I did my PA6 about 15 years ago. I remember that I had calculate how much water I would need to spray a test area, and then put in extra litre of water. This way you couldn't tell my the weight or 'sloshing' how much was left, and at the end of the test you then had to empty out what was left...
Considering that all approved pesticide registrations have to be supported and re-supported by actual data from the field, then I think almost all farmers who are using pesticides are going to benefit from helping test new and existing products. Obviously, hosting trials are not for everyone...
Data from the US suggests these actives control barnyardgrass. I don't know what rates, and obviously this is not a recommendation, and it depends on the crop