Effect of Conservation Practices on Soil Carbon and Nitrogen Accretion and Crop Yield in a Corn

Production System in the Southeastern Coastal Plain, USA

Tim Strickland, Brian Scully, Dana Sullivan, Zaid Abdo, Gary Hawkins, Reza Savabi, Bob Hubbard, and Dewey Lee

Upper Landscape

Lower Landscape

2008 Upper Landscape

2011 Lower Landscape2011 Upper Landscape

2008 Lower Landscape

June 20, 2011 July 7, 2011

May 24, 2011April 13, 2011 May 24, 2011

Conservation Farming Effect on Soil Carbon

Storage

Carbon Increase (kg ha-1)

Cluster 0-65 cm 0-15 cm % of Total 15-35cm % of Total

1 17,000 a 6,500 a 38 7,200 a 41

2 21,000 ab 6,800 a 33 8,500 ab 41

3 16,000 a 5,800 a 36 7,000 a 43

4 22,700 ab 7,400 a 33 8,900 ab 39

5 29,000 b 9,800 a 34 13,400 b 45

Whole Farm Carbon Increase (kg ha-1)

0-65 cm 0-15 cm 15-35cm

Average 19,900 6,900 8,400

Min 6,400 -1,800 2,900

Max 62,100 19,100 26,500

Whole Farm Regression - 2008 v 2011 Profile Carbon

0-65 cm 0-15 cm 15-35cm

Slope 10,300 790 2,030

P < 0.001 < 0.001 < 0.001

0500

1,0001,5002,0002,5003,0003,5004,0004,500

1 2 3 4 5

Kg

Ha-1

Cluster

Nitrogen - 2008

55-65 cm35-45 cm25-35 cm15-25 cm0-15 cm

0500

1,0001,5002,0002,5003,0003,5004,0004,500

1 2 3 4 5

Kg

Ha-1

Cluster

Nitrogen - 2011

55-65 cm35-45 cm25-35 cm15-25 cm0-15 cm

0

10,000

20,000

30,000

40,000

50,000

60,000

1 2 3 4 5

Kg

Ha-1

Cluster

Carbon - 2008

55-65 cm35-45 cm25-35 cm15-25 cm0-15 cm

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

1 2 3 4 5

Kg

Ha-1

Cluster

Carbon - 2011

55-65 cm35-45 cm25-35 cm15-25 cm0-15 cm

Soil Carbon Nitrogen Linkage

Carbon & Nitrogen from Above-Ground

Residue

Winter Cover SE Crop Residue SE Fertilizer

Carbon (kg ha-1)

2007 ND‡ Millet ND 1008

2008 2,373 a* 186 Corn 599 a 46 1008

2009 2,900 b* 194 Peanut 2,514 b 99 0

2010 1,987 a* 179 Millet 5,539 c 302 0

2011 6,724 c* 463 Corn 804 d 36 0

Total 13,984 * 211 9,456 184 2016

Nitrogen (kg ha-1)

2007 ND Millet ND 92

2008 66 a* 8 Corn 12 a 1 92

2009 75 a* 5 Peanut 104 b 4 0

2010 69 a* 7 Millet 145 c 10 106

2011 106 b* 7 Corn 17 d 1 123

Total 316 4 277 5 413

Input (kg ha-1) Accreted (kg ha-1,

0-65 cm)

Retention

Efficiency

Total C (SE) 31,000 (670) 19,900 (1,400) 64%

Total N (SE) 1,150 (30) 2,100 (90) 183%

Impact on Yield

Percentage of corn nitrogen requirement provided by soil (0-35cm) chloroform

extractable-N

2008 2011

Cluster Required N SE Required N SE

1 50 a* 15 160 a 19

2 20 b* 3 150 a 34

3 15 b* 2 150 a 31

4 12 ab 2 120 a 50

5 8 c* 0 100 a 21

kg ha‐1 (SE)

Cluster Corn‐2008 Peanut‐2009 Millet‐2010 Corn‐2011

1 1,230 (200) aA 3,050 (210) a 790 (40) a 3,700 (180) aB

2 2,180 (180) abA 3,470 (150) a 790 (100) a 4,060 (190) abB

3 3,250 (200) bcA 3,460 (180) a 660 (80) a 4,410 (260) abA

4 3,890 (120) cdA 3,590 (160) a 770 (80) a 5,440 (260) bA

5 5,250 (170) dA 3,150 (250) a 760 (190) a 6,890 (400) cB

Yield 

Average2,500 (190) A 3,350 (90) 750 (40) 4,730 (220) B

County 

Average‡7,276 3,282 NA§ 8,060

Year Yield Model R2 P =

2008 Yield = x0419 + x0139 + x0439 + zone/x0218 0.989 0.02

2011 Yield = zone + x0218 + x0317 + x0439 0.989 0.02

2008+2011Yield = x0639 + x0318 + x0619 +

yr*zone/x0218 0.990 0.02

139 0-15 cm Silt%

218 15-25 cm Carbon (kg/ha)‘08 = 0.974‘11 = 0.986

317 25-35 cm Nitrogen (kg/ha)

318 25-35 cm Carbon (kg/ha)

419 35-45 cm C:N ratio

439 35-45 cm Silt%

639 55-65 cm Silt%

619 55-65 cm C:N Ratio

Stage

Water Demand (cm/day)

Stage Duration

(days)

Cluster

1 2 3 4 5

Emergence 0.203 10 2 1 1 0 2

4-leaf 0.158 19 2 2 1 0 2

8-leaf 0.160 17 2 1 1 0 2

12-leaf 0.083 9 4 3 3 0 4

Early Tassel 0.142 13 2 2 1 0 3

Silking 0.119 13 3 2 2 0 3

Blister 0.055 7 6 4 4 1 7

Begin Dent 0.093 16 3 3 2 0 4

Full Dent 0.077 21 4 3 3 0 5

Maturity 0.025 15 12 9 8 1 15

Estimated† increase in water stored in the top 35cm of soil from 2008 to 2011 available to meet crop water demand during critical corn growth stages

† Williams, J.R., C.A. Jones and P.T. Dyke. 1984. A modeling approach to determining the relationship between erosion and soil productivity. Trans. ASAE 27(1):129-142

Summary

• Conservation Farming increased soil C 19.9 Mg Ha-1 (8.9 Tons Ac-1) and N 2.1 Mg Ha-1 (0.9 Tons Ac-1).

• Conservation Farming increased corn yield 2230 Kg Ha-1 (1990 lbs Ac-1).

• Corn yield increases were most correlated with soil carbon content at Regression indicated that soil carbon content at a depth of 15-25 cm, and the amount of influence varied by slope position.

• Although soil carbon and nitrogen changes were highly correlated (R2 = 0.844), plant available nitrogen was greater than estimated requirement (@ 52.6 kg corn kg-1 N) and was not predictive of yield increase.

• The correlation between yield increase in an extreme drought year and soil carbon is suggested to be mediated via increased soil water holding capacity.