China is set to host the winter Olympics in 2022. While Beijing may not have much snow, the country does have a big mountain — built of corn.

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Lured by high prices topping $9 a bushel, Chinese farmers did what any good grower would do: planted corn, a lot of it. Acreage rose by almost 45% over the last decade. While yields are still paltry compared to the U.S., production still rose 60%.

Huge reserves could limit imports and cast shadow on sorghum boom

To be sure, Chinese farmers needed more corn to feed a rising middle class, and the processing industry boomed, too. But supplies still grew. And grew. Officially, USDA says China will have more than 3.55 billion bushels of corn left over from a record crop of 8.85 billion bushels. Other estimates put its government-owned reserves close to 6 billion bushels, enough to last 250 days, with some saying the government has a full year's supply. By contrast, the U.S. is expected to have only a 42-day supply on hand when the 2015 crop marketing year ends Sept. 1.

If high government-support prices, overproduction and bulging government reserves sound familiar, just recall U.S. farm policy until 1986. China's leaders say they want to embark on reforms, too. That could be good for U.S. growers in the long run. But until the country's massive stockpiles are cut down to size, hopes remain elusive for a corn export boom that could match what happened with soybeans.

Moreover, changing government policies could squelch the rebirth of the U.S. sorghum industry, one of the few bright points in the grain trade for 2014 crops. That alternative feed grain could be caught in the crossfire of China's new policies.

Direct payments >>

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Direct payments

Even the baby steps the government announced for 2015 crops could echo large in the market.

The government's goal is to eliminate the high price it pays for corn to accumulate reserves, and move to a system of payments made directly to farmers. It's tried these measures, with mixed results, for cotton and soybeans. But a proposal for steep cuts to corn triggered a howl of protest. Instead, the government said it would trim the price it pays by 10%, taking it below $8, still an unpopular measure when laid-off factory workers are returning home to their villages.

But the price might be low enough to persuade end users to begin buying government reserves more enthusiastically. Auctions at higher prices for the 2014 crop drew little interest, despite subsidies the government offered to its struggling processing industry, where more than half the capacity is shuttered.

Instead, those companies turned to imports. China allows a small amount of corn imports, capped at 285 million bushels for 2016, to come into the country with a low tariff of just 1%. But importers must first buy grain from government reserves, limiting their use. Otherwise, a tariff of 65% is slapped on corn imports. Even at this fall's low U.S. corn prices, the tax would be enough to make government reserves competitive with U.S. imports.

Related: U.S. ag prices remain under pressure

Chinese companies got around the restrictions last year by turning to other feed grains, including barley and sorghum, which enter the country duty-free. U.S. sorghum exports exploded to a record 350 million bushels. Growers responded with a 22% increase in acreage, and plan another increase in 2016, according a Farm Futures survey.

But while USDA forecasts a big increase in exports for 2015, there are fears China is cracking down. Sales slowed dramatically this summer, for one, eroding premiums over corn back to their normal 10- to 25-cent discount.

In the meantime, Chinese imports of U.S. corn last year totaled only 19 million bushels. Ukraine captured some of the business, exporting 168 million bushels under a long-term agreement to provide grain in return for loans. That deal hasn't turned out to be a cakewalk for either side. Ukraine almost defaulted on one deal due to its financial troubles in 2014, and recently tried to renegotiate terms, fearing China's economic problems could decrease its imports.