(property tax assessment case in which petitioners sought 13-acre property reclassification as agricultural land; property reclassified because it did not have 10 or more acres used for raising or cultivating an agricultural product; petitioners began building horse boarding stable themselves and planted forage so sought reclassification; reclassification denied because statute required agricultural products to be produced the year before assessment and petitioners failed to establish any agricultural use in prior year because no boarding and forage planted after year for which reclassification was sought).