Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


July 20, 2005

July 20, 2005





Scott and Clinton Counties are now considered to be in a severe drought and the other counties I cover are considered to be in a moderate drought.  In general, the farther east you go, the more serious the drought is.  The hot and dry weather has taken it's toll, with the corn crop is especially deteriorating in many places; hopefully the showers that went through this morning are a prelude to more rainfall.  In these same locales, hay is short and pastures are drying up, posing challenges for dairy and beef producers.  Most soybeans still have the potential to produce an excellent crop.

Iowa State University has created a Drought Information page on the World Wide Web at  There are currently many resources there, and more will be added.  I would encourage you to use this resource for drought-related questions.






The days immediately leading up to tasselling through the first few days after pollination are critical to the corn plant.  This is the time when the plant is making the final determination of how many kernels it "thinks" it can carry to maturity.  The more stressed it is during that time, the shorter will be the ear it will try to keep.  Some fields have been showing much more stress than others, depending on location, soils, history, management, genetics, insect injury, etc.  The fields showing little stress still have excellent yield potential while the most severely stressed fields will be most valuable as silage.


Green Chop and Silage


Some corn fields are now being harvested as green chop or silage.  Be sure to check the WWW link above for details; is especially noteworthy.  A few key points to remember when green chopping or making silage are:

1.  Be sure silage is at the correct moisture content for the storage method you have.  The visual queues you usually use may not be accurate with drought-damaged corn.

2.  Nitrates are seldom a problem.  If they are, it is when the drought-damaged corn silage is harvested within a few days after a significant rainfall.  The plant may take in a "big gulp" through the root system and not have the ability to move it into the kernel.

A.  If nitrate accumulation does occur, it will be in the bottom 12 - 18 inches, so cutting high will help.

B.  Many forage testing laboratories can test for nitrate in forage.

C.  After 2 - 3 weeks of fermentation in the ensiling process, the nitrate level dissipates greatly.  If you are still concerned, have the fermented product tested for nitrate.

D.  Cattle and sheep can tolerate 0.5% nitrate on a dry matter basis.

E.  Cattle and sheep can tolerate higher levels if feeding occurs over a period of several hours.

F.  Nitrate tolerance is increased if grain is fed.

G.  Gradually introduce cattle to suspect forages over a period of several days.





Unless the plants have gone into permanent wilt, there is still excellent yield potential if temperatures moderate and we start receiving adequate and timely rainfall.  August weather will be critical for this crop.




Two Spotted Spidermites (technically not insects) are increasingly being found in soybean fields.  I have received a few reports of fields with soybean aphids above the threshold.  Be sure to continue to monitor for these pests and manage appropriately.  With the drought stress, the crop is less able than normal to tolerate injury from these pests.  See the previous update or on management issues.




Well established hay fields are generally not growing rapidly but are still green.  If the plants are otherwise healthy, there is currently no need to worry about long-term effects of the dry weather on the stand.


Potato Leafhopper


Continue to monitor for and manage potato leafhoppers.  With the drought stress, the crop is less able than normal to tolerate injury from these pests.  See the previous update or on management issues.


If you have any questions, please feel free to contact the Iowa State University Extension Office.
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Last Update: July 20, 2005
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