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6/29/2009 - 7/5/2009

Foliar Fertilization of Corn and Soybean

By John Sawyer, Department of Agronomy


Corn
Research has been conducted on foliar fertilization of corn over the years, but not overly extensive in Iowa. One reason has been the lack of positive results when studies were conducted. Looking at data from the early 1970s to recent years I don’t find cases where foliar fertilization produced positive yield responses. An example is a study we conducted in 1999 with foliar application of low-biuret urea and mono-potassium phosphate at four growth stages from V6 to VT. There was no yield response with urea application, but a statistically significant yield decrease of 5 to 6 bu/acre with mono-potassium phosphate application. Results of recent university trials that I’ve seen with foliar fertilization have not indicated positive response. I have also on occasion received input from producers about corn growth problems related to foliar fertilizer applications.

A new twist has been promotion of “rate substitution” for nitrogen (N), where a pound of foliar applied N product can substitute for more than 1 lb N/acre soil applied. Greater efficiency with a foliar nutrient application might be a theoretical advantage, however, research with various products has not shown this to occur. The main difficulty with applying N, phosphorus (P), or potassium (K) via a foliar application is the large nutrient requirement by corn (for example, 200 lb N/acre or more total above ground uptake depending upon production level), which cannot be met with a foliar-applied rate. Foliar rates must be low to avoid tissue damage and, therefore, to increase yield significantly repeated applications would be needed but this would be too costly. To meet the large crop demand for nutrients like P and K, the suggested method is soil testing and soil application when a need is indicated.

Soybean
Both early and late season foliar fertilization have been researched extensively in Iowa. A nice summarization of that research can be found in a previous Integrated Crop Management article written by Antonio Mallarino (Foliar fertilization of soybean: is it useful to supplement primary fertilization?). The short summary of that article is that late-season foliar application has not improved yield, with yield losses documented at rates that caused leaf damage. Early season application sometimes improved yield, but across many trials and various products the yield increase occurred at only about 15 percent of fields and the average yield response across all fields was less than 1 bu/acre. Therefore, early season foliar fertilization is not a recommended practice across all fields. Unfortunately no specific crop or field condition clearly indicated when an early season foliar application would be beneficial. Although soil testing indicated a higher probability of response in low-testing than in high-testing soils, tissue analysis for P or K concentrations at the V5 to R3 growth stages was not a reliable diagnostic tool. Frequency of response was greater in some cases, such as with no-tillage or ridge-tillage systems, and when early plant growth and/or P or K uptake were limited (which can be difficult to identify in early soybean growth). The most consistent yield responses, when they occurred, were with a rate of 3 gal/acre rate of 3-18-18.

What about iron chlorosis in soybean? High soil pH soil conditions, along with free lime – calcareous soils of the north central region of Iowa (the central lobe) can result in low iron availability to soybean and development of iron chlorosis. The most commonly suggested, and best but not always successful way to deal with iron chlorosis is variety selection. Foliar iron application can be beneficial due to the low amount of iron required by soybean, but typically applications must be made at initial development of the symptoms, multiple applications are often needed, and the yield increase is usually not as good as with use of varietal resistance. Iron chlorosis development, and iron availability in the soil and within the plant is quite complex, which makes successful management with foliar fertilization difficult.

iron chlorosis

Iron chlorosis symptom - soybean. Photo © John E. Sawyer

 

What about manganese-glyphosate interactions in soybean, and response to foliar manganese? In areas of the Midwest where manganese deficiency develops in soybean (specific soil conditions in states like Indiana and Ohio), foliar manganese application has been practiced for many years. Use of gylphosate has not reduced that symptom development or need for foliar manganese application, and perhaps has increased it. Because soils can quickly tie up soil applied manganese, the preferred treatment has been foliar application when deficiency symptoms develop. In Iowa we see iron chlorosis in soybean, but not manganese deficiency. Research in areas that do not have manganese deficiency issues has shown the use of glyphosate does not necessitate the need for foliar manganese application nor influenced the development of manganese deficiency. That is, manganese application has not necessarily increased yield when glyphosate has been part of the weed control system. This is an area that could probably use additional research.

Summary
Just because a post herbicide application is being made to a field does not justify inclusion of a foliar fertilizer material. Remember, corn and soybean take up a large amount of N, P and K, during a growing season. This amount cannot be substituted for or compensated with a low foliar rate. If you are still not certain about foliar fertilization or the benefits of promoted products/systems, then try a few well controlled/replicated strips and monitor crop growth and yield before making applications to large acreage.


 

John Sawyer is professor with research and extension responsibilities in soil fertility and nutrient management. Sawyer can be reached at jsawyer@iastate.edu or by calling (515) 294-7078.

Degree Days - More Heat and Humidity with Bigger Weeds

By Rich Pope, Department of Plant Pathology

Summer burst through the doors with a blast of heat and humidity. Although oppressive to people, it allowed for rapid growth of both crops and weeds.  Weeds are a considerable concern in most areas, most notably where pre-plant burn downs were skipped, and where spraying has been prevented by wet fields. Most areas of Iowa gained 20 to 25 degree days more than the average mid-June week.  

Mapped degree day accumulations by crop reporting district

Soybean aphid populations have now been reported in northeast, north central, northwest and central Iowa.  A cooler, potentially more aphid-favorable weather forecast for the coming week, increases the need to monitor soybeans for aphid populations.

 

Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted by email at ropope@iastate.edu or by calling (515)294-5899.

June 29 Iowa Crop & Weather Report

By Doug Cooper, Extension Communications

Listen to Doug Cooper, Extension communications specialist, as he interviews Iowa State University Extension climatologist Elwynn Taylor, integrated pest management specialist Rich Pope, and sybean agronomist Palle Pedersen.

During the weekly interview, Taylor says hot humid temperatures should be behind us for a few weeks with a return to cooler and drier weather.

Pope talks about this year’s pesky weed - volunteer corn – and how it is presenting a problem for many corn and soybean producers.

Pedersen continues the conversation about weeds and volunteer corn in soybean fields. Many field are unsightly because rainy conditions have made the weeds difficult to control.
28:39
http://129.186.89.193/radio/audio/ETWX2609.mp3

Is It Japanese Beetle in the Field or Something Else

By Erin Hodgson, Department of Entomology

A few reports of metallic adult beetles have been coming my way this week. I thought it might be too early to see adult Japanese beetles in Iowa. But literally as I am writing this article, a Japanese beetle flies into my office through an open window - guess that answers my question! Some of you may have questions regarding identification of scarab beetles, or beetles in the insect family Scarabaeidae.

In general, adult scarab beetles are stout insects with a hardened body and clubbed antennae. Adults eat a variety of foods, including fungi, dung, carrion, sap, pollen and foliage. Rarely do the adults cause economic damage to field crops, but they can occasionally cause aesthetic damage to ornamental plants and fruit trees. The larvae are called grubs that feed underground or under debris. Larvae are pale yellow, gray or creamy in color, and are always c-shaped. Larvae can cause significant plant damage, particularly to grasses, as they feed on the root system.

japanese beetle larvae

Grubs are creamy white with a brown head capsule.1

 

There are several scarab beetles in Iowa, and probably the most important species is the Japanese beetle. The larvae are difficult to distinguish, but careful examination of the raster (aka, the butt) hairs will provide diagnostic details. The adults are more easily identified based on size and color (see Table 1).

Japanese beetle life cycle.
There is one generation per year, with adults emerging from the soil in June. Mated females lay eggs in the soil until late August. Adults have an exceptionally wide host range (more than 300 plants) and skeletonize leaves. Hatched larvae feed on the roots until temperatures begin to cool in the fall; larvae move deep into the soil to overwinter. Nearly fully grown larvae resume feeding in the spring, pupate within the soil and emerge as adults.

 

japanese beetle damage

Japanese beetle causes leaves to be bronzed and lacy. Adults often mass on plants.1

 

 

japanese beetle life cycle

The annual cycle of Japanese beetle is like other scarab beetles in Iowa. 2


 

Table 1. Japanese beetle and other commonly mistaken scarab beetles in Iowa.beetle chart


Photo credits
1. David Cappaert, Michigan State University (
www.ipmimages.org)
2. M. F. Potter, D. A. Potter, and L. H. Townsend, University of Kentucky (
http://www.ca.uky.edu/entomology/entfacts/ef451.asp)
3. Marlin E. Rice (
/CropNews)
4. Jerry A. Payne, USDA-ARS (
www.ipmimages.org)
5. Steven Katovich, USDA Forest Service (
www.ipmimages.org)
6. K. V. Makarov (
http://www.zin.ru/animalia/coleoptera/eng/aphgrakm.htm)
7. Peter J. Bryant (
http://bugguide.net/node/view/272167/bgimage)

 

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at ewh@iastate.edu or phone (515) 294-2847.

FEEL Clinic Offers Basics of Crop Plant Diagnostics

By Brent Pringnitz, Department of Agronomy

The Field Extension Education Laboratory (FEEL) near Ames is offering a new program on July 13-14, the 2009 Field Diagnostic Clinic. This FEEL program focuses on the fundamentals of crop plant diagnostics.

For someone new to field diagnostics this clinic will provide fundamental training to conduct accurate diagnosis of crop and pest problems. The program will also challenge experienced agronomists to identify new pests and crop problems, and refresh skills needed on a daily basis to provide sound agronomic advice.

alison robertson at FEEL

Program sessions focus on insect, weed and crop disease identification, herbicide injury, nutrient deficiency symptoms, and understanding crop growth and development. Sessions will be taught by ISU Extension faculty from the departments of agronomy, entomology and plant pathology. Each small group session includes intensive, hands-on training in FEEL demonstration plots to enhance instructor-student interaction. The program also includes an evening barbecue with the instructors and a presentation by Elwynn Taylor, ISU Extension climatologist.

The Field Diagnostic Clinic is approved for Certified Crop Adviser CEUs: 5.5 crop management, 6.0 pest management and 1.5 nutrient management.

Registration is required for this program and space is limited. Registration is $250 and includes all meals, breaks and course references. To register for this program, or for more details on the course, visit the FEEL website. For program questions please contact the Agribusiness Education Program at (515) 432-9548 or aep@iastate.edu.

The Field Extension Education Laboratory (FEEL) is a 43-acre teaching and demonstration facility that has been training crop production professionals since 1987. FEEL is coordinated by the Agribusiness Education Program, a joint effort of the departments of Agronomy, Entomology, Plant Pathology and Agricultural and Biosystems Engineering with support from the College of Agriculture and Life Sciences and Iowa State University Extension. For a full listing of educational programs available, visit www.aep.iastate.edu.

 

Brent Pringnitz is coordinator othe Agribusiness Education Program. He can be reached at (515) 432-9548 or by emailing bpring@iastate.edu .

Crop Management Clinic Features Over 20 Topics

By Brent Pringnitz, Department of Agronomy

Registration is now underway for the 2009 Crop Management Clinic to be held July 15-16 at the Field Extension Education Laboratory (FEEL) near Ames. The Crop Management Clinic is an intensive two-day training program that focuses on the latest developments in crop production and protection. Attendees can select from over 20 different topics to develop a course agenda that fits their specific interests and needs.

ISU Extension specialists will be discussing the impacts of common crop problems, how to avoid them and methods to improve productivity. The curriculum is divided into four primary areas: crop management, pest management, nutrient management and soil, water and tillage. A detailed listing of scheduled topics is available at the clinic Web page.

FEEL elmore

Sessions will be taught by ISU Extension faculty from the departments of agronomy, entomology, plant pathology and agricultural and biosystems engineering. The sessions are conducted in small group settings to enhance instructor-student interaction and include hands-on training in FEEL demonstration plots.

The Crop Management Clinic is approved for up to 12 Certified Crop Adviser CEUs. Credits in each CEU category are dependent on sessions selected by the student.

Registration is required for this program and space is limited. Registration is $250 and includes lunches, breaks and course references. To register for this program, or for more details on the course, visit the FEEL website.  For program questions please contact the Agribusiness Education Program at (515) 432-9548 or aep@iastate.edu.

The Field Extension Education Laboratory (FEEL) is a 43-acre teaching and demonstration facility that has been training crop production professionals since 1987. FEEL is coordinated by the Agribusiness Education Program, a joint effort of the departments of agronomy, entomology, plant pathology and agricultural and biosystems engineering with support from the College of Agriculture and Life Sciences and ISU Extension. For a full listing of educational programs available, visit www.aep.iastate.edu.

 

Brent Pringnitz is coordinator of the Agribusiness Education Program. He can be reached at (515) 432-9548 or by emailing bpring@iastate.edu.



This article was published originally on 7/6/2009 The information contained within the article may or may not be up to date depending on when you are accessing the information.


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