"The average yield of corn was about 25 bushels per acre in 1860. [Laughs.] It hadn't changed in the next 70 years. It had gone up just slightly, very, very little. And then when hybrid corn came in, the first few years it actually, yields went down because of that huge drought that covered a large part of the country. So in the middle 30s the average actually dropped even though we were beginning to use hybrid corn, the average dropped. But then for the next, well since then on the average we've increased a little over 100 bushel an acre. So, there's been a better than average increase of a bushel per acre per year. And that hasn't been uniform either. The first 20 years of hybrid corn, we were in what are called 'double-cross' hybrids.
     "Hybrid corn are crosses of inbred lines, OK? Lines that have been inbred for a period of six or seven years. During the course of that in-breeding they become pure lines, but they also become much less vigorous and low-yielding. When you crossed two of these low-yielding inbreds together – each one [of the inbreds] might yield 20 bushels per acre, something like that – when you made that cross and planted the seed, the yield was 100 bushel an acre.
     "So, there was a huge genetic explosion that happened when those two lines were crossed. 1904 was when the first discovery was made of this genetic explosion they called hybrid vigor… The two are planted in the same field, side by side. The one line is detasseled. The male part is the tassel, and that is pulled off by hand so that there's no tassel or no pollen that's produced on that line. The other line is used as a pollen parent. That's the male part of the plant… So one line becomes the male parent and the other line becomes the female parent. And the only pollen that's in the field then comes from 'Inbred B.' So, when that seed is harvested, then, only the female is harvested. And that is used as a seed parent. It took until 1917, when somebody figured out how to put four inbreds together. Cross two inbreds together that were low-yielding to produce a high-yielding single cross. And two other inbreds together to produce another high-yielding single cross. And those two together to produce a four-way cross, or double-cross. That's what farmers were using. That made hybrid corn practical, when Henry Wallace decided to go into the seed business in 1926."

Stan Jensen on Crop Yeilds

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Other Excerpts from Stanley Jensen's Interview:

Killing Grasshoppers
Pests Thrive In Dry Climate
Hybrid Corn
All in the Same Boat
Working for the WPA
Growing Up Poor
Radio, Isolation and Entertainment
Getting Electricity
The Amenities of Home
Ethnic Communities
Keeping the Dust Out