It usually refers to cereals that have stem, such as wheat, barley or rye. Spike, grain, aggregate. Also used to denote the action of harvested cereals or grains. Mowing, harvesting.
Mies: ( 41 harvest; trim the fruit. collect, mowing or cutting fields. 2. grain to make bread.
The product of the field is much, talking about indicating the Bilblia " the harvest is plentiful and the workers are few ". It means that the product of the field is long and few workers to pick up the product.