Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


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May,  16, 2008




Emergency Forage Crops

One option to try to meet some of the forage needs is to consider planting an emergency forage crop. Nearly all of the emergency forage crops are rapidly growing annual crops. Sudangrass, sorghum-sudan hybrids, pearl millet, and Japanese millet are multiple-cut, warm-season annuals, which can be used for fresh cut forage, pasture or silage, but are difficult to dry for hay. Forage sorghum is a tall, one-cut, warm-season annual that is used for fresh cut forage or stored as silage. Prussic acid is a risk for sorghum and sudangrass, so must be managed appropriately. One of the better hay options is foxtail millet which produces one summer growth, although yields are lower than with multiple-cut forages. A relatively new to Iowa forage is Teff, which is an African warm-season annual grass that has grown reasonably well in some Midwest U.S. locations. It establishes relatively quickly and has multiple growth cycles through the summer season, but seed sources are limited.  Some cool season crops, such as annual ryegrass, spring small grains, and forage brassicas, can also be planted in the summer to help fill forage needs. For more information see Steve Barnhart’s article in last year’s ICM Newsletter at




Hybrid Maturities


There is a lot of corn yet to be planted and some are thinking of switching to an earlier maturing hybrid. Unless you were trying to stretch the season by planting a hybrid 5 days longer than what is common in the area, it’s too early to be switching away from the full season hybrids. If there is still corn to be planted during the last week of May, switching to a hybrid about 5 days earlier in maturity would be something to consider.


Corn Stands

I haven’t seen any corn emerged yet and I’m a little afraid of what we will see when the fields start to emerge with all of the fields that were planted under marginal conditions. Re-planting poor stands may be something that growers will be debating about soon. The following table can help in making replant decisions:

Influence of planting date and plant population on corn grain yields

------------------ Corn Yields (% of maximum) -----------------
Stand     April 20 -     May 13 -     May 26 -     June 10 -     June 24 -
X 1,000   May 5          May 19       June 1       June 16       June 28

28–32    100                 99                    90           68                  52
   24        94                  93                    85           64                  49
   20        81                  80                    73           55                  42
   16        74                  73                    67           50                  38
   12        68                  67                    61           46                  35

Numerous gaps of up to 4-6 feet can reduce yields by an additional 5-6%.

The table is based on trials done from 1997-2000 in three locations in Iowa.  Optimum corn stands have increased by at least 2,000 plants per acre since this work was done, so actual corn yields obtained will likely be somewhat lower than what is indicated in the table. One encouraging point is that very little yield penalty was seen with mid-May planting dates. Corn yield potentials did not drop dramatically until planting was delayed into June.

For more information, see Pm-1885 “Corn Planting Guide,” which is also available a and NCR 344 “Uneven Emergence in Corn”  at




            Many fields are looking a little weedy out there. Tilling the field when it is still wet will likely just transplant the weeds from one spot to another, as well as make a poor seedbed. If using 2, 4-D with Roundup to try to get a better kill on some of the larger weeds, remember the one week planting delay for both soybean and corn.

            Some may have planned applications of soil applied herbicides that get delayed due to the rain. Many soil-applied herbicides can be applied after the corn has emerged, but may not have an effect on emerged weeds. Radius (& Balance Pro) should not be applied after corn emergence or severe injury may occur. Obviously Roundup should not be applied after corn emergence on non Roundup-Ready varieties. Mike Owen has an article on herbicide options after corn emergence in the ICM News at









            Certified Crop Advisors can obtain 5 hours of credit (including 2 hours of soil and water) by attending a special session in the morning followed by the afternoon tour at the ISU SE Iowa Research & Demonstration Farm near Crawfordsville on June 26. This will include a tour in the morning featuring the soil drainage research on the farm.  More details will be posted soon.



If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: May 16, 2008
Contact: Jim Fawcett

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