Distribution of Structural Carbohydrates in Corn Plants Across the Southeastern USA

Abstract

Quantifying lignin and carbohydrate composition of corn (Zea mays L.) is important to support the emerging cellulosic biofuels industry. Therefore, field studies with 0 or 100 % stover removal were established in Alabama and South Carolina as part of the Sun Grant Regional Partnership Corn Stover Project. In Alabama, cereal rye (Secale cereale L.) was also included as an additional experimental factor, serving as a winter cover crop. Plots were located on major soil types representative of their respective states: Compass and Decatur soils in Alabama and a Coxville/Rains-Goldsboro-Lynchburg soil association in South Carolina. Lignin and structural carbohydrate concentrations in the whole (above-ground) plant, cobs, vegetation excluding cobs above the primary ear (top), vegetation below the primary ear (bottom), and vegetation from above the primary ear including cobs (above-ear fraction) were determined using near-infrared spectroscopy (NIRS). The distribution of lignin, ash, and structural carbohydrates varied among plant fractions, but neither inclusion of a rye cover crop nor the stover harvest treatments consistently affected carbohydrate concentrations within locations. Total precipitation and average air temperature during the growing season were strongly correlated with stover composition indicating that weather conditions may have multiple effects on potential biofuel production (i.e., not only yield but also stover quality). When compared to the above-ear fractions, bottom plant partitions contained greater lignin concentrations. Holocellulose concentration was consistently greater in the above-ear fractions at all three locations. Data from this study suggests that the above-ear plant portions have the most desirable characteristics for cellulosic ethanol production via fermentation in the southeastern USA.

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

“…Other research concluded that harvesting the upper half of standing stover with cobs produced the highest quality feedstock and maintained soil productivity as determined by the soil management assessment framework (SMAF) [70,71]. Total precipitation and average air temperature during the growing season were strongly correlated with stover chemical composition, and the above ear portion of stover was more desirable due to lower lignin and higher cellulose content [72]. However, stover should not be removed if grain yield is less than 11 Mg ha −1 [73].…”

Influence of Corn Residue Harvest Management on Grain, Stover, and Energy Yields

“…This increase in HHV is likely due to drought-induced lignocellulosic changes in the plant reported by [7]. With adequate rainfall, the plant prioritizes nutrient and photosynthetic resources into grain production as demonstrated by harvest index values ranging from 41 % to 48 % ( Table 2).…”

“…In the study of Johnson et al [6], nutrient recycling was greatest for the stover's lower portion (below ear); likewise, retaining this portion on the field would lead to decreased nutrient replacement costs. In Mourtzinis et al [7], the above ear portion of stover along with the cob was found to have the greatest holocellulose content. Greater holocellulose contents were desirable because they contributed to greater theoretical ethanol production.…”

“…A number of studies, with a focus primarily within the U.S. Corn Belt, have examined the influence of corn stover removal on soil quality parameters [3][4][5]; additional studies are reported within this special issue. Emerging studies are addressing the mineral recycling and downstream ethanol impact by varied stover removal [6,7]. In the study of Johnson et al [6], nutrient recycling was greatest for the stover's lower portion (below ear); likewise, retaining this portion on the field would lead to decreased nutrient replacement costs.…”

“…To meet this need a consortium of USDA-ARS researchers with university partners and engineers from the Idaho National Laboratory developed a multi-location, trans-disciplinary partnership to quantify and model the sustainability of corn stover harvest [13,14]. The results of this study are presented within this special issue, including plant characteristics such as ash content and lignocellulosic content [7]. The specific objective presented here were (1) to quantify the gross energy distribution in various corn stover fractions when harvested for bioenergy production and (2) to determine the impact of annual residue removal on these properties in subsequent years.…”