Easiest one is Turnipseed Farm.
This is the first challenge of the game to unlock.
You need to stay as close as possible to the abduct-o-beam, whilst picking up cows with
and then holding
and releasing to fire them in to the beam, They must be alive. Ignore farmers trying to kill you.
If you want to be able to lose ground on the beam a little, upgrade your PK, which will then allow you to throw things slightly further (Cows count as light objects). Throwing 65 Successfully in to the beam before time runs out, nets you this trophy.