May 14, 2012
As corn emerges, stands are being evaluated. So far I have not encountered nor heard of any stand that isn’t “a keeper.” Roger Elmore, ISU Extension Corn Specialist, recently wrote about possible causes for some of the observe issues, which can be found at http://www.extension.iastate.edu/CropNews/2012/0511elmore.htm.
The most recent corn population study results and a discussion of the re-planting decision-making process are at http://www.extension.iastate.edu/CropNews/2009/0514elmoreabendroth.htm and http://www.agronext.iastate.edu/corn/production/management/planting/replanting.html. In the articles, Roger Elmore mentions that numerous gaps of up to 4-6 feet can reduce yields by an additional 5-6%. For more information on the effect of gaps, see NCR 344 “Uneven Emergence in Corn” at http://www.extension.iastate.edu/Publications/NCR344.pdf. There is also useful information on non-uniform emergence at http://www.agronext.iastate.edu/corn/production/management/early/height.html. Remember that the cost of re-planting and yield loss from late planting needs to be compared to any yield loss from stand losses to make a good decision.
The unusual weather this spring has made it harder to predict when cutworms will start becoming an issue because some early moth flights may have been missed and the frost in April may or may not have taken care of some of the early cutworms. Some cutting has already been reported along and south of I-80. Cutworms are a sporadic problem and not likely to be an issue in most fields, but fields should be scouted until they reach the V5 growth stage so they can be treated if needed. A general rule of thumb is to treat if you find 2-3% of the plants cut and the worms are less than ¾ inch long. However, higher corn prices may alter that rule. An Excel decision-aid and more information are at http://www.extension.iastate.edu/CropNews/2012/0425sissonjessehodgson.htm.
Even though optimum seeding rates have been increasing every year for corn, recommended seeding rates for soybeans have been going in the other direction. Recent work by Palle Pedersen has shown that the optimum final stand for soybeans is 100,000 plants per acre. Optimum seeding rates will vary depending on the seeding method used and germination of the seed, but it will seldom pay to seed at higher than 125,000-140,000 seeds per acre. Because of soybean’s ability to compensate for lower stands by branching out and producing more pods per plant and more seeds per pod, yields do not decrease much until populations get below 75,000 plants per acre. See Palle’s fact sheet “Optimum Plant Population in Iowa” at http://extension.agron.iastate.edu/soybean/documents/OptimumPlantPop.pdf for more information.
CORN AND SOYBEAN SEEDLING DISEASES
I’ve heard of a few fields, both corn and soybean, where seedling diseases are present. Alison Robertson, ISU Plant Pathologist, is looking for some samples from such fields. She will collect 50 seedlings from the field and take them back to Ames for laboratory analysis. If you have such a field and would be willing to give up 50 diseased plants from the field, please let me know and I will relay the specifics of the field to Alison.
FOR YOUR CALENDAR
SOUTHEAST IOWA RESEARCH and DEMONSTRATION FARM, Crawfordsville
SPRING FIELD DAY and 25th Anniversary Celebration (afternoon) &
SPECIAL SESSION FOR CCAs (morning)
JUNE 21, 2012
Details are posted at http://www.extension.iastate.edu/Pages/eccrops/meetserc.html.
NORTHEAST IOWA RESEARCH and DEMONSTRATION FARM, Nashua
SPRING FIELD DAY
JUNE 28, 2012, 1 – 4:30 p.m.
Details are posted at http://www.extension.iastate.edu/Pages/eccrops/meetnerf.html.
TECHNIQUES and TECHNOLOGIES TO AVOID SPRAY DRIFT
July 17, 2012, Field Extension Education Laboratory (FEEL) near Boone, IA
Two half-day sessions (morning session repeated in the afternoon) (no cost to participants) will be conducted, focusing on:
- Nozzle selection/use with demonstration on spray table
- Balancing efficacy and drift
- Environmental factors, adjuvants and limitations, field demonstration, etc.
More information and registration will soon be available at http://www.aep.iastate.edu/.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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