The longer-term story is tied to the shaky Ukrainian economy. Experts worry that Ukrainian farmers may not be able to get credit to plant this spring, hitting companies that make and sell seeds, or sell equipment and chemicals. Moreover, an unstable economy can wreak havoc on agricultural innovation—after Khrushchev's visit to Iowa, the reality of Soviet economics made an immediate transition to Western farming equipment difficult. Ukrainian agriculture could also be hurt in the short term by labor shortages if farmhands are diverted to resist Russian incursions, Cox said.
"The growth aspirations for the seed companies in the Ukraine are critical," said one analyst who was not authorized to speak on the issue because he had not written a public note covering potential fallout from the geopolitical standoff.
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DuPont's citing of Ukraine in a recent regulatory filing warning of potential weakness to quarterly earnings also included a reference to bad weather in the U.S. as a culprit, and DuPont expressed confidence it would meet its targets for the full year. Monsanto spokeswoman Sara Milller said Ukraine is only a small part of its $2 billion European sales segment—the company does not break out Ukrainian revenue. Monsanto makes about 40 percent of seeds for Ukraine's market within the country.
"We're continuing to carefully monitor the developments like everyone else,'' Miller said via email.
The Ukrainian corn crop is set to be planted in May, and nearly all of it would normally end up on the export market, Cox said. Wheat gets planted in the fall, giving more time for the crisis to be resolved.
"If there's war, all activities will be disrupted,'' said Evgenia Apostolopoulou, a senior consultant at IHS Chemical in London.
Iowa farming innovator Garst had a political reason for inviting Khrushchev to his family farm. He had been to Communist nations throughout the 1950s—and had previously visited Khrushchev in the Soviet Union—trying to spread his message of agricultural revolution to feed the hungry masses behind the Iron Curtain and bridge U.S.-Soviet differences—through a corn détente.
It's the wrong seeds of change, though, at work in Ukraine right now.
—By Tim Mullaney, Special to CNBC.com