Before you can use land to raise organic products, you must stop applying inputs like fertilizers and pesticides that are prohibited in organic production and handling.

To complete your transition to organic, your farm or ranch cannot have used any of these substances in the last three years.

https://www.ams.usda.gov/services/organic-certification/transitioning-to-organic

Doesn't matter what crop it is. Organic certification is 3 years.