced from ARL-346 in both 2010 and 2012, and ARL-115 in 2013. The main soil at ARL is Plano silt-loam (fine-silty, mixed, superactive, mesic Typic Argiudoll); a deep (>1 m), well-drained mollisol developed over glacial till and formed under tallgrass prairie [13]. Mean annual temperature and precipitation are 6.9 °C and 869 mm, respectively [34, 35].…”

“…Corn stover is currently the feedstock of choice due to its current widespread availability and economic potential [2, 10]. Switchgrass is a promising perennial bioenergy crop that can be grown on marginal lands [11] and provides superior environmental benefits compared to corn, including support for biological diversity [12], lower nitrous oxide emissions [13], and improved soil properties [14, 15]. In order to investigate how interannual variation in precipitation influences the processing characteristics and microbial fermentation of these two important biofuel feedstocks, we compared switchgrass and corn stover that were harvested following the 2012 Midwestern US drought to those harvested during two non-drought years with different precipitation patterns (2010 and 2013).…”

Pre-senescence Harvest of Switchgrass Inhibits Xylose Utilization by Engineered Yeast

“…Pretreated samples were subjected to high solids enzymatic hydrolysis (6% glucan loading) followed by ethanolic fermentation using an engineered xyloseutilizing yeast strain, S. cerevisiae 424A. (Oates et al, 2016;Ong et al, 2016), and the mean temperature and precipitation were 5.6 • C and 782 mm, respectively for the entire year of 2014, and were 15.3 • C and 470 mm, respectively for the growing season from 22 May to 13 November 2014. Switchgrass was planted in June 2008, and samples were manually harvested in 2014 from five replicate field plots (R1 -R5), roughly every 2 weeks from peak biomass (20 August 2014) until after the killing frost (7 November 2014).…”