* Stand: A stand of wheat, a stand of corn
* Field: A field of sunflowers, a field of barley
* Harvest: A bountiful harvest of grapes, a successful harvest of tomatoes
* Planting: A new planting of potatoes, a thriving planting of carrots
* Growth: A healthy growth of beans, a vigorous growth of rice
You can also use more general collective nouns like:
* Array: An array of crops
* Assortment: An assortment of vegetables
* Variety: A variety of fruits
The best collective noun to use will depend on the specific context and the type of crops being referred to.