43 CFR §2530.0-8

1. (a)General.
   1. (1)The law provides that allotments may include not to exceed 40 acres of irrigable land, 80 acres of nonirrigable agricultural land, or 160 acres of nonirrigable grazing land.
   2. (2)Irrigable lands are those susceptible of successful irrigation at a reasonable cost from any known source of water supply; nonirrigable agricultural lands are those upon which agricultural crops can be profitably raised without irrigation; grazing lands are those which can not be profitably devoted to any agricultural use other than grazing.
   3. (3)An allotment may be allowed for coal and oil and gas lands, with reservation of the mineral contents to the United States.