Introduction

We appear to be in for a warm week and excellent planting conditions.  I would expect corn planting to be well underway by mid-week throughout central and southern Iowa.  The calendar indicates that we are beginning at the earliest suggested time and have plenty of time ahead of us.  Be mindful to slow down and pay attention to detail and safety.  Soil temperatures continue to rise and have moved into the corn planting range.  Keep the corn planting speed down and pay close attention to maintaining uniform planting depth.  With the warm moist soil, several weeds will have or will be germinating, including ragweed, lambsquarters smartweed, sunflower, woolly cupgrass, velvetleaf and giant foxtail.  Consider disease package options in corn and soybean seed when planting into problem fields.  Use soybean fungicide seed treatments if a history of disease has been a problem in particular fields. 

Weather update
It appears that we may be in store for another interesting year in terms of weather conditions.  Forecasted highs for the next several days will be well above normal with continued warmth through the 7-day forecast.  Sub-freezing nightly lows are forecasted for the mornings of the 19^th and 20^th.    The 14-day forecast suggests a return to normal to slightly below normal temperatures with normal chances of precipitations.  Remember, the average last frost for west-central IA is May 1 and the average day with temperatures at or below 28 F is April 18.  Most of the area had a very nice rain last week, ranging from ½ to 1.0 inches.  This was a perfect rain to incorporate herbicides, warm the soil and to moisten the upper (seed depth) soil profile. 

Planting and Crop Development
Soil temperature continues to rise dramatically as we enjoy the warm sunny days.  Current soil temperatures are in the mid-50’s.  Corn germination starts at 50 F.  Although soil temperatures are warm now, a cold front could pass through dramatically lowering soil temperatures and stressing planted crops.   Obtain the most recent soil temperatures at ISU’s NPKnowlege webpage http://extension.agron.iastate.edu/NPKnowledge/

Corn Plant Population and Spacing As we prepare to plant corn this season, keep in mind some interesting points presented in the following article by Successful Farming’s Larry Reichenberger:

 ·         Yield responses to narrow row corn have varied by region with the northwestern Corn Belt, including Minnesota and the Dakotas, and the Northeast with Michigan and Wisconsin, being the only areas with a significant increase.
·         Emerson Nafsiger, from the University of Illinois, outlined trends in corn seeding rates. "The percentage of farmers planting more than 30,000 seeds per acre is increasing rapidly.”There is less than a 5% chance of yield decline when planting rates are raised from 30,000 to 36,000 seeds per acre. Being above your optimum population is less risky than being below it," he says. 
·         Peter Thomison, of Ohio State University, reported that uneven emergence by corn plants were far more damaging to yield than uneven spacing in the row. "One major cause of uneven emergence is earlier planting.
(Corn planting trends, By Larry Reichenberger, Crops and Machinery Editor, Successful Farming)

Pest Management
Weeds – Researchers at Michigan State University summarized data on the effect of time of tillage (day or night) and weed emergence.  Research concluded that:

• Tillage at any time (day or night) will increase emergence of annual grasses, large-seeded broadleaf and small-seeded broadleaf weeds. Therefore, if the goal is to maximize weed emergence prior to planting or an herbicide application, it is best to till during the day.

• Tilling at night in complete darkness will decrease emergence of small-seeded broadleaf weeds but will not decrease emergence of annual grasses and velvetleaf, cocklebur, or giant ragweed. Therefore, if the goal is to minimize total weed emergence it is best to till at night.

For more information, visit the following web site http://www.msue.msu.edu/ipm/CAT02_fld/FC3-21-02.htm

Disease – There are new races of Phytophthora present in Soybean fields that are able to cause disease on varieties with many of the Rps genes (Rps 1a, 1b, 1c, 1k, 3a and 6) Choosing Varieties with high levels of partial resistance is very important (P. Lipps, A. Dorrance and D. Mills; Soybean Seed Quality and Seed Treatment) and if you have experienced significant Phytophthora disease damage on Rps-1k gene soybean, consider using seed treatments containing metalaxyl or mefenoxam treatment for those fields.  For more information, visit the following web sites:  http://www.ag.ohio-state.edu/~corn/agcrops.html and http://www.ipm.iastate.edu/ipm/icm/2002/3-18-2002/soytreatments.html

Soybean Seed Treatments and Innoculants - (Loren J. Giesler, NE Extension Plant Pathologist)
What is the impact of soybean seed treatment fungicides on Rhizobium inoculants? The seed treatment fungicides with the highest toxicity level to Rhizobium inoculants are captan and thiram. Metalaxyl products have not been shown to have any adverse effects on inoculants. If a product with high toxicity is being used, in-furrow application of the inoculant is a good choice. Newer products are very considerate of this issue and fungicide companies are pursuing compatibility with inoculant producers. Most new products are inoculant friendly - some can even be mixed with inoculants as the treatment is applied to the seed. Always read and follow label directions to avoid a lethal combination for the inoculant being used. http://cropwatch.unl.edu/

Soybean Cyst Nematode and Tillage – Studies by USDA-ARS nematologist Gregory Noel suggest that farmers who practice no-till run little risk of increasing soybean SCN populations as long as a regular resistance management program is followed.  For more information on SCN management in Iowa, visit the SCN quick-info web page  http://www.extension.iastate.edu/Pages/plantpath/tylka/Quick/quickinfo.html

Soil Fertility
Key Points to Soil Sampling (Dr.’s Mallarino and Creswell, ISU Extension):

1. Use soil test information before applying fertilizer, lime or manure.
2. Soil test every 2 to 4 years, at the same time of year and following the same crop.
3. Prepare a sampling plan before going to the field.
4. Formulate nutrient applications after interpreting soil test results.

For more information on soil sampling and fertility, obtain the following publications from your local extension office or download them from the following web site http://www.extension.iastate.edu/pubs/.

• NCMR 348, Soil Sampling for Variable Rate Fertilizer and Lime Application ($1.25 per copy)

• NMEP 1, Soil Testing

• PM 1310, Interpretation of Soil Test Results

• PM 1688, General Guide for Crop Nutrient Recommendations in Iowa ($1.00 per copy)

Newsletters and Websites
Several excellent articles have written in the ISU IPM newsletter, check them out here: http://www.ipm.iastate.edu/ipm/icm/default.html

Subscribe to these newsletters for more agricultural information.

• Michigan State University Field Crop Advisory Team Alert Newsletters http://www.msue.msu.edu/ipm/fieldCAT.htm

• University of Illinois Pest Management and Crop Development Newsletter http://www.ag.uiuc.edu/cespubs/pest/welcome.html

Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue 
Carroll, IA 51401 
Office: 712-792-2364; Cell: 712-249-6025;  Fax: 712-792-2366
Email: vagts@iastate.edu  

For questions or comments please respond to vagts@iastate.edu

This page last updated on 02/03/04