figure 1. residue removal effects on corn yields as affected by n rate in 2009 and 2010 for poorly...
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South West, Iowawell draining soil
SIde-dressed UAN (lbs N ac-1)
0 50 100 150 200 250
Cor
n Y
ield
(bu
ac-1
)
0
50
100
150
200
250
SIde-dressed UAN (lbs N ac-1)
0 50 100 150 200 250
2010
North Central, Iowapoorly draining soil
Cor
n Y
ield
(bu
ac-1
)
0
50
100
150
200
250
300
0 % removal50 % removal100 % removal
2009 2009
2010
*
*
*
**
*
*
**
**
Figure 1. Residue removal effects on corn yields as affected by N rate in 2009 and 2010 for poorly and well-drained soils. Asterisk indicates significant difference between residue removal within each N rate at p=0.05.
North Central, Iowapoorly draining soil
Residue Removal (%)
0 50 100
Co
rn Y
ield
(b
u a
c-1)
0
20
40
60
80
100
120
140
160Chisel plowNo-till
South West, Iowawell draining soil
Residue Removal (%)
0 50 100
bab
a
c
b b
c
ba
d
b b
Figure 2. Residue removal effects on corn yields as affected by tillage in 2010 for poorly and well-drained soils. Different letters indicate significant difference between residue removal and tillage at p=0.05.
North Central, Iowapoorly draining soil
Corn Residue Removal (%)
0 50 100
Soi
l Org
anic
Car
bon
(%)
0
1
2
3
4
5
6Chisel plowNo-till
Baseline = 4.46
South West, Iowawell draining soil
Corn Residue Removal (%)
0 5 10
Baseline= 2.39
aa a
aa
aa a a a
a
a
Figure 3. Total soil carbon as affected by two years of residue removal for poorly and well-drained soils. Different letters indicate significant difference between residue removal at p=0.05.
Corn Residue Removal (%)
0 20 40 60 80 100
Corn Residue Removal (%)
0 20 40 60 80 100
Corn Residue Removal (%)
0 20 40 60 80 100
SW
Iow
a, w
ell d
rain
ing
soi
lN
et S
OC
Seq
uest
ratio
n (t
on C
ac-1
)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
0 lbs N ac-1
NC
Iow
a, p
oorly
dra
inin
g s
oil
Net
SO
C S
eque
stra
tion
(ton
C a
c-1)
-2.0
-1.5
-1.0
-0.5
0.0
0.5Chisel plowNo-till
150 lbs N ac-1 250 lbs N ac-1
y = -0.6228 - 0.0036x, R2 = 0.72, CPy = -0.5281 - 0.0038x, R2 = 0.97, NT
y = -0.3059 - 0.0090x, R2 = 0.90, CPy = -2049 - 0.0083x, R2 = 0.98, NT
y = -0.1649 - 0.0086x, R2 = 0.91, CP
y = 0.1377 - 0.0092x, R2 = 0.82, NT
y = -0.8993 - 0.0006x, R2 = 0.61, CP
y = -0.6428 - 0.0016x, R2 = 0.54, NTy = -0.5230 - 0.0036x, R2 = 0.54, CP
y = -0.2915 - 0.0080x, R2 = 0.90, NT
y = -0.1397 - 0.0089x, R2 = 0.85, CPy = 0.0584 - 0.0068x, R2 = 0.92, NT
Figure 4. Potential changes to net soil organic carbon from carbon input from above- and below-ground biomass minus losses from microbial respiration to a depth of 15 cm. Carbon budget was conducted in 2010 in a well-drained soil and poorly-drained soil under different tillage and N fertilization regimes.
North Central, Iowapoorly draining soil
Residue Removal (%)
0 50 100
Bu
lk D
en
sity
(g
cm
-3)
1.0
1.1
1.2
1.3
1.4
1.5
1.6Chisel plowNo-till
South West, Iowawell draining soil
Residue Removal (%)
0 50 100
bb
a
b b
a
a
bb b
a a
Baseline: 1.25Baseline: 1.28
Figure 5. Soil bulk density as affected by two years of residue removal and tillage systems for poorly and well-drained soils. Different letters indicate significant difference between residue removal and tillage at p=0.05.
North Central, Iowapoorly draining soil
Residue Removal (%)
0 50 100
Ag
gre
ga
te M
ea
n W
eig
ht D
iam
ete
r
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8Chisel plowNo-till
North Central, Iowapoorly draining soil
SIde-dressed UAN (kg N ha-1)
0 170 280
bbc
c
a
c c b
aa
Figure 6. Aggregate mean weight diameter as affected by two years of residue removal, tillage and nitrogen rate systems for a poorly-drained soil site. Different letters indicate significant difference between residue removal, tillage and nitrogen rate at p=0.05.
North Central, Iowapoorly draining soil
Residue Removal (%)
0 50 100
Ste
ad
y In
filtr
atio
n R
ate
(cm
min
-1)
0.0
0.1
0.2
0.3
Chisel plowNo-till
South West, Iowawell draining soil
Residue Removal (%)
0 50 100
aa a a a a
a
ab
c
a
aba
Figure 7. Steady water infiltration rates as affected by residue removal and tillage for poorly and well-drained soil sites. Different letters indicate significant difference between residue removal and tillage at p=0.05.
0% Removal
Side-dressed UAN (N lbs ac-1)
0 150 250
Net
Gai
n o
r L
oss
of
CO
2 (l
bs
CO
2-C
ac-1
)
-1
0
1
2
3
4
5Chisel PlowNo-till
50% Removal
Side-dressed UAN (N lbs ac-1)
0 150 250
100% Removal
Side-dressed UAN (N lbs ac-1)
0 150 250
aa
a
b
c c
abab abab
c
c
b
abb
bc
cc
Figure 8. Potential sink or source for Atmospheric CO2-C .1. Include above ground biomass, grain, and root biomass for ANPP2. (ANPP + BNPP) – Rh 3. Positive values indicate a sink for atmospheric CO2
2010
Day of Year
50 100 150 200 250 300
2009
Day of Year
50 100 150 200 250 300
So
il S
urf
ace
CO
2 E
fflu
x (l
bs
ac-1
day
-1)
0
100
200
300
Chisel Plow, 0 % removedChisel Plow, 50 % removedChisel Plow, 100 % removedNo-tillage, 0 % removedNo-tillage, 50 % removedNo-tillage, 100 % removed
Figure 9. Seasonal CO2 emissions under different residue removal and tillage management in 2009 and 2010 for the poorly drained soil site in Ames.
2009
Day of Year
100 150 200 250
So
il S
urf
ace
N2O
Eff
lux
(g N
ha-1
day
-1)
0
50
100
150
200
250Chisel PlowNo-tillage
2010
Day of Year
100 150 200 250
So
il Mo
isture (cm
3 cm-3 vo
l %)
0
5
10
15
20
25
30
35
40
45
50
Chisel Plow moistureNo-till moisture
*
***
*
*
*
*
Figure 10. Seasonal N2O emissions under different tillage management in 2009 and 2010 for the poorly drained soil site in Ames.
2009 2010
Ave
rag
e S
oil
Su
rfa
ce
N2O
Eff
lux
(g N
ha-1
da
y-1)
0
10
20
30
40
50
600 % Residue Removed50 % Residue Removed100 % Residue Removed
a
bb
a
a
a
Figure 11. Mean annual N2O emissions under different corn residue removal management in 2009 and 2010 for the poorly drained soil site in Ames.
Table 1. Effect of N fertilizer Rate on Corn Biomass N and C Content at Plant Maturity Across Sites, 2009-2010 (John Sawyer and Jose Pantoja).
N Rate Veg. Cob Grain Total Veg. Cob Grain Total
lb N/acre - - - - - - - - - -lb N/acre - - - - - - - - - - - - - - - - - - - - - -lb C/acre - - - - - - - - - - - - - -
0 28 (43%) 3 (4.6%) 34 (52%) 651,770 (50%) 230 (5.5%) 1,555 (44%) 3,550
150 59 (38%) 6 (4.0%) 89 (58%) 1543,140 (43%) 510 (7%) 3,670 (50%) 7,320
250 73 (40%) 7 (3.8%) 103 (56%) 183 3,375 (42%) 555 (7%) 4,080 (51%) 8,010
Only the main effect of N rate was statistically significant for N and C (p<0.001).
Veg., vegetative material.