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5/27/2013 - 6/2/2013

Manure Management Concerns Caused By Recent Wet Weather

By Angela Rieck-Hinz, Department of Agronomy and Daniel Andersen, Department of Agricultural and Biosystems Engineering

The wet spring has raised many concerns about manure management for Iowa crop and livestock farmers.  The following is a quick list of issues and possible responses to the issues.  Farmers are encouraged to contact their local ISU Extension and Outreach ag engineer, field agronomist or livestock specialist, or the local DNR field office for additional information and assistance.

Delayed Planting
As we approach June, many areas of the state have experienced delays in corn planting due to wet soil conditions. Those fields that have had liquid manure applied at rates intended for growing corn can be switched to soybean on or after June 1 with no penalty of over-application of manure nitrogen. Chapter 65 of the Iowa Administrative Code reads [65.17(18)c]

Nitrogen-based application rates shall be based on the optimum crop yields as determined in 65.17(6) and crop nitrogen usage rate factor values in Table 4 at the end of this chapter or other credible sources. However, subject to the prohibition in 65.17(20), liquid manure applied to land that is currently planted to soybeans or to land where the current crop has been harvested and that will be planted to soybeans the next crop season shall not exceed 100 pounds of available nitrogen per acre. Further, the 100 pounds per acre application limitation in the previous sentence does not apply on or after June 1 of each year; in that event 65.17(6) and Table 4 would apply as provided in the first sentence of this paragraph.”

Producers should document the changes in the crop rotation, application methods and other changes in their annual manure management plan forms, prior to planting or changes in application method.

Application of Nitrogen 
Although in many areas of Iowa it will be days if not weeks before farmers can get back in the field to finish planting or to replant, for many of the planted fields a concern will be nitrogen loss.   Livestock producers with DNR manure management plans are reminded that if they have already applied the maximum nitrogen rate to the field, they can’t apply additional sources of nitrogen unless the need is confirmed by the use of the late spring nitrate test (LSNT). This test measures nitrate-N concentration at the 0-12 inch depth. Be sure to read the recent article on nitrogen issues by Jeremy Klatt, DNR, if you have a manure or nutrient management plan. 

Manure Storage
During wet water our primary management goal should be to keep concentrated manure contained. Open manure storages should be monitored closely to prevent these structures from over-topping. If manure levels in storage ponds or tanks approaches full capacity producers should make plans to remove manure from these structures. The over-topping of bermed earthen storage ponds and lagoons could result in breaching and loss of the structures. Although concrete and steel structures are not in danger of breach failures, they should also have level removed if they are in danger of overtopping.

Producers should transfer manure from full storage structures to alternative storages if available, as land application of manures during saturated conditions is likely to result in movement of manure nutrient and organic matter into surface waters. If no alternative manure storage is available producers should contact the Iowa
Department of Natural Resources to discuss emergency wet-weather land application before allowing a storage tank or pond to overflow. If manure levels reach one foot below the top of a concrete or steel structure, or within two feet of the top of an earthen bermed structures producers should contact their local Iowa DNR field office.

Contact Information for IDNR Field Offices

Field Office # 1 - Manchester (563) 927-2640
Field Office # 2 - Mason City (641) 424-4073
Field Office # 3 - Spencer (712) 262-4177
Field Office # 4 - Atlantic (712) 243-1934
Field Office # 5 - Des Moines (515) 725-0268
Field Office # 6 - Washington (319) 653-2135

Land application challenges
Wet soils intake manures and water at a slower rate, much of their capacity to hold liquids is already used, and they are prone to compaction and surface runoff. Moving manure to available storages is thus preferable, but if no alternative storage can be identified and emergency manure application must be performed, contact your Iowa Department of Natural Resources field office.

Tips to consider include:

  • Haul a few loads to lighter, well-drained soils that may support manure application equipment.
  • If using tankers consider filling them to less than full capacity to limit weight.
  • To minimize the risk of nutrient transport, avoid fields with a high risk of runoff or flooding, consider applying to the driest portions of fields, and reduce the manure application rate.
  • Apply to fields with flatter slopes and lower phosphorus index scores and try to apply at least 24 hours before substantial rainfall to help prevent runoff.
  • If this doesn’t follow your manure management plan, be sure to update the plan accordingly.

Develop and/or review your emergency application plan. Wet weather and muddy conditions increase the chances for something to go wrong and can slow response. Review the emergency response plan with employees. Emphasize who to contact, safety issues and what to do when emergencies occur. Potential issues to discuss include how to contain the spill, who to contact (both within the company and the appropriate agencies) and how to perform the clean-up and the necessary repairs. If possible a copy of these resources should be placed in the tractor.


Angela Rieck-Hinz is an Extension Program Specialist in the Department of Agronomy at Iowa State University. She can be contacted at 515-294-9590 or email  Daniel Andersen is an Assistant Professor in the Department of Agricultural and Biosystems Engineering.  He may be contacted at 515-294-4210 or email

Slugs Like the Wet Weather

By Erin Hodgson, Department of Entomology

Recently I have heard reports of slug damage to corn, soybean and sunflower. This particularly wet time in Iowa may be conducive to slugs. Although slugs aren't insects (legs or wings are absent and lack a segmented body), they often get lumped in with the bugs. Slugs have a head with a mouth, sensory tentacles and simple eyes. A simple foot produces mucus which aids in water conservation and movement. As slugs move, they leave a trail of mucus behind, sometimes referred to as a slime trail. Because they lack a hardened shell, slugs are able to move through small spaces and soil crevices. There are several slug species in North America, but the most common slug in Iowa crops is probably the gray field slug, Deroceras reticulatum (Fig. 1). 
gray slug
Figure  1. The mature gray field slug is 1 to 2 inches in length and pale cream to gray in color with mottled spots. Photo by Bruce Marlin, Wikipedia.

Life Cycle. Slugs usually have one generation per year and overwinter in the egg stage. The life cycle can extend to 15 months, there are often overlapping generations. Peak feeding activity occurs in the late spring and early summer. Slugs will become inactive during extreme cold and hot temperatures and can resume feeding after moderate conditions return (63-68 degrees F; more than 75 percent soil saturation). Slugs are hermaphroditic, (i.e., each slug is male and female), but mating pairs are needed to produce offspring.

Damage. Slugs are nocturnal feeders and their damage can go unnoticed. Slugs can attack seeds or seedlings and reduce stand, or they can defoliate established stands. Unlike insects with chewing mouthparts, slugs have a tooth-covered tongue, called a radula. The radula is used like a rasp to scrape food surfaces. If the slug is feeding on seeds, they will hollow out the center similar to wireworms. Field damage to germinating seeds and developing seedlings can be devastating. Brian Lang, extension field agronomist in northeast Iowa, has noticed slug feeding in emerging soybean fields (Fig. 2). 
slug damage
Figure 2. Recent slug damage in soybean showing a) cotyledon feeding and b) plant clipping. Photos by Brian Lang, Iowa State University

Slugs feeding on older plants will cause streaking or holes on the leaves. Slugs can be particularly devastating in no-till fields with moist surface residue; conventional or reduced tillage fields rarely have slug problems. Environmental factors that favor slug outbreaks include the following:

  1. No-tillage field crop production practices.
  2. Development of dense weed cover or the addition of organic matter such as manure.
  3. Mild winters may increase overwintering numbers, especially adult slugs.
  4. Prolonged periods of favorable temperatures combined with evenly distributed rainfall.
  5. Heavy and course soils, high pH, and excessive fertilization with nitrogen.
  6. Cool growing conditions that delay crop development, extending the period of crop susceptibility.

Scouting and Management. No-till corn and soybean fields should be evaluated in May and June for slug feeding. Because slugs feed at night, it can be difficult to estimate the density. Slime trails are often a first indicator of slug infestations. Instead, estimate the percent defoliation, knowing that vegetative corn and soybean can withstand 30 to 40 percent loss of older leaves. With the growing point intact, crops can outgrow slug feeding.

Planting date can be an effective cultural control tactic for slugs. Planting before eggs hatch will give plants a chance to establish and tolerate any feeding. Planting late may minimize slug feeding because of quicker germination and warmer/dryer soil conditions. If stand loss is significant, replanting sections or whole fields may be an option if the planting date is not too late.

Chemical control of slugs is difficult because of their biology and ability to “slime” off pesticides. The most effective products are caustic to slugs, like salt solutions or liquid fertilizers. Unfortunately, the concentrations needed to kill slugs are generally phytotoxic to the crops as well. Commercially formulated metaldehyde baits can be applied at 3.25-4 percent rates. (e.g., Deadline M-Ps). Slug baits are expensive, typically in the range of $10 to $15 per acre.

When applying baits for slug control, it is very important that the application be made when the slugs are at peak activity above the soil surface. Thus, bait application should only be applied during periods of ideal temperatures and wet conditions favorable to aboveground slug activity. Slug baits do not provide complete knockdown, but suppress populations until the plant can outgrow the damage (Fig. 3). In strictly no-till systems, growers must be able to tolerate slug feeding. A long term solution for persistent slug infestations should include occasional use of tillage and residue removal. 
gray garden slug
Figure 3. Slug baits will only suppress populations. Photo by Joseph Berger,


Portions of this article were based on The Ohio State University fact sheet (link to:

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities; contact at or phone 515-294-2847.

New Iowa State University Grad is FEEL Program Coordinator

By Daren Mueller, Department of Plant Pathology and Microbiology

Stuart McCulloh became the program coordinator at the Field Extension Education Laboratory (FEEL) on May 13, a few days after receiving a bachelor’s degree in agricultural communications from Iowa State University. The Camanche native grew up on a row crop and livestock farm and used his vegetable production enterprise to support his Iowa State studies. McCulloh focused on economics and studied a variety of agricultural topics to develop and hone his interest in agricultural entrepreneurship.

As FEEL program coordinator, he will work with extension faculty and researchers who have demonstration plots and conduct educational programs at the research facility. He will also coordinate educational opportunities for agri-business clients.

“I’m anxious to meet the people with projects at FEEL and establish a network with them,” said McCulloh. “It will be important for me to know the right people for the right job, so I can promote the farm and connect people with research on issues important to them – whether they are farmers, extension staff, students or agri-business professionals.”

In addition to addressing the training and demonstration needs of traditional FEEL audiences, he is interested in being more entrepreneurial in his efforts – not content with just doing things as they have always been done, but exploring new opportunities.
“Being a very recent college student, I see where FEEL has a lot to offer 300- and 400-level students, especially those learning about agronomics,” McCulloh said. “It is great place for students, as well as those working full-time in agriculture production, to learn from faculty research.”

McCulloh plans to apply his communication skills, general agriculture knowledge and inquisitive nature as he coordinates this summer’s scheduled events and directs FEEL staff finalizing plot establishment. He can be reached at or (515) 432-9548.


Upcoming events at FEEL

  • Early Disease Clinic − June 6; Focus is on diseases relevant to this year's growing season in both corn and soybeans; looking at diseases already present and those to scout and watch out for.
  • Field Diagnostic Clinic − July 9–10; A two-day clinic where attendees learn about crop growth and development of corn, soybeans and alfalfa, including herbicide injury and weed, insect and crop disease identification.
  • Crop Management Training – July 15–16; A two-day clinic covering over 20 topics with regard to crop management troubleshooting, and highlighting some research developments industry- and university-wide.
  • Late Disease Clinic August 21–22; Looking at early season disease relevant to the growth of both corn and soybeans and their effect on the plants, as well as current disease issues.

Daren Mueller is an assistant professor in the Department of Plant Pathology and Microbiology. He can be reached at 515-460-8000 or e-mail

Delayed Planting, Prevented Planting and Replanting Crop Insurance Coverage

By Steve Johnson, ISU Extension, and William Edwards, Department of Economics

The frequent rains that have soaked Iowa this year have left many corn and soybean fields unplanted or with flooded areas.  Many producers are wondering what options they have under their multiple peril crop insurance (MPCI) policies.

In Iowa, the crop insurance “late planting period” for corn begins on June 1. Corn can still be planted after this date, but the insurance guarantee on those acres is reduced by 1 percent per day until the acres are planted. Corn acres planted after June 25 will receive insurance coverage equal to 60 percent of their original guarantee. Producers should keep accurate records of planting dates on all remaining acres. The late planting period for soybeans is from June 16 through July 10 in Iowa.



Beginning June 1, corn producers with unplanted acres have three choices: plant corn as soon as possible with a reduced guarantee, shift to soybeans with full insurance coverage, or apply for prevented planting. Prevented planting acres are insured at 60 percent of their original guarantee and must have a cover crop established on them.

Acres that have been planted, but need to be replanted, may qualify for a special replanting insurance payment. Payments are based on the value of 8 bushels of corn or 3 bushels of soybeans per acre, times their respective projected insurance prices. In 2013, that is about $45 per acre for corn and $38 per acre for soybeans.  To qualify for an indemnity payment under the replanted or prevented planting provisions, a minimum area of 20 acres or 20 percent of the insured unit, whichever is smaller, must be affected.


ISU Extension Resources

More details can be found in the publication “Delayed and Prevented Planting Provisions” (file A1-57) on the Iowa State University Extension and Outreach  Ag Decision Maker website. An electronic decision spreadsheet is also available to help analyze alternative actions. Producers should communicate with their crop insurance agent before making decisions about replanting or abandoning acres.


Steve Johnson is an extension farm management specialist. He can be reached at 515-957-5790 or e-mail William Edwards is an economics professor with extension responsibilities in farm business management. Edwards can be contacted at 515-294-6161 or e-mail

Effect of Foliar Fungicides on Corn Yields in Iowa in 2012

By Alison Robertson and John Shriver, Department of Plant Pathology and Microbiology

Every year we evaluate foliar fungicides on corn at several locations across Iowa for disease management and yield response. In 2012, we tested foliar fungicides at six Iowa State University Research and Demonstration Farms: southwest (Lewis), southeast (Crawfordsville), north (Kanawha), northwest (Sutherland), northeast (Nashua) and the agronomy farm (Ames). Fungicides were applied at either growth stage V5, R1, R2 or both V5 and R1. Table 1 lists the fungicide products and treatments evaluated at each location.

Table 1. Fungicide treatments evaluated at six locations in Iowa in 2012.


The 2012 growing season was characterized by extremely hot and dry conditions. Very low foliar disease occurred in all trials and consequently disease severity was not assessed. A windstorm caused severe lodging at the northern and northeastern research farms. Standability and ear rot severity (percent ear with mold) were assessed within 48 hours of harvest at each location. Standability was assessed as the percent of plants lodged in a section of row in the middle of the plot. Ear rot severity was negligible to low (southwest research farm).  There were no effects (P<0.1) of fungicide on standability or ear rot.

The mean yield response of corn to a fungicide application across all locations was 5.7 bu/A and 54 percent of the treatments yielded more than 4 bu/acre compared to the untreated control, although no statistical differences in yield between the untreated control and a fungicide application were detected (P<0.1) for any treatment at any location. Fungicide responses varied widely among and within locations. Mean yield response for each treatment timing at each location is shown in Table 2.

Table 2.  Mean yield response of corn to a foliar fungicide application applied at either V5, R1, R2 or both V5 and R1 at six locations in Iowa in 2012.


In general, fungicides resulted in more of a positive effect on yield at the northern locations than the southern locations.  The mean yield response of an application of fungicide at V5 (4.9 bu/A) was lower than that of an application during the reproductive growth stages (5.5 and 6.2 bu/A for R1 and R2 applications, respectively).  A double application of fungicide at V5 and R1 resulted in a similar yield response across all locations to one application at growth stage R2 (both 6.2 bu/A).


We would like to acknowledge Bayer CropScience and Valent for partial funding for these trials.  Furthermore, we are grateful to the staff at all of the ISU Research and Demonstration Farms for managing and harvesting the trials.


Alison Robertson is an associate professor in the plant pathology and microbiology department with extension and research responsibilities; contact her at or phone 515-294-6708. John Shriver is a research associate in plant pathology and micorbiology. He can be reached at 515-294-3639 or

This article was published originally on 6/3/2013 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.