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Crop stages variable across the state

By Staff | Jun 8, 2018



Weather seems to have started cooperating for producers that have seen a struggle this spring.

However, where some crops are progressing at a fast pace, some producers are dealing with acres that may either see a switch from corn to soybeans or may face not being planted at all.

Mark Licht, assistant professor and Iowa State University Extension cropping systems specialist, said in the central and southern Iowa crop reporting districts, corn is nearing the eighth leaf stage and soybeans have two to four trifoliates out.

“The crop is relatively uniform from field to field,” said Licht. “However, in the northern crop reporting districts, the crop growth staging is a lot more variable due to wet conditions prohibiting timely planting. Some fields are yet to be planted while others are further developed.”

There is one thing that all producers have in common across the state: higher temperatures.

“Higher temperatures in May meant anything that got planted is growing and developing faster than normal,” he said. “This has implications for herbicide applications being compressed into a shorter number of days before crops exceed stage or height restrictions on herbicide labels. It also means that we can expect corn pollination of timely-planted corn to occur in early July compared to mid-July. And for some of the early planted soybeans, flowering may occur earlier than we would expect.”

He encouraged producers get out and scout their fields.

“There have been reports of wireworms, white grubs, armyworms, and black cutworms,” Licht said. “Overall these are good to note but have not been causing excessive stand losses. Now is the time to start scouting for corn rootworm feeding on roots.”

Preventive planting

Delayed planting impact and next step meetings were held last week in various locations in northwest Iowa.

Crop insurance and Farm Service Agency (FSA) officials gave an overview of options producers have if they choose to change their intended acres to a different crop or make the decision to abort their planting missions and choose preventative planting.

Although many decisions producers face will depend on those rules and regulations that surround their crop insurance plan and those of the FSA, they also need to think, agronomically, what the impact is on delayed planting.

Paul Kassel, Iowa State University Extension field agronomist, provided considerations providers need to take with the planting of both corn and soybeans this late in the growing season.

Late season corn

Kassel provided data that was collected at the Iowa State University Research Farm located near Kanawha.

“We intentionally plant at different dates for this very reason we are gathered here today,” he said. “We look at what does delayed planting do to corn yields and grain moisture; that type of thing.”

In 2015, researchers planted 95, 104 and 109 day corn on May 13 and again on June 5.

The effects of an early June corn planting date compared to a mid-May corn planting date were corn yields decreased about one bushel and acre a day or a total of a 25 bushel per acre yield loss.

The corn’s grain moisture increased by 4.8 points, which also increases the costs of dry down at harvest time.

“These findings are the reason why we, or Iowa State University, is going to say you change from planting corn to soybeans around June 5,” said Kassel. “From an agronomic standpoint, around June 5 is when you should really look hard to changing to a soybean crop.”

Part of the reason is the grain moisture levels at harvest time.

“What’s that mean to you?” he asked. “Well, that’s about $7 per acre, per point for that extra moisture.”

Soybean planting dates

Kassel shared, based on studies done at the Northwest Research Farm, near Calumet, producers can expect a 20 percent yield reduction with soybeans planted on June 10.

For those acres planted into soybeans June 15-20, he advises using an early group II variety then changing to a late group I variety from June 15 to July 1.


Before making the official switch from corn to soybeans, Kassel said to be sure to look at the preplant herbicides that were applied.

Crop injuries to soybeans could occur if they are being planted in soil that has had an application of Harness, Surpass, Keystone, low rates of atrazine, Lumax, Lexar, Acuron, SureStart/TripleFLEX, Resicore, Balance Flexx, Corvus and Prequel.

“Technically those herbicides such as Harness, Surpass, Keystone and low rates of atrazine are for corn applications, only they are not labeled for soybeans, so crop injury may occur,” said Kassel. “The good thing is, in those cases, they are fairly short lived, so if they have been out there for two to three weeks, and even if they’re not labeled for soybeans, you can still plant in to them.”

“But where it gets tougher is the Lumax, Acuron because they have a relatively high rate of Callisto,” he added. “SureStart, TripleFLEX, they have a herbicide in them called Stinger and soybeans are very sensitive to Stinger, so that’s why there is a higher risk for injury.”

He added herbicides such as Outlook, Dual II Magnum, generic Dual and the low rate of Verdict are labeled for both corn and soybeans so therefore won’t cause an issue.

Cover crops

Kassel said if a producer chooses to surrender the growing season and put their acres into preventive planting, he encourages planting a cover crop.

“You’re not required if you do preventive planting to plant a cover crop, but we encourage you to do that,” he said. “On a soil conservation standpoint and from a soil quality standpoint.”

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