Sunday, June 16, 2013

Water Hemp and Nitrogen Loss from Rain are Biggest Challenges to Corn Crops in Southwest Missouri

Contact: Jill Scheidt, agronomy specialist
Tel: (417) 682-3579

LAMAR, Mo. –Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County, scouted area fields on June 19 to prepare this week’s field scouting report.

Scheidt says wheat is in the soft dough stage and diseases are present, but it is too late to spray for them.

“It usually takes 4 weeks after flowering for wheat to be ready to harvest. On average, Wheat is running 14 days behind,” said Scheidt.

Scheidt did report seeing lots of water hemp in corn fields this week. It is important to kill water hemp at a very early stage, when it is 2” tall or less, to insure good control. Many water hemp plants are Roundup resistant and hard to control because they grow 1-1/2” per day.

“If water hemp is identified in your field, it needs to be sprayed immediately. You can identify water hemp from other pigweeds by the hairless leaves,” said Scheidt.

Dicamba products work well in corn, Cobra works well in soybeans and if water hemp is not resistant to Roundup, use a minimum of 32 oz. /ac. Roundup WeatherMax or PowerMax. Search for IPM 1030 for more information on controlling water hemp.

Corn is leaning due to wind and excess rain in the soil, but should stand back up.

“The excess rain received in southwest Missouri has reduced the amount of nitrogen available to the corn crop,” said Scheidt.

According to Peter Scharf, MU fertility specialist, producers are likely to need to apply more nitrogen if corn that is at least 1 foot tall remains lighter green than it should be once the soil is no longer waterlogged. You can also track rainfall and probable nitrogen loss by going the Nitrogen Watch webpage at

“According to the maps, producers in Barton and surrounding counties should be aware of potential nitrogen loss in poor drained soils and those in well to moderately drained soils have probably experienced substantial nitrogen loss if nitrogen was applied pre-plant,” said Scheidt.


The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension. For more information on this scouting report, or to learn how to receive it a week earlier by telephone, contact the MU Extension Center in Barton County, (417) 682-3579.

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