Post on 01-Jan-2022
Soil Fertility Dynamics
T. Scott Murrell
Director, Northcentral U.S.
National Alliance of Independent Crop Consultants,
2013 Annual Meeting, Jacksonville, FL. 22-26 Jan. 2013.
IPNI Nutrient Evaluation Efforts
• Soil Test Summaries
• Nutrient Use GIS
Median Bray P-1 equivalent
soil test levels, 2010
Change in median Bray P equivalent soil
test levels from 2005 to 2010
Soil test P distribution in 2010 compared to
2005 for the Corn Belt (12 states plus Ontario)
0%
5%
10%
15%
20%
25%
30%
Bray P1 Equivalent, ppm
Corn Belt P 2005 2.0 million samples2010 3.0 million samples
(2010) 22 28 (2005)
Median
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1987 P2O5 Balance
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1992 P2O5 Balance
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1997 P2O5 Balance
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2002 P2O5 Balance
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2007 P2O5 Balance
Expected changes in soil test levels
based upon nutrient budgets
Ch
an
ge
in
so
il t
es
t le
ve
l
~ 0
+
-
Application > removal
Application < removal
Application ≈ removal
Annual change in median soil P level for 12 Corn Belt
states as related to state P balance, 2005-2009
*NuGIS is a GIS nutrient balance model (IPNI, 2010).
y = 0.0897x - 0.063
r² = 0.62
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
-25 -20 -15 -10 -5 0 5
An
nu
al c
han
ge i
n m
edia
n P
, p
pm
NuGIS balance*, lb P2O5/A/yr
WI
IL
MI
IA
MN
SD
KS
OH
IN
NE
KY
MO
11 lb P2O5 / ppm
Median soil test K levels in 2010
Change in median soil K level from 2005 to 2010
Soil test K frequency distribution in 2001,
2005 and 2010
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1987 K2O Balance
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1992 K2O Balance
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1997 K2O Balance
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2002 K2O Balance
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2007 K2O Balance
Soil Test Potassium:
Difficulties with Identifying Trends
• Changes that occur are not consistently predictable
• What could be contributing to this variability?
Long-term crop removal and soil test P trends
0
1
2
3
4
5
6
7
8
9
10
0
100
200
300
400
500
0 2 4 6 8 10 12
Soil
P d
ecre
ase (
ppm
)
P r
em
oval (lb P
2O
5/a
cre
)
Years of corn/soybean rotation
P Removal Soil P decrease
Villavicencio and Mallarino, 2011. Personal communication
43 lb P2O5 / ppm
Long-term crop removal and soil test K trends
Villavicencio and Mallarino, 2011. Personal communication
0
10
20
30
40
50
60
0
100
200
300
400
500
600
700
800
0 2 4 6 8 10 12 14 16
Soil
K d
ecre
ase (
ppm
)
K r
em
oval (lb K
2O
/acre
)
Years of corn/soybean rotation
K Removal Soil K Decrease
12 lb K2O / ppm
Contributors to soil test K variability:
Sampling variability
Short-range variability of soil test K:
Across and down
Nutrient stratification
Banding 2 yr. ago
Banding 4 yr. ago
Banding this year
Depth control:
Important in reduced tillage systems
440 580
330 440
160
330
440
37 in. 37 in.
0
10
Dep
th (
in.)
160 6
Robbins and Voss, 1991 (IA)
8 in.
160 – 580 ppm
4 in.
330 – 580 ppm
No-till field with 10-yr history
Tama silt loam
Core number: Impact on variability
Soil test P category upper limit (ppm)
Fre
qu
en
cy (
50
to
tal)
0 2
17 20
7 3
1 0
5
10
15
20
25
30
35
40
5 cores per sample
0 0
8
34
8
0 0 0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70
20 cores per sample
True average
Contributors to soil test K variability:
Sampling frequency
Sampling frequency: Affects ability to detect trends
Crop year
So
il t
es
t le
ve
l
1 2 3 4 5 6 7 8
Increasing or decreasing?
Sampled every 4 years Sampled every 2 years Sampled every 1 year
Concept of a monitoring strip
Area where intensive
measurements are taken each
season
• Soil tests
• Plant tissue tests
• Nutrient deficiency
symptoms
• Grain nutrient content
• Diseases
• Insects
• Management practices
• etc.
Visual symptoms of K deficiency are a
useful diagnostic tool
170
0.0
0.5
1.0
1.5
2.0
0 50 100 150 200
K v
isu
al d
efic
ien
cy s
ymp
tom
ind
ex
Soil test K (ppm)
Deficiency Symptom Index:
0 = None
1 = Moderate
2 = Severe
Wittry and Mallarino, Iowa State University
Example of K deficiency symptoms:
soybean
Contributors to soil test K variability:
Leaching of K from plant residue
Changes in corn stover K content after
physiological maturity
Oltmans and Mallarino. 2011. Personal communication.
0
20
40
60
80
100
120
140
160
-50 0 50 100 150 200 250
Corn
sto
ver
K c
onte
nt (lb
K2O
/acre
)
Days since physiological maturity
harvest
Changes in soybean tissue K content
after physiological maturity
Oltmans and Mallarino. 2011. Personal communication.
0
20
40
60
80
100
120
140
160
-50 0 50 100 150 200 250
Soybean tis
sue K
conte
nt (lb
K2O
/acre
)
Days since physiological maturity
harvest
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
Water, inches
Pe
rcen
t o
f in
itia
l K
rem
ain
ing
Non-irrigated
Irrigated by overland flow
(2 in. every 7-21 days)
Schomberg, H.H. and J.L. Steiner. 1999. Soil Sci. Soc. Am. J. 63:607-613
Amount of water affecting K leaching
from residue
Contributors to soil test K variability:
Soil moisture
Potassium fixation Dehydrated K ion
Hydrated K ion
Clay mineral layer
Interlayer
positions
Havlin et al., 1999
Planar positions
Edge positions
Wetting/drying cycles impact variability
Sample Treatment Fixed K Exchangeable K
--------- meq/100g ----------
Drummer (Dekalb)
Dry 72.8 29.6
Wet 66.6 38.6
Drummer (Urbana)
Dry 71.6 33.7
Wet 65.7 39.6
Cisne (Brownstone)
Dry 43.9 30.9
Wet 39.2 42.9
Stucki, 1996 (IL)
Seasonal variation in soil test K
0
5
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
120
130
140
150
160
170
J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A
Soil
mois
ture
(%
)
Soil
test
K (
ppm
)
Month of the year
Soil test K
Soil moisture
1994 1997 1996 1995
Ebelhar et al. 1997. Personal communication. Soil test values are ammonium acetate extractable.
How the scientific community is
responding to variability in soil test K
Two primary efforts have been underway to address K
variability:
• Conduct new crop response trials
• Re-examine the effect of drying soils prior to analysis
Scientific response to
soil test K variability:
Updated crop response trials
Changes in soil test K critical levels:
Categories used previously – Iowa, U.S.
Mallarino, A.P. 2003.
40
50
60
70
80
90
100
110
0 50 100 150 200 250 300 350
Co
rn g
rain
rel
ativ
e yi
eld
(%
)
Soil test K (ppm)
Very
low
Low
Optim
um
Hig
h
Very
hig
h
Changes in soil test K critical levels:
Categories used previously – Iowa, U.S.
Mallarino, A.P. 2003.
40
50
60
70
80
90
100
110
0 50 100 150 200 250 300 350
Co
rn g
rain
rel
ativ
e yi
eld
(%
)
Soil test K (ppm)
Many other soils
Canisteo, Colo, Ely, Nicollet, Tama, Webster
Very
low
Low
Optim
um
Hig
h
Very
hig
h
Changes in soil test K critical levels:
Categories currently used – Iowa, U.S.
Mallarino, A.P. 2003.
40
50
60
70
80
90
100
110
0 50 100 150 200 250 300 350
Co
rn g
rain
rel
ativ
e yi
eld
(%
)
Soil test K (ppm)
Many other soils
Canisteo, Colo, Ely, Nicollet, Tama, Webster
Very
low
Low
Optim
um
Hig
h
Very
hig
h
Scientific response to
soil test K variability:
Re-examining the effect of drying soils
prior to analysis
Monitoring soil test K over time:
Effects of drying the soil sample
Field moist Air-dried
Mallarino, A.P. Personal communication. Soil test values are ammonium acetate extractable.
K applications
discontinued
0
50
100
150
200
250
0 10 20 30 40
Soil
test
K (
ppm
)
Years of corn/soybean rotation
0 lb K2O/acre
108 lb K2O/acre
Effect of sample drying on soil test K
y = 161.23x-0.543 R² = 0.9527
y = 84.336x-0.278 R² = 0.88
0
20
40
60
80
100
120
0 5 10 15 20 25 30
Soil
test
K (
pp
m)
Soil moisture (%)
Harpster silty clay loam
Clarion loam
Luebs, R.E. et al. 1956. Soil Sci. Soc. Am. Proc 20:45-50. Note: curve fitting and statistics not performed by the authors.
Initial soil test K levels affect changes as
soils are dried
0
50
100
150
200
250
300
350
400
0 5 10 15 20 25 30
Soil
test
K (
pp
m)
Soil moisture (%)
Bedford: no K added
Bedford: K enriched
Dowdy, R.J. and T.B. Hutcheson, Jr. 1963. Soil Sci. Soc. Am. Proc. 27:31-34.
Keeping samples moist may improve the
relationship of soil test K to yield response
Barbagelata and Mallarino. 2005. Personal communication.
60
70
80
90
100
110
0 100 200 300 400 500
Co
rn r
elat
ive
yiel
d (
%)
Soil test K (ppm)
Clay loam
Loam
Silty clay loam
Dried
Keeping samples moist may improve the
relationship of soil test K to yield response
Barbagelata and Mallarino. 2005. Personal communication.
60
70
80
90
100
110
-50 50 150 250 350 450
Co
rn r
elat
ive
yiel
d (
%)
Soil test K (ppm)
Clay loam
Loam
Silty clay loam
Moist
Summary
• Soil test P levels are declining in the Midwest, and these declines can be explained by mass balance
• Soil test K levels are declining in many states in the Midwest, but declines are not explained by mass balance perhaps because of high variability
• Causes of soil test K variability:
– Sampling variability
– Sampling frequency
– Leaching of K from crop residues
– Soil moisture
– Drying of soil samples prior to analysis
• Scientific response:
– Update crop response data
– Investigate drying of soils prior to analysis