Transcript Moving Beyond Nitrogen with Field Sensors

Moving Beyond Nitrogen with
Field Sensors
Jim Schepers (emeriti)
Agronomy and Horticulture Dept.
University of Nebraska
Premise –
in-season differences in crop vigor will be
proportional to yield at harvest
≈
Nocorrelation
correlationbetween
betweenlooks
looks(ears)
andand
yieldyield
“ “
““No
HenryA.A.Wallace
Wallace
Henry
1.2
Relative Yield
1.0
0.8
0.6
0.4
V9
y = 1.777x - 0.5492
R² = 0.8417
0.2
V12
y = 1.6218x - 0.422
R² = 0.9137
0.0
0.4
0.5
0.6
0.7
0.8
Sufficiency Index
Irrigated Corn - 2009
0.9
1.0
2.5
SI early
RI early
SI late
RI late
Relative NDVI
2.0
1.5
1.0
0.5
~ V6
~ V12
0.0
0.2
0.4
0.6
NDVI
0.8
1
Back in 2003, 2004 and - - - - “Relative yield has no value” - Bill Raun
Relative Yield =
RI yield =
Point Yield
----------------------------------------------------------------
Reference Yield
Reference Yield
----------------------------------------------------------------
Point Yield
Why is Sensor Adoption Slow ?
• Lack of perceived spatial variability
• Time window is too short
• Don’t have a high-clearance sprayer
• Anhydrous ammonia is cheaper
• Too costly for small producers
• Other adaptive management options (fertigation)
• Intimidated by the technologies
• Not compatible with strip-tillage
Why is Sensor Adoption Slow ?
• Reports of reduced yields with sensors
• Marketed from an equipment perspective
• John Deere system is not compatible with AgLeader
• Flow-rate change is slow
• Don’t like N-rich strip requirement
• Don’t believe yield potential prediction is reliable
• Algorithm structure and options not explained
• Lack of technical assistance / publications
My Impressions - - - • N fertilizer is still an excellent investment
• Adaptive management aspect of sensors is not
perceived as environmental attribute
• Producers don’t understand NUE implications
• Crop canopy sensors are simply a TOOL
• Effective promotion resides with seed companies,
service agencies, and curious producers
Nitrogen Use Efficiency - NUE
16
NUE = 45%
Corn Yield (ton/ha)
14
12
10
8
6
4
“ Free Nitrogen “
2
0
0
50
100
150
N Rate (kg/ha)
200
250
NUE = 45%
16
14
Corn Yield (ton/ha)
NUE = 11%
NUE = 34%
NUE = 56%
12
NUE = 78%
10
8
6
4
“ Free Nitrogen “
2
0
0
50
100
150
N Rate (kg/ha)
200
250
Corn Yield (ton/ha)
16
Mathematical Maximum
14
12
10
Net return of $6.13 for each
$1.00 spent on fertilizer
8
6
Assume:
4
$1.20 / kg N
$240 / ton corn grain
2
0
0
50
100
150
N Rate (kg/ha)
200
250
ECONOMICS
- Return per $1.00 invested in N fertilizer
Corn Yield (ton/ha)
16
$-0.83
$4.39
14
$7.90
12
$11.51
10
8
Assume:
6
$1.20 / kg N
$240 / ton corn grain
4
2
0
0
50
100
150
N Rate (kg/ha)
200
250
Effect of over or under-application by 10% ?
Corn Yield (ton/ha)
16
Mathematical Maximum
14
12
10
$-41.51/ha
$7.33/ha
8
6
201
4
y = -0.000178x2 + 0.071468x + 6.544653
R² = 0.991975
2
0
0
50
100
150
N Rate (kg/ha)
200
250
Effect of over or under-application by 10% at EONR ?
Corn Yield (ton/ha)
16
Economic Optimum N Rate
14
12
10
$-15.90/ha
$-14.95/ha
8
6
187
EONR - where the cost of the
4
last unit of N equals the increase
in grain value.
2
0
0
50
100
150
N Rate (kg/ha)
200
250
Observation
- After producers get past the
intimidation of new software, they want to know more
about how the algorithms work and how they can
manipulate the inputs to accomplish their management
objectives.
RapidSCAN Data - July 2, 2013
-97.859
41.3658 41.3659 41.3660 41.3661 41.3662 41.3663 41.3664 41.3665
-97.860
Longitude
-97.861
-97.862
-97.863
-97.864
-97.865
-97.866
Latitude
RapidSCAN - User Inputs
Reference Index (NDRE or NDVI)
Minimum N rate
Maximum N rate
N credits
Back-off (none, slow, medium, fast)
RapidSCAN Data - July 2, 2013
60
N Rate (lb/acre)
50
Series1
40
Series2
Series3
30
Series4
Series5
20
Series6
10
0
0
50
100
150
200
Sample Number
250
300
Data Output
NRA
NDR
PLOT TE VREF E
SI
NDVIRE
NIR R
Plot
N-rate
Virtual Reference
NDRE
SI
NDVI
Red-edge reflectance
NIR reflectance
Red reflectance
Latitude
Longitude
Elevation
HDOP
Fixture type
ELEV
LATITU LONGI ATIO HDO FIXT DAT
DE
TUDE N
P
YPE E
TIMEN
38
23.8
0.3520
0.3256
0.9250
0.7599
19.434
38.261
5.210
41.365873
97.864848
495.7
0.75
GP
MAX
MIN
STD
NDR MAX NDR MIN NDR STD CVN CVN
E
NDVI E
NDVI E
NDVI DRE DVI
Date
Time
Number of readings*
Maximum NDRE
Maximum NDVI
Minimum NDRE
Minimum NDVI
Stdev NDRE
Stdev NDVI
CV NDRE
CV NDVI
3/7/2013
14:13:15
17
0.3785
0.8259
0.2618
0.5907
0.0278
0.0486
0.0853
0.0639
* Readings recorded at 2 Hz
Jim Schepers
402-310-6150
[email protected]