Changes in Soil Thermal Properties Under Corn Stover Removal

and Cover CropsMichael Sindelar1, Humberto Blanco1, Virginia Jin2, and Richard Ferguson1

1Department of Agronomy & Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA2 Agroecosystem Management Res. Unit, USDA-ARS, Lincoln, NE, USA

BACKGROUND

Removing corn stover and using cover crops (CCs) can alter soil

thermal properties (Blanco-Canqui et al., 2011; Kenney et al.,

2015)

Changes in soil thermal properties affect energy fluxes, climatic

fluctuations, seed germination, and others.

There is little information on how CCs can mitigate changes in

soil thermal properties after corn stover removal.

Knowledge of changes in soil thermal properties can be

important for developing sustainable management practices.

We used an ongoing experiment at the University of Nebraska-

Lincoln’s South Central Agriculture Laboratory located east of

Hastings, NE

The experiment was established in spring 2010 on a silty loam

(fine, smectitic, mesic Udic Argiustolls) with < 1% slope.

Treatments were: 1) control (no stover removal without CCs), 2)

no stover removal with CCs, 3) corn stover removal without

CCs, and 4) stover removal with CCs (Fig. 1).

Stover was mechanically removed each fall prior to CC planting.

The average rate of removal across 6 yr was 56±3%.

Winter cereal rye CC was planted after corn harvest and

terminated 3 wks prior to planting of corn in spring.

Two soil cores (5 cm x 5 cm) were sampled from each treatment

plot in May 2016 for the determination of thermal properties in

the laboratory.

The thermal properties were measured using a KD2 Pro with

SH-1 sensor on soil cores equilibrated at -0.033 MPa (field

capacity) and -1.5 MPa (permanent wilting point) matric

potentials.

In the field, thermal properties were measured every 15 d for

the first two months after corn plating and then every 30 d.

RESULTS

REFERENCES

Fig. 2. Soil thermal properties measured in the field.

Stover removal had an effect on thermal conductivity (p<0.05) and

specific heat capacity (p<0.05) in both field and laboratory.

Cover crop affected specific heat capacity in the laboratory (p<0.05) but

not in the field.

Interaction between CCs and corn stover removal was not significant for

any soil thermal property (p>0.10).

In the field, corn stover removal reduced thermal conductivity by 11-18%

and soil specific heat capacity by 12-18% compared to no removal

through the growing season (p<0.05; Fig. 2).

In the laboratory, corn stover removal reduced thermal

conductivity by 21% at field capacity and by 22% at permanent

wilting point (Fig. 3a).

Similarly, in the laboratory, corn stover removal reduced soil

specific heat by 18% at field capacity and by 20% at permanent

wilting point (Fig 3b).

Cover crop reduced specific heat capacity by 17% in the

laboratory at permanent wiling point (Fig 3b)

Soil thermal properties were not correlated to any soil property except

thermal conductivity, which was correlated with volumetric water

content at the 0.1 probability level (Fig 4).

Results show that corn stover removal reduces thermal

conductivity and specific heat capacity.

Results also show that cover crops can reduce the specific heat

capacity of soil at low water contents, but this warrants further

analysis to fully understand the extent to which cover crops

affect soil thermal properties in the long term (> 6 yr).

Changes in soil water content can be the most sensitive

indicators of changes in thermal conductivity.

Thermal conductivity appears to be more responsive to stover

removal compared with specific heat capacity.

Other soil properties (i.e., pore-size distribution) may influence

changes in thermal properties more than soil organic C and bulk

density in this study.

CONCLUSIONS

This study suggests that stover removal can reduce the

amount of heat flow and exchange through the surface

layers and can have implications for crop establishment

and climatic fluctuations.

Removing approximately 50% of corn stover can impact

soil thermal properties.

Cover crops may not mitigate the negative impacts of corn

stover removal on soil thermal properties.

Further long-term monitoring is needed, particularly under

cover crops, as the magnitude of change in soil properties

could increase with time (> 6 yr).

Blanco-Canqui, H., Mikha, M. M., Presley, D. R., & Claassen, M. M.

(2011). Addition of cover crops enhances no-till potential for

improving soil physical properties. Soil Science Society of America

Journal, 75(4), 1471-1482..

Kenney, I., Blanco‐Canqui, H., Presley, D. R., Rice, C. W., Janssen,

K., & Olson, B. (2015). Soil and crop response to stover removal

from rainfed and irrigated corn. GCB Bioenergy, 7(2), 219-230.

METHODOLOGY

DISCUSSION

OBJECTIVE

To assess the impact of corn stover removal and CCs on soil thermal

properties (thermal conductivity, specific heat capacity, and thermal

diffusivity) through the growing season on a 6-yr irrigated no-till

continuous corn in south central Nebraska. We also correlated soil

thermal properties with other soil properties.

Fig. 1. Experimental treatments.

A B

C

y = 0.88x + 0.89r² = 0.20; p=0.10

0.8

1.0

1.2

1.4

1.6

1.8

0.1 0.2 0.3 0.4 0.5 0.6

The

rmal

Co

nd

uct

ivit

y

(W m

-1k-1

)

Volumetric Water Content (cm3 cm-3)

A

aB

b

1.5

2.0

2.5

3.0

3.5

-0.033 MPa -1.5 MPa

Spe

cifi

c H

eat

Cap

acit

y (M

J m

-3K

-1)

Matric Potential

Fig. 3. Thermal properties measured in the laboratory at -0.033 and -1.5 MPa.

A

b

A

a

1.5

2.0

2.5

3.0

3.5

-0.033 MPa -1.5 MPa

Spe

cifi

c H

eat

Cap

acit

y (M

J m

-3K

-1)

Matric Potential (MPa)

Cover CropNo Cover Crop

Fig. 4. Relationship of thermal conductivity with soil water content.

Corn stover removal without CCs

No stover removal without CCs

Corn stover removal with CCs

No stover removal with CCs

a

a

a

a

a

a

bb

b

b

b

b

2.0

2.2

2.4

2.6

2.8

3.0

3.2

10-May 30-May 19-Jun 9-Jul 29-Jul 18-Aug 7-Sep

Spe

cifi

c H

eat

Cap

acit

y

(M

J m

-3K

-1)

SAMPLING DATE

Control Stover Removal

A

a

B

b

0.6

0.8

1.0

1.2

1.4

-0.033 MPa -1.5 MPa

The

rmal

Co

nd

uct

ivit

y(W

m-1

k-1

)

Matric Potential

Control

Stover Removal

aa

a a

aa

bb

b b

b

b

0.7

0.8

0.9

1.0

1.1

1.2

1.3

10-May 30-May 19-Jun 9-Jul 29-Jul 18-Aug 7-Sep

The

rmal

Co

nd

uct

ivit

y (W

m-1

k-1)

Control Stover Removal