In Spain and the Spanish-speaking world, the “fanega” or “fanegada” represents various units of dry capacity, mass and land area. Originally, the fanega was a unit of dry capacity used for grain. It was also a unit of area, the amount of land that would be sown with a fanega of seed. http://www.sizes.com/units/fanega.html. The fanega as a unit of land area in Spain, as reported in the 19th Century for Málaga = 8,640 square varas (6,037.0891 square metres). Also see: http://www.unc.edu/~rowlett/units/dictF.html. In 1801, it was standardized in Spain as the area of a square equivalent to 96 varas (80.2 meters) on a side; this equates to 0.643 hectare (1.59 acres). After the introduction of the metric system, it became customary to refer to an area 80 metres square as a fanega. This unit is not legal, but is still used informally in some parts of Spain. The Central American manzana is a counterpart of this traditional Spanish unit. An “are” is equivalent to 100 square metres, while the “centiare” (also spelt centare) is a unit of area, equal to 1 square metre.

HTH!