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The drought has made it tough to glean much of any crop data from this year to put to reliable use for next year's corn and soybeans. The moisture shortage frankly made it difficult for any single cropping system, input, or management tactic to stick out as a big winner.
Continuous corn is one of those systems that saw some pretty lackluster results in 2012, and while it may not be enough to convince some farmers from straying away from it, there are others who you'll be hard-pressed to find planting corn-after-corn in years to come. Does that mean it should automatically be out of the running for a spot in your cropping plans for next year? It has its own unique risks, but if you're in a position to manage those as well or better than the milder risks of a traditional corn-soybean rotation, experts say you shouldn't rule it out based solely on 2012.
Pest pressures, residue management, and soil drainage are all conditions that can trim your yields if you opt to plant continuous corn. This year, those were more easily managed due to the lack of moisture, says Dave Rahe, a certified crop adviser and soil scientist with Soil-Right Consulting Services, Inc., in Hillsboro, Illinois. So, it's tough to gauge how those variables will return during the 2013 crop year.
"One of the shortcomings of growing more corn than soybeans is disease pressure. Another is insect pressure. It seemed that dry weather kept diseases to a minimum, but not rotating certainly adds to the risk," Rahe says. "Another issue could be nutrient cycling. Decomposing crop residue could be an issue. The carbon in the residue ties up the nitrogen in the soil. Keep in mind that the residue on the top is probably not a big issue, but roots and buried stalks do need nitrogen to start that decomposition process. Drainage is generally an issue in corn after corn. That issue is unlikely this year, but we did have good moisture in March and April, at least in my area."
Managing the nutrient load in that residue in continuous-corn acres will be more of a challenge moving from this year to next year's crop, adds University of Illinois Extension agronomist and crop scientist Emerson Nafziger. If your crop suffered damage severe enough to curtail plant growth as early as the middle of the growing season, the residue left will likely be much softer. The good news is that will make it easier to break down next year. But the bad news is if you decide to return with corn instead of rotating with soybeans, your yields will still likely fall well below normal.
"Corn that stops growing in midseason does not produce much lignin, so its residue is softer and it breaks down faster. Lower quantities of softer residue will also present less physical challenge to the planting operation," Nafziger says. "This is not a suggestion to plant more corn and fewer soybean acres next year. Corn following corn is showing more stress effects again this year. So even though a field with a short corn crop this year may be more corn-friendly than normal next year, it is still unlikely that corn following a corn crop -- even a low-yielding one -- will yield more than corn following soybeans."
Yields to expect
Continuous corn will almost always yield less than rotational corn. Experts agree on that. But that's not true in every field, and even where yields did lag further behind than normal, farmers are still considering it for next year.
"I have been tweaking my rotation a bit the last few years. I want to put one patch in continuous corn. Will I change my mind? It doesn't look like soybeans are yielding there very well," says Agriculture.com Marketing Talk adviser Jim Meade / Iowa City. "I will have a few acres of corn-on-corn as part of the rotation adjustment and will have to pay the price for that."
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That price typically adds up to a yield hit of about 10% compared to corn after soybeans, Rahe says. But, if you have a 10% lower corn yield for several years, it can all of a sudden become an economic hurdle.
"I have heard lots of people say they do not have that problem, but six years in a row with even performance and then a year with a 60- or 70-bushel hit would certainly set your average back at any yield level," he says. "Does this mean you should not grow long-term corn?Certainly you should consider the consequences."
In central Illinois, Nafziger says continuous-corn results have been mixed. But then again, so were all yields. "Corn-on-corn didn't really look much worse. Some people said it was OK," he says. "I suspect corn-on-corn may have yielded 100 where corn after soybeans made 120."
Because of the relative speed of most of this fall's corn and soybean harvest, farmers are already thinking about their 2013 planting decisions. In a recent Agriculture.com Crop Talk poll, 54% of farmers say they're sticking to their normal crop rotation plans whether or not they include continuous corn. Only 15% say they'll plant more corn. But, the numbers don't mean that corn-on-corn will take much of a hit, Rahe says. How well it performs in any given operation depends on how it's managed.
"We have one customer who has grown corn continuously since 1954. Am I going to tell him to switch off? I don't think so. I look at what he is doing. He maintains high soil test levels. He has well-tiled fields. I bet he watches which hybrids work best in continuous corn. You also need to take preventive measures for disease and insect repression," he says. "If you decide to go for it, do so with realistic expectations. If you can't stand the risk, then switch to a corn-soybean rotation."
Those expectations are almost as important as how the crop is managed in general, adds Nafziger. As long as you know that you'll face some additional unique challenges and will need to manage your continuous corn acres differently than corn-following-soybeans, you can make it work.
"I'll be surprised if anyone says corn-on-corn was better or as good as rotational corn," he says. "This will be the third year in a row where corn-on-corn has done not too well throughout a good chunk of central Illinois. But, corn-on-soybeans didn't do much better.
"Corn-on-corn won't suffer in our minds and hearts."