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Units of measure in agriculture explainedBy D. Bruce Bosley CSU Extension agent, cropping systems Colorado The units of measurement we use in agriculture demonstrate very well how to make things confusing to a new learner, be they a new immigrant or in teaching our own children. Take one unit of land measurement for example; an acre is a two-dimensional land measurement made up of 43,560 square feet. Its square root defies description in feet and inches (about 208). Where did this unusual number arise? An acre is an old English word meaning the area of a field that a peasant or yeoman farmer and a team of oxen could plow in a day. An acre is simply 4 rods wide by 40 rods long, or put another way, 1 chain long by 10 chains long. This definition simplifies nothing to most Americans. What exactly is a "rod" or a "chain?" By definition, a rod is 16.5 feet (or 5.5 yards). Four rods make up one chain (66 feet). In Elizabethan England, the measures of a standard acre were a rectangle 66 feet wide and 660 feet long. Using these measures, a mile is 80 chains long (80 times 66 feet). A square mile is 80 chains long by 80 chains wide. Knowing that an acre is 10 square chains in area is the reason for why there are exactly 640 acres in a square mile ((80 chain by 80 chain)/10 chain 2/acre). In the metric system, land is measured in hectares. One hectare is a perfect square 100 meters on a side. 100 hectares fit within a square kilometer, ten hectares on a side. Our measurement of yield for crops provides another example. We measure field crops by weight such as hundredweights of dry beans, tons of sugar beets, and pounds of sunflower. However, we still measure grain in bushels. A bushel of corn is supposed to weigh 56 pounds, wheat 60 pounds, barley 48 pounds, millet 50 pounds, and oats only 32 pounds. The area of a bushel is 2150 cubic inches. One bushel is four pecks (a peck is 537.5 cubic inches). Some people remember when two gallons equal a peck and if 4 pecks equal a bushel then 8 gallons would equal one bushel in volume. However, we normally measure liquids in gallons while measuring dry material in bushels. The measure for wet gallons is 231 cubic inches but the measure for a dry gallon is 268.75 cubic inches. Which reminds me, ordering a pint of ale in England will get you a 20-ounce beverage instead of the 16-ounce pint one would expect. Currency conversions are hard enough. Fortunately, a pint of wine in that same pub is the same 16-ounce pint measured in the U.S., but why would anyone order English wine? Finally beware of hundredweight. In the United States, a hundredweight is 100 pounds. The English hundredweight is eight stone or 112 pounds (a stone is 14 pounds). It follows that our ton weighs 2,000 pounds but in England, they weigh a tonne as twenty English hundredweight or 2,240 pounds. Meanwhile, only a few Americans know that the legal definitions of the English customary units are actually based on metric units. Fortunately, the U. S. and British governments have agreed that a yard equals exactly 0.9144 meter and an avoirdupois pound equals exactly 0.45359237 kilograms. The fact is that we in the United States are officially a metric nation too. What are the chances of encountering anyone in rural or urban America to agree that we use anything but feet and inches, or pounds and ounces? Two websites where one can learn more are: www.footrule.com, and muextension.missouri.edu/xplor/agguides/crops/g04020.htm. Please contact me, Bruce Bosley about this or other cropping systems or natural resource topics at 970-522-3200, extension 285 in Sterling or 970-542-3540 in Fort Morgan. 11/24/08 Date: 11/14/08 Advertisement
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