As the rains continue into mid-June, so does the talk about nitrogen losses from crop fields. Nitrogen deficiency symptoms in corn plants can be a warning sign of yield limitations to come.
In a presentation at the Western Iowa No-Tillers Field Day near Shelby June 16, Pat Reeg, Iowa Soybean Association On-Farm Network technology manager, told attendees that nitrogen loss and nitrate content in water correlate more directly with rainfall amounts and frequency than with amount of nitrogen applied within a watershed region in any given year.
He says that if sidedressing is part of your normal nitrogen management program and very little of your nitrogen was applied before planting, chances are applying your normal rate of nitrogen fertilizer at sidedressing time will be sufficient for this year's corn crop. That's assuming, of course, that you can actually get into the fields to sidedress! "If you put on most of your nitrogen last fall, or were able to get it on preplant and then see yellowing in corn leaves, using the late spring soil nitrate test can indicate whether there's a need for an extra application of nitrogen," says Mick Lane, research communications manager for the On-Farm Network.
He explained a little about how to use the late spring soil nitrate test in last week's newsletter that is published online by the On-Farm Network. He offers are a few more notes on that topic:
* The critical concentration is 20 ppm in a wet spring.
* Collecting good cores of soil for testing can be a challenge in saturated soils.
* Because Iowa fields are variable, multiple samples should be collected in each field.
* Fields with N applied in a band such as anhydrous ammonia or injected swine manure are difficult to sample. The best way to sample fields that have received banded N is to collect three sets of 8 cores that are positioned at various distances between two corn rows.
* For help with interpreting results, see this On-Farm Network publication and also Iowa State University Extension Publication PM1714.
Other references are also available online to help you with current crop management decisions
If you still have soybeans to plant, see ISA's Soybean Planting Brief issued last week. This article lists several considerations and options for farmers facing planting delays, including a clarification of many of the crop insurance factors, soybean planting dates vs. group maturity selections, soybeans and nitrogen fertilizer, cover crops and the prevented planting option.
Last week, Lane also discussed the revisions to the online soybean fungicide calculator to account for spring rainfall. Since March through May rainfall has exceeded 12 inches in nearly all of the state of Iowa, growers will be much more likely to see a return on the investment with an R3 application on soybeans this year. "As we've been saying for the past few weeks, this unusual weather has given us the opportunity to gather data comparing late plantings of differing maturity corn hybrids and corn vs. switching to soybeans," says Lane. "We've had a few takers on the normal vs. early maturity corn replicated strip trials, but so far none on the soybeans vs. corn. If you've considered all the options and are at the point where you're about to make a switch, we'd encourage you to plant three combine (or sprayer) width strips of corn in the field you're now planting to beans in order to make a final economic comparison after harvest. See the protocol for this trial."
Now is the time to scout fields and check the growth stage of your crops
Finally, if you were able to get corn planted earlier, check the growth stage. Tristan Mueller, ISA On-Farm Network program manager, says it may be growing faster than you think, especially with the recent warm days. "If you signed up for On-Farm Network fungicide trials, many of the products need to go on between the V5 and V10 growth stages," Mueller says. He also notes that with the wet weather this spring, the chances of seeing a benefit from fungicide on corn are higher than normal. "We still have some products left for fungicide trials, and with much of the corn behind schedule, it's not too late to get involved," he says.
Fungicides still available for 2013 trials include: Priaxor, Custodia, Quilt Xcel + Halex GT, and ProAct + Propiconazol vs. Headline. In 2011 and 2012, both drier years, V5 applications of fungicides on corn averaged about 1 bushel per acre yield response. See Mueller's report from the 2013 On-Farm Network Conference for more on fungicide use and yield response. For information on any of the 2013 replicated strip trial opportunities discussed here, contact: Tristan Mueller email@example.com or 515- 669-9151; Anthony Martin firstname.lastname@example.org or 515-669-9157; or Patrick Reeg email@example.com or 515-669-9184.