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 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.