Growing and Harvesting Switchgrass 

for Ethanol Production in Tennessee

Clark D. Garland, Professor, Agricultural Economics 

Chair, Biofuels Farmer Education Team*

S

witchgrass is a warm-season 

perennial grass native to 

North America. The plant can 

reach heights up to 10 feet with an 

extensive root system. Once established, switchgrass well-managed 

for biomass should have a productive life of 10-20 years. Within the 

stand, switchgrass is an extremely 

strong competitor. However, it is 

not considered an invasive plant. 

Switchgrass adapts well to a variety 

of soil and climatic conditions. It is 

most productive on moderately well 

to well-drained soils of medium 

fertility and a soil pH at 5.0 or 

above. The high cellulosic content 

of switchgrass makes it a favorable 

feedstock for ethanol production. 

It is anticipated that switchgrass 

can yield sufficient biomass to 

produce approximately 500 gallons of ethanol per acre. While 

the Tennessee Biofuels Initiative 

includes a demonstration plant to 

make ethanol from switchgrass, the 

market for switchgrass as an energy 

crop remains limited. Producers 

will likely need to be located within 

30 to 50 miles of a cellulosic ethanol plant. Producing switchgrass for 

energy generally occurs under some 

form of contractual arrangement 

with the end-user. To reap potential 

benefits from using switchgrass 

for cellulosic ethanol production, 

the system of production must be 

profitable for farmers and energy 

producers, as well as cost effective 

for consumers.

Recommended Varieties

There are two main types of 

switchgrass. The upland varieties 

usually grow 5 to 6 feet tall and are 

adapted to the Midwest. Lowland 

varieties are most adapted for the 

South and grow from 7 to 10 feet 

tall. The most common lowland 

varieties adapted to Tennessee are 

Alamo and Kanlow and both are 

currently recommended by UT. 

Alamo has been used in the majority of recent research conducted 

by the University of Tennessee on 

switchgrass for biomass. 

Henry County Extension Director, Ken Goddard (at left), discusses switchgrass 

production with farmers.

SP701-A

UTBiofuelsInitiative
Recommended Seeding Rate

Switchgrass seed is very small 

and much of it will not germinate 

right after it is harvested. However, 

aging, treating with water and chilling temperatures (stratification) or 

storing it in warm conditions will 

break dormancy. When establishing 

switchgrass, buying quality seed is 

an important consideration. Switchgrass seed are normally sold on the 

basis of pure live seed (PLS). The 

germination rate will vary. Therefore, it is critical to plant according 

to the PLS. In calibrating seeding 

equipment, take into account the 

percentage of pure seed and the 

germination rate. UT recommends 

6 pounds of PLS per acre.

Fertilizer and pH 

Recommendations

Although switchgrass is adapted 

to nutrient-deficient soils, soil 

fertility is important and soil testing is recommended to determine 

pH and nutrient availability. If soil 

test values are medium or high in 

phosphorous (P) and potassium (K), 

no additional P205 or K20 is recommended. If the soil test is low in P, 

an annual application of 40 pounds 

of P205 per acre is recommended. If 

the soil is low in K, an annual application of 80 pounds of K20 should 

be applied per acre. If the soil pH 

is 5.0 or above, no lime is recommended. These recommendations 

are for long-term reasonable yields 

of switchgrass for biomass, with 

switchgrass harvested after a killing frost over a period of 10 years. 

Being a perennial, switchgrass is 

thought to translocate much of the 

aboveground nutrients back into the 

crown root system, resulting in very 

low input needs after establishment.

Nitrogen should not be applied 

until the stand is established and 

weeds controlled. In the first year, 

do not apply nitrogen. It increases 

competition from annual grasses 

and broadleaf weeds. Beginning 

in the spring of the second year, 

60 pounds of nitrogen per acre are 

recommended (Table 1).

Planting Date

Planting dates can range from 

late April to mid June. Switchgrass 

is a warm-season grass and establishes and grows best under warm 

conditions.

Planting Methods

Switchgrass can be planted 

into a tilled seedbed or no-tilled. 

It appears no-till planting with a 

no-till drill in fields not bedded 

from past row crops is the ideal 

way to plant. Switchgrass should 

be planted when sufficient soil 

moisture is available for emergence 

of the seeds. A planting depth of 1⁄4 

to no deeper than 1⁄2 inch is critical with good seed coverage at that 

Table 1.

Soil Test Recommendations for Establishment 

and Maintenance of Switchgrass for Biomass

Practice

Nitrogen Phosphate (P2

O5) Potash (K20)

Soil Test Levels*

(NT) L M H L M H

1. Establishment Year 0 40 0 0 80 0 0

2. Maintenance Year 60 40 0 0 80 0 0

*

NT = Not Tested L = Low M = Medium H = High

Alamo Switchgrass seeds are quite small with more than 400,000 seeds per pound.

UTBiofuelsInitiative 2
depth. This is usually easier to 

achieve in no-tilled soil conditions. 

The drill should have small seed 

boxes suitable for accurately metering switchgrass.

Weed Control

In the establishment year, 

switchgrass does not compete 

well with grasses such as fescue, 

crabgrass, johnsongrass, etc. and 

broadleaf weeds. Appropriate weed 

control measures vary greatly 

according to previous cropping 

history and specific weed varieties. 

Carefully evaluate fields before and 

after planting and check with an 

Extension agent for control options.

Few herbicides are labeled for 

weed control in switchgrass on 

non-Conservation Reserve Program 

(CRP) land in Tennessee. Therefore, 

it is critical to control weeds prior 

to planting. Most often, a glyphosate herbicide (e.g., Roundup®, 

Gly-4 Plus®) is used to kill existing 

cover. The guideline switchgrass 

budgets include two burndowns 

with a glyphosate herbicide. The 

preferred method to establish 

switchgrass in a pasture or hay field 

is to spray in the fall prior to planting with a glyphosate herbicide. 

Before the sod is sprayed, the field 

should be grazed, mowed or hayed 

and regrowth allowed to reach 6 to 

10 inches. This ensures the herbicide comes into contact with an 

actively growing plant.

Cimarron®, formerly named 

Ally® from DupontTM, is labeled 

for post-emergence application on 

switchgrass for control of broadleaf 

weeds. Efforts are currently being 

made to gain regulatory approval for 

the use of an additional herbicide 

for grass suppression in Tennessee.

Observations in Tennessee 

on weed control in switchgrass 

indicate grass competition is much 

more severe than broadleaf competition. Once switchgrass is wellestablished and properly managed, 

it is very competitive against weeds.

Month-old switchgrass in East Tennessee.

Conventional equipment can be used to harvest switchgrass. Large rectangular 

bales are easier to handle, store and transport.

Reseeding Switchgrass 

Switchgrass establishment will 

not always be successful in the first 

year. Weed pressure, seed quality, 

incorrect planting procedures, level 

of soil moisture within the first 

four to five weeks of planting and 

other factors can contribute to not 

achieving an acceptable stand of 

switchgrass. The expected probability of needing to reseed is assumed to be 20 percent. Guideline 

expenses for establishment include 

the reseeding costs. 

Harvesting

Switchgrass can be harvested 

as a one- or two-cut system. When 

cut twice, the first cutting would 

occur when switchgrass is in late 

boot to very early seedhead emergence, which is usually in late June 

or early July. The second cutting 

would be at the end of the season 

and can occur when the plant goes 

into dormancy (usually after the 

first killing frost).

In the one-cut system, the 

switchgrass is harvested once after 

UTBiofuelsInitiative 3
Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development.

University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating.

UT Extension provides equal opportunities in programs and employment.

SP701A-5M-5/08 (Rep) R12-4110-070-019-08 08-0120

For more information about the UT Biofuels Initiative, please visit

http://www.UTbioenergy.org

*

Developed by Biofuels Farmer Education Team: Gary E. Bates, Christopher D. Clark, Deloras A. Dalton, Delton C. Gerloff, 

John J. Goddard, Ken J. Goddard, Laura Howard, Patrick D. Keyser, Melvin A. Newman, David R. Perrin, Lawrence E. Steckel, 

Finis Stribling, Donald D. Tyler, Michael D. Wilcox and James B. Wills, Jr.

November 1 or the first killing 

frost, whichever comes first. Total 

biomass yield for the year is similar in the one- and two-cut system. 

The choice should be influenced 

by management timing, costs and 

needs of the buyer relative to cutting time. Single harvest of switchgrass after the aboveground growth 

is killed by frost will reduce nutrient removal and fertility needs.

Switchgrass should be cut 

at least 6 inches high. The taller 

stubble will help reduce punctured 

tires by allowing equipment tires to 

push over the stubble. Furthermore, 

switchgrass stand survival, vigor 

and yield consistency in later years 

is greatly impacted by the cutting 

time and height. Switchgrass can 

be harvested with conventional hay 

equipment. Many farmers have 

large round balers and prefer to use 

their existing equipment. Round 

bales are acceptable. However, large 

rectangular bales (3 x 4 x 8 feet and 

4 x 4 x 8 feet) are easier to handle, 

store and transport.

Yields

In test plots, switchgrass has 

frequently produced more than 10 

tons of dry matter per acre/per year. 

However, on a commercial scale, it 

is more reasonable to expect 6 to 

8 tons per acre. In the first year of 

production, yields are estimated to 

run 30 percent (2 tons) of the full 

yield potential. Second year yield is 

normally 70 percent (5 tons) of full 

Factsheet adapted from publications developed by the University of Tennessee, Iowa State and Auburn University.

production. In the third year, yields 

should be at the 100 percent yield 

level of 7 tons. Over the first 5 years 

of an anticipated contract period, 

yields are estimated to average 5.5 

tons per year. Obviously, land quality, weather conditions, stand vigor, 

weeds and overall management 

will impact yield levels for a given 

switchgrass field.

Pest and Disease Management

Switchgrass has resistance to a 

wide variety of insects and diseases. 

Researchers and farmers have not 

experienced significant insect and 

disease problems in switchgrass 

trials conducted in Tennessee. As 

switchgrass acreage expands, it is 

not unreasonable to expect problems to develop over time.

Visit the UT Extension Web site at

http://www.utextension.utk.edu/

Funding that allowed the development of many of these recommendations was provided 

by the U.S. Department of Energy through project GO14219.

UTBiofuelsInitiative 4

Biofuels Initiative