Early planting priority: Corn or soybeans?

By Dusty Sonnenberg CCA, Ohio Field Leader, a project of the Ohio Soybean Council and soybean check-off and Matt Reese

At least on some farms, there has been a shift in recent years prioritizing planting soybeans first. In a few conversations that were part of the 2022 Ohio Crop Tour, it was suggested that planting soybeans earlier may have paid off last year.

“The early planted beans look good and the later beans are just so-so. There has been more of a push lately to plant your soybeans first, or at least earlier. This year may be an example of that working out,” said Grant Davis, Agriculture and Natural Resources Educator with Ohio State University Extension in Champaign County after sampling fields for the 2022 Virtual Crop Tour. “A lot of this later planted corn looks pretty good where the later planted beans don’t necessarily. I think there may be greater upside potential for planting beans earlier if you get the opportunity and maybe, if it comes down to it, push the corn back if you have to. There seems to be less of a penalty for doing that for corn than there is for beans this year.”

In many cases, the way the weather played out last year favored those early planted soybeans while the heat and rains worked well for corn planted a bit later than would normally be preferred. Ultimately, the yield monitors told the tale. But with so many nuances, it still remains unclear, year in and year out, the best early season planting priority.   

The issue is the subject of numerous research efforts. Mike Hannewald, a Beck’s Hybrids agronomist, said early planting of corn and soybeans has been part of their Practical Farm Research (PFR) trials for several years. 

“You know when you look at our data, whether it’s from Ohio State planting date studies, or Beck’s PFR studies — we got over 20 years of data — it pays in both corn and beans to plant early on average over multiple years. But the interesting thing is that the beans are much more consistent in the early planting dates where corn is a lot less consistent. For corn, it depends on what conditions you planted into and then also what the weather was at pollination timing. We obviously don’t know and can’t control what the weather is at pollination timing, but we can control the conditions that we plant into,” Hannewald said. “When it comes to deciding whether or not to plant corn or beans, if you’re questioning if you want to get out there early and you might be pushing the limits a little bit as far as the temperatures or the soil conditions, which crop should you be planting? If you went out and planted say 160,000 soybeans per acre and then you got a final stand of 120,000, would you be happy with that? Most farmers would say yeah of course they’re happy with that. But if we look at corn, if you go out and plant at 32,000 plants per acre of corn and you get a final stand of 24,000, are you happy with that? Well of course not! You’re thinking about tearing it up at that point. Both of those figures are a 25% stand reduction.”

With this in mind, Hannewald suggests that, when in doubt, it is a safer bet to plant soybeans first.

“If things aren’t perfect when we plant the beans and they’re a little bit more inconsistent coming up, they can adapt so much better than our corn crop. Soybeans are able to branch out more to fill in the gaps and we can still produce a good soybean crop. If we don’t get that perfect picket fence stand with corn, it is a lot bigger of a difference maker. So, if you want to go out and plant early, and you feel like you’re pushing the limits just a little bit, at least be pulling the bean planter and you’ve got a lot higher chance of success,” he said. “The biggest thing is just being smart about the conditions you’re planting into. We’ve still got to be smarter about when we go out and plant that we’re not pushing the envelope of being too wet or planting into the mud or right ahead of a heavy rain, but the beans do tend to be a little bit more forgiving than what corn is. We can afford to give up a few more beans and still produce a good crop. If you get the chance to plant beans early, definitely do it because our multi-year data says that you’ll be rewarded for that.”

The early planting question is also part of ongoing Ohio State University Extension research. For the last two years, in two separate locations, a study has been conducted to determine how early soybeans can be planted in Ohio. In the past, studies have looked at early planting at the end of April or early May. Laura Lindsey, OSU Extension state small grains and soybean specialist, is looking at an earlier planting date than the past, and also the interaction between very early planting and the presence of cover crops.

“The past two years we were able to plant soybeans for this project in Wayne County during the first week of April, and last year in Clark County we were able to plant the soybeans on March 30,” Lindsey said. “We really wanted to see how early we can plant soybeans. Almost every agronomist will tell you that it is important to plant soybeans early.”

The other aspect of this research project is the interaction of planting early, and cover crops being in the rotation ahead of the soybeans. 

“In Wayne County there was an interaction in the very early planting (first week of April) with the cover crops. In the early planting with no cover crops, there was a lower than desired stand of about 80,000 plants per acre. In the early planting with a rye cover crop, the stand was even lower at around 20,000 plants per acre,” Lindsey said. “There was a negative interaction with the very early planting date and cover crop. When the soybeans were planted at a more normal planting date, the presence or absence of a cover crop had no influence on the stand. For the very early planting date, especially with the cover crop, we observed a reduction in stand, and also in the final yield by 20 to 30 bushels per acre.”

There are multiple possibilities as to why the negative interaction between the cover crop and soybean stand occurred in the very early planting. 

“Asking why the negative interaction occurred is a really good question, and one we want to do more research into,” Lindsey said. “When looking at the reduced stand with the very early planting date and cover crops present in Wayne County, there seemed to be more than one problem. There was slug damage, and some bean leaf beetle feeding. The cover crop seemed to keep the soil a little cooler and wetter and there were some diseases observed in the crop. There was also some frost damage where the cover crop seemed to trap some of the cold air compared to the bare soil. It did not seem to be just one thing, but multiple. It opens the door for more research to pinpoint what was happening in the interaction between the cover crops and early planting stand.”

Lindsey pointed out that the negative interaction was only observed at the very early planting date (end of March, first of April). There was not a negative interaction between the cover crops and soybean stand with the more normal planting dates. Research will continue into some aspects of this project.

As the calendar approached April in 2023, wet conditions throughout Ohio had prevented any extremely early planting efforts for soybeans or corn by OSU Extension researchers. The first early planting date corn and soybeans in the Extension research went into the ground last week. Temperature conditions at planting were considered adequate, with average soil temperatures at 2 inches of depth in the range of 52 to 57 degrees F while average air temperatures were in the range of 64 to 66 degrees F.

With cooler temperatures this week, the researchers will see what impact it may have on the early planted corn and soybeans last week. Cooler days will accumulate GDDs slower, leading to emergence at later calendar dates than expected.