Glyphosate - experiments

Our glyphosate pages: Overview | Sites | Experiments | Methods | CRC Hydrology

Our “experiments” were routine agronomic glyphosate sprays in spring and other seasons, followed by stormwater runoff sampling. There has been no specific spraying simply to trace glyphosate. Most spraying has been to eliminate competing plant types from plots that were intended to house a single grass species, and in one case the spraying was to change crops without cultivation. Since the crop species are not engineered to be glyphosate resistant, the spring spraying must happen before the desired crop begins to grow again, thus is effective against only earlier-emerging plants. Three tables below present the plots, the spraying history of the site through spring 2018, and sampling history.

CRC plots

CRC site plots A-R with topography, watershed, recurring sampling points

The various plots are:

Plot ID Crop Area (ac) Frac in
watershed
A Control 0.833 0.983
B Switchgrass 0.837 0.985
C Reed-Canary, then Switchgrass 0.837 1.000
D Switchgrass 0.837 1.000
E Reed-Canary, then Switchgrass 0.833 0.975
F Switchgrass 0.848 0.888
G Switchgrass 0.875 0.845
H Switchgrass 0.901 0.818
I Control 0.915 0.802
J Switchgrass 0.930 0.761
K Switchgrass 0.928 0.727
L Reed-Canary, then Switchgrass 0.970 0.700
M Switchgrass 1.025 0.655
N Switchgrass 0.933 0.696
O Reed-Canary, then Switchgrass 1.091 0.673
P Control 1.083 0.641
Q Miscanthus 0.400 0.423
R Miscanthus 0.400 0.308

We sprayed glyphosate each year at least once:

Year/ season Plots sprayed kg AI in watershed Comments
2014 May B,D,G,H,J,K,M,N 4.08
2015 May B,D,G,H,J,K,M,N,Q,R 2.85
2016 April B,D,G,H,J,K,M,N,Q,R 4.28
2016 July C,E,L,O 2.14 Killing reed-canary grass for crop change
2016 October C,E,L,O 2.85 Killing reed-canary grass for crop change
2017 April C,E,L,O,Q,R 2.34
2017 June C,E,L,O 2.14
2018 spring All except controls (A,I,P) 6.4

The glyphosate sampling campaigns in these years were as follows:

Year and season Number of samples Comments
2014 spring CRC Weir: 226 Pilot year, few samples analyzed
2015 spring CRC Weir: 104
CRC Tile: 94
First round with USGS collaboration
2016 spring CRC Weir: 124
CRC Tile: 126
2016 fall CRC Weir: 49
2017 spring CRC Weir: 84
2018 spring CRC Weir: 175
CRC Tile: 1
Freese: 2
2018 summer and fall CRC Weir: 166
CRC Tile: 3
Freese: 69

Last updated 2023-09-21 sp17 AT Cornell.edu.