A manure spreader, pictured in Emmet County, Iowa in 1936. Credit: U.S. Library of Congress

That was a question asked by farmers in 1920. And scientists at the Iowa State University (ISU) agriculture experiment station at Ames had an answer. Scientists at the facility tested several soil types throughout the state to find an answer to the critical question that was on farmers’ minds at the time.

The scientists found all crops were improved with the use of manure. They determined that the corn yield was increased 11.4 bushels per acre by the application of eight tons of manure once in a four-year rotation of corn, oats and clover. Figuring corn at $1.40 per bushel meant an increase of $15.96 per acre with the application of the smelly stuff. On the same soils the oat crop increased 17.1 bushels per acre which amounted to an increase of $13.68 per acre. (Oats were selling for 80 cents per bushel.) And clover increased in yield by $10.50 per acre.

The scientists concluded that the total increase in yield with the use of the eight tons of manure over the four year period amounted to $55.65. That made one ton of manure worth $6.96 according to the ISU agriculture scientists. (The dollar in 1920 was the equivalent of about $12.42 in current value—considering inflation rates over the years.)

Credit: U.S. Library of Congress

They could say nothing but good things about the use of manure by crop farmers. They claimed the “physical effect of the manure on the soil” was extremely beneficial. According to the studies conducted by the scientists the use of manure “opened up heavy soil” and made “light soils more compact and more retentive of moisture.”

They said with “proper care in storing” manure could return as much as 85 percent of the plant food taken from the soil by the crops. And, they predicted, “the time when the addition of artificial fertilizers will become necessary will be far in the future.”

©Cheryl Mullenbach

Read other Iowa Stories and learn more about author Cheryl Mullenbach at http://www.cherylmullenbachink.com/.

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