This achievement is cumulative across all games and modes. Each piece of corn you collect counts as 10 towards the achievement (if you have v1.2 patch), so effectively you only need to collect 100,000 corn to unlock this. This should only require minor grinding (a couple of hours or less) after you gold all the levels. Remember, you can check your progress in the achievement screen.
Occasionally, as was the case in June 2012, the corn can be boosted in a Weekly Challenge that has very few obstacles. In this case, you can leave your phone running continuously in the challenge and rack up the corn while sleeping or doing anything else. Each week you can try the challenge to see if you can rack up points without touching your phone.