Can Cover Crops Improve the Efficiency of

Fall Applied Nitrogen within Conventional

Midwestern Cropping Systems?

Corey Lacey

M.S. Candidate In Agriculture Sciences

Dr. Shalamar Armstrong

Assistant Professor of Soil Science and Agronomy

Our watersheds are

interconnected, therefore my N

management practices impacts

my neighbor

Introduction

USGS reported that Agriculture contributes > 70%

of N deliver to the Gulf of Mexico annually

Corn and Soybean fields of the Midwest contribute

contributes ~50% of the N loading to the Gulf (USGS,

2007)

• 73% increase in size since 1987

• 87% increase in size since 2000

(NOAA, 2011)

Growth of the Hypoxic Zone in the Gulf

Implementation of BMPs and

Conservation to Decrease N losses

Lemke et al. 2011

• 7 years of BMP

implementation, no

significant difference in

NO3-N concentration in

surface water.

Surface Buffer strip

Flowing Tile

No Connection

No Impact

Sprague et al. 2011

estimated that the contribution of nitrate from the Illinois River to

the Gulf of Mexico had decreased by only 1% between the years

of 1998 and 2008.

Implementation of BMPs and

Conservation to Decrease N losses

Manipulation of N rate

• several researchers have investigated the use of lower N fertilization rates to reduce nitrate leaching and found a direct relationship between N rates and nitrate losses via tile drainage, when the annual precipitation was normal.

• Other, studies have demonstrated that dry and wet climatic cycles more strongly influence N transport via tiles that application rate

• N timing most effectively reduce Nitrate leaching from tile

drained fields.

Implementation of BMPs and

Conservation to Decrease N losses

Fall N with and

without N-inhibitor

30-43ppm NO3-N

Spring N with and

without N-inhibitor

23-29 ppm NO3-N

Control

15-23 ppm NO3-N

Smiciklas and Moore, 2008 – Bloomington Watershed

EPA Standard for Nitrates:10 ppm

Spring Application of N + Cover Crops

Kasper et al., 2008, Iowa

Problem

• In Central Illinois 48-52% of farmers fall apply N (Smiciklas and Moore, 2008, O’rourke, 2010)

• In Central Illinois only ~11% of farmers cover crop (Leopold Center, 2006)

Objectives

Therefore, our goals are to determine the efficacy of cover crops to improve the efficiency of fall applied N.

1. Investigate the effectiveness of three cover crop species to reduce nitrate leaching following fall applied N.

2. Determine impact of cover crop species on the release of stabilized fall N to the spring cash crop.

Fall N Storage Using Cover Crops

N

N

N

Fall applied N

taken up by the

cover crop

In the spring, the

cover crop

decomposes and

releases N back

to the soil

The following

corn crop takes

up the release N

Methodology • The experimental site was located at the Illinois State

University farm in Lexington, IL.

Lexington

Methodology-Objective1

(Planting) Treatments:

• Corn-Corn – no cover crop Control

• Corn-Crimson Clover-Corn

• Corn-Cereal Rye-Corn

• Corn-Tillage Radish-Corn

*All treatments receive 200 kg ha-1 of fall applied N into a growing stand of cover crops

T.

Cover crops were drilled planted on September 8th, 2011,after harvesting corn

silage at the recommended seeding rates.

• Fall N fertilizer application

was applied to standing

cover crops in November as

anhydrous ammonium (200

kg ha-1).

Methodology-N Fertilization Practices

Method-Plant Sampling

• Plant samples were collected before the Tillage Radish plants winter killed.

• A second plant sampling was conducted in, before the termination of Cereal Rye and Crimson Clover. Only aboveground plant material was sampled.

• Plant samples were dried and analyzed for total N to determine N uptake.

Terminated the cover crops in March

• Spring soil samples were collected in April from each plot at

4 depths: 0-5cm, 5-20cm, 20-50cm and 50-80cm.

• Soil samples were analyzed for Nitrate Nitrogen (NO3-N)

Methods-Spring Soil Sampling

Soil Profile Depth 0-80cm

After spring plowing corn was

planted on April 23, 2012 and

May 15, 2013

Harvested corn for silage on August 12th 2012.

Methods-Corn Silage

0

2

4

6

8

10

12

Jan

-11

Feb

-11

Mar

-11

Ap

r-1

1

May

-11

Jun

-11

Jul-

11

Au

g-1

1

Sep

-11

Oct

-11

No

v-1

1

De

c-1

1

Jan

-12

Feb

-12

Mar

-12

Ap

r-1

2

May

-12

Jun

-12

Jul-

12

Au

g-1

2

Sep

-12

Oct

-12

No

v-1

2

De

c-1

2

Jan

-13

Feb

-13

Mar

-13

Ap

r-1

3

May

-13

Jun

-13

Pre

cip

itat

ion

(In

che

s)

Year 1

21.3 inches

Year 2

31.9 inches

Results- Year1

(2011/2012

Objective 1: Investigate the effectiveness of three cover crop

species to reduce nitrate leaching following fall applied N.

A

A

B

0

50

100

150

200

250

300

Nit

roge

n U

pta

ke (

kg/h

a)

Cover Crop Nitrogen Uptake

Cereal Rye

Tillage Radish

Crimson Clover

Results-Year 2

2012/2013

C 3.82

B 131.94

A 249.92

0.00

50.00

100.00

150.00

200.00

250.00

300.00

N u

pta

ke (

kg N

/ h

a)

Cover Crop N Uptake 2012/2013

Clover

Radish

Rye

2 Average

0

50

100

150

200

250

N U

pta

ke (

kg/h

a)

Cover Crop N uptake 2 year Average

Clover

Tillage Radish

Cereal Rye

A

A

B

Results- Year 1- 2011/2012

AB

A

A

B

C

B

BC

B

0

10

20

30

40

50

60

70

80

90

0 50 100 150So

il D

ep

th (

cm)

Soil NO3-N (kg/ha)

Control Tillage Radish

Crimson Clover Cereal Rye

0

10

20

30

40

50

60

70

80

90

0 20 40 60 80

Soil

De

pth

(cm

) Soil NO3-N (kg/ha)

Control Cereal Rye Tillage Radish Crimson Clover

A

A

A

AB

AB

AB

BC

AB

B AB

C

B

Results- Year 2- 2012/2013

Cover Crop vs. Control

Results- Year 2 Average

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90

Soil

De

pth

(cm

)

Soil NO3-N (kg ha-1)

Control

Cover Crop

A B

Specific Year 2 Averaged

0

10

20

30

40

50

60

70

80

90

0 50 100

Soil

De

pth

(cm

) Soil NO3-N (kg/ha)

Control Cereal Rye Tillage Radish Crimson Clover

A AB ABC C

A AB B C

A B

Cover Crop Impact of Nitrate Distribution

(2 year Average)

Control Cover Crop

0-20 cm

20-50 cm

50-80 cm

18%

35%

47%

30%

29%

33%

% S

oil

Nitra

te a

t 0

-80 c

m d

epth

Cover Crop Impact of Nitrate Distribution

(2 year Average)

Control Tillage Radish Cereal Rye Crimson Clover

0-20 cm

20-50 cm

50-80cm

28%

32%

40%

45%

24%

31%

33%

41%

27% 34%

29%

34%

% S

oil

Nit

rate

at

0-8

0 c

m d

epth

Method-Objective 2

• Soil samples were collected immediately before cover

crop termination and in weekly increments until 1 week

after the planting date of corn.

• Soil samples were analyzed for NO3-N.

Determine impact of cover crop species on the

release of stabilized fall N to the spring cash

crop.

Results-Year 1

2011/2012

Results-Year 2

2012/2013

0

20

40

60

80

100

120

-5 5 15 25 35

Soil

NO

3-N

(kg

ha-1

)

Days After Cover Crop Termination

Control

Tillage Radish

Cereal Rye

Crimson Clover

Cover Crop Termination

Spring Tillage

Planting 5/7/13

Nitrogen Released at Planting

0

20

40

60

80

100

120

Control Tillage Radish C. Rye C. Clover

% o

f Fa

ll ap

plie

d N

as

Soil

Nit

rati

on

in

the

0-2

0cm

De

pth

Year 1

Year 2

Results- Year 1- 2011/2012

What did we learn? Objective 1

• Tillage Radish and Cereal Rye were the only cover crops species that were able to absorbed the full rate of fall applied N.

• Fall application of N into a standing cover crop significantly reduces nitrate leaching. Cereal Rye>Tillage Radish>Crimson Clover

• Cover crops had no impact on corn silage production in the 2011/2012 growing season.

Objective 2

• Tillage Radish releases more fall applied N at planting relative Cereal Rye and Crimson clover.

• Extreme climatic conditions effect rate by which cover crops release fall applied N in the spring.

• The inclusion of Cover Crops into conventional cropping systems has the potential to increase the efficiency of fall applied N.