Whether new investors are causing the market’s problems or keeping them from getting worse is in dispute. But there is no question that the grain markets are now experiencing levels of volatility that are running well above the average levels over the last quarter-century.

Mr. Grieder’s crop insurance premiums rise with the volatility. So does the cost of trading in options, which is the financial tool he has used to hedge against falling prices. Some grain elevators are coping with the volatility and hedging problems by refusing to buy crops in advance, foreclosing the most common way farmers lock in prices.

“The system is really beginning to break down,” Mr. Grieder said. “When you see elevators start pulling their bids for your crop, that tells me we’ve got a real problem.”

Until recently, that system had worked well for generations. Since 1877, grain producers have been able to hedge the price of their wheat and corn crops on the Chicago Board of Trade through the use of futures contracts, which are agreements to buy or sell a specific amount of a commodity for a fixed price on some future date. Soybean futures contracts were introduced in 1936.

More recently, the exchange has offered another tool: options on those futures contracts, which allow option holders to carry out the futures trade, but do not require that they do so. Trading in options is not as effective a hedge, farmers say, but it does not require them to put up as much cash as is required to trade futures.

These tools have long provided a way to lock in the price of a crop as it is planted, eliminating the risk that prices will drop before it is harvested. With these hedging tools, grain elevators could afford to buy crops from farmers in advance, sometimes a year or more before the harvest.

But that was yesterday. It simply is not working that way today.

Futures, for example, are less reliable. They work as a hedge only if they fall due at a price that roughly matches prices in the cash market, where the grain is actually sold. Increasingly  for disputed reasons  grain futures are expiring at prices well above the cash-market price.