Current Nitrogen Fertilization Strategy for Corn in

Transcription

Current Nitrogen Fertilization Strategy for Corn in
Current Nitrogen Fertilization
Strategies for Corn in
Nebraska
Richard Ferguson
Bob Caldwell
Nebraska Nitrogen Rate
Algorithm for Corn
NR = 35 + (1.2*EY) – (8*NO3-N) – (0.14*EY*OM)
EY = Expected yield (bu/acre)
NO3-N = Root zone soil residual nitrate-N (ppm)
OM = Soil organic matter (%)
Additional credits for legumes, irrigation water and manure.

Strengths


Fairly extensive
research database
Goal of minimizing
nitrate leaching below
root zone

Weaknesses


Reliant on accurate
preplant soil testing
Developed at yield
levels ≤ 200 bu/acre
Mid-Nebraska Demonstration Project
N Rate Response Over Years
Rec -
200
200
Rec
Rec +
180
180
160
160
140
140
120
120
100
100
80
80
60
60
1990 1991 1992 1993 1994 1995 1996 1997
Nitrogen (lbs/acre)
Yield (bu/acre)
Rec. N Rate
Expected
Yield
Mid-Nebraska Demonstration Project


N recommendation algorithm underrecommended N approximately 14% of the time
(24 of 170 sites from 1990 – 1997, at which
REC+ yield was statistically greater than REC
yield).
N recommendation algorithm overrecommended N approximately 52% of the time
(88 of 170 sites where REC- yield was
statistically the same as REC yield).
Nebraska Fertilizer Nitrogen Use Efficiency for Corn
Fertilizer Nitrogen Use Efficiency
lb N/bu
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
1965
1970
1975
1980
1985
Statewide average corn yield for grain, and surveyed average N rate – irrigated and dryland
Nebraska Agricultural Statistics Service
1990
1995
2000
Nitrogen Fertilizer Use in Nebraska
Primary Sources
900000
800000
Am Sulfate
N Consumption (tons)
Urea
700000
600000
500000
Am Nitrate
N Solution
Ammonia
400000
300000
200000
100000
0
1956
1960
1964
1968
1972
1976
1980
Year
Nitrogen for all crops
Nebraska Agricultural Statistics Service
1984
1988
1992
1996
2000
Chemigation: in-season wholefield N application
Producer Approaches to N Timing for Corn
NH3
100
Fall NH3
%
50
100
Preplant NH3
%
UAN
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
50
100
Sidedress
%
50
100
Fertigation
%
50
Summary


Current N recommendations for corn in
Nebraska have led to measured increases
in N use efficiency and reductions in
groundwater nitrate concentrations.
Current approach –



Relies on accurate preplant soil sampling.
Is not sensitive to application timing – ie
increased efficiency with fertigation.
May not be valid for yield levels above 220
bu/acre.

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