Translation: The imagery of the ripe harvest and the sickle comes from the Bible rather than the Mesoamerican experience. Joseph might have picked up this imagery from either Joel or Revelation:
Put ye in the sickle, for the harvest is ripe: come, get you down; for the press is full, the fats overflow; for their wickedness is great. (Joel 3:13)
And another angel came out of the temple, crying with a loud voice to him that sat on the cloud, Thrust in thy sickle, and reap: for the time is come for thee to reap; for the harvest of the earth is ripe.
And he that sat on the cloud thrust in his sickle on the earth; and the earth was reaped.
And another angel came out of the temple which is in heaven, he also having a sharp sickle.
And another angel came out from the altar, which had power over fire; and cried with a loud cry to him that had the sharp sickle, saying, Thrust in thy sharp sickle, and gather the clusters of the vine of the earth; for her grapes are fully ripe. (Revelation 14:15–18)
Reaping with a sickle was likewise familiar to Joseph as an American farmboy (the same image appears in Doctrine and Covenants 4:4), but it would not have been natural for Mesoamerica. Of course Mesoamerican farmers had harvests that ripened in their fields, but they did not have sickles. Sickles are curved blades suitable for harvesting grains that grow on long flexible stalks. Corn, the principal food of the New World, is harvested differently. The ears are pulled off by hand; and stalks, if they are not left standing, are chopped down with a bladed instrument like a machete in more recent times.
Ammon’s verse should be read as another example of Joseph’s reaching for an image familiar to him from the Bible to explain the harvesting image from the plates. (Of course it is possible that Ammon alluded to Joel, but that seems unlikely, given the cultural distance that would have separated them.)
Vocabulary: A garner is a storage facility for grain, a granary.