What happens in a field of small grains before the main harvest?

Les explains that in a field of small grains—barley, wheat, oats—before the main harvest, while the field is still green and all headed out, scattered heads of grain turn yellow and ripen early. These early ripening heads have ripened before the mass of the other stems around them. The Jews were instructed to go into that green field, pluck those early ripened stems with the heads, enough to make a sheaf, and bring it to the priest as a wave offering. This was the firstfruits. He connects this to Leviticus, where Scripture says, "When you are come into the land, and ye shall reap the harvest, you shall bring the firstfruits to the priest." Barley was their first grain to be harvested in the spring. He tells his audience to file this in their computer.