use of aerial imagery to detect n response in corn following alfalfa fr 5262 matt yost stephen palka
TRANSCRIPT
Use of aerial imagery to detect N response in corn following alfalfa
FR 5262Matt Yost
Stephen Palka
http://www.rothamsted.ac.uk
Alfalfa provides N to following crops
~100 lb N ac-1 yr-1
2% N
~200 lb N ac-1 yr-1
http://www1.umn.edu/news
Alfalfa provides Nitrogen to corn for 2 years
State1st-year N credit†
2nd-year N credit†
-------- lb N ac-1 --------IA 170 140IL 100 30IN 140 ---KS 120 ---MI 140 ---MN 150 75MO 100 ---ND 150 75NE 150 ---OH 140 ---SD 150 75WI 150 50
42 on-farm alfalfa-corn N rate trials (2009-2012)K
Regrowth, tillage time
No-till
Manure
Predictors
Stover removal, predictors
1st-year corn31 site-years
2nd-year corn11 site-years
More trials needed: Can yield differences be detected with NDVI?
0
20
40
60
80
100
Economicoptimum
N rate(lb N/acre)
1st year corn - ROHE
Fall applied manure
4 fertilizer N rates
Corn 2011
2nd year corn – MARPE
Aerial imagery: - 1m spatial resolution- 4 bands (RGB, NIR)- collected Aug. 2011
Create shapefiles of plots in ArcMap:GPS points (10-70 cm accuracy)Projected to NAD 83 UTM Zone 15N
Change image band order:Originally IR R G B, changed to B G R IR in ArcMap
Calculate vegetation Indices:Create AOI for plotsUse signature editor to average pixel values for plots.
Methods
ROHE MARPE
Aerial images
Shapefiles of plots with -1.5 ft buffer
NDVI - MARPE
NDVI - ROHE
Methods of NDVI calculation
NDVI related to corn grain yield
Other indices were not better – IR/RED
Other indices were not better - TNDVI
Highest correlation – Silage yield vs. IR/Red
Can NDVI be used to detect corn yield differences?
Main effect P values (P > F)Grain yield Silage yield NDVI
Manure 0.484 0.164 0.326
N 0.003 0.025 0.042
Manure*N 0.515 0.339 0.952
Regrowth 0.177 - 0.656
N 0.021 - 0.018Regrowth*N 0.234 - 0.835
YES!
Are the slopes of yield and NDVI related? - ROHE
Are the slopes of yield and NDVI related? - MARPE
Conclusions
• Farmers could use aerial imagery to determine whether N fertilizer treatments affected corn yield.
• This would make it easy for farmers to conduct their own research.
• More fields and correlations are needed to validate this conclusion.
Future work: More fields, larger plots, Tassel cap transformations, online tools