Northwest Iowa Crop Update Newsletter by Todd Vagts ISU Extension Crops Specialist Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.
[Home][Special Topics][Field Problems][Weather Data][Subsoil H20][PDF Info] [ISU Extension][IA State University]

Volume 2, Number 8

Northwest IA Crop Update, May 13, 2002
(Word Document)

In this issue 
Soil Temperature Cools (again)
DD50 accumulation and Corn Emergence
Corn stand and yield potential
Rotary Hoe
Farm Bill

Introduction
We had a good week for planting through most of last week.  I believe most of the corn is in the ground and many producers got a good start on soybean planting.  Most of west-central IA received from 1.0 to 2.5 inches of rain on Saturday.  For the most part, this will be beneficial to re-wet the seedbed.  Yet we may need to be cautious of soil crusting and seedling disease inhibiting corn emergence.  Emergence of the corn crop has been relatively slow across most of IA and west-central Iowa is no exception.  Figure 1 tells a story of greatly fluctuating soil temperatures and unfortunately soil temperatures have been on the decline the last 7 days.  Cool and wet soils may increase the likelihood of seedling disease and rot problems over the next several days.  This means we need to be out in the fields inspecting the seed in the ground and evaluating stands that have emerged.  Use Table 1 on page 2 to evaluate your potential corn yield based on the present stand and planting date.

Weather update
Moderately heavy rain was widespread across Iowa and Illinois on Saturday and Sunday.  Much of Iowa received at least 1.0 inche of rain and many areas received greater than 2.0 inches.  The 7-day extended forecast calls for chance of rain from Wednesday through Friday with day-time high temperatures reaching into the low 70’s.  We need warm sunny days to warm the soil and promote seedling emergence.

Growing Degree Day Accumulation
 The area accumulated 53 DD50’s over the last 7 days which is a few more than the previous week but less than was anticipated.  According to the 7-day forecast, we should expect 65 DD50’s over then next 7 days.  Emergence of corn should have occurred on fields planted from April 15th – 23^rd and be looking for corn planted through May 5 to be emerging this week (Figure 2).  According to DD50 accumulation, the earliest planted corn should be at the two to three full leaf stage (count the first leaf with the rounded tip).  With the cold soils the area has experienced, germination and emergence could be a problem in some fields, particularly in reduced and no-till fields with lots of surface residue.  Soil temperatures can be 5 degrees colder in fields with heavy residue compared to fields with little to no residue on the surface.

In Figure 2, the line with squares equates to Monona, Crawford, Carroll and southern Ida, Sac and Calhoun counties.  The line with Diamonds equates to Pocahontas, Buena Vista and northern Ida, Sac, and Calhoun counties.  The dotted line is predicted GDD and crop development in 7 days.

Corn Emergence Problems?
The cool, wet and crusted soils may result in many fields with marginal plant stands. Evaluating a stand to determine if replanting is necessary is a combination of science, economics and art. Research at Iowa State University comparing final plant stands at different planting dates (Table 1) should be used to help to make the decision on whether to leave a corn stand or replant it.

An excellent worksheet to use to make economic comparisons of leaving the original stand vs. replanting can be printed from the website
http://www.agcom.purdue.edu/AgCom/Pubs/AY/AY-264.html

Break up that soil crust with a Rotary Hoe - Joel DeJong, Extension Crop Specialist in far NW IA, wrote some good comments on the rotary Hoe.  He suggests that if you happen to be in an area with heavy rain or hail this spring, then crusting could be a problem as the planted corn tries to emerge - if conditions get hot, dry and windy.  A rotary hoe can help break up the crust.  Rotary hoes do a better job breaking up the crust if hoeing occurs before it gets really dry and hard.  Start hoeing when a little moisture remains in the soil near the surface - before that crust bakes hard.  Similar rules apply for soybeans - but remember that you should not hoe beans when they are close to emerging and have a "bent neck."  Damage from the hoe can severely decrease soybean stands at this time!

Pest Management
Black Cutworm Trap Catch; Go to the following web page to see local BCW trap catch numbers http://extension.iastate.edu/carroll/crops/bcw_2002_trap_catch.htm

Farm Bill Information
President Bush signed the farm bill Monday morning.  For more information and background on the farm bill visit www.agriculture.house.gov/farmbill.htm  The U.S. House Committee on Agriculture web site     http://agriculture.house.gov  has additional information on this and other subjects.

(Word Document)