Weeds rob nitrogen from corn

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

An MSU timing study on post emergent weed control showed that 95 percent of weed control or better can be achieved when weeds are 9 inches tall, but yields were reduced 25 bushels per acre. (Everman et al., 2008)

Post-emergent herbicides provide a greater window of opportunity to control weeds, but allowing weeds to grow too long can be “robbing” N and other nutrients from the intended crop.

In a two-year study in Wisconsin, there was no yield loss when weeds were controlled at the 4-inch stage, but delaying application on 12-inch weeds resulted in an average 9 percent yield loss. Looking at the data from another view point, 2006 data showed the MRTN rate was 96 lbs per acre when weeds were controlled at 4 inches, compared with an MRTN rate of 200 lbs per acre when weeds were controlled at 12 inches.  Timely weed control will ensure valuable nutrients are used for crop production rather than weed production. (Boerboom et al., 2008.)

Boerboom, C.M., T.L. Trower, C.A.M.  Laboski and T.W.Andraski.  2008.  Fertilizing weeds for a profit?  Proc. Of the 2008 WI Fert., Aglime and Pest Mgt. Conf.  47:223-226.

Everman, W.J., A.J. Chomas, and J.J. Kells. 2008. Residual and non-residual herbicide application timing effects on weed control and yield. Proc. North Central Weed Sci. Soc. In press.

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