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Mathline

Keith Jolley, Farmer from Jamaica, IL

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Keith JolleyThere is a lot of mathematics in farming! With farming, you have to able to use different areas of mathematics, such as weights and measures, addition, subtraction, multiplication, division, rates and ratios, geometry and area, interest rates, and taxes.

We farmers do quite a bit with conversions. For example, grain has always been sold in bushels. However, when we harvest a field, we know the weight of the corn or soybeans we’ve brought in. So we use the fact that a bushel of soybeans weighs 60 lb. and a bushel of corn weighs 50 lb. to calculate how much of each we have to sell.

The size of a field is measured in acres. An acre is equal to 160 square rods. (These are very old measures that farming has carried through the years.) A rod is equal to 16 1/2 feet. That means that an acre is 43,560 square feet. All farmers know how long and wide their fields are and use that to convert feet into acres.

When we plant corn, we like to plant about 30,000 seeds per acre. With beans, we plant about 18,000 seeds per acre. There are new planters now that will tell us as we drive through the field how many seeds per acre we are planting. However, it is still good to check how much we’ve planted by digging up a small area and counting the seeds that have been planted there. Once we know how many seeds per foot are being planted in that row and how close the rows are, we can do the math to figure out if we are planting the right amount (and if not, what type of adjustments we need to make).

With fertilizers, we generally spread 200-400 lb. per acre. We run soil tests to determine how much of which fertilizer we need. Now there are new spreaders with computers that allow us to enter a map of the field that it will use to adjust the amount of fertilizer it applies as we drive along. We are also starting to use farm machines that are linked by satellites. Right now, however, those are still pretty expensive.

Farmers also have to know mathematics to think about interest rates. There is quite a difference between 6.5% and 14%. We also use mathematics when deciding what to plant and when to sell. We watch the prices. It is kind of strange. If it rains in Brazil, then the price of beans drops. It takes something really good to happen to make the prices go up. But that’s farming!