I'm confused. You quoted this from Penn State:
Waterfowl can be repelled by almost any large foreign object ...
While I agree that sparc asking the farmer who placed the pallets originally would be insightful, it seems he may be using the pallets as "foreign large objects" to keep the geese wary of the field. Now it appears, the farmer has replaced the pallets with other temporary deterrents.
The geese, we must remember, have a choice: land in a field with pallets, or land in a field with no pallets. Also, it must be considered that it doesn't matter when the pallets are placed, only that they are present when the geese are making their choices.
Are there agricultural economist studies that analyze the trade-offs between geese eating and pooping, and no geese? Surely, this would get you a Nobel?