Spend Wisely Now to Avoid Late-Season Troubles
Much of the heavy lifting is already done regarding 2015 inputs. Still, you aren’t out of the woods yet. Some decisions remain. Here’s a look at three input decisions you may have to make later this year.
1. In-Season Nitrogen Applications
Springs are wetter than they used to be. That’s boosted the payoff for in-season and late-season N applications.
Peter Scharf, University of Missouri (MU) Extension soil specialist, says 80,000 central U.S. acres, on average, received 16 inches of April-to-June rainfall from 1900 to 1980. That’s now grown to around 200,000 acres annually.
“When you have more than 16 inches of rain from April through June, you run a high risk of N deficiency,” says Scharf.
No one knows exactly where these acres will occur from year to year. In 2011, many northeastern South Dakota farmers battled prolific precipitation during this time frame. Ditto for northeast Iowa and southeastern Minnesota in 2013.
Odds are that if you farm in the central U.S., your time is coming – if it hasn’t already.
“You’d better have a plan in place for those types of years,” says Scharf.
One way to beat the odds is to spread out N applications later in the growing season. That reduces exposure to rainy periods.
This strategy worked well in a 2008 MU central Missouri trial. A sidedress application of 110 pounds of N per acre on knee-high corn beat a 180-pound-per-acre at-planting N application by 44 bushels per acre, says Scharf.
Similar results occurred in a 2009 MU trial with the same N rates and timing treatments. Ditto for 2010, when the same sidedressed treatment outyielded a preemergence N treatment by 80 bushels per acre.
Little difference resulted in the two timings and applications during drier years in 2011 and 2012. In 2013, though, the same pattern surfaced again.
When all years from 2007 through 2014 were tallied, sensor-based sidedressing treatments beat preplant treatments by 254 bushels per acre with 164 pounds per acre less N in the MU tests.
Late-season N applications aren’t just limited to knee-high corn. Successful rescue treatments can occur even as late as tasseling.
“Some people think it is good money after bad,” says Scharf. That’s true in some cases. Overall, though, good yield responses have resulted to late-season N applications in MU trials.
In 2010, for example, a 57-bushel-per-acre response occurred to N applied to corn under high N stress at tasseling.
“The worse it looks, the more it can respond,” Scharf points out.
2. Late-Season Waterhemp
Yes, it can be uncomfortable wading through standing crop to wrangle late-season waterhemp escapes.
Even more uncomfortable, though, can be a postseason talk with a testy landlord who wants to know why you let a weed go to seed at the rate of at least 250,000 seeds per plant.
“The key is to control those weeds before they go to seed,” says Ryan Rector, Roundup technology development manager for Monsanto.
Waterhemp is a late-season stalker that can foil even the most foolproof of cultural and chemical control programs. In corn, the good news is that its canopy is a tough deterrent for weeds to dent. Still, scouting is needed to assess waterhemp status, says Ryan Lins, Syngenta research and development scientist.
“See if survivors are large enough to come through the canopy,” he advises. “If they survived a previous glyphosate treatment, they likely are glyphosate-resistant. Those survivors can produce seed that are resistant to glyphosate.”
Drop-nozzle application with a nonresistant postemergence herbicide is one way to control a cornfield run amok with underlying waterhemp.
Unfortunately, soybeans do not have as formidable of a canopy. Waterhemp also can emerge in drowned-out spots or on prevented-planted acres that are difficult to enter with a sprayer.
Treating these areas with a backpack sprayer is an option, although you’d likely be spraying weeds at a height taller than herbicide label recommendations.
“You can’t expect 100% control,” says Lins. “Some growers may go into field edges or drowned-out or prevented planting areas with a mower before weeds go to seed. In-crop hand rouging is also an option.”
3. Soybean Aphids
The month of August used to be a time when soybean farmers could take a break before the busy harvesttime season. Soybean aphids put a stop to that practice when they first invaded the Corn Belt in 2000.
Soybean aphids don’t occur each year. Still, it behooves you to scout for this late-season pest, particularly under the mild and dry conditions in which aphids thrive.
A 2005 to 2007 land-grant university study in six locations in Minnesota, Iowa, and Michigan that compared four soybean-aphid management systems showed an integrated pest management approach worked the best.
This strategy consisted of field scouting followed by a foliar insecticide application if a 250-aphid-per-plant economic threshold was reached. This threshold hinges on this level being reached by at least 80% of plants.
There is a point, though, when an insecticide treatment will not pay.
“Even if you have aphid populations increasing, you will not see any benefit if you go past the R5 (beginning seed) stage,” says Erin Hodgson, Iowa State University Extension entomologist.