69th SWCS International Annual Conference “Making Waves in Conservation: Our Life on Land and Its Impact on Water” July 27-30, 2014 Lombard, IL

1. 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

2. Upper Landscape
Lower Landscape

3. 2008 Upper Landscape
2011 Lower Landscape2011 Upper Landscape
2008 Lower Landscape

4. June 20, 2011 July 7, 2011
May 24, 2011April 13, 2011 May 24, 2011

5. 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

6. 0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
1 2 3 4 5
KgHa-1
Cluster
Nitrogen - 2008
55-65 cm
35-45 cm
25-35 cm
15-25 cm
0-15 cm
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
1 2 3 4 5
KgHa-1
Cluster
Nitrogen - 2011
55-65 cm
35-45 cm
25-35 cm
15-25 cm
0-15 cm
0
10,000
20,000
30,000
40,000
50,000
60,000
1 2 3 4 5
KgHa-1
Cluster
Carbon - 2008
55-65 cm
35-45 cm
25-35 cm
15-25 cm
0-15 cm
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1 2 3 4 5
KgHa-1
Cluster
Carbon - 2011
55-65 cm
35-45 cm
25-35 cm
15-25 cm
0-15 cm
Soil Carbon
Nitrogen
Linkage

7. 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%

8. 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
Average
2,500 (190) A 3,350 (90) 750 (40) 4,730 (220) B
County
Average‡
7,276 3,282 NA§ 8,060

9. 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+2011
Yield = 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

10. 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

11. 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.