Switchgrass as a Biofuels Crop for the Upper Southeast: Variety Trials
and Cultural Improvements

##### Lee Daniels

John Fike

Rocky Lemus

David Parrish

Paul Peterson

######## Zheng-Xing Shen

####### Dale Wolf

Crop and Soil Environmental Sciences

###### Virginia Tech

John Balasko -- WVU

James Green -- NCSU

Monroe Rasnake -- UK

John Reynolds -- UT/K

**Results/conclusions from "main study"**

**(6 varieties, 2 cutting mgmts, 8 sites, 4 years)**

Switchgrass yields well in upper Southeast:

-   \~15 Mg/ha/yr yield average

-   Top site/variety/mgmt/yr  26 Mg/ha/yr

-   Poorest combo  8 Mg/ha/yr

> Wide variation among sites: 11 to 18 Mg/ha/yr

# Little variation among five cultivars/lines when cut twice (\'Shelter\' consistently lower)

## For the two upland ecotypes, two cuts  25 to 

## 30% more yield than one cut

> 1 cut~upland~ \< 2 cuts~upland~ ≈ 1 cut~lowland~ ≈ 2 cuts~lowland~
>
> **Conclusions from main study (continued)**
>
> N boosts two-cut yields

-   \~30% increase for 0 vs. 100 kg N/ha

### NPK levels in first harvest \>\> than in second

-   June: N/P/K/Ca = 1.04/0.20/1.26/0.27%

-   Nov.: N/P/K/Ca = 0.63/0.11/0.67/0.39%

### 

### NPK removal substantial; reduced if cut once 

-   2X (15.4): N/P/K/Ca = 154/28/172/74 kg/ha

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-   1X (15.0): N/P/K/Ca = 56/11/68/45 kg/ha

N accumulates below ground at end of season

-   1 Oct.: crown/roots/biomass = 0.83/0.62/0.78%

-   1 Nov.: crown/roots/biomass = 1.20/0.75/0.40%

**Conclusions from main study (continued)**

More N accumulates with 1 cut than with 2

-   Once: crown/roots/biomass = 1.81/1.22/0.42%

-   Twice: crown/roots/biomass = 1.20/0.75/0.40%

Root biomass is very substantial

-   50 to 75% of roots found in upper 20 cm

-   Total root biomass from 5 to 14 Mg/ha

-   Root/soil separation misses 40+%

-   No consistent effect of cutting mgmt

### 

### Stands remain "pure" and show persistence

-   No weed encroachment

-   However, thinner stands observed with:

    -   Single cut

    -   Higher N levels

##### Results/Conclusions from Other Studies

Minimal correlation between yield and soil tests for P or K

-   None in main study (eight sites)

-   Response seen at one other site where P and K were \"low\"

-   No response to P and K fertilization in three studies where N was an
    added factor (and N did boost yields)

Seeds of all varieties we've studied are dormant at harvest

-   Dormancy can be broken during warm storage (one year)

-   Dormancy can also be broken by stratification

Seed yields were boosted by Banner and 3-D (seaweed extract) 30 to 60%
in 1997 to 2000

##### Other observations/predictions

#### Odds for successful switchgrass establishment 

#### will be improved by:

-   Using no-till methods

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-   Breaking seed dormancy before planting

-   Planting into a fully warmed soil

-   Killing live weeds

-   Reducing insect herbivory

Switchgrass stands will persist indefinitely with ≤ two harvests.

Leaves will likely represent a better test tissue than whole plants for
determining fertilization needs, and soil tests will be of no/minimal
use.

50 kg N/ha will maximize yields for one-cut management (under our
conditions).

"Accelerated after-ripening" will work well for breaking switchgrass
seed dormancy.

##### Some suspicions/interesting observations

Over-fertilization with N may be detrimental.

Single-cut management may reduce stand thickness (tiller #) but not
stand life.

Switchgrass can thrive under low P and K and pH; perhaps due to
mycorrhizae?

More N can to be removed in biomass than is being added in fertilizer.

-   Symbiotic N fixation?

-   Mineralization?

##### Cooperative efforts

######### New lines from OSU program tested

######### Some are very promising.

Soil C and N studies done with ORNL

+------+---------+----+-----------+------+---------------------------+
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+------+---------+----+-----------+------+---------------------------+
| 1    | SL93-3  | 16 | 18.7      | 18.8 | 17.9                      |
|      |         | .3 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 2    | SL93-1  | 14 | 14.7      | 21.3 | 16.7                      |
|      |         | .0 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 3    | SL94-1  | 12 | 16.5      | 20.0 | 16.5                      |
|      |         | .9 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 4    | SL92-1  | 12 | 16.0      | 18.0 | 15.6                      |
|      |         | .8 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 5    | SL93-2  | 10 | 16.8      | 18.2 | 15.1                      |
|      |         | .4 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 6    | NL92-1  | 11 | 15.4      | 16.4 | 14.3                      |
|      |         | .2 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 7    | Alamo   | 12 | 15.6      | 14.2 | 14.0                      |
|      |         | .2 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 8    | Kanlow  | 9  | 16.4      | 16.1 | 13.9                      |
|      |         | .1 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 9    | NL93-1  | 9  | 15.8      | 15.0 | 13.4                      |
|      |         | .4 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 10   | NL94-1  | 11 | 16.1      | 12.3 | 13.3                      |
|      |         | .4 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 11   | NL93-2  | 9  | 14.8      | 13.0 | 12.3                      |
|      |         | .0 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| 12   | C-in-R  | 6  | 11.0      | 7.9  | 8.5                       |
|      |         | .7 |           |      |                           |
+------+---------+----+-----------+------+---------------------------+
| LSD  |         | 2  | 3.0       | 3.7  | 3.0                       |
| ~0   |         | .2 |           |      |                           |
| .05~ |         |    |           |      |                           |
+------+---------+----+-----------+------+---------------------------+