Student Research: How Harvest Timing Influences Switchgrass Production

Agronomy Student Joey Geisler checks plant growth stage (left) and uses a frequency frame to determine the number of tillers in switchgrass stand.
Agronomy Student Joey Geisler checks plant growth stage (left) and uses a frequency frame to determine the number of tillers in switchgrass stand.

Student Research: How Harvest Timing Influences Switchgrass Production

By Joey Geisler, Agronomy Student, Department of Agronomy and Horticulture, University of Nebraska-Lincoln

Advisors: Robert Mitchell, USDA-ARS Grain, Forage, and Bioenergy Research Unit; Daren Redfearn, Nebraska Extension Forage and Crop Residue Systems Specialist

The use of switchgrass as a potential crop source of large amounts of biomass was further examined in this study. Greater biomass yield is needed as the amount of pastureland decreases due to increased grain production. A native plant to Nebraska and the Great Plains, switchgrass is easily grown in Nebraska with the right management practices.

Switchgrass has many uses from being a forage crop to a bio-energy crop. Like corn, switchgrass uses C4 photosynthesis so it is very efficient at using carbon and making new cells rapidly. Also like corn, switchgrass takes up many nutrients and must be fertilized annually with nitrogen in order to produce continuous biomass. While it is known that switchgrass can produce a lot of biomass, it isn’t known when it is best to harvest it to achieve maximum production. We wanted to find out how harvest timing affects the growth of switchgrass.

Factors Contributing to Optimum Biomass Yield

Chart of average biomass production over three years
Figure 1. Weekly measurements of average switchgrass biomass production (kg/ha) over a three-year period.

As overall plant frequency shows, after being harvested for multiple years, switchgrass produces fewer plants. But, if you look at the amount of biomass over time, the amount present doesn’t change much. This shows why switchgrass is ideal for biomass production since the stands continue to produce consistent yields from one seeding year to another.

It was also found that August was the best month to harvest switchgrass. In particular, the third week in August produced the most biomass of any other week in the three years of this study. If you look at the frequency of the plants though, most plots had fewer plants in them in 2006 than in 2004. This shows that once established, switchgrass tends to have fewer tillers, but has the potential of producing high biomass if managed correctly. After August, every month that harvest was delayed resulted in an average yield loss of 784.46 kg/ha (700 lb/ac) through November (Figure 1).

Conclusions

From this study, we can conclude that switchgrass has high potential, but must be managed correctly in order to ensure high yields and a successful crop. Little management is needed with the only limiting nutrient being nitrogen. If large quantities of biomass are desired, the timing of switchgrass harvest is critical. In Nebraska it should be harvested from late August to early September to avoid large yield losses. Once switchgrass is established in the first year growing it, it can produce high forage yields using minimal inputs if managed correctly.

About the Author

Joey Geisler is a junior at the University of Nebraska-Lincoln majoring in agronomy and horticulture. He grew up on a family farm near Hooper.


Support for this project was provided by a grant from the USDA NIFA FY15 Agriculture and Food Research Initiative: Education and Literacy Initiative–Undergraduate Experiential Learning Fellowships Program "Developing Research and Extension Skills of Students in Integrated Agronomic Systems."

Find more stories about student research conducted through this project at Developing Undergraduate Research and Extension Expertise in Integrated Agronomic Systems.