Volume 2, Issue 4
April 19, 2019
This newsletter is an update on current topics and events in agriculture in Boone, Dallas, Jasper, Madison, Marshall, Polk, Story, Tama, and Warren counties.

Meaghan Anderson
Extension Field Agronomist

ISU Extension & Outreach
220 H Avenue
Nevada, Iowa 50201
Office:  515.382.6551
Cell:     319.331.0058

Upcoming Events

IDALS Apr 19 - Dec 19 Pesticide Testing Schedule

May 16 - Field Scouting Basics Workshop, Boone

Handy Links

Central Iowa Crop Update
Updates from an agronomist and weed nerd in central Iowa.

In this issue:

  • Soil temperatures, rainfall, air temp
  • Corn - planting date and yield, nitrogen
  • Check alfalfa stands for winter injury
  • Pasture nitrogen management
  • Seedling diseases and low germ
  • Online paraquat and dicamba training
  • Resources for pesticide applicators using respirators
  • Check FieldWatch before pesticide applications

Soil temperatures, rainfall, air temp

Soil temperatures warmed quickly in early April before falling back down again with rainfall and cooler temperatures; the NPKnowledge website linked above provides an estimate of average daily soil temperature across the state for the last three days. We always aim for 50 F (4 inch depth) and a favorable warming forecast before starting corn planting, however, even if the soil temperatures aren't 50 F, if the forecast is favorable for warming and the soils are fit otherwise, the general consensus is to go.

While it doesn't probably feel like it, we've had a fairly dry and slightly warmer than normal last 30 days. The forecast looks fantastic for fieldwork in the next week, so hopefully we can get a lot of work done and get timely rains where/when we need them.


Corn - planting date and yield, nitrogen, other notes

Corn planting, planting dates and yield
Corn planting will soon be the only thing on everyone's mind, but take care not to let the late start get the best of you. It's important to take time to properly adjust, monitor, and make readjustments to the planter to fit soil conditions and field to field variation. Corn crops are remarkably resilient, but sidewall smearing, compacted soils, shallow seeding depth (aim for 2" and I'd always rather risk being deeper than shallower), and other issues can haunt you the entire growing season. Check out this ICM News article on planter maintenance and adjustments for more information.

On average, maximum grain yields in Iowa occur between 34,500 and 37,000 plants per acre (ppa), although there is significant variation across locations and years.  On average, the best net returns occur with plant populations at harvest are between 30,000 and 35,000 ppa.  Not every seed that is planted develops into a plant, so we typically suggest increasing seeding rates by about 5% to account for losses from abnormal seedling development or seed that does not germinate. Check your seed tag for the specific percent live seed (PLS).
Corn planting date is typically a balance of crop insurance planting dates, time frame for the highest yield potential, and favorable soil conditions (temperature, moisture). ISU planting recommendations show that the highest yield potential is achieved when corn is planted between April 15 and May 9 (98-100% potential) in central Iowa and between April 17 and May 8 (98-100% potential) in southern Iowa. 

Nitrogen rates
Consider checking your N application rate against the Corn N Rate Calculator. This calculator uses data from replicated nitrogen rate trials all across the state over multiple years to determine the MRTN rate range. The MRTN is the point of maximum return to nitrogen or where the economic net return to N is maximized, and the calculator provides a range of N rates that are within $1 +/- of the maximized net return to N.

Anhydrous ammonia application
I posted some notes about anhydrous ammonia application in my last newsletter, but there have been several accidents and a lot of application happening recently, so I thought I would repost notes on what happens with NH3 in the soil, safety with NH3, and some general application tips
  • Many people use a 7 day rule between NH3 application and planting corn, but if NH3 is placed deep in the soil and sealed well, there is no specific waiting period before planting. Ammonia moves more in coarse, dry, or cloddy soils, as well as in wet soils that smear.
  • In order to minimize potential contact between germinating corn seeds and NH3, use GPS to plant rows either offset (perhaps 6-10 inches) from straight NH3 rows or plant at an angle from the NH3 rows (apply NH3 at angle, plant straight) rather than directly above NH3 knife rows.
  • Safety with NH3 is key - both in transport and use in the field - and only so much of this is within our control. Read up on NH3 safety and application tips for in the field in this new article and here in an older one.

Check alfalfa stands

I've received some phone calls and heard from colleagues across the state regarding winter injury and winter killed alfalfa coming out of this winter. If you haven't already checked your forage stands, now is the time to do so! Stands that may have suffered the most would be older stands, those with a late harvest last fall, those with little stubble, and those with low lying areas that may have collected water.

This new article "Scouting and Managing for Winter Injury in Alfalfa" on the ICM News website can be helpful in determining what management might be necessary this spring.


Pasture nitrogen management

My colleague in NE Iowa, Brian Lang, wrote a nice article in his newsletter on pasture nitrogen management. It does a good job of discussing nitrogen from an agronomic production standpoint; consider when you need the forage and whether it will be utilized (as pasture or hay) in choosing rate and timing.

Grass-based pastures generally respond very efficiently to the first 40-50 pounds per acre of nitrogen (N). Bluegrass will continue to respond to N applications up to 150-180 lb./acre annually, but at a decreasing rate of response. Tall cool-season grasses (bromegrass, orchardgrass, tall fescue) respond to total season N levels up to 250-300 lb./acre, but at a decreasing rate of response. The lower end of the N recommendation ranges listed below for grass-based pastures are considered modest and efficient. Timing of N applications listed below are generally most efficient for Early spring > Late summer > Late spring. Thus some may consider not to apply any additional N in Late spring, especially if rainfall is below normal. The other critical factor is efficiency of use of the forage. Can the livestock fully utilize the increase in forage production with N fertilizer applications? Can a portion of excess pasture be fenced-off for a spring hay harvest? Is the pasture fenced for rotational grazing to better utilize the forage, and manage regrowth cycles?

 Kentucky Bluegrass 
  • Early spring (March and April) 60-80 lb./acre
  • Late spring (May to early June) 30-40 lb./acre
  • Late summer (August to September) 30-40 lb./acre
 Tall, Cool-season Grasses
  • Early spring (March and April) 80-120 lb./acre
  • Late spring (May to early June) additional 40-60 lb./acre
  • Late summer (August to September) additional 40-60 lb./acre
 Legume-Grass Mixed Pastures
  • If less than 1/3 legume, treat as a grass pasture
  • If more than 1/3 legume, no nitrogen is recommended
Note for legume-grass mixed pastures: high or frequent applications of N, particularly spring N applications, will make the grass component of pastures more competitive and limit the amount of legumes in the mixture. To encourage a greater legume presence, use modest N rates and limit application to summer or fall.

Seedling diseases and low germ

I wanted to share a nice ICM News article that was posted recently on seedling diseases in corn and soybean. You can read it here.

Online paraquat and dicamba training 

Farmers planning to use the new dicamba products approved for use in soybeans (XtendiMax, FeXapan, or Engenia) must maintain a pesticide applicator's license for the state of Iowa and must also attend a special dicamba training each year. You can still complete this training in an online format. Each company has an online training available and online training from one provider qualifies as training for all the dicamba-based products. Access the online training from Bayer (XtendiMax), BASF (Engenia), and Corteva (FeXapan) at the links on their names.

On March 8, 2019, the EPA announced that they have released a mandatory online training for applicators using (mixing, loading, applying, etc.) the product. Find more details on the training, when it is required, and where to get it at this link.

Resources for pesticide applicators using respirators

The Worker Protection Standard (WPS) requires that all pesticide handlers using products that require respirators:
  • receive a medical evaluation by a physician or other licensed healthcare professional;
  • complete a fit-test to determine if the respirator forms an appropriate seal around the face;
  • and, complete a training about the use, care, and maintenance of a respirator.
For more details about these requirements and how often you must complete each piece, check out this ICM Blog article on our website. Iowa's Center for Agricultural Safety and health (I-CASH) put together a list of medical providers across the state who conduct respirator medical evaluations and/or fit-testing. You can also reach out to local healthcare providers or contact me if you need help finding someone to provide fit-testing.

Check FieldWatch before you spray

FieldWatch is the new version of the Sensitive Crops Directory and the Apiary Registry for the Iowa and several other Midwest states. This easy-to-use website allows you to check for sensitive crops and apiaries near fields where you will be applying pesticides. As an applicator, you can register with the website to record your fields and receive updates when new sensitive crops or apiaries are added near them or you can access the maps to look for neighboring publicly registered areas for free without providing any of your own information.

Specialty crop producers with 1/2 acre or more of commercial specialty crop production and beekeepers are encouraged to register their locations on the website to alert neighboring applicators to these sensitive areas. The Iowa Department of Ag and Land Stewardship (IDALS) has more on the specifics of Iowa's Sensitive Crops Directory on their website.

For more information about FieldWatch, how to find it online or in their new app (FieldCheck), and other good information, check out this recent ICM News article "Check FieldWatch Before Pesticide Applications."


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