Some Corn Belt values have seen their sharpest price jumps ever. Crop prices have been good. Interest rates have been low. Farm incomes have been healthy. Makes for a healthy outlook for farm land values, right?

There is bad news, though. Interest rates can't get much lower. There's a lot of uncertainty about this year's crop yield potential. And, both fixed and variable costs to raise corn and soybeans continue rising.

Add it all up and it's certainly not the end of the bull run for farm land prices, but it's reason for more caution in pricing new land than in recent years, says director of the Purdue University Center for Commercial Agriculture and ag economist Brent Gloy. Ultimately, it's best to take a longer-term view of both land values and your ability to keep up with them instead of remain beholden to a shorter-term perspective.

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"In the short term, people will buy [land] because they think it's going to go up, and that's where we get concerned," Gloy told Agriculture.com. "I think there are a lot of people who may be optimistic about earnings in the future but are still tying the value of what they're paying for the land for the earnings they can get off of it."

Right now, grain exports, already-tight grain stocks and interest rates are all looming large for the land market. And, all these largely bullish variables -- especially grain exports right now -- could turn on a dime at any time, making it difficult to track them effectively on a short-term basis, he says.

"The scary thing about farmland and agriculture in general right now is when you start talking about exports being so important. They tend to grow over time, then change dramatically. Those can really shock things," Gloy says. "Those are the hard things to forecast."

The grain market saw a perfect example of this scenario play out over the weekend when officials in Brazil took action to close its ports to soybean exports in an effort to keep up with orders amidst a new-crop supply shortage. After a lower start to the trade Monday, the grains moved higher on the prospect of more sales of U.S. soybeans on the export market.

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"For 20 years, we've been saying China's going to import all these ag products, and all of a sudden, they really get an appetite for our commodities," Gloy adds. "We knew that they'd likely buy more, but when and how much is tough to estimate."

Instances like these are bullish. But, there's also a lot of bearish potential out there too, Gloy says, namely the movement of already-low interest rates higher. Then, there are variables that could go either way.