The loan can be exempted from reporting under the farm exemption in HMDA if it was to be used for an agricultural purpose. Acreage does not come into play when determining the use of the property. HMDA gives you the option of using RESPA's 25 acre rule as a determining factor if needed on a case by case basis. But the property does not have to be greater than 25 acres to meet the HMDA exemption.
Now with that said, boarding horses and giving riding lessons does not IMO meet the definition of an agricultural purpose. Therefore I would opine the loan is not exempt.
6. Agricultural purpose. An agricultural purpose includes the planting, propagating, nurturing, harvesting, catching, storing, exhibiting, marketing, transporting, processing, or manufacturing of food, beverages (including alcoholic beverages), flowers, trees, livestock, poultry, bees, wildlife, fish, or shellfish by a natural person engaged in farming, fishing, or growing crops, flowers, trees, livestock, poultry, bees, or wildlife. The exemption also applies to a transaction involving real property that includes a dwelling (for example, the purchase of a farm with a homestead) if the transaction is primarily for agricultural purposes.
_________________________
The opinions expressed are mine and they are not to be taken as legal advice.