Here are some possibilities:
* Crops: Wheat, corn, soybeans, cotton, rice, barley, oats, sunflowers, fruits and vegetables.
* Grasses: Clover, alfalfa, fescue, ryegrass, bluegrass.
* Wildflowers: Daisies, poppies, wildflowers.
* Trees: In some cases, fields can be used to grow trees for timber or fruit.
* Flowers: Fields can be planted with beautiful flower arrangements for landscape or commercial use.
* Nothing: Sometimes fields are left fallow or are awaiting planting.
To give you a more specific answer, tell me:
* What kind of field is it? (farm field, meadow, wild field, etc.)
* What is the climate like?
* What is the soil like?
Knowing these details will help me determine what might grow in the field!