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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #311268
Title: Effects of delayed winter harvest on biomass yield and quality of napiergrass and energycane

Author
item Knoll, Joseph - Joe
item JOHNSON, JENNIFER - Auburn University
item HUANG, PING - Auburn University
item LEE, R - University Of Georgia
item Anderson, William - Bill

Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2015
Publication Date: 7/1/2015
Citation: Knoll, J.E., Johnson, J.M., Huang, P., Lee, R.D., Anderson, W.F. 2015. Effects of delayed winter harvest on biomass yield and quality of napiergrass and energycane. Biomass and Bioenergy. 80:330-337.

Interpretive Summary: Napiergrass (Cenchrus purpureus Schumach) and energycane (Saccharum hyb.) are high-yielding perennial grasses that are well-suited for biomass production in the southeast USA. The purpose of this study was to determine the effects of delayed winter harvest on biomass yield and quality of these two grasses. The study was conducted on two adjacent sites near Midville, GA. Each grass was harvested at three different times: December, January, or February to compare the quantity and quality of the harvested biomass. Dry matter (DM) yields were measured by mechanical harvesting, and a sample of biomass was taken from each harvest for determination of ethanol production by a process called simultaneous saccharification and fermentation (SSF). In this process, biomass is treated with dilute acid at high temperature to partially break it down. Then enzymes are added to break the cellulose into simple sugars. Yeast is added at the same time to ferment those sugars into ethanol. Biomass moisture and nutrient composition (N, P, K, and ash) were also determined for each harvest. Energycane yields were relatively stable from December to January, but then declined, while napiergrass yields tended to decline sharply from December to January, most likely due to leaf drop. Moisture content of both grasses was affected by harvest time, but only modest reductions were observed. Nitrogen, K, and ash content tended to decrease with later harvesting, but sometimes appeared to increase due to changes in the ratio of other biomass components. Multiplying biomass yield by its nutrient content allows us to estimate how much of a particular nutrient was removed from the soil. Delaying harvest of napiergrass from December to January returned an average of 144 kg ha-1 N to the soil, mainly through leaf drop, while energycane only returned an average of 54 kg ha-1 N by delaying harvest to February. On a per-unit basis, ethanol production from SSF of napiergrass was relatively unaffected by harvest date, but energycane tended to produce less ethanol per unit of biomass in later harvests. In conclusion, standing biomass of these grasses can be stored in the field into the winter months. Some loss of total biomass and total ethanol yields should be expected with delayed harvest, but some N and other nutrients would be returned to the soil to benefit the next crop.

Technical Abstract: Napiergrass (Cenchrus purpureus Schumach) and energycane (Saccharum hyb.) are high-yielding perennial grasses that are well-suited for biomass production in the southeast USA. The purpose of this study was to determine the effects of delayed winter harvest on biomass yield and quality of these two grasses. The study was conducted on two adjacent sites near Midville, GA. Each site used a split-plot design with four replications, with species as the main plot, and harvest times (December, January, or February) as sub-plots. Dry matter (DM) yields were measured by mechanical harvesting, and a sample of biomass was taken from each harvest for determination of ethanol production by simultaneous saccharification and fermentation (SSF). Biomass moisture, N, P, K, and ash mass fractions were also determined for each harvest. Energycane yields were relatively stable from December to January, but then declined, while napiergrass yields tended to decline sharply from December to January, most likely due to leaf drop. Moisture mass fraction of both grasses was affected by harvest time, but only modest reductions were observed. Mass fractions of N, K, and ash tended to decrease with later harvesting, but sometimes increased due to changes in biomass composition. Delayed harvest of napiergrass from December to January returned an average of 144 kg ha-1 N to the soil, while energycane only returned an average of 54 kg ha-1 N by delaying harvest to February. Ethanol production from SSF of napiergrass was relatively unaffected by harvest date, but energycane tended to produce less ethanol in later harvests.