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The challenges of a cool spring

By Staff | Apr 27, 2018



Producers who have already had to deal with delayed planting are facing additional challenges in the forms of cover crops and getting spring nitrogen applied.

The good news, according to experts, is that there is still plenty of time to get the corn crop planted in order to maximize its yield potential.

Cover crops

Angie Rieck-Hinz, Iowa State University Extension field agronomist, said terminating cover crops could be tricky this year due to the cooler weather.

“We really want to make sure we don’t skimp on our burn down this year,” she said. “It’s going to be hard enough to kill them as it is.”

Rieck-Hinz suggests, when it comes to applying glyphosate to terminate covers crops, to do so on a warmer, sunny day with temperatures above 60 degrees and a night time temperature dropping no lower than 40 degrees.

“That plant has to be actively growing. That is when we get our best activity with our herbicide,” she said. “We have to get it translocated through the whole plant, to all of the growing points or else it is not effective. If the plant is not growing, it is not moving the herbicide to get the whole plant killed.”

Some cover crops are just now beginning to grow due to the cooler spring temperatures.

Typically, Rieck-Hinz said cover crops should be terminated two weeks before planting corn.

“We also have to think about crop insurance considerations,” she said. “Some crop insurance requirements require terminating so many days before planting for corn, or so many days of planting beans, either before or after.”

Timeliness of cover crop termination can also help ward off any potential seedling diseases.

“We want to look at any allelopathic affects cover crops can have on corn germination,” she said. “We have some research out of Alison Robertson’s plant pathology lab and her work, and we see some of these cover crops can actually host or increase soil bacteria or soil fungi, so we want to make sure we have terminated that cover crop so there is a bridge between terminating the cover crop and planting corn. We want to make sure we are not leading to increase incidences of disease.”

Rieck-Hinz suspects, because of the way the year is going, some producers may plant some corn prior to terminating their cover crops.

“I don’t want to tell people to do that, but I think some are going to be thinking about that,” she said. “This year is going to be tough. We’ve been cool and we’ve been wet and we want our soils as good as they can be. Our seed coats on our corn and our soybeans are much better at protecting seed this day and age than they have been prior, and I think that helps a lot, but I think we really want to minimize an increased chance of disease pressure.”

Although spring has brought a lot of challenges with cover crops, Rieck-Hinz said to not give up on them.

“We had a fairly late fall last year, and we do have some places with some nice-looking cover crops and the benefits we get from them, and even the benefit we get from the cover crops that’s not in the lush stages we are used to seeing the last couple of springs, is still there,” she said. “We reduce erosion, we’re still holding soil in place, we’re still actively taking up nutrients and holding them in place. Probably not to the point we have seen the last couple of years – at least in terms of nutrient cycling because we haven’t had a lot of growth – but it doesn’t mean they are still not contributing to nutrient uptake and that they’re still not actively helping us to reduce erosion.”

And there is still significant time to go before cover crops have to be terminated for a soybean crop.

“Some aren’t going to terminate cover crops until they’re ready to plant beans and it’s possible there is two to three more weeks and we can get some nice growth in that time,” she said.

Another potential issue with cover crops this season could be insects

“Since growth and subsequent termination have been delayed, I would also encourage farmers to scout fields where cover crops have been planted for insects such as True Armyworm and Black Cutworm as corn emerges. The moths of those insects are attracted to green, grassy cover for egg-laying,” she said.

Spring-applied nitrogen

Rieck-Hinz said it isn’t too late to get your nutrients applied.

“When soil conditions are fit, because we are still within that adequate time frame to plant corn, we have not lost any yield potential yet, I would put my nitrogen on, then plant corn,” she said. “If we would continue to get delays in planting, then we might want to flip-flop that around. We always say in north central Iowa, our 98 to 100 percent yield potentials are somewhere between April 12 and April 30.”

“Even then, that yield potential can sometimes and often, in late springs like this, may extend all of the way through the first week of May. We have plenty of time to maximize corn yield potential.”

Rieck-Hinz advises if a producer decides to switch from anhydrous ammonia to another nitrogen product – such as 28 percent or a 32 percent solution or a granulated urea – to be sure to check with their supplier to ensure they have the product.

Planting conditions reminder

“First of all, we want warm conditions,” Rieck-Hinz said. “We want soil temperatures at 50 degrees and going up, but we also want to make sure soil conditions aren’t too wet.”

What is a good way to tell if your soils are ready for planting?

“My advice is to go out to each field, because they will all be different,” she said. “Check those fields, and check them multiple times throughout the day because conditions change. Grab a handful of soil, squish it into a ball, toss it up in the air. If you catch it and it’s still in the ball form and doesn’t crumble, it is too wet.”

Planting in too wet of soils can cause compaction and sidewall smearing. The roots will only be able to grow in that trench, ultimately leading up to limited root growth.

“We really want soil conditions good so we get good seed to soil contact,” she said.

Once those soil temperatures are at 50 degrees and rising, keep track of those numbers, as well as the forecast.

“I encourage people to keep an eye on soil temperatures,” Rieck-Hinz said. “And if we are supposed to get one of those cold rains and soil temperatures are going to drop – and especially if they are not that warm to begin with – I would delay planting until after that cold, wet rain.”

If a cold snap is forecast, Rieck-Hinz advises waiting 48 hours before planting.

“If we’re going to drop soil temperatures and especially if we get a cold rain with it,” she said. “Because, when that seed first embodies water, we don’t want it to be overly chilly and don’t want additional chilling that can effect germination and emergence. So if the soil temperatures look like it is going to drop, then I would back off on planting for at least 48 hours and see what happens.”

There has been some discussion of producers switching to soybeans before planting their corn.

“We want those soil temperatures a little bit warmer,” she said. “We have plenty of time, and we have more time to plant soybeans than we do corn to maximize yields at this point.”

With a long delay in planting, should producers be looking at switching hybrids?

“It’s way too early for that conversation,” she said. “We wouldn’t normally tell people to switch from a full season maturity until we get closer to the end of May. We have some time on that.”

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