Current N Fertilization
Strategy for Corn
in Missouri
Newell Kitchen
Cropping Systems and Water Quality Research Unit
Columbia, Missouri
USDA-ARS
Major Soil Regions in Missouri
Missouri Corn Nitrogen Requirement (NR):
University of Missouri:
NR (lbs/A) = POP x 4 + 0.9 x YG – MN
Where:
POP is the plant population in 1000s
YG is expected yield in bu/A
MN is the expected N mineralization from SOM
Nitrogen rate adjustment based upon
soil texture, organic matter, and time of major crop
Soil
texture
Cool-season
Cation exchange
Organic
crops (lbs.
capacity (me/100 g.) matter (%) N/A)
Warm-season
crops (lbs. N/A)
Sands —
sandy
loam
less than 10
0.5
1.0
1.5
10
20
30
20
40
60
Silt loams
— loam
10 to 18
2.0
3.0
4.0
20
30
40
40
60
80
Clay
loams —
clays
greater than 18
2.0
10
3.0
15
4.0
20
5.0
25
1Based on soil texture, organic matter and time of major growth.
20
30
40
50
Missouri Corn Nitrogen Requirement (NR):
MFA:
NR (lbs/A) = 1.5 x YG - MN - PCA
Where:
YG is expected yield in bu/A
MN is the expected N mineralization from SOM
PCA is the previous crop addition (ex. 20 for soybean)
A CEC adjustment within MN is an attempt to correct for N loss
associated with leaching in low CEC soils and denitrification in high
CEC soils. A CEC of 10 (silt loam) was set as the pivot point.
MFA’s Previous Crop N Credit for
common crops in the Lower Midwest
Previous Crop
Nitrogen Credit (lbs./acre)
Soybeans
10
Winter Wheat
-10
Corn
-10
Milo
-20
Cotton
-10
Rice
-20
Alfalfa (1/2 stand)
40
Given: A soil test CEC = 10, O.M. = 2.0,
previous crop = corn, plant population =
28,000.
What are the MFA and University of
Missouri N Recommendations for a
yield goal of 160 bu/A corn?
Exactly the same: 200 lbs N/A
Other Important N BMPs in Missouri
• For river bottom soils
and irrigated fields,
farmers are encouraged
to side-dress the
majority of N
-about 90% of “boot-heel”
farmers side-dress
Other Important N BMPs in Missouri
The preplant N test is advocated under certain
conditions:
• on fields that have received manure anytime since the
previous summer.
• on fields that have a history of heavy manure applications.
• following a drought year on fields with a high potential for
carry over for fertilizer N.
• following fall and early spring fertilizer applications where
excessive rainfall may have caused losses of fertilizer N.
Other Important N BMPs in Missouri
• Ammonium nitrate is the preferred source of
nitrogen in no-till when injection is not possible
and the material must be surface broadcast.
Nitrogen source
Corn yield1
Ammonium nitrate (34-0-0)
149
Urea (46-0-0)
142
UAN solution (32-0-0)
132
1Average
across 8 site years in Missouri