Upload
jamil
View
29
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Sensor Based Variable Rate N Management in Mid-Atlantic Cropping Systems. Joshua M. McGrath, UMD Wade Thomason, VT Steve Phillips, IPNI. Background on the Mid-Atlantic. Corn : Apply N based on realistic yield goal 1 lb N/bu expected yield Split-apply N fertilizer on corn - PowerPoint PPT Presentation
Citation preview
DEPARTMENT OF ENVIRONMENTAL SCIENCE & TECHNOLOGY
Laboratory for Agriculture and Environmental Studies
Sensor Based Variable Rate N Management in Mid-
Atlantic Cropping Systems
Joshua M. McGrath, UMD
Wade Thomason, VT
Steve Phillips, IPNI
Background on the Mid-Atlantic
Nitrogen Management Basics(since early 1990s in MD)
Corn:• Apply N based on
realistic yield goal – 1 lb N/bu expected yield
• Split-apply N fertilizer on corn– apply 30 – 40 lbs/A at
planting– remaining N as sidedress
• When utilizing manure or following leguminous cover crops use the
Pre-Sidedress Nitrate Test
Wheat:• Apply a total 70 – 120 lbs
of N• 20 – 40 lbs at planting• Split top-dress 80 – 100
– Green-up– Feekes 5 - 6
What makes us special?
• >90% side-dress N in Corn on Delmarva
• Yields vary widely 120 – 220 bu/ac
• >90% no-till corn• 50 – 60% irrigated on the
lower shore• In Maryland farmers cannot exceed University recommendations
VIRGINIA APPROACHVIRGINIA APPROACH
Generated calibration models for wheat and corn grown in the Mid-Atlantic
Developed N fertilization algorithms for both crops
Validated these rate equations for performance
VIRGINIA APPROACHVIRGINIA APPROACH
Generated calibration models for wheat and corn grown in the Mid-Atlantic
0
1
2
3
4
5
6
7
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007
Predicted Yield Index
Yie
ld,
Mg
ha
-1
0
1
2
3
4
5
6
7
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007
VIRGINIA APPROACHVIRGINIA APPROACH
Generated calibration models for wheat and corn grown in the Mid-Atlantic
y = 6.7825e367.41x
R2 = 0.9752
y = 8.5528e244.11x
R2 = 0.95
0
20
40
60
80
100
120
140
160
180
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009
Yie
ld,
bu
/ac
YPI
Wheat N Rate Algorithm
Rate (kg/ha) vs. NDVI
0.0000
20.0000
40.0000
60.0000
80.0000
100.0000
120.0000
140.0000
0.00 0.20 0.40 0.60 0.80 1.00
N Rate, kg/ha
Constrained NRate, kg/ha
VIRGINIA APPROACH - WheatVIRGINIA APPROACH - WheatTARGET NDVI
LOW REFERENCE HIGH REFERENCE GS 25 N DAP MAX YIELD MAX N NUE N RATE
0.60 0.50 0.80 50 150 85 80 50 80lbs/N dap bushels max constraint% lb/ac
87.1361 N fertilizer required23.5681 N required for additional grain46.0133 Bushel/A expected yield increase due to fertilizer
coefficients Define these units SI units ?ka 0.74076kb 577.66kc 1000kd
NUE 50%CONVERSION 0.0149
0.220.230.240.250.260.270.28
Rate (LB/ac) vs. NDVI
0.0000
20.0000
40.0000
60.0000
80.0000
100.0000
120.0000
140.0000
0.00 0.20 0.40 0.60 0.80 1.00
N Rate
Constrained
VIRGINIA APPROACH - CornVIRGINIA APPROACH - CornNDVI Low_Ref Hi_Ref N_preplant DFP MAX YIELD MAX N N RATE
0.82 0.50 0.90 60 63 175 100 85lbs/N dap bushels max constraintgal/acre
kg/ha85.27
coefficients Define these units SI units ?ka 56.479kb 67.626kc 56kd
NUE 60%Pn 0.0125
0.220.230.240.250.260.270.28
Rate (gal/ac) vs. NDVI
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
0.00 0.20 0.40 0.60 0.80 1.00
N Rate
Constrained
What’s Needed
• Reference Strips– Difference between:
• High N reference (best possible with more than adequate N)
• Low N reference (0 N applied)
And• Area currently in sensor’s view.
In-season N management
1st topdress based on estimated tiller #
2nd topdress based on Tissue N concentration
30 to 40 lb N/ac preplant
Zadoks stage, in parenthesis
In-season N timing
Days From Planting
1st topdress based on estimated tiller #
2nd topdress based on NDVI and DFP
Validation in VA, MD, DE
• ~60 sites across Virginia since 2000
• 12 sites in DE and MD (2008, 2009)
• Irrigated and non-irrigated
• Conventional and no till• Various rotations,
hybrids, varieties, and soil types
• Wide range of pre-plant, starter, and in-season N rates (including VR)
• Collected spectral measurements and an assortment of plant physical and chemical characteristics at various growth stages
• Determine grain yield
Validation in VA, MD, and DE
• RCBD; 3-8 reps• Plot size: 60 by 250
to 500 ft• In-season N:
– 4-5 Fixed Rates– 1 Standard Rate– 1 Variable Rate
Spra Coupe 220 w/ 60 ft boom and
GreenSeeker RT200
Raven 440 flow rate controller
Recommended vs. Applied Rates
0
5
10
15
20
25
30
1 201 401 601 801 1001 1201 1401 1601
gal/a
cre
Prescribed
As Applied
• 55% are within 2 gallons of prescribed rate• 88% within 5 gallons
Wheat: Applied N GreenSeeker vs. Tissue
0102030405060708090
100
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
SS
TD
GS
ST
DG
S
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 AVG
N r
ate,
kg
ha-1
Average Wheat Performance
Farmer Practice
Farmer Practice
GS
GS
0102030405060708090
100
Grain Yield, bu/ac GS 30 N Rate Applied, lb/ac
NS
7% less N with GS
Corn Algorithm Performance
0
20
40
60
80
100
120
1 2 3 4 5 6 7 8 9 10 11
N R
ate,
lb
/ac
STD
GS
0
20
40
60
80
100
120
140
160
STD
GS
Average Corn Performance
Grain Yield, bu/ac Sidedress N, lb/ac
NS
21 % (21 lb/ac) less N with GS
Limitations and Challenges
• Corn: V-7 versus V-4• Wheat: Herbicide in
second spring top-dress?• Check strips• How to tell if the system
was “right” – Skepticism• When parameters are
entered the application graph often needs tweaking by faking parameters
Honest Answers Don’t Always Work!
Can’t just plug and chug (spray)
Farmer would apply 46 gal/acre
N_pre = 0This has been corrected in the software
Part of the Adaptive Management Toolbox
• Systems approach– Manage soil N
• Focused on in-season N management– PSNT– Active Crop sensors– LCM
• End of season assessment– CSNT– Yield monitoring
The Future in the Mid-Atlantic
• The Chesapeake Bay and cost of fertilizer have us poised for rapid adoption– A few major farmers and ag service companies– Environmental Groups
• Likely to be covered through various cost share mechanisms soon
• Need to continue to refine algorithm to address– Accuracy of input values– Expand side-dress window– Straightforward user interface
Thanks to our partners