If it was the Harvest Champion boost you activated, for three hours after activation you can collect double crops. For maximum effectiveness of this boost, you should have your crops ready for collection when you activate this. And then plant another crop(s) that will be done growing prior to the boost expiring.
The Nimble Farmer boost speeds up growing time for three hours. This effectively reduces the growing time of longer growing crops by three hours. Ie a 21 hour crop will be ready in 18 hours.