Most individuals will file a 1-d-1 Ag Exemption with their county upon purchasing the property or upon the chief appraiser's written request. The 1-d Ag Exemption is the original ag exemption that gave farmers a break on their property taxes that uses your farm income to determine the value of the property when agriculture is the property owner's primary occupation and source of income. The 1-d Ag Exemption should only be used under certain circumstances, does not have a minimum size requirement for the parcel of land, and takes 3 years to establish the history instead of the (5) you hear from most CADS. Most individuals will not qualify for the 1-d Ag application and must use the 1-d-1 Ag Exemption.
THE FULL MANUAL FOR APPRAISAL OF AGRICULTURAL LAND CAN BE FOUND BELOW. There are a few more details and things your can learn more about here:
https://comptroller.texas.gov/taxes/property-tax/docs/96-300.pdf